oderja

I am going to try and drag race my Z06 this summer and could use some pointers on proper launching. All the C5's I have had in the past have been automatics, my 01 goes back off of lease in 2 weeks. My daughter and I had to do a little side by side race :D I launched about 4K and it spun until a shifted into 2nd and then some. She thought it really sounded nice and looked cool with smoke coming off the tires as I pull away :eek: !! I will be running it on both stock and drag radials so any suggestions would be appreciated!!

CP

J-Rod launches his Z just short of redline. :eek: Look in the Southwest section for him.

backtrail69

:eek:

PeterK

Hmm, what kind of tires does he have? I mean - I'm still in brake-in perioud - but 4K spin my tires.

Tracy

J-Rod slips the clutch, bigtime. Several months ago he wrote a very informative treatise on his progressive experiences at the track. He went quicker and quicker as he experimented with launch techniques. He attempted to explain his clutch slip technique in detail, but practice is the only way to really learn. I seem to recall that he goes from slip to fully engaged in like 10-15 feet.

Perhaps he'll chime in with a link to that excellent thread/discussion.

fpcopo

Mmmmm... JRod soon be putting in new pressure plate and disc!
:skep:

Power Shifter

Ranger

Not claiming my technique is the best one. But here's what I was doing on the F1SC tires. [Note: I only had 13 runs in my 02 on the stock tires before switching to the BFG drag radials.]

First off, select the best prepared and professionally run track in your area, even if it's a longer drive. Your times will be better; the racers will be more experienced; and someone will usually have a pocket weather station to give you the density altitude at the times of your runs.

Stage: Windows up. COMPETITIVE DRIVING mode. Radio off. AC off. I spin the stock F1SC tires for a second or two to clean them off. I run 23-25 lbs in the rear and 45-50 lbs up front. I shallow stage, just barely tripping the second set of bulbs. There is a school of thought that says heat up the F1SCs by doing a full burn-out. I have tried this and found that it does make for 60’ more consistently in the 1.8s than just the simple clean-off that yielded an average in the low-mid 1.9s.

Launch: I hold 1800-3200 rpm, depending on traction/track conditions, and quickly release (not pop) the clutch with full engagement occurring in the first 4'-10' of forward movement. I let the tires hook before going to WOT, and the progression to WOT is a squeezing of the accelerator…not a stomp. Goal is to not overpower traction and thereby make them break loose again. I can usually get to WOT leaving less than 10' of rubber. This takes practice that's best done away from the drag strip.

I adjust the launch rpm up or down in 200-300 increments depending on what happened in the earlier runs. On a well-prepped track, if the launch rpm is too low, the car will bog. If this happens raise the launch rpm.

Hope this helps. Good strong launches at the drag strip comes from practice, practice, practice.

Ranger

J-Rod

Again like others have said. Play with your car and find what works best for you. Here is what I have done... I hope you find some of this helpful.

Since the question comes up frequently in this forum, I thought I would post this. This is a compilation of my observations in running my car. From the first pass I ever made, up till I set my best pass to date of 11.933. If you have questions on what a Z is capable of, I hope that this will shed some light on what the car can do in anyone's (and I do mean anyone's) hands with a little bit of practice.

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As soon as I can get my clutch issue squared way, I hope to get into the 11.80s now that the weather is turning cooler.

In just about any conditions a Z06 can run in the lows 12s with no sweat. In my first trip to the track I went a 12.7.


My car was dyno'd with 1100 mile son it at MTI it dyno'd 358 corrected HP. I have made 4 dyno pulls on the car two pulls on two separate occasions. The highest corrected number was 359 and the lowest was 357. So, my car isn't some factory ringer. It makes the same number everyone elses does.

Anyway, here is a logbook of my passes in my car. From the first to the fastest... You can also go back and search for my posts, as they are all in this forum...


Here is a copy of my first post on the car.

------
First Pass
I took my '02 Z06 to Houston Raceway Park to put some initial baseline passes last night. I picked it up Saturday, and had put 1100 miles on the car and made the first oil change, so I felt now was the time to go make the first shakedown pass. Due to oil downs and an emergency page from work I was only able to make one pass. But I was impressed.

The Z06 to me did not feel as fast as the clock showed when I picked up my timeslip. I think this is because the power comes on very smoothly and across more of the band than other small block cars I have driven. After just playing around on the street I figured the car to be a 12.90/107-108 ride bone stock, just by the seat of the pants feel.

I had driven a 98 Z28 with 400 miles on it (back in 98) and it went 13.09/107 bone stock. I was impressed then by the way the LS1 revved. The Z06 felt faster, but I wasn't sure how much. I went conservative on the first pass and left at 1100-1200 rpm since I didn't know how the car was going to hook on the stock radials.

I was racing a 2000 6speed TransAm on gas. My car bogged coming out of the hole since I left so easy, and the TransAM totally killed me. He missed third gear, and I was able to make up some ground, and he ended up beating me by about 2 car lengths.

When I picked up my timeslip I was fairly amazed. While it is obvious that there is a lot of room for improvement, as evidenced by some of ya'lls times, I felt alot better about the purchase of the Z after this.

3/OCT/2001

60' ... 2.159
330 ... 5.610
1/8 ... 8.355
MPH ... 90.69
1000 ... 10.716
1/4 ... 12.716
MPH ... 111.41

Just in looking at the 60' times. I feel confident that I can get the car to a 1.8 - 1.9 60' time. Which would indicate to me that the car should go 12.20-12.30 bone stock. I am sure that there is some more time once I get a better feel for the shift points. The car seems to pull all the way to the rev limiter. I found last night playing around on the street that it was real easy to bump into the rev limiter.

All in all though, I am fairly pleased with what I have seen so far.


10-04-2001 09:54 PM

----------------------------

Here is my second trip to the track about a week later. It was hot outside, but I am also still getting a feel for the car.


----------------------------

Drag Racing part Deux
I was tempted to drive to SA and watch the Viper vs. Vette show, but instead decided to go to HRP and flog my '02 and do some much needed testing.

I managed to get in 5 passes in 2 hours. The car at this point is bone stock down to the stock paper air filter. I had intended to have a light load of fuel, but instead ended up having a full tank of gas.

My first pass was at around 7pm and the last was at 9:15. Temperatures ranged from 82 down to 78 and the humidity was high +90% (In short, the air sucked). I really was more concerend with working on my 60' times rather than quarter mile times, as I knew the car would probably drop off from the last time I ran it. I also intended to play with shift points, etc... and see what did and didn't work.

My first pass ever in the car a few weeks ago was leaving just off idle and resulted in a 2.15 60' time and a 12.77@111 the air was cooler and the humidity was lower, hence the higher trap speed.

Best pass last night was a 2.041 60' time 12.667@110

Most everyone I talked with complained about the air quality, and how slow their cars were running. I raced a supercharged 93 mustang who beat me by two car lengths. He went an 11.88 @114 and complained because his trap speeds are sometimes as high as 121. I think he was ready to burn his car. He pulled me over and asked what my time was. I think he was mad because our race was so close, and he didn't pull on me on the big end. The he spotted the badges on the side of the car and went "OH, so thats a Z06, not just a regular 'vette" then he didn't feel so bad and put the can of gasoline and the ligher away and went to go get back int he staging lanes. I was playing with shift points on that pass and only went a 12.95 @110. Since he only beat me by 2 car lengths, I can only imagine how he would have felt on the next pass when the car went a 12.667 which would have put me one length in front of him. (I hate seeing mustang owners cry....)

Anyhow, a couple of observations. I am still working on getting a feel for the clutch. Best results so far have been to leave around 2000 rpm, slip the clutch and roll into the throttle. I am easing into the clutch too fast at this point and bogging the car on the leave slightly. I feel if I can control the release better, I can drop the 60' times significantly.

Leaving between 2500 and 3000 on the stock radials tends to lead to too much wheelspin for me.

If you are going to run your car at the drags shut off Active handling completely. I had mine in Performance mode. While doing my burnout the car moved a little sideways and the active handling kicked in ( I guess it thought I was in a slide) and shut down my burnout.

I played with the shift points and this is what I was able to determine.

Hitting the rev limiter at all seems cost about .1 seconds in a pass. So if you hit the limiter at all figure it costs you about this much. If you hit it in both the 1-2 and the 2-3 figure .2

Short shifting the car is quite detrimental to quater mile times. I played with a couple of different shift points and found that it seems to run best if you stretch them out right to the limit, but not past.

Third gear seems to be the killer. The car really seems to pull best in this gear. On one pass I short shifted third gear to fourth at about 5000. The car dropped to 13.33@108. I tried 5500 and the car went a 12.95@110. So, my advice in this department is to watch the tach in 3rd gear. The car seems to hang a bit at the top of 3rd, but hold 3rd as long as you can it is woth some E.T. I went all the way to 6000 on the 3-4 and the car went a 12.667@110.

I ran these passes with minimal cooldown and in bad weather to see how it should fare on the street. It appears to me that currently the only real problem in the car so far is with its drivers inability to 60'. So, I think I am going to borrow at set of 16" E.T. Streets for the next go around and see what the car can do if traction is not an issue.

10-22-2001 07:38 PM

----------------------------------

Here is my third trip to the track with the car. It ook around 10 passes at the strip to get the lanches figured out.

----------------------------------

12.350 @ 114 - Bone stock
I went out to HRP Friday night and made 4 passes on the car. As per the advice of Ranger and some of the other folks I dropped the air pressure in the rears to 22.

My first pass was right off the street with no cooldown. 2.20 60' with a 12.88@111

I used the heater to bring down the motor temp (it goes right down to 190).

Next pass I brought the revs up more, and worked on slipping the clutch a little more. 1.97 60' 12.41 @ 112

Next pass I cooled the car again to 190 went up to around 2800-3000 and bogged it slightly coming out off the hole ( still working on the release) the car went a 1.92 60' 12.35 @ 114

Last pass I blew the release and ended up with a 12.88 @ 111

I was impressed however that there is 3-4 mph on the big end depending on the launch. I am interested to see how a lower 60' time helps the cars mph.

Anyhow, thanks to Ranger and everyone else who is posting hints here. My quest is to get it into the 11s with no mods. I may try it first on some drag radials, just to see if it can be done, and then work on doing it on the stock radials.

Anyhow, take care.


11-19-2001 06:09 PM

----------------------

Next I mounted up a set of ET Streets and took the car to the track in this case, the car finally went into the 11s. Using the ET streets helped me in learning what the cars limits were, and actually helped me do a LOT better on the radials.

-----------------------

11.960 @ 113.52 Bone Stock
Well, I went to HRP this evening on my new ET Streets. I made about 8 passes. There was about 6" of rain yesterday, so the track had been prepped right before rans began. I left at about 3500 and bogged the car and went a 12.22. I went to 4000 and the car bogged and went a 12.10. I was hot-lapping the car and my temps were in the 205 range. I continued to increase the launch rpms until I launched at 5200 rpm and came away with a 1.75 60' 11.96@113.52 I was warned by tech that one more 11 sec pass and I would be kicked out. I cooled the car to 190 degrees and went to launch the car at 5500 rpm. It resulted in a 1.69 60' time. But, I hit the rev limiter and blew the run. I came away with a 1.697 60' 11.98@112.54. Had I not blown the shifts I feel confident it would have been an 11.91 pass.

And as the title says, the car is bone stock no mods, no filter, no nothing. Just tires...

I will have a scan of the timeslips ready in the next day or so, and I will post them also.

12-15-2001 03:21 AM

--------------------------------

Next I decided to go out an work on the radials again. As you can see the ET Streets helped my skills on the stock radials.
--------------------------------

12.181@112.21 on Radials
Well, I had a chance to go out to HRP Sunday for some "instant green" racing.

My car was on Empty, so I debated on whether to go run on the ET streets and run a light fuel load, or whether to top it off for some ballast and run on the stock radials.

Since I had managed to run the 11.96 on the ET streets the last time out, I decided to go work on my radial tire skills.

I was late getting out there, and the track was packed. I was only able to get three passes in.

The first pass I launched the car at about 3000 Rpm and slipped the clutch. The clutch seemed to stick at about 3/4 of the way when I released it. It popped loose towards the top of 1st gear. I had not encountered this before in the Z. I hope this was a one time event, but I will be keeping an eye on this.

The launch RPM seemed to be low, and the car didn't move as hard as I wanted. Also, as usual on my first run, I banged the rev limiter twice. Usually my first run is a total blow off run , and then I get settled down and actually drive like I am supposed to. Instead of like a total goober. The timeslip reflected this.

60' - 1.947
330 -5.233
1/8 - 7.967
mph - 91.13
1000 - 10.298
1/4 - 12.280
mph - 112.35

I decided to weigh the car with a full ( and I mean completely FULL) load of fuel. The car weighed 3150 without me, and 3338 with me.

The next pass, I was in the lanes, and the guy in front wanted to race me. He was driving a mid 90's white Mustang LX. So, I said sure. He also said that he owned a WS6. He and his friends were nice, and we talked for a few minutes.

We staged the cars, he staged last and they dropped the light on us. He got me out of the hole by about a car length. I launced again at around 3000, since I didn't want to go up in smoke against a rustang.

The car launched about the same, maybe a little less. But, the car started to spin towards the end of of 1st and bumped the rev limiter. I had to chop throttle and shift It also wheelhopped a bit as it went into 2nd. By this point I was 1 to 1 1/2 car lengths behing the mustang. In 2nd nothing changed drastically. But when I stuck it in 3rd, the tables turned. I went from 1 length behind to 3 lengths in front. As most folks have noted the car really works in 3rd gear. I was happy that I beat him, but it was definitely not the best pass I ever made.

60' - 1.973
330 - 5.366
1/8 - 8.120
mph - 90.54
1000 - 10.463
1/4 - 12.445
mph - 114.32

The final pass was at the end of the night. I had hot lapped the car back around, and the temperature was around 205 degrees. I went to pull up, to do my burnout, and watched the car in fron of me leave. It was some silly kid in a 85 LX. He spun hard leaving and got completely sideways at the 330' mark and stopped inches from hitting the wall head on. He also took out the timing markers as he slid sideways. This idiot was spinning when he left and should have chopped throttle long before he got sideways. His car was drifting all over the place and probably ran all of a 15.1. They got on the radio after his little stunt and had someone go find him, and throw him out of the track.

Anyhow, they got the track cleaned off, and put in a new reflector, and I finally got to make my pass. They let me make my last pass by myself. I decide to try and raise the launch rpm, since I the night was over. I launched at about 4200. The car launched much better this time. I was able to keep my revs in the 5000 range all the way through 1st. The car didn't feel like it was spinning at all in 1st. The pass felt good all the way until I got to the 3-4 shift. I got greedy trying to stretch 3rd and bumped the limiter. I knew it cost me some time and mph.

Anyhow, I picked up my slip, and I was happy to see that the car had improved.

60' - 1.903
330 - 5.165
1/8 - 7.873
mph - 91.54
1000 - 10.200
1/4 - 12.181
mph - 112.21

Looks like the rev limiter was worth at least 2 mph and I would guess probably a tenth of a second. Anyhow, I am going to try and go next time and see if I can get those radial times into the magical 12.0 - 11.99 range.


Last edited by J-Rod on 01-29-2002 at 08:12 AM

01-28-2002 06:34 PM

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I went out the next weekend and made my fastest pass to date. 1.85 -60' / 11.933@114.52. I have since gone faster in the 60', but I am having clutch problems (not with it slipping, but with the pedal sticking to the floor). Until that is resolved, I probably will not be getting into the 11.80's. But anyway, my goal for the next few months is to get into the 11.80s or faster on the stock radials.

-------------------

11.933@114.52 Bone Stock on Radials
Well I went out to HRP this evening for a little instant green action. It was cold and windy tonight the weather shows 7mph, but, think it was closer to 10-15. The temperature was between 48 and 51 degrees when I got there and went down to 45 when I left.

Current Temp: 45 °F
Wind Chill: 41 °F
Wind: north at 7 mph
Humidity: 58%
Dewpoint: 31 °F
Barometer: 30.46 " and rising


The wind was blowing straight down the track, so you were running into a headwind.

My first pass was my usual blow off pass. I launched to hard and the car spun. 2.218 60' - 12.571@113.61

My next pass felt pretty good. Not great, but good. The car launched ok, I hit the rev limikter in 1st, but the rest of the pass was pretty solid. I got pulled over at the timing stand.

60' - 1.915
330 - 5.130
1/8 - 7.777
mph - 93.56
1000 - 10.055
1/4 - 11.992
mph - 114.73

Ok, I was given the warning and sent back to tech for the usual "Don't do that again". Ok, sure

I tried to cool the car down since there wasn't much of a crowd, and I could almost drive right up to the line. I decided that if the pass felt the least bit off, I would abort it, and see if I could get a "good" run in.

I made two more passes. One felt good, but the clutch stuck to the floor again and didn't come off until the car hit the rev limiter in 1st.

It was a 1.919 60' 12.324@93.61 on the brakes hard.

The next pass I had the car cool, and then something screwed up on the far end, so I had to sit there with both bulbs on and staged and let the car get hot, and the tires get cold. The car spun so I just coasted down the track.

I brought the car back around the coolant was at 194. The car launched pretty hard for radials, and bumped the rev limiter in 1st. The pass felt solid, so I stayed with it.

When I got to the timing stand I got the usual grief. I went through all the hooplah, and picked up my slip.

60' - 1.852
330 - 5.055
1/8 - 7.709
mph - 93.32
1000 - 9.992
1/4 - 11.933
mph - 114.53

So, I guess its time for a cage either that, or I get 1 or 2 passes per trip to the track.

Anyhow, I met another new Z06 owner Brutus0725 he just traded in his 2000 coupe for a 2002 z06. He was out there with paper tags and running some 12.3s. Which I thought was good for a new car with limited seat time. He was really cool, and I had a good time talking with him. Anyhow, I was pleased to see the car picking up still.

And as always, the car is 100% bone stock down to the paper air filter, and these passes were made on the stock radials.

02-11-2002 02:18 AM

------------------------------

Anyhow, I hope this helps anyone who want to race their stocker. I just wanted to point out, you probably aren't going to go to the track and in your first 3 passes turn an 11.9. Look at me, I sure didn't. It took some seat time and severla passes to get it all down. One thing I would suggest is to go out to the track early and try to get in as many passes as you can. We call this hot lapping. Don't worry about trying to run an 11.99. Just look at your slips. Make sure that every pass your times get better and better. Work on your launches, work on your shift points, etc... If you do 5 or 6 back to back passes you will be amazed at how your times start to drop. One of the things about doing this is doing them in rapid succesion help you get some "muscle memory" so this is more instinctive. One of the things about going to the strip is that many times it is over an hour between passes. By that time, the car may have cooled, but your body has forgotten what it did (right or wrong) on the last pass. Once you have a good technique down you can go to the track and get squared away in 1 or 2 passes.Consider it your crash course in drag racing 101. Doing that will conceivably save you 3 or 4 more trips to the track before you get your technique sorted out.

The only other advice I have is to drop the air pressure. I go with 22 in the rear and 50 in the front. Thats what works for me others have gone anywhere from 25 to 28. But dropping the pressure does work. So, play with that also.

The wheelspin I referred to in my 2nd trip to the track was early on. My experiences with ET Streets helped me get a feel for what
the car would do, and what I needed to be doing with the clutch.

As for the 60' times. The higher I rev it, the lower the 60' times.
My best 60' have been leaving at 4700-5500. Yes, this could be characterized by saying it is probably not condusive to long clutch life. Leaving at 3200-3500 typically gets me in the 1.9s.

For instance the other night, I left at 4700 and cut a 1.75 60'. The only problem as I stated was the clutch stayed glued most of the way down. When I went to pull 2nd I didn't have enough pedal to disengage the clutch. I missed the shift, had to lift off the throttle, and then pull it into second. That pass was a 12.2@114... So I feel pretty confident it would have been a VERY good pass otherwise.

At this point my car was still 100% stock. I went 114.52 through the stock airfilter,etc... with the restrictive (although somewhat better) 2002 cover in place. My mph showed about a 1-2 mph improvement by pulling the cover off and leaving the just the frame around the filter, but simply wire tied into place. On the dyno this was measured at 15 RWHP/11 lbft/TQ.

With the cover removed an ET Streets on the car continued to pick up ET and MPH. The best time to date in the car has been an 1.675 60' / 11.596 @ 118.52. Since you were asking about stack radials, etc... I didn't post that information. But, this should give you a good baseline to start from.

FYI, a friend just bought a 2003 EB z06 and broguht it out to HRP. Leaving at 3500 and slipping the clutch just a bit (not very much) he went 12.0x @ 118. Just remember, you can't dump it, you have to slip it a bit...

In October of 2001 my car went a 1.85 60' / 11.933@114.52 on the stock radials. That was leaving with a lot of clutch slip at between 4700-5200rpm.

As the summer came on I went back to the track, but in the summer even on a cool night the weahter is 85+degrees with nearly 100% humidity. So, I worked on launch technique.

I got my radial tire launches down. I was consistently cutting low 1.7 60' times on the stock radials. A long the way, the clutch started sticking to the floor. It finally got to the point that I could not shift the car to 2nd gear.

At that point I had the clutch replaced.

After that I decided to take a different tack. I decided rather than whoop up on another stock clutch I would try something differenet. My launch technique differs from Ranger, PowerShifter, Steve Row, and others. Its what works for me. It may not be the best, but it works for me. Here is a little insight on why I do it that way. All of my vehicles have always been stick vehicles with a hydraulic clutch. I drive one every day in fact. I have about 500,000 miles on car/trucks with a manual transmission and a hydraulic clutch.

Way, way back I would race folks in it. I could consistently beat any of my friends in the exact same vehicle by at least 3 lengths. They always asked me how. The common theme among them was that I had some kind of factory freak. It was by keeping the motor in the powerband, not spinning the tires, and launching harder than them, and powershifting. I simply applied those same lessons to the Z06.

I know I can launch on the stock radials, but I decided to not slip the clutch and have to replace yet another clutch, and simply see what the car would do if traction wasn't an issue. I already had a set of ET Streets, so I just started using them. I went from an 11.96 on them to an 11.802 to an 11.69 to an 11.61 to an 11.59... There is no magic, there are no tricks... Just more seat time than some other folks.

I decided to count my timeslips. I think that I have the majority of them. I had 85 total... There may be a few that I didn't have in my envelope that I keep them in...

47 of those came before I replaced the clutch. 38 have been made since... And in that time there have been a lot of Street races. And that is where the track time paid off. I have raced cars radial tire vs radial tire from a dig (a dead stop). One of them was a 2003 Cobra with (at the time 461RWHP). From a dead stop I could put 2-3 lengths on him that he could never make up. Sure his car made more HP, but it was heavier, and he couldn't launch it as well...

Just to humor you, :) let me share my slips on my trip to the track a few weeks ago. I went on radials, and it was very cold (mid to low 30s). The car was spinning at over 3000 RPMS no matter how much I slipped it, and it was spinning badly in 2nd gear. The first pass was launching at 5000 the second at 4000, and the third at 3000...

60' - 2.046
330 - 5.393
1/8 - 8.053
mph - 93.54
1000 - 10.330
1/4 - 12.253
mph - 117.53

60' - 2.060
330 - 5.365
1/8 - 8.006
mph - 94.16
1000 - 10.268
1/4 - 12.176
mph - 118.29

60' - 2.034
330 - 5.333
1/8 - N/T (clock screwed up)
mph - (same)
1000 - 10.242
1/4 - 12.153
mph - 118.15

Keep in mind all those passes had a lot of whelspin that increased mph. On passes where my car doesn't spin, but makes a good pass mph goes down, not up. High MPH is an indicator of wheelspin for me....

One other thing about all that is that you need totake into consideration weather. It can have a huge impact on ET. You need to take into account the SAE corrected number. Then you factor in the DA. Or, what is actually better is to use the dyno correction factor calculation, put in the weather information, and you can figure out what the HP multiplier is.

On a decent day C/F is .95 to .96 So, on a day when I dyno 372 corrected my actual is 389. 389RWHP is 439-440 crank HP...

When the weather gets even cooler, and drier that C/F can go down even lower.... The lower it goes, the higher the HP... This is basically free HP. The car will run better provided it hooks up. Don't look for record times in the heat and humidity.

[Modified by J-Rod, 7:40 AM 3/18/2003]


[Modified by J-Rod, 2:35 PM 3/19/2003]

J-Rod

Nothing done gear wise or transmission wise. As you say, look at the MPH. I ran an 11.933 @114.52 last year on radials... The DA was not -2000 on that pass. The 11.596, well I picked up MPH by pulling the cover off the airbox. So, from 114 to 117-118. The key to it all is 60' time. Most drag racers will tell you that dropping .1 off your 60' time will drop your total on your timeslip .15 to .2 on your total timeslip...

So no, sub 12s are easily believeable if you can launch the car. A friend of mine who is a heck of an Auto-X driver came out to the track in his brand new EB '03 Z06 recently. On his first trip to the drag strip in his car, he went a 12.0 in his car. His car is bone and only had only just passed the break in point. If he took an interest in drag racing instead of weaving in and out of cones, we might have another member of the sub 12 club....

What was the secret... He knows how to drive. I'm not knocking anyone for not having a killer 60' in their car or not running an 11.99 or quicker. Heck, the main thing is to just enjoy your car. I post on here, for one simple reason I know some of the stuff I have read on here has helped me do better. I am sharing what has worked for me. It may not work for everyone, it may not be what folks want to do with their own cars. It is simply information to do with as you wish. As they say YMMV (your milage may vary), or in this case YEMV (your ET may vary).

One thing I will say about my home track. HRP is 5 minutes from my house. It is the fastest track in the U.S. and has always shown itself to be. Pro-Stock usually sets records here because of the low elevation (18' above sea level). Its usually prepped well. But, we do have Texas heat and humidity. To give you an example. Although my best pass in 100% stock as deliver state was an 11.933@114.52, my 60' time was 1.85. As the year wore on, I worked on my launches. The problem was the Texas heat and humidity. In the middle of the summer it is 85+ degrees at night with 90+% humidity. I was cutting 1.74 - 1.77 60' times and only running a 12.0. Had those passes been made in cooler air, I would most likely have gone 11.8s or better. This was with the stock radials and the factory lid on the airbox.

Yes, heat and humidity do play a role. They eat HP, or they give it to you. But, some of it has to do with simply driving the car.
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01-04-2003
Removal of the stock airbox lid on 2002 Z06 worth 15.8HP and 11.4lb/Ft Tq
I went with the Southwest group to MTI today for Dyno day. This is the third time to the Dyno for me. The first time was at 1100 miles. The second time was at around 4000-4500 miles. Today, the car was at ~6700 miles.

In both previous pull, the car dyno'd within 1-2 HP, with two pulls per trip. This time the only change was to remove the factory cover from the airbox. I left the frame in place (including the center section). I used two tie wraps in place of the factory metal straps.

After my two pulls on the dyno I walked over to Jayson @ MTI and he said. The car made a strong pull. I asked him what it came in at. He said 372. I said that wasn't bad for an uncorrected number. He replied that that was the corrected number. I was more than a little suprised.

The two runs were 372.7/363.5 372.8/362.0 HP/TQ

Folks had complained before my run that the correction factor was off, because their cars were dyno'ing too low. The folks who I heard from before me were claiming to be low by about 5HP. Jayson checked his weather station before my run, and it appeared to be right on.

We pulled up my last dyno pull, and layed it over the one from this time. Across the board the open airbox pull was ahead. The two runs we looked at were 356.9/352.1 vs 372.7/363.5 My correction factor in both runs was .95. Weather conditions were almost identical.

My uncorrected number for those two pulls were 388.9/377.6 and 389.8/379.5

No magic, no tricks, nothing. The Stock airbox just simply seems to work pretty darn well with that restrictive cover removed. I am waiting to hear from Blu-By-U his car is about the same setup, but he has a Vararam. It will be interesting to hear how his car did. I left before he ran, since it was going to be well over an hour before they got to his car.

J-Rod

Now as for running on the ET Streets. Here is basically how that all went down. Hope this doesn't put you to sleep...

New personal best in Stock 2002 Z06 - 11.802@116.07
Well, I have had the car back for awhile since getting a new clutch installed. I had driven about 200-300 easy miles trying to "season" the new clutch and make sure it was "bedded" in properly before making any passes in the car. Last night was supposed to get cold (like down in the 40's). So, I decided that I would go out to HRP to try and make some passes in the car.

Rather than go out and smoke the brand new clutch, I decided that I would take the car out on ET Streets. I have cut about the same 60' on the radials vs the ET Streets, the main difference is that on the ET Streets I can "pop" the clutch rather than "ride it out" like I do on the radials. I think this is much easier on the stock clutch which is what I am after right now. I really don't want to have to put another clutch in anytime soon.

I was able to get in 9 passes from 6:45 to 10:30.

I ran the car with 14psi in the rears. On the first pass I pulled a good burnout since I hadn't used the ET Streets in many months. I staged the car and brought it up to 5000. It was "instant green", so R/T is immaterial. The car acted really stupid at this point. I un-clutched it and it rolled out, but it didn't feel quite right. I went to pull 2nd and discovered why. The clutch was stuck to the floor again. This time it was stuck, and slipping badly. To put it mildly, I was very upset. I chopped throttle, and the clutch pedal sprung back up. I put the car into second and finished that pass. I picked up the slip at the timing tower to find out I had run a whopping 12.842@114.79...

60 - 1.839
330 - 5.693
1/8 - 8.522
mph - 89.08
1000 - 10.873
1/4 12.842
mph - 114.79

Now I was a bit worried. Was a stock clutch going to be able to hold the car on ET Streets? Why was my clutch acting so stupid. I decided that the possibility was there that perhaps the new clutch needed a good pass to get settled in, and that even though I had made some easy passes on the street, that perhaps the first pass on the new clutch should have been a bit easier.

I let the car cool down, and put it back in line.

For the next pass I was lined up beside an open headered 68 Camaro. I indicated to the official that I didn't want to run that car since I couldn't hear, and besides in many cases I don't run some of those cars since many have a tendency to have way too much motor for way too little chassis. He didn't see things my way and indicated that I had to run this car. Things got a bit heated and he told me if I didn't run that car I would be thrown out of the track. I knew this not to be the case, and that he was the person with whom you indicated if you wanted to line up with someone, etc...

I am supposed to be the next car making a pass, but instead, I now am forced to pull out of line, and I was hot... I went up to the tower to talk to the officials. They directed me to the track manager (Linwood) who was lining up cars in the staging lanes. I went to talk to him. He told me not to worry that what I was doing was exactly what I was supposed to do. He told me to get back in line, and not worry about it. He got on the radio and called the guy I had problems with and explained things to him.

As I pulled back to the line the guy I had the issue with decided it was time to have a stare down contest. So, we stared each other down, and I made my pass... As a side note, I made 8 more passes and declined running several cars. I also set up races with a couple of other Vettes. He didn't give me any more static.

This time I decided to lauch at around 4000 RPM. Went through my usual routine and got the car staged. I launched, and the car bogged. The pass was better, the clutch seemed to stick well, but as I said the car bogged.

60 - 1.792
330 - 5.095
1/8 - 7.792
mph - 92.23
1000 - 10.092
1/4 - 12.038
mph - 115.91

The next pass was about he same except I launched the car @ 4500. The car bogged even worse than the launch @ 4000. And, I slowed down a hundredth. But in both passes the clutch seemed to stick with no real hints of slippage. Also, the clutch wasn't getting stinky. The time slip was as follows:

60 - 1.807
330 - 5.136
1/8 - 7.820
mph - 92.57
1000 - 10.109
1/4 - 12.042
mph - 116.69

Temperature had started out in the mid 60's with low humidity. As night fall came it began to cool off, but the humidity came up. DA was in the -100s, and was fluctuating up and down but showing a generally downward slope.

I began moving my launch RPMs up on each successive pass. The next pass I went back to my original 5000 RPM, and the clutch stuck with no problem. As in the previous passes the car "hit the tires" resulting in just a bit of wheel spin followed by the car bogging just a bit. The results were better, and I felt like I was moving in the right direction.

60 - 1.746
330 - 5.037
1/8 - 7.716
mph - 92.57
1000 - 10.005
1/4 - 11.935
mph - 116.79

A look at the weather station showed that we were looking at about a -460DA. Temperature was about 58F. 78% humidity and the barometer was at 30.08.

The 11.935 was the second best time I had made in the car to date. The 11.933 I had run last year was with a 1.85 60' and the mph was 114.52. That run was with the stock cover on the air box, and on the stock F1SC radials.

For the next pass I decided to move past my 5000 rpm launch window and look to launch around 5200 or so. The car launched clean, and the pass felt very good. And then tragedy struck. I did something that I haven't done in a long time, and something I have never done in the Z. I missed the 3-4 shift. Here I am cooking along on a textbook and I crunch 4th. I could not believe it. Once I missed it I just pushed the clutch in and coasted the rest of the way down the track. I picked up my time slip which further re-enforced my belief that this was a pretty good pass. Up until I blew it...

60 - 1.689
330 - 4.946
1/8 - 7.622
mph - 92.70
1000 - 9.916
1/4 - 12.035
mph - 101.34

One thing I did notice was that the clutch pedal seems to be a bit soft after my burnout. So, I decided to test something which seemed to help a bit. After I pulled my burnout, I would roll up, turn on the pre-stage beam, and then pump the clutch 4 or 5 times. This seemed to help out on pedal firmness.

I brought the car back around for the next pass. Again, I moved my launch rpm up a bit more. I brought it up to about 5500. Again, the car would "hit the tires" as it did on all previous passes. It would spin them for about 10 feet, bog slightly as it hooked and then just move out. I was able to power shift the car without any problem, and I could not hear the car "hit the tires" on any of my other shifts.

60 - 1.687
330 - 4.945
1/8 - 7.630
mph - 92.51
1000 - 9.924
1/4 - 11.865
mph - 116.27

The DA for that run was about -412. As I said, it would fluctuate up and down, but showed a general downward trend.

The next pass I was lined up with another Z06. I had a Vortex on it, but was otherwise stock (performance wise). I had given its owner a few tips after his first couple of passes and he had been able to drop over .5 by making a few changes to his driving style. He was quite happy with he cars performance thus far especially since he was able to drop .5 and pick up several MPH.

He rolled all the way in, so as soon as I turned on the second beam the dropped the tree. I was not ready and he just left on me. I was bring the revs up, and just dumped the clutch at about 5500. Instead of "popping" the clutch this was almost more like one of my radial tire launches. I ran the other guy down quickly and ended up beating him by about 3-4 lengths. After the pass he explained that he had missed 4th and had run a 12.80.

I picked up my slip at the timing booth and was pleased to see the following:

60 - 1.685
330 - 4.909
1/8 - 7.594
mph - 92-54
1000 - 9.890
1/4 - 11.831
mph - 116.04

They had a couple of kids working the booth, and they just handed me my slip and smiled. No one asked me about a cage the whole night... Life at this point was looking good. The lines were starting to get shorter as it was getting late. This meant my passes were getting closer together. I started to smell a bit of clutch stink, and new it was probably best if I wrapped things up pretty soon.

I lined up for my next pass and decided to launch @ 6000 to see if the car would do any better. It hit the tires and spun about 10ft or so. The rest of the pass felt pretty good. I picked up my slip and was both happy, and just a bit disappointed.

60 - 1.708
330 - 4.908
1/8 - 7.576
mph - 92.85
1000 - 9.866
1/4 - 11.802
mph - 116.55

I was .003 away from an 11.79. I know, I know. An 11.80 in a stock Z06 is pretty darn cool. But an 11.70 would have been even cooler. I decided that I would make one more pass for the night in an effort to see if there was an 11.70 in the cards.

I pulled the car around and quickly and got back into line. By this time there were only 1 line of cars left that were lined up to run. They put us in another line, and I was 4th or 5th in that group. They pulled us around and I lined up to make what would hopefully be my best pass yet.

I pulled my burnout, and they dropped the tree. The car hit the tires and spun, but this time I noticed that it hit the tires on every gear change. I knew this meant one of two things either the car was pulling even harder and I was on one whale of a pass, or the track was going away. When I picked up my slip I discovered it to be the latter.

60 - 1.673
330 - 4.955
1/8 - 7.643
mph - 92.26
1000 - 9.942
1/4 - 11.884
mph - 116.07

The track was finally getting cold enough that it wasn't going to hook anymore. So, I decided to take the car to the shop and put it up for the night. All in all I was pretty happy with the cars performance. One of the things I did note out there was the Blu-By-U was out there wit his car. He recently installed the VaraRam on his car. We started comparing time slips. Now, keep in mind he was on Drag Radials and I was on ET Streets. But, he was trapping 3 mph faster than me at the 1/8 mile. Most of my times were in the 92's he was trapping 95 and running almost 118mph trap speeds. His ETs were down to mine, but that can be explained by the differences in our launches. I found this to be very interesting. Now, one other thing to consider is that the ET Street @ 14psi does have a lot more rolling resistance than a drag radial. But, I still found 3mph to be quite impressive considering the softer launches.

I guess I will have to wait for that -3500 DA day when it is 45-50 degrees, around 40% humidity, and over 30.xx on the barometer. If I can get one of those days I feel pretty certain a 11.70 or perhaps even an 11.60 can be had...

Another new best in Stock Z06 - 11.617@ 117.67
I had been out to the track twice since my last personal best. Sunday the 15th and Friday the 20th. Sunday the track was hooking very very hard. I had my ET Streets set to 20psi, and the car was dead hooking on 6600 rpm launches. The car was bogging on the launch, so my times suffered a bit. Also, the temps and humidity were up a bit.

My first pass, as I said, the car bogged a bit, and I missed 4th. So, I just put it into neutral and coasted through.

60' - 1.650
330 - 4.902
1/8 - 7.565
MPH - 93.09
1000 - 9.850
1/4 - 101.72

The second pass the car was at around 196 degrees. The tires were still at 20psi, and the car bogged again on the launch. This time I managed to find all the gears.

60 - 1.685
330 - 4.965
1/8 - 7.642
mph - 92.74
1000 - 9.932
1/4 - 11.866
mph - 116.71

The last pass of the night was a bit better. The air had cooled down just a bit. The car spun just a little on this run, but still bogged more than it had the other day. This would have been a pretty good night for radial tire passes.

60 ' - 1.670
330 - 4.897
1/8 - 7.560
mph - 93.00
1000 - 9.847
1/4 - 11.783
mph - 116.57

I went came back out on Sunday to see how things were going to be. The weather looked to be good. Cool dry air with a good -DA. Everyone else had the same idea. I got to the track a 7:30 it was 9:47 before I got my first pass.

There was one other problem. Of my 4 passes I only got 3 of my timeslips. One of them was completely the wrong slip. So, although I had 4 passes I only have three slips to post. I will be getting the other two from the track after it opens back up.

I was at 20 psi in the ET streets, to get a feel for how the track was going to hook. When I launched on the first pass, I could feel the car spinning hard. I feathered the throttle and got the wheelpsin taken car of. The rest of the pass was alright, but it told me the track prep wasn't as good as the other night. That of course would work to my advantage. That pass was good, except the 60' was of from the wheelspin.

60 - 1.777
330 - 5.005
1/8 - 7.640
mph - 94.05
1000 - 9.901
1/4 - 11.814
mph - 117.98

The second pass I was set to race a Millennium Yellow 2002 Z06 with a ProCharger on it. I was running my fans in the lanes, and disaster struck. I fired the car to drive up to the head of the lane, and I shut it off. When I went to re-fire the car all I got was click,click,click... Dead battery. Some of my friends were nice enough to push start me, but they wouldn't let me make a pass without the car starting on its own. They made me kill the car, which of course wouldn't restart. Now, I am up by the burnout box, the car won't start, and everyone who is going through the water box is spraying my car. I finally got them to allow me to push the car back. We push started it again, it fired immediately, and I parked it for a second to let it charge. I walked up to the starter, and he told me to hold on for a second, and he would go ahead and put right back in the lane, so I didn't have to go back through the line.

It just so happened I got lined up with LovintheC5. The ET Streets were set down to 16psi, but the car was getting up in temperature from sitting there idling. The pass was Ok, except that in the top of 3rd, the car made a stupid move on me. It really hasn't done that to me on the ET Streets. I have had that before, in some of my other cars. Rather than mess with A pass that was sub-par anyway, I just pushed in the clutch, stuck in neutral and coasted across the line.

60 - 1.739
330 - 5.050
1/8 - 7.721
mph - 93.17
1000 - 10.007
1/4 - 12.172
mph - 97.69

The air was cooling down, but the south wind was blowing. The gulf air was driving the humidity up. When I got there, the dew point was at 27^. But now, condensation was forming on my car.

I pulled the car back in the lanes and talked with several Z owners there was a guy who is a regular forum lurker who was out playing with his MY 2002. Two guys with an EB 2003s who I talked with, and of course the guy with the procharger equipped car. Another new owner had his brand new 2003 MY car that he had just picked up in Kansas City and drove to Houston. It still had paper tags on it... We talked about launch RPM, tire pressure, etc... I tried to fill them in on what worked for me, and what to expect on your first few times out, and what the car can do with a bit of practice.


We sat in the lanes while the cleanup crews worked on yet another oildown. I finally got around for my next pass. For this pass, I did a really good burnout. A really long, smoky one. I tached the car up, and turned her loose. I was rewarded with some good wheelspin, but the car really moving out good. I picked up my timeslip and was happy to see that the car had 60' its best so far, and that resulted in a new best.

60 - 1.622
330 - 4.804
1/8 - 7.437
mph - 94.08
1000 - 9.700
1/4 - 11.617
mph - 117.67

Right before I made my pass I heard that the lanes were closing in 10 minutes. So right after my pass, I came back around and got in the end of the line. Right after I did, they closed the lanes. My last pass was with a Ford Lightning. I got his slip, which I didn't notice until I had left the track. So, I don't know if it was better or worse than the 11.617. But i will post back once I get the results from the track...

A couple of thoughts, I know that many folks feel like you need 200 miles or some such number to get the full power of any modification. I just want to point out that I completely cleared my computer (dead battery), and after one pass plus driving back up the return road, my car made the best pass it has made to date. I think at this point I am going to have to disagree with all the driving time needed to see an improvement. I suspect you could install a cold air intake, and if you so desired, clear the computer. After one of two passes you should see all the performance gain you are going to see...

Perhaps if I ever get a CAI, I can check this out at the track and post the results here.

Again it was good meeting new owners, and folks who are making their first few trips out to the track.

There is a difference between a drag radial and a tire like the ET Street. But to answer your question, you can hurt your 60' time if the track is prepped to well. But, with a BFG it is possible to overpower it. Let me give you an example. When I ran your car. When I launched it, the tires were right on the verge of going up in smoke. When I left, they were barely spinning about halfway through 1st gear which resulted in a 1.73. But, I think some heat in the tire is important. The thing that you have to do is modulate the throttle. Some folks (like Powershifter) dump the clutch at about 3500 and spin the tires for about 20-30 ft and modulate the trhottle. I modulate wheelspin through tire pressure. But, the other thing is that your car has at least 30HP on me. We can try to make a pass with no burnout, but I feel like the car will do like my car does with too much tire pressure. ( Lots of smoke, not really good times.) One thing I would like to see you do is do a big hairy burnout, and turn the car loose at about 5500-6000. Blu-by-u did so the other night, and got his best run to date. Anyhow, after the track opens back up in January we can get together and try all this out, and see what works...


New Personal best in Stock 2002 Z06 - 11.596@118.53
My Dad and I went out to Houston Raceway Park tonight to make some passes in the Z06. Dad was videoing the car, and watching how the car was leaving. The weather yesterday was ideal. The big question was, would it last. The answer was no. The weather late in the afternoon was on its way to worsening. It was going to be a race to see if I could make it to the track and get some passes in before the track got too cold, and the weather got too bad. When I got there there were a few guys I know running (Mike Texas SS,mmiller, DJ99SS). They reported the track was hooking and the cars were flying (which was what I wanted to hear. I had planned on being there when the gates opened, but got there an hour late. I made my first pass at 6:16 and it turned out to be my best.

I had my ET Streets set @ 20psi. When I launched the car, the clutch stuck to the floor. Rather than lift, I went ahead and drove it trough. I made the 1-2 shift, and the clutch stuck again. Once I pulled third it popped off the floor. It didn't feel like second pulled as it should, and I didn't expect it to be a good pass. But i was suprised to see I had a new personal best.

60' - 1.675
330 - 4.822
1/8 - 7.442
mph - 94.62
1000 - 9.692
1/4 - 11.596
mph - 118.53

I hustled the car back around and gor it set up for the next pass. The air was so cold outside that as soon as I drove up the return road, the car was already cooled down. I figured that the clutch would probably engage like it should on this pass. It has messed up on the first pass once before.

I was right. After I pulled my burnout, I launched the car. This time it hazed the tires most of the way through first gear. So, I knew I needed to drop the air pressure a bit. I picked up my slip and saw that the car had slowed a bit.

60' - 1.706
330 - 4.911
1/8 - 7.538
MPH - 94.38
1000 - 9.792
1/4 - 11.698
MPH - 118.45

I brought the car back around to make another pass. This time as I was about to make my pass, someone oiled the track down. So, we had to wait 30 minutes while they cleaned and prepped the track. By this time it was dark, the temp was dropping, and the wind was blowing fully out of the east. The car was cooled down after this delay, and I figured that this was going to be my best chance at making another good pass. I dropped the air pressure to 17psi to see if I could ge the car to hook.

I pulled my burnout, and launched the car. This time it spun a bit, but when it hooked it bogged just a bit. But, it felt like a decent pass. The track was getting cold, and the car was starting to move around on the big end. I picked up my slip and was disappointed.

60' - 1.655
330 - 4.822
1/8 - 7.442
mph - 94.33
1000 - 9.702
1/4 - 11.616
mph - 117.86

The next pass the car went stright, but just feel off a bit more in performance.

60 - 1.655
330 - 4.865
1/8 - 7.516
mph - 93.52
1000 - 9.789
1/4 - 11.711
mph - 117.33

There was a pretty good cross wind blowing across the track. I decied that I would make one more pass. If the car fell off again, I would hang it up for the night. I figured my window had passed me by. I launched the car it rolled out hard, but once I got into third the car began to drift. I stayed with it until I was in 4th. The car began to move too much, rather than stick it on the wall, I put it in neutral and coasted though.

60 - 1.619
330 - 4.785
1/8 - 7.429
mph - 93.74
1000 - 11.684
MPH - 108.45

Well, there went my best pass of the night. From the looks of the 1/8 mile split, it was on its way to a low 11.5x pass. Probably around a 11.54 - 11.52...

At the timing window they asked me how the track was. I told them it was going away quickly on the big end. They shut it down to have a look. By this time I was frustrated and just decided to hang it up for the night. I might have made a better pass if I had stayed. But I will wait, and hope for another good air day is somewhere around the corner... Besides, I didn't want Dad turning into a posicle. He was standing out there in the cold with a camera while I was in the car (thanks Dad).

Before I left, I saw another Z06, a red one, about to make a pass. I went over and talked to the owner. It turned out to be Ryan Bell. He made his pass, and then I met him and a few friend of his back in the lanes. As always, it was nice meeting another fellow Z06 owner. Ryan was working on his launches. That combined with a cold track and rear tires set at 32psi was causing him to spin a bit, etc... Anyhow, I was about to leave, but he was staying around to make a few more passes. So, I left.

Anyhow, my quest for an 11.49 was thwarted, but at least I got into the 11.50's. I think if I had gotten there a bit earlier and got the tire pressure sorted out a bit sooner, the car would have laid down a better number. Oh well, all the speculation in the world is worthless. The only thing that matter is what is on the slip.

And again just for the record. The car is still bone stock, no aftermarket intake, no tuning, no headers, etc.... The only thing I have done to the car is put some ET Streets on, and pull the lid off the factory airbox.

fpcopo

JRod you are one heck of a Z06 drag racer. I have a couple of questions for you. What is the tach reading in the lights? Also have you tried either putting a block on the floor under the clutch pedal or seeing what the air gap is on the clutch when it is pushed all the way in? I don't know if you can get a feeler guage to the disc on the Z but I think your clutch is over centering and the centrifugal force is holding it down. The thing that makes me think this is you said the clutch got soft after it sticks. The pedal is coming up a little when the pressure plate is stuck down and I think it got some air in your hydraulic clutch line. We used to stop the clutch sticking in the old days by blocking the pedal to stop the clutch from going in any farther than it needed to shift. Usually on a diaphragm type clutch this was with the disc to plate air gap of .035"-.040". If you can't check this, experiment with blocks of varying thickness. I used to use a 1"X2". But you could start a little thinner. If you go to 1/2" use oak or you will smash the wood when you shift. :D

J-Rod

fpcopo - Thank you for that valuable information.

The car is only in 4th for a short time due to the 3.42's. I can't tell you the exact rpm, but calculating a 25.5" tall tire with a 3.42 @ 118 is 5314rpm. For a 26" tall tire (ET Streets) 5215. For 26" tires @ 117 5171 rpm.

The clutch on the Z is nice in that you can pull the inspection cover off. I suspect that I will be pulling it off soon to check my airgap.

I know this is critical in manual type clutches, as I have a friend who has a manual in his dragster, and several friends who run a Lenco or Liberty in some big cars. I hadn't given much thought to the fact that GM may have engineered in too much travel, but that certainly stand to reason as a possibility.

Again, thanks for the tips and I will report back what I find...

BLU-BY-U

Jrod, how has your trap speed been affected with the et streets?

J-Rod

I would say a small drop in MPH. Perhaps 1 MPH. Look at my 1/8 mile and 1/4 trap speeds vs yours. I see about a 1 mph dif.