thesubfloor

I encountered something tonight which makes almost no sense to me so please feel free to offer up any suggestions or ideas you might have.

Here's the Reader's Digest version of where things were at with my car up until tonight:

• I ran my fastest time ever of 11.479 back in March with the following mods: Vararam, cam, headers, 3000 stall converter, 3.15 gears, drag radials, tune
• I blew up my differential 2 months ago and upgraded to 3.42 gears.
• After the gear swap I was able to pull off a time of 11.504 which when you account for the difference in temperatures (March vs. June) is pretty much equivalent with the 11.479.
• I blew up my transmission last month and ended up with a stock torque converter in the car instead of the 3000 stall.
• Without the stall converter, I expected the car to run anywhere from 0.3 - 0.5 seconds slower based on what I've read in posts here and in various other places on the Web.
• After fixing a vacuum leak from the Vararam and going to the track a few times, I was pleasantly surprised when I managed an 11.734 two weeks ago which was only 0.226 slower than my best time with the 3000 stall.

So far so good, right? Oh how I wish it were that easy.


I went racing tonight and much to my surprise/shock/amazement ran the 11.522 shown below.

The reason this didn't make any sense is because my best time without the converter is only .043 seconds slower than my best time with one. If you also consider that they don't spray the track with VHT on Wednesday nights, I might actually be able to run faster than 11.479 if the track was properly prepped.

Although the torque converter was a reworked stock unit and not a brand name, I do believe it worked properly because I used to get sub 1.8s 60ft times on a pretty regular basis with it. I also verified through my HP Tuner that it was stalling correctly.

Normally I would probably just think "Cool, my car's pretty fast" but since I was just getting ready to pull the trigger on a high stall converter, given the events of tonight I'm starting to wonder if it'll be money well spent or wasted.


If I do decide to go ahead and install another converter (probably a 3600 because of my gearing) I figure one of two things will happen:

1) I will be able to pick up 2/10ths or more in the quarter mile (desirable)

2) The car won't run any faster because for some reason my current mods are such that a converter isn't going to help (not so desirable).


If you're still reading, thanks for being patient with me. I'm open to any and all suggestions or explanations so please feel to start offering them up.

Christopher

Slwsvt

Is'nt the stall most beneficial for the launch and first 60'? Might help you to get in the 1.7's. I believe every .10 on the 60' is worth about .2 overall in the quarter mile. Do you think maybe going to the 3.42's helped you pick up another .10 or .15 thru the quarter?

LS1LT1

Well, yes and no. One would need to know the exact temp and density altitude differences to say for sure but I've seen people run as much as 4/10ths slower between March and June in my area...meaning that (on paper) your 11.50 in June might have still been notably quicker than your 11.47 in March.





Or
3) The PCM/TCM just will not tolerate that high of a stall and the transmission will act all funky, though hopefully not.
But if that 3600 stall still allows the trans to function properly, the car will pick up WAY MORE than only 2/10ths in the 1/4 mile, all else (weather conditions, track prep and driver) being equal.

Either way congrats on the new passes, that car has some great track times to come.

LS1LT1

True, a properly working higher stall converter will help one's sixty foot as well as the shift extension which is essentially limiting the amount of rpm drop/keeping the revs a little higher between shifts. The beauty of the A6 trans is that it sort of limits that rpm drop off in stock trim just by nature of it's design and might do it even more so with gears (be they 3.15s or 3.42s) so that's why some might feel that a higher stall converter simply won't help it as much.
But frankly, hitting only a 1.83 sixty foot in a cammed/bolt on'd/geared/tuned/drag radialed/'reworked stock stall' C6 is quite weak.
Some of us have hit 1.85s with only a Vararam, t-stats and some tuning so those sixty foots have to come down.
And a higher stall with a solid focus on it's tuning parameters might be the key to lowering them in such a modified car.

thesubfloor

Is there any way of determining what the DA was for a given day in the past? I checked a few weather websites but didn't find anything.

According to Yank, they have a few customers running 3600 stall converters in A6 transmissions and they've apparently been working fine so far.

Thanks, the car is a lot of fun which is why I race whenever and wherever I can. I'm currently having a bit of a problem with the car shifting too high (at around 6900 rpm) which is causing me quite a bit of wheelspin. Once I get that solved, I'm hoping to squeeze another tenth or two out of it.

thesubfloor

Weak, huh? Ouch, that hurts! (just kidding).

That's something that a lot of people have commented about my car - that it almost seems slow off the line but picks up really quick towards the end. I regularly race people who get 1.5s (or faster) 60ft times but usually catch them by the end.

Joe_G

Since you seem intersested in understanding the why...can I recommend that you keep a spreadsheet of all your runs, and calculate the splits between times noted. I also invested in a weather station that gives me DA info (you'll likely see many at the track and can ask folks for the DA if you don't want to buy one).

While my BEST times are shown in my Sig, I can tell you that my averages are a couple of tenths lower...it's actually more meaninful to calculate an average for your mods. You'd think my cam didn't add that much based on the difference below between bolt ons and cam but on an average run basis the cam added quite a bit every run (assuming I launch and shift properly which is a wild card with a manual! lol) I will be willing to bet that if you calculate some average times for your various mods, calculating in the effect of DA (which is dramatic) you will find that the data supports the fact that your gears and converter do indeed provide faster times.

This has more meaning than you might think, as I saw people quoting your specific experience in a thread as a reason that gears don't add anyhing to the quarter mile experience and I can tell you from personal experience (and every guy in the corvette challenge at moroso) that gears do indeed make a difference in quarter mile times and speeds.

Making that assumption off of your best run ever with various mods means you're not getting a meaningful answer as to what mods do what.

Be happy to show you my spreadsheet if you're interested!

thesubfloor

Sure, I'd love to see it if you'd like to e-mail it.

Thanks,
Christopher

Joe_G

happy to. shoot me a note to joegut at gmail.com.

thesubfloor

Just sent you one.

DOUG @ ECS

Are you basing this off of just a few passes, or many and those were the best times?

LS1LT1

That's all that matters, the one who gets there first.

thesubfloor

I've got over 200 passes in the car altogether.

mkr3686

Christopher,

I think a good quality Yank or PI converter will make a noticeable difference over any "reworked" stock converter. It's no suprise to me that a tweaked stock converter gave you little performance increase. Any Yank/PI converter not only have much better internal parts but is also a smaller diameter which significantly lowers weight. The reduction in weight on such an important piece in your drivetrain makes a noticeable difference.

mkr3686

Look at the other A4/A6 cars running converters on the fast list and you'll notice quite a few in the low 11's and even now pushing high 10's.

Kenny H

I'd shy away from less no-name convertors. Yank/Vig are the two biggest players with 4L60Es, I'm not sure about the A6s.

If you do not drive the car a lot you may want to opt for something a little bigger than 3000.

thesubfloor

The only converter I've had in the car so far was that reworked stocker. I ordered a 3600 yank on Friday which should be a good match for the 3.42 gears.

Joe_G

You will be knocking on 10's door with that converter based on my buddies' good experience with it. My shop's car gets 11.15 with in a c5 with ls1 cam only and that converter and gears (3.90's) in their full interior car.

Excellent choice IMHO.

LS1LT1

I didn't realize they were both 'modified stock' converters all along, that could very well be part of the problem/lack of better results.

thesubfloor

The one in the car right now is stock and untouched. The prior one was the modified XLR one set up as a 3000 stall.