okinawa86vette

Well, here you go. The first one is one we did with the power key in the normal power mode. More out of curiosity....the dyno guy wanted to know and I did too.

The second chart is in full power. The lower hp run was not long after I got there and the car was still hot. It was the lowest run of the day. The other is the best run and done after cooling off for a bit. The other runs were similar to this one...within a few HP.

The car is bone stock. Of course, the numbers are all rear wheel horsepower and torque done in 4th gear. Unfortunately, the printout showed MPH instead of RPM, but it's 4th gear with stock 3.45 gears, if anyone wants to do the math. Plugging the numbers into an online calculator, peak HP came at about 6000rpm and peak torque around 4800rpm....dead on for the factory specs.

I'm pretty happy with how the car did. It's definitely running ok.....

So, here you go.....

Normal Power mode: 203.80 hp / 260.50 ft/lbs



Full Power mode: 331.53 hp / 330.60 ft/lbs

Meanmyz

Way to go Chris. Now you know. If you figure about a 17% driveline loss, your numbers are looking real good.

By the way, I sure didn't mean to sound like I was down on the LT4, because I really like that car/motor too.

Just something I kind of remember from the 2010 C4/ZR-1 Gathering...John Heinricy and Fred Gallasch (Chevy Marketing), and a few others talked about the Grand Sport in one of the seminars.... I remember Heinricy mentioning something about the conservative rating on the LT4... As I remember, Heinricy was relating on how he was talking to Dave Hill during development of the Grand Sport and LT4. Dave Hill made it clear that there was "no way" a one year, outgoing production motor was going to have more horsepower than the newly introduced incoming C5. Can you say..."under-rated" At least that is the way I remember it.

okinawa86vette

No worries.....I've heard that too.....and the numbers show it....you don't see too many bone stock LS1 cars running 12's..... but that's not uncommon for the LT4 guys.

I know my green car ('96 LT4 coupe) is quite a bit quicker than my friend's 2002 6 speed coupe. I've heard the torque tube setup adds in a little more driveline loss, but that's just hear say.....

When I get a chance in the next couple weeks, I'll take the green car down to the dyno and see what it pulls. Very curious to see real numbers on 2 real cars side by side. Feelings are great, but the butt dyno is fairly inaccurate. Even track times are misleading because of weather conditions, driver, track conditions, etc. Taking two cars to the same dyno in virtually the same conditions is a pretty good equalizer.

C

SurfnSun

Driveline loss is more like 12-15% for an M6 C4, most people stick with 15%. At 15% you've got a strong running car @ 389 crank hp. If you were to use 12% loss, you're at exactly rated hp. The debate has raged on forever. I believe I read an interview with John Lingenfelter who stated they use 15% on the C4 back in the day.

Either way...Congrats on a great car!

FU

Average numbers. Now pull the plenum and injector housings and port them up for a 20 RWHP increase with absolutely no down sides except expence.

WydGlydJim

This is a pretty cool comparison you are doing.........

okinawa86vette

FU,
Please post your dyno charts from when it was stock and then after porting. I always like seeing before and afters...only way to really know.

I wasn't posting to claim I had more than a normal LT5. As I said, the car is stock.



C

Meanmyz

Even better! I couldn't remember what it was.

Meanmyz

He's just saying there isn't anything wrong with your car.

FU

Correct.


okinawa86vette , I'm sure someone on here can post the chassis dyno numbers before and after the top end porting.Typical results on a 90-92 car are @ 30-34 rwhp and 11 lbs of torque. Check Marc Haibecks site out : http://www.zr1specialist.com/HAT%20W...%20porting.htm

My car has a little more done to it than that.

ghlkal

Very nice

mike100

Maybe it has been done before, but I would love to see the LT4 car dyno run plotted over that one. Same dyno, same elevation and correction etc... (easy to spend other people's money- haha).

I weighed my 91 this week and it came out to 3400 lbs so the regular coupes will always be about 150 lbs lighter- that is another factor.

mike100

As a not very scientific comparison, my car with factory exhaust manifolds, a cat-back and porting made the same torque, but 350 rwhp on the same dyno type. my run was done in 3rd gear though- I think it had a few more lb/ft in it if it was run in 4th, but you get the idea- porting helps extend the torque curve flatly to a higher rev and allows a higher peak hp.

FU

Big Diff.

okinawa86vette

3rd gear dyno runs aren't really valid for comparisons.....you're adding in a gear multiplier. The reason 4th gear is the accepted method is because it's straight through, taking out any multipliers from the transmission.

The guy who ran my dyno mentioned that a lot of the import guys request pulls be done in 3rd gear.....it'll post bigger numbers for bragging rights, but really means little when comparing to a straight through ratio pull.



FU,
I knew what you meant.....I just like seeing before/after dyno runs or track times. It validates claims.....I wasn't calling you out or anything.

Even a dyno run comparing modified and stock, but physically different engines can throw things off. LT1, LT4, LS1, etc dyno all over the map and it's entirely common to see 20hp or more difference between "identical" motors....so many factors involved. I just haven't seen enough baseline LT5 pulls to really know what's normal for these cars. Scouring the internet pulls up very few completely stock LT5 dyno charts. One of the reasons I posted was to show what a good running stock one runs....and to prove a point from my other thread that the car is, in fact, running right, despite my LT4 feeling stronger in the lower RPM ranges.


BTW, I will eventually be dyno'ing my current LT4. It's stock, just the same as the ZR1. The dyno's in El Paso, so it's a little bit of a drive. I will probably get to it in the next couple weeks when I have some time off from work.....shift work and lots of overtime doesn't leave a ton of time for fun stuff.

I'm not sure if he'll be able to overlay the graphs or not, but it doesn't hurt to ask. The LT5 made more torque below 3500rpm than I was expecting. It's entirely possible that my LT4 feels stronger at lower RPMS because it's a little snappier, less smooth, etc, but is really similar in low end grunt. Just shows how inaccurate a butt dyno can be......

Chris

FU

bb62

A couple of things you should be aware of. Based on marketing/engineering studies of customer satisfaction with respect to acceleration, two interesting factors came out:

1. The greatest mover of customer satisfaction in acceleration was not the engine itself, but the angle of the gas pedal to the throttle opening. The greater the angle (to a point), the greater the satisfaction with the car's acceleration (and the "snappier" it would feel).
2. Cars with more uniform torque characteristics tended to feel slower - even if they that torque was a bit higher up the scale. As an example, if you go back to the 60s, you'll find that many people thought the big blocks were slower than the small blocks because of how the power came on. The big blocks didn't have that explosive acceleration when the cam came on - so the customer didn't feel it - except that the big block was much smoother with its higher acceleration from the start - obviously driven by the higher torque curve which was across the rpm range.

okinawa86vette

I do agree.....it's why a lot of people think the tiny motored imports and domestics feel fast.....when they give 10% pedal input, they get 50% throttle....hypothetical numbers, of course. But the illusion falls apart quickly as you get deeper into the pedal.

I'll be curious how the torque curve on the LT4 compares. I don't think the LT4 gets (or needs) that kind of trickery. It definitely has a more violent feel to it, where the LT5 is very smooth....kind of like the difference between a reciprocating aircraft engine and a jet engine.

Driving the cars back to back, the LT5 accelerates deceptively quick. I need to just take a road trip back to GA and get it on the same track I last ran my CE.

I'm not sure when I'll get to the dyno with the LT4. Probably in the next couple weeks as time and money allow......I work shift and a lot of long hours.

Chris

scottfab

FWIW here is a Dynojet plot of my stock LT5 (90)
The plot differs from yours in that it shows RPM not MPH and the Y axis begins at 100 instead of 0. Also on your plot it shows "smoothing".
I assume that my plot does not have smoothing on plotting the data as is evident by the jagged plots.

Paul Workman

Perhaps the same can be said then about the LT5 vs. LSx motors. Lots of people go into hyperbole over the low/mid range seat of the pants feeling they get from the LSx. However, the fact that they have to shift and the LT5 is still pulling is lost on many of them until they experience this themselves...

I love it when the C5 passenger says, "HA!" as they first jump the ZR-1, followed by a surprised, "Huh?". Then as the Z's tail lights continue to pull away, "Your NOT catching him!"

Every time the C5/LSx driver shifts, the Z noticeably pulls away smartly.

Priceless