0Mike69@ECS

I finally got a chance to Dyno my car last night. It didn't put down what I would call stellar numbers. ~ they are ok I guess, but I expected more.

The #'s were 275 hp, and 319.9 tq.

This is with my ZZ4, M20, 3.36 rear.

Either I have more than 20% drivetrain loss or my motor is a little sick!!! The ZZ4 is supposed to produce 355 hp and 405 torque at the Flywheel with pulleys and a full exhaust. (15% loss would be around 301 hp / 344 tq, and 20% loss would be 284 hp / 324 tq. )

I know it's not exactly running great (I haven't tuned it in months and it was running a little crappy yesterday) but I still expected to see at least 10 more hp & torque from it!

The Good news is, after the pulls I finally re-set the timing (I had to bump it down out at the Cruise in due to crappy gas) and it felt like it was back to normal. Let's hope it shows in my et's at the track tomorrow.... the best I could muster last time was 13.5 @ 103. Which is a touch on the high side of normal for me... then again it was 90+ degrees. Tomorrow night should be in the low 80's and maybe even 70's!!!

How much Drivetrain loss have you guys seen????

MWILLET

I hear ya.... a couple years ago I stuck a ZZ3 in my '80 along with Twisted Wedge heads, Hooker headers, hi-flow cat and mufflers and a Carb Shop Stage II Quadrajet. After several passes and some tuning, we finally got it up to 251 rwhp and 308 rwtq. I wasn't amused. Some Forum members recently recommended a local Corvette shop that's supposed to have an excellent reputation, so I'm hoping he can help me corral my missing horses.

rainman69

Crate motors are not measured in SAE Net, they're measured in SAE Gross. Which means that although there might be engine driven pulleys and a "full" exhaust, "performance still differs on the street." Unless I'm completely mistaken. :smash:

Darkness

I feel for you, but a last year I went to the dyno and pull some #'s that left me :( mean while on the way home I noticed that the car wasn't running good and if I left the gas it would come to a stop real quick. What happened was that the e-brake's cable got stuck some how with a tiny little rock and this made it brake just enough to take hp/tq from my #'s.

Well I'm not saying that you have the same problem but some times it can be a simple thing like this and not you engine.

Good luck :cheers:
Paul

68shark

Mike, please see the numerous dyno threads re Agostino/Toronto guys etc, one of which is running right now. Ghostrider's ZZ4 pulled numbers less than yours (259rwhp, as I recall) yet sounded very strong. Think he was pleased, but I don't know how his set up compares to yours. I've heard the 355 rating is also gross (but not quite the exact gross of the old days) thus you would have to reduce the 355 (how, I don't know...) to get true net then deduct friction losses. My guess is your numbers are pretty good (assuming a stock ZZ4), considering you mentioned it wasn't finetuned.

Chuck Harmon

Mike,

When they quote Gross HP, they are using approx 70 degree farenheit air temp. Even though the dyno should correct for the 90 degree ambient air temp during the test, your underhood air temp was probably closer to 150+. You will pick up 1% power for every 7.5 degrees you reduce the air temp. I expect you are losing nearly 30 hp because of this alone!

Chuck

0Mike69@ECS

Thanks for the imput guys... I'm going to try and take some time to fine tune it and strap it back on... I was hoping to start on a couple of mods next week, but I wanted to get an accurate base line first I hope these # are a little off from what they really are.

68shark... thanks for pointing me to that other thread.... at least I know I'm not alone!!!! :lol: :lol: :lol: :lol: :p:

QuickVet

glad to see you have a good base line number for your future mods. Those numbers are similar to mine. See you at the track tomorrow.

BTW, find out what jets you are running. I went down two sizes in the front and ran a bit quicker. I was running 12.99 at 105 in 90 degree weather last sunday.

Pete79L82

The 355 HP is NOT with an exhaust system. Here is the informtion from GM's site:

"The 355 HP @ 5500 RPM was derived from a superflow dyno using a 4 barrel 650 cfm Holley carburetor P/N 80541-1, 32" long by 1 5/8" to a 1 3/4" stepped header with a 3" collector, and 92 octane unleaded gasoline."

When you dyno a motor the only thing that the motor has to turn is the water pump. There is no other accessories on the motor. The carb uses a velocity stack (in which the air turbine is mounted) which is much more effiecent then any air cleaner. You have to use the fuel pump from the dyno so you can use the fuel turbines so the is no fuel pump on the motor. They are using step headers which will broaden the torque curve and raise peak HP. The end result is that installed in the car the motor will probably make 10-15% less power at the flywheel than on the dyno. Add to that the loos through the drivetrain.

275HP at the wheels is pretty respectable!

MotorHead

The way I look at it, I was happy with the performance of my car before I dynoed it. I was hoping for over 300 RWHP and it came out to 285, I am happy not disappointed. That is what it pulled on that day, the HP quit at 5 grand and I know the cam and heads etc. should have pulled to well over 5000 RPM which when I find out what the problem is I will get my 300 + RWHP no problems

The point is, if you were happy with the power before, why do you say you are not happy because of a few numbers on paper. I think one of the biggest problems is all the huge HP claims floating around and everyone is a little skeptical of these claims to begin with. WHen you actually measure the performance in the real world you get disappointed becasue you believe you had all this HP, but where did it go.

There is nothing to be disappointed with 275 RWHP, ( stock C3's 75-82) would be lucky if you could squeeze 150 RWHP out of them) if you put slicks on your car you could pull the front wheels off the ground :D

gdh

I am most assuredly with MotorHead on this one. hp and torque are only 2 of the ingredients that go into making a car potentially fast. The key is the driver's abilty and no dyno can show that. I have no interest in dyno #'s personally, but get me to the track and lets see how I do at the Mosport circuit. Now that would be fun, Andretti curve anyone?

69stingray

The factoid of the day. Very Nice. ;)

Rottenrob

[QUOTE]
You will pick up 1% power for every 7.5 degrees you reduce the air temp. I expect you are losing nearly 30 hp because of this alone!

Chuck

The factoid of the day. Very Nice.

yes I'm logging that one too! :chevy

Fevre

That's plagerism! (sp?) :D

I wrote almost the same line in a thread by Grandsport. I would be deflated if I saw my dyno numbers but am very happy with my engine right now. It ain't a rocket but it gets up goes. Now the tranny is another story....

But we all have bench marks and seek to reach them. Now take your dyno and compare it Monty's :eek: . My benchmark is a little lower than Monty's. :lol:

0Mike69@ECS

Thanks guys you are right! I'm not really dissapointed just because of the number that came up on the screen, I guess it's just that you always would like it a little higher!!!

I can drive the car pretty well.... I've taken it down to 13.3's @ 104 which is pretty good for 275 rwhp and 3310 lbs I think. I still feel like there is a little more in there - and I would like to extract it all before I dig into the engine!

Aaron.... I went a bought a complete jet kit... because the car is a little rich, and my goal at the dyno was to find out exactly how rich it was so I could change the jetting. But by the time I reset the timing it was a little to late to dig into carb.... I do plan on spending a full day next week tunning... I'll let you know what I find.

Gordonm

Hey Mike, those numbers should be a little better but I think with carb tuning and jets you would improve. I would suspect my numbers to be around those also. I know there is more in mine with carb tuning and timing just don't have the facilities to do it. Where did you dyno it. I would be curious on mine also. I think I could be in the mid 12s with more tuning. I'm on vacation till the 21st so I'll be in touch when I get back

SuperFast80

This is a great thread! :cheers:

CDaniel525

mike....thats not too bad.
Its basically the same amount of loss I have in my zz4 w./ hotcam

went from 396HP @ crank to 306 at rear wheels = 23% loss

GrandSportC3

Did you have the engine dynoed for crank Horsepower before installing the engine in the car??? If you did - 23% looks like the % of loss you can expect. I only dynoed at 325.3 with my 465 HP engine... However - with a new carb, open exhaust and some good tuning I'm sure that I would get to close to 360 RWHP which would be a approx. 23% loss...

:cheers:

Olivier

QuickVet

whats happening mike? what jets were in there? huh, huh, huh??? :blueangel: