Birdie2000

Hey guys

One of my buddies has a 1995 Z28 that weighs about 3800lbs with a 383 in it and its a 6spd
and 3.42 gears

He got it dynoed and is wondering why it is lacking some (alot of) performance.

Dyno Graph

The stock casting heads supposedly flow:
.100 64.2 47.8
.200 132.8 92.3
.300 188.6 134.5
.400 237.7 160.0
.500 267.1 179.1
.550 277.8 186.9
.600 279 191.7

Cam is a 230/236/112 .544/.555 lift with 1.6 rockers
Stock intake manifold/stock tb/stock injectors (DC were only at 83% max on a WOT street run
up to about 6300rpm)

Compression is a static 10.7 or so, but its cut down b/c his elevation


We thought it would have made at least 400rwhp and about the same amount of torque. He
suspects the heads, what else could be losing 85hp?? And why does it take a dump at 5000
rpm?

He has trapped 104 mph at a 10.5k DA, but we're not sure what that converts to at SAE
conditions.

Thanks guys

edit: Oh, by the way, he has a base tune from pcmforless

84FTA

I have a friend like this also

slopokrodrigez

Some of the stand out items to look at are:
Stock TB
Springs(maybe stock?)
Injectors, regardless of Duty Cylce, these should be stepped up.
I would assume since you had the heads flowed, you changed the valves, springs and so on. From the higher compression we would also assume you had the heads decked.
You also didn't mention anything about exhaust or cats?
If the springs are good (that is not stock), I would suggest a larger TB and bigger injectors if the exhaust can keep up.

Some not so obvious things to look at are lifters (stock?)
Pushrods touching the heads. This occurs a lot when switching to higher ratio rockers since the contact point moves closer to the fulcrum.
How high is the elevation?

Rodrigues

hes got cmotorsports springs, jet hot 1 3/4" LT headers, no cats, to a wide open borla, Comp R lifters

elevation shouldn't matter since those numbers are SAE corrected


also an msd 6al

WS Sick

I had the same problem when I built my engine, but I switched to a larger T/B and the cam your freind is using and the car woke up. Can he confirm cylender pressure?
Definately have the intake portmatched to the heads and the throttle body larger. The fuel may be running out as well.
Since his fuel injectors are not maxed out could there be some tuning issues?

Injuneer

Looks to me like its running a little lean. The wide band shows the A/F ratio climbing toward 14:1 at the top end, and its never below 13:1.

Was it done on a Dynojet?

Serene

Yes it was done on a dynojet

TheBlur

dayyyyyyyyy oooooo

m0nk

Sounds similar to what happened to my car, the power peaked at 4800, instead of 5800. After that the car just seemed to bog down. I talked to madwolf about it, and he sent me a new tune, and it really woke the car up. It felt like at least 50 hp extra, probably more than that, but I dont have any dyno runs. Try having someone look at your tune, even if thats not the problem im sure ull get a few extra hp out of it

SS MPSTR

It's all in the correct combination. IMO, the TB and intake are not hurting that to the degree that you think. The tuning may need to be addressed, but you need data logs to properly diagnose tuning issues. The heads/cam combo may be suspect in this case as well as the tuning.

Serene

I have some datamaster logs of WOT runs on the street of the car if someone can host them

ltlhomer

I can't host em but maybe rodrigues could.

m0nk

Ill host them for you, email them to me and ill throw em up on my web server, my internet was down all day yesterday but hopefully it will stay up long enough for people to help you out

Serene

Sent you an email m0nk

m0nk

http://m0nk.sytes.net/images/wot383.uni

the link works locally, tell me if anyone has problems, it should work thou