Danimal02

My 02 Z28 is currenty at a local shop getting tuned (I did the heads/cam work). My expectation was to pull somewhere near 390 at the wheels after she was tuned (I know the cam is "mild" but, still).

I get to the shop yesterday and the report shows 363rwhp and 348 max torque. Is it just me or does this seem WAY low?

Another interesting bit is that he tells me the fuel flow/pressure tails off at 5400 RPM so, my peak power is at 5350RPM (and it's evident on the dyno sheet I have in my hands). I'm thinking this thing should be pulling until 6300 and still gaining HP.

Given the mods below, what kind of power should she realistically be looking to make? Your input is greatly appreciated (as I want to make sure I don't get on the tuner's case when it really shouldn't be making anymore power).

MODS
HEADS: Stage II Patriot Heads 64cc
CAM: Comp 222/224 .566/.568 112 LSA
Lifters: Comp Hydraulic Roller Lifters
Rockers: Crane 1.8 adjustable
T-Stat: SLP 160-degree
Oil Pump: SLP high flow w/double roller timing chain
Air Intake: K&N
Exhaust: SLP LT headers/high flow cats and Borla catback exhaust

teke184

iTrader: (5)

couple questions:

1 - are those lift numbers with the 1.8 rockers?
2 - is that cam compatible with higher ratio rockers?
3 - what was your fuel pressure? a/f ratio?
4 - what kind of dyno
5 - what trans do you have? and what gear was it dynoed in?

sounds like you may have some fuel starvation up top. peak power should be near 6K

with the small cam and those heads...390 should be very atainable. something is wrong.

Danimal02

Thanks for your response...here's more info:

1. Yes, those lift #'s are with the 1.8 rockers.
2. According to Comp Cams it is compatible...
3. a/f was is 13.4
4. DynoJet
5. M6 trans

I agree, something is wrong

LS1Formula01

iTrader: (1)

Time for fuel pump and maybe some bigger injectors....

Danimal02

Why would I need bigger injectors? For this setup, aren't the stockers plenty??

killerinparadise

iTrader: (2)

I concur, sounds like a fuel problem from your description, can you post up the dyno sheet?

Danimal02

I can post the sheet but not til I get home tonight.

At 5700 RPM it peaks at 363. By the time it's at 6000 RPM the HP is down to approximately 350 (maybe a tad less). When you say "sounds like a fuel problem" are you suggesting my stock components are "failing" or simply inadequate?

slow trap

iTrader: (22)

if only pulled to 5400 rpms then 363 rwhp is pretty good but obviously you are running out of fuel. you could be lucky and put on a new filter and fix it but i would invest in a new pump/filter and pull that thing on up to 6k and you will find your power.some stock don't seem to be as strong or last as long as others. mine was fine at 513 rwhp but it was low mileage and i'm sure was maxed out but i've heard of alot of others going south way before then.

Danimal02

I hope it's not the pump...car only has 47k miles on it. I'll start with the filter and go from there

Is there any way the tuner/tune itself is the cause of this? I.e. a tuning error?

killerinparadise

iTrader: (2)

I'm not sure about tuning errors or anything as I have never tuned a car personally. I don't think it would be your fuel pump though because all the ones that I have seen fail normally just die it's not like you can still run on it, it's usually just kaput kaput uummphh and it wont start again, did he say what your injector duty cycle was at or the fuel pressure? I to would recommend checking the filter and then the injectors, maybe your injectors aren't seated correctly. I would also check your MAF sensor, I had a dirty one when I first put my car on the dyno and it wasn't dumping enough fuel because it couldn't get an accurate reading the only pull I did it with like that pulled 260hp with catback & lid , but the A/F was at or greater than 17:1, a $6 can of MAF cleaner saved me from replacing injectors, fuel pump and chasing dead ends.

Danimal02

Killer, good suggestions. I will personally check the injectors to make sure I seated them properly (and replace the filter). I was not provided w/any duty cycle data...I'm guessing this wasn't checked.

The MAF is clean, I cleaned it before I put it back in.

BeemerZ28

iTrader: (5)

I was told that when I do my heads and cam to go ahead and step up too 30# injectors at least. something like the SVO 30#er. My came will almost be the exact same as yours too.

Rick @ Synergy was the one that recommended this, as he will be tuning my car when I get it done.

teke184

iTrader: (5)

the injectors should be able to handle 400hp give or take....

isn't 13.4 a bit high? shouldn't ti be more like 13.0

still sounds like fuel starvation from either the pump, the lines or the injectors

Danimal02

I am taking it to another shop as I have a stupid feeling there's nothing wrong with any parts on the car. At worst, I'll be proven wrong in which case, I'll have to buy more parts.

...I still think there is a disconnect between the tuner and the keyboard