ProEFI

First off this is on 91 oct pump gas.

Setup, ls7 with no forged parts in the bottom, Mast Black label 285 heads with a 2.200" intake valve and 1.600" exhaust valve, cam, d1 procharger with original procharger intercooler.

I am having an issue with power and boost falling off past 5800-6000 rpms so I will start by giving you my valvetrain details.

Cam specs, 227/242 duration @ .050 .613/.615 with 1.8 ratio rocker arms 116.0 CL

I run the car with C16 today and it's hits 700hp only was about to die at the dyno shop cause when I took the car for ride it's feels great while driving with C16 but it's not even changed I feel like the car is 580hp not more than that not sure if the dyno is reading good or not and I feel sad for it.

planning to add more boost to that D1 and lowering the compression to 9 which is will help for adding nitrous too.

Summary, I am definitely not at the limit of this procharger intercooler with iats reaching 160 at the end of a pull. Boost at 6000rpms is 7psi and falls to 4 by 6600, no belt slip. Restrictions in blower piping have been eliminated with full 3"alum pipe from blower to intercooler.

Wrong cam? Wrong springs? Right springs set up wrong? Valvefloat? I am just a few thousand rpms short of the recommended max blower speed at my redline.

This car should easily be pulling to 7k and making 700+rwhp at least (with methanol to crutch the pump gas) with some boost leaks it made 3psi and almost 530 at 6000 rpms on pump gas only. With boost leak fixed it (stock ls7 intake) it made a touch over 674 & boost hit almost 6
6 at 6000. I chalked the loss from the intake, backing off the timing to cope with,the extra hot air and pump gas. The falling on its face is what is getting me.

Chance42

IATs are 160 with meth? That's awfully high. Mine would hit around 150 with 93 and no meth on a 2.9 whipple. This was in 95 degree weather.

Are you certain there are no boost leaks or belt slip? If not I'd be looking at the valve train next.

ProEFI

not using meth yet and yes there is no boost leaks or belt sliping also I'm not sure if it's something with the valve train, what I thud is with better heads and cam it's common to see a pressure drop. With more airflow the engine should want less timing as well. Needs a different pulley setup for more boost.

Chance42

A pressure drop similar to going to long tube headers from the stock manifolds, yes.

But to lose pressure between 6k and 6600 on one of these motors with a centrifugal blower? If it isn't belt slip or a boost leak, I'd be looking for valve float or something else in the valve train.

ProEFI

I'll check if there is an agreement that agreed with you, I'll open the valve train to check everything up again. what I have been told here that it's getting an overflow cause the Heads gave her more flow so all what I need is boost to set it up all together.

Unreal

Boost goes from 7 to 4 and you say no slipping? How do you figure? Friend had a d1 on his 2005, went with one size down pulley and had the same issue. Finally had to swap to an A&A bracket and now holds 8psi. Belt was slipping like crazy with the PC setup.

99.9% this is belt slip if you are running anything smaller than the stock PC pulley. Heads won't do it, cam is fine, etc.

Unreal

Boost goes from 7 to 4 and you say no slipping? How do you figure? Friend had a d1 on his 2005, went with one size down pulley and had the same issue. Finally had to swap to an A&A bracket and now holds 8psi. Belt was slipping like crazy with the PC setup.

99.9% this is belt slip if you are running anything smaller than the stock PC pulley. Heads won't do it, cam is fine, etc.

SHovV

What are your valves made from, what springs do you have and what are their pressures?

Unreal

Unless someone royally screwed up the valve train, that isn't it. They would have to put the cam in a tooth or two off, have wait too short/long pushrods, or something seriously wrong.

edge04

how do you know you are not getting belt slip?

realcanuk

Really sounds like belt slip, and if not that I would look to pushrod length. Do a quick compression test to make sure valves are not being held slightly open at least.

breecher_7

Gonna have to agree here....

Sounds like belt slip.

As he said above, a swap to a A&A bracket will cure this issue.

Can you post some logs? Would be much easier to diagnose and know whats going on for sure if you had some.

Nasser_q8

What belt brand are you using ? still on the stock pulleys setup 6 rib ?

Unreal

Swap to an A&A bracket, 10 rib and direct drive. You will need all that later for the F1 anyways.

Or just swap to an ECS 2200R with cogged 10 rib and call it a day.

breecher_7

That about sums it up right there....

0ProChargerTech

Why would you need to swap to an A&A bracket, when lots of people run the stock ProCharger bracket with a direct drive making more power then he is.

Example 915rwhp: http://forums.corvetteforum.com/c6-f...hp-815wtq.html

Before you go spending a bunch of money that you don't need to, lets go back to the basics:

Dirty or restrictive filter?
The OEM inlet, is really designed for the stock kit, lots of people swap it for a 4" big mouth unit, with great results.
Easy test = Try doing a run without the filter on it, and see if it clears up.


HERE IS A GOOD LINK TO A CAR MAKING SIMILAR POWER, SAME BLOWER, 4" INLET: (Also stock ProCharger Bracket)
http://forums.corvetteforum.com/c6-f...uth-inlet.html


Bypass valve that is letting go?
Due to bad diaphragm or linkage or bad reference line?
Easy test = Block off Bypass valve port. Don't just unhook the vac/boost line, that will do nothing. But block off he 1" rubber tube with piece of metal if you can.


The other thing to note, is that 160 degree IAT's is pretty darn high for just a dyno pull. Either its not getting a good amount of airflow to the intercooler, or something. Lots of people use that intercooler again to much higher HP numbers that then. Possible its falling on its face, because its hitting a high IAT table in the tune, and removing a bunch of timing. (Though that doesn't explain the boost issue)

0ProChargerTech

Its amazing how common this happens, but you don't hear about it much. Or people that have cams skip time / ground incorrectly.

ProEFI

acutely I'm not sure if it's a belt slip cause everyone saw my belt said it's a good belt and ready to handle the power. thats why I said it's not the belt the car runs like a cammed Z06's nothing much I really upset with it.

ProEFI

• A fully CNC machined Mast Black Label aluminum cylinder head
• Mast nitrided & micro finished .700" Lift Dual Springs
• Mast lightweight stainless steel intake & exhaust valves
• Mast lightweight steel retainers
• Mast machined locks

Lift Intake Exhaust
0.100 76 65
0.200 163 118
0.300 245 171
0.400 307 212
0.500 350 229
0.600 379 245
0.650 388 247
0.700

ProEFI

cause the garage guys said it's not sliping. and everyone els of my friends said it's a good belt. we have tested the car it's fine until we hit the 6000 RPM boost start going down seriously.