Losing Boost

[myblk32v]

Ok so I put my BAP, SCT2600 and 63lb injectors in on Friday and put her on the Dyno and I am having some issues. At about 4k RPMS the boost drops from ~13.5lbs to 10lbs and I'm not sure whats going on. There is no belt slip and I read about it maybe being that I need to do the Boost Bypass Mod but I checked and that has already been done. From doing some searching on here it seems like it could just be the factory non ported Eaton bleeding boost with age? Which i also read means that if I was to have it ported that would maybe solve the issues? Could someone explain this to me. It has 64k miles on it and has had a 2.76 for I'm not sure how long, at least 2 years as that's when the original owner gave me a Dyno sheet from. I will include a the engine specific Mod list and the Dyno sheet, any help would be appreciated.

2.76
Stock Lower
Metco Idlers
KB SBTB
Billetflow Inlet
JLT CAI
SCT2600
63lb Injectors
KB BAP w/wiring upgrade
Afco H/E
BBK o/r X/Bassani CB

 

[Shadow Grey 03]

Your torque is what is going down starting at around 4K. Not an issue. Stock eatons will drop some boost up top as well.

 

[myblk32v]

So no issues with the psi loss at 4k. I only was worried as it made 20 less hp and 25 less tq than when it was last dyno'd which was before sbtb inlet jlt BAP injectors and maf...

 

[moot09]

That isn't normal boost drop off. I had the SAME issue before I decided to rebuild the motor. I had a stock fuel system though.

I have a 2.8 (12.5-13lbs) and would drain to 10.5 right around 4500. I had compression issue though. I ran a 10lb pulley for most of the cars life and never had this issue.

Has the blower been off recently?

 

[myblk32v]

Blower has not been off since I've owned it. The inlet was off to do the injectors Friday but that's it. Could compression issues cause the boos drop off?

 

[Anabolic]

did you make sure ther gaskets were there?

 

[myblk32v]

did you make sure ther gaskets were there?

On the inlet?

 

[moot09]

It could, you would normally be forcing 13lbs of air into the engine but if your losing compression from failing rings, cylinder pressure is being lost.

Dont want to scare you or anything, but it would be wise to not overlook it.

Like mention, you could be losing boost through a possible bad gasket in between the inlet and the blower. I would check all of your gaskets first.

 

[myblk32v]

It could, you would normally be forcing 13lbs of air into the engine but if your losing compression from failing rings, cylinder pressure is being lost.

Dont want to scare you or anything, but it would be wise to not overlook it.

Like mention, you could be losing boost through a possible bad gasket in between the inlet and the blower. I would check all of your gaskets first.

Thank you sir. Ill check into that. Maybe have her compression tested just to be safe.

 

[04SVTCobra]

I had the same problem a few years back. I did all the mods you did to fix problem. But even after the ported eaton the problem was still there. Then I remembered that I had installed a differential brace before all the mods and for some reason the cover didn't seal right. It kept leaking. I thought maybe the ring and pinion were damaged due to lack of oil. I had the ring and pinion replaced and problem went away!