Power Loss Top end

[duke52]

Hey guys, here’s the problem. The car pulls hard at 3.5 to 5.8k around 6k it peters off and feels almost like I’m loosing timing.

I’m running a data logger and the timing seems to be were it should be (18deg) at 6.5-7k and the egts are around 14k Fahrenheit.

I’m running an ADFX front mount (good size core 2.5" mandrel short route piping) br20g, hks 40mm wg, ported exhaust mani, 2.5" to 3" down pipe with waste gate recirc'd, turbo xs bov recirc'd, 780cc inj, sx afpr, safc, 255 fp, 6 bolt block with je's, stock 1g head and cams. nt 92 tb. magenecore wires, I’m sure I’m forgetting something

Anyways I’m running a stock unported o2 housing... could this be my problem? I’m running 25psi right now, I’ve tried more boost and less and seem to get the same feeling up high no matter where the setting is. I've got an appointment for a friend of mine's chassis dyno in two weeks but would like to have the car running decent before I get there to get the most out of the dyno time

sorry for the ridiculously long post

Thanks in advance!!

 

[PaleDSM]

Log your airflow and see where it starts to die off. It could tell you if there is a bottle neck in your system somewhere.

 

[duke52]

i'll try that tonight, should the numbers remain consistant or should they continue to go up with rpm?

 

[pboglio]

i'll try that tonight, should the numbers remain consistant or should they continue to go up with rpm?

My T28 airflow levels out at 5250 rpm or so. The 20g logs I've seen have the airflow level out at 6000 rpm or so on high boost. 50 trims I've seen carry on to 6500-6750 rpm before the airflow stops rising with engine rpm. Post at what engine rpm your airflow stops climbing with engine rpm. Stock cams are not helping you though.

 

[duke52]

i know the cams are hurting me, i am waiting to have head port work done before i swap for hks's, is it worth just getting the cams and putting the head work off for now though?

 

[1G/TS-ituner]

Not if your still running on stock valves and springs, if it were me i would send the head out for some P&P then reassemble the head with new valves, springs, ext. putting in the cams now would help a bit, but it's a 1st gen head, forcing the valves and springs to go more than they are used to at that high an rpm might cause some serious probs that i wouldent want to risk....that and you will have to take the head apart anyway later on so i dont think it's worth it

just as an outside perspective

 

[pboglio]

i know the cams are hurting me, i am waiting to have head port work done before i swap for hks's, is it worth just getting the cams and putting the head work off for now though?

If you promise not to rev beyond 7500 rpm or so, do the cams first, you'll thank me later.
I've run it up to 8000 rpm and the car was still pulling half way decently. If you plan on 8500 rpm then you might as well freshen up the head, upgrade the ENTIRE valvetrain along with the cams. Cams make a BIG difference in the 5500-7000 rpm range.

 

[duke52]

If you promise not to rev beyond 7500 rpm or so, do the cams first, you'll thank me later.
I've run it up to 8000 rpm and the car was still pulling half way decently. If you plan on 8500 rpm then you might as well freshen up the head, upgrade the ENTIRE valvetrain along with the cams. Cams make a BIG difference in the 5500-7000 rpm range.

Hahaha I promise,... Thanks man! I'll put that at the top of list for this winters mods.