HY35 RB25 NEO not making power?

[ArcticSIlver]

HY35 RB25 NEO not making power?

So I rebuilt a stock rb25 neo with cometic mls head gasket, arp hardware, freddy intake mani, top mount turbo mani, HY35 turbo, walboro pump, 550cc injectors, tial 38mm W/G,  running Link G4+. Got tuned today by a very good and reputable tuner, goal hp was 400whp and only made 280whp? The motor runs flawlessly, but boost was solid from just after 4k to about 6.5k and boost would fall off. He said the turbo is reaching it maximum volumetric efficiency as the AR is to small (.65) or the turbo is damaged. Now from all the research ive done I thought the HY35 was capable of 450ish hp on rb25s? Am I mistaking? Does anyone have any dyno sheets running the same turbo? Thanks - Josh

[KiwiRS4T]

Can you post up your boost curve and power curve? What are you using for boost controland how much boost are you getting? What fuel? Do you know your compression ratio or have you tested with a compression gauge? Got a decent FMIC?

[ArcticSIlver]

I will post up the dyno sheet tonight. Last night i realized i did not put the compressor o ring on. were doing a boost leak test today and if its leaking real bad ill fix that and throw it back on the dyno to see if it fixes the issue. Boost curve curvs up from about 3k to 4k then at 4k it holds 14psi flat untill about 6k then dips a couple psi to redline. He even threw in extra injector duty cycle and closed the wastegate a bit  where it starts to dip to see if it would help but nope. Boost is controlled via mac 3 port solenoid and link g4+. Fuel is 92 octane. Have not measured compression ratio but Its probably a smidgen higher than factory, stock headgasket thickness was used on the head that has been resurfaced 4-5 times and the block resurfaced once. FMIC is a good sized ebay item. I really hope its just a massive boost leak that does not show itself untill 15 psi, i had high hopes for holset, but i may end up having to go with a legit turbo, which sucks because i just paid 450$ to have a custom down pipe made.                          

[KiwiRS4T]

17 hours ago, ArcticSIlver said:

I will post up the dyno sheet tonight. Last night i realized i did not put the compressor o ring on. were doing a boost leak test today and if its leaking real bad ill fix that and throw it back on the dyno to see if it fixes the issue. Boost curve curvs up from about 3k to 4k then at 4k it holds 14psi flat untill about 6k then dips a couple psi to redline. He even threw in extra injector duty cycle and closed the wastegate a bit  where it starts to dip to see if it would help but nope. Boost is controlled via mac 3 port solenoid and link g4+. Fuel is 92 octane. Have not measured compression ratio but Its probably a smidgen higher than factory, stock headgasket thickness was used on the head that has been resurfaced 4-5 times and the block resurfaced once. FMIC is a good sized ebay item. I really hope its just a massive boost leak that does not show itself untill 15 psi, i had high hopes for holset, but i may end up having to go with a legit turbo, which sucks because i just paid 450$ to have a custom down pipe made.                          

I see people making power at 1.5 bar so you need more boost!

BTW if you google Holset HY35 manuals there are a bunch of makers manuals from Cummins.

[89CAL]

92 octane? Not in Aus?

[KiwiRS4T]

Its common to find knock off FFP with pinholes. To pressure test system make up a plug from anything - plumbing fittings or whatever you have to hand and put a tyre valve in the middle. Pull the outlet off the turbo and put the plug in the pipe and apply pressure with an air hose.