Reason for power dropping off

[MX4]

Hi all,
I had the first go at the dragstrip on the weekend and did pretty terribly. The Evo Zero 3.909 ratio gearing might be partly to blame, probably as much as my shitty driving, but another issue is my 7500 RPM limit. My tuner set it there as the car stopped making power about that point. Full boost is at 5250 RPM and with the rev limit where it is it gives the car a very narrow powerband. So with the mod list below can anyone see anywhere which might be causing power to drop. One item that has crossed my mind is the intercooler. Its a 21x9x2.5" chinese style. I had the inlet and outlet changed from 2.25" to 2.5". Could this cause a drop in power up top when the turbo is really starting to pump.

Mod list is below as well as dyno graph. Any advice greatly appreciated. Cheers!

9.0:1 forged pistons
Aftermarket rods
ARP head studs
Cometic head gasket
ID1000 injectors
300lph fuel pump
Fuelab fuel filter and adjustable fuel pressure regulator
Forced Performance GT35R with 0.68 exhaust housing @ 28psi
JMF Race Inlet Manifold
Larger intercooler w/ 2.5" intercooler piping & Tial BOV
Degree'd Kelford 272 cams with dual valve springs
3" Exhaust
Standalong ECU

 

[strokin4dr]

Nevermind.... reading fail!.

 

[OldHairyBastard]

You should be able to go to 8500 RPM with that setup to keep you in good power on the up shift. I don't know why your falling off as much on the top end but lets get that RPM up higher as your cams can do it. Do you have a copy of your air/fuel and the timing map or could you get that off of your standalone on a laptop?

 

[MX4]

Yeah I will be able to. I have never downloaded the map so I will do it over the weekend and post it up.

 

[ghostinthevr4]

This is a easy one, your turbine housing is to small.

That .68ar housing is suffocating that turbo you need a .86 and higher.

 

[MX4]

Well thats not what I wanted to hear!!

 

[MX4]

Quoting ghostinthevr4:
This is a easy one, your turbine housing is to small.

That .68ar housing is suffocating that turbo you need a .86 and higher.



Not trying to argue with you here, but found this dyno chart of a 2G that also has a FP boltup 35R. His power, though not climbing, is static up to 9500RPM.

click

 

[ghostinthevr4]

No worries mate I don't see it as arguing I see it as a discussion, with what Oldhairy bastard said you should be able to rev to 8500 rpm. On my setup it pulls all the way to 8500 and the power starts to drop a little.

I'm running an 3586HTA in .86 Tial v band housing so kinda of similar setups I also have a JMF street manifold with HKS 272 built motor, you should be able to pull harder consider you have Kelfords 272's and a race manifold.

With the DSM3582 it's not really a good comparison fp has done there home work with there housing they flow really well. I had an FP3065 then went to the .86ar in the Tial v band housing. I can't remember where the power started to drop with the FP housing I was trying to look for some logs with the FP housing to compare with my Tial housing but just remembered that the logs with my FP housing was on my laptop that that got stolen when I left my door unlocked some years back. When I switched to the Tial .86ar the power sustained and kept pulling unfortunately no dyno but I had the logs, you could see an increase in HP too.

If you had ECM link you could've posted a log on the forum, a .63ar T3 and a .63 T4 housing are not going to be the same size with that said a .63 FP bolt on housing is not going to be equal to the above housings either. What's your timing look like when it starts dropping timing plays a big role in the top end if it just drops considerably expect HP an TQ to drop also, how's the afr tuned at that rpm, or your fuel pressure? It could also be the inter cooler maybe it doesn't flow that much cfm's, I have the ETS kit I believe the piping is 2.5 like yours.

There's a lot of variables but without data it's kinda hard to narrow it down I hope what I posted made some since have you asked the tuner what he thinks it could be?

 

[ghostinthevr4]

Give this article a read it basically describes how AR's effect performance.

click