We (Myself and Mattback) built a car for a customer that wanted 500whp. Specs are as follows:
CP Pistons 9.0:1 CR
Stock Rods w/ ARP rod bolts
HKS 264 Step 2's
Greddy Intake Manifold
Garrett GT3040R Turbo
ROM tune - Z32 MAF, 96# injectors
JGS Tools Log Manifold
When we took it to the dyno for tuning all we could get out of the car at the wastegate pressure of 12.8 psi (0.9 kg/cm^2) was 300whp. I tried different AFR's and timing values but they yeilded no change. The setup simply would not make more than 300whp @ 12.8 psi. This was a problem becasue I knew that we werent going to get to 500whp without running stupid boost...which i didnt want to do. So after alot of head scratching and a few beers to help cope with the disappointment Matt and I compiled a list of everything that was different between this car and my car when it was running a nearly identical setup and making 340hp @ 10 psi.
This is what we came up with:
1) Log manifold vs. Full Race manifold.
2) ROM tune with MAF vs. Haltech on MAP.
At which point we looked across the garage to my car which is currently out of commission and decided we needed to try swapping manifolds. A call to the customer to discuss the situation...and he agreed it was the correct course of action. So the test was on!!
Matt and I worked dilligently friday night after work to get the manifold swapped over. We used my old downpipe and hot pipe of my car. These pieces were nearly identical to the downpipe and hotpipe that were on with the log...just slightly different fitments. We got it up and running, celebrated at Hooters for a late dinner...then headed off to the dyno on saturday morning. I was expeciting to see gains but we were unsure of how much. On satuday morning we ran the car at wastegate pressure (12.8 psi) and after a bit of tuning to get the new setup dialed in we saw the following gains:
All i can say is WOW...60whp and 35ft-lbs. Spoolup was almost identical with the Full Race hitting maybe 100 rpm later. I was completely floored by the results of this test. I was expecting 30-40hp maybe...but 60hp. I was totally shocked.
I think this also disproves the myth that MAF sensors are a restriction. this car made exactly what my setup made at 12 psi with a MAP sensor based system.
The truth of the matter is the flow properties of the LOG manifold are terrible. The flow from 1,2 and 3,4 directly oppose each other then are forced to do a hard 90 deg turn to enter the turbine housing. A basic understanding of fluid dynamics will tell you this is terrible for flow. The smooth transistions of the full race manifold make all the difference allowing the car to make more power even during spoolup!!
Thumbs up to the guys at Full Race
for making such a quality product!!
Oh...and the car did 507whp @ 25 psi later that day!!