Lizo7

iTrader: (11)

Setup -

91 FC
E6X Running one of Hitman's 550/1600cc basemaps, changed drastically on fuel side, timing untouched.
550/1600
HKS .84 P Trim Hot/Precision GT40 Cold
on HKS log mani and 50mm gate

The problem here is that I was running a non-turbo RB catback with a 2.5 downpipe, and the car ran awesome throughout the rpm range, but obviously being held back.

I installed a 3in straight through exhaust, and greddy FMIC and afterwards the problem started.

The situation is anywhere under about 3.6krpm if I hit the throttle more than 25% mani pressure rips to atmospheric then stops and the car feels noticably slower as the gauge reads 1psi.....2psi.....3psi.....4psi as the rpms climb but hesitantly, almost as soon as the tach reads about 3.6k-3.7krpms the boost gauge reads 15psi (wastegate limited) almost instantly and the car just hauls.

I've messed with the fuel, till all the way through this scenario my AFR's are 11.1-11.3 with the occasional varying to 10.9 or 11.5ish but still pretty close most of the way, with no change nearly.

One thing I noticed in the map, after like 4k the timing is basically the same 28 degrees at 0psi, tapering to 9 degrees at about 15psi. I don't want to mess with the timing too much since I only know the basics of it. But i did make a new map based off mine changing the timing pre-4krpm to the timing after 4k where it runs awesome...once again no change so I switched straight back.

I have a tune date set with Dave at KDR in a few weeks but I really want as much as input on this as I can get so if it's something I can fix now rather than waste time on the dyno screwing with stuff, I'd like to get it done.

I'm thinking a few things like staging bar, throttle pumps maybe, but I'm stumped so any help is much appreciated.

Matt

Nige

At a guess you've never had a big turbo before, spooling at 3600 sounds pretty good to me on a GT40.

Lizo7

iTrader: (11)

Its just a GT40 compressor wheel and housing, turbine side is relatively small. Before I had the 3in exhaust and FMIC on I was rocking a non-turbo RB exhaust with a 2.5DP and an HKS top mount If I punched it at 2500rpm i would see 15psi by 2800, and my full boost which at the time was about 24psi at around 3400rpm tops.

This is more like it hits a wall as soon as I hit atmospheric pressure, and just hesitates as it slowly builds pressure and rises in rpm's even though afr's are mint, then at 3600ish that wall dissapears and it runs as it should.

I want to start messing the throttle pumps but I can't find a definitive way to do it, every thread just says play with it till its right

drifting in drifting

iTrader: (11)

At the lower psi i think you could stand to be alittle leaner should help with responce