lum90

I really hope someone can help me as nobody i've spoke to over here in england seems to have a clue whats goin on

I've got a 94 FD running a large street port, garrett T04Z, PFC, 1680 secondary inj plus all other supporting mods.
I was running a GT35R but managed to throw a tip due to the vac line to the fuel pressure reg coming off halfway up the 1/4 mile so decided to change to T04Z when it was being rebuilt!
Now since the engine's been back in we've been having a wierd issue when trying to tune it. We started with the map for my GT35R and the AFR's were very rich so we had to take lots of fuel out of the map accross the whole boost map to get the AFR's down to an acceptable level?? Surely the T04Z should have required more fuel to be added over the GT35R
In the end we had to take out so much fuel the map had less fuel in than the base map yet we had perfectly safe AFR's and the car pulled well.
Aswell as this the Inj duty will not seem to go over about 60-65% i'd get about 55% duty at 2-4psi and only 60% at 14psi. I was seeing about 80% duty at 14psi with my old GT35R
The only time the inj duty ever goes over 60% is when the car is cold in the morning and you blip the throttle at a standstill and it'll hit about 70%

I really hope some one can shed some light on this cos i've not got a clue whats going on?? The engine must be getting more fuel than whats on the map somehow??
Don't wanna drive it on boost incase whatevers causing the extra fuel to be delivered suddenly stops doing it.... then it's less fuel than base map and bye bye engine!

Andy_k

Whats the base fuel pressure?
And what does it rise to when your on boost? Also do you know the reading is true?

arghx

iTrader: (3)

I would post this in the PFC section. Do you have your "before" and "after" maps? Did you do anything to your fue system at all?

Here's something that happened to me. I tuned my car on a T04S (obviously smaller than yours), threw a ton of fuel into the map, but once the boost climbed it kept leaning out. Turns out I was getting a fuel pressure drop due to a bad wiring job on the fuel pump. I redid all the fuel pump wiring and I ended up having to lean out the map significantly because I now had steady fuel pressure.

fro

something sounds very fishy. I'll pm you my email address - if you can mail me your map I'll look over it in case there's something obviously weird (but I guess you've already checked the map over?)

lum90

Base fuel pressure is set at 41psi i think? That was the first thing we checked.
I'm not sure if it's rising correctly with boost as we tuned it on the road not on a dyno, although if the pressure wasn't rising i would expect it to be leaning out under boost??
The only change to the fuel system was that i fitted a "sock/filter" to the bottom of the fuel pump (Bosch 044 fitted in tank) to help prevent fuel surge.

jantore

If ur close to Manchester u should take the car to Pip at WGT Autodevelopments.

He's a wiz with a PFC and would probably find your problem fast, and maybe save u another rebuild.

www.wgtautodevelopments.co.uk
01606 837277

Im going there the first week of May with my Bridge Port T04Z build to tune it on E85

JT

blitzboy

hmm very curious, 80 percent inj duty at 1 BAR on your original setup (GT35) with 1680 injectors is quite high, I only see 68 percent at 1 BAR at most normally 63-65 percent.
But yeah get WGT to double check the fuel system, you may have had a voltage drop at the pump in the past and now you getting full voltage, also the sock maybe giveing the pump all the fuel it needs now where as before it might have been starved.
But to be safe get WGT to double check it

lum90

Ah blitzboy.. should have known to ask you about any problems with a T04Z setup!
Fuel pump type problem seems like a logical explanation or at least the best one yet! I'm gonna be taking it out with the guy who does my tuning on wed afternoon so we're gonna get the wideband on and see what it does as i've changed the plugs leads & double checked a few things since the last time it was mapped.
I'll make sure i take a note of any relevant information (inj duty, AFR's, map details etc) and let you all take a look n see what you think.

lum90

Well we mapped it last nite to 14psi with absolutely no issues at all!
It seems whatever was up with it before has gone away since i changed plugs, leads & sorted a few wiring connections. So i'm well happy....
Now to tune it to 20psi & get on the dyno!!
Thanks for all your help guys!