Fuel pressure at rail after engine off?

[OhioC5]

I was reading another guys thread, but didn't want to hijack. I installed used 36lb injectors and recently a new TT chip. Long story about chip selections. My car appears to either have a lean condition or faulty 02 sensor, maybe both. My 02 reading never makes it to 750 at WOT, I have added 20% fuel and had to back timing off 1.4* in all gears due to KR at 16lbs boost. I have no KR now, but can just tell the car is falling on its face at WOT. So, I installed an accufab FPR and set FP to 43# vac off at idle. I shut the car off and noticed the FP dropping off, this seemed odd but didn't really strike a cord until I read anothers thread.

Finally brings me to my question. How long should the rail maintain how much FP? The car feels much stronger at part throttle than WOT, strange. I've been told I need an ALKY kit and agree. There must be another issue somewhere. I'm not sure if I'm just expecting too much as far as performance. This is the first V6 turbo car I have ever owned by the way.

Don't get me wrong, the car doesn't run bad. Adding 20% fuel and still lacking enough fuel has me baffled. 36lb injectors should be plenty for factory turbo and internals, correct? I ran 36lb injectors on my mid 11 sec C5, it was naturally aspirated but had ported heads, cam and the injectors were at 75-80% duty cycle if I remember correctly.

I know I'm typing a lot, but need some ideas on things to look for. Really feeling I need some logging software, but need to try to stay married. Bought the car a few months ago and have spent about $2500.00 on it to date.

My wife has been really nice about everything, but the UPS guy is at my house so much I'm listing him as a dependent on my tax return.

 

[Chuck Leeper]

Check the fuel psi @ WOT. Should hold at base psi+boost.
The "stronger at part throttle vs WOT," could be you are running out of fuel. [Thus the low O2 readings.]
If you will post the data off a scan tool, there are "gurus" that can help diagnose the issue.
As for FP drop at engine off, that could be a leaky inj, check valve in the fuel pump....

 

[Pronto]

On the Scan Master, check the CCs. They should be climbing steadily while driving around. If the numbers are slow changing or stuck at one the O2s are getting flakey.

 

[OhioC5]

The fuel pressure is at 39# vac line on and climbs to 56#'s at 16lbs of boost. Posted this over on TT's web site and he believes I may have a bad MAF. I asked my wife to look at the scanmaster while I was at WOT. She said AF went to 216 at WOT Guess thats kind of low. I forgot to look at the CC's, actually by the time I got out in the car I forgot what you said to look at. I'll check them next, thanks.

 

[OhioC5]

On the Scan Master, check the CCs. They should be climbing steadily while driving around. If the numbers are slow changing or stuck at one the O2s are getting flakey.

Ok, I checked the CC number and it didn't move from 220 the entire time.

 

[Pronto]

If it didn't move around while driving normal it's time to change it. Guess the AC Delco's are not the best anymore. Denso's seem to be popular and I think they are cheaper too.

 

[Royal-T-Ltd]

on a side note----> tuning with a narrow band O2 just plain out sucks... the magic number of 750-800mv is worthless IMO... i remember tuning for 780mv and putting it on a dyno years ago, where they attached a WBO2 to it... i was somewhere around 9:1 AFR which is PIG RICH....... you definitely need to replace your narrowband if the cross counts are not cycling as it should... but to tune...YOU NEED TO INVEST IN A WBO2

 

[Pronto]

I agree but I guess it depends on what you want to do with your car.

 

[OhioC5]

I agree with buying a wideband, there are no less than 10 WB set up's saved in "my e-bay" I'm looking at buying. I had the PLX set up on my Corvette and loved it. It's not the most popular one, but kind of idiot proof. I tuned my vette to 11.80 with a PLX and HP Tuners.

 

[Pronto]

We're getting ready to use Eric's AEM wb. Not bad at $180.

 

[OhioC5]

Yes, the AEM is the other one I'm looking at buying. I found them for as low as 174.00 with free shipping. seems like a pretty good deal.

 

[Royal-T-Ltd]

yeah ive heard a lot of good things about the PLX.... i have a Innovate and works fine.... i just hate the preheat.... i've heard you dont have to preheat the PLX.... dunno about the AEM....