PTE 550 Tuning issues

**TKIs** · 02-26-2014, 04:07 PM

Hey everyone. I'm having some problems getting my PTE 550cc injectors working properly. The car randomly goes lean at idle and back to the normal range. It also goes lean when starting to move when its cold. Also, it was hard to start at first hot or cold. I managed to get the cold start issue fixed by lowering the cranking IPW values in startup but hot starts still take forever. I wasn't sure if I should even have to mess with the startup tables. From the way I understood it from Greg's Technical manual it shouldn't be needed for only having 550's. Am I wrong on this?

The thing I'm really confused about is injector size. I have it set to 550 (554) in chrome, but I read that they don't flow that much. I've read 525, 510 and 490 something in different places. Ive also read that only the high impedance injectors have that issue. Can someone please clarify this for me and give me a good starting point?

I got the injector latency here on the forum

1.63ms @ 8.7v
1.00ms @ 10.4v
0.80ms @ 12.2v
0.70ms @ 13.9v
0.60ms @ 15.6v
0.56ms @ 17.4v
0.56ms @ 19.1v
0.53ms @ 20.9v

The fuel pressure is 45 with vac and 55 without.

The car is a 92 VR4. Rebuilt about 30k ago and the throttle body is a rebuilt one from April just last month. The FPR is a new stock one. The fuel pump is a Walbro GSS341 installed a couple of moths ago. Not hot-wired yet. The injectors were used but I sent them out to have them cleaned and tested before I put them in. I was told they checked out fine.

I've checked for fuel leaks, vac / boost leaks and exhaust leaks and can't find any. The car ran fine before I installed the new injectors. The only issue I had was getting the low trims in the +-5 range and since I couldn't find any leaks I figured is was an injector issue. Thanks for any help in advance.

-Tom

**cobrakiller1994** · 02-26-2014, 11:06 PM

I also have PTE 550s in my car. As of right now I have them in Chrome as 535cc right now but I also haven't started tuning yet either. You are running a stock FPR with a Wally 255? Saying your fuel pressure is 55 means your overrunning the stock regulator quite a bit. Base pressure should be 43 psi. I have my latency values different the yours also. (funny thing is I did have the same values you have listed but I found another thread on here and used them instead.)

I have

10.99 V 0.810 MS
12.01 V 0.675 MS
12.96 V 0.585 MS
13.99 V 0.510 MS
15.01 V 0.405 MS

Like I said I just got my car running and haven't done any tuning minus the base tune changes flashed on so far.

**Chris@Rvengeperformance** · 02-26-2014, 11:13 PM

Do your o2 sensors cycle? Can you post a log?

**TKIs** · 02-27-2014, 03:45 PM

Thanks, I'll give this a shot and report back.

Originally Posted by cobrakiller1994

I also have PTE 550s in my car. As of right now I have them in Chrome as 535cc right now but I also haven't started tuning yet either. You are running a stock FPR with a Wally 255? Saying your fuel pressure is 55 means your overrunning the stock regulator quite a bit. Base pressure should be 43 psi. I have my latency values different the yours also. (funny thing is I did have the same values you have listed but I found another thread on here and used them instead.)

I have

10.99 V 0.810 MS
12.01 V 0.675 MS
12.96 V 0.585 MS
13.99 V 0.510 MS
15.01 V 0.405 MS

Like I said I just got my car running and haven't done any tuning minus the base tune changes flashed on so far.

**TKIs** · 02-27-2014, 04:03 PM

The o2s seem to cycle fine. Here are some logs from today. Thanks for the help.

Originally Posted by Forest Gump

Do your o2 sensors cycle? Can you post a log?

**Chris@Rvengeperformance** · 02-27-2014, 04:27 PM

Nothing jumps out at me. Are you sure the random lean spikes at idle are not a mis? Is your ignition up to date?

**TKIs** · 02-27-2014, 05:01 PM

Here's one more short log. This one shows the lean idle condition really well.

**Chris@Rvengeperformance** · 02-27-2014, 05:11 PM

It is pulling fuel on one end and adding on the other. Unplug one of the o2 sensors under the hood and make sure the correct one goes dead in the logs.

**TKIs** · 02-27-2014, 06:10 PM

I pulled the front one and it is correct. I'm not sure if this in normal or not but I did notice that there was some voltage with the o2 unplugged. 0.03904 on the front. So I unplugged the rear and it was fluctuating between 0.03904 and 0.05856. Unplugged both and they stayed at 0.03904.

The ignition coils are original to the car. Plugs and wires are about a year old.

Originally Posted by Forest Gump

It is pulling fuel on one end and adding on the other. Unplug one of the o2 sensors under the hood and make sure the correct one goes dead in the logs.