135 % low trim?

[93laserAWD]

Been tuning my new setup for about the last month. Run's 15 psi perfectly. The last few days while driving my idle was being a bit "awkward" I hooked up my logger and saw that my low trim was at 135 %. I went to my SAFC II and started to adjust my low settings. My fuel trim would even out at around 100% only when i added almost +10% on the 1000, 2000 rpm settings. I have 650's. Mods in profile are up to date. Also, as i added fuel, my idle shot up, but fuel trim looked good WTF

 

[95blackGsTurbo]

Adding more fuel is gonna up your idle. 650's are hard to tune with an SAFC because of the lack of compensation a SAFC allows. As always check for leaks around the throttle body and piping. Should be the first thing you do. With 650's you should be around -36% at idle since that's how much bigger they are than stock. You are getting unmetered air from somewhere.

 

[93laserAWD]

boost leak tested yielded one result. but very minimal. at the BOV gasket. Im stumped. I had my original setting at around -28 at the 1000 rpm point, but like i said before, i must actually ADD fuel to get my trim right. maybe a bad 02? any suggestions, im stumped


* Im gonna check all the vacuum lines tonight after class! maybe that could be the problem??

 

[95blackGsTurbo]

Vacuum lines could cause that or an o2 sensor.

 

[93laserAWD]

looks like the O2 signal wire is spliced for that stupid air/fuel light show, you think that ruined my O2 sensor? this could be causing my high low trim??

 

[Matrixhunter]

I have an identical problem only imagine this i had to add +17 for stock 450's !!!!!! at 1000rpm that is pure ridiculus with a brand spankin new mitsu o2. I boost leak tested the entire system and found that there are absolutely no leaks anywhere however i found the big ones on the throttle body itself. The shaft seals and the bis screw and the air rushes out quite fast from those two spots. Going to fix it tommorow and i'll post the result.

 

[Matrixhunter]

Another thing i'm going to check and you should also is base fuel pressure i'm guessing mine must be of for some reason also.

 

[93laserAWD]

fuel pressure is 37 psi.. i guess i will try the new o2 sensor.. car pulls damn good its just the idle sucks right now!!

 

[eclipse_guy]

Have you tested the coolant temp sensor for the ECU?

This will have an affect on the fuel trims. Although the ecu should be in closed loop operation so the ecu will look at all sensor values to juge where it think the proper a/f ratio should be.

 

[dsm-onster]

Have you tested the coolant temp sensor for the ECU?

This will have an affect on the fuel trims. Although the ecu should be in closed loop operation so the ecu will look at all sensor values to juge where it think the proper a/f ratio should be.

No. if the coolant temp is at proper operating temp, the ecu begins looking at the closed loop system of sensors to function in closed loop properly (o2, maf, Intake Temp, Baro). If the temp is reading lower than around 180 degrees (i believe), then the ecu will not update fuel trims. So his low trim would not go up or down. if the coolant tem sensor is disconnected or broken, then the car would not start.

A minor boost leak can be a major vacuum leak at idle and "steady state" driving. a major vacuum leak would throw low trims out of wack. You should have ran a boost leak test and fixed everything you saw before muffing w/ your safc. But that's ok. You can always put it back.

Also, if there is an exhaust leak close to or before the o2 sensor (like at the o2 housing, turbo-manifold, manifold-head), then your o2 sensor will throw your low trim off mark. Usually raising it.

Also, monkeying w/ the o2 sensor signal wires can alter the signal voltage and thus change the trims. But usually this affects ALL the trims.

 

[dsm-onster]

Been tuning my new setup for about the last month. Run's 15 psi perfectly. The last few days while driving my idle was being a bit "awkward" I hooked up my logger and saw that my low trim was at 135 %. I went to my SAFC II and started to adjust my low settings. My fuel trim would even out at around 100% only when i added almost +10% on the 1000, 2000 rpm settings. I have 650's. Mods in profile are up to date.

Wait, did you finish your closed loop tune and run around looking at your logger for a few days? I usually drive it about a week (350 miles), when I monkey w/ closed loop fuel and airflow. The trims may start out rich then slowly begin to even out but your tune may send them right over to the lean if logging for several hundred miles. Updating rates are usually anoyingly slow.

My PTE 650/660/680s had SIGNIFICANT deadtime. Thus, i got the trims lined up real quick then over the course of the week, my low trim just went wide lean. The only way to counter dead time w/ a piggy back style controller is to richen up (or do less offset) at low rpms.

Still, a suddenly rough idle indicates that your minor boost leak is causing more harm than it would suggest.

Also, as i added fuel, my idle shot up, but fuel trim looked good WTF

This smacks of a post-throttlebody leak.

 

[Matrixhunter]

turns out the boost leak on my throttle is a major vacuum leak at idle and cruise vacuum at idle is no more than -15 and at cruise when i let off throttle vacuum jumps to -21 almost. Would that indicate that it is sucking unmetered air in?

 

[dsm-onster]

turns out the boost leak on my throttle is a major vacuum leak at idle and cruise vacuum at idle is no more than -15 and at cruise when i let off throttle vacuum jumps to -21 almost. Would that indicate that it is sucking unmetered air in?

15 inches idle vacuum indicates big vacuum leak or a severely worn out motor.

The leak at the TB being the culprit goes along w/ your symptom of 'adding fuel and the rpms went up'. Leaks at or after the TB do this.

 

[Matrixhunter]

Brand new Engine Jdm with less than 50,000km amazing compression. Thats why i ruled out the Throttlebody.

 

[dsm-onster]

Brand new Engine Jdm with less than 50,000km amazing compression. Thats why i ruled out the Throttlebody.

that's ok. You know a BIG leak in the intake manifold or after the throttleplate will yield higher compression test results. So will running a compression check w/ no intake manifold. I had a blown intake manifold gasket and when I replaced the gasket the compression test results went down 10 psi.

BTW, do all compression checks w/ intercooler piping removed and throttle plate open and engine warm.