Very Weird Tuning Problem!!

[Largekid]

alrighty, well we finished the tune yesterday... I was running 32* at full boost There is one spot that we cant get to lean out at all. Its whenever i'm not on the throttle, or barely on it to keep speed. Any RPM, any load. Its reading 10:1 on the AEM. As soon as I get on the throttle to power past it, it goes back to where it should be. All the cells that we are hitting, and around it have had the fuel taken out as far as they will go (.500 iirc). We did a boost leak test, no boost leak at all. What could be causing the problem? Here is a pic of my MAF readings (top), RPM (middle), and bottom is TPS. What do you guys think the problem could be???

edit: guess i could add the pic

[WhatsADSM]

32* of timing is way to much under full boost. Unless maybe your full boost is like 8psi and you are running C16.

IMO fix that, and if you still need that kind of timing to make it go anywhere then you need to check your base timing (Configure->ECU Setup->Set Ignition timing) and make sure that you are using a timing light on the high tension lead not a low tension lead such as the loop back black wire.

As for the AFRs at cruise.

First off are you running O2 feedback?Next you really need to see what trims are effecting your fuel pulse, so open the fuel trims parameter screen and see what trims are adding the fuel. If nothing stands out then yes you will need to just lower the injector DC at the lower load levels.

[Largekid]

32* of timing is way to much under full boost. Unless maybe your full boost is like 8psi and you are running C16. IMO fix that, and if you still need that kind of timing to make it go anywhere then you need to check your base timing (Configure->ECU Setup->Set Ignition timing) and make sure that you are using a timing light on the high tension lead not a low tension lead such as the loop back black wire.

yea, i know! It was breaking up badly up top, we put it down to 24* and its doing just fine now. 22lbs and 93 octane. The car makes great power now everywhere, just trying to fix the damn super rich spot.

As for the AFRs at cruise.First off are you running O2 feedback?Next you really need to see what trims are effecting your fuel pulse, so open the fuel trims parameter screen and see what trims are adding the fuel. If nothing stands out then yes you will need to just lower the injector DC at the lower load levels.No, i'm not running O2 feedback, its a open loop system (no O2 sensors), by the fuel trim parameter, what are you talking about? the % of fuel per cell? i'll also check out teh injector DC and see where they are. Anything else??

[WhatsADSM]

The base fuel table is only that... Just a base.. There is a whole section in the fueling category for all of the fuel trims. The biggest one is the load versus % addition, which I know AEM was using in their base map for the 26. If you go under the fuel menu there should be a Total ("T" icon) for all of the various fuel trims. Keep looking.

Also IMO it is MUCH easier to think of everything in IDCs, so if you haven't already go to the main fuel map, right click on it outside of the cells and select that you want to view everything in duty cycle (as opposed to the default of pulse width)

IMO, you really should run O2 feedback.... since likely you already have a wideband. Feed the analog output from the wideband to the EMS and configure the O2 sensor. This way under cruise conditions you can use O2 feedback to watch your back and keep you in check (as a side note you can also use it under WOT )

[Largekid]

AHH, sorry I wasn't specific...it was in the other thread. I'm running a PFC w/ a AEM W/B. I probably have those options, but not labeled the same.

[silviasgp06]

wish there was a way to use the programable out on the AEM wide band with the PFC, to be viewed while in datalogit or something. there isnt right?

[Largekid]

i can record all my a/fs in the datalogit as we are tuning...there isn't a way for the PFC to record them though, if thats what you are asking

[WhatsADSM]

Ahh my mistake. I assumed you were running the AEM. Hmm.. I would still check out your maps to see if you have any fuel trims.

Another quick thing to check is your injector dead time.... sometimes called other things. This is effectively the pulse width that is added onto your base map. It is used because there is a lag between when the ECU commands the injector open and when it actually starts to open. If you have this value set to large then I could see problems in the low load cells.

[Largekid]

yea, i'm going to check that out...that was my only other thought. I was told that my MAF might be to close to my turbos inlet, so I moved it as far away as I could (~6") but i'm still having the issue. Hopefully I wont have to change my setup to a blowthru...i dont want to have to start tuning from scratch again. I'm heading to the dyno on sat for some mad tyte hp #s .....hopefully we get this issue figured out before hand.

[eh?]

Post the complete log. I think it's just hunting for idle rpm and overshooting/undershooting.

[Largekid]

Post the complete log. I think it's just hunting for idle rpm and overshooting/undershooting.

i'll see what I can do tonight. I'm not sure if we saved any logs from the "final" tune, but I know we have one from one of my lean tunes

[ItzGenX]

Post the complete log. I think it's just hunting for idle rpm and overshooting/undershooting.

That is exactly what seems to be happening. If you look, the MAF and RPM respond in the same manner on the graph as the throttle is closed. I think the IACV needs to be tuned in the ecu, or the throttle plate stopper is set all the way to closed making the IACV load cycle too much to handle. Usually the stopper screw should be set where the engine can still idle 450-500rpm without the IACV's help. The IACV could also be tuned somewhere in the PFC. It could also be through there, that the PFC is telling the IACV to open up too much at a time, bogging out the engine from a quick lean, then add fuel right after to compensate before it stalls. Adding this fuel would suddenly cause all this lean air to richen and burn causing the rpm to shoot up, then over react and close the air off and the rpm drops again. Rinse and repeat = possible hunting problem.

Edit: I also noticed on the RPM that after you let off, the RPM drops down to 450-500 before it comes back up, then begins it's hunting problem. I think you should solve this hunting idle before trying to adjust the fuel around too much. When I first did my idle tune on my Haltech, I had a hunting issue with 'rich' numbers too (11-12:1). Really, it just needed 'more' fuel and a steady idle map. After it held steady at idle, the AFR's were reading 15.5:1 even though I added fuel.

[Largekid]

That is exactly what seems to be happening. If you look, the MAF and RPM respond in the same manner on the graph as the throttle is closed. I think the IACV needs to be tuned in the ecu, or the throttle plate stopper is set all the way to closed making the IACV load cycle too much to handle. Usually the stopper screw should be set where the engine can still idle 450-500rpm without the IACV's help. The IACV could also be tuned somewhere in the PFC. It could also be through there, that the PFC is telling the IACV to open up too much at a time, bogging out the engine from a quick lean, then add fuel right after to compensate before it stalls. Adding this fuel would suddenly cause all this lean air to richen and burn causing the rpm to shoot up, then over react and close the air off and the rpm drops again. Rinse and repeat = possible hunting problem.

Edit: I also noticed on the RPM that after you let off, the RPM drops down to 450-500 before it comes back up, then begins it's hunting problem. I think you should solve this hunting idle before trying to adjust the fuel around too much. When I first did my idle tune on my Haltech, I had a hunting issue with 'rich' numbers too (11-12:1). Really, it just needed 'more' fuel and a steady idle map. After it held steady at idle, the AFR's were reading 15.5:1 even though I added fuel.

yea, it does have a slight hunting problem for sure...we fixed it by turning the injectors on earlier after we let off of the throttle. I'll see if i can get an actual log to load up, and will let him know what we have been talking about. The IACV problem sounds like it could be it for sure.