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Discussion Starter #1
Vehicle: 2012 STi
Previous mods:
Grimmspeed CAI
Grimmspeed lightweight crank pulley
Invidia catted DP
Grimmspeed EBCS
Fuel pressure regulator kit (cobb style)
Killer B holy header w/ uppipe
Invidia Q300
Aeromotive Stealth 325 fuel pump

With the above mods the car ran and idled fine.

I recently added and was tuned for IAG TGV deletes, ID 1050x injectors, tomei turbo inlet, ETS TMIC and IAG competition series AOS to my 2012 STi. The vehicle was smoke tested after the install was completed and there was no leaks found.

The car runs/idles ok when its warmed up however, upon cold start (coolant temp below 140f) the engine idles at 1500rpm and if the gas pedal is blipped (say to move the car around on the driveway after 15-30secs of idling) the idle fluctuates once the gas pedal is released. If left untouched until the engine is warm there is no problem though. The issue is the idle will go between ~2000rpm and try to drop ~1000rpm. The engine will feel like its going to stall then bring itself back to what I guess it deems to be an acceptable idle rpm. It will repeat that cycle 2-3 times prior to settling back at ~1500rpm.

I'm kind of at a loss here because I recently had a friend who is stg2 (ots map) try to see if his vehicle (2013 wrx) will experience the erratic idle upon cold start once he blips his gas pedal and it did not.

I have an appointment to smoke test the car once more and to double check the install. Then I'm going back to my tuner to see if he can revise the map.

Has anyone else experienced this after adding TGV deletes/injectors? Is this a mechanical issue or something more related to the tune? I'm trying to figure out if I should just remove the TGV deletes/injectors and swap back to stock TGV's/injectors to rid myself of the issue or not. Is this just the nature of TGV deletes & larger injectors? I know for certain that previously my car did not experience these cold start idle fluctuations.
 

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Discussion Starter #5 (Edited)
Sounds like a tuning issue. Should be a fairly easy fix.

Additionally, If you have an air compressor, you can make your own boost leak tester for under $5 and just do it at home.
Just for my own knowledge, what needs to be revised? At first I was thinking the issue stemmed from TGV deletes or potentially the injectors. Ideally, there should be no reason the car doesn't behave like it did with the stock tgv's and injectors? To resolve the issue, I'm guessing the tuner would need to see the vehicle at or near cold start conditions (70-130F coolant temps) or is this something easily scaled while the engine is at operating temps?

The mechanical side I have a little more knowledge, the tuning side not so much - I think you and your tuner kind are wizards. :lol:

Thanks again for the insight, Jason. :)
 

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It may need several after-start tables corrected. One of the issues based on what you describe is that the ECU is seeing an AFR fairly far off from what it's looking for and trying to correct... over-correct, back and forth.

Stock TGV's help atomize cold fuel into the cold air. Removing them will naturally make a cold start harder. If the tuner who dialed in the ID1050x's is even remotely decent, the injectors are not the problem.

Additionally, the tuner should already have an idea of the issue and fix and be able to send you maps to correct. ID1050x's, TGV deletes, and gasoline really shouldn't have this sort of issue as it doesn't take a whole lot to get right. Once you add E85 to the mix, then the work has to be put in on making it cold start nicely. It gets even more difficult when you do the KStech TGV route and leave the dividers in place... Like I have.
 

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Discussion Starter #7
It may need several after-start tables corrected. One of the issues based on what you describe is that the ECU is seeing an AFR fairly far off from what it's looking for and trying to correct... over-correct, back and forth.

Stock TGV's help atomize cold fuel into the cold air. Removing them will naturally make a cold start harder. If the tuner who dialed in the ID1050x's is even remotely decent, the injectors are not the problem.

Additionally, the tuner should already have an idea of the issue and fix and be able to send you maps to correct. ID1050x's, TGV deletes, and gasoline really shouldn't have this sort of issue as it doesn't take a whole lot to get right. Once you add E85 to the mix, then the work has to be put in on making it cold start nicely. It gets even more difficult when you do the KStech TGV route and leave the dividers in place... Like I have.
Much appreciated and thanks for letting me pick your brain on this! :tup:

For a good while there I was thinking of dropping the TGV deletes/injectors because I had a notion that it was just a nature of the beast situation with the both of them. Fingers crossed, its as easily rectifiable as you say.

I'll update the thread with the outcome/cause to help others in the future after everything is said and done.
 

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Discussion Starter #9
So the tuner tried a couple things. Its been reduced but not totally eliminated. IIRC he mentioned something about my fuel pump dipping to 33% so they tried up'ing it to 100%. I think I'm going to just drop the TGV deletes and call it a day. The power increase over previous mods is not worth the headache at this point. Although, the cars driveability when warm is and has always been fantastic, it just the cold starts that drive me up the wall. :lol:
 

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Discussion Starter #10
Who did your tune? I am looking at doing the same mods next year and I'm in the GTA area.
Andy @ Neetronics tuned me. You do have a wide variety of options though, touge tuning and definitive tuning are some of the others I am familiar with. I've only dealt with Neetronics though.
 

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Kind of going to piggyback off of this.
2005 STI:
Catless DP, intake, ID 1000s, Walboro 255 fuel pump (or whatever the most popular number is now), IAG TGV deletes, Aeromotive FPR. Got the injectors and TGV deletes installed and on a cold start the car's idle will dip twice. During this dip, it drops below 1000RPM and the car leans out completely, according to the wideband gauge. Also shakes a bit as the idle drops. It does this twice, back to back (RPM dip, then rise, then dip, then rise) and then idles fine, like clockwork. On a warm start there is no issue at all.

Is this a tuning issue or the classic "hunting idle" that can come with TGV deletes?
 

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Discussion Starter #16
Issue Resolved. Jason, blurred & jsr you were all right it was directly related to the tune. Had it gone over from scratch by a new tuner with some fresh eyes (Justin @ Definitive Tuning).

Thanks to everyone who helped and provided some insight it was greatly appreciated. :)
 

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Just realized I'm having the same issue. I've gotten use to it, is there any long term harm with the car doing this at start up? Same deal as previously hunts for idle for about a few seconds then is fine. I don't know if I want to go back to the previous tuner to get it corrected. Already had multiple issues in the past and not sure if it's worth hiring someone else to retune the car.
 

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Discussion Starter #18
Just realized I'm having the same issue. I've gotten use to it, is there any long term harm with the car doing this at start up? Same deal as previously hunts for idle for about a few seconds then is fine. I don't know if I want to go back to the previous tuner to get it corrected. Already had multiple issues in the past and not sure if it's worth hiring someone else to retune the car.
My tuner said there is no detriment to result from it. Perhaps all you need is a fresh set of eyes on it. Mine does it still but very slightly, meaning over a much smaller rpm band range (~300rpm) as opposed to ~1000-1200rpm. Everything else looks bang on otherwise but I will keep a close eye on it when temps drop below zero.
 

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I wouldnt delete the Tumble generator valves on a daily driven car that sees a cold start up every morning. The uneven mixture distribution without them is going to cause driveability issues until the intake heats up enough to correct the mixture to the combustion chamber, you can also get wet fuel in the intake until it warms up enough to vaporise properly and that can lead to increased cylinder wear from being overly rich. The tune is just going to modify the mixture when cold, it still wont prevent the type of potential wear when cold that I am talking about and as you stated the TGV's arent restriction airflow enough to be worth removing unless your shooting for 800 horsepower or something and every possible minute restriction eliminated is the goal.....if you live in a climate that is cold I wouldnt bother removing them, but since you already did it and the tuner is not able to eliminate the driveability issue 100% you might want to put them back and gain power from a different mod or as others are suggesting try a different tuner and see if they can smooth it out when cold.
 

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Kind of going to piggyback off of this.
2005 STI:
Catless DP, intake, ID 1000s, Walboro 255 fuel pump (or whatever the most popular number is now), IAG TGV deletes, Aeromotive FPR. Got the injectors and TGV deletes installed and on a cold start the car's idle will dip twice. During this dip, it drops below 1000RPM and the car leans out completely, according to the wideband gauge. Also shakes a bit as the idle drops. It does this twice, back to back (RPM dip, then rise, then dip, then rise) and then idles fine, like clockwork. On a warm start there is no issue at all.

Is this a tuning issue or the classic "hunting idle" that can come with TGV deletes?
others with tuning experience can chime in but removing the TGV's is going to cause a rich condition when the engine is cold on first start up each day, especially in cold weather, the A/F guage is reading lean because the computer is trying to compensate for the wet fuel(too rich) that is present due to the poor mixture distribution to the cylinders with the TGV's gone.
 
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