vr6 supercharged c2, idle issues when stopping

[dubber89]

so first let me start off by saying i have read countless threads and searched all over, i am a vw technician and put the car together myself.
setup::
97 12v obd2 vr6, with c2 9.4:1 head spacer
vortech v1, not sure size pulley but makes 13 psi on my boost gauge
c2 30# software with proper injectors and 95mm maf housing

the car starts and idles fine, will run great down the road , makes a healthy 10.5-11.5 during WOT passes, but when i come to say a red light the car will surge almost as if starving for fuel and the idle will go up and down for about 10 seconds until it fixes itself.

any help is greatly appreciated, i have replaced a lot of parts to try and fix this.

also planned on going stage 2 with 42# injectors , at the same boost level. any input on if that is even worth it ?

[x9t]

I am not an expert but I remember some people having issues with the MAF being to close to the supercharger.. and the way it hits it.. it would freak out the MAF.. I think the solution was to move the MAF away from the Supercharger.. move it down a bit.

JT

[dubber89]

I am not an expert but I remember some people having issues with the MAF being to close to the supercharger.. and the way it hits it.. it would freak out the MAF.. I think the solution was to move the MAF away from the Supercharger.. move it down a bit.

JT

yeah i have the maf about a foot and a half from the charger, with the cone directly on the maf. it sits down low almost near the front lip. then theres another foot length from the charger to the throttle body

[dubber89]

im just baffled i have replaced so many parts like plugs+ wires ,coilpack, 2 different MAF sensors, brand new 1.8t diverter (not installed backwards), throttle posistion sensor, even used a smoke machine to check for vacuum leaks. i even tried an inline fuel pump and it didnt make it any better so i took it back out. tried 3.0 fpr and 4.0 fpr. no idea

[youlostme21]

I'm having some crazy idle issue too, same setup.
I'm thinking air flow straighteners in the MAF housing and maybe my throttle body... need more time

[x9t]

Is your tune set up for that 95mm MAF housing size? Again.. I am jus throwing stuff out there..

I guess when installing a C2 chip.. it will not trip the computer/throw a CEL for certain things.. i wonder if you could slap on a OEM ecu so it may give you some codes..

When did the issue first happen? Did you just install something or replace something?


JT

[dubber89]

Is your tune set up for that 95mm MAF housing size? Again.. I am jus throwing stuff out there..

I guess when installing a C2 chip.. it will not trip the computer/throw a CEL for certain things.. i wonder if you could slap on a OEM ecu so it may give you some codes..

When did the issue first happen? Did you just install something or replace something?


JT

thats a great idea actually. plug in the stock ecu to check for codes. im actually embarassed that as a vw tech i didnt think to do that ! ill keep you guys posted.

[dubber89]

still no luck. at this point im sending the chip back to c2 and getting a custom tune for the headspacer that i have.

[x9t]

So C2 software should use a 4 inch MAF housing.. You have that right?


Finally, I remember some guy fixed it by buying a... air flow strainghtner.. i looks like a honey comb screen looking thing.. basically what we have on our OEM intake .. its to correct the incoming air into the MAF. I think he got it on a site for american cars.. thats all i got.

JT

[youlostme21]

These

[dubber89]

So C2 software should use a 4 inch MAF housing.. You have that right?


Finally, I remember some guy fixed it by buying a... air flow strainghtner.. i looks like a honey comb screen looking thing.. basically what we have on our OEM intake .. its to correct the incoming air into the MAF. I think he got it on a site for american cars.. thats all i got.

JT

i have the correct 4" maf with the honeycomb insert. i have had that for a while now...

[Das.Rado]

Place the MAF post supercharger/ post diverter valve..... If the diverter valve is post MAF at the moment and dumps air when slowing to a stop, the ecu sends fuel for the amount of air the MAF logged not the decreased amount of air which passes into C.C., due to the dump by the valve.

You can give this a shot i bet its the problem.

[mk3alltheway]

Place the MAF post supercharger/ post diverter valve..... If the diverter valve is post MAF at the moment and dumps air when slowing to a stop, the ecu sends fuel for the amount of air the MAF logged not the decreased amount of air which passes into C.C., due to the dump by the valve.

You can give this a shot i bet its the problem.

Arent blow thru maf's entirely different? Also I wonder what the stock maf's peg out at?!

[dubber89]

Place the MAF post supercharger/ post diverter valve..... If the diverter valve is post MAF at the moment and dumps air when slowing to a stop, the ecu sends fuel for the amount of air the MAF logged not the decreased amount of air which passes into C.C., due to the dump by the valve.

You can give this a shot i bet its the problem.

the setup i have for obd2 requires the MAF to be pre charger with the intake cone directly on it , it sits down near the front lip, the pre charge and post charge pipes have lines run off each of them which go to the diverter valve. i always knew that only to run the MAF post charger if youre not running a dv

[youlostme21]

I wonder if its your dv being to close to the MAF, since your precharger pipe is so short.

{{{{Warning- Totally theoretical, talking out my ass ahead}}}}

I wonder if putting some kind of capaciter like setup would help. Just a small tank between the DV and Intake pipe, withsome sort of foam to slow the air and let it seep in more naturally instead of blow in, disrupting flow across the MAF....

[TBT-Syncro]

the setup i have for obd2 requires the MAF to be pre charger with the intake cone directly on it , it sits down near the front lip, the pre charge and post charge pipes have lines run off each of them which go to the diverter valve. i always knew that only to run the MAF post charger if youre not running a dv

it will never run properly with the intake cone mounted right at the maf.

either change it to blow-thru, or extend the intake tube across the motor to the drivers side to get a cleaner maf signal

what you're talking about is a very very common problem.

[Kenji]

it will never run properly with the intake cone mounted right at the maf.

Really? The VF-Engineering S/C kits clamp the air filter directly onto the MAF sensor and their kits idle just fine.

[dubber89]

yeah c2 told me my setup is correct and i had this same setup on another vr and it ran great for 2 years until i spun a bearing at the track. when i swapped the kit into this car i had already rebuilt pretty much everything while i was there for this motor and this is how it ran after. im about to tear it all apart and re do it all again i have no idea what it could be . ill try and route a longer intake across the front and just see if it helps anyways.

[dubber89]

i wonder if its possible that the head spacer has something to do with it. ill get back on the phone with c2 and see if they can tune their chips to be compression specific. ill also try a stage 2 chip with the 42s injectors and see what happens

[arashfarakesh@yahoo.com]

i had idle issues to. found out they gave me the wrong tune sent it back they set me up for 30# and 4in maf. than i upgraded my fuel pressure regulator and everything is fine

[corpsman-up!]

i had this issue. it's because the maf is too close to the charger. i had the original piping that came with VF's kit that is really long and sits down near the lip. Well i sucked some water up one night and thank god it didn't mess anything up.

got a shorter intake tube and the car started stalling. if you unplug the ISV and disconnect the battery to reset the ecu then you will be ok. just sucks on cold starts that you have to have your foot on the gas for about 20 seconds or you will get a hunting idle on start up.

hope this helps you out.

[arashfarakesh@yahoo.com]

so i found out they tuned my car for 36# injectors when i have 30#. sent it back got it retuned the car runs much better than before but was slightly lean because of the other mods
so i upgraded to an adjustable fuel pressure regulator and now i just need to set it up

[VdubBry]

I know this is an old thread but did you get it all straight dubber? Mine is almost the same exact scenario, fresh motor etc etc. Get some wacky idles though.

Also at WOT, my AFR is reading in the low 13's and I think it should be more like low 12's. Im running C2 with the 42# and 4" maf, same setup with the cone filter right at the lip etc.

[C2Motorsports]

Are you guys running BOV with open dump, or DV with recirculation?

[VdubBry]

I am running a turbo smart that you can run I believe as full recirc or bov. I am not sure if that is the right thing or not. It does have a bov sound to it now and has a bunch of settings. What should we be running?

[C2Motorsports]

I am running a turbo smart that you can run I believe as full recirc or bov. I am not sure if that is the right thing or not. It does have a bov sound to it now and has a bunch of settings. What should we be running?

You need to run it as a recirculating DV...not open dump;

[VdubBry]

Ok this is one part of the system I am not familiar with. I need to look at it and figure out how to tune it to full recirc. If it is in full recirc should i not hear any whoosh sound like a bov.

Also what is the reasoning behind recirc vs bov just want to learn the technical side as in what does the dv or bov affect?

[C2Motorsports]

Ok this is one part of the system I am not familiar with. I need to look at it and figure out how to tune it to full recirc. If it is in full recirc should i not hear any whoosh sound like a bov.

Also what is the reasoning behind recirc vs bov just want to learn the technical side as in what does the dv or bov affect?

you will NOT hear a pronounced WHOOSH, but you may hear a muffled version....hard for me to qualify this over email

The reason is you do not want to lose metered air overboard when using a MAF based car.....

[VdubBry]

you will NOT hear a pronounced WHOOSH, but you may hear a muffled version....hard for me to qualify this over email

The reason is you do not want to lose metered air overboard when using a MAF based car.....

Ok thanks that makes sense. So this may affect the idle etc. How about the issue when she sits overnight, when I start in the morning, can't even tap the gas pedal or she conks out, have to let it run for few minutes before touching the gas. Never had that issue until I just put in this new software this week.

Thanks!

[VdubBry]

Switched to a full DV valve, got the OEM one used in VW/Audi etc. 06A 145 710N. Well it runs way worse, the AFR sits at almost full rich, the idle bounces worse and when I drive the car, it's running lean (per the AEM AFR)

[C2Motorsports]

I think that we are missing something basic with your setup. We am leaving in the morning for Waterfest, but I would like to dedicated some time with you and your setup when we get back into the office.

[VdubBry]

I think that we are missing something basic with your setup. We am leaving in the morning for Waterfest, but I would like to dedicated some time with you and your setup when we get back into the office.

Thank you, yes I would really appreciate it. You can call me if easier when you are back.

I am on my second C2 software etc. It has to be something basic and related to afr. Is that DV I put in there that the 1.8T uses a good one to use? It definitely ran better before with the partial blow off valve. I have the full version of VCDS from Ross-Tech so I can get any readings you need there also.

[dubber89]

i am using a stock new 1.8t diverter valve. my AFR was around 13 too idk if thats how the c2 software runs but i use a wideband and a manually adjustable fuel pressure regulator and manually dyno my car in 3rd gear on the highway. then make adjustments. i still dont drive the car much it still has the same issue

[TBT-Syncro]

i am using a stock new 1.8t diverter valve. my AFR was around 13 too idk if thats how the c2 software runs but i use a wideband and a manually adjustable fuel pressure regulator and manually dyno my car in 3rd gear on the highway. then make adjustments. i still dont drive the car much it still has the same issue

adjusting your fuel pressure wont do anything, as long term fuel trims will just dial out the additional fuel.