# Spark blowout and need some help



## diceman469 (Sep 3, 2003)

Not short, but I wanted to be sure you had ALL the data in the first post. I'm looking for experienced, informative replies http://****************.com/smile/emthup.gif
Setup is an ABA/16VT stock internals.
Exhaust side: T3 .63 / T4 .57 Stg3 turbo, turbonetics manifold, Tial 38MM, 3" turboback with no cat.
Intake side: 1.8PL head with mild port, stock 40mm scirocco manifold, 2.75 intercooler piping into an ebay FMIC. Intake temps do not exceed 130 degrees unless sitting in traffic or at idle (pulls air from engine bay). 55lb low impedance injectors and a Bosch 044 fuel pump. Duty cycle between 60-70% in problem area.
Management: MS2 triggered off distributor and fires through the stock bosch module (not directly off the VB921). NGK BKR7E gapped at .025, magnecore 10mm ignition wires.
Problem: Car runs absolutely fantastic all the way up until around 15-16PSI and then I get spark blowout. It seems to only do it in 3,4,5th gears. 1st and 2nd gear seem to be fine, but I'm not really in those gears long enough to properly diagnose. What I've tried so far:
Gapped plugs as small as .018 with no improvement
Replaced Spark plugs
Replaced Rotor and Distributor
Moved Ignition Coil into rain tray
Both retarded and advanced timing 2-3 degrees in problem areas
Both increased and decreased fueling in problem areas
Datalogs show AFRs in the low 12s when the blowout occurs. Timing has been adjusted between 13 and 18 degrees with no difference. I can use some professional input. I've been searching this problem both on here and google for a month, so trust me when I say I've exhausted my resources.
Here is my theory. Please tell me if I am on the right track:
Now if you look at my tables, you'll see how my VE tables definitely flatten out at a certain point. This leads me to believe there is a certain bottleneck here.
The tables:

























I have come to the conclusion that it is my turbo manifold that is causing this problem. I'm theorizing that excessive backpressure is not allowing the spent gas to completely exit the combustion chamber, and that the fresh air charge is being so diluted that there's not enough a/f to actually fire. Pic of culprit:








Not very well designed for high flow, but I wasn't as well educated in turbocharging at the time as I am now. I'm looking for some validation before I do something about it. I'd hate to go through the trouble to find out it was something simple that I overlooked.
So how about it, turbo gurus, can your extra pair of eyes see something that I overlooked? Thank you in advance for your help!


_Modified by diceman469 at 10:35 AM 9-3-2009_


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## diceman469 (Sep 3, 2003)

*Re: Spark blowout and need some help (diceman469)*

Really? No input? If the answer isn't "search" I guess there IS no answer?!?


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## TBT-Syncro (Apr 28, 2001)

*Re: Spark blowout and need some help (diceman469)*

post in the SEM forum, you'll get better responses for tuning.
the one big detail you've left out - fuel.
is it possible you've been buying bad fuel from a particular gas station?


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## diceman469 (Sep 3, 2003)

*Re: Spark blowout and need some help (TBT-Syncro)*

I posted in the 16V forum...overlooked SEM

As far as fuel, I buy from various places and I've cycled through several tanks. I'm really thinking about tapping the manifold so I could measure my backpressure. I've turned down the boost for now.


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## TBT-Syncro (Apr 28, 2001)

*Re: Spark blowout and need some help (diceman469)*


_Quote, originally posted by *diceman469* »_I posted in the 16V forum...overlooked SEM

As far as fuel, I buy from various places and I've cycled through several tanks. I'm really thinking about tapping the manifold so I could measure my backpressure. I've turned down the boost for now.

you may want to try setting the boost to the max safe level, and then advancing the timing. this way you can figure out if it's the boost, or the timing thats causing the problems.
you shouldnt need to gap your plugs that small though. I run a .032 on those plugs at 18psi on my VRT


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## kompressorgolf (Dec 6, 2005)

maybe the coil/spark is too weak?


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## diceman469 (Sep 3, 2003)

*Re: Spark blowout and need some help (TBT-Syncro)*


_Quote, originally posted by *TBT-Syncro* »_
you may want to try setting the boost to the max safe level, and then advancing the timing. this way you can figure out if it's the boost, or the timing thats causing the problems.
you shouldnt need to gap your plugs that small though. I run a .032 on those plugs at 18psi on my VRT

I'll give it a shot. When I adjusted the timing, I left the boost setting alone, and there was no change. I'll see if I can duplicate the problem at 12psi through tuning.


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## lap (Nov 20, 2005)

i have the same issue with my icm on vr6 running MS1. when i switched to Vb921 the spark is stronger and no blowout issue


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## diceman469 (Sep 3, 2003)

*Re: (lap)*


_Quote, originally posted by *lap* »_i have the same issue with my icm on vr6 running MS1. when i switched to Vb921 the spark is stronger and no blowout issue

Interesting...I'll have to look into that


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## VOLKS-MAN (Oct 7, 2000)

*Re: (diceman469)*

Try regapping at .022" and set the dwell higher.
Sorry I did see you regapped at .018"...
VB921's should be fine for low a current ignition driver.

_Modified by VOLKS-MAN at 10:15 PM 9-5-2009_


_Modified by VOLKS-MAN at 10:19 PM 9-5-2009_


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## pdogg (Nov 11, 2004)

*Re: (VOLKS-MAN)*

what r u using for wires? my car and my buddys did the same thing till we swaped to 9mm msd wires custom made buy me now no probs at all, you can get them at summit or jegs they were for a 89 bbc


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## diceman469 (Sep 3, 2003)

*Re: (pdogg)*

Magnecore 10mm wires.
I already increased the dwell to no avail. I just upgraded the megasquirt firmware to the newest one and recalibrated the wideband. I'm going to drive and datalog tomorrow.


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## diceman469 (Sep 3, 2003)

*Re: (diceman469)*

I may be getting somewhere.

I reflashed MS and recalibrated the wideband. I found I was running more rich than anticipated. After datalogging I found the areas I believed to be running at 12.5 AFR were indeed running around 11.6.
Recalibrated the VE table through megalogviewer and alot of fuel was pulled up top. I can now run 15psi with about half of the blowout I had previously. Increased power in the 10-15psi area. I'm going to continue to datalog and lean out as needed over the next couple of days. I will post my findings here for future reference.
Oh yeah and tip of the day: After reflashing the firmware in MS....don't forget to recalibrate the wideband INSIDE tunerstudio and write it to the controller! I spent an hour on the stim trying to figure out why my wideband would toggle from 12.1 and 17.0 AFR...


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## Salsa GTI (Aug 29, 2000)

*Re: Spark blowout and need some help (diceman469)*

get an EGT gauge in your car first and formost............
You dont have enough ign advance at full boost...its way retarded...and for me I would spend the time to toss the dist in the trash and go wasted spark
off the VR sensor in the block...
I believe its a timing problem...also check fuel pressure at full boost usinf a gauge you can see while driving at full throttle in 3rd gear.....or get an electric fuel presure gauge to mount in the car....it's a good idea


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## diceman469 (Sep 3, 2003)

*Re: Spark blowout and need some help (Salsa GTI)*


_Quote, originally posted by *Salsa GTI* »_get an EGT gauge in your car first and formost............
You dont have enough ign advance at full boost...its way retarded...and for me I would spend the time to toss the dist in the trash and go wasted spark
off the VR sensor in the block...
I believe its a timing problem...also check fuel pressure at full boost usinf a gauge you can see while driving at full throttle in 3rd gear.....or get an electric fuel presure gauge to mount in the car....it's a good idea

Most informative post yet....thanks!
I was tossing around alot of the ideas you are referring to. I took out my MS with the intent on switching it to wasted spark, but decided to leave it for now. I don't want to toy with too much right before H20 and risk not having her ready. The EGT gauge is another thing I'd like to install, but H20 funds > EGT gauge right now








The timing advice is really what I was looking for. What would you suggest? My trigger angle is spot on as I've just checked it last weekend (6deg advance in the spark table lines up perfectly with the 6deg mark on the flywheel) so these advance numbers are actual. Keep in mind that at 15psi I am not hitting the two top rows yet. How does my timing look at 200KPA? That is where I am running into problems.
Since I haven't gone above that too far yet, timing was declined at a linear rate to be safe for now.
As far as fuel pressure is concerned, it seems that pulling fuel out alleviated the problem to an extent...so I'm going to make the assumption that fuel is ample at this point. But the gauge doesn't hurt.
Keep the advice coming...


_Modified by diceman469 at 10:53 AM 9-8-2009_


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## Salsa GTI (Aug 29, 2000)

*Re: Spark blowout and need some help (diceman469)*

what are you reading tour Air Fuel Ratio with?


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## diceman469 (Sep 3, 2003)

*Re: Spark blowout and need some help (Salsa GTI)*

Innovative LC-1


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## diceman469 (Sep 3, 2003)

*Re: Spark blowout and need some help (diceman469)*

Update:
So I decided to finally grow a set and get aggressive on my timing. Adjusted the AFR and ran two datalogs to adjust the VE table. These tables are tuned to 200KPA. Some more tuning is to follow:
























Much more power, no pinging that I can hear. I think it's kind of odd the way the VE table falls off up top, but I verified it in the datalogs.
Tomorrow weather permitting I'll turn it up to 18 and see if my problem is gone.


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## EL DRIFTO (Jul 11, 2004)

*Re: Spark blowout and need some help (diceman469)*

VE table looks right for your setup


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## diceman469 (Sep 3, 2003)

*Re: Spark blowout and need some help (EL DRIFTO)*


_Quote, originally posted by *EL DRIFTO* »_VE table looks right for your setup

The part I'm talking about in particular is where it drops off from 121 to 99...looks abrupt as hell to me. I checked it on my datalog, and it was right at 12.2:1. Odd but correct it seems...


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## EL DRIFTO (Jul 11, 2004)

*Re: Spark blowout and need some help (diceman469)*

6500 is where that 1.8 plenum 40 mm runner scir manifold seems like it would run out...just guessing
i dont know if you're revving to 7k, but if the fuel pump/press starts to drop off, the o2/ve correction may add exponential duty cycle to keep fuel volume with dropping fuel press...


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