I am experiencing a problem under high boost..

At about 20-21 lbs during a long 3rd gear pull, a loud backfire happens and MS resets. My overboost protection is set at 249kpa, and the BASE number of sparks to cut is set to 3.

I feel like this is the wrong number of cuts -what would be a better number, 4?

BTW at about 21lbs, I was able to put down 300whp even. I left after an hour of tuning and my 3-4k rpm were still a little rich.

I sucks that there is no zoom feature on the MSlvv -I might need to start thinking about making something in visual basic.

Explain you complete MS setup.

Spark ignitor ect?
MS for fuel obviously
Where are you getting 12v positive from?
Ignition box?


This is a problem ExtremeRS and a few others have had cause by weak spark.

Terry

Yep, exactly! I fought with this issue all summer long, only to finally find out it was due to a weak spark, caused by the dwell code in the MS Extra firmware. I havent tried out the version that was supposed to fix it, but I ultimately installed a Crane ignition CDI box, which completely solved the misfire/backfire. A rather expensive solution,but it works great. I still use the Mitsu ignitor to fire the Crane box.

I've found that a lot of MS resets can happen because something sends current back into one of the outputs. For example... my 4G63 ignition module overheated a while back, which creates a condition called "thermal runaway" in the transistor which makes it not act like a transistor anymore and send current back into the processor. When this happens the MS resets.

I am using the mitsu ignitor, the v2.2 board, remote mounted TIP42C. I am not using a crane box.

This is great info.

I noticed that I am getting backfires more often in hard 3rd gears pulls @ 10psi+ -only once did the MS reset, so now I lowered the boost till this problem is under control.

Can I just increase the dwell to help this problem? Currently i am at 25/5.5/.1

Would the Mitsu ignitor be less likely to overheat when used with a crane box?

Originally posted by rs-pssst
Would the Mitsu ignitor be less likely to overheat when used with a crane box?

Yes, because you're sending such a high voltage to the primary coil that dwell isn't really an issue anymore.

Your issue at 21 PSI (backfire) doesn't sound like weak spark... it's likely the overboost protection (21 PSI = 249 kPa).

However, a few messages down you said you're now getting a reset just over 10 PSI. That's likely weak spark, based on reports from others.

One question- what is your running dwell value?

I had this issue with boost from 11-12+ psi. 10 psi it was fine. Its a weak spark. My ignitor stays cold when firing the crane ignition box. CDI boxes do not rely on dwell time, which is why it works with a dwell messed up code.

My running dwell is 5.5. It is possible that it is over boost protection on the high boost. But backfires are happening at 11, 15, and 18psi.

I just ordered the crane box yesterday -I can't wait to feel how strong this is going to pull

Originally posted by rs-pssst
My running dwell is 5.5. It is possible that it is over boost protection on the high boost. But backfires are happening at 11, 15, and 18psi.

That's what I was saying. If you were boosting 21 PSI and your Overboost Protection was set to 249 kPa, then the protection was kicking in (because 249 kPa = 21.something PSI). The 10-20 PSI MS resets are most likely the same problem that XtremeRS has encountered. Who knows why some of you guys are getting MS resets over 10 PSI... nobody that I know of has found a solution other than to use a CD box.

Originally posted by rs-pssst
I just ordered the crane box yesterday

Smart move. :thumbsup

Yeah the problem with just upping the dwell time, it gets the ignitor super hot, which i dont think is a good thing. I mean, it can handle some intense heat, as that thing is bolted right by the cylinder head on the 4g63 engine. I also ran slightly larger plug gaps as well, which could have contributed to the misfires, esp when a weak coil charge is happening all at once. I ran around .032" gaps, and still run that with the crane box.

Originally posted by XtremeRS
Yeah the problem with just upping the dwell time, it gets the ignitor super hot, which i dont think is a good thing. I mean, it can handle some intense heat, as that thing is bolted right by the cylinder head on the 4g63 engine. I also ran slightly larger plug gaps as well, which could have contributed to the misfires, esp when a weak coil charge is happening all at once. I ran around .032" gaps, and still run that with the crane box.

What dwell time are you using now with the crane box? Im curious because I will be installing my MS with my Crane box and am excited by the fact that dwell becomes les significant with it.

hmm i'll have to check..its been a while since i've played around with it and even longer since i've driven the car(toasted the clutch a while back)..I believe its around 4.0 ms..i noticed it did idle a bit smoother when i uped the dwell from like 3.0ms where i started at. When running the crane box, even with increasing the dwell to maximum in megatune, the ignitor still stays cold.

Technically, you shouldn't even need the ignitor with a CD ignition box.

Originally posted by DarkOne
Technically, you shouldn't even need the ignitor with a CD ignition box.

nope you shouldn"t..but i didnt want to mess around with inverting the signal from the MS, and i know nate had some issues with his MSD when tring to fire it directly from the MS..so i figured using the ignitor to fire the crane was more of a "stock" way to hook the box up(eg using the crane on the stock ECU and stock coilpack)

Originally posted by XtremeRS
nope you shouldn"t..but i didnt want to mess around with inverting the signal from the MS, and i know nate had some issues with his MSD when tring to fire it directly from the MS..so i figured using the ignitor to fire the crane was more of a "stock" way to hook the box up(eg using the crane on the stock ECU and stock coilpack)

The ignitor adds another layer of protection inbetween the Crane/MSD box and the MS in case the Crane or MSD thing fails. It shouldn't be needed but if it works...

Back when I was trying to get it to work with my MSD unit I didn't really know what I was doing. I haven't really tried it since then because the 4G63 ignitor works well enough for my setup.

Got the Crane Box installed....

Holy crap!!

This thing pulls hard! Def crossed the 300whp mark (since I was 299.4whp @5400rpms @20psi b4 backfires) I haven't been able to do hard 3rd or 4th gear pulls in a long time.....

Amen to the crane setup -it works like a charm.

Ok, so still making backfires...

I figure its because I overheated my mitsu ignitor and caused the transistors inside of it to become faulty under high load.

It only backfires above 15psi after the car has been driven for 20-30min

If i start the car cold, and drive to warm it up, then give it a nice hard 20psi 3rd gear pull, it works fine and pulls like a bastard.

After the car has been driven on the highway for a while the backfires will start to occur at random psi levels of 15psi or greater.

I figure its because the ignitor is faulty and it heats up becoming ineffective.

The ms fires the mitsu ignitor by grounding it? What does the crane box need? I want the crane box to be the only thing after the ms.

How can we eliminate the mitsu ignitor, thus making this setup cheaper with less parts to fail?

Run the output wires directly from the MegaSquirt ECU to the Crane Box. Then then invert the spark output (MegaTune setting).