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Turbo misfiring
https://www.ausmini.com/forums/viewtopic.php?f=5&t=82751		 Page 1 of 1
Author:  Torchd76 [ Sun Sep 15, 2013 5:34 pm ]
Post subject:  Turbo misfiring
Anyone out there that can steer me in the right direction...I've tried re gaping the plugs down, fuel mixture, different ignition maps, installed a restrictive plate between the carby and plenum. The motor drives nice but as soon as it seems to come on boost around 35 - 4k rpm it stutters and carries on, the other day when testing it actually stuttered its way past the misfire and then took off like crazy. I'm almost at wits end, what should I look for? :(
Brief engine specs
Hif44
T28 Garrett
1100 +0.100" flat tops
Mega jolt ignition
Author:  Mick [ Sun Sep 15, 2013 5:53 pm ]
Post subject:  Re: Turbo misfiring
Are you sure the spark isn't blowing out under boost? As pressure goes up, the voltage required to jump the gap also goes up.

Put an ignition timing light onto the lead and see if the light flickers and misses under load with the engine. Hard to do on the road I know...
Author:  1018cc [ Mon Sep 16, 2013 4:02 pm ]
Post subject:  Re: Turbo misfiring
I had a similar problem with my megajolt in trying to track down a random missfire. All would be ok then bam,would back fire /missfire like crazy. Took me 20,000kms to work out what it was. What happened to me was the CAS and the plug that plugs onto the CAS were worn. It would vibrate far enough off (while still being clipped on) to be able to disconnect from the CAS. I bought a brand new CAS and a brand new plug and it hasn't happened since. Also take the opportunity to redo your wiring to the CAS. I found that my engine would vibrate just right at certain RPM for it to happen, hence why it only did it sometimes at a certain RPM.

Good luck and I know how frustrating tracking these things down can be!
Author:  Torchd76 [ Mon Sep 16, 2013 4:27 pm ]
Post subject:  Re: Turbo misfiring
Thanks a heap guys for the quick help!
As for the strobe light...I've done stranger in the past so ill give it a crack!
By the CAS do you mean the crank angle sensor? Cause I did have an issue with that plug a while ago actually :/ they never clip on properly
I've gone thru one angle sensor from getting fried and the plug didn't fit any better on its replacement.
If this rain sods off ill give these a look over, thanks a heap! Been pulling my hair out!
Author:  s-c1293 [ Mon Sep 16, 2013 7:41 pm ]
Post subject:  Re: Turbo misfiring
Another thing to check is to make sure your crank sensor bracket is strong enough. If it isn't, it can allow the sensor to vibrate at certain RPM's. This can cause misfiring and ignition cut out.
Author:  1018cc [ Tue Sep 17, 2013 1:51 am ]
Post subject:  Re: Turbo misfiring
Torchd76 wrote:
Thanks a heap guys for the quick help!
As for the strobe light...I've done stranger in the past so ill give it a crack!
By the CAS do you mean the crank angle sensor? Cause I did have an issue with that plug a while ago actually :/ they never clip on properly
I've gone thru one angle sensor from getting fried and the plug didn't fit any better on its replacement.
If this rain sods off ill give these a look over, thanks a heap! Been pulling my hair out!


I do mean the crank angle sensor when I say CAS. I replaced the bits separately at first (plug first) and the fit was very sloppy. When I replaced both the fit was perfect! Good luck with your problem.
Author:  Torchd76 [ Tue Sep 17, 2013 6:31 pm ]
Post subject:  Re: Turbo misfiring
Just did a quick test, was getting too late as its crazy loud so I could only do a short burst

Looks like the problem was the CAS plug, I took the spring clip off and bent it tighter and also secured the plug with a cable tie and it didn't seem to miss although I was taking it easy to try keep it quiet. Thanks guys! Will post up when I get to do a propper test
Author:  simon k [ Wed Sep 18, 2013 1:42 pm ]
Post subject:  Re: Turbo misfiring
being that its at a specific rev range, and when coming on boost it's more likely to be a weak spark... I had similar and ditched the Hyundai coil I was using and have 4 x LS1 coils instead - nothing will put those f*ckers out
Author:  m1100s [ Wed Sep 18, 2013 6:31 pm ]
Post subject:  Re: Turbo misfiring
simon k wrote:
being that its at a specific rev range, and when coming on boost it's more likely to be a weak spark... I had similar and ditched the Hyundai coil I was using and have 4 x LS1 coils instead - nothing will put those f*ckers out


I have used a Hyundai Getz coil pack at 12 psi supercharged without a problem. Only misfire I had was when my crank angle sensor was slightly out of line.

Ash.
Author:  Torchd76 [ Mon Sep 23, 2013 7:11 pm ]
Post subject:  Re: Turbo misfiring
Alright guys, issue was load related ignition map
I replaced the map with one I wrote with no difference in load changes (all identical across load ranges) still a tiny tiny misfire but it now works thru the rev range. takes off like crazy! so next stop is dyno session after I install the "innovate" afr gauge and sensor

thanks for all the help
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