backfires

[firemanems06]

when i get on my kawi hard, the motor backfires when letting off the gas.. it has never done this before.. i have a pc3 mapped with no baffle and no air box lid.. i live in south florida so the only gas down here has 10% ethanol.. im wondering if this may be the problem.. if so, are there any fuel additives that can be mixed in?

[offroadhunter]

Sounds like your fuel map may be too lean and causing that backfire...not sure about the ethanol though

[teamDNS188]

QUOTE (offroadhunter @ Jun 2 2008, 07:52 PM)

Sounds like your fuel map may be too lean and causing that backfire...not sure about the ethanol though

check to make sure your fuel injector is clean and your octane is high enough. if you run anything less than 92 its gonna pop and and overheat.

[madracing]

lower your idle or set it back to factory spec.

[firemanems06]

i run 93 octane.. it's never done this before.. that's why i think it's the gas.. the idle is at factory

[madracing]

Double check your throttle position sensor settings. Note that's going to affect your idle speed. So you a adjust the throttle position sensor first then adjust your idle speed second.

TPS should be .58 mV (stock)

1. remove engine mount
2. loosen torque bolt on TPS
3. using a digital ohms meter set on 2.5 DC tap into yellow w/white wire on ESC (left side/top)
4. warm up quad and set idle to factory
5. then attach the meter (may be easier with two people) adjust the voltage to specifications
6. tighten down the torque bolt and double check the voltage readings
7. doublecheck the idle speed
8. all done have a beer



One other thing that just came to mind make sure your header pipe is not cracked. This will deftly created backfiring and throw off all your settings.

[firemanems06]

thanks..ill see if that solves it

[Rhino1]

I think its the ethanol leaning your mixture out a bit. Call Dynojet (or the people that you bought the PCIII from), and see if they have a map for your mods under those conditions. That would be the safest and easiest thing to try first. Popping off throttle is usually a good indication of a lean situation.

[firemanems06]

i called dynojet.. they said the deceleration pop and backfire is due to unburned fuel in the exhaust mixing with air rushing in. it can be caused by either an exhaust leak or if that wasnt te case, i was told to increase everything in the 0 column by 10-25, starting at 10, from the 2000rpm column-redline.. he said the backfiring ismt a big deal and doesnt affect performance or the motor.. i was told it has nothing to due with the motor..

[madracing]

QUOTE (FiremanEMS06 @ Jun 4 2008, 09:19 PM)

he said the backfiring ismt a big deal and doesnt affect performance or the motor..

Was this guy a sales guy????

I have Dynoed over 15 quads with 100's of runs and I strongly disagree with his statement. On a fuel injected quad backfiring should not accrue at all if everything is set properly. I have a lot of respect for some of the engineers over at Dynojet Research Inc., but there are a hand full of guys over there that repetitively give out very questionable advise/information.