ColtSteele

I posted this on a few dodge boards, just want to see if anyone else can help. Thanks and sorry for the NOVEL.

On July 1 I had installed Richmond Pro Drag Race 4.56 gears and a Powertrax Street Locker. That same night we installed a nitrous express kit on my buddys 03 Quad Cab. Finish his install, I follow him while he's making his first few runs to test out the kit. SO, me being me, I decide i want to hit it just one time to see just how big a difference the new gears would make. I waited til I was mid way between 1-2 shift and I hit the button. Tach shoots up and it shifts gears and I hear a faint POOOP!. I stay in it (thinking it was a car that had passed in the other direction) tach rolling over to the 2-3 shift and another POOOP! Not a loud/ hard backfire, but just a noticeable small backfire. Well I pull over and make sure nothing is loose and check my bottle pressure, it's fine. I decide I want to do it again. I hit it again and at 1-2 shift- POOOP. Dammit SON!!

Ok, this is where I PM Motohead, he calls, we talk, I go to bed with a plan. Check plugs, if not, I must be bouncing off the rev limiter, the computer will learn that the rpm spike is gears and things are ok!! Stay off the spray at shift change until the Superchips programmer comes out! (Don't want the HPP)

Next morning- pull a couple plugs, no problems. I go to the track.
(No I'm not coming off the line hard in any of these races since I have new gears. I figure someone will say why are you racing with new gears. The place that installed said I could and they would cover them for warranty)
Anyway, First run, I let off the nitrous button during shift change, no problems.
Next time I hold it through gear change (that's the video in racing of me beating the SRT10QC) no backfire in 1-2 but it does backfire at 2-3 shift. But it is fainter than any of the others.
Last run, I hold the button through all gear changes and no backfire at all. So I think it's fixed. I run a few more times, holding through gear change and have no more problems.

Well yesterday I wanted to get a couple nitrous runs in since I just put a new 2800 stall torque converter in. Well it pulls way hard but at the 1-2 shift what do I have- POOOP. Another freaking backfire. WTF?!?!?!
Am I still bouncing off the rev limiter?

About 2/3 weeks prior to this I put my headers and y pipe and tossed the rear cats and pulled the O2 sensors.
Does removing the rear O2 sensors do something to my fuel mix?
Does it push more in to be safe?
I've read that Dodges (and Jeeps) ONLY use the rear O2's to sense whether or not your cats are bad. That they serve no purpose to correct any air or fuel problems.

After the header and y pipe install I ran on spray several times and had no problems at all. I've had a cel ever since unhooking the rear O2's and have a O2 sim that I plan to install tonight as long as the rain holds off. I just don't think this would do it.

I am going to try to get a dyno session for friday to make sure my A/F ratio is good.

If anyone has any ideas or can help- please do.

Thanks
CS

1slow01Z71

iTrader: (36)

Not a lcue man sorry I cant help maybe its the a/f ratio but I ahvent experience that. My buddy had that problem but it ended up being a fried plug I believe.

one03sierra

iTrader: (1)

well you are unable to take out torque management. and the computer seems to be learning. whenever you make another mod to the truck it is going to have to learn it. when you first did it you said that you also put in gears. well the comp had to learn that as well. then you said that it worked for a while. then you installed a converter and it did it again. the comp will have to learn that as well. also with tqm and the shifts--when the truck goes to shift it is pulling timing and then bringin it back up quick. timing effects nitrous a lot. with the converter your shift extension is different and the pcm is trying to compensate for it. i think it will,learn it out eventually. hey isnt motorhead named jared. if so tell him i said hey.

ColtSteele

Thanks for your help.

Yea I do expect it to "relearn" the gears and tc. I just found out that when the tc was installed the mechanic pulled the battery cable off for about 3 hours, so the computer definitley reset its self. That put it back to stock parameters, 17" wheels and 3.55 gears with the stock tc. With 22's, 4.56's, a nice shot of spray and a 2800 stall tc I'm sure the computer is shi77ing it's pants. LOL
I'm going to drive it like I stole it for the next two days and try to get to the track friday night and make a few passes to see what happens.

Thanks for helping.

ColtSteele

well- I sprayed one more time late last night. No backfire at 1-2 shift but it did at 2-3 shift.
Ran it hard today and it seems to be getting back in the groove. Hopefully it will be fixed by tomorrow evening. I want to get to Ware Shoals Drag Way and get a few runs in. I just nee dto get a hold of som e17" drag radials... anybody know where a pair is for sale???

Anyone else had any exhaust backfire while spraying??? Not intake backfire- exhaust.

Thanks for any help!

02sierraz71_5.3

iTrader: (2)

if it doesnt do it on the spray then you know its from no2, not to be a smartass.

Im wondering why it would backfire on the exhaust side especially with nitrous I thought it aided in the combustion process there shouldnt be any combustible fumes left over to backfire in the exhaust

ColtSteele

No prob 02sierra-
We know it's from the spray, just trying to narrow down exactly why.

I've got a theory as to why it's doing it.

The new, much steeper than stock gears (3.55 to 4.56) and the 2800 stall tc are far from stock. And since the cpt was reset when the tc was installed sending it back to running on stock parameters. We think the motor is reving so fast that the computer is not telling the tranny to shift soon/quick enough and I'm bouncing off the rev limiter. So the engine is cutting back timing but I'm still spraying. And once the cpt resets timing the extra fuel sprayed in with the nitrous is then detonated- thus the small backfire. I'm only running 52/33 jets.

This happened a couple weeks ago when I first switched out the 3.55's for 4.56's. It pretty much happened the same way. First 2-3 times I sprayed it backfired. When I posted the first post in this thread I didn't know the guy had unhooked the battery for that long and reset the computer. So I was worried I had screwed up putting the higher stall tc in. You can see above where I foubnd out he had reset it- now I'm pretty confident that my theory above is correct. I just wondered if anyone else had had anything similar to this happen.

Thanks for your help
CS

one03sierra

iTrader: (1)

because on a hemi there is a plug for compression and one on the exhaust side as well. the engine fires one for compression and then fires the other on exhaust. so as it is pulling and adding timing it is firing them at different times causing it to backfire.

ColtSteele

Could lack of back pressure increase the likelyhood of backfire?

02sierraz71_5.3

iTrader: (2)

I wouldnt think so a freer flowing exhaust should help with combustion if anything, thats why most pick up mpg with good exhaust. Exhaust backfires are from only one thing unspent fuel