Popping and backfing under boost
Popping and backfing under boost Just finished my new turbo build and my question is what could be causing it to be breaking up and popping when it goes to wot. If I ease into it from a roll it does fine but if I nail it from a dead stop it starts breaking up, mostly at high rpm. I changed out the plugs and put some 8's in gapped @.025, and new wires, etc but I'm still having the same issue, what could be wrong?
With a PT88, I hope it would be tuned!!
Whats the mixture like? How much HP roughly? Valvetrain setup and boost levels?
There are a lot of things it could be, more information helps
Louis
Whats the mixture like? How much HP roughly? Valvetrain setup and boost levels?
There are a lot of things it could be, more information helps
Louis
Yea its been tuned, I've already decided to go with twins, but I was thinking it would do fine at low boost with the single pump. Everyone I've talked to says it's emissions related. ie plugs, wires, or coil packs.
It made 531rwhp at 50% throttle on the dyno before I had to let out of the throttle, so the pump is definatley on the edge.
It made 531rwhp at 50% throttle on the dyno before I had to let out of the throttle, so the pump is definatley on the edge.
Last edited by SuperC1; Apr 12, 2009 at 10:09 AM.
It's between 11.5 and 11.8 on the mixture, everything looks good, just starts breaking up around 6K.
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It starts breaking up at 55psi even though the mixture is 11.8-11.5 afr at 5800 to 6000 rpm. The pump is a racetronix pnp setup with a hot wire kit. I'm looking into running a second pump off a hobbs switch, where can I purchase one of those?
Last edited by SuperC1; Apr 12, 2009 at 10:42 AM.
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If your running a single fuel pump it is most likey that. I maxed mine at 540whp and had to let up on the dyno. I would think 11.3 would be more ideal. 11.8 seems a little on the lean side.
It was dropping down to 10.5, so I had to lean it out a little, it was still breaking up though, I let out at 531 on the dyno cause it wouldn't rev any further.
Could be too much fuel at that RPM (tune issue). I had similar problems with my setup recently, its been tuned but I thought I'd try a set of TR8s...good idea from what I 'heard', but it didn't wanna keep a set of TR8s in it at all, fouled them in about 10 mins of driving and was doing the popping thing under about 3/4 throttle and 4+ psi of boost. Put TR6s gapped at .028 (gapped tight as it was blowing out the spark at .035) back in the car and its driven great since. You might try the same or maybe try a TR7....the 8s are very cold and may be too cold for your app.
Good point. I tryed tr8 plugs in my car and I started having problems and when I pulled them the looked bad so I put a set of tr6 plugs in it and been running them ever since. The tr8 is a really cold plug.
Popping What kind of coil packs you have? I had the same problem with my procharged car, It turned out the car packs didnt have enough stuff to keep it goin. Switched to truck packs and problem solved go's to 7000 no problems not stumbling or anything like that.
Running stock coil packs right now, a set of truck coils would be nice though. But I was told that the stock coils would work fine, is that a bad idea?
Well the stock coils should have no problem with your setup.
What kind of plug wires do you have?
What valve springs do you have?(valve float maybe)
What do the plugs look like after if acts up?
Any more info on your setup might help.
What kind of plug wires do you have?
What valve springs do you have?(valve float maybe)
What do the plugs look like after if acts up?
Any more info on your setup might help.
Plugs look clean, the wires were msd street fires custom made because the original msd's weren't long enough. Been thinking about going with some 8.5mm's though and wraping them with some heat shielding tape. Valve springs are patriot dual gold. I'm leaning towards the wires being the issue though, cause the pressure drop was very little. Adding twins was already in the making, just need two pumps to go in the bucket, going to dump the racetronix single. I got some -8 and -6 steel braided lines here already and boost reference regulator with rails ready to go. Just hate to tear down the car again.
Last edited by SuperC1; Apr 12, 2009 at 10:24 PM.
