Engine Sputters when throttle is hit and let off then hit agian quickly

I have witnessed the same issues, but not very often. My belief is we are running a little rich and when we let off the throttle quickly and back on it has more gas than needed. When this happens at night I get a flame out the side exit exhaust when I get back on the throttle. Scared the $hit out of me the first time it happened. I since have figured out how to make the flame come out when I want.

I bet it's worse if you let the rev limiter kick in at the top of 3rd gear or even 2nd gear and then shift fast to the next gear. It will probably sputter and fall on its nose. Am I correct?

Quote from rabtech

I bet it's worse if you let the rev limiter kick in at the top of 3rd gear or even 2nd gear and then shift fast to the next gear. It will probably sputter and fall on its nose. Am I correct?

That's when I get about a 2 foot flame.

I have a theory.... I think part of the stumble is because there is charge air left in the intake pipe when you let off the gas and then get back into the throttle. The engine can't handle the rush of air when the butterfly opens up. I know the BOV should get rid of that but I think it closes so fast (because you want to hammer the gas for the next gear) that there is still a small amount of air that gets trapped... Same thing happens when you hit the rev limit. The air is still being packed into the engine and when you hear the engine hit the limiter you clutch it and shift to the next gear. But you do it fast and the BOV doesn't seem to expel all the boost. Then the engine stumbles as it levels the air and fuel out.

Do this as a test. Run it up to about 5000rpm and do a slightly longer shift. Completely lift your foot off the gas between gears and let it empty the tubes of any boost before railing into the next gear. Let me know what happens.

I have done the longer shift. I think you are correct. At night if I am messing with someone on the right I quick shift just short of the rev limiter and get the flame. If I back out of the throttle right after the shift it will sputter.

You all talk like a two foot flame coming out the back is a bad thing? Guess it could be if you left your gas cap on the pump somewhere. I've just ordered my third one. I need a chain.

Quote from Slingrazor

That's when I get about a 2 foot flame.

Your flame is obviously unburnt fuel... so that tells you that you have spark and fuel. You just have to much air at the wrong moment. (in my opinion)

I need to change my BOV spring. When I switched over to the Alpha setup I noticed my BOV does NOT open up when I let up on my throttle. It's does open at full lift but not at partial lift. It should start to partially open at partial lift of my foot.

That is where I get the neat psuuu psuuu psuuu noise. But that is a bad noise. It's because my BOV isn't opening at partial lift and the wind from the turbo is being forced backward and hitting the turbo blades. It willeventually kill the turbo over time. But it makes the coolest noise while it's alive...

Same here. I eliminated mine by going to E3.74 plugs.

Quote from JoeF.

That is how started driving mine, I delay my shift and it does not seem to have the problem. Now, the backfire I started having was as soon as I installed the 1320 variable exhaust,I am using the middle size baffle, I had the TwinShot exhaust on it but DDM recommended I change it out due to the Hi-Flow CAT that has been untested. I ran it with the SC for 2 weeks with no issues, but changed it out last week as I don't want to take chances, now it will backfire once, in between shifts, even under normal driving. It does not do it a lot but it has never done that before the 1320. Its rather loud backfire that makes my girlfriend jump...lol Any ideas with that?
I am a rather experienced Tech, but sometimes its the simple things that are hard to duplicate that frustrate me and most techs....

Sir,
I am not having backfire issues that you mention. Initially I was running a custom MagnaFlow exhaust that exited out the back. The high flow of the SC exhaust killed that muffler because it was to close to the header. I have switched over to the Alpha side exit which performs very well. The slight stutter I have only happens when I have rolled on rapidly, back out of the throttle and lightly roll the throttle back on. I believe Rab's answer is 100 percent correct for my situation. I will look at reducing the spring tension on the blow off valve which does relieve under partial pressure where it is set now. It is an easy adjustment on our BOV, just turn the end counter clockwise.
The flame I have is self induced and I like it.

Quote from JoeF.

That is how started driving mine, I delay my shift and it does not seem to have the problem. Now, the backfire I started having was as soon as I installed the 1320 variable exhaust,I am using the middle size baffle, I had the TwinShot exhaust on it but DDM recommended I change it out due to the Hi-Flow CAT that has been untested. I ran it with the SC for 2 weeks with no issues, but changed it out last week as I don't want to take chances, now it will backfire once, in between shifts, even under normal driving. It does not do it a lot but it has never done that before the 1320. Its rather loud backfire that makes my girlfriend jump...lol Any ideas with that?
I am a rather experienced Tech, but sometimes its the simple things that are hard to duplicate that frustrate me and most techs....

You may want to check to make sure that the header and muffler bolts are tight and the gaskets are good.

It's just one of those things that everyone deals with in some sort of way. It was there when I had my Hahn setup and it's in the Alpha setup. If you haven't had it then your not driving the same as the others are... I have never seen a turbo system that ran exactly like stock. Mine even stumbled a tiny amount in stock form..

If you think yours doesn't have problem please post a video of you hitting the rev limiter between each gear and speed shifting it. I can't wait to see it...

I have never had mine to sputter. But I did get a good backfire out of it yesterday morning when I cranked it up. That was a first.

Quote from FunCycle

I have never had mine to sputter. But I did get a good backfire out of it yesterday morning when I cranked it up. That was a first.

Yea, they do that sometimes ...

I'm looking for a video of a turbo charged SS that doesn't hiccup between gears when it hits the rev limiter OR when its speed shifted at high RPM...