Afterfiring around 3k

I have an 05 mustang gt with a kenne bell 2.6 stage 1, and comp mutha thumpr cams. After having the car dyno tuned I've noticed a after fire around 3k when cruising down the highway. The car only does it when you slowly increase throttle after holding at steady speed like when your climbing a hill. The after fire is worse the more you press the throttle in. I've changed plugs so far and still nothing.

You may wish to make an intro in the newbie area as a gesture of proper protocol.

You imply the car ran fine before the "dynotune", so since there were no additions to the setup, one would have to conclude since this started happening just as soon as it had been dynotuned (over whatever previous tune method one would have to conclude worked fine), that it would be the dynotune. Take it back to the tuner.

Sorry, yea this is my first post. I never it drove post blower install. It ran great with just cams. I installed the blower and trailered it to the dyno. It runs great at wide open throttle, with the afr's in the 11s and 18* timing. I've tried different brand plugs and different gaps, but it's still has that afterfire.

What is an after fire?

If it runs good at WOT than like said above, the tune needs adjustment.

Don't know what you mean by "afterfire" either. Either way, take it back to the tuner. There in lies your best source of resolve.

Marble said:

What is an after fire?

If it runs good at WOT than like said above, the tune needs adjustment.

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redfirepearlgt said:

Don't know what you mean by "afterfire" either. Either way, take it back to the tuner. There in lies your best source of resolve.

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Afterfire is the proper term for what we call a backfire in the exhaust. Technically a backfire is an uncontrolled explosion back up the intake. When this detonation occurs in the exhaust it is called a afterfire, technically. Same same, kinda.

07 Boss said:

Afterfire is the proper term for what we call a backfire in the exhaust. Technically a backfire is an uncontrolled explosion back up the intake. When this detonation occurs in the exhaust it is called a afterfire, technically. Same same, kinda.

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Sorry about the confusion from using afterfire. i should've explained it in the first post. Anyways, I figured it had to be something tune related, maybe too rich mid throttle? I was just looking for ideas of things to try that may have been overlooked when the blower was install that might save me a 3 hour trip to Charlotte to have it retuned.

Amazedz said:

Sorry about the confusion from using afterfire. i should've explained it in the first post. Anyways, I figured it had to be something tune related, maybe too rich mid throttle? I was just looking for ideas of things to try that may have been overlooked when the blower was install that might save me a 3 hour trip to Charlotte to have it retuned.

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Why not just data log it and send him the file?

Amazedz said:

Sorry about the confusion from using afterfire. i should've explained it in the first post. Anyways, I figured it had to be something tune related, maybe too rich mid throttle? I was just looking for ideas of things to try that may have been overlooked when the blower was install that might save me a 3 hour trip to Charlotte to have it retuned.

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FI cars do run richer than NA cars WOT. 11.2-11.6 WOT vice 12.6ish N/A WOT. Some tunes like Roush will run as rich as 11.0 WOT. The point at which most tunes go open loop is typically at 3000 RPM. My FI car with stock cams will generate a very mild afterfire/backfire on the exhaust side when letting off of the gas as the engine speed decreases. I haven't driven the car in 2 months now, so I can;t get specific as to what RPM level,sorry about that.

Call the tuner and speak to him/her very specifically about this before going. Remind them what your setup is down to the cams and the RPM range at which you are experiencing this. It may be something they can correct and email a tune revision to you without making the trip or it may simply be normal.

Good luck. Sounds like a sweet setup.

05stroker said:

Why not just data log it and send him the file?

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Very good idea to do this as well, before calling. Email it then speak with them over the phone in specifics.

Okay, thanks guys. I'll get out there and data log it to email Dan @ prodyno once I get a dc inverter installed since my laptop battery is awful. I called him after it first happened on the way home with the car, and the first thing he said to try was to get the hto brisk plugs out of the car and get a set of hto autolites. It's nowhere near as bad as it was the first time now, but it's deffinetly still there. I know fi cars tend to be a bit richer at wot the n/a, and mid 11s is where I'm happy with it being at wot. I'm just a bit worried about this afterfire hurting the motor. It tends to happen right around 2600-3000 when you increase throttle like when trying to maintain the same speed while climbing a hill. The car is an auto with a 3k stall in it aswell.

I have a small ac inverter that just plugs into the 12v outlet. Been plenty fine for me so far too data log my car

If/when you take the Brisk plugs out, would you consider selling them if they aren't fouled? I'm trying to build up a cache.

^^^ Man I wish I had not thrown out that set of Brisk from my 05 that were slightly used last fall when doing a clean out. I would have sent them to you for the price of shipping. Sorry.

Amazedz said:

Okay, thanks guys. I'll get out there and data log it to email Dan @ prodyno once I get a dc inverter installed since my laptop battery is awful. I called him after it first happened on the way home with the car, and the first thing he said to try was to get the hto brisk plugs out of the car and get a set of hto autolites. It's nowhere near as bad as it was the first time now, but it's deffinetly still there. I know fi cars tend to be a bit richer at wot the n/a, and mid 11s is where I'm happy with it being at wot. I'm just a bit worried about this afterfire hurting the motor. It tends to happen right around 2600-3000 when you increase throttle like when trying to maintain the same speed while climbing a hill. The car is an auto with a 3k stall in it aswell.

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You could try reducing the gap on your existing plugs by 2-3 thousandths to see if that resolves the problem prior to dropping $90 bucks for another set of plugs. Sounds like he may be thinking it is spark blow out. The datalog should provide some insight no doubt.

Appease the tuner as I have learned, and install what he prefers when doing a follow up if nothing else after datalogging.

Sounds like a nice setup when you get it tweeked to the happy point.

I appreciate the thought anyway. Plugs for these cars are expensive and I would hate to throw away $100 every time to diagnose a misfire!

Yea I've already thrown the autolites in the car, and went from 35 thou to 30 thou and it really helped. The afterfire is much less now than it was, but it's still there. If you want those brisk plugs they have maybe 100 miles on em, just dyno time. You can have em price of shipping if you'd like.

Actually I take that back, dad just dropped two. So I doubt they're any good now

Awesome! What's your email address? I tried sending a PM but I don't think your inbox is set up yet because of your post count.

Also to remain on topic, when I was having a part throttle hesitation issue, changing the coil boots fixed it. I don't know if you've already changed those or not. The problem has started to come back for me though in the form of an intermittent misfire (or should I call it afterfire) so I'll need to double check to see if any plugs have worked their way loose.