Back firing on 1st and 2nd gear at 4k+ ????

[mx54life]

Hi so I finally get to drive my 1994 w/ JSC gen 1 MP45 w/ a newly installed non-adjustable power card, brand new catalytic and O2 sensor after passing California Smog w/ flying colors. All I can say is that she rans better than the former set-up (spliced diode in between the MAF and ECU). But now I'm noticing some back fire on the 1st and 2nd gear above 4k. If I ease it up I don't hear any back fire.

1. Is this normal for rev above 4k on the 1st and 2nd gear? Only on these first two.

2. Is my timing off? She idles at around 750-800.

Any input would be greatly appreciated.

[DK Wolf]

Some people have bizarre meanings for backfire. You'll need to be more descriptive. As in you'll miss an ignition cycle and she chokes on hard accel? Or there's just a super loud pop(with or without power loss) on WOT.

If you aren't suffering powerloss, don't worry about it, it's probably just a regular burp.

[mx54life]

It's a single pop from 1st-2nd and 2nd-3rd only on hard acceleration. No loss of power noted.

[DK Wolf]

I wouldn't worry in that case.

[Chops]

It's a single pop from 1st-2nd and 2nd-3rd only on hard acceleration. No loss of power noted.

My bone stock '02 used to do that through my RacingBeat axle-back muffler. Just one solid "pop" as soon as the revs started to drop when I pushed in the clutch, and that was under moderate acceleration up to 4k or so. I could usually repeat it every time if I wanted to. My little '91 doesn't do this at all though, even with a full exhaust from the engine back.

[mx54life]

Funny I do have a RacingBeat exhaust system. I wonder if this is inherent in their design.

[SM16RMSM]

It backfiring between shifts then? It normal and it won't hurt anything. What causing it is excess fuel not being burned. It caused by the Power Card tricking the ECU to add more fuel. Now your running rich and it causing it to backfire in the lower gears. In a longer pull/taller gear, it burning the extra gas and not causing a back fire. I don't know much about the Power Cards but someone should be able to tell a bit more in detail.

My Mazdaspeed Miata will backfire every now and then from time to time. It usually caused when idling for a extended period. When driving hard, no backfire. When stopped at a really long light and I drive away, it will backfire in the 1st to 2nd gear.

[mx54life]

It backfiring between shifts then? It normal and it won't hurt anything. What causing it is excess fuel not being burned. It caused by the Power Card tricking the ECU to add more fuel. Now your running rich and it causing it to backfire in the lower gears. In a longer pull/taller gear, it burning the extra gas and not causing a back fire. I don't know much about the Power Cards but someone should be able to tell a bit more in detail.

My Mazdaspeed Miata will backfire every now and then from time to time. It usually caused when idling for a extended period. When driving hard, no backfire. When stopped at a really long light and I drive away, it will backfire in the 1st to 2nd gear.

So excess gas is not a problem? Which one is better then. Powercard or FPR?

[mx54life]

Update: So I drove her this AM and surprisingly no popping on any gears. Does cool air temp improves fuel mixture? When I first experience the popping I recall it was around 80's deg.

[SM16RMSM]

So excess gas is not a problem? Which one is better then. Powercard or FPR?

Excess gas won't hurt anything. Highly tuned race cars will backfire all the time. The MP45 is the smaller supercharger for our cars and a FPR isn't really needed unless your going to run bigger injectors or a bigger supercharger. You could be able to tune the backfire with a adjustable power card and a wideband air/fuel ratio gauge.

In all honesty, I would stick with the PowerCard with the MP45 supercharger. If you ever decide to go with the MP62 or the Rotex (I would personally go with the Rotex) then look into a standalone ECU. The best bang for buck ECU is MegaSquirt. Only problem is that it not Cali legal. It won't pass smog. To pass emissions, I would switch back to the stock ecu, stock injectors, and a power card just to pass emissions. It only once a year. Once your done, just switch everthing back over and your done. I few of the MSM on M-S run MegaSquirts and Hydra. They will swap out the aftermarket ECU and pass emissions. Once done, all the goodies go back in.

Update: So I drove her this AM and surprisingly no popping on any gears. Does cool air temp improves fuel mixture? When I first experience the popping I recall it was around 80's deg.

The cooler the air, the more dense the air is and it has more oxygen. With more oxygen in the more with the set fuel ratio given to the PowerCard, you won't hear the backfire since the A/F ratio is now correct. Once the air warms up, there is less oxygen.

[mx54life]

Excess gas won't hurt anything. Highly tuned race cars will backfire all the time. The MP45 is the smaller supercharger for our cars and a FPR isn't really needed unless your going to run bigger injectors or a bigger supercharger. You could be able to tune the backfire with a adjustable power card and a wideband air/fuel ratio gauge.

In all honesty, I would stick with the PowerCard with the MP45 supercharger. If you ever decide to go with the MP62 or the Rotex (I would personally go with the Rotex) then look into a standalone ECU. The best bang for buck ECU is MegaSquirt. Only problem is that it not Cali legal. It won't pass smog. To pass emissions, I would switch back to the stock ecu, stock injectors, and a power card just to pass emissions. It only once a year. Once your done, just switch everthing back over and your done. I few of the MSM on M-S run MegaSquirts and Hydra. They will swap out the aftermarket ECU and pass emissions. Once done, all the goodies go back in.



The cooler the air, the more dense the air is and it has more oxygen. With more oxygen in the more with the set fuel ratio given to the PowerCard, you won't hear the backfire since the A/F ratio is now correct. Once the air warms up, there is less oxygen.

Thank you for the wisdom. So would you think I would be better served by an adjustable powercard? What I have now is the non-adjustable one. I also ordered a wideband O2 this AM.

[SM16RMSM]

I hoping someone else with chime in with more knowledge. What I know is from reading up on turbo cars. In all honesty, I really think you can trim the fuel curve to get the backfire to stop by trim less fuel out. But you will lose a bit of WHP. It a double edge sword. For daily driving, it really shouldn't matter. but when you go out to play, bump the fuel up a few clicks and go for it.

[mx54life]

I hoping someone else with chime in with more knowledge. What I know is from reading up on turbo cars. In all honesty, I really think you can trim the fuel curve to get the backfire to stop by trim less fuel out. But you will lose a bit of WHP. It a double edge sword. For daily driving, it really shouldn't matter. but when you go out to play, bump the fuel up a few clicks and go for it.

Right there is a certain degree of compromise. I will eventually get an adjustable card. For now I think it is running pretty good. Thanks again.