I知 street tuning my car and I知 getting low rpm back fires. The engine is a lsx454 solid roller 258/272 cam on a speed density tune, E38pcm
Above 2500rpm the tunes sweet, I get back fires coasting down, I知 thinking because there so much overlap on the cam I知 getting lean back fires.
Does tht sound rite?
How do I dial the tune in with lots of overlap?

 

Maybe your tuner has left "Decel Fuel Cutoff" turned off in the operating system??? In other words, he left the fuel running just a little during engine coasting for deceleration. This can be turned off if you don't like the exhaust burbling a little.

Rick

 

im the street tuning myself. I知 running off the short term fuel trims. But I really can稚 use them under 2500rpm dueto the amount of overlap. I知 wanting to know the correct way to tune when you do have so much overlap. I have 38ｰ overlap

 

Can anyone give me advice on this?

 

I'm not a tuner but it seems if you want good street manners you'd pick a cam with less overlap.

 

Enable DFCO then see what it does.

 

Yes I agree that if you want to hv good street manners , go with less overlap
Im not interested in street manners, I would just like some advice on how to best tune your car for low rpm when you hv lots of overlap
I値l just go back to tune 1 and copy and paste paste everything under 2500rpm. That will fix it

 

Dfco is good, I think I must hv smoothed tune below 2500rpm, before it had no backfire

 

I had similar issues with my setup, a 454 LS with a 239/251 @ 114 cam, and P59 PCM.

Enabling DFCO helps a lot, but it takes a second for the fuel to cut off, so it's a necessary step but not entirely sufficient. Disable throttle cracker was the other key thing, it made a huge difference.

Disabling throttle cracker then screwed up return-to-idle, and the fix for that was a setting that causes adaptive idle to kick in at about 1500 RPM, so that it can handle the transition to idle proactively instead of just reactively.

It's all good now. No pop/bang on decel, and consistent return-to-idle.