Backfire

[Bruce Plecan]

Some times, it's gonna be a normal event.
Unless you totally shut the fuel off.
Matter of fact some should be normal, just a hint of a crackle that is, when
your decclerating.
If you want the DFCO, fine, just rmember the chambers are cold, and no EGT
so you have no to little exhuast gas energy.  Which you want, if you the
kinda guy the does some spirited driving.
Headers allow for alot more noise to be transmitted.
  Course an exhuast leak will make for a good popping, during over run.
Very tiny one will do it.
There are several very distict reasons for it.   Too much fuel, to little
fuel, to much timing or too little timing.
Like I said I like to turn down the timing and somewhat the fuel on overun.
HTH
Bruce




> I have a slight popping or backfire when I downshift and sometimes let up
on the throttle. I got the BLM's to all come within + - 4 of 128 from idle
to 5500 RPM. This problem wasn't there when I had the, dare I say it, Carb
on it, once I put the TPI on I started to get it. The car runs great, pulls
hard through all the gears plugs look good but I can only get rid of the
Popping or backfire if I crank up the initial timing even then I still get a
little.
>
> Is this because of the inertial supercharging effect of the TPI and I am
getting a lean pop because of all the air blowing through when the throttle
is closed and the motor is still revving at a higher RPM and not as much if
any fuel is being delivered?
>
> Specs on the application are
>
> 68 - Camaro 327 Stock
> 87 TPI from a Camaro running stock F-body Code except for the
modifications to get the BLM's correct
> Screens removed from Mass air
> K&N Air filter
> 50 PSI Fuel pressure on 19Lbs injectors
> Headers
> Dual Exhaust with glass packs (soon to be removed) no cross over
> Converted over O2 Sensor to 3 wire heated design
>
> Thanks in advance
>
> Todd
>
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