On Tue, 16 Jan 1996, Todd Mullins wrote:
>
> New question: Backfiring. I don't quite understand it. My exhaust
> makes a raspy, popping sound upon overrun. I had assumed that it was
> unburnt fuel travelling through the pipe and exploding when it
> encountered the outside air. Others have told me that backfiring is due
> to a lean mixture. Which is right? I believe my carbs (dual HIF4s) are
Both. Rich mixture tends to pop out the tailpipe, while lean pops back
through the carbs. I call the latter "frontfire", although nobody else
does <grin>.
I'm not sure about the bit of it traveling all through the tailpipe
before exploding, I think it happens when raw fuel hits the hot exhaust
manifold. But I've been wrong before.
> valve is operative, I can't think of anything else that might cause
> backfiring (I have solid throttle plates). Any gurus? Denise?
>
Well, the reason those silly buttons were put on the throttle
plates was to prevent overly rich mixture on trailing throttle. Aha! I
must say though that I have replaced my plates with solid ones and have
no backfiring problem (frontfire while the engine is cold, oh yes).
John M. Trindle | jtrindle@tsquare.com | Tidewater Sports Car Club
'73 MGB DSP | '69 Spitfire E Stock | '88 RX-7 C Stock
|