Backfire

[chipsndukes]

Well, I just introduced myself, in the other section.
I am not new to ecomodding, I have been "lurking" for a while and trying my hand at saving fuel.

I wanted to post, because something interesting happened yesterday:

I was driving out of a tight curve with the engine off, bumped it on a short straight and then shut down again for a tight left-hander.
It was uphill, and with someone behind me, I quick bumped the engine again...BOOM.

The person in front of me nearly stopped dead and I had to brake, the person behind me backed off. Nobody knew what happened, just that it was LOUD.

I know that it is possible to cause a backfire because of raw fuel in the exhaust system, but I thought that wouldn't happen, because when the ignition is turned off, the injectors close, right?

In a year, this has never happened to me, but I thought I would kindly ask for your comments!

Chipsndukes

[The Atomic Ass]

Originally Posted by chipsndukes

Well, I just introduced myself, in the other section.
I am not new to ecomodding, I have been "lurking" for a while and trying my hand at saving fuel.

I wanted to post, because something interesting happened yesterday:

I was driving out of a tight curve with the engine off, bumped it on a short straight and then shut down again for a tight left-hander.
It was uphill, and with someone behind me, I quick bumped the engine again...BOOM.

The person in front of me nearly stopped dead and I had to brake, the person behind me backed off. Nobody knew what happened, just that it was LOUD.

I know that it is possible to cause a backfire because of raw fuel in the exhaust system, but I thought that wouldn't happen, because when the ignition is turned off, the injectors close, right?

In 1 1/2 years, this has never happened to me, but I thought I would kindly ask for your comments!

Chipsndukes

In a multi-cylinder engine, fuel can be injected into a cylinder prior to shut off, and the shut off happens prior to that same cylinder getting spark ignition. As a matter of fact, it's probably going to happen every single time, with 4 cylinders. Although it was probably the quick stop-start routine that allowed enough fuel to collect to cause the backfire.

I'd recommend installing a kill switch!

[chipsndukes]

Originally Posted by The Atomic Ass

I'd recommend installing a kill switch!

Thank you very much Atomic.

How would the kill switch help to prevent a backfire?

Thanks!
Chipsndukes

[The Atomic Ass]

Originally Posted by chipsndukes

Thank you very much Atomic.

How would the kill switch help to prevent a backfire?

Thanks!
Chipsndukes

When you key off, the computer stops the spark and fuel simultaneously. With a kill switch, if wired properly, it kills just the injectors, keeping the spark going, igniting any left over fuel in the last few revolutions before the engine comes to a complete stop.

[chipsndukes]

Originally Posted by The Atomic Ass

When you key off, the computer stops the spark and fuel simultaneously. With a kill switch, if wired properly, it kills just the injectors, keeping the spark going, igniting any left over fuel in the last few revolutions before the engine comes to a complete stop.

OK, thank you very much, that makes sense.

Chipsndukes