I guess this is a question for those with upgraded injectors....

I have RC 660's in my G and damn near every time I turn the key to fire her up she backfires uncontrollably loud. It isn't that terrible accept for the fact that some have been so serious that the throttle plate was bent in half like a Pringle because of it. I am just wondering how people can run 770's and beyond in Honda's and stuff without this problem. If anyone has any solutions I would love to save my motor and more throttle plates.

Thanks

 

I run 60lb~630cc injectors and it doesn't backfire or screw up throttle plates. The injectors fire "batch" at startup and then go sequencial. This causes a rich condition but shouldn't cause a backfire. Sounds more like a mechanical problem.

 

The issue is a rich idle (I believe) which leaves extra fuel in the cylinder on shut off......so when I come back to start an hour or so later the fuel has settled in the bottom of the cylider and when I turn the key to "on" the backfire occurs. So basically when the battery turns on it sparks the left over fuel. Any suggestions for leaning out the idle characteristics of 660's?

I knew about the rich condition at start up but I guess my concern is how to get the rich condition from occurring when the motor is shut off.

 

Would a Turbo Timer help?

 

Have one. IMO, that is where the fuel build up is occurring. When I let the turbo timer allow the car to sit at idle for an extended period of time it idles very rich and fuel builds up in the cylinders.

 

This is a 4 stroke engine and it is very unlikely that it is caused by what you are talking about. While the injectors fire batch the spark plugs fire in sequential order. Does it start up correctly on cold startup. If it does it probably has more to do with your headgasket and how it has thrown off your cam timing.

 

Interesting I do have a low compression Greddy head gasket in the motor. I just have trouble unsderstanding why it idles rich and backfires when the battery is switched to the "on" position.

 

I don't quite understand what you mean by "when the battery is switched to the "on" position"? What is your AF at idle? Trust me that at idle their is no fuel "building up" in the cylinders. Their just isn't any way unless a fuel injector is stuck open but then it would always sound like you have a dropped cyclinder.

 

Well the backfire occurs when the key is turned to "on" It's not when the car is cranked to turn on. When I sit in the car and turn the key to the point that all of the gauges and the radio come on, that is when the backfire occurs. I can't explain this phenomenon. There is some amount of fuel in the cylinder when the car is switched to "on" and it ignites and backfires in the cylinder.

It is definately a hard thing to describe because I am sure this does not happen all that often.

 

Post this over at my350z.com There are many more "tech heads" over there. I think it has something to do with your turbo timer. But even then I don't know how the car would be firing the ignition while the intake valve is open.

 

Eh....it was worth a shot. Thanks for the input!

 

Do you have Nitrous? If you do I would suspect a leaking solenoid. A gasoline explosion in the intake manifold should not be able to bend the throttle plate. A gasoline/nitrous explosion will very easily bend the plate as well as pop off hoses and/or crack the manifold.

 

No nitrous but some of the backfires are VERY violent. i.e. load and rumble the car. It's no fun. We think an injector is leaking when the car is shut off and is still under pressure. When left for a while the leak in the injector will puddle fuel in a cylinder and when I go to start her up BOOM! But yeah I need to post a pic of the throttle plate....it looks like a Pringle.