How are you 96lb injectors at idle??

[Redline Motorsports]

Been playing with a TT C5 with 96lb/hr injectors. Seems like no matter what we did the A/F was alway very rich. The rest of the fuel curve, cruising and WOT is on the money. Are just an problem or are there some tricks? Idle quality seemed fine despite the richer idle. It is too much injector for this car anyway but regardless its an idle problem.

Any tips?

[Delco]

Been playing with a TT C5 with 96lb/hr injectors. Seems like no matter what we did the A/F was alway very rich. The rest of the fuel curve, cruising and WOT is on the money. Are just an problem or are there some tricks? Idle quality seemed fine despite the richer idle. It is too much injector for this car anyway but regardless its an idle problem.

Any tips?

the injectors will have a min pulse width that they will operate at physically,even though you try and drive then lower they will not especially if you are using a driver box that will also have a min opening time. you will find no matter what you do the engine will want less than this to run at the right mixture at idle , with big injectora you can loose control of stuff like this , may have to drop fuel pressure at low rpm to enable you to get idle control and part throttle control

[Redline Motorsports]

Thats what I figured... I did changed the min. pulse width time and it had no effect. Like I said this car could have got away with a 60's which most likely would not have the same problems. I never thought about the driver having a minimum threshold.........

Thanks

[nco663]

A simplistic way to look at injector sizing is;

you can't open too small injectors big enough

and

you can't close too big injectors small enough

[MN C5]

Redline, I've compensated with fuel pressure using a variable boost referenced fuel pressure regulator. It's a little harder to tune because the fuel pressure is rising faster than the boost but it allows you to make the beast idle. Its not the right way to do it but it works.


http://www.holley.com/data/Products/.../199R10101.pdf