Trying to decide on what kind of fuel system (specifically injectors) are required for a low 10 second n/a car. So far the car is equipped with an Aeromotive 1000hp fuel pump and -8 to the rail. We need to know what injectors will be sufficient. Will 55's be enough? What size injector options are out there for the low 10 n/a cars?

I would like to hear some thoughts on engine (computer) management. We are using the stock computer and are looking for some good computer programmers out there. The car will be equipped with a Translator+ for fuel and spark adjustability. Is there anyone out there that you suggest or don't suggest? We are planning on using Ed Wright. Any thoughts on Ed? Thanks again fellas.

 

To get HP from ET or MPH estimate, you need the race weight of the vehicle.

Assuming 3,200#, you need 650flyHP to run 10.1@135mph. Assuming the ususal 0.50 #/HR/HP BSFC, and an 80% duty cycle on the injectors, you need to supply at least 51#/HR with each injector. If you got some 3bar injectors and ran them at 4bar (58psi) you could get away with 44#/HR.

Bigger isn't always better on the fuel supply line... a -10AN has a huge "mass" of fuel in it, and when you launch hard and pull a couple G's, your going to see that entire mass of fuel fighting the pressure on the pump discharge. You will get a loss of pressure right when you need max flow. I run 800flyHP through a -6AN supply line and a -6AN return. And that's a fuel hungry dry nitrous motor.

 

Race weight should be 2900 - 3000lbs. Flywheel HP is estimated at 670 carbed. The engine builder has been extremely accurate on HP estimations within 5-10% on every engine he has built for us.

I need to make a correction on the fuel supply line. The size is -10 to the pump, and -8 to the rail. I believe -6 return.

Assuming a set of 50lb injectors (MSD50's) are used with a stock computer, will that be sufficient? Thanks for your reply injuneer.

 

I think 50#/HR should be fine, with a good tune. If you need a little more after seeing the dyno results, you boost the pressure a little. A 20% increase in pressure nets you almost 10% more injector flow.

Are you running high impedance injectors, or do you have the "black box" to run low impedance injectors on the stock PCM?

Im confused though.....

Carbed??????

 

MSD50's are high imp. injectors.

The flywheel HP estimation is carbed because it would ensure a close to perfect tune. So many variables with a fuel injected motor that will affect the outcome of the HP. He says carbed to give you an idea of what a perfect tune would net. Does this make sense?

We dont want to be borderline on injectors. If it would be wise to use something larger like 55's then we will do so. Let me know what you think. Thanks again.

 

There is no downside to an "oversize" injector, except possibly idle quality. I do not know what the limits are for the stock PCM, either with regard to the largest possible injector constant, or the ability to achieve less than 1mS pulse widths at idle. I doubt that you are worried about idle quality, however.

I run 64# Bosch injectors at 58psi (= 74#/HR) and my lowly 500HP NA 381 idles like a kitten. Then with a full shot of juice, the duty cycle is barely 70%. But I wouldn't attempt that with the stock PCM.....

 

What do you use for engine management?