Anybody have any opinions on injector sizes for the primary and secondaries for a rebuilt motor with porting, 3mm apex seals, to4 turbocharger, etc....

Are four 720's enough or do the secondaries need to be bigger, so the motor will not lean out.

Thanks guys

 

A good rule of thumb is 8cc/min per flywheel kW. Then divide fuel by 0.8 (or multiply power by 0.8) so you don't exceed 80% injector duty cycle. So 4 x 720cc/min = 2880cc/min = 360kW = ~480hp @ 100% duty or ~385hp @ 80%. The stock 550's should be good for around 295hp. These are all flywheel figures remember.

 

My experience...
Stock 4x550's can barely handle 250bhp at the flywheel.
4x720's should be good to 350bhp at the flywheel.
This is going with the 80%-85% safe fuel injector pulsewidth under the stock fuel rail pressure of 35psi.

You can gain more power potential by going with an aftermarket FPR and raising the fuel rail pressure (max 70psi).



-Ted

 

I agree. If you run that turbo at it's power potential, the injectors will be hitting close to 100% duty cycle. Keep in mind not all pumps flow well at higher rail pressures. I would run 1300s in the secondaries. 70 - 20 psi (where efficiency of a t04 drops) = 50 psi fuel pressure. It's better not to stress the fuel system.

 

they have a fuel calculator at rx7.com that might help

 

http://www.rceng.com/technical.htm