I was wondering on my 89 s5 turbo II motor I have a Haltech E8 and I have 1200cc secondaries and 750cc primaries. And I have a knightsports turbo. I was wondering how far can the Haltech E8 adjust the fuel injectors down. I am trying to see if I will need a adjustable fuel pressure regulator.

 

are you tring to run a non rising rate reg then as you boost up assume the fuel pressure drops (which you wont know accurately in different load combinations) and then adjust the injects flow rates to suit the reduced fuel pressures ?

**** that...

get a rising rate reg mate and dont have the head ****.

 

The Haltech will adjust the pulse width down to zero. Idle quality at a short pulse width is going to be a combination of injector quality and size and ECU injector driver quality. The stock pressure regulator works. It will draw down pressure under vacuum and is 1:1 rising rate. With the small turbo upgrade that you have the stock regulator should work fine and you should not have trouble idling the 750 injectors.

 

+1 these ECU's will still idle with 1000 cc rochester multech's with no issue, so modern 750's will be a breeze

for optimum response
you may have to go to the fuel setup screen and then to the injector current setup and alter that suit the injector grouping

ie divide 12 by the injector ohms to find out the injector current draw, then alter the setup suit the best selection