daddyov8

Hi all,

Any recommendations for injector size and make/model for approx 5-6-8lb of boost.

Any ideas what the max airflow is either at std or at any boost level.

Thanks in advance,

tveltman

I think it makes a difference whether you are talking supercharger or turbocharger (turbo should consume less fuel to power the compressor than the belt-driven supercharger), and whether this is intercooled or not, but my guess is most people will tell you 36# or higher. Airflow is easy to calculate, just google for it and you will find calculators online. I don't know what the volumetric efficiency is of the 928 (as though it were even constant throughout the RPM range of the engine), but if you assume 100% (which is definitely not it), then you won't under-fuel it. Also boost means you will be needing to tune it after the install, so as long as your injectors are about right, the tune should take care of the rest. Dr. Google is your friend.

dprantl

I would just put in 42lb injectors (actually, I did). That way you have room to upgrade in the future, which you most probably will be doing anyway. On my intercooled eaton M112 with 8.5psi at sea level I hit 70% duty cycle on my 42lb injectors in normal mode. For an '87+ 928, you would need Ford Motorsports M9593-F302 (http://blueovalindustries.bluekeyinc...ts.php?pid=574).

Dan
'91 928GT S/C 475hp/460lb.ft

IcemanG17

what model 928 do you have?

Without knowing which you have...its really hard to guess...

daddyov8

Thanks, its an row 89 s4.

44 look good, were the ford ones a straight fit or did this require drilling or a custom rail etc?

LEADASS

I've got the Murph Votec stage III kit and I have 42# ford injectors, there was no modification required.

LEADASS

P.S. I'm running 14.9 # of boost.

AO

There are two considerations, IMO.

One is max boost. If you think you'll only ever be hitting max boost of 8psi, then you might be able to get by with the Ford 33# injectors (or are they 36?). If you think you'll go above that, then I would say go with the 42#. They seem to work very well.

The other consideration is how you are managing the boost. If you are using a shark tuner, then I would say the 42# injectors is the way to go as you can tune them for descent idle and low throttle response. If you are using a begi or other RRFPR, along with stock chips, then you may want to stay with stock chips or go up one level to 24#.

victor25

What AO says... 24's will work will up to about 6psi of boost with no problem, after that you will need 36 or 42 lbs. The nice thing about 24's is that you can litterly drop them in, start the car with 6lbs of boost and drive away with no chip modification. But to do it all correctly you need a wide band and Shark tuner

daddyov8

cheers guys, planning for 8 to allow for future changes so 42's look promising. Planning on shark tuning, read much on here re stand alone efi and not sure it makes sense in terms of how much of a mod for little benefit but may change my mind on this as things go.
thanks for the help.