What size injectors????

[nickmpower]

what size injectors do you guys think i should run??? ive got stock, 19's, 21's and 24's to choose from. I have a 2.1 liter motor with reground cams and ported 3 angle head. I recall febi using 24's with a higher fuel pressure but that seems like too much. Using the displacment the 21s seem like they will be the best match.

[Febi Guibo]

Jah, it was a precautionary thing to avoid leaning out, although I've had no problems and my fuel economy actually went up a bit.

Do you have one of those lambda (a/f ratio) meters? that will pretty much tell the whole story.

[nickmpower]

yes, but i dont want to have to keep taking the manifold on and off. are you sure they are 24's?

[nickmpower]

A guy on bimmer forums installed 21's i think in his motor that he did high comp cams and worked head, but no change in displacment and his wouldnt even run.

But i guess im going to go with the 24's, any more opinions?

[BrandC]

Just do homework on some 2.0L vehicles with similar compression. See what fuel pressure and injectors they are running, especially if they are tuned engines.

[nickmpower]

it seems the s14's are about 22.5, so maybe i should go with the 21.5's

[Gunni]

What HP range does your engine cover?
Then I´ll tell you what to get

[nickmpower]

i have no idea. id guess a little less then the s14 at this point.

m47 crank, 86.5mm pistons, 10:1 compression (i may get a dasc in the future plus i want the engine to last a long time) lightly ported head, 3 angle valve job, metric mechainc springs and retainers, lightweight lifters. supersprint replica header, reground cams but will upgrade to metric mechanic eventually, plus a miller MAF real soon. every moving/wear part replacd.

[Gunni]

so your hoping for about 200hp?
Use the 24´s.
the others are just to small for that level.

[nickmpower]

im guessing it will probably be 180-190

[bmwman91]

The stockers are 20.35# units. They seem to be good up to ~155bhp. Just going on the assumed increase in power...

(X#/20.35#)= (190bhp/155bhp)
=> X = (190bhp/155bhp)*20.35# = 24.9#

So, usung the ratios (crude way of doing it), you should look for some 25# ones. 190bhp would probably be about their limit. Hope this helps.

[vjlax18]

Built S52's run 24# up to 100hp/ltr, so the M42 which is a baby M50 should run the same with 95hp/ltr

[nobrakese36]

24 seems a little big, i talked to ireland eng. They said stock 19 or 20 lbr's are fine with higher fuel pressure.

[Tor Arne Kaasen]

200 hk = 277cm3 #26,3 190hk = 263cm3 #25 etc. this is at 90%
140hk =#18,51 194cm3
19 or 20 Lbr at 4 bar = 165hk to smal for 200hk