Well I called Rc Eng and they said that the 500cc would be to big for the AFC to handle, going from 250 stock to 500 was more then a %50 change. SO I asked some othere people and I belive someone said 550 were teh max teh AFC could handle in our cars. So my q's is who here other then Chris M have the AFC and bigger injectors?? I plan on ordering all this stuf here this Fri and was going to upgrade to stage 3 but figured why spend extra cash on the fuel controller when I have the AFC but if I can't run 440cc which now I'm hearing I can't either, but sure I can, then I might as well fork out teh extra cash for the 500 and HRC fuel module. ANy suggestions, Ideas, something.....
#1118, "RE: Afc Usere and Injectors q's" In response to Reply # 0
Thats strainge! Cause when I orderd my 440's, RC just ask me two questions. What are you going to use to control these? answer"S-AFC". And you are planning on going turbo right? Answer"yes". So I dont know what the prob is for you! if it was no problem for me. HUMMMM! Let me know what you find out. SEE YA!!!!!!!!MWC
#1120, "RE: Afc Usere and Injectors q's" In response to Reply # 2
what kind of math are you doing on that and what are you using for your baseline injector size?
last time i talked with RC engineering, the tech looked up the stock injector size on the 420A and it was 234cc.
234cc to 440cc = 88% larger 234cc to 500cc = 113% larger 234cc to 550cc = 135% larger
he said that the stock ECU can compensate for about a 20% increase in injector size. no more. that means anything larger than a 280cc injector would run rich at idle. if you need to go bigger, you'll need an AFC. I'm not sure what the limits of the AFC are though. i never called their tech department.
#1121, "They Need to get the crap together" In response to Reply # 3
Sounds like everyone is getting different info. I've called them up a couple of times and they told me BOTH times that the largest injector we could go with would be a 320cc.
Here is another question. At what pressure did they (RC) test our injectors at for flow? I'm sure the only way they know the size of our injectors is by actaully testing them at there shop. If they tested them using 43psi (what all thei injectors use as pressure) then our injectors actually flow 275cc/min @50psi. That seems really big to be putting in a 2.0l 4 banger, but I dunno.
This is confusing stuff. If our cars can compensate for a +/-20% increase in injector size, why wouldn't a 500cc injector or even a 550 work.
Assuming RC Fuel pressure @43psi 235cc/min Stock injector 285cc/min Max Injector size RC engineering says we can handle (20% larger)
With use of a S-AFC +/-50% fuel adjustment 500cc/min --------- = 250cc/min - 2 @50% Adj
We are still within out 285cc/min injector size
how about 550cc/min 550cc/min --------- = 275cc/min 2 @50 Adj
Hmmm.. 275cc/min. Pretty close but I think we can do it. Specially since I have been told 2-3 times that our cars can actually compensate for a 320cc/min injector. I know there are people using 550cc/min injectors w/ S-AFC. I'm trying to find their e-mail addresses. I'd like to know if idle was maintained.
Another aproach would be to lower idle fuel pressure. This would solve a lot of problems. Plus, you could still set your Adj FMU ratio that gave you the fuel pressure you need at peak boost.
Those are my thoughts. I'm getting 500cc/min injectors here pretty soon (don't know when ) but I'm going to run them (hopefully) with the AFC and when race season really starts up over here I'm converting to either HRC's (if they sell it separate someday) EFI system or the Haltech. I'm leaning toward the Haltech simply because a lot of people have it and everyone who I talk to says to go Haltech rather than the "half programable" system the HRC sytem is. I dunno, its still up in the air. I wish Howell would get their programable ECU out for us. That would be awesome!
#1122, "RE: They Need to get the crap together" In response to Reply # 4
wyatt, you're right. RC does rate their injectors at 43 psi. so that 234cc is most likely at 43 psi. but so are all their other injectors. the 320's, 440's, 500's, whatever. they're all rated for that flow at 43 psi. there is a simple calculation that will tell you what the flow would be at a higher pressure. increasing fuel pressure from 43 psi to 49 psi would only make the 234's flow 249cc's. that's not much of a difference. of course there is more of a difference if you were to increase fuel pressure with a boost-sensitive FPR.
550's are some seriously BIG injectors. i didn't run the calculations on RC's site, but i'd imagine that they're overkill unless you're planning on running MAD boost. all you have to do is know what kind of boost you plan on running, estimate the HP output with that boost, and calculate the right size injector. if that calculation tells you to get 550cc injectors, keep in mind that it's calling for 550's running at 43 psi!
if you have the fuel pressure cranked up under boost, you might only need 440's to flow 550cc/min. that's where you have to play with the numbers and see what injector flows what at what psi. sharpen your pencils and get some scrap paper. it's alot of fun!
#1123, "RE: They Need to get the crap together" In response to Reply # 4
LAST EDITED ON 23-Jan-01 AT 07:23 PM (PST)
I just used a commom fuel pressure of 50, since I've seeen it vary from about 48-54psi @ 50psi of fuel pressure RC's rate of 235cc/min changes to about 274cc/min for our cars
50/43=1.162 1.162x235cc/min = 274cc/min Thats were I got my numbers from.
Yes, I think thats the best solution to our problems. Lower idle fuel pressure of the 500cc/min or even 550's and use the FPR to raise fuel pressure under boost. or even better, ditch the FPR completly, get some 820cc/min injectors and let your PMS handle everything Man I wish our ECU'su were re-programable! come'on Howell, through me a bone!
On paper, we could theoretically handle close to 400hp using 550cc/min injectors running at 90psi of fuel pressure and still not go above 80% duty cycle.
#1124, "RE: Injector size + pressure" In response to Reply # 6
I think one thing that we need to keep in mind is that we should not be running much above 80% duty. I believe part of the reason why we tend to detonate at higher boost is because we are running these massive 12:1 FMU's and small injects 234cc..
So lets look at it this way : 234cc @ 43psi = 272cc @ 50psi (our cars) Now to make things more interesting lets throw in some boost, with along with a 12:1 FMU ! Correct me if im wrong but 8psi should put us right around 100psi. +/- a few psi.. (2.325 ratio) 100psi 8psi boost = 544cc ...which is 184% duty cycle !! Injector lockup galore !! --hehehe
#1125, "HRC does sell the accell by itself." In response to Reply # 7
i had asked them about it. It's about 1500 they said, which would be 625 cc injectors, the accel unit, and a 1:1 regulator. Not bad to be able to run mad amounts of boost.
Wyatt, who all have you heard has the haltech, no one with a 420A right? I don't know of anyone with one yet. I hope to be that first one soon.
#1126, "RE: Afc Usere and Injectors q's" In response to Reply # 2
>That's because 440cc's is less than >50% larger than are 500c's >and above.
234cc x 0.5 = 117cc // 234 + 117 = 351cc !! There is your proof that you can run 320cc's on stock ECU ! Im curious if running 400cc injectors and slightly lower idle fuel pressure would be sufficient w/o a S-AFC ! ???
#1128, "RE: Afc Usere and Injectors q's" In response to Reply # 10
LAST EDITED ON 24-Jan-01 AT 10:35 AM (PST)
>wyatt, how did you come up >with those numbers?? i >calculated that a 235cc injector >(@43psi) would flow 253cc's (@50psi) > I'ma retard, I didn't to my sq root nevermind, all my data is screwed. I need to go back to math class. Duh.............
#1129, "RE: Afc Usere and Injectors q's" In response to Reply # 9
>>That's because 440cc's is less than >>50% larger than are 500c's >>and above. > >234cc x 0.5 = 117cc // >234 + 117 = 351cc >!! >There is your proof that you >can run 320cc's on stock >ECU ! >Im curious if running 400cc injectors >and slightly lower idle fuel >pressure would be sufficient w/o >a S-AFC ! ??? > >Any ideas on this one ?? > So, your saying if I change my AFC settings to +26% adjustment @ idle, that would simulate a 320cc/min injector? I'll have to try that. Although I don't know if its a direct correlation between air pressure and fuel cc/min. Hopefully is does what I think its going to do and even @ +26% adjustment the ECU leans back down the ratio so it can idle.
#1132, "RE: Afc Usere and Injectors q's" In response to Reply # 11
I'm grabbing the 440's, Chris M is running 400cc and leans them out at about -10 across teh board, So I think the 440cc will be fine, if not, I'll get the 400cc, thanks guys.
#1133, "RE: Afc Usere and Injectors q's" In response to Reply # 12
My 440's came in today and I hope to have them installed in the next week or two. I will post my results of the turbo install as well. SEE YA!!!!!!!!MWC
) but I'm going to run them (hopefully) with the AFC and when race season really starts up over here I'm converting to either HRC's (if they sell it separate someday) EFI system or the Haltech. I'm leaning toward the Haltech simply because a lot of people have it and everyone who I talk to says to go Haltech rather than the "half programable" system the HRC sytem is. I dunno, its still up in the air. 
