SAFC and 50Trim. 650 or 750cc?

[DSMJim]

I have 550cc now and anything over 15psi on my 50Trim my timing is getting pulled

I have a SAFC for fuel control. I have seen guys with both 650cc and 750cc injectors using a SAFC but have heard of problems with the 750cc and idling etc..

Does anybody out there have some first hand experience with the 750cc and SAFC that they can share? I really want to get the largest injectors possible which would in this case be the 750cc but dont want to end up with a car that idles like crap because of it. I want to run between 20-22psi on pump gas (94 octane here)

 

[peregrine]

650's. 750s are big.

 

[swordfish]

The 650's should be fine. You could do 750's but would have a problem taking enough fuel out on race gas to get the AF's where you want them. The reason the ND style 720's idle a bit rough is that they have a Dead Time of 405 usecs whereas the 750's are down around 330-340 usecs. 550's and 650 or 660's have a dead time of 180 usecs roughly.

jeff

 

[mlopez]

Try 720's. I run them with my 57trim and safc. It idles great.

 

[candela]

Run them in what

H LLA....

 

[KRAZYKOREAN]

Originally posted by candela


H LLA....

 

[TellschAWD]

Don’t be afraid to mess with the base fuel pressure. Bump the base up and you can make a 550 injector a lot bigger than 550. You should be able to get 17psi by simply doing that with your existing setup.

I would go no bigger than 650's.

 

[KRAZYKOREAN]

Originally posted by TellschAWD
Don’t be afraid to mess with the base fuel pressure. Bump the base up and you can make a 550 injector a lot bigger than 550. You should be able to get 17psi by simply doing that with your existing setup.

I would go no bigger than 650's.

Do you understand how injectors works.....be afraid to bump up your fuel pressure...all that is doing is going to make your injectors work alot harder....on a 50 trim turbo the 550 will be maxed...and they would be at a very high duty cycle....like Mlopez says 720 are good...or 680 thats what I got with my 50 trim from extremepsi.com and they work good to...also with bigger injectors it gives you more lee way and more room to work with....my idling is perfect with 680...but 550 are to to to small...

 

[candela]

Holla....

 

[LandoAWD]

Word.

 

[jdmawd]

Originally posted by candela
Holla....

 

[swordfish]

Originally posted by KRAZYKOREAN


Do you understand how injectors works.....be afraid to bump up your fuel pressure...all that is doing is going to make your injectors work alot harder....on a 50 trim turbo the 550 will be maxed...and they would be at a very high duty cycle....like Mlopez says 720 are good...or 680 thats what I got with my 50 trim from extremepsi.com and they work good to...also with bigger injectors it gives you more lee way and more room to work with....my idling is perfect with 680...but 550 are to to to small...

Krazy, not to be an ass or anything, but do you know who you are correcting here? You should listen to him or at least give him a bit of respect. He knows a thing or two about a thing or two.

jeff

 

[mlopez]

Originally posted by candela


H LLA....

Ghey

 

[KRAZYKOREAN]

Originally posted by swordfish


Krazy, not to be an ass or anything, but do you know who you are correcting here? You should listen to him or at least give him a bit of respect. He knows a thing or two about a thing or two.

jeff

I give everyone respect on everything..but IMO I do not think just raising the fuel pressure when having 550c injectors for a 50 trim turbo..is not going to be suitable...or even recommened.but whatever the guy wants to do its his car...and I apologize if I seemed like I came off as a ass or anything..

 

[DSMJim]

No I dont plan on jacking my base fuel pressure, thats a band-aid way of fixing the problem of needing larger injectors. I have been through 3 other turbo cars and running heavy shots of nitrous so modifying cars and going fast is certinately not new to me.

Im just wondering if anybody with a SAFC has 750cc injectors and has their car running properly with a smooth idle etc etc. If there are a few cases then I will buy them, however i am not going to pioneer this on my car if nobody else has done it.

 

[brads]

Originally posted by DSMJim
No I dont plan on jacking my base fuel pressure, thats a band-aid way of fixing the problem of needing larger injectors.

And if you think the SAFC isn't just a bandaid, you have some reading to do. Adjusting fuel pressure is a very valid way of working with the other bandaid you already have, in order to try to adjust your fuel and timing. The AFC adjusts fuel and timing at the same time. The fuel pressure allows you to just tweak on fuel. So if you play with both, it gives you a little more chance to get good timing for you, with the correct amount of fuel delivery.

Also, have you looked at your injector duty cycles to make sure your timing retard at 15 PSI is due to maxing out the stock injectors? I had a timing retard at 15 PSI that was due to carbon buildup in the combustion chamber.

Brad

 

[bjgarvin]

for everybody with 550's who are thinking they need to go bigger.

http://www.dsmtuners.com/forums/showthread.php?postid=528482#post528482

http://www.dsmtuners.com/forums/showthread.php?postid=549991#post549991

read.

you will need the same supporting fuel system for either set of injectors flowing the same amount of fuel, meaning a big pump and an AFPR.

don't be afraid to bump your fuel pressure, if you have the flow.

Ben

 

[DSMJim]

Originally posted by brads


And if you think the SAFC isn't just a bandaid, you have some reading to do. Adjusting fuel pressure is a very valid way of working with the other bandaid you already have, in order to try to adjust your fuel and timing. The AFC adjusts fuel and timing at the same time. The fuel pressure allows you to just tweak on fuel. So if you play with both, it gives you a little more chance to get good timing for you, with the correct amount of fuel delivery.

Also, have you looked at your injector duty cycles to make sure your timing retard at 15 PSI is due to maxing out the stock injectors? I had a timing retard at 15 PSI that was due to carbon buildup in the combustion chamber.

Brad

True SAFC is a bandaid solution as well. I can not log my injector duty cycles on a 2G unfortunately.

I think I will end up with 650cc instead of 750cc. With 650 and a bump in the base fuel pressure that should be enough fuel to handle my turbo. 550cc are too small now, the car runs like a champ at 15psi but crapola at 20psi....

 

[webbdog]

For reference I run 650's, a 190 pump and an AFC on my 50 trim at 20 psi on pump gas with no problems.

 

[L2RTSiAWD]

650 ball/disc,AFC,50-trim-no problem at 20psi.

 

[FastRthenU]

Im in the same problem. I have a 50 trim with 550, and they dont cut it at all, not even close. I tryed to bump fuel pressure, but it had to be like 65 base to run 20 psi. Even then the injectors were maxed right out. Im thinking of buying 870cc injectors. I think there a little big but, i think i can control them

 

[KRAZYKOREAN]

Dude 870 are so much more then you need...way to much...IMO just get around 650-720 and you will be fine....or get the 870 its your decision and car..

 

[DSMJim]

Well I ordered my 650cc injectors and Im going to run 50psi for base fuel pressure instead of 43 as it is right now. THat should get me near what say a 690-700cc injector sizeing. Hopefully I can get a nice idle and enough fuel with that setup. Kinda sucks having all that turbo on my car and no injector.

Anyways I will report my findings and how things go after it's all done.

 

[webbdog]

Originally posted by DSMJim
Well I ordered my 650cc injectors and Im going to run 50psi for base fuel pressure instead of 43 as it is right now. THat should get me near what say a 690-700cc injector sizeing. Hopefully I can get a nice idle and enough fuel with that setup. Kinda sucks having all that turbo on my car and no injector.

Anyways I will report my findings and how things go after it's all done.

I'd run em at the stock fuel pressure first. If you need more fuel, then you can bump it up.

 

[FastRthenU]

I know 870cc injectors are overkill for the turbo. But im planning on going bigger next year. I can run them on my Super AFR.

450/870 -1 =.48 Which means i have to take out 48% out of my stock fuel maps. So i can run them for my application. Plus they will be great for what i want to get next

The only time that im going to have problems is with idle. But I can take out over 80% fuel at idle. So i think they should work great. Plus i will get awsome timing maps

I also have the choice of lowering my stock fuel pressure. So all in all, it should be fine.