550's or 650's still not convinced

[Echo5Zulu]

Allright Ive been researching like mad for my new turbo set up but still have a couple things that I cant make up my mind about. I would like to get the opinions from those of you with similar setups.

First of all Im going with a MHI Evo3 16g or possibly the equivelant from Bullseye turbos. I tune with my safc II and palmtop datalogger. I have Walbro 255 pump with Aeromotive FPR regulator. Other mods are in my sig. as there are many. My goals are 300 to 350 horses.

My largest debate in my head is what size fuel injector to go with. Now before you say oh thats a common question run a search, hear me out.

I was thinking of running 550's because they are a step up and should be easy to tune with and not a huge jump. According to RC's injector calculator to hit 350hp I need to run 50psi of pressure, and inj. duty cycle of 93%

Now if I step up to 650's I can of course either run lower psi or stay at say 50psi and take it easy on inj. duty cycle. The problem Im having is that Im not sure the safc II can properly tune the 650's. Ive read a few articles explaining that people have had mad problems with knock on the 650's and safc II.

Now I would really like to hear from those of you running a first gen (second gen mass flow and gm mass flow characteristics are different so may not pertain to my situation) and a similar set up to what I will be running please speak up. If your running 650's did you have problems with the SAFC? If your on 550's what kind of times and power are you making. Also in both cases please state fuel pressure and injector pulse width you had to run. Thanks everyone and sorry it got lengthy.

 

[delta448]

Ever consider getting a keydiver chipped ECU?

I don't know first hand but have heard that 650s are difficult to tune for a good AFR and no knock at the same time with a SAFC. (Hopefully someone with some experience there will post for you.) Timing advance gets a little "edgey" with a correction percentage that high. If you chip the ECU, you'll be able to fine tune via the SAFC once you decide what base fp you want to use.

50psi of base fuel pressure is probably going to shorten injector life a little, especially considering that you'll be hitting such a high duty cycle if you use the 550s. Personally, I'd get a chip and run some 750s with a base fuel pressure of about 42psi. Then you still have a little room to grow, can still use your SAFC for fine tuning and you're not really pushing the limits of your injectors to reach your goal.

 

[xveganxcowboyx]

I'd think that your pump may have trouble keeping up with that fuel pressure. 50psi base plus 1:1 at say 20 psi adds up.

You could go with a second gen MAS and have corrections be closer on the AFC.

I've been enjoying my EVO injectors. They seemed like a good compromise between the two. They run closer to 600cc when you factor in dead time differences and whatever else. Mine are actually set to 620cc base right now and I'm still running rich.

 

[selmerguy]

I run 650's on my 1g awd. I use a MAFT and safc. I was messing around with my wideband when I was tuning ad I tuned the car (for fun) With the MAFT zeroed out and just the SAFC. It sucked. It is very hard to tune with just the safc on injectors that big. See with bigger injectors you have dead time. It takes them longer to open up you you have to richen up the idle. It is kinda weird. I had my safc at like +30 to get a good idle at the low rpm and throttle settings. Then at 2000 rpm on LTH it went to like -30. Seemed stupid to me. But after I got done pl;aying around I tuned the idle with my maft and am using the SAFC for everything else.

IMO I would still go with at least 650's. The reason I say this is you are going to want more once you get to 350 hp. The boost monster will grab you and here comes the 50 trim or something like that. I see dsmlink or keydriver in your future.

Also the 255 will have no problem keeping up with a idle fp or 50. The 2gnt guys run crazy fuel pressue when using a 12:1 fmu. I had mine pegging out my 100 psi fp gauge. The walbro is a beast.

 

[force it in]

I tried tuning PTE 680's with my MAFT & SAFC2. My car knocked like crazy running 91 octane California pump gas & 50/50 meth injection on an MHI Evo3. Just too much timing. I had to put my RC 550's back in with a N/T FPR (higher base fuel pressure) so that I could run 16 psi. Then I bought an EPROM ECU and ordered a Keydiver chip. Now I can run 24psi on 91 octane with meth injection on the 680's and stock turbo FPR. It feels like a completly different car in a good way. I've read that others have had sucess with 550's and an Evo3, but my injector duty cycle was over 100%.

 

[Echo5Zulu]

Thanks for the good replies everyone. I know I should probably eprom and keydriver chip it but I think Im going to just stick with 550's, safc, evo3 16g, walbro 255, and tune it at 50psi fuel pressure and see where she takes me. According to the calculators 50psi will get me 350hp at 93% inj duty cycle. Should be fine since Im not going to run them that hard all the time. Im not one to race everywhere I go. I like to tune/mod my car a little at a time. Its more fun to me to slowly gain power and see what makes a difference rather than buy a huge setup and toss a ton of parts at it and try to get it all tuned together all at once. Probably more pricey in the long run but fun non the less. It is a fwd so any more than 300-350 and its useless.

Now do you guys prefer the pintal or ball style injectors? I heard the balls can be run harder but can clog easier and the pintals are time tested and more common.

Thanks.

 

[SinaiTSi]

I know you already made your decision but for what it's worth, I have a 2g maf, 3000gt VR4 fuel pump and denso 660s that I'm trying to tune with my SAFC. It's a little difficult because I'm knocking higher rpms wot because of too much timing, which is why I'm getting a chip soon so the car has a good tune on it and if I might need to fine tune anything, the SAFC is always there.

 

[turbodsm18]

Thanks for the good replies everyone. I know I should probably eprom and keydriver chip it but I think Im going to just stick with 550's, safc, evo3 16g, walbro 255, and tune it at 50psi fuel pressure and see where she takes me. According to the calculators 50psi will get me 350hp at 93% inj duty cycle. Should be fine since Im not going to run them that hard all the time. Im not one to race everywhere I go. I like to tune/mod my car a little at a time. Its more fun to me to slowly gain power and see what makes a difference rather than buy a huge setup and toss a ton of parts at it and try to get it all tuned together all at once. Probably more pricey in the long run but fun non the less. It is a fwd so any more than 300-350 and its useless.

Now do you guys prefer the pintal or ball style injectors? I heard the balls can be run harder but can clog easier and the pintals are time tested and more common.

Thanks.

If you havent already ordered everything, you may want to try and find some EVO injectors. They are 560 cc injectors but I beleive they flow closer to 590 cc. It would get you more out of your setup but would probably still be easy to tune with the SAFC. Also it would lower your IDC's quite a bit and you wouldnt have to run such a high base fuel pressure.

-Kevin-

 

[Street Surgeon]

Can't go wrong with the 650's man.

 

[Geezus_Aach]

i am running RC550s with my EVO3 16g, however, i am using dsmlink. no probs with knock, car runs fine. i had the SAFC2 before, but didnt have a datalogger, plus i like the features of dsmlink and that allowed me datalog

btw, i agree with the other poster about using evo8 560cc injectors. you may be able to get those cheap, plus they are mitsu branded.