91 octane to E85 fuel question with return line

[Salty SRT]

I had a thought regarding switching from 91 pump gas over to e-85. Currently I have DW stage 2 injectors with a DSP rescale tune accounting for the larger injectors. I have heard of people, when they get larger injectors say 750's, they use a return line setup and then dial back the base fuel pressure to account for the extra fuel from larger injectors without having to rescale (WOT then being tuned with whatever you have, map clamp, DSP, Neo, etc). My line of thinking, would be couldn't I install a return line, then up the base pressure to account for the ~30% or so increase of fuel that E-85 needs (then tune my WOT with the DSP handheld to account for the increase in base pressure and now rising rate).

My only worries would be if I can/should run that high of base pressure and with the rising rate, I don't know if the injectors are rated to that high of pressure (need to check with DW). Later on I will be getting a new tune for 1000cc injectors and a 3bar sensor, I just don't want to pay for an "in between" tune.

[Salty SRT]

71 views and no replies

[apexcrazy]

Well since nobody else has posted , here is what I know about the subject .

You need to figure out what the actual specs are on your DW injectors . For example , My RC 650s Are rated at 650cc . Duh . RC tests its injectors at 43.5 psi , but the fuel rail of a stock srt4 is running at 58 psi . add to that the fact that RC uses a lighter test fluid than what most injectors are tested with (N-heptane) and you realize there is a major difference between the stated flow and the actual flow when installed in our system . After all consideration are accouted for , my RC650s flow at 712cc in my fuel rail .
The stock S2 injectors flow 682cc , stock 04-05 stage0/stage1 flow at 577cc , for reference .
Now , as I understand it , your rising rate return line doesnt actually increase fuel pressure when it sees a boost signal , it does the opposite . It actually reduces fuel pressure untill it sees a boost reference signal , then it allows up to the full amount of pressure to pass thru . If you set your regulator to 58psi , then you are limited to that total pressure . How high can you run your fuel system beyond what it was designed for ? 80 psi would get you your 30% increase . is that possible ? I dont know .
Im sorry if you know all this stuff , I just thought I would reply .
All that said , I have run up to 50% e-85 in my SCT tuned 650s (again , actually 712cc in this application) in an otherwise stock setup . I suppose I could get them to flow enough for a full e-85 tune , but I doubt I could up the boost much beyond stock without pushing the envelope , or running out of headroom . So I kinda doubt you could run a hot e-85 tune safley on 682cc injectors . Just my opinion .
Another option that may make this plausable is a modified stock regulator that flows more than 58 psi . I know they are out there , but I dont know who makes them . But again , some believe that increasing PSI in the fuel system will overwork the stock fuel pump , but I am not certain of this .
If Im wrong about anything I posted , maybe somebody that knows what they are talking about will post up , correct me & teach us both something

[reed32]

for e-85 you need:

returnline w/bnf
750's
fp@50psi on a 1 to 1
255 pump
fuel pump rewire

good for 20-25psi on e-85 stock turbo

[apexcrazy]

Ahhh , the voice of authority .
Thanks Reed . I am very happy with these injectors , BTW . Do you have any idea what the dead-time is on these RC 650s? I cant seem to find that info .