Heres a dillema .. How would one run say.. 107, 110 octane on a FI application??

I think I'm detonating too much. I'm not running lean, but I think i'm running too hot.

-- Joe

 

Either get some Race gas or you can mix up your own using Toluene and a touch of ATF.

THat is what we are running in our 406 due to the compression we have. I can run 94 octane but anything over ~40% throttle give a nice pinging sound.

At 30% throttle though I can burn the tires all thru 2nd

Do a search on "octane home brews" on yahoo you will find the site

 

You sig shows a Vortec.
and 24 PPH injectors.

If your using a FMU for additional fuel, lots of folks have had problems using them.

 

Hey Grumpy,

FMU + BTM = problems, yes!.. I went from 165 to 730, running $8D. When I get the hang of tuning the 730 a bit better, I'll be making the swap over to $749, _or_ if I'm brave I might just start altering the tables in $8D to goto 190kpa.. part of me says "stick with 730 and make it boost friendly" another part says that will cause more trouble than its worth.

Anyway, the point of the post was.. I'm figuring under full boost I'm at like.. 11.5:1.. I wanna add a 50 shot of NOS on top of that.. But I have octane limitations of "unleaded".. How do some of you guys run 10s, 9s with FI?? I don't get it ..


-- Joe

 

If your running 24s and boost, you're out of fuel.
At a 85% DC your out of injector at 320 HP. Raise the F/P and you immeditely reduce the amount of fuel available at fuel demand. So while you may raise the F/P to 60 PSI you still maybe actually out of fuel.

It's far better to have a large injector and low DC then trying to hammer the injectors into doing more then they are designed to.
On my lil v6, I run what works out to be 61 PPH injectors to get it to have a fuel curve I can fully taylor to do exactly what I want.

And I run fairly well with just 16d of timing.

 

I like that suggestion. I curently have "other junk" to deal with, but making a 7730 properly handle a 2 bar (or possibly even a 3 bar) MAP sensor is on my "project list".

Also, as Bruce said your fuel injectors are far too small. My buddy with a N/A 383 Miniram/AFR 195s/ is hitting around 90+% DC at 6,000+ rpm with only 30#s. I've suggested he should be running 36#s based on the potential HP of his engine.

I suggest you do an Injector Sizing calculation based on you estimate your HP to be and get the appropriate injectors.

 

**blinks**

Okie. My FMU raises pressure to about 55PSI which pretty much max's out my pumps I think. With the 24lbs injectors, I get about .600mv at WOT under full boost, so I figured that the 24PPH were fine.

You think I should switch to some 30's?

-- Joe

 

I found a calculator on the internet. Looks like at 500HP which is what I'm hitting/aiming for based on e/t's (without the nitrous) and a 80% DC 36PPH are recommended. Thats at 50PSI

That would work great because my N20 jets (which i'm too scared to use at this point) are jetted for a 50, or 75 shot @ 50PSI fuel.

Now here is the question that actually has something to do with this board. I idle right now at 128blms for most of open loop, I go into close loop, stay at 128, then right at about 210degrees, I'm at 108. Pretty much stay at 108. O2 goes up and down like michael jackson. If I switch over to a 36pph say this weekend, will I be able to get a short enough injector pulse @ say 45psi
that it won't run rich at idle (which is 700-800RPM, trying to find the sweet spot). I'd like to rip the FMU out all together soon.

Glenn I'm strongly considering the 2bar $8D stuff. Have you done any preliminary work on it? I'd like to rip the FMU out all together soon so my FP can be static at around 50PSI at WOT.

-- Joe