i'm running dsmlink with a 2.3L stage 5 head with 272 cams and 1000cc injectors 255 fuel pump and e85 at fuel, at only 15psi i'm still getting knock around 5500-6500 i'm already running a colder spark plug, its gapped at 29, and my a/f ratio is around 10.2-10.6, does anyone have any tips and ideas on how to eliminate my knock its only 1 - 4 degrees of knock but i shouldn't be getting any at all, please help


- junkyardtalon

What is your timing advance at that point? Starting at 500 - 1000 rpm prior to the knock take out timing in one degree increments.

my base timing is 5 degrees and in dsmlink we have it around 16-18 degrees but whenever i knock it drops it down, we've pulled timing out a few degrees in the higher end and it still knocks, i have about 4 dregrees pulled out between 4500-6500

If you're actually running E85, you're too lean. Soich for E85 is 9.7:1 where max power is around 8.8:1.

ya.... get some 93 in there!

The octane rating for E-85 is actually 105 so it is not a lack of octane that is causing the knock. Based on what I have read (if I interpreted the info correctly) it is the fact that E-85 is an extremely oxygen rich fuel. I would suggest making your A/F ratio a little richer or blending the E-85 with about 30-40% straight unleaded or E-10.


Did you do the conversion to run the E-85 or did you just start putting it in?

yeah i did the conversion, ok i've been told several different things about what stoich is for e-85, someone else i know told me the stoich is 10.5 and others say that since i don't a fuel anylyzer then 14.7 is stoich since the wideband i'm using won't compensate for e85, who's right?

ok well forget the last question, i did some research of my own and stoich is 9.7 and max power rich is 6.9. that answers some of my questions for knock, cuase that would mean i'm running super lean.

wortdog knows his stuff...

i'm guessing there for either cuase the website i got the info doesn't discriminate between n/a and forced induction, now that thats all out of the way, wortdog - is my fuel pump not big enough? its a 255 lph, i found an equation to calculate the fueling i would need but i'm not sure if its right....

Turbocharged engines typically need BSFC fueling of about 0.60 lb/hp/hr, a reasonable first guess for fueling required on E85 would be 0.77 lb/hp/hr

(BHPgasoline x 1.05) x BSFCe85 = Estimated E85 fuel requirements

(350hpgasoline x 1.05) x .77 = 282.975

so would i need a fuel pump that pushes 282+ lph?

You need a lot of pump and injector to run E85, a lot of folks running E85 are running 1600cc injectors at a minimum. Anybody running straight methanol is usually at 8 1600cc injectors, but that's a different ballgame.

The 255 is a lot smaller than 255 once you start talking about big boost, but if its rewired and on a 1G its still in the 240 l/hr range at 15psi.

I know Walbro doesn't recommend running the 255 with E85, but I haven't heard of any problems with it. The 1000's you have should be enough for 350hp at the crank you're talking about. You will have to at least buy another 255 pump and run the two of them or buy a nice Aeromotive external pump. I'd also upgrade the fuel line feeding the fuel rail.

Is there a particular reason you're running E85? 350hp at the crank should be pretty easy to obtain on straight 93 pump with the headwork and cams you have.

the 350 hp was just an estimate on pump gas, with e85 and if i was able to turn the boost up to 20psi i would be around 450-500 at the wheels, this is all just guess work cause i'm in the 11's with 15psi, if i fix my tranny shifting problems then i'm pretty i can get into the 10's with my set up with a little more boost, my lastest time slip is 11.9 @ 116mph 1.65 60', so you can obviously tell there is alot of time loss in the middle cause all my shifts are slow, with those numbers i should be seeing 11.4 11.5 1/4mile times.

i have another 255 with a custom setup that i'll try and i'll also get bigger fuel lines

one other cuase of my knock - could it be that i have to high of compression? its a 2.3L short block with eagle rods and wisco pistons, and with the stage 5 head, 1mm oversized valves, 272 cams,

i just did a compression test and 1-3 cylinders have 155-165 and cylinder 4 had 195, the machine shop didn't do a very good job, oh well i think i'm just going to run c16 as fuel and forget about trying to run e85 i already have to many problems and c16 should eliminate all of my knock, hopefully

thankx for all of your info

The Wiseco 2.3 stroker pistons are only 8.8:1, you should be ok there. You'll definately want the 1600's to run 500whp on E85 though.

Running 10.5:1 on E85 is like running 15:1 on pump, its probably going to knock at full throttle.

And, yeah, theoretically running about 6.7:1 gives you the most power, but I doubt the stock ignition system will fire that kind of mixture off reliably. You'd also need a firehose of a fuel system to feed that much fuel.

As far as timing goes, if it's still knocking when you richen it up a bit, don't be afraid to trade some degrees of timing for lbs of boost, you'll make more power up to a point.