Need input from people that can do smart stuff like math

Tell me if this sounds right.

Intake valve diameter is 1.84"

Assuming intake flows 170cfm (I know I'm being optimistic)

Optimally I need a intake runner inside diameter of 1.65 with top at plenum being 1.75in in diamater

Plenum should be about 4 in diamater and about 18in to 20in long with rear angled down giving a internal volume of about 225 to 250 cubic inches.

I have a Ford 65mm throttle body and I will be running 65lb/hr injectors (Larger than needed to account for E85 fuel).

Anyone see anything that needs changed? Comments appreciated.

Thanks!

Mark

I suck at math also but dont go too big on the injectors. Those seem (did no do the math) pretty big assuming you are going with 6 of them, thats 390 lbs. Big injectors have lots of trouble at idle. Are you trying to run Flex or just E-85? Im running a 500 cuin gas motor on 170lbs. I know I must be close to the upper limit so there is no way I could do e-85.

Read some where plenum volume needs to be 0.5 engine volume and each runner 1 - 1.25 x 1 cylinder volume.

From what I've read the BSFC numbers for E-85 are 30-35% higher than for gasoline.

So if you start with a BSFC of 0.50 lbs/hp-hr for a normally aspirated engine on gasoline, you would consume .65-.675 lbs/hp-hr for the same engine on E-85

By the same logic, a boosted gasoline engine consumes 0.55 lbs/hp-hr so an E-85 fed one would consume .715-0743 lbs/hp-hr.

The specific gravities of the two fuels are different and while we rate injectors in lbs/hr, they actually meter a volume. The "lbs/hr" assumes a specific gravity of .75 which is average for gasoline. E-85 is slightly denser at .78 SG so the injectors can be 4% smaller than otherwise indicated. It's probably best to keep this 4% as a safety margin against leaning out and ignore it in the calcs.

You're planning on 6 x 65 lbs/hr injectors or 390 lbs/hr.

(390 lbs/hr) / (.743 lbs/hp-hr) = 525 HP

(390 lbs/hr) / (.715 lbs/hp-hr) = 545 HP

That's a whole lot of ponies out of a Falcon 6

Sound like 45lb injectors would be a better setup if my goal is a optimistic 360hp. Seeing what some people are getting I wouldn't be surprised if I only got a little over 200hp but even that would be a night and day improvement over my 2.3L n/a 67rwhp in a 3100lb car.

Still undecided on the runners and plenum.

I want to optimize the engine for best performance with E85 but since I will have a Megasquirt II ECU I plan to set it up with two tunes and a flex fuel sensor.

One of the many tricks of getting flex thing to work is finding exactally the right injectors. All the calculations I did when I was thinking about it did not give me any room for error or a safety margin. One guy I talked to had some fancy regulator setup to alter the pressure when running one of the fuels. Not sure of the details because it was more complexity than I wanted to deal with.