[Diy_efi] New project

[steve ravet]

Dennis Noordsij wrote:
> One thing you mentioned, a VE table for SD. If you take the MAP, compare it to
> the ambient pressure, isn't there a nifty formula that takes the size of the
> throttle opening and angle of the butterfly to calculate exactly how much air
> would have moved in due to pressure differences? Which would give you the
> exact amount of air almost as accurately as a MAF could? Every time you
> receive a TACH pulse, take the time that has elapsed since the last pulse, do
> the math, inject the fuel. I.e., where does the VE come into play?

VE comes into play when you calculate the mass of air flowing into the
engine:

PV=nRT, P=MAP, T=temp, R=constant, V is a function of VE and rpm, solve
for n.

I doubt there's a formula for flow versus throttle angle, the vague
memories I have of that kind of ME stuff tell me that there aren't
formulas for anything in ME, it's all in tables at the back of the
book.  And if you have to have a flow table for your throttle body,
might as well just have one for your engine+throttle body instead. 
Maybe someone else can weigh in here.

> Like I said before, it's for-fun, to actually build an EFI setup ourselves.
> The point is not to end up with EFI, which could be done much more
> painlessly, but to build it from scratch.

Well that's a great goal.  Your boat's reduced set of operating
conditions should allow you to build a much simpler system than what a
car manufacturer would use.  I'll be paying attention, I still want to
do this on my boat also.

good luck,
--steve

-- 
Steve Ravet
steve.ravet at arm.com
ARM,Inc.
www.arm.com

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi