Instant MPG Calculation Tool

[Mrmaroon]

I Was reading a thread over at gearhead-efi.com on MPG calculation. Someone posted formulas to calculate it using INJ PW, RPM, and MPH. If you have a scan log and want to test it feel free. I put the link in my sig. I may update it to allow averaging big chunks of data.

You need a google account to use it I believe. Copy all cells from link and paste into your own Google Sheets document insert data

I make no guarantee on the formulas, this is a work in progress.

https://docs.google.com/spreadsheets/d/14-url_egi3IJR9fOhIgyWm0GQLJnXKNOm1_u4VPHu-s/edit?usp=sharing

[shownomercy]

Wouldn't it need to know fuel pressure?

[Mrmaroon]

I think his formula uses a stock injector size. I didn't think about fuel pressure :\ On stock injectors does the FPR "hypothetically" adjust to maintain a constant flow rate?

[shownomercy]

Yea, in theory I guess, but PW means nothing without knowing the pressure, so I guess you can assume the stock FP?

[fullforce]

What would be the benefit of this?
If you know calculate your fuel mileage at every fill up you should know what your average is.
I must be missing something?

[shownomercy]

What would be the benefit of this?
If you know calculate your fuel mileage at every fill up you should know what your average is.
I must be missing something?

Could help you find a sweet spot for highway cruising, but I have found that all the instant MPG stuff is way off. Especially if you have modified tables in tune.

[Injuneer]

Appears that they are assuming the injector is flowing it's rated capacity, hence being operated at the differential flow pressure used to rate the injector flow. Appears they assumed 24.192 #/HR. My stock programming was 24.896

As far as variations introduced by vacuum compensation, the purpose of the vacuum compensation is to maintain the differential pressure across the injector (rail pressure minus manifold pressure), insuring that it's flow rating pressure is maintained.

If you have altered the baseline pressure to something other than the stock flow rating, or are running a different injector, you would have to calculate your new flow rate and enter it in the equation in cell A6. Might be a good idea for them to include that as an input.

[Mrmaroon]

What would be the benefit of this?
If you know calculate your fuel mileage at every fill up you should know what your average is.
I must be missing something?
My idea was to see if cruising in 5th vs 6th gave better mileage at different speeds. I think there is a way to tell by vacuum too.

[fullforce]

Could you just go buy engine load??

[MoeHorsePower]

Gas Mileage? Horsepower and Gas Mileage dont go together. (it can)when my street car made 648 rwhp some would say, what kind of mileage do you get? I would tell them, I built my motor for horsepower not mileage. at least for me, I really dont care what kind of mileage I get, of course if you are getting like 5-6 mpg then trouble shoot for the cause..

[popo8]

Ill play... with my 6spd and 9" with 3.90 gears in it... my boosted 602whp camaro pulled an average of 20mpg to kentucky.

LTXtech.com IS my drug...
OWNER/ADMIN

[MoeHorsePower]

Same here, when I was supercharged with 648 RWHP, and an M6 i got like 21 or so mpg..