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MetroMPG 08-31-2008 12:16 PM

MPGuino installation/setup: 1998 Geo Metro (Pontiac Firefly)
dcb recently sent me a "care package" with a couple of components my small town rat shack didn't have. To my surprise there was also an "evaluation" MPGuino in the box!

I hooked up to the car (1998 Pontiac Firefly 1.0L TBI 5-speed) this weekend.

Random observations:

1) COOL!!!

2) finding the injector & VSS wires was easy, mostly because dcb has the same car as mine and has blazed that path already (with pictures!):

3) with those settings, the MPGuino was showing half the MPH that the speedometer/ScanGauge showed, so I halved the VSS Pulses/Mile value in the MPGuino setup (to 8204), and that seemed to fix it.

4) I still need to factor in an additional offset for VSS Pulses/Mile, because the transaxle I swapped into my car (with a taller final drive ratio) was originally calibrated with a smaller tire size (diameter) than my tires.

5) The car's MPH display is jumpy, as dcb already noted with his Metro, though he also found that despite this, the total distance traveled seems accurate.

I was thinking I could calibrate my car's VSS pulses/mile setting by jacking up the drive wheels and idling the car in 5th gear to rack up some mileage without having to drive around unnecessarily. It seems to idle @ about 30 mph.

Any technical reason I shouldn't do this? (Aside from the fact it'll pad my tank MPG with some awesome numbers - seems to get about 150 mpg idling in 5th on jack stands. :p)

I probably won't have a chance to calibrate the MicroSec/Gallon until I get back from the tall ship race though, because I'll have to do some actual driving to tweak it.

Will 08-31-2008 12:23 PM


Originally Posted by MetroMPG (Post 57689)
Any technical reason I shouldn't do this?

I think it would be ok, and really neat to see. Just be real careful!!!!

IMO I would ask Johnny what he thinks...

bbjsw10 08-31-2008 09:31 PM

You are running the Xfi transmission correct? So the vss pulses should be the same for mine right? Ordered my stuff today to make my MpGuino Iduino, can't wait real feedback finally.

And can you enter these numbers right through the MpGuino setup screen?

Johnny Mullet 08-31-2008 09:49 PM

Nothing wrong with having the car securely raised and supported while you run it in gear at idle. This will make the axles have slightly more flex than usual, but it should be fine for a short period of time.

MetroMPG 08-31-2008 11:32 PM

bbjsw10: I'm running the Swift 1.3 SOHC transmission, not the XFi.

Mullet: thanks for that. I will admit I suspected as much and went out and ran the "jack stands calibration run" before I read your reply. Stuck a snow scraper lightly against the gas pedal and accumulated 20 miles per the ScanGauge. That'll give me enough info to get the Guino dialed in (when I get back from my trip).

dcb 09-01-2008 12:52 AM

Cool, let me make a guess at your modified vss pulses per mile (stock *should* be 8208). Assuming your tire circumference is 5% greater than stock for that tranny, I will guess you have an effective vss pulses per mile of 7798.

Also will stash the metro install pics here till we get car specific wiki pages with setup data AND pics:

metroschultz 09-01-2008 08:10 AM

Just a note
The injector drive wire comes from the ecm as well.
You wouldn't need to run any wires to the engine if you tap all of them onto the ecm.

dcb 09-01-2008 09:13 AM

I've had mixed results tapping into the ECM for the fuel injector, would like to see someone actually make it work before calling that a certainty.

starquestPilot 09-02-2008 07:48 AM


Originally Posted by dcb (Post 57843)
I've had mixed results tapping into the ECM for the fuel injector, would like to see someone actually make it work before calling that a certainty.

Worked for me - got Injector and VSS from the ECU...

MetroMPG 09-15-2008 07:01 PM

How I collected my speed/distance calibration info for the Guino...

YouTube - Calibrating an MPGuino fuel consumption computer

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