1. As mentioned before, OBDII can only _calculate_ fuel flow rate, which leaves you with inaccurate information at times. For example, during DFCO (Deceleration Fuel Cut Off).

2. OBDII is embraced by modern performance-minded individuals and most OBDII vehicles can be tuned a lot easier than non-OBDII, though at times more expensively. The total result can be better.

3. Fuel injector duty cycle is the most accurate way to measure fuel flow rate. If you’re looking to publish specifications, you’ll need to know your manifold pressure; but if you’re just looking to get relative numbers to understand your engine, this is a great way to measure.

4. This will work fine on OBDII cars, and gives you data you can’t get, so it’s NOT LIMITED TO PRE-1996 CARS!

5. Early 90s cars, when decently maintained, are some of the most efficient cars on the road. They were a lot lighter than newer cars (now we have huge amounts of additional safety weight, generally bigger vehicles, and more gadgets weighing us down), often had smaller engines, ALWAYS had far less power, and were tuned for efficiency.

6. I can’t load mpguino’s page right now, but it sounds like a FI duty cycle measurement combined with VSS (Vehicle Speed Sensor) measurement to give you MPG. That’s great and if it’s made from cheap parts I might make one. However…

7. For $33, you can get a digital multimeter with dwell reading from Harbor Freight. Tap the injector wire -> positive lead on DMM, ground the negative lead, set to 4 cylinder dwell regardless of how many cylinders your engine is. Total investment: $33 and ten minutes work (plus the time to got to Harbor Freight or the money for them to ship it mail order). The scale is 0 to 90 instead of 0 to 100 so you’ll need to mentally adjust it a bit.

I’ve been using the $33 DMM that way for a week or two now. I’ve been hypermiling for a couple months and have now improved my 2008 VW by 2mpg just from FI duty cycle monitoring alone. I learned that it uses more fuel at 90% open throttle than at 100% WOT, and that DFCO is very aggressive above 40mph but won’t start under 35. I also learned that my ECU doesn’t go to open loop no matter how I drive, it only uses it for 30 seconds after the car starts and (of course) when in DFCO. (Thanks to monroe74 on gassavers.org for telling me about this hack.)

the mpguino does fill a niche market, but then again so does the scanguage for obdii cars. That being said, mpguino is opensource and is going to be cheaper than the comparable supermid. (the dollars fall against the yen, and rumor is the guy making the supermid is just too busy to do them anymore.

That small market more like than not is also not as small as you think. A lot of people are either ditching their new rides or at least acquiring an older vehicle simply because we’ve got suvs and trucks that just aren’t worth it anymore (myself included) a couple of thousand or less for 30+ mpg is well worth it when you do the math.

I have full control over engine management through the ODBII port.

oh and my 1995 240sx gets 28MPG… there’s something to be said for proper tuning and maintenance.

As someone who’s about to buy an 80′s Jeep CJ-7 to play with (custom gauges/electronics), I’m a part of that small audience, and I certainly appreciate this article. Old vehicles are fun to play with, and you don’t have the guilt associated with damaging a brand new car when you screw up ;)

This project is pretty cool.