Gas milage from another forum

[tracka96]

I copied this post from another forum, for what it's worth: Tracka96

1996 Geo Tracker 1.6l Gas mileage enhancements! 35-40MPG...Read !

To those interested....

I have been working on some mileage enhancements on my 96 tracker....

I's a 4 door 4wd with a 3 speed automatic.....

When I first got the vehicle...I was seeing like barely 22-23mpg....

Which didn't really tell me much...I bought it with 110,000 miles on it...
Original spark plugs...cap rotor wires....etc....

Anyhow....The first step in Mileage enhancing was to dump the old 180 degree thermostat...up to a 195....A K&N drop in air Filter NKG v Plugs...
Got her up to 27 mpg on the hyw....

adding 2 oz of acetone...1 oz of xylene to the gas ...I gained another 2 miles to the gallon on the highway....

Now here's the big gain!

I've installed a thermocouple in the Exhaust ...just past the manifold to monitor EGT...Exhaust gas temps....

Using just a simple 1.2k ohm resistor to ground and a 10k ohm potentiometer
voltage divider...I tapped the MAF sensor feedback to the ECU...
With the potentiometer, I'm able to lean the fuel mixture way back.....

I am using a device called ScanGuage...Plugs into your OBD2 port,
Gives a current readout your selection of like a dozen different digital guages.
ScanGaugeII - Trip Computers + Digital Gauges + Scan Tool

The big thing to watch for when leaning back the air fuel mixture is to make sure the ECU is compensating by adjusting the timing advance!

When I lean the fuel...I see immediate change in ignition timing....
One of the things this does is prevent Detonation...Pinging ...especially under a load!

The mileage on a 10 mile trip...combination highway/city here in Pittsburgh...
was 40 mpg on the return trip....it was 36+ on the trip there!
(the acetone has been out of the system for the last tankfull or so)
Also I wanted to measure temps without any additives....
The thing to watch for with the pyrometer....
Take the vehicle out on the open road and run it at 65 mph...
under a normal load....Now when you lean the mixture...Make sure your not exceeding like 200 degrees past the High end point!

I do have a few more devices to add to the Tracker...
And will have more to post ...hopefully this week!
Brian Gerber

P.S. Use this information at your own Risk!
This is a vehicle I can afford to rebuild if there becomes an issue!

So far it looks fairly safe!

C.E.T. N.A.R.T.E. (Certified Electronics Technician, National Association of Radio and Telecommunications Engineers)
FCC licensed Electronics Technician W/Radar Endorsement, GROL license # PG00022728
FCC Advanced Class Amateur radio license K3RCA
Certified Power Engineer NIULPE (National Institute for the Uniform Licensing of Power Engineers inc.)
CompTIA A+ and Net+ (Computing Technology Industry Association)

[jtgh]

great work,
lean burn is what HE is doing. ( like in a Prius)
The hard part is keeping the oxygen sensors "closed loop" servo from correcting any lies you feed from the MAF. (rescaling pot. etc.)
the additives are expensive, and get more each day. ( I want to burn gas, not Paint thinner)

the scanguage2 and EGT are very helpful so you dont fool your self.

the only other issues ,is what will the CAT do.?

all that I have read (eom cat designers) says it will melt off the precious metals.
how you deal with that , depends on where you live and the moral issues.

i believe the 40mpg, as mine can do that , if I go 45mph and never move gas pedal fast.
but hills , kill it.

His peak must be 50mpg and ave. 40mpg.

With custom ECU you can have 16.5:1 AFR while crusing, ( with a wide band sensor ) operating in closed loop. Easy to do really.

the stock ECU will do everything it can to force the car to 14.7:1 AFR.
He must have unplugged the OXY sen. This will put .45v on the port to the ECU.
this will tell the ECU ( I AM PERFECT forever) when in fact you are lean.

I note that he was watching the timing, because if that messes up , detonation will happen. (sharp cookie he is)

The whole thing here, is fooling the ECU from dropping to Limphome mode.or going into detonation ( no knock sensors on this puppy).

I do not recommmend doing this unless you get a custom ECU,so one can have full control and no surprises. ( or you have spare engine blocks)

very good post. Thanks very much for sharing it.

cheer.s

[jtgh]

his posting of his HAM handle was kinda goofy , now the black helicopters will hover over him for ever. or ? worse.......