Unmetered Air leak = Better MPG???

[Tygen1]

Well, the initial results are good. Today I got 45mpg on the way home, the best during the previous week of base line was 43. Not really a valid test, but the the gph readings are much better. While messing around, I let the car idle with the line hooked up, checked the gph and it was 0.21, unpluged the hose and it dropped to 0.18, plugged it back in and it went right back to 0.21, all while keeping the car running. I've also observed that the the gph readings at the speeds I travel are better also, resulting in roughly 5-10mpg difference.


So why isn't the PCM adjusting? Shouldn't it be attempting to compensate for this large vacuum leak? Is it possible the engine is running a bit lean and the PCM just doesn't care??? Once I get a full week under my belt, we'll see if the improvement stays, it usually takes about 3 days of commuting to let the PCM adjust, tommarow will be the thrid day....

[moorecomp]

I disconnected mine the other day and today with even the cool weather got 42 on the way to work versus less than 40 for my last tank with it hooked up. I have noticed that the engine is much more responsive with the line disconnected, I think the pcm is adjusting the ignition timing and that is where we are seeing improvements. With the line disconnected, I can cruise through town in 5th gear at 30 mph, 1300 rpms. Before, it would never allow this as it would almost buck and stutter. Pulls a lot better going uphill without downshifting too. Must be the timing. Do you have a scanguage that would give this info?

[Christ]

I think that the PCM might not be adjusting because it's metering the airflow through the MAF, it probably just thinks the O2 is stupid, or it's not far enough out of spec for the PCM to compensate, or it's so far out of spec that the PCM is at max trim.

More likely, in this case, the O2 is the "odd man out", and the PCM is a bully, calling it retarded and kicking dirt at it's readings. :P

[Tygen1]

I can't believe all those folks who said Escorts were retarded were completely right? Sweet, my car is so dumb it can be run lean without it even knowing
I do have aa scangauge, but never checked the ignition timing. I did check the O2 output, but it is so ragged it's hard to tell, although it appears to be the same. I'll check timing tomarrow morning, but I won't be able to check it without till Saturday....maybe?
This is good stuff, I'm glad you have seen an improvement Moorecomp!

[Christ]

Can you check O2SAT? Or if not, can you get a signal reading from the O2 sensor before/after while you're running, and one test signal after fresh start with it unplugged, one fresh start with it plugged in. 4 total numbers.

Also - if you have a way to see your vacuum readings, do me a favor, engine brake at about 4k rpm, no throttle, and tell me what your vacuum readings are. That's a side project, though.

[Tygen1]

You'll have to define O2SAT.... I can see the O2 sensor as a AFR or voltage reading.

I'm not sure the PCM will let the TCC lock at 4K, but I got a way around that BTW, no MAP sensor on this car, but I got a old vacuum gauge I used to use to set the power valves on Holleys

I won't be able to do this, this weekend, but I'll get around to it.

[Christ]

Originally Posted by Tygen1

You'll have to define O2SAT.... I can see the O2 sensor as a AFR or voltage reading.

I'm not sure the PCM will let the TCC lock at 4K, but I got a way around that BTW, no MAP sensor on this car, but I got a old vacuum gauge I used to use to set the power valves on Holleys

I won't be able to do this, this weekend, but I'll get around to it.

Oxy Saturation Level... O2SAT. It's how some readers display the O2 information, as a percent of the sensor's range. Instead, I'd want to see the voltage reading.

Yeah, all I need to see is the vacuum reading while engine braking. Even if the TCC isn't locked, it shouldn't freewheel at a speed that high, unless you're in 1st gear. I usually drop it into 2nd gear at about 50MPH to test engine braking in automagics.

[Tygen1]

It is magic

[Christ]

Originally Posted by Tygen1

It is magic

I type that on purpose. :P

I hate the term "Automatic", because it blurs people into thinking that it "just happens" with no input, no consequence, etc.

Thus, they think that because it's "Automatic", they think it's "Magic", hence "AutoMagic".

Even though it's only one key down and slightly to the right, it's not a typo. Thanks for noticing!

[Sulfuric]

I'm very interested this, please keep posting your findings. If I can make my car run leaner without hurting anything, I think we can agree it will be very beneficial.