39MPG, got it today!! Options

[toon1]

I've been working with Megasquirt with timing and Fueling. The car has been responding well to the changes.

I had to take a trip to the foothills today and decided to take the 914 and really test the changes. Most of the driving I had been doing had been around town so I wasn't sure how the car would respond to a long freeway trip.

while cruising up hwy 5 the cht's were 340.....I pulled up Tuner studios and leaned out the area around cruise a bit. Suprisingly the CHT's dropped about 5 * and were stable.

I kept the setting there and was wondering how this would be when I started climbing hills, again I was suprised how good the head temps were. nothing over 370(which was for a very short time) on the long climbs.

I don't have my 02 sensor connected yet so I can't say what the AFR is.

At the end of the trip, I drove 176miles and it took 4.5 gallons to refill....39.1mpg......NICE!!!

[rick 918-S]

Nice!

[wndsrfr]

YIKES!! Really risky to change timing or fueling without AFR's....detonation lurks there....especially when leaning it out!!!

[toon1]

YIKES!! Really risky to change timing or fueling without AFR's....detonation lurks there....especially when leaning it out!!!

No risk at all (IMG:style_emoticons/default/smile.gif) , I have a Dakota digital CHT gauge. If any ill affect of leaning the AFR were to happen I'd know instantly.

The timing at 26-2700rpm (cruise speed) was 25-26*BTDC,( I think I can go more) well within stock timing range. With MS you can alter how fast the timing comes in, which, I'm finding makes a big difference. You can also alter areas of cruise, which makes a big difference. The only detonation(pinging) that I noticed was at the upper rpm's while having my foot in the gas. Again more tuning needed in that area.

Surprisingly, as I leaned out the cruise areas the cht's got COOLER.

Seems counter intuitive, I have an idea why this is but can't say for sure.

It would be a great question for Jake.

[barefoot]

I've been working with Megasquirt with timing and Fueling. The car has been responding well to the changes.

I had to take a trip to the foothills today and decided to take the 914 and really test the changes. Most of the driving I had been doing had been around town so I wasn't sure how the car would respond to a long freeway trip.

while cruising up hwy 5 the cht's were 340.....I pulled up Tuner studios and leaned out the area around cruise a bit. Suprisingly the CHT's dropped about 5 * and were stable.

I kept the setting there and was wondering how this would be when I started climbing hills, again I was suprised how good the head temps were. nothing over 370(which was for a very short time) on the long climbs.

I don't have my 02 sensor connected yet so I can't say what the AFR is.

At the end of the trip, I drove 176miles and it took 4.5 gallons to refill....39.1mpg......NICE!!!

From my combustion chemistry, max combustion tempeerature occurs at stoiciometric A/F, that is wheere exactly the correct amount of oxyger surrounds the fuel molecules , no more/ no less. Either richer or leaner from that and tempeeratures drop, so looks like you're now running a bit lean.
Our modern direct injection gas engines run that way lots of the time, that's how imporved fuel economy figures are emerging.
here's a graph:

http://en.wikipedia.org/wiki/File:Flametemp.jpg


Barefoot

[JamesM]

Sweet!!!! When you get your wideband hooked up, post your timing and AFR targets.

[toon1]

I've been working with Megasquirt with timing and Fueling. The car has been responding well to the changes.

I had to take a trip to the foothills today and decided to take the 914 and really test the changes. Most of the driving I had been doing had been around town so I wasn't sure how the car would respond to a long freeway trip.

while cruising up hwy 5 the cht's were 340.....I pulled up Tuner studios and leaned out the area around cruise a bit. Suprisingly the CHT's dropped about 5 * and were stable.

I kept the setting there and was wondering how this would be when I started climbing hills, again I was suprised how good the head temps were. nothing over 370(which was for a very short time) on the long climbs.

I don't have my 02 sensor connected yet so I can't say what the AFR is.

At the end of the trip, I drove 176miles and it took 4.5 gallons to refill....39.1mpg......NICE!!!

From my combustion chemistry, max combustion tempeerature occurs at stoiciometric A/F, that is wheere exactly the correct amount of oxyger surrounds the fuel molecules , no more/ no less. Either richer or leaner from that and tempeeratures drop, so looks like you're now running a bit lean.
Our modern direct injection gas engines run that way lots of the time, that's how imporved fuel economy figures are emerging.
here's a graph:

http://en.wikipedia.org/wiki/File:Flametemp.jpg


Barefoot

So you may be the guy to ask...

Mt theory is, With enough timing and a leaner mixture at cruise, you are not making a hotter exhaust gas which in turn will make for a cooler discharge.

Am I close?

[toon1]

Sweet!!!! When you get your wideband hooked up, post your timing and AFR targets.

I definitely will. I'm curios also.

[barefoot]

I've been working with Megasquirt with timing and Fueling. The car has been responding well to the changes.

I had to take a trip to the foothills today and decided to take the 914 and really test the changes. Most of the driving I had been doing had been around town so I wasn't sure how the car would respond to a long freeway trip.

while cruising up hwy 5 the cht's were 340.....I pulled up Tuner studios and leaned out the area around cruise a bit. Suprisingly the CHT's dropped about 5 * and were stable.

I kept the setting there and was wondering how this would be when I started climbing hills, again I was suprised how good the head temps were. nothing over 370(which was for a very short time) on the long climbs.

I don't have my 02 sensor connected yet so I can't say what the AFR is.

At the end of the trip, I drove 176miles and it took 4.5 gallons to refill....39.1mpg......NICE!!!

From my combustion chemistry, max combustion tempeerature occurs at stoiciometric A/F, that is wheere exactly the correct amount of oxyger surrounds the fuel molecules , no more/ no less. Either richer or leaner from that and tempeeratures drop, so looks like you're now running a bit lean.
Our modern direct injection gas engines run that way lots of the time, that's how imporved fuel economy figures are emerging.
here's a graph:

http://en.wikipedia.org/wiki/File:Flametemp.jpg


Barefoot

So you may be the guy to ask...

Mt theory is, With enough timing and a leaner mixture at cruise, you are not making a hotter exhaust gas which in turn will make for a cooler discharge.

Am I close?

My comments are only on mixture strength. Timing may have it's own unwanted temperature consequences.
Sorry not enough theory to go on here.

[toon1]

Where's Jake???

I remember him mentioning a while back that it's possible to lean these engines out more than people think.

[gereed75]

There is tons of info in the aviation world about running air-cooled flat fours - Lycoming IO 360 - in the lean of peak ranges (LOP) for EGT.

Google LOP Lycoming IO 360 or go to the Van airforce webpage and you will find volumes.

The bottom line is that EGT's around 30 - 100 F LOP will reduce CHT's with a small reduction in peak power. Detonation is an issue and monitoring CHT is a pretty indirect way to see it.

It works but be careful.

[toon1]

There is tons of info in the aviation world about running air-cooled flat fours - Lycoming IO 360 - in the lean of peak ranges (LOP) for EGT.

Google LOP Lycoming IO 360 or go to the Van airforce webpage and you will find volumes.

The bottom line is that EGT's around 30 - 100 F LOP will reduce CHT's with a small reduction in peak power. Detonation is an issue and monitoring CHT is a pretty indirect way to see it.

It works but be careful.

Detonation??

Are you and wndsfr referring to engine failure???

If so, This is not the case here. I think that I "may" be in the area of 15:1 AFR, if that.

My 02 sensor should be done this w/e. I'm going to leave the settings where they are and check it.

From what I recall Jake saying a few years back was, 15:1 is more than doable with these engines.

[a few loose screws]

Your timing was likely the reason you didn't have any issues with detonation. May not want to advance it more until you can monitor AFR.

[gereed75]

The reason CHT goes down running LOP is that the internal combustion pressure drop significantly. ICP is highest near peak EGT.

Again do some research in the aviation world. They run engines in labs and measure all parameters, including ICP The situation is not exactly comparable because airplane engines sit a drone away for hours at a constant speed and load. An auto engine is more critical since throttle settings constantly move, but the theory is the same

A short period of intense detonation can ruin your whole day

[Dave_Darling]

Detonation??

Also known as knocking, pinging, or spark-knock. Uncontrolled combustion in the combustion chamber; it leads to hot spots and can make the piston push down against the crank at the wrong time. A lot of detonation can melt holes in pistons, heads, or valves.

--DD

[toon1]

The reason CHT goes down running LOP is that the internal combustion pressure drop significantly. ICP is highest near peak EGT.

Again do some research in the aviation world. They run engines in labs and measure all parameters, including ICP The situation is not exactly comparable because airplane engines sit a drone away for hours at a constant speed and load. An auto engine is more critical since throttle settings constantly move, but the theory is the same

A short period of intense detonation can ruin your whole day

Did some reading on the subject and there seems to be some differences of opinions about ROP and LOP. I agree that LOP can create issues BUT I don't think I was even close to being LOP and in the dangerous range.

If I was in danger of being too lean I think I would have noticed lean surging. This was not the case.

Thanks for all the info. when I get the 02 sensor up and running I will post the AFR's.

[barefoot]

Detonation??

Also known as knocking, pinging, or spark-knock. Uncontrolled combustion in the combustion chamber; it leads to hot spots and can make the piston push down against the crank at the wrong time. A lot of detonation can melt holes in pistons, heads, or valves.

--DD

I'll always remember one of our Thermo lab experiments:
We had a variable compression spark ignition test engine (you could adjust the combustion chamber volume by cranking down the cylinder head onto the cylinder.)
It had a pressure transducer feeding signals to an oscilloscope to watch combustion pressure.
Normal pressure wave is a smooth curve with ignition, but as compression was increased to the point of detonation you could watch very rapid pressure spikes of at least double normal combustion pressure. Neat stuff !
Sorry i can't find a neat graph to show.
Barefoot

[toon1]

Detonation??

Also known as knocking, pinging, or spark-knock. Uncontrolled combustion in the combustion chamber; it leads to hot spots and can make the piston push down against the crank at the wrong time. A lot of detonation can melt holes in pistons, heads, or valves.

--DD

This was my first thought....pinging...also known as PRE detonation.

I had none of that going on (IMG:style_emoticons/default/smile.gif)

[r_towle]

What size tires are you running to calculate you MPG?

[toon1]

What size tires are you running to calculate you MPG?

205/65/16....4% over driven.

With previous calcs. with the same tires I was getting 30ish mpg