Thoughts on pinging

[flightdoc]

BD, I think your experiment will be very interesting. I'm from NH and in the summer the fan comes on quite a bit in traffic. You're right, fan comes on , runs for a minute then off it goes for a minute. As long as I'm in slow moving traffic in the heat it keeps that up constantly. I've never had much of a pinging issue though. I run 92-93 octane and keep the revs up a bit especially if it's hot and I've been sitting in traffic. Even though it's gets very cold up here, I store the bike in the garage and it never goes below 40 in the winter.
this is another of your great threads. Keep us up todate.

vin

[blowndodge]

Also: pinging can occur if there's not enough advance (if I'm not mistaken.) The mix explodes before the plugs fire, never giving it a chance to actually burn.

You are mistaken, barely. "the mix explodes before the plugs fire because the combustion chamber is too hot, "dieseling". If it's caused by timing issues it's always advanced too far.

Lots of advance ie: spark plug firing before TDC (top dead center) allows more torque and the pistion is fighting the flame front earlier in its rise to the top. this increases torque but causes more heat. Heat is the energy converted to pushing the piston down.

The less timing means the burn starts higher up the the piston travel and produces less resistance and thus less combustion pressure and lower temps and lower power output.

clear as mud???

Yeah, that's "pre-ignition" or 'pinging". Dieseling is when it runs on without a spark at all. (After you shut of the ignition.) It's really the same thing: the mix just explodes because it's so hot, or there's a hot spot in the combustion chamber. No spark is required.

But of course pre-ignition is not always caused by too much advance. If there's a hot spot or carbon buildup or a too-lean mix, extra-hot intake air, or not enough cooling (all things we've discussed) it can ping.

I'm just thinking that an engine that's on the verge of too lean (like the Nomad FI) could ping when it otherwise might burn, if the spark is a tiny bit late. A lean mix takes longer to burn, so demands more advance. OTOH, you're right in thinking that too much advance under heavy load will usually cause pinging. Sooooo...

Vacuum retard anyone?

(I stole this from some Jaguar article to illustrate the point:)

"Vacuum retard was used on the V12 XKE also. However, it was a smarter system as it had a thermostat system on the right rear of the engine. This system disabled the retard system when the engine got to hot. This in effect advances the timing allowing the engine to run cooler and at a higher idle."

Just like too much advance can cause excess heat, so can not enough. The Nomad has little advance and may just fall in the "not enough" category.

[blowndodge]

I own a diesel. I thought you would understand the metaphor "dieseling" or spontaneous combustions without an ignition source is essentially the same as pre-ignition. I'll be clearer.

On the Jag that feature was exclusively for overheating after running hard and coming down to idle speed. It was not wise to shut off the motor so the increase in vacuum idle speed and advance was it's way to cool down the engine but only at idle.

Actually a lean conditions burns the exact opposite. Very quickly, too quickly. The use of premium slows down this violent quick burning lean mixture. Lean conditions have a less steady flame front and the burn can actually happen all at once as oppose to one side of the piston to the other side like it should. Richer mixtures are harder to ignite, burn slower and thus usually foul spark plugs quicker do to the soot in the richer mixture.

I'd be willing to bet that if the ECM had a knock sensor this sensor would retard the timing as oppose to advancing it if it detected pre-ignition.

[nomadd]

I own a diesel. I thought you would understand the metaphor "dieseling" or spontaneous combustions without an ignition source is essentially the same as pre-ignition. I'll be clearer.

On the Jag that feature was exclusively for overheating after running hard and coming down to idle speed. It was not wise to shut off the motor so the increase in vacuum idle speed and advance was it's way to cool down the engine but only at idle.

Actually a lean conditions burns the exact opposite. Very quickly, too quickly. The use of premium slows down this violent quick burning lean mixture. Lean conditions have a less steady flame front and the burn can actually happen all at once as oppose to one side of the piston to the other side like it should. Richer mixtures are harder to ignite, burn slower and thus usually foul spark plugs quicker do to the soot in the richer mixture.

I'd be willing to bet that if the ECM had a knock sensor this sensor would retard the timing as oppose to advancing it if it detected pre-ignition.

Agree 100% BD. IMHO the installation of a Power Commander III would do away with almost all of the pre-ingition problems. I have one on my Nomad running with a map for my V&H exhaust and I have to say the only time I have heard the engine ping was on a day with 100+ temps while I was lugging the engine. The engine runs like a champ with the PC. I do run 93 octane fuel all the time but I also live <100ft. above sea level. When I ride in the mountains of New Hampshire (which is often) I sometimes run premium fuel that is only 91 octane without problems. The nice thing about the PC is that you can take it to a tuner and create a custom map taylored to your specific needs. Come on boys, dig down deep in them pockets and spring for a PC. I don't think you'll be dissapointed.

[ells]

Posted this on the Pinging Poll but may be more on-topic here

I just ran a tank of 85 oct (normal regular here) and all seemed to be okay, 5500 ft. elev. Maybe slight power loss but could very well be my imagination. Then, near the end of the tank I did some stop and go city driving and fan kept coming on in 50F weather. Never did that before. Then on a couple starts from stop lights I heard a faint but unmistakable little ping. That was it, pulled into the next Shell station and filled back up with 87 - end of that experiment.

[flightdoc]

The only time I ran 87 octane was a hot (80) and the wife was with me. Pinging like crazy. Never ran that low of an octane again.

I own a diesel. I thought you would understand the metaphor "dieseling" or spontaneous combustions without an ignition source is essentially the same as pre-ignition. I'll be clearer.

Sorry BD. I came off as a smarta$$ there and I didn't mean to. I've operated lots of diesel equipment and lived in the desert so I've heard lots of dieseling from hot gas engines too.

On the Jag that feature was exclusively for overheating after running hard and coming down to idle speed. It was not wise to shut off the motor so the increase in vacuum idle speed and advance was it's way to cool down the engine but only at idle.

The way I read it, it kicked in whenever the engine was hot and vacuum high. Not just at idle, though of course the vacuum is high at idle that's not the only time.

Actually a lean conditions burns the exact opposite. Very quickly, too quickly.

OK. From what I read it actually burns slower, unless of course it *pinged* which meant it simply exploded instead of burning. Definately a case for using high octane gas.

I'd be willing to bet that if the ECM had a knock sensor this sensor would retard the timing as oppose to advancing it if it detected pre-ignition.

I'm sure you're right. This is what my EFI car does. Do you think we could rig a knock sensor that would swap a resistance in and out of the air temp sensor circuit, temporarily faking the computer into altering the timing/mixture? What about the coolant temp sensor? Does the computer actually read that on a Nomad to help setting mix/timing? Or does it just control the fan?

IMHO the installation of a Power Commander III would do away with almost all of the pre-ingition problems. I have one on my Nomad running with a map for my V&H exhaust and I have to say the only time I have heard the engine ping was on a day with 100+ temps while I was lugging the engine.

Having a TFI has eliminated 95% of all pinging I had stock, but I routinely ride across town, in stop & go traffic on days above 100^oF and while stopped in a pack of cars the air temps go well above 120 I'm sure. That's when I can still easily make it ping.

The other time is on a similarly hot day, when riding the open road with a passenger, and accelerating really hard (pinning the throttle) in the upper gears say from 60~90 MPH. Then it will definately ping.

In more normal riding, it never does.

Not that a TFI is the equal of a PC-III. It's a much less sophisticated device AFAIK. But, man, it'a dang sight better than jetting a bike with 4 carbs! I don't miss those days at all.

[blowndodge]

Wouldn't a knock sensor be cool!!?? I'd love to be able to put a fuel processor on and be done with it but........

I'd be interested in the TFI. Gadget has shown that on his old 1500 he ran about 14 to 1 across the board which is ideal.

I remember the jetting of yesterday at the drag strip. i got pretty quick at it but still a pain.

Mine pings like yours in those conditions as well. that's why I think that the water temp sensor is the major player in the ECM.

I purchased a pack of 330 ohm resistors the other day at radio shack. When my water temp goes to 212 the extra 330 ohms to the ECM should tell it that the temps only 150-160 degrees. Until the fan goes on my bike doesn't ping much so I think the very low resistance from the sensor is causing a full lean out. Bumping the ohms back up to 550 ohms should work?!!

As on an earlier post, the fan is on a total seperate circuit and the sensor is on the bottom of the radiator.. The water temp sensor is on the side of the thermostat under the tank but you can splice into it at the ECM. Its the orange wire in #7 pin.

Oops! I thought the resistor mod involved splicing into the air temp sensor circuit.

[blowndodge]

both circuits water and air.

Veeeeeery interrrrrrresting!

[dhelfritz]

I live is South Florida and my bike pings on hot days, particulary on 5th gear rool ons. In the heat down here the fan runns alot. Sometimes at stop lights it feels like your thighs are burning. If I stop for a drawbridge, I turn the bike off. You really feel the heat in Fl.

[blowndodge]

that is typical of Nomads. Hot hot hot....