340 Pinging using 94
- Thread starter dterry1
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dterry1
Active Member
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Inertia
Well-Known Member
Misunderstood Causes of Detonation in High Performance Applications
In the engine tuning world, detonation is the uncontrolled and often unwanted igntition of the air-fuel charge, which can cause significant damage.
www.enginelabs.com
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dterry1
Active Member
"One thing to understand is that detonation is not necessarily destructive. Many engines run under light levels of detonation, even moderate levels. Some engines can sustain very long periods of heavy detonation without incurring any damage. If you've driven a car that has a lot of spark advance on the freeway, you'll hear it pinging. It can run that way for thousands and thousands of miles. Detonation is not necessarily destructive. It's not an optimum situation but it is not a guaranteed instant failure."
Very interesting, thank you for that resource
Tuning or it's because you're in the big block section.
some good advice here, but may find more in the little engine section.
some good advice here, but may find more in the little engine section.
dterry1
Active Member
"The best indication of detonation is the pinging sound that cars, particularly old models, make at low speeds and under load"
Doesn't this mean that when I get off the gas and am coasting at low speed, and am hearing pinging, it is still detonation?
Tuning or it's because you're in the big block section.
some good advice here, but may find more in the little engine section.
dterry1
Active Member
Tuning or it's because you're in the big block section.
some good advice here, but may find more in the little engine section.
I'm not sure if you read the entire thread, but I did accidently click 1 thread off of where I meant to click.
But the people here have been just as helpful as the people in a different size engine thread.
Inertia
Well-Known Member
Conclusion
Detonation can cause catastrophic engine failure if left unchecked. That’s why most modern engines incorporate a failsafe in the factory tune to retard ignition timing or add fuel when a knock sensor detects too high of a knock count. To prevent knock on modified engines, a tune is required to adjust the factory calibrations and bring your engine into equilibrium with your new mods.
Detonation can cause catastrophic engine failure if left unchecked. That’s why most modern engines incorporate a failsafe in the factory tune to retard ignition timing or add fuel when a knock sensor detects too high of a knock count. To prevent knock on modified engines, a tune is required to adjust the factory calibrations and bring your engine into equilibrium with your new mods.
Inertia
Well-Known Member
Not sure what you're hearing, but I'm very sure it isn't "ping" under decel, hence the vid.
More likely exhaust leak .
dterry1
Active Member
The case for Pre-ignition is also very interesting. In my case, for the first few accelerations there is no pinging. But as the drive continues, that is when the pinging starts.
It's about 1-3 minutes of no pinging where I think in my head "yes I finally fixed it", then it starts again...
It's about 1-3 minutes of no pinging where I think in my head "yes I finally fixed it", then it starts again...
LJ67barracuda340
Well-Known Member
does it have stock manifolds with a noisy heat riser valve.?
You're cool, I'm just being me. You're in good hands I think the guy's got you covered.
OldmanRick
Well-Known Member
Nice catch on the heat riser.
OP - so now comes the unwanted English lesson. What it says is low speed AND under a load, not low speed OR under a load. They mean both things at the same time.
Thought #1 - Are you trying to made this car exactly like it came from the factory? If not (and I know there will be some howling here) just replace the system with a factory electronic ignition. If it's a 72 it would have come with it if it was built later in 72. You can go to @halifaxhops (another member, who builds Mopar distributors all the time) and buy everything you need to convert it and, if you answer all his questions, he will deliver a distributor that you know has an advance curve that fits your car. This will save a HUGE amount of time and money because you don't have the equipment and knowledge to fix this. You have to get rid of detonation because it will eat your engine. I'm already worried because you have driven it like this through 3 tanks of gas!!!
Thought #2 - yeah send the video because if it's not detonation it would be great for you to fix whatever is wrong.
I already asked what the distributor is a number would help tremendously if it is unmolested.
RAMM
Well-Known Member
This ^^^^^^^^^^^^^^^^^^ right here.
Pinging while coasting is not combustion related. You have mechanical metallic thingys touching each other. I knew a guy once that thought he had "pinging" while decelerating which is IMPOSSIBLE BTW.....Turned out to be the flex fan just nicking the fan shroud.
As mentioned--cranking compression would tell me all I need to know. I hate threads like this that suck me in and leave me hanging. Lol. J.Rob
If you have time can you do the cranking compression test please. While the spark plugs are out record the number on the spark plug and report back. Couple of pictures of the spark plugs would be nice. if you can get some timing numbers through the rpm range that would be awesome. I'll bring this up. Do you know how to check the tdc mark on your balancer? If you do, check it before you do the timing check otherwise don't worry about it just yet.
Likely The reason the ping doesn't happen until the engine warms up is because the combustion temprature is lower. Higher combustion temps will bring you closer to the conditions necessary for ping to occur. A manifold heat cross over valve stuck closed will increase combustion temps. Do you know if you have one of these in your exhaust system. Or maybe you have headers? A picture of the engine would be nice.
The fact that the pinging doesn’t start until the motor is warmed up and reducing the timing reduced the severity of the ping does lean towards the sound that your hearing as actually being ping. However it could still be something else. More information would help narrow it down. Good luck.
I
Likely The reason the ping doesn't happen until the engine warms up is because the combustion temprature is lower. Higher combustion temps will bring you closer to the conditions necessary for ping to occur. A manifold heat cross over valve stuck closed will increase combustion temps. Do you know if you have one of these in your exhaust system. Or maybe you have headers? A picture of the engine would be nice.
The fact that the pinging doesn’t start until the motor is warmed up and reducing the timing reduced the severity of the ping does lean towards the sound that your hearing as actually being ping. However it could still be something else. More information would help narrow it down. Good luck.
I
I agree more load gets you closer to conditions that cause ping. So can leaner fuel mixtures. I have never experienced ping when actually "coasting". If what the op describes as coasting is actually coasting it's not likely what he is hearing is pinging.
I have experienced pinging at light throttle and had it disappear with moderate throttle (increased load). I suspect due to the power valve opening making the air fuel ratio richer. I can't confirm that so it's just a theory. It could be the op's "coasting" is just reducing throttle position and speed just enough to close the power valve while still having enough load to cause ping. Hows that for a conspiracy theory?
TT5.9mag
Two atmospheres are better than one
Detonation is most likely to occur at or near peak cylinder pressure which is where peak torque is. VE is highest at peak torque which is why cylinder pressure is at its highest. Lower RPM higher gear and introducing load (like climbing a hill with out downshifting) is when detonation will happen. You can make a 14:1 iron headed big block idle around town on 94 octane. I’ll say it again, if the noise he experienced happened on deceleration, is isn’t detonation.
Inertia
Well-Known Member
If someone opened a thread with a 5 second video, and asked " what's this noise" ?
We wouldn't be at 60 posts, he wouldn't have bought a set of now useless plugs .
Just saying . . No offense to anyone, we are all here to help .
We wouldn't be at 60 posts, he wouldn't have bought a set of now useless plugs .
Just saying . . No offense to anyone, we are all here to help .
TrailBeast
AKA Mopars4us on Youtube
That’s exactly what I thought when I read that.
Engines don’t ping under deceleration because the cylinder pressure is way lower.
2 things can cause the fuel to fire off.
Heat and pressure.
This is why we are questioning that it’s actually pinging.
Inertia
Well-Known Member
OP , hi, - I changed the detonation link.
When I posted that link on detonation, it wasn't the link I wanted, it was "not found".
It seems to have changed its name/address, which I have since found.
I found it more helpful than the one I scrambled for, and originally posted.
Good luck, cheers.
Misunderstood Causes of Detonation in High Performance Applications
In the engine tuning world, detonation is the uncontrolled and often unwanted igntition of the air-fuel charge, which can cause significant damage.
www.enginelabs.com
Jim Lusk
Well-Known Member
Like I explained earlier, I'd highly suspect the distributor. That's at least a place to start. Check dwell or just replace with a known good one.
Yup.Once I see many questions asked and I've asked some too and there are no answers, I mark the thread off my list. I'm glad there's an "ignore thread" option.
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