Why does pinging occur on hot days
Why does pinging occur on hot days I cannot reason why pinging is more prevalent on hot days. Wouldnt cylinder pressures be higher on cold days? I did a quick google search and remain stupid. Can anyone explain the basic physics?
TECH Apprentice
Joined: Jun 2009
Posts: 318
Likes: 5
From: Oklahoma
Can you hear the nock or are you logging data and can see the timing retard? Do you have a MAF or SD tune?
How about this: we tune to an afr of 12ish to one. Stoich is 14ish to one and is more prone to knock because it is ideal. So somehow hotter less dense air is leaning the mix? That has to be sensors, right?
My tune is maf, but my question is physics. Less oxygen =? Leaner mix...wut? I can see the KR on torque pro and I can for damn sure hear it.
Squirlnutz...howdy from a fellow okie. Im from mwc.
My tune is maf, but my question is physics. Less oxygen =? Leaner mix...wut? I can see the KR on torque pro and I can for damn sure hear it.
Squirlnutz...howdy from a fellow okie. Im from mwc.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
You'll run richer in hotter air. Your O2s *should* compensate for this and pull fuel. However, you'll most likely pull timing as the knock sensors will pick up the ping before the fuel trims are adjusted.
TECH Apprentice
Joined: Jun 2009
Posts: 318
Likes: 5
From: Oklahoma
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TECH Apprentice
Joined: Jun 2009
Posts: 318
Likes: 5
From: Oklahoma
BTW.
This won't necessarily help with this post but if you haven't posted here
https://ls1tech.com/forums/showthrea...500236&page=38
Then you should. Lots of Okies on tech.
This won't necessarily help with this post but if you haven't posted here
https://ls1tech.com/forums/showthrea...500236&page=38
Then you should. Lots of Okies on tech.
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So again my question is mainly physics. My car is set to kill (30 degrees timing, tuned in November in new england) and had tr55s which I specifically requested not be used...so its no surprise its pinging...retune with meth and tr6ix plugs/new wires is friday... the old stuff had nearly 1500 miles on it, lol.
I believe all that LA humidity might help with ping, but not that heat. You may be right in that I could also have some carbon buildup from just cruising around with the wife and dog ..not a lot of places to hammer high whp cars up here in new england. My state has more cops per capita than any other.
Running rich should not cause ping. Thats my whole point, rich is cooler. So is whats happening is that the sensors are over compensating and leaning it too much? If that is the case 1) what good are the sensors? 2) does an SD tune do this?
Or is it a two step process: hot air runs rich which deposits carbon which causes hot spots. This scenario seems less likely.
I believe all that LA humidity might help with ping, but not that heat. You may be right in that I could also have some carbon buildup from just cruising around with the wife and dog ..not a lot of places to hammer high whp cars up here in new england. My state has more cops per capita than any other.
Running rich should not cause ping. Thats my whole point, rich is cooler. So is whats happening is that the sensors are over compensating and leaning it too much? If that is the case 1) what good are the sensors? 2) does an SD tune do this?
Or is it a two step process: hot air runs rich which deposits carbon which causes hot spots. This scenario seems less likely.
Well if I had to take a guess, I think that your engine is running hotter in general on a warm day. I'm sure that the environment that the combustion occurs in also affects things, besides the incoming charge of air and fuel.
Launching!
Joined: May 2012
Posts: 209
Likes: 1
From: NC
Only after the IVE builds pressure inside the chamber then does dynamic compression come into play where you're compressing a mixture of fuel and air into a dedicated chamber volume + headgasket thickness.
When you're comparing 8.5:1 you're giving a constant of volumetric reduction by compression into a very small volume.
If the head or piston has a hot spot, it will cause pre-ignition which is heard as pinging. If the air is less dense and is not providing a cool enough charge to cool the piston face and chamber, it can lead to higher chances for pinging and decreased efficiency due to the air being less dense.
Also chemistry is highly involved in this process. The fuel you're using, its cooling properties, its efficiency to burn and not release excess carbon molecules, etc. are also involved.
Even the piston face design plays a large part in combustion efficiency and controlling the compressed mixture for combustion. Head design and flow efficiency for enough swirl, tumble, and other factors play a part in proper chamber filling in effort to help with piston face cooling and chamber efficiency.
There are many factors that come into play, timing is just one small component of the larger picture.
How about this: we tune to an afr of 12ish to one. Stoich is 14ish to one and is more prone to knock because it is ideal. So somehow hotter less dense air is leaning the mix? That has to be sensors, right?
My tune is maf, but my question is physics. Less oxygen =? Leaner mix...wut? I can see the KR on torque pro and I can for damn sure hear it.
Squirlnutz...howdy from a fellow okie. Im from mwc.
My tune is maf, but my question is physics. Less oxygen =? Leaner mix...wut? I can see the KR on torque pro and I can for damn sure hear it.
Squirlnutz...howdy from a fellow okie. Im from mwc.
If you don't comprehend the fact that stock CRUISE ratio is 14.7:1 maintained through feedback from the O2 sensors and that 12-13:1 are WOT power enrichment ratios then you need to go back to basics before you even begin to think about this.
Short version is if your car pings on hot days but not cold there is either a mechanical issue or the tune is **** and not adjusting things like timing properly for varying temperatures. Such issues are common with cheap tuners. I used several different tuners with my LT1 and once I found a guy who was thorough the car became MUCH more consistent in varying weather. Use a shitty tuner and they don't tweak all the necessary tables, it gets warm the engine pings, the pcm pulls a lot more timing than really needed say 5 degrees. Use a good tuner and they dial back the timing 1-2degrees in hot temps it doesn't ping and the car stays more consistent because the timing is not being excessively lowered.
pinging can hammer the hell out of bearings and pistons.
SS10Tech and RedhotG8 thank you for the cogent responses. These seem to make the most sense from a physics perspective, which is what this thread was (supposed to be) about.
TECH Addict
Joined: Mar 2013
Posts: 2,628
Likes: 30
Actually it happens AFTER the spark plug fires. The mixture in the cylinder is a little too hot and the carbon in the cylinder is hot, as the plug fires and adds more heat instead of the mixture burning evenly across the piston it explodes in one big bang. That noise you hear is actually the explosion inside the cylinders.
The sooner the plug fires before TDC the higher the cylinder pressure and heat.
The reason backing off the timing stops "PINGING" is firing the plugs later reduces the amount of pressure and heat in the cylinder. So as the plug fires the mixture is cooler and stays under control. "PINGING" is the mixture burning out of control.
The sooner the plug fires before TDC the higher the cylinder pressure and heat.
The reason backing off the timing stops "PINGING" is firing the plugs later reduces the amount of pressure and heat in the cylinder. So as the plug fires the mixture is cooler and stays under control. "PINGING" is the mixture burning out of control.
TECH Senior Member
Joined: Mar 2004
Posts: 14,620
Likes: 17
From: BFE
TECH Fanatic
Joined: Aug 2012
Posts: 1,334
Likes: 1
From: Wildomar, CA
It's the sensors. They read temp barometric pressure and airflow. If its hot your car will pull timing and fuel to compensate. It would be like going up in elevation several thousand feet. Hot air is thinner. You just need to toss it on the rollers again and dial in the tune.
