Don Terrill’s Speed-Talk

Assumption: Temperature is the cause of pre-ignition / detonation of a given fuel; CR, DCR, all the other indicators have rough coorelation to pre-ignition /detonation

Or to say it another way: the temperature of the fuel being raised beyond the point at which the fuel spontaneously combusts is the CAUSATION of pre-ignition; the other factors are merely COORELATION to what we should actually care about.

This is mostly correct, except the heat that causes the detonation comes from the retained heat in the combustion chamber area.
Then it sets off the mixture prematurely before the spark plug fires.
With a correctly working coating, the surrounding combustion chamber would be cooler than with a non-coated one.
All the extra heat from the correct actual combustion process would push harder on the piston for more power, and the rest would go out the exhaust like now.

The gains would be more than 10 HP probably?
2/3rds of the actual combustion process of gasoline is wasted heat. Gaining even 10% of that would be huge?

Looks like Madbill covered a lot of my explanation.

Auto-ignition is the cause of pre-ignition and detonation and is caused by a combination of temperature, pressure and time. As MadBill pointed out, the only difference between the two is when it occurs. Assuming a fixed mixture strength and fuel and cam timing, the solution for abnormal combustion is to reduce any one of the three parameters. Higher engine speed reduces the time, as does reduced ignition lead which also reduces pressure. By itself, a lower CR reduces pressure and temperature, but generally requires earlier ignition . . . which then increases pressure, temperature and time. I can't think of any one change that doesn't have multiple effects.

A thermal barrier will reduce the temperature of the mixture prior to ignition and hopefully increase average cylinder pressure resulting in more torque, but I have no data on what it does to peak cylinder temperature or pressure. Beyond that, the timing of peak temperature and pressure will change with the addition of a thermal barrier. There's that time factor again.

At one time was on the sidelines of testing temp coatings of the piston tops, pistons under sides, combustion chambers, valves.
The final word I received was the only improvement was coating the back side of the piston. If you have ever noticed the baked on brown color of a an uncoated piston is fried oil. The coating of it I guess reduced oil temps but never any info on if it required timing/ compression tweeking.

4sfed wrote: ↑Tue Nov 07, 2017 5:11 pm Auto-ignition is the cause of pre-ignition and detonation and is caused by a combination of temperature, pressure and time.

Detonation is auto ignition of the remaining gasses but after the plug fires.


Oil squirters have another advantage in that you can run with tighter clearances without getting the piston stuck in the bore due to getting too hot and too big.
Coatings are mainly snake oil.
What happens when the coatings start falling off?

joe 90 wrote: ↑Tue Nov 07, 2017 7:26 pm

4sfed wrote: ↑Tue Nov 07, 2017 5:11 pm Auto-ignition is the cause of pre-ignition and detonation and is caused by a combination of temperature, pressure and time.

Detonation is auto ignition of the remaining gasses but after the plug fires.

If you read past the first sentence ...

4sfed wrote: ↑Tue Nov 07, 2017 5:11 pm As MadBill pointed out, the only difference between the two is when it occurs

joe 90 wrote: ↑Tue Nov 07, 2017 7:26 pmCoatings are mainly snake oil. What happens when the coatings start falling off?

Properly applied they don't.

NewbVetteGuy wrote:


Assumption: Temperature is the cause of pre-ignition / detonation of a given fuel; CR, DCR, all the other indicators have rough coorelation to pre-ignition /detonation

thermal barrier coatings create more even temps, reducing hot-spots and this attribute helps to reduce the likelihood of pre-ignition. If your pre-ignition was because of a hot-spot, thermal barrier coatings might help;

Adam

I think it could go either way.
I've read several SAE articles that seemed to indicate detonation can be caused by cold /rich spots. The cold/rich spots don't burn and BECOME the "end gas" that spontaneously ignites.

I agree a "more even temperature" would certainly be good, but that would be the cold spots are hotter and the hot spots are colder. Does it do that?

Very smart questions, I am impressed.

4sfed wrote: ↑Tue Nov 07, 2017 8:00 pm
Properly applied they don't.

It's like Murphy's law.

If something CAN fail then it WILL fail.

How many heat cycles will it take before it flakes off.
It's all about the difference in the coefficient of expansion of the piston vs the coating.

Then more importantly.......where does it go.
Ceramics are hard and abrasive.


If it's a dedicated race car then maybe it doesn't matter.
Waste of time though for a daily driver.


It's no different from me telling kids that cast iron manifolds are the only way to go for a turbo.
Why?
Because fabricated ones always end up either cracking or warping at the flanges or more often .....both.
Then they leak and they become totally useless.
The only variable is the number of heating and cooling cycles before it happens.

Where I live I'm at 300 feet above sea level.
To go anywhere ...like to work.......I have to climb to 600 feet then drop to sea level........all over about 4 miles.
Then to come home again, it's the opposite.
I've been doing it nearly every day for over 30 years, sometimes more than once.
That's like 10,000 dyno pulls of 2 minutes each.


Ok, so if all you ever do with the car is go to the supermarket, maybe it won't happen.

joe 90 wrote: ↑Wed Nov 08, 2017 2:45 am It's like Murphy's law.

If something CAN fail then it WILL fail.
Ok, so if all you ever do with the car is go to the supermarket, maybe it won't happen.

Not my experience with multiple turbo street cars that regularly see track events. YMMV

John Wallace wrote: ↑Mon Nov 06, 2017 2:58 pm

Assumption: Temperature is the cause of pre-ignition / detonation of a given fuel; CR, DCR, all the other indicators have rough coorelation to pre-ignition /detonation

Or to say it another way: the temperature of the fuel being raised beyond the point at which the fuel spontaneously combusts is the CAUSATION of pre-ignition; the other factors are merely COORELATION to what we should actually care about.

This is mostly correct, except the heat that causes the detonation comes from the retained heat in the combustion chamber area.
Then it sets off the mixture prematurely before the spark plug fires.
With a correctly working coating, the surrounding combustion chamber would be cooler than with a non-coated one.
All the extra heat from the correct actual combustion process would push harder on the piston for more power, and the rest would go out the exhaust like now.

The gains would be more than 10 HP probably?
2/3rds of the actual combustion process of gasoline is wasted heat. Gaining even 10% of that would be huge?

Thanks John and Madbill!

This is how I learn the fastest; just throw my understanding out there and have the experts pick it apart and help clarify where I went wrong.

Now I just need to find a good place that can coat my heads out here in Seattle; I'd love to go with Swain but that 1,500 miles between me and them is a lot of added hassle, risk, and cost.


Adam

Is there any credible research on combustion chamber and piston TBC coatings ever helping the maximum power of a knock limited gasoline engine? For that matter, is there any credible research that someone could point me to that documents the iron heads making more power than aluminum heads in a knock limited gasoline engine, with compression, ignition, and fueling optimized? I'm curious, I'd like to read something systematic about this.

Right, I'll even take questionably credible research, as long as it's not fake
IT COULD BE, that once you reach the theoretically optimal CR, which is usually somewhere between 12-14, then maybe insulation of the surfaces could be worth something.

For evidence against the insulated piston, I simply note that most all pump gas high performance engines are made of aluminum, including the cylinders. Far as ideal thermal gradients, IMO the vega might have been the right combo and I'd love to see "proof" otherwise

ptuomov wrote: ↑Thu Nov 09, 2017 11:11 am Is there any credible research on combustion chamber and piston TBC coatings ever helping the maximum power of a knock limited gasoline engine? For that matter, is there any credible research that someone could point me to that documents the iron heads making more power than aluminum heads in a knock limited gasoline engine, with compression, ignition, and fueling optimized? I'm curious, I'd like to read something systematic about this.

I can't state as fact, but you may find a credible, hands-on post about coatings/results in the NASIOC.com forum. Subarus are notorious for being knock limited, rod bearing eating, poor oil control, etc. They have some pretty sharp guys there.

My empirical before/after evidence of Swaintech coatings (chambers, crowns, intake/exh ports) used in a bone stock EJ207 with VF-37 twin scroll on 27 psi....was I had to add fuel (E85), my EGTs went down and it looked fabulous on tear down. I didn't really expect that on E85.

n2xlr8n wrote: ↑Fri Nov 10, 2017 7:30 am

ptuomov wrote: ↑Thu Nov 09, 2017 11:11 am Is there any credible research on combustion chamber and piston TBC coatings ever helping the maximum power of a knock limited gasoline engine? For that matter, is there any credible research that someone could point me to that documents the iron heads making more power than aluminum heads in a knock limited gasoline engine, with compression, ignition, and fueling optimized? I'm curious, I'd like to read something systematic about this.

I can't state as fact, but you may find a credible, hands-on post about coatings/results in the NASIOC.com forum. Subarus are notorious for being knock limited, rod bearing eating, poor oil control, etc. They have some pretty sharp guys there.

My empirical before/after evidence of Swaintech coatings (chambers, crowns, intake/exh ports) used in a bone stock EJ207 with VF-37 twin scroll on 27 psi....was I had to add fuel (E85), my EGTs went down and it looked fabulous on tear down. I didn't really expect that on E85.

With a twin scroll and E85, you weren't very knock limited, right? The twin scroll (and the long pipes) eliminate the exhaust blowdown interference and E85 evaporization cools so much. So this may be closer to the diesel case than pump gas case.

Out of curiosity, did you have to add fuel because of insufficient evaporization or to keep the AFR the same?

I have used Tech-Line Cer-Met coating on chamber, valves , and piston crown, and ceramic only TBC in the exhaust port of every one of our 50 street performance single cylinder aircooled engines for 10 years.

We have never done a/b dyno tests for hp difference. However, we were able to get lower head temps, which I believe helped the engine to take more compression on pump gas than our competitors engines.

My partner Joe Mondello worked on this with me, and the consensus was that this combination of 2 different coatings in different areas was the right way to go in a very difficult application.

In general, a cooler head temp led to less heating of the intake mixture, helping to reduce propensity to have pre-ignition. The cer-met coating has some insulation property that not only helps reduce head temp by slowing thermal transfer, but even a partially effective insulator acts very well during the "flash" peak combustion period where there is extremely high temps and very little time at those peak temps. This helps reduce heat transfer at the extreme delta-t periods wich define rapid heat transfer. Even partial effectiveness at these times is a pretty big deal in aircooled environment. The same is true for the cer-met on the piston. We had virtually zero overheating seizures with this due to less thermal expansion at the skirt on our 2618 forged slug.

Additionally, the metallic (al) component of the cer-met acts to reflect the heat back to the interior of the chamber from the coated chamber/valves/piston, making a better environment for more complete combustion, reducing propensity for detonation, from reduced unused end gas . And the metallic particles are extremely low mass and high thermal conductivity so they give up their heat very quickly during the overlap.

All said and done, my assessment is that it may have helped power in a variety of small ways which just helped the overall application. But it definitely helped in reliability by mitigating heat related problem in a difficult aircooled hemi (no squish) large(105cc) chamber street engine.