| Author | Message | ||
     Flapjack |
I am starting this thread at Blakes suggestion, let me say I am not an engineer or chemist and do not claim to be a coating expert. However over the past six years or so we have built a large number of rngines in my shop using coated components. We were skeptical at first but were won over with the results we saw firsthand. increased power & longer part life. Answer to Blakes first question. Yes oil viscosity & volume were the same as used in the test that acheaved highest HP with uncoated piston aand head. Question #2 What was coating thickness? I don't know, I didn't coat the parts but I do know the people that did and I am sure it was properly applied. Coating thickness should range between .001-.0025 max. Coating over .0025 leads to hairline cracks and delamination. Not knowing chamber volume or height of piston to the deck makes exact calculations of compression ratio impossible but they should minor. Question #3 If the coatings are so good why don't the auto companies use them. Answer they do. Both GM and Chrysler have and still use pistons with coated skirts to solve their piston noise problems. One reason they dont coat more parts is cost. Gm is so cost concious that they were only coating pistons in cylinders that had a history of problems. However they found out that in the field they couldn't always get the piston in the proper hole so now are coating all pistons in the problem engines. Chrysler had noise problems with the new v6 in the Jeep Liberty and solved them by coating the piston skirts. Evan a motor compny from Milwauke runs coated pistons in their engines. | ||
| Blake |
Cool. Thanks for posting the new topic. I can see that with a dry film thickness of no more than 0.0025" the CR would be virtually unaffected. As to the question of their use by automobile manufacturers... I was referring to the thermal barrier coatings you mentioned, not solid film lubricant coatings. Buell and probably also Harely-Davidson use solid film lubricant coatings on their stock pistons. I can see how that could improve engine power output and efficiency. How can we explain a 10% increase in engine power/efficiency with the only difference being application of thermal barrier coatings? If such coatings yielded even half of that result, surely every modern automobile engine in existence would be using them. It certainly cannot be very expensive on the grand scheme of things. Wouldn't the Corvette team kill for another 5% of peak HP? | ||
| Hootowl |
I'd like to know that too. Maybe it doesn't do any good to coat parts that don't see a high level of tune, such as an EPA friendly stock motor? I can see how reducing temps of the valve faces and pistons might reduce the tendency to detonate. Would a mild CR modern engine benefit from these coatings? I'm considering these thermal coatings for my next engine rebuild (don't need it yet...knock on wood) as I will be paying Brian and Aaron or Wes and Pammy a visit for this event, and I think they might help with longevity. Do you have any dyno runs you can post? | ||
| Benm2 |
Blake, check Smokey's book. He mentions the thermal barrier coatings there, says they do work but are best left to "experts", due to failure issues (ceramic in oil as grinding compound). The book has a pretty old copyright though. He mentions something about the piston melting above the top ring land. The combustion chamber (including the piston face) is exposed to full exh temp for how long? Maybe 100-degrees of crank rotation before the gas cools from expansion & the exh valve opens. If less heat can escape through the chamber & piston crown, more will go thru the cylinder walls, I'd think. I can't model the thermo flow in my head, I'm not certain that the engine OVERALL will run cooler. The posted info I've seen from the coating companies claim lower operating temperatures, but I haven't found an "all other things being equal" test that quantifies any power gains AFTER the engine is AT stable operating temperature. Total seal piston rings offer a power advantage too, but the major car companies don't seem to be lining up to buy those. Aaron has posted that these rings make more power but require other modifications to take advantage of them, maybe the coatings are similar. But, the PT team used thermal barrier coatings, and that may be enough validation for me. | ||
| Jmartz |
Flap: Are these coatings carbon based? | ||
| Blake |
To clarify... I think the thermal barrier coatings are a great thing to help protect against excessive heat. I just don't see them providing anywhere near a 10% improvement to engine efficiency. Ben, Yes, the cylinder walls would absorb additional heat, but additional heat would also go out the exhaust/tailpipe. More heat would also be available for the power stroke, though I cannot imagine that being anywhere near 10%. Overall the engine temperature should drop. | ||
| Steveshakeshaft |
Jmartz- I imagine the coatings to be metal oxide based? There's a LOT of variables to consider here. If we're talking about reducing engine running temp, then we're either- a) Improving the Thermodynamics of the engine across its 4 cycles. And/or b) Reducing friction. Either scenario should show increased power output for a given air/fuel flow. The trouble is, with a piston crown/combustion chamber coating of .001" to .0025" thick I don't imagine either a) or (particularly) b) effects being THAT noticable. Call me a luddite if you wish. I just don't see it. I have many other points too, but that's enough for now. BTW, I DO want to believe in this technology. Regards Steve steve_s@ukbeg.com http://www.ukbeg.com | ||
| Blake |
I think a little insulation can make a big difference in a transient heat environment, especially one with extreme peak temperatures and an otherwise exposed highly efficient conductor. If the additional liberated heat blocked from transferring into piston, and cylinder head instead goes out the tailpipe, there is no improvement to the thermodynamic cycle, just less heat absorbed and thus shed by the engine and its cooling system. edited by blake on June 30, 2003 | ||
| Steveshakeshaft |
If the Thermodynamic efficiency of a well tuned Buell motor is (say) 35%, we're looking to increase this to 38.5% to get the extra 10% bhp output. And we're claiming this without any increase in volumetric efficiency? (Which afterall, is where flowed heads, race pipes etc make their hp gains). Are we saying that an engine set up by Aaron or Pammy and yielding 100+ rwbhp can instantly become a 110 rwbhp motor with no more work than a .001" coating on top of the piston and inside the chamber? Well, I'd sure like to see the vendor of this stuff offer exactly that, dyno'd and posted right here. Then I might believe it. Heck they'd sell tons of the stuff. How about it? Regards Steve steve_s@ukbeg.com http://www.ukbeg.com | ||
| Blake |
Heheheh. You sure know how to cut through the BS.  | ||
| Blake |
Again, I think the genuine selling point for the stuff is that it does protect the piston against excess temperatures. I'd rather have a coating on the piston face than oil squirters. Maybe I'd rather have both.  | ||
| Steveshakeshaft |
Morning Blake. Simple eh? One of our badweb engine maestros dynos an engine. The vendor of the coating takes the pistons and heads, coats 'em. The engine goes back on the dyno. Everyone gains, no one loses. We all learn. Regards Steve steve_s@ukbeg.com http://www.ukbeg.com | ||
| Flapjack |
Busy, busy, busy. Working 14+16 hours to try & keep up with work, in the middle of vacation schedules & my son is still recovering from his incident so he is only about 25% and going back in to hospital to have his shoulder redone. I'll try to answer all questions in a timely manner. Blake 10% power increase? I am only reporting information I was given. The less efficient a chamber is the greater the increase. Evan if the increase in power is only 5% the lowering of head & oil temps is nothing to sneeze at. If the Corvettes you refer to are the ones with engines prepared by Katech the pistons and domes are thermal barrier coated, I have first hand knowledge of this. Hootowl stockers as well as modified engines benifit from coatings. Ben delamination was a problem with some early ceramic barriers, however that problem has been largely solved with current formulations if they are properly applied. Lmartz- are the coatings carbon based? No they are not. The ones I apply are comprises of ceramic like frit,stainless and aluminum in a carrier. Blake power is increased because more thermal energy is available to push down on the piston during the power stroke after which it is exhausted. teve you are improving the efficiency of the chamber & piston combination. Sometimes only a small gain shows up at first however after tuning changes are made beyond the limits of uncoated parts you are rewarded with added power. Steve great idea, I was going to suggest we need a test. Blake you seem to have the ear of Aaron or Wes perhaps you could broach the subject with them. I am more than willing to partisipate but lets do it more towards fall or winter. Now back to work. | ||
| Steveshakeshaft |
Well that's set then. All we need is a dyno'd engine. I want the technology to work, it sounds good. I can't wait to see the results. Regards Steve steve_s@ukbeg.com http://www.ukbeg.com | ||
| Benm2 |
Blake, like flap said. Hotter air is higher pressure (for a given volume, of course). Higher pressure = more power. Still, a dyno test would cut to the chase, for sure. | ||
| Blake |
Ben, Are you saying that in the few milliseconds during the usable portion of a powerstroke that a thermal barrier coating is going to prevent the loss of 10% or even 5% of the energy of combustion? I agree that it will prevent some, but is it significant to the tune of 5% or 10%? Let's investigate... Let's worst case it and assume that the temperature of the entire piston goes from 400oF to 401oF during the meaningful portion of the power stroke. From that extremely crude yet conservative assumption we can calculate the amount of heat energy absorbed that would other wise have been available to the powertrain. I don't know the mass of a Buell piston sans pin and rings, it's probably less than a half pound. For simplicity let's estimate it at 0.2 Kg. The heat energy required to raise the temperature of 0.2Kg of aluminum alloy by 1oF (0.556oC) is... where... Q is the heat energy absorbed by the piston cp is the heat capacity of aluminum in J/(kg*K) m is the mass of the piston in kg DT is the change in temperature in Kelvin or Celcius With cp equal to 900 J/(kg*K) our estimate becomes... At 6,000 rpm a two cylinder engine would loose energy at the rate of... Okay then. Let's run some dyno testing! | ||
| Steveshakeshaft |
Hmmm. Factor in that with a thermodynaic efficiency of 35% we're looking at 13.4*0.35 = 4.7 HP, still useful eh? Regards Steve steve@ukbeg.com http://www.ukbeg.com edited by steveshakeshaft on July 02, 2003 | ||
| Blake |
It all hinges on how close my heat loss guess is. If it's just 1/10th of my guess, not much there to gain. Funny how it worked out though. Not sure if it needs to be factored or not though since I was only using heat transferred during the useful portion of the power stroke. | ||
| Steveshakeshaft |
I suppose it's academic really, but I think you need to factor in the efficiency. If the heat loss through the piston top is reduced that means the energy retained in the charge is greater, that charge acts on all surfaces not just the piston top, so it needs to be factored by the thermodynamic efficiencly of the engine? What the heck, I just want to see the dyno results now, who cares so long as the power is up! | ||
| Benm2 |
Blake; Thanks for running the calc. My thoughts were wandering to the heat transfer books on my desk, but never made the connection to my hands. Anyway, if you can, try this calc for comparison: Option 1: 1/2" thick Al plate, 400F on bottom side, 2000F on top. What's the rate of heat transfer across the plate? (yes, I know it can't sustain 2000F) Option 2: 1/2" thk composite plate, 0.0025" AlOx coating, remainder Al. What's the heat transfer rate? The real solution is alot more math than I care to think about; as the air expands on the power stroke it will lose temperature as it expands, so the instantaneous heat flow rates will vary as the temperature drops. Then, add in Steve's comments about overall thermodynamic efficiency, and it gets worse. I wonder how scalable results might be? To reduce costs (parts, labor & otherwise) would results from a blast be scalable to some extent? It would be tough to produce absolute results without having bike (or engine) downtime though. I'd think you'd want to test with the same piston, on a "broken in" engine. Low miles, check leakdown & cranking pressure, measure hp. Pull head & cylinder, send piston for coating. Re-assemble, using same thickness gaskets as original (hone cylinders, re-use rings?). Break-in rings, check cranking pressure & leakdown, and measure hp. In order to reduce "sampling error", run each measurement 5-times. (just picked a number, not statistically significant) Then, if you're bored, try it again with a coated head too. Seems like alot of work. I wonder how scalable results would be from a "junk" engine, testing on something "disposable" like an old Honda 110cc one-lunger. You might be able to pick up a "testbike" for free on the side of the road on garbage day, or nearly free at a yardsale. Need something with a throttle & a rear wheel...found a place that will coat one piston for about $35.... | ||
| Peter |
Jack, I finally got around to finishing that header for the turbo. There's some pics here. When I emailed you about it though, your email bounced. Could you email me with a rough price to coat it with something to keep the heat in which is also ok for street use, and an address to send it to please? Pete | ||
| Flapjack |
Pete you've got mail. Jack |
