Ive been searching for some valuable information on the necessity of piston coatings and their validity in street driver, yet high horsepower applications.

For those of you who have experience with this, what are the benefits?

The cost isnt a concern if it, in fact if it doesn't outweigh the benefits. Thanks

 

#1 coating the top of the piston in ceramic like Gold Coat from SwainTech is a huge advantage in keeping the heat in the cylinder and preventing the edges of the valve reliefs from creating hot spots in the cylinder which in turn helps prevent detonation.

#2 Skirt coatings wear off eventually but coating the skirt can and does help prevent the piston from scuffing the cylinder wall when the piston rocks in the cylinder.
Even Mitsu skirt coates the pistons from the factory.

It is not that expensive to do both of these to a set of pistons.
did Gold Coat and PF-9 on the skirts and had the rod bearings PF-9'd by Swain Tech for $300 I think it was.

 

Cool, thanks Tim.


Just the same, I saw in Turbo Mag that their project Supra, they coated the heads from SwainTech as well as the valves.

I figure it'd be about 500 bucks to do all that...but...on a street car?

I dont know...Dave Buschur didnt remark highly of them for high HP street, even some race applications.

It seems the formula for the 2.3 Evo motor has been written and etched in stone...as these things are making HUGE power and lasting dang near forever.

But....an ounce of prevention.

 

I built a couple supra motors back in the day, before 1000 hp was simply "trendy". Had the head/valve facings coated, as well as the piston tops and side skirts, all by Swain. I did suffer a piston failure at the valve relief in the piston prior to the coating, that's why I went ahead and had them coated. No issues after the coating, but the side skirt coating did wear off rather quickly, in less than a 5000 miles on a car driven 4-5 days a week.

Word of note/caution. If you get the gold coat on your piston crowns, it requires heat to thermally set the ceramic coating. I made the mistake (actually my engine builder did) of giving the assembly one last final flush prior to final assembly, to remove any debris. It washed the gold coat right off. It's not made to get wet, not until it has been heat cycled.

It wasn't expensive, I don't remember the cost and it was about 8 years ago, but it's relatively cheap insurance. The time will kill you though! What is it with coaters, they take forever to do anything! Minimum 3 weeks.

 

Basically Ive concluded that the head and valves could afford to have it, and the side skirts become useless.....I can't imagine that the side skirts would benefit too greatly alter the metalurgy to the point where it causes the actual sideskirt itself to be more resilient.

 

Coating the valves would help lean or high egt situations from tweaking the exhaust valves. The piston top coating works great from preventing hot spots which cause knock. The only down side coating the piston top is when you check the plug for signs of knock you won't see any on the plug. The side skirt coating isn't worth it in a street car because it wears off so fast.

 

I know the wiseco's come with a skirt coating, on my old motor it wore off in about 3,000 miles. I spoke with the guys at Swain tech and they seemed to really know their stuff, however, I also spoke with the engine builder at RRE, I believe his name is Rob? He said if you get the piston tops coating and you get any kinda of detonation, that the coating can and will crack off and end up getting sucked thru the exhaust side and into your turbine wheel or it can break up and get into the oil causing it to damage the bearings. It makes perfect sense. In relation to the EVO motors, the valve pockets are soo large that it leaves very little material between the pocket and the top ring, this is pretty much every pistons weak point. I talked to several people about this including Magnus, Pruven and RRE and on all their custom pistons they opted to move the top ring lower on the piston for added strength, rather then using a coating.

 

I have not had much luck with piston coatings in the past. The inherent problem with such coatings is in many cases, the temperature that the ceramic coatings are applied actually effects the integrity of the aluminum in the piston. Although in all fairness, I have not dealt with anything like that in a few years, and I am sure things are a little different now than they were a few years ago. Everything has come a long way...

 

VTECH Killer,

Here is the problem with that statement. The ceramic coating is very thinly applied, somewhere around .001 or less. Even if detonation did manage to damage the ceramic it is not going to do the damage reported by RRE. After a couple thousand miles mine still looked like the day I installed them. My car is currently being road raced and daily driven by the new owner.

 

Yeah, well yours looked like the day you installed them, im guessing your motor ran well. What im saying is, if you get detonation, there is a chance it can flake off. I know its thin, but any debris in your oil will do damage. Im not saying if it gets in your oil the motor is gonna instantly blow up, im saying that it will reduce bearing life. I spun a rod bearing in my motor once, just from spinning the bearing, hearing the knock and shutting the car down, the metal dust in my oil killed the bearings in my turbo. Im talking dust, not chips or flakes, im talking you couldnt even see it in the oil, i stuck a magnet into the oil and a little bit collected on the magnet. and the swain gold coating is .003 thick

 

So help me out this problem since the debate is getting good. I just finished my buildout with manley rods and ross pistons and the guy doing the work mentioned the #1 piston was 3 tenths of a thousandth off but should be OK. Now he believes I am getting "piston slap" that is jacking with my computer because of knock. Do I stick with the Ross and get them coated or go with another precoated piston like wiseco? Have the gt35r but looking to go to the 40r by next spring so I need a piston capable of over 700whp.

 

How can the piston be off? The cylinder should have been hones to size...

Anyway, if you want a stronger piston you need a Wiseco or Mahle but talk to them and let them know what kind of power you plan on making. There are two different forgings they make. I forget the numbers, it's like 8640 or something like that. I am sure someone can chime in and give you the actual number.

 

Weisco pistons come coated already. Or at least in the SRT-4 applications they do.

 

Wiseco's come with a skirt coating. As far as the piston size being off, did the guy bore the block out before you physically gave him the pistons? The correct way, and this is just comon sense, is the machinist measures the piston and then bores that cylinder to spec with the piston. Thats why when people take motors apart the number all the pistons and rods to make sure they go back where they came from.

 

Oh an the other point is, coating is not there to make up an improperly sized cylinder.
It is there to protect the cylinder wall from scuffs when the pistons do make contact.
In the end though the coating doesn't last that long on the skirt. At 5000 miles my skirt coating on the stockers was already worn away on the thrust side.

The real topic of this thread IMO was ceramic coatings on the piston tops.