Coating OEM Pistons
 

Hey guys!

Been reading up about rods only builds for a while and saw a few threads from folks that had coated oem Pistons. It looks like folks did it for a bit and then there has been little mention of it since.

If we ignore the cost argument, ie that cost of coating is about halfway to cost of forged Pistons, which is a valid argument... Is there any benefit to coating oem Pistons if one ignores said cost argument?

It would definitely keep the piston itself cooler :dunno: No added strength I would guess.

Can't find FAB's (Brian) photo of his gold top coat, on this forum somewhere. But plenty of other threads on this subject.

See swaintech info

There's probably some benefit to it. No one really knows (or cares) the extent of it due to reasons we're ignoring.
IMO: when modding a Miata, cost is always a major driver. If it's not, then get a much nicer sports car.

The only way I could see this being worthwhile is if you are building a race engine where you were required to keep the stock pistons, but needed to get every bit of power possible. Otherwise you put money into pistons to have: probably the wrong compression ratio for what you need and are weakish.

The coatings can reduce heat transfer to the metal, and help reduce the coefficient of friction on the piston skirt. Would I spend $200 to coat stock pistons? Probably not, you're near the price of supertechs if you are purchasing pistons too. Would I buy a set already done for $100-150 (like the ones in the classifieds?) I sure would. If I were building an engine right now, I would get those pistons from the classifieds, and rods from the classifieds, a BE pump and some good bearings and have a bullet proof bottom end for about $1200 including machine work.

They can make you slightly more detonation resistant, reduce heat through friction, and look pretty. They wouldn't be as stout as upgraded pistons, but given a good tune I don't see why they wouldn't last. If you're chasing 500whp, ok, go ahead and get upgraded ones. If you're going for EFR 6758 or GT2871 power levels, then I think the stock ones would be fine, and are what I would have used had I not had to bore the block I got.

The pistons out of the engine I blew look fantastic. The rods on the other hand had an odd similarity to the dildofist featured in borat.

Thermal top-coated pistons are standard in every motor I build. Rover's rods-only BP05 has a thermal-coated OEM 8.8:1 piston.

Care to expand on why?
I know you were class limited to HP right? So you could have dropped in forged pistons should you have wanted to go that route.

Thanks!

Explained elsewhere, check my build thread for that car.

Yes.

Yessir.

It increases thermal protection and flame propagation, more even heat distribution, less hot spots. While some would say it is redundant, and probably not necessary, I had my supertechs done. I think it is worth doing. The jackass that negcatted my post above probably disagrees.

Wasn't me, but suggesting that coated stock pistons are safe for "EFR6758" power levels is a pretty sure-fire way to rack up negcats here. I do the coatings to reduce oil temps and add a bit of detonation resistance. They are an add-on to whatever piston is correct for the application, not a bandaid to help you save money by skipping forged slugs when you actually need them.

I haven't seen any evidence that pistons die at xxxwhp, not enough to where I wasn't willing to try them. A shitty tune will kill your pistons anyways, even if they are coated in unobtanium. I was not suggesting for high boost race applications, you wouldn't want them there, and i do believe that i made the point that if you go through the trouble of coating stock pistons, you are most of the way to supertech money anyways. That being said, even though he didn't say it, he was asking about the ones in the classifieds, and I believe with a good tune they should survive 300-350whp. He obviously isn't building a race engine if he is asking about these. They're $100 pistons.

I think 350whp on a cast piston is ill-advised at best. One tiny hiccup and the entire motor is flushed down the drain.

CDM, wouldn't the 6258 be a better comparison here to the 2871? I think they both top out around 350 in a perfect setting, but more likely in the 320-330 range from the dynos I've seen.

But yeah... I'm not looking for 350 wheel lol. I know things would need to look quite different past the 300-325 range. If I decide to go past that range, Pistons will be part of the plan.

I currently have a 2560. I'm likely not going to go bigger than a 2871 since that necessitate a new manifold. And I'd likely get a churbo for that, so I don't expect it to act like a garrett or efr in terms of efficiency.

I was thinking that the 2871 and 6758 were both turbos on average that people use for 350whp. I know they can both do more, and I know you can squeeze the 6258 more. A 2871 should put you in the upper 300's no problem.

My churbo is a 2871. You have to be careful when selecting one. The EMUSA one is an odd duck, for example, and that is the main one floating around out there. I think when I was researching the churbos, it had a 70mm compressor wheel, and the inducer on the turbine was an odd size, and closer in approximation to a T25 wheel than a T28, which I think could be resultant in the shitty spool and midrange we see out of some of the 2871 churbos.

**Does some googling**

For instance the inducer on a 2560 turbine is 53mm, on the EMUSA one it is 52.9mm. The exducer on the turbine of the EMUSA is some odd size between the two. So it is effectively a GT26.570, and while I have never had one apart, or even held a EMUSA turbo in my hand, I can't help but to think if they put a T25ish (T26.5 as I am calling it now apparently) wheel in a generic T28 housing, it would spool like crap.

This is also why some of the chinese 3076 seemingly spool so well for what they are, because they spec out like a 2871 or some odd size between the 2871 and 3076. They never bothered to check the measurements. They also wonder why they only make 300whp at 14 PSI on a 500hp turbo. I've literally seen them to where they are a 2871 with a 4 inch compressor inlet. Interestingly enough, the ones with measurements that are identical to the garrett, usually ship from china, or are the "more expensive" churbos.

My "cheap" turbo upgrade is going to be a JDS 2876 CHRA. I have the compressor housing for the 76mm wheel already. We used one of his 2871 CHRAs on a 2871 on a KA24 and it slid right in, and has been working flawlessly for 2 years now. He also has the extended GTX fins for them.

The 2871R is done by 400whp. The 6758 will press on into the mid-high 400s. The two are not comparable in any way except to say that the 6758 is better in every way (spool, response, power, sexual prowess)

my Supertechs survived a Megasquirt anomaly that ran 18lbs of boost at 14:1 afr for a solid 6-8 seconds. this was long before i knew about efr safety. Today the same pistons look great. short story, forged parts take a beating.

Yeah, didn't Soviet make 450whp on it, and it had a some left to give? Most are making mid 3's on it, that is what I was getting at. The 6758 is going to be more efficient, do it with less boost, and it is more efficient at a higher PR? Sure I maybe falsely assume that most people stop at about the mid 350 area, because when we get to that point, V8 swaps start making far more sense. I was merely comparing the ends to which they are used, and not starting a comparison, which we all know any garret would lose against the EFR, as I have stated in many threads, many times before.


I am 100% glad I have supertechs in my engine. I forgot to hook my wastegate actuator hose up, and berging onto the interstate I gunned it in 4th and HOLYF%^*)(! CRAP WHY IS MY CAR SIDEWAYS. Boost gauge was pegged and out of the corner of my eye I saw a 12.8:1 afr. I hooked up my wastegate and went about my day. Woops. Forged slugs are a great safety buffer to protect you against jackassery. Would have I nuked my engine had I had stockers? I don't know. The E85 probably saved my ass too.

That's what boost cutoff is for!

I've done a few runs with the wastegate disconnected and I'm still here!

CDM and Savington, noted re:2871 and specs all over the place.
Like I said, wouldn't happen for a while. I don't want to get to a point where I run the danger of blowing my 6 speed. Honestly, I'm sure I'll be happy maxing out the 2560. That's still a ton of power.

I know folks have done that with a stock block, but I want to learn to assemble one over the next 6 months or what not, so I'll get to working on things.

Should be conservative. I'm still running brains stock timing map which may even be too conservative. In any event, thanks for all the good info as always.