trying to find out what would be the best for a s5 turbo engine rebuild, the goopy refinish has some good reviews but the turblown coating claims a penetration depth of .005-.50" with an overbuild of .0002-.0007".

It seems like the trublown coating would fill some imperfections in the housing surface and provide superior service life vs the goopy refinish probably provides better apex seal seating. Service life vs higher compression numbers?

 

service life generally isn't the problem with the resurfacing, it is the original condition of the housings. FC rotor housings usually are down to the steel liner at the outer edges which can't fully be taken out.

but what is this coating that turblown offers? no offense to them but i haven't ever seen a coating work on chrome and people have tried in the past. they offer lots of different coatings but i have never actually seen reviews on any single one of them. without claims they would serve better to explain the purpose of the coatings, show wear patterns and pictures of use. a plasma sprayed new looking part doesn't make it immediately better.

chrome simply doesn't like to bond with other materials after its initial setting, but who knows maybe it does work great but an explanation would be very helpful.

 

Hey does resurfacing rotor housings cause more stress on apex seals??? If your removing material doesnt that allow the apex seal to extend out further from rotor??? Jus curious...

 

13B Rotor Housing Coating - Turblown Engineering

 

i believe that goopy's refinish removes so little material that the seal stickout is not an issue (like a glaze breaker hone on a piston engine), they do stress the side clearance of the apex seal to the rotor grove however

 

it would be more critical in applications where people were using the stock 3 piece seals. since the 3 piece seals are no longer sold and no one should really be reusing them it is not an issue.

 

care to expound?

 

Take a look at the image below. If you remove material, and the seal sticks out more, you could possibly break off the bottom of the 3 piece apex seal due to stress.

The reason he says nobody should be using them is because they really have no benefit over the 2 piece and are weaker than the 2 piece. I originally had 3 piece seals in my engine, and replaced them with modern 2 piece FD seals and called it a day.

Yeah, they seal better between rotor faces, but most of your gas leakage between chambers is when the seals crosses over the leading plug hole.

 

that looks like an exaggerated picture, you cant really have that much gas leakage around a correctly clearanced apex seal/seal groove. (one of the main reasons for a proper warm up before driving?)

i though RR would referring to turblowns coating rather then in reference to the seal stickout question

 

It is exaggerated to better explain how it works. Like i said, 99% of your leakage occurs at the leading plug.

Nope, he was referring to seal "stick out".

 

exactly, thats why i didnt understand what he was on about with a 2 or 3 piece seal.

 

Another poster hit him up with this question...

 

Of course it's exaggerated. Otherwise we'd be looking at an image showing factions of a MM. You'll find that most engineering diagrams designed to show stresses, leakage, deformation, etc. are exaggerated so that we can actually see the thing we're studying.

3 piece seals are an issue because the top piece wears and will eventually roll out of the groove even though the seal is still serviceable. Taking some material off of the housing, causing the seal to stick out more, just exacerbates this problem.

3 piece seals are one of the dumbest ideas Mazda ever came up with. A perfect example of tunnel vision to solve one problem while completely ignoring the other consequences. Kind of like the FD twin turbo system.

 

every 86-2003 engine had 3 piece seals in it from the factory, and that was all that was supplied as a replacement part until about 2004, when Mazda went to a 2 piece seal, as a replacement part.

3 piece seals have been NLA since late 03, so IF you could find some, it came out of someones parts hoard.

interestingly the Japanese vendors actually sell 2 piece seals that have been cut into 3 piece.

better sealing > everything else

 

i don't believe the better sealing explanation.

old tired worn out 3 piece seal engines had as much carbon buildup in the seal channels as the 2 piece seal engines, nor did it address the issue with compression and housing wear.

the 3 piece seal engines have eaten as many rotors and housings as turbo engines improperly tuned and built ever have. we've all heard and seen an n/a engine roll a seal upon startup and running on one rotor, there's only one explanation: worn apex seal tip, which wouldn't have failed with 2 piece seals.

 

gasses still have to be able to get under the seal and push it against the housing.

if anything better sealing probably = more housing wear, which sucks.

 

My unopened 87 turbo had 2pc seals as well as many of the n/a engines I've pulled apart

 

they were rebuilt.

mazda never made a 2 piece seal while the FC or even FD was in production so it's impossible that they were original or you misunderstand what a 3 piece seal is. additionally many of the remans made after the discontinuation after 2004 had 2 piece seals.

 

regardless, that is not the topic of this thread

 

I'm a bit more interested in the Turblown process and what it is. Anyone with some more info?

 

i'm curious about the longevity of their coating also, but i'm highly skeptical for the reasons i gave earlier.

 

Not from the factory it didn't.

 

If it's anything like JHB it'll fail miserably in the short to mid term. And you'll have almost as much money in a set of used/questionable housings as you could get a nice original set for, or a few hundred shy of a new set.

 

JHB?

goopy refinish and turblown coating are the same price

i'm assuming you start with usable housings in the first place and your not looking to buy usable housings then have them refinished/coated

$300 only a few hundred less than new s5 housings? my math and mazdatrix prices (probably a bit cheaper on the mazda race program) ~$670ea. so ~1300 for a pair? ether goopy refinish or turblown coating is only a fraction of this cost.

 

Let me explain further.

I have some goopy (and freelance) resurfaced rotor housings on my shelf and have used them in a few builds.

They are grinding approximately 1/4 to 1/3 the chrome layer off the housing as far as I can tell. This is done in hopes of removing most mild defects visible on the housing. Moderate or significant defects WILL REMAIN after the resurfacing, because this process cannot add material, it can only remove it, yet if the defects extend below the depth they wish to grind to, the defects will remain.

Most defects that would cause a rotor housing to be deemed not reusable as-is, are the same kind of defects that would not be repaired or made significantly better by the resurfacing process. So, to wind up with a nice set of rotor housings AFTER resurfacing, you must send in a pretty decent set of housings first. The resurfacing can turn an "8" housing into a "9.5" but it cannot turn a "5' into an "8" in my opinion, it'll still be a 6 or 7 when it comes back except that now you're $300 plus round trip shipping ($400 or more) further into it.

So if you start off with a pretty nice set of rotor housings that might be worth 3 or 400 on the used market, you can put $400 more into them with resurfacing/shipping, and have a near perfect set. But then again you are 2/3 of the way to a new pair if you do that, and I would still question whether this "resurfacing" is as accurate as mazda's finishing procedure in terms of uniformity and flatness...or put another way, I would still be inclined to trust a nice original set of housings more than a resurfaced set.

Or you can take your average set worth $100-150 and put the $400 into them, and when they come back they'll be marginally better and still not worth $550 in terms of condition. Your money would have been better spent selling what you have now, putting more money on a nicer pair of original housings, or about halfway to a new pair.