Ever seen those crazy Aussie Rotaries? My God!

AClockworkGarage said:

There is nothing you can do to make a rotary sound good,

787B says you're wrong.

There are a couple of turbocharged triple rotaries at Nationals and they sound pretty good. I still think that if there were as much mental energy put into rotaries as there has been put into piston engines, we would see a much better quality rotary.

In reply to The0retical :

I'm assuming you're talking about the groove where the soft coolant seal sits? I've seen a few people fix them with a little welding and grinding... lots of grinding. I've also seen some rotaries "fixed" by liberal application of RTV...

Knurled-
Rotary Engine Specialists in Alberta does ceramic and "Cermet" coatings on rotor housings. There is a guy local to me that had his housings Cermet coated and told me about it: https://www.rotaryengine.com/services/ceramiccoatings.html

I also heard Goopy was experimenting with rechroming, they already do resurfacing.

In reply to TheRX7Project :

Interesting note about the water seals. I'd been lead to believe that the housings were junked if a hole was found or the groove rotted. I'm far from an expert on them though as I'm just starting to dip my toes in the pool playing with the RX-3.

I've been following Rotary Engine Specialists and Goopy on and off to see if they offered up any data on the longevity of their services. I know Goopy at one point was experimenting with re-chroming after they finished the resurfacing process but they kind of went silent on it.

There was someone also experimenting with ductile iron inserts for the rotor housings. I haven't seen anything on that for a while but I haven't been following along real closely.

I do wonder what the process Mazda used to manufactured the housings in the first place was that the aftermarket hasn't come up with a good way to recreate the process. I'm sure there's economies of scale at play with the sand casting and chroming but I would have expected that someone could do it even if it were spendy. Same with manufacturing new rotors. It must be one hell of an economy of scale or seriously specialized machinery  that it's taken this long. I'd be interested to know either way.

In reply to The0retical :

They are usually junk... especially since it's not impossible (yet) to get replacements. Usually the only reason to try and save them is because they are ported or custom in some other way, and the cost of replacing them is greater than the cost of fixing them "well enough".

I've always wondered what would be wrong with stripping all the chrome plating from a housing, resurfacing it with something else, and polishing it. I'd imagine as long as it is a strong, smooth surface (like chrome) it would be a-ok. I suppose that's what they do with the Cermet coating I mentioned above, and it seems to work. They say it costs between $400 and $700, so I suppose if you had some ported housings it would be worth the money to salvage them.

GIRTHQUAKE said:

yupididit said:

Okay a few points:

That burnout at 10:10 was a top 5 burnout I've ever seen. 

I love crazy rotarys in little cars. Those cars were like baby rabbits on cocaine with a hive of bees up their ass.

I absolutely loved how these untamed beast still had beautiful body work knowing they could hop into a wall any second. 

What's the lightest rwd car you can buy here in the states? 

How much power can one extract out of a NA 13B?

 

Don't know about *lightest* car, though it's probably just under a ton for oddball 1980s toyotas and such. The 1980s Starlets were around ~1900 pounds wet, but they were front-wheel only.

As for power? I know you *can* hit 400 or more from a 13B, but at that level you had to hog out your intake ports and you effectively have no idle. You'll also have to remove the oil metering pump in exchange for premix in the tank, but that's more for reliability at that speed.

Early 80's starlet's were rwd, i think they went fwd in the mid to late 80's

Hm, I'm not sure if we got those -super- early ones from the 70s, and even if we did they'd be nothing but rust now.

TheRX7Project said:

In reply to The0retical :

I'm assuming you're talking about the groove where the soft coolant seal sits? I've seen a few people fix them with a little welding and grinding... lots of grinding. I've also seen some rotaries "fixed" by liberal application of RTV...

Knurled-
Rotary Engine Specialists in Alberta does ceramic and "Cermet" coatings on rotor housings. There is a guy local to me that had his housings Cermet coated and told me about it: https://www.rotaryengine.com/services/ceramiccoatings.html

I also heard Goopy was experimenting with rechroming, they already do resurfacing.

The water jackets will eventually pit through the exhaust ports and/or spark plug locations.  When that happens, they are done.

I have heard many bad things about the cermet coated rotor housings.  Namely that the coating doesn't have near enough lubricity compared to the pin-point-porous chrome process.  Seal wear happens shockingly fast.  I saw an FD engine that was rebuilt with those that wore the seals down to triangular cross sections in under 3000 miles.  I'm shocked that it ran at all with wear that bad.

GIRTHQUAKE said:

Hm, I'm not sure if we got those -super- early ones from the 70s, and even if we did they'd be nothing but rust now.

The KP61 is the only Starlet we got in the US and they were RWD. 81-84.

Knurled. said:

The water jackets will eventually pit through the exhaust ports and/or spark plug locations.  When that happens, they are done.

That sounds like something that could be fixed by someone motivated enough with a welder, etc.  Probably not worth it, but possible.  

In reply to Knurled. :

Granted, it has been a while since I talked to the guy with the Cermet housings, but he had them for several years and was not having an issue. He also did some additional work to his, if I remember correctly, he put a skim coat of JB weld on them and smoothed them out, as the Cermet was not completely smooth.

In reply to GIRTHQUAKE :

There was an R100 for sale about 2 hours from me last year, it was a field find and was probably more rust than steel. I still wanted to go get it, but honestly what would I do with it. There was another R100 for sale recently on Facebook, a very clean garage "survivor" car, as well as an R100 drag car I saw at one of the local JDM club's car shows. Additionally there's a pair of RX2's I know about in Chicago...

The0retical said:I do wonder what the process Mazda used to manufactured the housings in the first place was that the aftermarket hasn't come up with a good way to recreate the process. I'm sure there's economies of scale at play with the sand casting and chroming but I would have expected that someone could do it even if it were spendy. Same with manufacturing new rotors. It must be one hell of an economy of scale or seriously specialized machinery  that it's taken this long. I'd be interested to know either way.

The 1973-earlier engines were just cast aluminum that was chromed on the inside.  The MFR rotor housings (the peripheral port rotor housings used by, well, Mazda Factory Racing engines from the early 1980s up through the last of the racing rotaries) are also just cheap castings with chrome slapped on them.  They do not tolerate iron apex seals, and the MFR housings actually have a service life of 24 racing hours, at which point the chrome is probably cracking too heavily near the spark plug holes.  (That area gets very hot...)

1974 and later engines, basically everything with iron apex seals, cast the aluminum around a sawtooth-corrugated piece of steel, and then that steel gets chrome plated.  The chrome lasts much longer, although chrome life went up significantly after Mazda ditched the 3mm seals after 1985.

The chrome isn't chrome like a bumper, they have a process where the chrome is applied, and then (I infer) the polarity of the electroplating process is reversed, which DE-plates it a bit, turning the chrome into more like a porous sponge.  This holds oil a lot better and also cuts friction.  As time went on, they did a bunch of other different things.  I know the FD rotor housings had a flourocarbon applied to them for some reason or another.

Bear also in mind that, with the exception of the ultrarare 13A, all Mazda rotaries are built on the same geometry.  A 2011 RX-8 engine is basically just a 1967 Cosmo engine with a few detail tweaks.   They changed some of the tension bolt locations in 1974, and changed compression seal dimensions and coolant seal locations a few times, but that is it.   And really, they should have moved the tension bolts again with the FD engine because they really screwed the pooch there when they relocated the spark plugs (again) and caused a coolant flow issue in THE hottest part of the engine....

With good 2mm apex seals with good tolerance to the rotor slots and sufficient lubrication, the rotor housings are basically immortal chrome-wise, as long as you can keep the coolant cool so that they don't warp all to hell.

Fig. 1:  Warped all to hell.  The shiny spots are where there is more metal behind the surface, the dark spots are where the metal was expanding and warping and causing blowby.  This also, incidentally, causes beaming stresses on the apex seals, and causes THEM to warp at best, and cause wear issues the rest of the way around.

The main reliability issue I seem to have is the side housings wearing down.

Fig. 2:  Berkeley, CA.   This is not the worst I've had but it's still NFG.

Knurled. said:

The0retical said:

In reply to TheRX7Project :

I'm still trying to figure out if Racing Beat actually manufactures their own aluminum rotor housings or what.  They're not cheap by any means but they exist, which is the important part for when the OE supply eventually dries up.

There's a couple of companies out there that'll rechrome the rotor housings. They're about 1/4 of the price of new housings which is a freaking bargain if true. I was actually looking into them recently.

The real danger is corrosion in the cooling wall seal. There really isn't a fix for that as far as I know, though I wonder if they could be machined and sleeved. I doubt it since I can't be the first person to think of that.

Racing Beat does not make rotor housings, they make side housings.  They are aluminum, run something like $1500-2000 each, and intake ports are optional.

IIRC nobody is rechroming rotor housings.  There are people who smooth out the chrome, but this does not help if you have a 12A with half the chrome gone.  If there ARE people rechroming, then I have a waist high stack ready to be redone.

 

The real problem with the billet junk on the market is that it is oriented for drag racers who want to make power for six or seven seconds.  Not road course or street friendly.  The water jackets in the billet rotor housings and side housings that I have seen were laughable.

It's deeply disappointing that the billet rotaries are not up to the task of road racing and track day applications.  An all-aluminum (Billet Rotary even shows billet eccentric shafts on their web site) turbo 13B would be by far the lightest, most compact source of ~400 hp on the planet, making it the ideal candidate for a dream swap.  Oh, well, think of all the money I'll be saving...

I've heard some pretty bad things about the "re-chromed" housings, at least for RX8s. Apparently it's common that the chrome is ground down, not re-applied and the resulting compression isn't necessarily where it should be.