WonkoTheSane

iTrader: (2)

I just got my engine disassembled, and it's as bad as I feared... The rear rotors' apex seals completely took out the rear housing as well as the rear plate (intermediate plate seems okay, oddly enough).

So I'm going to be looking at a set of replacement rotors at least, obviously a housing and most likely the rear plate (more on that in a second)....

My goals for the car is to be a quickly higher revving engine for road racing and autocross.. I'm gunning for about 350HP or so with a BNR and supporting goodies. I'm going to be running the ignition and fuel management with a megasquirt 'n spark.

I would really like to go with the lightest weight rotors available (Renesis) which coincidentally also have the highest compression ratio available (10.0:1). I'm thinking of pairing this with a Renesis e-shaft as well (lighter weight) and stat gears for strength. The entire rotating assembly will be balanced once I get it assembled.

On the housings/end plate sides, I've worked before with a company called Millenium Technologies, ( http://mt-llc.com ), that does Nikasel plating, and they're going to plate my endplates and housings for me.. When I pair this with the Rotary Aviations' stronger seals, I think that I should be able to run decent boost with high compression, fairly safely..

I will also be porting the intake and exhaust ports with the help of some rather well known cylinder head porter friends.

Can anyone punch any major holes in my plans? I'm just trying to think of everything ahead of time so I can get everything started...

Thanks for reading and any suggestions.

arghx

iTrader: (3)

Do yourself a favor and go with a proven setup, and spend those extra dollars on parts that will make the biggest difference. Get some good condition used 8.5:1 rotors because they are inexpensive, and keep the s4 T2 eshaft. Then get a brand new rotor housing and rear iron, or a good condition JDM one. Aftermarket treatment of housings is just nowhere near as good as OEM. Read this article--it's not an SAE paper or anything, but it does raise some good points: http://jhbperformance.com/downloads/jhb-tech01oem.pdf

Since you are trying to optimize the benefit-per-dollar, you will get far more additional benefit from good condition, oem parts than from very high compression rotors that will increase the risk of a blown motor. And you won't have to deal with the balancing and all that other crap.

You are going to get in way over your head trying to tune an ultra high compression turbo setup on a Megasquirt. Hardly any professional tuner will touch Megasquirt (Steve Kan won't, I asked him at one point). I had one, I know. I would never, ever trust any no-name local guy with a high compression turbo setup either. For the most part you are on your own man, and it would be hard enough with a Haltech or Power FC (two most common rotary EMS's) but you are picking an EMS which has a smaller pool of available basemaps and overall knowledge.

I'm not saying you can't pull this off, but the odds are against you doing it without blowing up another motor first during the learning process. You will need very very carefully tuned timing maps and EGT datalogging. Do you realize how hot EGT's get with hard running even on 8.5:1 rotors? You will guaranteed need a methanol injection system too. And you better not run out of methanol/water during an event or you could be in big trouble.

If you want really good response, you will find much more benefit from a good manifold and turbo combination. Consider a T3 GT35R kit from Aspec tuning with a tubular manifold. It will have a more efficient compressor wheel (compared to the T04B H-trim of the BNR stage 2 or the T04B 60-1 of the stage 3/4) with a divided hotside and an external wastegate for better boost control. There's nothing wrong with BNR turbos but clearly you have some money to burn if you are thinking about crap like Rx-8 rotors. So why not get a high end setup with a higher power potential as well? Assuming you have good quality housings, you would benefit the most from a really efficient turbo setup.

For your goals, you need to go with what is known to work: safe, low compression rotors on good housings with a well-designed manifold and turbo system.

beefhole

iTrader: (29)

I say go for the Nikasil. Don't think I've heard anyone trying this on rotary engine parts. How much though would it cost you?

classicauto

iTrader: (3)

don't use RX-8 rotors.

static compression and dynamic compression are two different animals.

arghx

iTrader: (3)

experiments with unproven internal engine parts (like Nikasil plating and turbo setups with super high compression rotors) are for shops and experienced people with deep pockets. it's the whole "before you learn to run, you have to learn to walk" type of deal.

j9fd3s

iTrader: (3)

+1 just build the best stock (or street ported) engine you can. the japanese dont do much other than that, and they make plenty of reliable hp.

WonkoTheSane

iTrader: (2)

I suppose I should explain my logic for thinking of Nikasil plating them; I've worked with Brian over at Millennium a lot with work, so he's willing to plate these for me for.. er... "rather cheap" (no public record, please). I work at a CNC shop, teaching 5 axis machining (to automotive customers), so I was going to fly-cut the work faces of the intermediate and end plates down to have them replated by Millennium, and he said that he as a canadian customer who has a jig set up to do the rotor housings, located in Manitoba, Canada.. I think it's JHB, but I haven't gotten the contact info from Millenium yet...

I really think a light weight high compression engine would be fun to play with, especially since I already had a megasquirt running my last Rx7, which I tuned myself, and I race with a guy who owns a dyno shop who said he'd help me tune on the dyno if I ever want to, I just never got around to it last go around.

I just figured since I had to buy at minimum a rotor and housing that I'd see what everyone said about a fast revving light weight drivetrain.

Arghx - That was a great link to read, and if J.H.B. reads this, thanks for posting it! That was also an excellently thought out response, I really appreciate your input on it. I'm going to look into the cost of the turbo/manifold combos you mentioned, though I'm all about building/porting/plating everything myself, since I have a lot of CNC equipment available and a huge resource pool of customers who will help me out with a killer build/port... Money is definitely an object, but not as big as it would be this time next year or so (when kids get involved)... So I'll be taking a lot of what you said into consideration to make a fun, fast revving reliable engine..

Keep the comments coming guys, I'm loving all of 'em.

Thanks again!

WonkoTheSane

iTrader: (2)

Oh, and I should add that Brian at Millennium said that they do a decent bit of plating on rotor housings and intermediate/end plates for race teams around the world already... . Most of what they do is 2-stroke style engines, so really, a rotary isn't that different

arghx

iTrader: (3)

Let's run some numbers here, not to make an actual budget but to illustrate the fundamental nature of your choice--pride in a unique setup vs the piece-of-mind of proven parts.

Take the cost of a brand new s5 rear iron. I say s5 because they are a nice upgrade with 19% thicker dowel land casting according to my own measurements (see this thread: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/just-measured-s5-turbo-rear-iron-factory-bracing-pics-795339/ ). -- $400. Now let's take the cost of what you were probably intending to get, a decent condition used s4 rear iron (good luck finding a nice used s5 iron). That's $100. Plus say $50 for the plating.

So say you've spent $150 total for the housing, whatever the final prices (plus shipping) of the housing and the plating may actually be. Then let's say two Rx-8 rotors are $200. Then you've got at least $50 for balancing and any other crap you need to make it work, but probably more than that. That's $400.

Now, decide which is the best choice for the money. On the one hand you have the used and unproven plated housing. That's unproven relative to a new rear iron with millions of dollars in development behind it and an unquestioned reputation. You also have the high compression rotors. This setup is 100% guaranteed to increase the risk (note I said risk) of a blown motor, while many would say it offers a dubious increase in response compared to more proven options such as a highly efficient turbo/manifold combo.

On the other hand you have a brand new rear iron with the piece of mind that brings. It's never been overheated. It has no wear, and it has all the hardening that Mazda intended for it. Since it's an s5, the casting is thicker, and your odds of cracking the plate during a tuning mistake are lower than a plated s4 iron with thinner casting.

So let me ask you--which is more important given your budget and your preferences, reducing the risk of a short-lived or catastrophically blown motor, or having a setup that is different (although not guaranteed to be superior overall) from almost everybody else's? I may not have described the exact choices of parts you were considering, but as I said I am illustrating the nature of your dilemma my friend. There is something to be said for both types of setups. Only you can decide what's right for you.

WonkoTheSane

iTrader: (2)

Arghx - Man, I wish I was somewhere near where you lived, because you seem exactly like the kind of person I would like to hang out with and grab a beer You are making the same exact argument that I would make to someone else, haha!

The main reason I'm considering going with this setup, although it's radical and not really done before (at least to my knowledge, and I'm researching as much as I can), is that I'm getting the plating done for basically the cost of shipping, I'll I will have to pay for is the honing to be done on the rotor housing to remove the coating (there's already a few companies that have the jig to hone it, or I would do that myself)...

I have a local customer/friend who is REALLY known for doing cylinder head porting and rotating assemblies, so I'm not worried about doing balancing/porting myself, since he's going to let me use his flowbench and grinding equipment and let me apprentice for a day.. I may do my porting via CNC, though since I teach it and all I'd have to do is make the fixture plate...

I have the equipment available to do the fly cutting to remove the factory nitriding from the intermediate and end plates.

Using your numbers, where I'm at then: If I can reuse my rear plate (after re-coating, obviously can't without re-coating), approx $0.

That leaves about $200 for the Rx8 rotors or $100ish for used TII or NA rotors... Balancing can be performed at my friends/customers' shop for *cough*nothing*cough*...

If I wasn't in my unique position, I really wouldn't be considering all of this crap, but, I don't know that I will ever be in a position like this again where I could try a radical/experimental setup like this...

I guess the real question I'm asking is: If you had the chance to try a setup like this for within a coupl'o hundred bucks of a regular rebuild for 3rd car that is pretty much just a race car.... Would you try it?

Also: I'm checking out the link from the last post, VERY good to know.. Do you happen to know if anyone has welded that area up and re-machined the dowel location after beefing the heck out of that area? I'm thinking it would be pretty easy to reinforce that area before I fly cut the rear iron... I guess the iron is already scrapped unless I go the plating route, so what's to lose, right? I can easily machine a new dowel hole into it after welding, because I'm sure it would distort...

Spectator

iTrader: (1)

I'm just asking and I haven't read the thread but, why dont you go with a good proven/reliable set-up, spend money on new housings and S5 rotors/ used shaft put an 8lbs flywheel on it, it'll rev like a charm just like you want. No balancing, nothing and more money for something else. Tada! No?

Spec.

WonkoTheSane

iTrader: (2)

Spec - That's what Arghx is trying to talk me into as well... And I will probably be going that way since it really does seem to be the most logical way of going....

Spectator

iTrader: (1)

Yea, I showed him everything he knows, I just dont post as much as he does. And I just read the thread and he didn't mention the part about the flywheel. Half-*** replies.




But seriously now, thats most likely what my next build will be with the TII I have waiting. Leaves more money for better upgrades.

Spec.

arghx

iTrader: (3)

I think you will regret the high compression rotors long before you regret the Nikasil plating, especially if you are tuning this yourself. As far as the rear iron issue... I have personally detonated the crap out of s4 irons and never cracked one (blew a MAP sensor line off at 21psi), but many others have had problems. You could attempt to brace them, but I have learned the hard way that 90% of the time there is no substitute for OEM manufacturing and design quality (like s5 or s6 irons).

Go with the 8.5:1 or even 9:1 rotors. There are lots of timing maps available for those rotors with all sorts of porting configurations, especially for Haltech's and Power FC's (which you could make work on the Megasquirt maps). Take it from me man, I had no trustworthy local tuners and I had to learn how to tune standalones myself. You need all the safety cushion you can get. I'm hardly a professional, but I have tuned an FD on sequential twins at 14psi and a single turbo FC at 21psi with race fuel, both street ported.

WonkoTheSane

iTrader: (2)

Okay, so what I'm really hearing here is to just avoid the higher compression rotors, but still go for the light weight (Renesis E-shaft, and I'm planning doing the triangular lightening machining on the rotors)... I really feel like I'll be missing a big opportunity if I don't use the machinery and experience available to me.. But it definitely makes sense to avoid the higher compression since I'll be tuning it myself..

Spec - I suppose I should have called out the flywheel, that was kind of a given for me

Thanks guys!

WonkoTheSane

iTrader: (2)

Well, not only were you guys talking me into being sensible, 88RxN/A posted up a engine for a price I can't pass up... so the rebuild will be put off indefinitely anyway... I really wanted to see how the Nikasel held up, though, but I can't pass a deal like this!

Groshuk

I think you are crazy not to try this, like you say it costs you very little and it's not a daily driver so if it does blow it's not that big a deal. If Mazda had listened to guys like this back in the day the rotary never would have gotten this far, we'd all be driving around with steam engines still because it's tried and true technology.

No matter what happens you tried something cool utilizing your skills and connections that very few other people would ever be able to do. Even if there's only a 10% chance of it working I'd do it just for the chance at proving the doomsayers wrong.

Spectator

iTrader: (1)

Seems you have 15k$ to waste that we dont. The rotary engine got to where it is now because companies put millions of dollars in research in it, not because of unique owners like us.

Spec.

farberio

iTrader: (7)

This is comforting except for the fact that the bob weights used to balance a rotary are no where close to the bob weights used to balance a piston engine. And don't even think about asking other shops how their bob weights look because thats a very closely guarded secret.

If you have money to burn, why not pick up a set of RB lightened rotors? Or get some S4 Rotors and lighten them on your CNC? That way you get lower compression and lighter rotors.

Groshuk

Where do you get 15k from? From reading Wonko's posts he's spending well under a grand and reworking junk parts.

classicauto

iTrader: (3)

My suggestion to avoid them is borne more from a "they don't work well in older style engines" then from a tuning perspective.

They may be 10:1 sitting on a bench, or by volume measurements but when they're actually running in an older style keg, they simply do not seal as well as the older style rotors. You'll end up with a compression ratio somewhere in between, or possibly lower than, an older set of rotors. There's alot of variables for this with the machining being a huge one, but a much better option if you're after fresh slots would be going 3mm on an old set of rotors.

The lightening and balancing though, sure, knock your socks off.

WonkoTheSane

iTrader: (2)

That's the info I was digging up after searching around some more, why couldn't you post that originally (about the sealing aspect)...

As I posted earlier, I found a local deal too good to pass up, so what I'm thinking is later on I will get this all done to this engine, but using the lower compression rotors because hey, they're cheaper, and it gives me a little more wiggle room tuning wise. I will still do the machining and nikasil, why not? I'm also going to go for a lightened rotating assembly, including machining out the rotors a bit for lighter weight. This should be a spare engine, and I probably won't get around to it until next year now....

Thanks for all the info and discussion about it.