Nexxussian

Okay, I'm a rotary noob, no two ways about it.

I race at Bonneville, the sanctioning body lowered the displacement multiplier on the rotaries from 3:1 to 2:1 just last year.

It doesn't look like they are going to push it back up any time soon.

I run in a class with a 2015cc displacement limit (so 2015/2=1007.5 cc, call it 1007) so the 10A is the only Mazda rotary that I'm aware of that is small enough.

No, a 12A isn't close enough.

I've read on this forum about possibly cutting down a set of 12A rotor housings and using the later 13B mid and end housings that have the water seal grooves in the end and mid housings.

So the question is, with a max effort build (billet rotors and whatever else needs be) how much power could one expect from a combination like that, 5 miles at a time?

For those that respond with #s, what would you expect it would need (peripheral port, 6 port, billet rotors, etc).

For frame of reference, 350 HP at the flywheel is the number I'm trying to beat.

If feasable I would like to run a variable ratio trans (snow machine? something else? suggestions welcome ).

I know this may not be in the correct forum, but since the 10A is deciedely a vintage combination I thought I would start there first, as it didn't make sense to me to worry about the trans, if the engine wasn't up to it.

Thanks in advance to everyone that doesn't heckle or suggest lunacy on my part.

re10

210bhp has been done before... PP, injection or 48ida, the right exhaust, etc. No torque to speak of, so pushing hard at full noise, it just won't rev out in top gear no matter how long the track is. You will not get 350 at the flywheel.

Nexxussian

Re10, thank you, that is what I was afraid of.

Every indication is the current record holder has that much.

We have less frontal area, but he has a better Cd (working on that) so we can't give up any power.

Guess I'll have to dig into that piston poundin' Peugeot I'm running (XU10 w/ a XU9J4 top end for anyone that's interested).

DriveFast7

iTrader: (1)

350hp out of a 2 liter? That's a money class.

Nexxussian

It's certainly turning to one.

Hence my interest in the rotary, as power is primarily a function of shifting enough air (yes there's more to it, but more airflow allows a higher potential for power).

I know that a rotary doesn't have the best reputation for combustion efficiency, but you can wind the daylights out of them.

So my only two concerns were durability (seems better at high rev with a 10A anyway) and getting the air to move through fast enough without boost.

I figure RE10 has the most practical experience with that size, modded for maximum noise, of anyone that posts here regularly.

Of course if anyone here knows different, I would love to hear it.

RCCAZ 1

iTrader: (10)

Would love to hear the BS excuse for this rules change. Yet another group trying to handicap the rotary. Sad and misinformed...

Nexxussian

They got closer to what the rest of the world uses for a multiplier, not there yet, but I'm sure Racing Beat has something to do with the progress so far.

j9fd3s

iTrader: (3)

not many of use have ever seen a 10A.... where are you going to find rotors?

re10

You can find anything if you look hard enough, and have the right amount of coin..! Even 10a rotors.

Nexxussian

I've seen several sets go for not completely unreasonable amounts of money on the various auction sites.

However I would expect billet rotors would almost be a necessity for what I had in mind.

The only things I would likely use that were actually from a 10A would be the E shaft and counterweights.

Even those would likely have to be modified.

gerald m

Nice to see you have surfaced with your ideas Erik ?? hope something works out for you.

Jobro

iTrader: (2)

225BHP from a 10A would require 115% filling efficiency at 8500rpm with a BSFC of .55.

I can't see how you are going to get another 50% on top of that especially considering you will need to hold that RPM and power for what 10kms?

Nexxussian

Jobro, I was expecting to have to wind it tighter than 8500 (10K +), hence part of my question, with peripheral ports, and likely the side ports too (if I'm reading the forum right, they call that "6 port") that should help.

Of course then you have to get it to exhale.

Not quite 10 Km, the long course is 5 miles to accellerate, so if my math isn't horribly off this early in the morning that's just over 8 Km.

At this point I'm running the short course though, so at 3 miles that's just under 5 Km.

I get what you mean though, it's not a drag race, same issue the recips have; alot of things you can get away with for a 1/4 mile don't survive the "great white dyno".


Gerald, yes it's nice to do this with more than PM's.

I figure anyone I might surprise with a rotary by this point would be suspecting something by now anyway.


Saddest thing being, if RE10 doesn't think it's feasable with a 10A, it probably isn't.

RotaryEvolution

iTrader: (30)

350 from a 10A won't happen, no matter how you slice it. you would have border into uncharted territory with compression ratios on the rotors in order to even come close and that will get costly rather quickly with all the customized parts required. we're talking 11:1 rotors, race fuel, semi PP with large peripherals and some serious timing. if there was ever a chance at actually blowing out an apex seal on a naturally aspirated rotary engine, this would be the ideal circumstance.

a semi peripheral port is what you're referring to as a 6 port, 4 ports in the irons and 2 smaller peripheral ports directly through the rotor housings. a true peripheral port is only 4 ports, 2 in the rotor housings and the 2 exhaust ports, the side port cavities in the irons are filled but this is generally more widespread in forced induction as i believe semi-PP has better low end and mid range response.

GtoRx7.

iTrader: (12)

I think a "pull all the stops" n/a 10a could push 300+ flywheel horsepower. Due to the massively narrower rotors, the main bearings are much closer together. So even without a center bearing, rpm could be 11k with just stock components and drysump (obviously balanced, hardened gears, etc etc etc). Here is some examples of what I know has been done, and my own experience that points to 300hp 10a being possible-

-In Australia there is a 11.5k rpm 13b n/a making 425 flywheel hp. 425/ 1.3 liter = 326

326 x 1.0 liter obviously is 326hp crank hp on a 10a

-A very well built 13b sized rotary n/a will produce 100ft-lbs per rotor. 200ft-lbs for a 13b. Which is 153 ft-lbs for 10a. 153 ft-lbs @ 10,000 rpm is 292hp. 153ft-lbs @ 10,500 is 305hp.

-Let say the 10a size being so narrow cannot match 13b efficiency. So do 140ft-lbs instead. 140ft-lbs @10,500 is 280hp. Still close.

So build a 10a using 12a housings cut down, 13b side plates from FD, street port with semi p-port, ceramic seals, drysump. I think it can be done.

Jobro

iTrader: (2)

Narrow engine /smaller will give you more efficiency!.

You would however be fighting against 60s tech apex seals/slots etc using 10A rotors. I've heard you can cut 12A rotors down a fair bit from 573cc.

It may be possible to get 84-85 12A non turbo rotors, get them cut down so each chamber swept ~503.75cc. Within reason the 12A crank might still work because you can pack the stationary gear further out etc.

Even working on 115%VE 2015cc .55bsfc and 10500rpm you are talking about 282bhp. It might be pretty hard to get 115% VE @ 10500rpm. Seals might also stop working and make the BSFC drop too.

What is interesting tho is that 1psi of 'ram flow' would be worth about 20bhp. If you could get 1-3psi of positive pressure using outside air then you could potentially get your goal. The other thing I'm not sure about is if it is possible to get a vacuum effect on your exhaust due to air speed outside the car.

The other thing you could do is fuel the thing on some sort of alcohol fuel and inject at the entry to the ram tube so the air is precooled

re10

Good luck with that - 200 is hard enough ;-)

RotaryEvolution

iTrader: (30)

cutting the rotor width also requires extensive reworking to them on top of that, as there no longer is side seal, corner seal and oil seal grooves. you may as well make your own cast and build higher compression rotors at that point.

GtoRx7.

iTrader: (12)

Well, I have seen conflicting info on if a narrow rotor is more or less efficient. But everyone can agree that the area to put a exhaust port and intake port on a very narrow rotor housing is not very large :/

I've always wondered how performance is if you were to use only one side seal, instead of the twin side seals on the early engines? Work similar to the newer rotors? On a side note my dad has some experimental 10a rotors that are both higher compression and use single side seals. Wonder how much those would be worth?!

Apex seals could be a easy fix, press in a machined groove that is 2mm, and pin it. Then use 2mm ceramics, have NRS make a special "10a" length.

Jeff20B

iTrader: (13)

Single side seals are ok to run. Just make sure they're .002" to .003". Plenty of sealing, half the drag.

re10

I have single side seals on mine, the last of the 10a rotors for the RX3 were all single side seal.

RCCAZ 1

iTrader: (10)

Dyno charts from recently rebuilt 10a by Racing Beat. Bone stock...

Nexxussian

Thank you all, I was suspecting billet rotors might be a requirement, sounds like that's the case (from a time standpoint if nothing else).

For a cost standpoint, and I do appreciate the concern for my wallet (thank you) the engine we have now will likely require a set of aluminum rods (custom billet), custom pistons (billet) new valvetrain (all 16 valves, new springs, retainers, keepers and from what I can tell I have to install solid tappets, from a Kawasaki, yes it requires machine work, then there's the cams) as well as a dry sump with either a bottom end girdle, or a full bed plate (not sure we have the machining resources for the bed plate).

None of that is cheap, and we still have to come up with a different trans anyway, as the gears have WAY too large a RPM drop between them in what we have (and no way to get them close enough).

Still an academic exercise on this end as I don't know that we will get any of this done for 2012.

Jobro, the hardest thing about ram air at Bonneville is to get it to distribute evenly.

Admittedly it would be easier on a rotary (only 2 combustion spaces to feed, instead of 4) as the plumbing would be simplified.

Vacuum at the exhaust would be possible as I would want to run the pipe out the back of the car (double wall and insulated too, I don't want to catch anything on fire, outside the engine anyway ).

tlmitf

What fuel are you running?
Is it free, or do you have an oxygen limit?

Rotaries run really well on hydrogen (or at least mazda has found that the rotary runs on it far better than any piston motor )

Running massive RPM isnt an issue. There is a proven series of steps to keep them together at high rpm.
One of the issues is the stat gear tooth profile, at high RPM the tooth profile lets the rotor dance on the gear (creating issues in itself) and also soaks up HP.
If you going for custom rotors, you may be able to invest in some updated stat gear tooth profiles to unlock a couple of HP, and hopefully help keep the rotors off the side plates.


Due to the width of the 10A, your going to have exhaust port issues - trying to get all that hp out the port without melting things.
You can only go so wide before the apex seal bows out the port, then SNAP.


Sounds like your not going to have issues with your inlet V's outlet mani pressures, which is most of the battle

Nexxussian

We are currently running the "gasoline" class.

That means we have to purchase our fuel at the track, from the official vendor.

That may seem draconian, but it's the only practical way they can police what constitutes gasoline.

The other option is the "fuel" class, which constitutes "everything else" (ok if I remember correctly they do have a ban on radioactive isotopes, and they may yet ban Hydrazine, no, that's not a joke).

I expect a rotary could be made to run quite well on Methanol, or Nitro, I have to believe someone has at least tried.

I seem to recall a formula car series running Mazda Rotaries on alky, haven't heard of anyone trying nitro though.

That's a whole different project for now though, Gasoline is a difficult enough task, without tinkering with hypergolics and monopropellants.