Alright at my last race one of the corner works was apparently a rotary head (he did a 10+page report for class on them) according to him the only reasson a 12A's redline is at 7k is because Mazda couldnt find an ignition setup capable of going much higher then that. So if you upgraded the ignition system you could get a 10k redline without damaging the engine any. Any truth to this at all?

 

If I recall correctly, because of the expansion rates of the irons vs the rotors, its impossible for them to seize from heat (unlike piston engines). Also Wankels are not interference type engines, so no issues there, but I thought that around 9k you want to upgrade one of the engine bearings for longevity

I'm sure there is someone here with more knowledge than I

 

There are a number of things that can go horribly wrong past 8k. There are a lot of things in and on the engine that aren't made to spin that fast - the bearings, clutch, water pump, etc. And consider the shearing force on the whole keg. Yes, people have built race motors that rev to or in excess of 10k, but those motors are specially built, balanced, treated, and dowel-pinned and also equipped with special scatter-guards to keep the driver from becoming sushi if the clutch happens to fly apart.

I'm sure the experienced engine builders on here can give you more info on it, that's just the stuff I've read on here over the years. I know, the thought of a 10k+ redline does sound enticing, especially with a bridgeport.

 

as usual with things like this there are bits of truth, but overall the story is totally false.

have you ever tried to take a 12A past 7000rpm? the HP peak is 6000, it'll go to 7k, but its making less power than it did @6.

so no mazda set the redline @7k, because that's 1000rpm higher than where the engine makes peak power. or shoot look at the rx8, its the highest revving engine they have ever sold, and fuel cut is at about 9k

it is true that the ignition system is "loosing power" over about 6500, the coil(s) take a certain amount of time to charge 100%, and over a certain rpm, the time available is less than the time it takes to charge the coils, so as rpm goes up, the amount the coil is charged goes down.

10,000rpm is possible but have a look at the competition prep manual (www.foxed.ca) there is a whole list of parts that they change to have the engine SURVIVE a 9000rpm redline for 600km, and to MAKE POWER there.

basically to rev to 9k, they wanted better balanced rotors, higher oil pressure, with the big oil pump and pan. the apex seals are switched to carbon, the stationary gears are hardened, and the tension bolts get rubber dampers. its actually not that bad. the FD and later engines have all this done stock.

10k oiling the bearings becomes very difficult, dry sump is probably mandatory

 

Uh, no. You can seize bearings in a rotary through overheat & oil starvation even faster than you can a boinger. The rotor and e-shaft have huge thermal mass and relatively poor cooling options - they're cooled by oil much more than by the water jacket.

 

Thats not seizing through thermal expansion, a different scenario, but yes, the bearings will seize quite fast without oil.

 

About what I expected, it may be possible but nowhere near as easily as he thinks and besides with the spec rules I couldnt really do any of the above anyways

As far as going over 7k is concerned... yes on numerous occasions, as far as its past peak power (and thus lowering as you go higher) Im kindve curious about the actuality behind that, do you get more out of shifting at peak power or do you lose more due to the diffrent gear ratio and the corosponding drop in rpms? Basiclly are you really losing anything by taking it over peak power by a couple hundred rpm and postponing the upshift?

 

But then, seizing through thermal expansion is not an over-rev-specific failure mode, is it?

 

I say Bullshit. I have a 10 year old 13-B streetported motor with over 50K miles. My shift light is set at 9500. It still running strong.

 

50k isn't a whole lot of miles but that's pretty damn good. What internals are you running? Have you ever had it dynoed? Does it produce power that high?

 

12-A plates big streetport, GSL-SE rotors, factory seals and such. other mods modded jets on e-shaft, wacky modified ROPR, modded 48 IDA, MSD direct fire, 4puck clutch with 3,000 lbs pressure plate. I never had a problem with detonation or whatever as I run my carb rich and my MOP pumps lots of oil. I dont baby my motors

 

So your motor is a custom build and far from stock. I'd say your oil mods help you a lot at those high RPM's. That's a pretty good build to go for 50k at those revs, props!

 

that depends. in a straight line, like drag racing, there is going to be a certain shift point, for each gear that works best. a STOCK 12A makes peak tq @4k, and peak hp @6k, so your shift point is going to be something that drops the rpm to around 4k. off the top this puts the shift point around 7k with stock gears.

but in road racing one of the great features of the rotary is that if you want to skip the upshift-downshift right before a corner you can, the engine wont care if you rev it to 8k here and there. a couple HD's ago i would have posted my friends BP rx3 video from infineon. he used to rev that thing to 10k, and during the 2-3 laps he never leaves second gear. (maybe its 3rd, long time ago).

 

The stock ignition system is plenty.

The engine internals, however, will not stand 10k for more than a few moments, not that it will actually make power there.

Basically, you talked to a fanboy who has no real-world experience.

 

But you can run them completely out of coolant and they will still keep running, unlike a piston engine that will lock the pistons in the bores. One of the reasons why they're popular for aircraf.

BTDT. I found that if you keep the loud pedal mashed, an all-aluminum engine will self-machine everything and stay running but it will barely idle and won't have any compression once it cools off. I never did find out if the pistons or the bores lost the battle, but it got me to work on time

 

I'd like to see your supporting evidence for that.

I hope you're not citing from this single case anecdotal report, and considering it to be a general case:

http://www.dmack.net/mazda/information.html

Every source I can find (including Atkins) mentions this one supposed case... And no one who mentions it gives any specifics about the actual incident.

The same sources tend to cite the engine as never having physical catastrophic failures, yet there examples of exactly that happening just within this site, usually traced back to fracture of a stationary gear causing rotor desync, or to massive detonation.

 

Hell, I've done it, although I didn't get the engine hot enough to kill it. Not the first time, anyway. Maybe it was the sixth time that did it


Blow all the coolant out, continue driving until there's a safe place to stop and try to fix it. It was always that heater hose under the beehive. Fixing the beehive oil leak fixed the heater hose problem, but until that point I had a splice in the hose partway up and always kept an L in the car. And some water.

The funny thing is, sometimes the temp gauge would peg, sometimes it would drop to full cold like you'd expect it to.

 

So how long of a "keep driving it" time are you talking, here? Couple minutes, tops? Longer?

Done that on old-school iron-block V8's multiple times without apparent serious engine damage, too. Doesn't mean it was good for it, or didn't weaken key components for early failure.

Do it long enough in a rotary (especially with a beehive, I'd imagine, but I'm used to FMOCs) and the inability to keep the oil cool leads to viscosity breakdown and loss of seal and bearing lubrication, and failure to adequately cool the rotor which leads to seal spring failure too.

Failure to cool the hot side of the rotor housings under load leads to bad things, like warping, loss of dimension, even cracking. So sayeth the engineers who designed it.

I've no doubt that you've done as you say, but that doesn't mean it's 'safe' or 'non-damaging;' it just didn't lead directly to failure.

You can run an engine for minutes without oil in it, sometimes, and it won't necessarily seize. Doesn't mean it's not damaged in the process, though.

 

stationary gear failures are kind of rare, i've only seen two with my own eyes. the first was in a Pro7 car where the guy missed a gear, he wanted 4th and got 2nd, or something, engine saw 12K. it actually still ran ok, but it sounded like a piston engine that needed a valve adjustment. so the driver made it back to the pits, then onto the trailer, and then off the trailer. damage? yes, but you'd make it home in a plane

#2 was this one http://fc3spro.com/TECH/HOF/K2RD/k2rdhof01.html
engine was running in 3rd, at 8250rpm on the rev limiter and after about 30 seconds a lap of that for half a season (8 laps a session, 4 sessions a day, 2 days in a weekend), and after all that it let go. this one did not make it back to the pits. this wouldn't happen in a plane, as you can't rev the prop that fast!

ive never run a rotary too hot for too long, but we have run a couple of BMW E30's without coolant, one at the race track, and not only do they not blow head gaskets it seems to actually make them run better. the rest of the car is pretty tepid, but they are durable

 

Racing Beat is revving ported Renesis engines to 9500 rpm http://www.racingbeat.com/mazda/perf...ml?id=Fu6gPibm . I'm sure the Renesis could hit 10k, especially the 09+ with the better oiling system, but there has to be a reason to do so.

 

I USED to run my 4 port 13b to 10k everyonce in a while.........USED to, get the picture. lol it shattered the e shaft..man that blowwed up real good. this was when parts were easy to came by in the 80's. not worth it now days. just my .02 worth

 

And our nominee for Understatement Of the Decade:

It's always good when you blow the engine so hard you break the intake manifold.

 

Those engines are also not 20-30 years old. Even if decades-used parts inspect OK, stress over time takes it's toll.

Big difference between new-built and re-built.

 

whoa! just like FnF!

it doesn't really work for road racing though, i live my life one session at a time, for those 15 minutes i'm free?