Previous attempt got trolled to death - rotary racing advantages?
 

Ok, so we know how a v8 can be good in a street car.

But, yet, Ive heard rotaries really shine in RACING. So, I started a thread to try to get some real facts out of it (read: not press releases or empty/useless/stupid facts like hp/liter or that its small or doesnt recriprocate) like expenses on rebuilds, frequency of rebuilds, if its any better at going NA in the 2.x liter class (for a 13b) and 3-4liter class for the 20b, and na vs turbo type stuff.

No, Im not out to troll, but on the other hand, Im not here to listen to ricers spew the same old nonsense as before. Hard facts or credible experience, please.

See, Carl Byck is here enduro racing a heavily modified FC, so I know they can definitely work. And, the first thread I started had a TON of info in it! But, unfortunately, before I could read it it was deleted for whatever reason.

So for those who have facts and reason here, this is your chance to educate me and all the other 'piston heads' out there who are willing to listen. Again, this isn't a troll, Im not calling anyone or anything out, I just want to get the real facts here.

So far, all I as able to get before I had to leave my computer (and came back and found it gone) was that because you dont have to worry about a valvetrain with a rotary, theres no worry of springs wearing out or having to adjust lash or shim anything, and theyre naturally able to rev up to about 8K or a little over stock, and can be modded to go sky high with a diff stationary gear and two part e-shaft.

Anyone have anything productive to add? Im genuinely curious!

Since 1996, I have been vintage road racing an HSR IMSA GTU class RX-7 against mostly Porsche 911 2.9 and 3.0 liter, and the occasional Nissan L-28. I don't know about the Nissan engine costs, but a top notch racing air cooled Porsche flat six costs is very expensive, some approaching $30,000 each. Rebuild for the Porsche is $7000. My 12A PP cost $7000 to purchase in 1997 dollars, and was still running strong after 26 road racing hours on it when I pulled it out. In 2004 I built my 13B PP, wet sump, for less than $6000. If you can do your own work, a PP rotary can be re-sealed with carbon apex seals for less than a grand, counting all new seals and springs. If you want one to last and last many racing hours, my evperience is that they cannot be revved sky high. The 12A will rev a little higher and last longer than the 13B, but the extra torque of the 13B will jump out of the corners faster than the best 12A.

12A 9.4:1 NA PP can burn 87 octane pump fuel, and a 13B 9.7:1 NA PP can burn 92 octane pump fuel. This saves you a fortune over buying race gas. An NA rotary will loose power running 110 octane race gas, the stuff most piston race motors require.

See, this is good info - now this is a thread that can go somewhere. THANK YOU! :beerchug:

I personally think a lot of the problem with adoption of rotaries and perceived credibility of them is one of the reasons theyre so liked by those that are in the know - they are very obscure and a lot of the real nitty gritty is hard to find. It definitely makes it special, but it means a lot of what should be "on the table" during discussion isn't.

BTW, why exactly can you use the lower octane and lower compression (relative to the piston engines) with a rotary? Is it because of the bathtub chamber design and knock resistance?

Also, just out of curiousity - in-class, what ends up being the biggest competetor to the 13bs out there? Honda motors? Duratechs? Quad Fours? Limas?

Furthermore, anyone got input about the classes that allow turbo motors?

In which class? Are you talking about road racing, timetrials or auto-x? drag?

For "racing" the important part is the entire package, not just the engine. Vehicle weight, fwd vs. rwd, suspension design - they all play into the equation. Hopefully whatever sanctioning body has classed the cars appropriately so that they are competitive withing the class.

In SCCA Improved Touring (club road racing) the overdog in the ITS class (where the 13B FC's run) is currently the 3-series BMW. Other than that, FC's do pretty well there.

In ITA where the 12A FB's run, the current lead car is (IIRC) the Honda CRX. There were enough RX-7's running in ITA to where in certain regions (like the SE) they run in their own class, IT7.

E and F Production I am not sure about.

In the Grand Am Cup series, the RX-8's are doing quite well, but are suffering from reliability issues (not directly engine related) that all new platforms tend to go through during their first years at the track.

So, what exactly are you asking?

-b

What Im asking is what are these supposed advantages to rotaries in race cars vs piston engines. I have heard that rebuild costs are lower and they can go longer between rebuilds on average when done in high revving NA type builds, and those rebuild costs are lower if you have the knowledge to do it.

Then, I asked how a turbo rotary would compare to the typical turbo piston engine in racing.

Basically Im trying to dredge around for practical, credible experience and whatever FACTS I could find to back it up.

Regarding your comment about the whole car mattering... thats a given! I understnad that. I was asking specifically about the 'engine' variable from a cost perspective, basically. Speedturn's answer was basically what I was going for, but I redirected it fowards if anyone would have similar knowledge of turbo builds for race cars.

I guess you missed the part that his engine died?


-Ted

I think the point of low rebuild cost for an NA rotory is true. IMO in the real world of racecars there are NO advantages to a rotary, only disadvantages. An engine burns fuel to make power. Piston motors do a better job of that than a rotary. End of discussion. Racecars of course crave power so why disadvantage yourself right from the beginning? Sure you can make a lot of power in a rotary but at that point you're talking highly tuned race motors and a highly tuned piston motor still has the advantage IMO.

I'm a Mazda fan and enjoy my rotory but fact is the rotory doesn't represent some special technology; it's merely a gimmick. Let the hate mail begin! :p:

Why did it die?

DamonB, I would like to point out that rotaries share one significant advantage over piston engines for racing: RELIABILITY.

No valvesprings to constantly have to check and change, especially after an overrev
No valve lash, no valve seats, no guides
No split bearings and therefore no bearings held together merely by bolt tension
No piston skirts to crack
No wrist pin circlips to come loose
No head gaskets, just O-rings
And so on!

Yes it is true that, thermodynamically speaking, rotaries suck. But that is not as important as the fact that it is damned near impossible to kill a N/A rotary!

Bologna. Piston motors are just as reliable; in fact I'd say more reliable when judging on the whole.

In my world people build race motors to win the race, not merely finish it. People don't race to lose. You can have all the finishes you like but the guys on the podium also finished and they happened to kick your butt while doing it ;)

Damned near impossible, eh?

Perhaps you should contact rx7gslse. His 13b rebuild should be done by now. :D

The point is:

Advantages:
a) gasoline price (aka, no race gasfor the NA rotary)
b) relatively inexpensive rebuild process, since it is less likely to punch a rod through the block when it dies.

Disadvantages:
a) Less reliable
b) Less powerful
c) Less fuel efficient

I don't know if I would agree with that. I talked to a local racer who races EProd and a few other divisions; he talked about how much more life they get out of the rotaries per season verses the piston guys.

For a NA racing application, rotaries are very reliable.

"Life" as in what? What parts are failing, in what motors? Springs, valvetrain stuff, the rotating assembly, bearings, what?

My 2 cents:

If a rotary engine is kept in tune and operating under the proper conditions (ie, plenty of fuel and no overheating) it will generally last longer under racing conditions than a piston engine.

This is a very general statement of course. There are too many types of engines and racing to say anything specific.

the rotary has enjoyed a storied career in racing. It has won in every class it has been allowed to run. Recently since the 12a/13b has been out of production for the most part (I know the RX8 is a rotary) the support has died off. Parts have been harder to find and have become even more expensive. I also have had a hard time finding someone to do a good job of rebuilding the 13b. I should have acquired this talent years ago but it sadly is to late. With anything that gets old the good people who service these engine have also gotten quite expensive. For me this has caused a shift to another powerplant. It is not a performance issue but a service and support issue that has caused me to change powerplants.

I dunno Lucy... generally you can get more race hours with a rotary vs. a piston engine of similar tune, and get away with less maintenance. Keeping a high strung piston engine alive is an excercise in remarkably intensive regular maintenance. Rotaries, you change the oil and plugs, maybe do a compression test every now and then, that's all you have to do. (Mainly because it's all you *can* do...)

Winning once and DNFing two times usually gets less points than a 2nd, 3rd, and 4th. :)

I've done a driving school at mid-ohio with my n/a FD rx-7, and have watched over 20 races through the years at mid-ohio raceway as well. I always talk to alot of the rotary racers while I am there, back in the paddocks to see how things are going. I talked once to a guy named Glen Jung, driving a tube frame fiberglass FD in GT1 class. He was up against ONLY large cube v8's 400ci+ and by per the rules, he had to run a 13B p-port. A 13B running against 6.0 liter plus cars? Yeah, my thoughts exactly, he said it was frustrating to run, but he could take any of them in the corners, and get lost in the straights. He wasnt allowed to run a 20B!! Some guys even complained and wanted him to run side port and not p-port 13B!!! WTF!! Its like this for EVERY rotary racer I talk to is "restrictions of all types placed on the rotary, and p-port is a big no no for some reason. If the great piston engine is soooo damn good and reliable, why are the rules so hard on the rotary? Are you piston guys that scared to loose to a POS engine? If the pistons are so great, let the rotary run without 25mm chokes, let them run p-ports, just let them run fair for gods sake!! The rotary is cheaper, and MUCH more reliable than any piston engine I've seen on the track. Oh yeah, during that GT1 race Glen Jung was in, out of the 9 V8 monsters pushing 800hp, only 5 finished as the other four (I talked to them all) had engine failures during a 2 hour, 2 HOUR race!!! Glen beat two of them that were running, putting him in third place finish, with only 350hp. Which brings me to my next point, if a V8 is no heavier or worse than a 13B, why is it that a pure race car vs race car, the rotary race car handles better through the corners??? Food for thought. Moral of the story, people hate and fear the rotary, and dont want to be beat by it, so they slam it with restrictions so they can win. Political as hell.

Straight from the horses mouth...
https://www.rx7club.com/forum/showth...=515309&page=4


-Ted

I imagine when he was referring to life, he means how long the engine can make enough power to be competitive. I doubt there is anything stopping you from using an engine with lower compression if you don't mind being non-competitive.

I've never taken apart a race motor, so I can't directly comment on exactly what kind of wear happens when taking a beating like those cars do...

Show me a 1.3L NA piston engine making 300-310hp that has won 24hr races. Or a 2.6L NA making 650+ doing the same. Porsche's new LMP2 car which is absolutely state-of-art in sportscar racing is seeing around 480 out of 3.4L.

The rotary hasn't always been the most powerful engine in it's racing class but Mazda built the winningest record in IMSA with year upon year of reliable service. The overall win at LeMans was a study in this philosophy. The Silver Arrow Mercedes were quicker no doubt but they broke. The TWR Jags could put down competitive laps but at 6.5L they were very thirsty beasts and they couldn't use their advantage and not run out of their fuel allotment. Tom Walkinshaw openly admitted they were surprisingly outpaced by the Mazda. The rotary happened to be just right that day.

In more grassroots terms the rotary has a decided advantage over it's competition in terms of running costs and build/rebuild costs. I can build a front running SCCA ITS engine from the ground up with all new parts for less than $4000. The engine I won the Cen-Div title and 6 of 12 starts with last year cost much less. The same front running BMW engine will set you back 50-100% more. Hell, Huffaker has an ad in this months Sports Car for Spec Miata engines priced at $7000!!! An ITS rotary can be expected to give 5 years (12 weekends per year) good service. The BMW engine will be pushed to make 2 years and still be healthy.

As was mentioned the NA rotarys don't require high dollar race gas. Which really isn't so high dollar anymore since pump fuel is rapidly catching up in price. The question of why was asked. The rotary by nature doesn't make good use of anything over 10:1 compression ratio. Goes back to that nasty thermal inefficiency that was also mentioned. At that limit pump fuel works just fine. In a highly tuned piston engine running compression ratios of 14-16:1 there is obviously a need for greater knock resistance than 93 octane can provide.

The engine isn't exactly light by todays standards but it does provide for a lower center of gravity than a typical piston engine. That's pretty key in high end motorsports. For reference the 26B is listed at 180kg on Mulsanne's Corner website. The latest AER V8 endurance engine is listed 114kg. I'm assuming that's sans turbos. A Judd V10 goes about 130-140kg.

And FWIW 3-rotor PPs are allowed in GT1. Still not competitive with the 600+hp 310ci V8s but allowed none the less.

13bs are essentially 2.6 liters as 26bs are 5.2, but thats beside the point of the thread - HP/liter is specifically the kind of useless factoid I trying to avoid. No offence.

Rebuild costs and lifetime between rebuilds ARE something Im interested in looking at, however. ITS class is for FCs, right? Im really not too knowledgeable about SCCA clases, what would a RX7 run in that class usually? And what are the guys youre running up against, 3 series?

So anyway, to recap here - they lose compression slower than race-built piston engines and are cheaper to rebuild, and often cheaper to build in the first place, they dont run as high of a compression and thus dont need anything higher than 93 octane, and if something goes wrong you just pop seals, you dont put a rod through a block.

Well, that right there seems to be good reasons to use them in racing - you can spend more money on the chassis and tires that you WOULD have been spending on the motor and fuel!

See, we need more threads like this. FACTS are great :icon_tup:

for my 2 cents worth
One of the best features of most rotory powered cars is the low centre of gravity.
The FD has a very very good weight split and a very low center of gravity, this makes it a good prospect to turn into a race car compaired with most saloon cars.

While this is true, isn't this partly offset by the higher position of the output from the engine which raises the transmission?

It was quoted by the mazda enginners who took apart the 787b's engine after lemans, that it showed little wear, and could have run the race again no problem. Assuming all the other functions of the car were in operable condition. The problem with our tiny engines weighing so much is as you know the cast iron. Now run some Aluminum irons, and some lightweight rotors, you looking at a very light engine. Though I do not know how the aluminum will wear. You can always do some sort of coating, which the did on the r26b's engine

I agree putting a 13B against a 400cid+ v8 is stupid. At equal power levels the v8 would have such a broad powerband and so little strain on it relative to what the rotary is dealing with (you might as well compare a twostroke motorcycle engine to a truck motor) its majorly unfair. THAT right there is a result of overly stringent racing rules and lack of understanding.

Regarding the other statements you made, youre ignoring all the other variables when you make your assertions, thus making them... useless assertions. I'd imagine there would be weight penalties based on your displacement, and It also wouldn't surprise me if the v8 cars had a LA rear. Then again, I wasn't at the race, don't know the rules or the cars, so I dont know any better either. I do know the engine itself doesnt effect handling nearly as much as where its put and the rest of the cars suspension tuning and tires.

Just keep in mind people having draconian rules against what theyre not used to being run in the race class doesn't mean theyre afraid of it... I can't exactly show up to an autocross in a 2.3T RX-7 and whine that Im not going up against T-IIs with similar chassis mods because the rules place me in E-Mod (last I checked...) even though a 2.3T to a 13B is a fair comparison IMHO. I know for a fact most 2.3T guys would kill for a rotaries airflow, considering we need twice the boost to make the same power :P. And we both know there isn't anyone on earth whose terrified of a Lima, no matter how much esslinger shit I bolt on it.

Most likely the issue here is there is a major lack of comprehension and understanding because of how different they are, a lot of propaganda on both parties, and general dickwaving. If more people REALLY understood rotaries and we had more flexible or rational rules and guidelines, it would be a lot better, I agree. But part of reaching that is comparing facts without getting emotional or relying on empty facts.

Im trying to get away from that and move towards objective comparisons and facts. So, does anyone have experience of a turbo rotary in racing vs a turbo piston motor?