I'm looking into turning a '88 GTU into a driver's challenge car with Penn State's car club. So basically anyone in the club will be able to race it. Most of the racing will just be autocrossing, but some people might take it out for track days. In order to get the car in working order I'll need to rebuild the engine. My question is, off of a fresh rebuild, how long will the engine last?

 

when the 787B rotary that won lemans was taken apart, engineers stated that it was in such good condition it could run the race again

 

....

a better reply would be more beneficial.

Perhaps from people who actually race rotaries...

 

ive heard roughly between 30k and 40k depending on how hard the engine is run.

 

The short answer: It Depends.

The long answer: It depends on how it's taken care of, how it's driven.

Major factors in rotary engine longevity:

*Apex seal lubrication. The best option is premix in the gas, roughly 100:1 ratio (though for race use, I'd go 80:1 or so). The next best option is to use the stock injector pump with an adapter to let you use an external two-stroke tank. The not-great-but-works option is the stock system (injecting crankcase oil). The worst is no lubrication at all.

If the people driving it will understand the importance of putting premix in with gas, I'd say go that way.



Another really, really important factor is temperature. Overheating a rotary, or running it hard when cold (heating it up too fast) will kill it in a hurry (usually just the coolant seals, but it can warp stuff if it's bad enough). Make sure it stays cool, and make sure people warm it up FULLY before getting on it hard - this includes the oil temperature, which lags behind coolant temperature by a few minutes when warming up. You also need to keep the oil cool - hot oil on a track can fry the bearings in short order if it gets too hot to lubricate. The oil cooler matters, and I don't *think* you'd need a second one for a NA, but... keep tabs on the oil temperature on track days.

Porting: I wouldn't suggest any insane port jobs for a "club car" like this, but you might want to consider at least cleaning up the intake ports while it's apart.

Clearances: They matter. There are some good threads over at nopistons on side seal clearances & such - I believe for NAs, some people recommend trimming the side seals to zero clearance, because they will make a bit as they push back into the corner seals.

Cats. Don't leave them in. They overheat, fall apart, block the exhaust, run heat back up into the engine that should be leaving, and damage things. Just run without cats.

*ponders*

Another thing to think about is fuel management. The NA ECU runs really, really rich at high RPM - I've heard rumors of it hitting the 9:1 area. This is way too rich for power/economy. A SAFC-II or such leaning it out up high (with a wideband for tuning) will help a lot, and can get you 10-15hp over stock. A better option would be a full standalone ECU.

If it's taken care of, it should last quite a while. It's just that "taking care of" part that's the trick.

-=Russ=-

-=Russ=-

 

The engine can last long. All of my rex's lasted up to about 90-160K miles. I put at least a good 30k- 50K on each rex I've owned (about 3 of them.) With that said, I drive really hard and loved to street race them. My first 2 rx7s I bought in high school and drove everyday. Both were 2nd gens. I street raced them just about everyday on the way home from school, yet I was never hesitant in driving to Orlando or Jax. I have a year long disney pass so I go there habitually. Wasnt even afraid of racing them on the way to Disney. My current Rex has about 92k on it. The motor is still good and the tranny is good. Still has pretty good compression and it held up when I was going to UF (and I made alot of road trips down and back to Ft. Laud.) With that said: Alot of people like to say that rotaries arent reliable, but I beg to differ. I feel that they are very reliable when they are taken care of. If you read alot of the horror stories, you'll see that alot of the times when the motors prematurely go, it was due to fault of the owner (like my friend's Supra... He upgraded the exhaust and that increased the boost. I told him not to drive it again until he could get proper tuning. He didnt listen and blew his motor the same night. Does that make MKIV Supra unreliable, or was my friend the fault?) With that said, I will leave it up to you.

 

O'rly. My guess is that it might have been propoganda from Mazda, that thing was smoking nasty in the final hours of the race.

 

The life depends on the quality of the rebuild. An engine put back together with out of spec, worn out housings, and worn out oil rings and springs will not last as long as one with fresh new rotor housings and flat smooth side housings and ALL new seals and springs.
Some ITS racers can get a 24 hour race plus several other shorter races off a good rebuilt motor.

 

yep give or take thats about right. 30-40hours? on the track.

 

we talked to koby himself in 01 or 02, and the apex seal wear was .00004 or somesuch, basically its not worn enough to measure, he didnt mention the oil seals though....

 

Multiple users? Rev limiter will be your best friend. Don't tell anyone where its at either

 

full race motor professionally built and raced hard but not abused will last about 40 to 50 hours before performance starts to drop off. Engine could be raced for 100 hours, but it would be way down on power and may have to be push started. I have found most N/A race motors have to be rev'ed to 8-10K to take advantage of the porting and this just does not last. Properly built and tuned turbo motor may last a bit longer since it won't need the big rev's. High rpm's just wear things out quickly and a bad rebuilt might not make a 3 hour enduro. Four races last year and four rebuilds. only one made it through a 3 hour enduro without lose of power.

 

Two words: Le Mans...

 

I ran a moderate street ported 12A (we called the engine old reliable) for five years of club racing, this included a two hour enduro race for three of those five years. I sold the car three years ago and the fellow who bought it ran it for about another year and a half before a rock through the radiator overheated the motor and destroyed it. The engine was almost always shifted at 8000 rpm, sometimes higher, rarely lower. The usual race weekend was two 15 minute practices, 2 20 minute qualifying sessions, thee 20 minute sprint races and a two hour enduro. So about four hard hours per race weekend. The engine probably ran 40 or more weekends, so about 160 hours.
I've seen race ebgines last a few hours as well, usually they put new rotor bearings in and run it hard too early. The bearings usually seize up. I blew one up myself, I ran too much timing with carbon apex seals. All good, then poof, a black cloud out the exhaust and the "bad" rotary sound.

My advice:
If you port it, keep it mild.
Make sure you have a good cooling system.
Stay a little conservative with the timing.
Change oil often.
I like the rev limiter idea as well.

-Trent

 

http://www.fc3spro.com/TECH/HOF/K2RD/k2rdhof01.html

we're blaming this one on the rev limiter, 8250 rpm@90 mph is a lot of kinetic energy....

 

Anyone who thinks it's legit to compare a 13B built from over the counter parts to a factory backed, race prepared 4 rotor specially built by factory technicians to install in a prototype car and compete in one of the most preminent races in the world needs medication.

 

I ran my s5 N/A all the time at auto X's and open track events, never had a problem.

I think if you keep the engine pretty much stock, it should last for a heck of a long time. If you have the engine apart, i would try to remove those defusers in the exhuast ports somehow.

I never pre-mixed, and i ran 87 octane. Though, I did run Marvel Mystery Oil, which is a mild detergent, in with the gas.

Engine ran great when i took it out at around 65,000miles. still got it if you want it!

 

thanks Damon for keeping everyone on the same page. I hate to break it to everyone but stock, mild porting and shifting under 8000rpm is not a race built N/A 13B. To make competitive power it has to be wild porting and shift points around 10,000 rpm(mine was like 9200). These engines just don't last like an IT 12a in a pro7. Factory developed and hand built from one off custom parts is not the same as what is commonly raced in the amatuer ranks.

 

The general rule of thumb in SCCA for a "race" ported 12a n/a is 2 racing seasons. I don't know how many hours that equates to but I figure 8-12 race weekends. Shift points 8600-10000. The fast guys "freshen" the motor up before the Runoffs. Those same guys are using ceramic seals, lightened and balanced rotating assembleys with all the other oiling parts and mods. The 13b has a larger rotors and a heavier rotating assembley and will require either lower revs or more frequent rebuilds. Building a full race rotary is still a bargain compared to a piston equivalent.

 

Initial cost to build is essentially the same for a 4 or 6 cylinder piston motor of equal power. the problem is in the freshening part. the rotaries take more expertise to freshen then do a piston engine. the 12a or 13b has to come completely apart for an inspection or for simple apex seal replacement. piston engines can be serviced much easier and for a freshening it will not need to be completely broken down. In my 12 years of racing rotaries I have found it is much more expensive over time compared to a piston engine of equal power. If you do all the work yourself then it will be about the same, but if your paying engine builders it will be alot more expensive. I wish I could get 16 races from any engine I have ever raced. please forward the name and contact info of this engine builder I really could use his help.

 

I have never built a piston engine so I have no experience there. I've been told by others that have more experience than myself that a piston motor needs more frequent rebuilds and that the initial build is more expensive. I'm not sure about 16 races, but you might call Jesse Prather at Prather Racing, he builds a nice motor and can certainly speak to the longevity of the 12a platform. I know there's a handfull of good engine builders out there.

Tim what rotary motor are you running and what is your experience with longevity?

I blew up 2 motors until I finally bought a good one. It had about 4 races on it when I got it and I did another 4 plus 2 test days. Needs to be freshend up about now, but still seems fine. I never had the right carb on it but I've fixed that. I'm having another built right now.

 

I have over 200,000 on my untouched motor and she still runs strong. If the engine is properly built and properly cared for, then the sky is the limit... I'm beginning to close the gap on those damn Miatas during the Autocross events (finally).

 

I have run a turbo 13b, 13b peripheral port, and an E-production 13b(six port street port). the longest lasting motor was the turbo 13b. It was low boost and low revs it ran about 10 or eleven events over 2.5 years. PP motor lasted about 2.5 events(maybe 6 hours) before the bearings shredded. The first of 5 EP motors did not make one minute on track before it shredded the side seals. the other 4 lasted: 5 race hours plus 1 hour of dyno tuning, 1.5 race hours, 2 race hours plus 1 hour on dyno, 3 race hours plus 1/2 hour on dyno. All engines were built by local "rotary experts" with new parts. Professional and well respected rotary engine builders charge a very high premium for a high quality engine. One firend had a PP motor built by a very famous rotary racer and the final total was more than $10,000. For $10k I can have an 600hp dry sump V8 with money left over for the first freshening. My problem with the rotary engine in racing is a lack of good "semi pro" engine builders. In the piston engine world there are quite a few choices for good inexpensive engine builders for anything from Honda to chevy, but over the years the rotary connection have just dried up. there are alot of guys claiming to know everything there is about these engines, but I have yet to have any of them deliver. My problem is a lack of local talent and my inability to afford the real pro engine builders. Last year I paid more than $4000 for engine rebuilds, parts, and tuning. this excludes track time and expenses. Yes, I should have spent that upfront and got the good engine, but hind sight is 20/20 and I thought(wrong of course) that the supposed expert would deliver what he advertised.

 

I noticed this thread seems to be straying way off from what the original poster was asking about. From the sounds of it, if the engine speed is kept down (rev limiter set to ~7250?) and it's not abused or overheated it should last for quite a while.

You should probably also do some reliability mods like an oil pan baffle, all new fuel, oil, coolant and vacuum lines, a new PD, and so on.

 

A the Celmson Sports Car Club we run a 12a as a club auto-x car. The car runs maybe 50-60 runs per auto-x (not an exageration) and the motor has had basically no problems. That car gets pounded too, nothing we have come across has been a more reliable race car.