How Good are Modern Auto Engines?

[the_other_dougreeves]

Originally Posted by rtry9a

Like you said, a race-prepped rotary often is not opened up during the entire season while its piston-powered peers generally carry around spares and are broken down/ overhauled after each race. That great durability, and its light weight, are reasons why the rotary engine has been voted out or penalized in most race categories. The races are mostly rigged by the big money competitors.

F1 engines are about the highest stressed engines out there short of the Shuttle's main engines. They are designed to last for 2 weekends of qualifying and racing - other engines are used for practice. I sure don't want to fly behind one of those.

Endurance racing engines can be very reliable - within the context of motorsport. The Audi R8's 3.6L twin-turbo V8 made 550 to 600 Hp (The ACO kept shrinking the inlet restrictor) and weighed about 150kg (330lb). The engine never failed in competition (although it did during practice). Audi's standard practice with R8 engines was to build one, put it on the dyno for 8-10 hours, simulating laps at LeMans (i.e., going through rev and load profiles experienced during the laps) and if the engine passed, it got shipped out. What did they cost? If you have to ask....

The 13Bs that are used in Formula Mazda are stock - no race prep is allowed. Engines are sealed at overhaul and must remain sealed.

TODR

[rtry9a]

Originally Posted by rv6ejguy

Naw, I don't buy this stuff. I built and road raced cars for 13 years. My piston engines lasted the whole season without coming apart and we won 7 championships- way more than anyone else in that time period.

Engines had stock rods, blocks, heads, bearings and cranks and were pushing over 200hp/ L specific output in turbocharged form. The long blocks were worth less than $3000 complete and came from the junkyard originally. Yearly rebuilds consisted of a valve reface, mag the crank and rods, new rings and gaskets (about $400-$500). I re-used bearings on my 1407cc engine 4 seasons in a row. We raced some fast Wankels but they were no match for us in hp. I beat one consistently which had a close ratio gearbox (I had stock ratios) and he was in the class above me. Our same class car annihilated all the other Mazdas including the best PP ones.

If people are wearing out piston engines in amateur road racing in less than a season, the wrong people are prepping or driving them.

You consider the Daytona and LeMans 24 hour races "amateur road racing"? I think there is a slight difference in our frames of reference,

There is no doubt that a prepped reciprocating engine can be built to withstand the considerable internal stresses inherent when the pistons and con rods constantly work against themselves- IF you throw enough money and exotic materials at the problem and expect "frequent" breakdowns. The problem is far worse at high rpms often seen during races. Rotary and turbine engines are very different in that regard, and their durability records reflect that difference.

[rv6ejguy]

Originally Posted by rtry9a

You consider the Daytona and LeMans 24 hour races "amateur road racing"? I think there is a slight difference in our frames of reference,

There is no doubt that a prepped reciprocating engine can be built to withstand the considerable internal stresses inherent when the pistons and con rods constantly work against themselves- IF you throw enough money and exotic materials at the problem and expect "frequent" breakdowns. The problem is far worse at high rpms often seen during races. Rotary and turbine engines are very different in that regard, and their durability records reflect that difference.

I consider SCCA regional and club racing amateur racing and this is the type I was involved in. I don't consider Daytona or LeMans amateur racing.

Wankels had an admirable record racing years ago but are overshadowed today by modern 4 valve piston engines in almost every form of racing- amateur or professional. How many LeMans races have Wankels won in the last decade? Zero. All been piston engines with those pesky reciprocating parts. If Wankels were so superior, they'd be in much more widespread use as the patents have long ago expired. My experience in 13 years of engine building (over 200 engines) and road racing myself was zero rod failures on the engines under my program and this was all with stock rods at rpms as much as 2000 rpm over factory redlines.

Today with multitudes of superior aftermarket rods available, even higher safety margins are available at low cost. Despite your perceptions about piston engines, rod failure is pretty much a non-issue these days. GM's durability tests at high rpm for thousands of hours clearly prove that on production engines.

As one more data point, A friend endurance raced a 4AGE powered Showroom Stock MR2 for about 8 years in Canada and the NW US. The engine accumulated almost 25,000 km of RACE miles, shifting at 7500 rpm. He only changed the timing belt once in that time and never touched the engine.

[rtry9a]

Ross,
The point made was that the Wankels were outlawed at Lemans in 1975 after they won convincingly in 1974. It is sorta difficult to log wins when they are either outlawed or penalized unfairly in most racing classes. IMSA is the exception, and there Mazda has pretty much dominated. Ive always held that the wankel is a much better aircraft motor than automotive, with the possible exception of automotive racing where the engine has to perform under full load for long periods of time and light weight is a virtue.

A minor point- SCAA racing is more about handling than power is it not?

Wankels have never been particularly great at producing low end torque -there the recips ARE the better choice (road driving); the rotary shines at full power (in aircraft apps), particularly in the realm where the recips drop in performance. Im far from negative about reciprocating engines- they have come a long way thru the ages. But they are what they are, the physics of mass and motion do not lie. I value your frequent contributions; Subaru/Egg is my second choice largely from your recommendation and experience.

A quick question: Did you ever look at the Mitsubishi DSM motor? I overhauled one once and was very impressed with the design of the aluminum head- too bad it had an iron block.

[Mike S]

Originally Posted by rtry9a

Ross,
The point made was that the Wankels were outlawed at Lemans in 1975 after they won convincingly in 1974. It is sorta difficult to log wins when they are either outlawed or penalized unfairly in most racing classes.

EXACTLY.

IIRC, the wankel was penalized by multiplying the displacement by 1.5 or something-------made them run against cars with half again more displacement----and they still won most of the events they were allowed to run in.

Same with the Indy turbine car-----anyone remember that???

http://www.turbinecowboy.com/carstru...hotoalbum_view

One of the big pluses touted for racing is that so many technical advances happen in competition.

However, when the competition is outlawed, sure does stifle growth.

[the_other_dougreeves]

Originally Posted by rv6ejguy

I consider SCCA regional and club racing amateur racing and this is the type I was involved in. I don't consider Daytona or LeMans amateur racing.

Wankels had an admirable record racing years ago but are overshadowed today by modern 4 valve piston engines in almost every form of racing- amateur or professional. How many LeMans races have Wankels won in the last decade? Zero. All been piston engines with those pesky reciprocating parts. If Wankels were so superior, they'd be in much more widespread use as the patents have long ago expired.

The ACO changed the rules on restrictors for rotary engines to essentially make them less competitive after Mazda won LeMans is 1991. In all fairness, it's hard to make competition adjustments to the rotary based on displacement due to its nature. Maybe if a French company made the rotary, the ACO would change the rules back ....

I think Mazda would like the have the rotary return to LeMans, but they are choosing to go forward with their 4-cyl designed with AER. They are successfully racing rotaries in GT cars (e.g., Grand-Am).

On the aviation front, Rotaties are being used in applications where weight and size are critical, e.g., UAVs and self-launching motorgliders. I don't know if they can be competitive with pistons (particularly diesels) on other GA applications where weight and size are less critical and fuel efficiency is more important.

TODR

[rv6ejguy]

Typically any engine design which wins a lot starts facing weight, altered equivalence factors or inlet/ rev restrictions. One could say the same has afflicted gasoline engines in endurance racing recently. This is a part of racing.

Success may depend more on lobbying or sandbagging to delay rule changes.

The rotary was typically factored at 2X swept volume for years in IMSA and SCCA and that worked well. They traded many wins with Nissan Z cars and their L series engines.

The FIA factored turbos at 1.4 times many years ago. As technology progressed, this had to be changed as turbos dominated everywhere they were allowed and just continued to do so despite factor changes. Finally they were simply outlawed in most forms of racing. The whiners are typically the losers who lacked the vision to develop something different.

I generally agree, Wankels make a better race engine than passenger car engine. On the track, I respected them but never feared them.

I think this whole thread has strayed somewhat. If it makes the Wankel guys happy- yes Wankels are very reliable too and always have been.

[Rotary10-RV]

Originally Posted by rv6ejguy

Wankels had an admirable record racing years ago but are overshadowed today by modern 4 valve piston engines in almost every form of racing- amateur or professional. How many LeMans races have Wankels won in the last decade? Zero. All been piston engines with those pesky reciprocating parts. If Wankels were so superior, they'd be in much more widespread use as the patents have long ago expired. My experience in 13 years of engine building (over 200 engines) and road racing myself was zero rod failures on the engines under my program and this was all with stock rods at rpms as much as 2000 rpm over factory redlines.

Ross,
I very much concurr with your views on modern piston engines. However I must point out the fact that after Mazda won the Le Mans 24 hour outright in 1991 the rotary engine was banned from future prototype racing. That is why you haven't heard about them lately. There is a great deal of effort made to mannuipulate the rules to various advantage, which is why we have DIESELS winning lately. There are several conversion engines that are attractive both piston and rotary. I have long maintained the rotary makes a better aircraft engine than car engine! The biggest need is for a quality PSRU for a reasonable price. I am supprised that some of the aftermarket transmission designers haven't taken a crack at it. Liability scares off most I'm sure.
Bill Jepson

[Jconard]

The only competitive roadracing class where the rotary was competitive for a whole season without rebuild were classes that were spec mazda, like formula star mazda.

In formula atlantic, or csports racing (often super Vee Ralts with a body) they are not competitive with the relatively old tech cosworths and 4AGE engines without frequent rebuilds....this is just the nautre of racing.

The swept volume rules sure seemed fair to me, but the reality is that the fuel economy rules have eliminated the rotary where they would otherwise be allowed.

[Rotary10-RV]

Originally Posted by Jconard

The only competitive roadracing class where the rotary was competitive for a whole season without rebuild were classes that were spec mazda, like formula star mazda.

In formula atlantic, or csports racing (often super Vee Ralts with a body) they are not competitive with the relatively old tech cosworths and 4AGE engines without frequent rebuilds....this is just the nautre of racing.

The swept volume rules sure seemed fair to me, but the reality is that the fuel economy rules have eliminated the rotary where they would otherwise be allowed.

The current RX-8s have been very successful in racing, but they have been adding weight for "pairity" for the whole season. When something is different and successful it often is killed by rules changes. The indy turbines are a classic example. The first car had some advantages and would have won if a transmission bearing hadn't failed at 495 mile point. The inlet area was cut in half for the next year. Lotus built a VERY innovative chassis for a smaller turbine that was only competitive because of the CHASSIS. They didn't win but the next year inlet areas were reduced to the point that a turbine wouldn't even run. Effectively a ban. Racing is a rules game. Doesn't mean a engine isn't a good one, just that it "fits" the current rules package. We need to keep our focus. That is, is the engine a good one for our use, in an airplane. Rotaries, Subarus, Chevy, Ford, Lycoming I don't care if the package is well engineered. By the way I have never see a rotary Formula C, or C sports racer. When I was building them rotaries weren't allowed period.
Bill Jepson