titaniumgrey

Well , my friend was telling me about how rotary engines were inefficient today and how they don't have compression or something and suck up gas ? , anyone have any counter statements to make against this guy ?

guy321

Run over his foot then ask him about compression!

Check out this thread.. especially rotarygod's posts.

https://www.rx8club.com/showthread.p...y&pagenumber=1

mysql101

rotary engine does three times the work per cycle than a piston. It's far more efficient.

Each cycle it is doing exhaust, intake and compression/ignition at the same time. As him how much his piston engine does per cycle.

Add to it that it can be smaller than a similar powered v6, and lower in the car chassis....

northern-8

Let's see, 238 hp from 1.3L.

That works out to 183 hp/L without a turbo charger.
Sounds pretty efficient to me as the only 2 other production cars that produce more than 100 hp/L are the Honda S2000 and the Ferrari 360.

Your friend is right though, if you want fuel efficiency, get a Honda Civic.

robertdot

Do you own an 8? If so, that should be enough.

If not, here are some quick answers. The Renesis in the '8 has a 10.0:1 compression ratio. I don't really even know what the hell that means to not have compression. Compression is part of an internal combustion engine. I think I'm wasting my time, because a statement like that is assinine and ignorant. Anyway, I'll hope he didn't actually say that.

The '8 is projected to have 237 HP (though 250 is possible with the right fuel maps). My best MPG has been about 19.2 non-highway (A/C off, shifting before 4000 RPM). My worst was 14.25 (A/C when needed, shifting around 7,000 - 8,000 RPM). My average is about 16.3 (A/C on various driving styles).

The Renesis is a 1.3 L engine (or that is one way of looking at it... you can read rotarygod's post on what the real displacement is / could be... maybe even 3 times what is claimed) that gets (realistically) 16 MPG (claimed 19 on street) and 237 (claimed) HP. I got mine for $27K.

The 350Z is a 3.5 L engine that gets (claimed, probably not realistic) 20 MPG and (claimed) 287 HP. It starts about $27K (based on MSRP).

The S2000 is a 2.2 L engine that gets (claimed) 20 MPG and (claimed) 240 HP. It starts at $32K.

I think realistically, the S2000 is probably the closest car spec for spec and it gets about the same MPG and power. Plus, with some work to the Renesis, it will rev 12 K or more. I think the S2000 probably can't be pushed any more than it is. What I mean is that we have room to go up. S2K is, IMO, close to maxed out, even with upgraded internals. But, again, I haven't researched much about the S2K's modability. (***Ignorning Forced Induction!!!***)

So, are they inefficient? That depends on what you want to know. They are really small and really light and put out a ton of power for their size. They are efficient in that way. If I assume that the engine is a 1.3 L (which, I don't think I'd really call it that), the MPG looks inefficient. If we assume it is a 3.9 L, then the MPG starts to make sense (Fords 4.0 L gets 17 non-highway). But, really, efficency is based on what it can do with what it has. It can do alot for what it has.

That ignores all the other really attractive features of the '8 (50/50 weight distribution for one) and focuses on the engine. Hope that helps.

titaniumgrey

well , my friend shut up I think , thanks for the responses , and nope he doesn't own a rx-8 ,he owns torque american station wagon.

guy321

So, did he want to race your 8 because the 8 has no torque and the satanwagon will take it??!

mysql101

heh. your friend owns a station wagon.

Why do you even listen to him?

titaniumgrey

lol ... he actually did say that , lmao ... I don't want to race a station wagon ><


and he is pretty smart so I assumed that he knew what he was talkin about , hes a chemical engineer or something

Silver04RX8

Let your friend test drive an 8 and see how he feels about it. I bet he will get back in his P.O.S satan Wagon and feel really crappy about his ride.

Feras

iTrader: (1)

celica gets 180hp from a 1.8L N/A

Feras

iTrader: (1)

oh yeah and tell your friend that the renesis is a race car engine...Mazdastar Formula car uses a 240HP Renesis, almost identical to the one we have.

titaniumgrey

rsx type S gets 200 hp from 2.0 L N/A too

guy321

They could only get 3, THREE, Tres, SAAM, SAN, TROIS more HP!?

Also, the last two cars make 100hp/l the statement was MORE than 100hp/l

babylou

Ummm...yah...but all of the other umpteen race cars use piston engines. Well except for those turbine powered Granatelli jobs at Indy in the 60's.

Nubo

Fuel efficiency will probably never be quite as good as piston engines of comparable power because the combustion "chamber" has a weird shape and is moving through space. BUT...

There are lots of measures of efficiency

miles per gallon
horsepower per litre
fun per gallon :-)
satisfaction per dollar spent

robertdot

So? I think the point was that the Renesis that is in our car (as in the exact same engine that is sitting in RX-8s right now) is used as a race engine, not that our type of engine is used in a racecar.

For example: So, the '8's engine is used in race cars while the Z's engine is not. A modified version of the Z's engine may be, but not the engine that is sitting in the production vehicle at this moment.

medcina

The Elise gets 190 HP out of the same 1.8 L Cellica engine.

Just busting chops...

PoorCollegeKid

Celica SSII (2ZZ-GE Celica in the rest of the world): 190hp from 1.8L
M3: 333hp from 3.2L
GT3: 380hp from 3.6L
DC5R: 220hp from 2.0L
DC2R: 195hp from 1.8L

...and then there are the exotics, of course.

DRx

183 hp/Litre can't be touched by any other production car, period, which are all in the ball park of 100-115 hp/Litre. I think thats the point. Not to mention the lowered center of gravity...

beachdog

The rotary is efficient in a "less is more" sense. With only three major moving parts it has a design elegance that a piston engine cannot match. Fewer moving parts means less mass to move and less friction to overcome. This makes it a very efficient mechanical design.

It is also efficient because there are no wasted cycles as the rotors travel. Each face is charged, compressed and ready to fire as it passes the spark plugs. Piston engines use half their cycles for exhaust.

From a thermal perspective it is another story. The engine wastes a lot of heat. All the heat that comes through the exhaust system (the engine runs rich to cool the exhaust system) and radiates out of the engine and cooling system is wasted energy that could have been generating more HP or better fuel mileage.

There have been many detailed discussions on the operation of the rotary engine, search threads for rotarygod.

BaronVonBigmeat

Thermodynamically speaking, the rotary isn't very efficient at all.

If you're talking about "packaging efficiency" ie size/weight per HP, then sure, it's very efficient.

Further discussion on why the rotary is inefficient:

http://quasiturbine.promci.qc.ca/QTpasWankel.html

Purple Helmet

you forgot the Toyota Celica GTS, it has 100 HP per liter BEFORE the TRD exhaust which adds another 14 HP, giving it 194 HP from 1.8 liters, get the off road TRD exhaust and you have another 20 to 180 and you have 200hp from 1.8L with no turbo, My GTS got 30 mpg at over 70mph and I had the street legal TRD exhaust, and it had a bad *** factory stereo, but as in all systems anything can be upgraded and replaced, but for stock, it was a hell of a lot better that the stock rx8, I already replaced my system, except the head unit, as I will wait until a quality panel comes along

Purple Helmet

OH YEAH, I forgot to mention that there are MANY DAILY DRIVER Toyota TURBO Supras, that have upt to 300 HP per liter and more,.......DAILY DRIVERS, so lets not all start giving each other reach arounds quite yet.... www.suprastore.com

Purple Helmet

and three moving parts also means that the engine stress is concentrated in those three moving parts, where as a standard pissston engine the mechanical stress is distributed everywhere, I would say the valves see the most stress