Tim Benton

iTrader: (1)

People get into spastic fits when we talk about displacement on our engines and whether or not they are truly 1.3L. Mazda's been bragging about the engine of the year honor's that it received for the renesis engine but what category did it win in you ask? It won best engine in 2.5 to 3L category.

Tim

diablone

iTrader: (2)

Actually it won:

Best New Engine of 2003,
2.5-3 Litre &
International Engine of the Year 2003

paw140

Yep, thats because it's effectively a 2.6l.

Tim Benton

iTrader: (1)

agreed, but someone will contest the fact

Tim

XSTransAm

I contest! because we only have 2 revolutions per power stroke

(had too)

jimlab

Yep, we have no shortage of jackasses in denial around here...

https://www.rx7club.com/showthread.p...hreadid=165579

https://www.rx7club.com/showthread.p...hreadid=244983

Kento

Sigh...

Hasn't this subject been beaten to way past death already? (by the way, I do agree that the rotary is actually a 2.6L... )

Andrew

iTrader: (1)

So, it still kicks the crap out of any sub 2.5L.

Tim Benton

iTrader: (1)

It's been beaten to near death, some twitching still lingering Not sure if its the death knell or not, probably not since it's like the synthetic oil debates that come back like Jason in the Halloween movies.

Tim

Kento

jimlab

With forced induction it does... how does an NA 13B without a bridgeport stack up against NA 4 cylinders? Not very ******* well, mate...

jimlab

As long as you've got bad actors like Zerobanger and unixpilot around, you'll always have sequels...

diablone

iTrader: (2)

And people like you, who keep bringing it back.

jimlab

You mean people like me who aren't afraid to point out when someone's wrong or just being outright stupid, don't you?

Scrapiron7

Mazda says it's a 1.3L.. that's all that matters to most of us

jimlab

Baaaaa... 1.3 Liter is good enough for us... baaaaa....

911GT2

Actually, if its anything but a 1.3l, it's a 3.9l. But it's still a 1.3l. I wrote up a decent explanation here:
http://boston-motorsports.com/forums...5&pagenumber=8

Scrapiron7

Damn straight

paw140

You didn't notice that your explanation is wrong? A 13B doesn't displace 3.9l per crank rev, like you say. It displaces 1.3l.

You all are living in your own little fantasy world if you think a 13B is comparable to a 1.3l piston engine.

Wargasm

Ya know, it depends how you define displacement...

If you believe that it's the difference in volume from min chamber volume to max chamber volume multiplied by the number of cylinders, then the rotary is a 1.3 if you ask me. (it's not its fault if it has a better design!)

If you believe that what matters is the amount of air that is sucked in in a given number of degrees of crank rotation, then I think it's a 2.6 liter.

I think that engineers would argue for the 1.3 case, while racing regulators would argue for 2.6.

Brian

paw140

I agree 100%. From an engineering standpoint, 2.6L doesn't make a whole lot of sense. One could easily make a case for 1.3L or 3.9L, for that matter. But we are comparing to other types of engines here, so we have to be careful.

Displacement is a pretty meaningless number anyway. It's all about power, fuel economy, and weight.

KevinK2

Key point ... there is no sae, astm or other official standard definition of displacement.

Per your 1st def'n, you have 6 faces acting like piston tops ... 6 x .65 = 3.9L displacement, taking 1.5 e-shaft revs to do it ... one down and back for ea face. wankle being a 4-stroke, u get all six faces fired in 3 revs.

This engineer would state there already is inconsistent displacement ratings for 2 and 4 stroke boingers, regarding actual aspiration per rev. A 13B would be 3.9L per a similar vague definition ... disp per piston x number of pistons. note that a 2-stoke boinger fires all cannons in 1 rev, 4-stroke boinger in 2 revs, wankel in 3 revs.

Since a vast majority of diesel and gasoline engines are 4-stroke boingers needing 2 revs to fire all faces, it is logical to compare the 13B performance based on it's 2.6L of 'ideal' aspiration in 2 e-shaft revs. Mazda implied this by accepting the award, and it is standard practice in racing.

If we could turn back time and start with a clean board, it would be best to rate engines based on 100%VE aspiration per output shaft rev .... 1.3L FD, and 5.0 stangs would be 2.5 stangs. 50cc leafblower would still be 50cc, but would be given compensation for it's partial effective stoke ... say compare with other engines 'one-rev-rated' at 35cc.

Rx-7Addict

iTrader: (2)

I couldnt agree more. Just look at the 660hp, 6.0 L enzo engine. Then compare it to a 6.0L truck engine that struggles to make 300hp. Apples to apples, both NA.. harder to compare NA & forced induction

Or compare a 2.0L, 240hp Honda S2000 engine to a 2.2 cavalier engine with like 120hp

0110-M-P

iTrader: (10)

So based on the fact that the 2-stroke has one rev and the 4-stoke has two revs, would that mean the rotary having three revs would make it a 6-stroke(add 2 strokes per rev) or dare I say an 8-stroke(squaring the number of strokes per rev).

Haha....just kidding.

But seriously, I don't think piston engines should even be compared to rotaries. They are just too much unlike each other to get a good solid comparison. Just my .02.

M-P

Tim Benton

iTrader: (1)

I'm with KevinK2, in that Mazda accepted the award so it implies that Mazda realizes it's similar to a 2.5 to 3.0L piston engine. Or why not just have an award for just rotaries if you can't categorize it.

Tim