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View Full Version : RX8 engine - 1.3 or 2.6 Litre ?



Mustang
08-05-2004, 03:55 PM
Does the RX8 count as a 1.3L because when i was looking on my other forum i found this

this was the original question


This car is the best i ever seen! And 1.3L rotary engine one of the most powerful in the world!! New Ford Mustang GT produsing only 65hp per 1 litter. Ferrari 360 Modena produsing 111hp per 1 litter. BMW M3 have 104 hp per litter. Lamborghini Gallardo- 100 horses per litter. Lamborghini Murcielago 93hp per litter. MAZDA RX8 produsing 149 horse powers per 1 litter!!!!!!! what u think about that!!!! If that engine was same size as Lamborghini Murcielago (6.2L) it will produse 923hp but Murcielago have only 580hp!!! THIS CAR IS THE BEST!!! Anybody know any car that can beat RX8 Hp per litter with out any upgrades?

and this is the answer that it recieved


they rate it at 1.3 liters but in actuallity it is more than that. Regardless of what you think the displacment is, the fact is the "measured' displacment is 1.3 liters. Both rotors (when fired) will only ignite 1.3 liters of mixture at any given time. Guess what Sherlock... the other face still has to wait its turn to produce power. It is true that the engine will consume 2.6 liter of air in "2" rotations of its eccentric shaft, there for it IS 2.6 liters. SWEET.... so since only 1/2 of a 03 cobra's pistons actually "fire" in one revolution, they have ~2.3 liters of displacement. They have 390 HP so that would be what? 169.5 HP per liter So face it your rotary sucks, the whole engine is 2.6 liters and just because the whole 2 rotors arent firing doesn't mean it is only 1.3 liters

does this really mean that the Rotary engine is a 2.6 ?

Renesis
08-05-2004, 04:18 PM
http://www.rx7.com/techarticles_displacement.html

Renesis
08-05-2004, 04:21 PM
and another...

"The SAE (Society of Automotive Engineers) defined way of measuring the displacement of a rotary is to measure the difference in volume of the combustion chamber between when it is at its largest and smallest. Since each rotor has three of these chambers and there is one combustion event per rotation of the eccentric shaft, a 1.3 liter rotary would burn 1.3 liters of fuel and air per eccentric shaft rotation. A 2.6 liter reciprocating engine would burn this same amount. This confuses some people and makes them claim that rotary engines have twice the displacement their manufacturers claim they have. There is not right or wrong in this case. Rotary engines are different from reciprocating engines, so of course they need to be treated differently."
(http://www.louisville.edu/~asjobs01/assignments/third_report.html)

Mustang
08-05-2004, 04:23 PM
ok thanks alot

ThoughtlessX8
08-05-2004, 04:30 PM
Just tell the guy his Cobra with all 169.5hp/litre is still a Ford piece of shit and I'd much rather an RX-7/8 any day of any week of any year EVER!!! Ford Cobras are still piles of shit.

SIMPLETON
08-05-2004, 04:38 PM
how does this work. Math has failed me many tomes in life, this is 1 of them

Mustang
08-05-2004, 04:38 PM
Just tell the guy his Cobra with all 169.5hp/litre is still a Ford piece of shit and I'd much rather an RX-7/8 any day of any week of any year EVER!!! Ford Cobras are still piles of shit.


hmn lets see that ford piece of "shit" also make the mustang, GT and what the hell is wrong with the cobra,

The mustang set the trend for a new era of muscle cars in the 60's and was the biggest selling car of its time in america

the GT has been designed from the GT40 which if i remember correctly won Le-mans on a number of occasions

the cobra also did that when they got the daytona version sorted, and BEAT ferrari :)

oh and if ford are so shit then why are they at the top of the WRC and have been for many years and this is one of the toughest challenges for cars. not many could stand what these cars go through.

Now theat they have braught these three cars back i think it is amazing and ford have done an excelent job with them.

Mustang
08-05-2004, 04:40 PM
how does this work. Math has failed me many tomes in life, this is 1 of them


haha that has either been tinkered with no photoshop or there was a slight malfunciton with the forum for a second, it is working now :)

Ferrari Tifosi
08-05-2004, 05:01 PM
hmn lets see that ford piece of "shit" also make the mustang, GT and what the hell is wrong with the cobra,

The mustang set the trend for a new era of muscle cars in the 60's and was the biggest selling car of its time in america

the GT has been designed from the GT40 which if i remember correctly won Le-mans on a number of occasions

the cobra also did that when they got the daytona version sorted, and BEAT ferrari :)

oh and if ford are so shit then why are they at the top of the WRC and have been for many years and this is one of the toughest challenges for cars. not many could stand what these cars go through.

Now theat they have braught these three cars back i think it is amazing and ford have done an excelent job with them.

I believe he was referring to the Mustang Cobra, not the Shelby Cobra which only has a Ford engine, the car in whole is NOT a Ford. Its Chassis is from AC, and it was all put together by Carroll Shelby.

Mustang
08-05-2004, 05:09 PM
I believe he was referring to the Mustang Cobra, not the Shelby Cobra which only has a Ford engine, the car in whole is NOT a Ford. Its Chassis is from AC, and it was all put together by Carroll Shelby.


still i dont think that there is anything wrong with the mustang cobra, and if you are saying that, that cobra isnt a proper ford does that mean that the new one isnt too because it was produced with Shelby. :rolleyes:

And another thing is ford are so shit then, why is aston martin so good, the DB7 had the same chassis as the old jag x-type i think and that chassis came from the ford mondeo, sure Aston might have changed to a newly designed chassis for the DB9 but that is only because they have Ford money and they wouldnt be getting that money if ford were shit

Egg Nog
08-05-2004, 05:10 PM
Most people need to realise that hp/litre is an irrelevent and technically useless statistic, unless of course there is a limit on displacement.

A more important thing to look at is power in relation to efficiency and emissions. In this respect, rotaries are nothing to get worked up about. They do have the "wow" factor, though... ;)

Ferrari Tifosi
08-05-2004, 05:23 PM
Most people need to realise that hp/litre is an irrelevent and technically useless statistic, unless of course there is a limit on displacement.

A more important thing to look at is power in relation to efficiency and emissions. In this respect, rotaries are nothing to get worked up about. They do have the "wow" factor, though... ;)

Well, not really. If you can make more hp/liter, then in turn you can make a smaller engine that in turn weighs less and improves performance.

Also rotaries are great, 3 MOVING PARTS = a hell of a lot better than 100 + on a standard reciprocating piston engine. Less chance a mechanical failure.

Renesis
08-05-2004, 05:25 PM
Most people need to realise that hp/litre is an irrelevent and technically useless statistic, unless of course there is a limit on displacement.

A more important thing to look at is power in relation to efficiency and emissions. In this respect, rotaries are nothing to get worked up about. They do have the "wow" factor, though... ;)

uh yeah. rotaries are preeety lousy when it comes to power efficiency, and im not going to deny this.

but arent we forgetting that weight is in fact an issue?
especially when someone is a lightweight car enthusiast (and im not being critical)
the rotary creates excellent power considering its weight and size. So if you wanted a nimble car that could turn on a dime and weighs like a feather, wouldnt you maybe want a lightweight engine? like a rotary?

so when you think about rotaries, power isnt really the focus, but maybe weight and size efficiency is


i really wish someone would create an extremely lightweight rotary sportscar, not like the rx8, but maybe built with carbon and a mid-engine design. Now that would be a car meant for the backroads, and my garage.

Ferrari Tifosi
08-05-2004, 05:25 PM
still i dont think that there is anything wrong with the mustang cobra, and if you are saying that, that cobra isnt a proper ford does that mean that the new one isnt too because it was produced with Shelby. :rolleyes:

And another thing is ford are so shit then, why is aston martin so good, the DB7 had the same chassis as the old jag x-type i think and that chassis came from the ford mondeo, sure Aston might have changed to a newly designed chassis for the DB9 but that is only because they have Ford money and they wouldnt be getting that money if ford were shit

All I was saying is the with the original Cobra, the extent of Ford in it was the engine, which they didn't even develop specifically for that car. Ford deserves no credit for the ORIGINAL Shelby Cobra. Not saying I dislike ford, in fact I like them a lot.

Renesis
08-05-2004, 05:27 PM
Well, not really. If you can make more hp/liter, then in turn you can make a smaller engine that in turn weighs less and improves performance.

Also rotaries are great, 3 MOVING PARTS = a hell of a lot better than 100 + on a standard reciprocating piston engine. Less chance a mechanical failure.

oh boy, here we go again
theory versus reality: rotaries arent as reliable as you think
(look into past threads if you dont believe)

Mustang
08-05-2004, 05:29 PM
All I was saying is the with the original Cobra, the extent of Ford in it was the engine, which they didn't even develop specifically for that car. Ford deserves no credit for the ORIGINAL Shelby Cobra. Not saying I dislike ford, in fact I like them a lot.


i can understand that they didnt have a big part in it i just used that because it completed the trio and it was names the FORD shelby cobta

glad to hear you like em :)

Matra et Alpine
08-05-2004, 05:36 PM
i really wish someone would create an extremely lightweight rotary sportscar, not like the rx8, but maybe built with carbon and a mid-engine design. Now that would be a car meant for the backroads, and my garage.
Not a lightweight sportscar, but motorbikes played wiuth Rotaries and culminated in the JPS Norton F1 which won pretty much everything - until the "equivalency" rule was brought in and it was realised that the '750' was the otto-cycle equivalent of a 1500. So it got restricted and couldn't match I4s and was dropped.
Great sound though, they had them out at IoM TT a couple of years back :)

Ferrari Tifosi
08-05-2004, 05:36 PM
oh boy, here we go again
theory versus reality: rotaries arent as reliable as you think
(look into past threads if you dont believe)

What rotary engine in specific? Because if its the 13B twin turbo that was in the RX-7 that you're are referring to, that wasn't because it was a rotary, it was because Mazda designed the engine badly, specifically the apex seals and the cooling system.

Renesis
08-05-2004, 05:48 PM
i was thinking the 13b

Egg Nog
08-05-2004, 06:04 PM
uh yeah. rotaries are preeety lousy when it comes to power efficiency, and im not going to deny this.

but arent we forgetting that weight is in fact an issue?
especially when someone is a lightweight car enthusiast (and im not being critical)
the rotary creates excellent power considering its weight and size. So if you wanted a nimble car that could turn on a dime and weighs like a feather, wouldnt you maybe want a lightweight engine? like a rotary?

In a situation where the difference is so minimal, I'd take efficiency any day. Despite being physically compact, the rotary is not really very lightweight. Lets do a comparison:

Renesis mass: 130kg.
Renesis power: 230hp
RX-8 (1375kg) milage: 18/25 (miles per American gallon)

LS1 V8 mass: 153kg
LS1 V8 power: 350hp
C5 Corvette (1460kg) milage: 19/28 (miles per American gallon)

Renesis
08-05-2004, 06:12 PM
okay. good stuff.

but isnt LS1 made of aluminum, while renesis is forged steel?
so what then, if renesis were aluminum?

megotmea7
08-05-2004, 09:39 PM
the above articles already answered the original question so i'll follow up


okay. good stuff.

but isnt LS1 made of aluminum, while renesis is forged steel?
so what then, if renesis were aluminum?
mazda has no doubt experemented with this but deemed it inpractical(more on this in a sec). the aftermarket has also gone this route with some success but the ppl who buy these aluminum housings know all about proper warm up. as we all know aluminum doesnt like heat, esp. not rapid heat change. rotaries can produce alot of heat very quickly if not warmed up properly. if not propperly warmed up these aluminum housings will warp compramising the water seal and causeing coolant to leak into the combustion chamber and exploding gasses to vent into the cooling system. needless to say this isnt good so mazda decided to "idiot proof" their engine so they use a more forgiving (and heavier) material, steel, to prevent this from happening. because the engineer at mazda know not every average joe that buys their cars is going to take to 5-10 minutes to warm uip their car or pull the car over if it starts overheating. the 13b-REW is a pretty light engine by itself but once you add on all the turbo components, intercooler, etc. it starts catching up pretty quickly to the competition (i.e small block chevy's, the supra's exeedingly heavy cast block with all the turbo components, etc) the major advantages of the rotary is its compactness not its weight, and its smoothness and powerdelivery, and turbo friendlyness. its a trade off as it has many disadvantages also. :)

Renesis
08-06-2004, 04:22 PM
okay, in that case could it be possible to create a version of rotary that had steel housings, steel rotors, and everything else made of aluminum or maybe ceramics, so that it would be significantly lighter but also less prone to the warping effects of heat?

Matra et Alpine
08-06-2004, 04:29 PM
okay, in that case could it be possible to create a version of rotary that had steel housings, steel rotors, and everything else made of aluminum or maybe ceramics, so that it would be significantly lighter but also less prone to the warping effects of heat?
Unlikely to be significant.
Rotary engines unique benefit of size comes because they don't need to build a block capable of holding and sustaing the forces of all those components moving in allt he directions. So ordinary engines need very strong blocks, heads etc. This takes lots of metal and strengthening ribs etc which all add weight and size beyond the steel liners and pistons. In a Rotary tho' it's all simpler. On the block ALL the forces are the same and ALL emanate from the combusion chamber trying to 'grow'. So there isn't a need for as much metal and strengthening ribs.

So replacing the outer section of a Rotary block with alloy instaed of steel is not as big a win as with an in-line or V. So nobody really bothers beyond the engineering challenge :)

Matra et Alpine
08-06-2004, 04:32 PM
oh boy, here we go again
theory versus reality: rotaries arent as reliable as you think
(look into past threads if you dont believe)
True, but neither are they as bad as you think especially in a 'tuned' and raced condition.

Search for the thread I'd posted LOTS of the details last time this came up.
Basically the Mazda engine and car were THE MOST RELIABLE EVER in all the years the Le Mans race has run.

megotmea7
08-06-2004, 08:14 PM
correct, even properly maintained street rotaries last very long times. especially the 13b and 13b-t found in the FC, in the FD certain design inadiquacies must be adressed due to mazdas cost cutting and wanting to get their new sports car out on the show room floor to compete with the likes of the skyline and supra. just a few: coolant catch tank needs replacing or removal as the plastic OEM part tended to crack and spray your coolant all over the road(not good esp. on a hot running rotary), new aluminum radiator as the stock plastic end caps have been known to do the same thing as the catch tank, new higher temp rated fual lines(should be under the recall) as they used to age quickly and crack due to the heat spraying fuel all over the engine bay causing an engine fire, new radiator hoses in regualar intervals as the stock units tended to do the same thing as the fuel lines and again spray your coolant all over the road, vacuum line replacement and simplifacation aids in preserving turbo switchover reliabilty as most of the lines were just slipped on the nipple with very little or no adhesive or ties rendering the secondary turbo unable to come online(this ones a big pain in the ass but worth the ~$50 you'll pay ten-fold), replace the downpipe/precat with an aftermarket unit as the precat tends to get clogged trapping heat in the engine bay(adds power and makes the car run cooler),, warm up the engine under light load off boost to prevent the rotor housing from warping compramising the water jacket, and top off the engine oil every 2 weeks or so with high quality dino oil as rotaries inject a small amount of oil in the rotor to keep things lubricated and synthetics dont burn off as cleanly leaving residue. after you do these simple reliability mods and regualr maintenence(change your oil twice as much as you would any other car) you can expect an FD to last hundreds of thousands of miles provided you dont abuse it... :)

KnifeEdge_2K1
08-07-2004, 10:14 AM
hundreds of thousands of miles provided you dont abuse it... :)

master of stating the obvious ...

any engine will last hundreds of thousands of miles provided you don't abuse it

megotmea7
08-07-2004, 04:32 PM
thank you for being a smart ass, this is contrary to the belief and somewhat truth that most rotaries dont last past 100k miles. it is due to ppl not taking care of them and abusing them. then they wonder why the rotary is so unreliable...

Ferrari Tifosi
08-09-2004, 11:14 AM
One of the biggest problems with the RX-7 turbo models, If I remember right, wasn't the car itself. It was people modifying the engine poorly and overlooking very important changes to be made when running higher boost. Once again it was usually apex seals that blew and as a result damaged the engine. This is what I believe gave this car and more specifically its rotary engine a bad name.

megotmea7
08-09-2004, 12:25 PM
One of the biggest problems with the RX-7 turbo models, If I remember right, wasn't the car itself. It was people modifying the engine poorly and overlooking very important changes to be made when running higher boost. Once again it was usually apex seals that blew and as a result damaged the engine. This is what I believe gave this car and more specifically its rotary engine a bad name.
very true, if an FD was modified in teh wrong way (i.e. exhaust, upping boost pressure, larger turbo, intake, etc.) the stock computer (which is the less common speed density system) would be inable to compensate for the additional airflow(couldnt recognise the additional fuel requirments) into the combustion chambers. this would cause the car to run lean and lead to detonation which is almost instant death for a rotary due to the fragile nature of its apex seals. an aftermarket piggyback or stand alone ECU/fuel compueter is needed to make the nessesary compensations