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Thread: RX8 engine - 1.3 or 2.6 Litre ?

  1. #16
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    Quote Originally Posted by Ferrari Tifosi
    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
    Cedric - I sound like a chipmunk on there. Some friends of mine were like, "were you going through puberty?" I was like, no I was already 20, I just sound like a girl.

  2. #17
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    Quote Originally Posted by Renesis
    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
    "A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'

  3. #18
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    Quote Originally Posted by Renesis
    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.
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  4. #19
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    i was thinking the 13b

  5. #20
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    Quote Originally Posted by Renesis
    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)

  6. #21
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    okay. good stuff.

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

  7. #22
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    the above articles already answered the original question so i'll follow up

    Quote Originally Posted by Renesis
    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.
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  8. #23
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    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?

  9. #24
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    Quote Originally Posted by Renesis
    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
    "A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'

  10. #25
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    Quote Originally Posted by Renesis
    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.
    "A woman without curves is like a road without bends, you might get to your destination quicker but the ride is boring as hell'

  11. #26
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    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...
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  12. #27
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    Quote Originally Posted by megotmea7
    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

  13. #28
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    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...
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  14. #29
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    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.
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  15. #30
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    Quote Originally Posted by Ferrari Tifosi
    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
    Last edited by megotmea7; 08-09-2004 at 01:10 PM.
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