Jeezus

iTrader: (4)

Check this out. I knew that Rotarys burn hotter than pistons, but here is a comparison. This picture is with my Camera Phone (sorry, will get real pics when I find the camera) of my exhaust.

1982 Mazda RX7
Mazdaspeed Protege Exhaust

2002 Mazda Protege
Mazdaspeed Protege Exhaust

Simple, and about as good and fair a comparison as I can get . If you look closly at the rotary exhaust on the left, you can see the tip starting to turn a tan/blueish color. The piston... well, Still shiney!

Naegleria_Fowleri

Have both exhausts been on for the same amount of time?

Jeezus

iTrader: (4)

No, The Protege's has been on for a little over a year, the RX's... about 3 weeks.

Naegleria_Fowleri

That is really crazy for only three weeks. Good proof.

bugman1973

well our egt do get over 1700 degrees just with average driving let alone when you are getting in to the gas. when i get the new exhaust ill cut the old one open to see how bad it is burnt out. will talk pics

Rx-7Doctor

iTrader: (13)

Exhaust temps at full throttle on a Rotary can go as high as 2000 degrees Farenheit.

Thats why you don't put on "Cheesy" exhaust components. :-)

Anthrax Mike

You'd think that, that'd depend on the tuning. I wonder if the greater power created would offset the richness of the fuel mixture. You'd think that a car with EGR disabled, coupled with the naturally lean conditions during highway cruising might generate an even higher exhaust temp.

I found this crazy link

http://www.math.tu-cottbus.de/INSTIT...rs/rotory.html

some of the captions are in german, though the text is in english. Anyway, it has this bit where it says that a rotary engine will on average produce 2/3 the Nox of a conventional piston engine. Due to its elongated combustion chamber. And considering that Nox is formed under conditions of both high temperature and pressure, it would seem that somehow the pressure generated during combustion doesn't quite rival that of a piston engine. Obviously the run hotter, but I thought the combustion pressures weren't all that far off.

Any ideas smart people.

Wanktastic

I think the biggest difference between rotary and piston regarding NOx formation are the pressure curves inside the chamber... The rapid up-down motion of the piston lends to a dynamic compression that you may not get in the rotary (largely because of the 1/3 rotor speed). I remember reading an article somewhere a long time ago about an engine tuner who specialized on Hondas after a successful career tuning NASCAR motors. This person said that he could run rediculous static compression of 14:1 or more without blowing the engine because he tuned the combustion chamber to allow a much "softer", or gradual dynamic compression curve. Wish I could recall the guy's site...

Ah! http://www.theoldone.com/

Runs EnDyn... fascinating articles, even if they are for boingers.

Anthrax Mike

^

No this kind of stuff is worth the read.

Danke

BlackFireRX7

now where is the glowing header pic??

speedturn

iTrader: (1)

The combustion of fuel/air inside the rotary is not really any hotter than a piston motor; the reason the rotary has a hotter exhaust is because the rotary has to open up and dump the exhaust gasses before they are fully expanded. If held in longer like a piston motor does, the gasses begin to do negative work on the face of the rotor, and power is lost. So, the rotary exhaust port opens up sooner and dumps out the gasses while they are still much hotter. In a piston motor, the gasses are expanded further inside the motor, doing a little more work on the piston and crank. The old Pressure versus Temperature gas laws always hold true, so further expanded = lower pressure = lower temp relationship holds true, so the exhaust is cooler when it comes out of the piston motor. This is also the one basic reason why rotaries get worse gas mileage than a comparable power piston motor - the rotary has to open up and dump the exhuast before extracting the full amount of work out of it. Wasted energy is going out the exhaust port.

bugman1973

dont think about putting just any turbo muffler on because you will destroy it and i mean destroy. so speed the money buy something that will last

BlackFireRX7

on the other hand the rotary engine doesn't have to waste energy spinning a heavy rotating assly and it doesn't have to waste energy reversing the direction of some heavy *** pistons... what kinda fuel milage does an Rx8 get??

Joker1337

The 8's are getting 25-ish as I understand it. I believe that Mazda moved the exhaust ports on the irons a bit to help get a little more power and mileage from the engines.

BlackFireRX7

is that city or highway or an average??

my 12a gets 25 on the highway doing 80... on the other hand, the Renisis makes just a bit more power

bugman1973

lets not all go out and get Renisis engines for our first gens.

Joker1337

Has anyone done that? Dropped a Renesis into an FB? I mean, the layout's should be roughly the same, once you replaced the wiring, right? And 232 hp stock would give you a fair kick.

18 city, 25 highway by the way, if Mazda's EPA numbers are to be believed.

rotornoob

iTrader: (2)

i had the opportunity to test drive an 8 not too long ago and i must say that the renesis is beautiful. having one in my FB would be a cream dream. from what i understand its a whole **** load of work to do and there is an issue of some sort about the abs controlled speedo (?)

bugman1973

its has been done wouldnt suggest doing it. there are guys on here that have pics of some magazines with it on there.

dj55b

iTrader: (2)

From my understanding, they have moved the exhaust porting to the side on a renesis was for better emmisions reasons.

bugman1973

on what do you mean can you show pics i thought they were very close to what the 6 ports engines are on the 1st and second gen probably close to the later second gen na setups were

Jeff20B

iTrader: (13)

Can anyone read Japanese?