Originally Posted by guyhatesmycar
Wrong...gasoline is far more volatile than diesel. Go get a gallon of diesel and pour it on your driveway and then take a match to it. It won't burn.
The correct answer is: Gasoline cannot be used in a compression like a diesel because it is too volatile. The combustion of it cannot be easily controlled at high compression ratios.
i know this has been threadjacked and now we're talking about diesel and diesel engines, but aren't rotaries considered 2-stroke?
No.
They have intake, compression, power, and exhaust stages.
The thing that makes them more efficient vis a vis displacement is that the rotor can have multiple stages going on in different parts of the rotor.
The reason I brought up the diesel thing is that since in a diesel engine the injector sprays directly into the cylinder, that is a way you can efficiently use the 2 stroke cycle without any fuel going out the exhaust. That of course led into me wondering why you can't have a compression ignition gasoline engine. I still totally believe it is possible, and that it comes down to injector design almost 100%. But no, you wouldn't need compression ignition to have a 2 stroke gasoline engine. You would just need a supercharger.
..I thought volatility was a measure of a liquid's properties of evaporation, not combustibilty..time to go look in a chemistry book, I guess..
Wow, haven't been back in a while. Certainly some interesting reading...
Great Dane, can you elaborate? Btw, nice car!
hell, makes me wonder about the rotery engine , we all know the TQ rating is shit but high HP gains are easy, only reason that i like this engine (from an enginnering standpoint and engine rebuilder) is that there is no valve train at all , its mostly the degree angle and other characteristics of the ports on the engine that act liek valves, thus a light weight engine with fewer moving parts, now only of they could fix the TQ problem and make the engine run better on gas cuz sometimes thos roterys are pigs on gas
1989 Accord Lx-i hatchback (current DD project)
1986 Olds Cutlass 442 clone (never ending project)
3Geez resident body man
Owner of Wreck-less auto body
How do you seal the rotors without burning oil? I don't get it. And the rx-7 engine only lasts about 80k before it needs a rebuild..but better oiling/materials/construction will probably be applied to rotaries of the future. How is the engine in the rx-8, other than not turbo?
..the rx-8 is the gayest looking pseudo sports car I can think of, next to the eclipse after like 99 or whatever. Ugh, imagine if the rx-8 and the new eclipse had gay buttsex and produced an offspring..man, that would be a Gay looking car!
..whoa, sorry there for the hation..
Last edited by Accordtheory; 12-30-2005 at 05:22 PM.
excuse me? i never indicated that diesel was more "volatile" than gas.
go read the post again.
The diesel detonates when it is injected at or near tdc of the power stroke. this is TIMED DIRECT INJECTION. diesel engines can't "pre-ignite" because of high compression or boost levels because the fuel isn't even in the cylinder yet, as soon as it is, it detonates. its supposed to. go look up "diesel engine principles of operation". it will all make sense. Spark event? diesel engines do not have spark plugs. some have glow plugs, but they are not required.
....also, ever heard a gas engine "diesel" after you shut it off? My chev did it constantly. if the ignition is shut off and it's still running but sounds like a 6.2L diesel than it must be detonating....
The argument that gasoline is "too volatile and it's combustion cannot be controlled at high compression ratios" makes no sense. it WILL detonate. however diesel will detonate more easily, despite being LESS volatile. Volatility refers to how a substance evaporates, or produces fumes, having nothing to do with detonation. Gasoline is made really to not detonate, so why use it?
I'm not making this shit up. go read a friggen book on it if you don't believe me.
Last edited by Ichiban; 12-31-2005 at 07:44 PM.
ICHIBAN!
"Now, even more better!"
[QUOTE=Accordtheory]How do you seal the rotors without burning oil? I don't get it. And the rx-7 engine only lasts about 80k before it needs a rebuild..but better oiling/materials/construction will probably be applied to rotaries of the future. How is the engine in the rx-8, other than not turbo?
..the rx-8 is the gayest looking pseudo sports car I can think of, next to the eclipse after like 99 or whatever. Ugh, imagine if the rx-8 and the new eclipse had gay buttsex and produced an offspring..man, that would be a Gay looking car!
..whoa, sorry there for the hation..[/QUOTE
wankels do inject a small quantity of oil to lubricate the apex seals, otherwise you would cut right through the nikasil coating, thats why its in the owner manual of the mazda/eunos cosmo to top up the engine oil level.
but the rotary engine can last well past 100K miles if you take care of it, Ive seen a 1g RX7 with its 12A engine clock past 200,000 kms and still it fires up on first start and runs like new.
The rotor uses "apex seals" at the corners. Indeed oil control can be a problem on worn engines. The rotary is also designed to burn a small amount of oil to keep the apex seals lubricated and pliant, thereby mandating the use of conventional and not synthetic oils. Some racers who want to use synoil will hook up an external tank to the rotor oil injectors and fill the tank with conventional or even 2 stroke oil.
As for it needing rebuilds after 80K...not true. One caveat being, the rotary is ill suited for short trip operation. OTOH, it can be better than a reciprocating engine for sustained high speed operations because everything is going the same direction all the time, not unlike a turbine. There are some sites detailing the use of rotary engines in small aircraft, and they are run at 5000+ RPM for hours at a time using a reduction gearbox. They are well suited for this sort of operation.
If you ever drive a rotary, one thing you will notice how smooth the engine is at high RPM. I had a friend in high school who raced RX-3's and RX-7's, and the engines were smooth as a baby's butt at 8000+ RPM's.
As to why it is ill suited for short trip operations...Even in the fuel injected versions, it is possible to flood the engine if you turn it off too soon after a cold start. Once a rotary engine is flooded, you are in a world of hurt. Unlike a standard reciprocating engine, it is not merely a matter of supplying the engine a leaner fuel mixture until it starts. The process goes like this: if the engine is turned off shortly after a cold start, the engine will be running rich which will cause the apex seals to become wet with fuel, reducing their effectiveness to seal the different stages (intake, compression, power, exhaust). A rich mixture will be reintroduced on a subsequent restart. If starting is hard and enough extra fuel goes into the chamber, it is *possible* that the apex seals can get wet enough with gas that effective compression is no longer possible, rendering the engine flooded. In this extreme example, the only fix to get the engine running again is to remove the spark plugs, squirt a few ounces of oil into the chamber, and then crank it over again. If it doesn't start within 15-20 seconds, repeat. Keep this routine until it does start. (PITA, I know...)
Some reading on this here: http://www.rx7.com/techarticles_unfloodFC.html
People mostly experience these sorts of problems when moving the vehicle. For example, they will start the engine cold, move it out of the driveway, and then turn it back off. They go back later, or the next day, to a no-start condition. To avoid these sorts of problems, it is recommended to always run the rotary engine to full operating temperatures after a cold start. This is actually detailed in the owner's manual of Mazda rotaries. One method around this is to run the engine at 3000 RPM for 10 seconds before turning it off. Another procedure I found is here: http://www.rx7.com/techarticles_floodprev.html
You may ask yourself, why bother with all this rotary crap? Well, the engine can be very rewarding in it's smooth and powerful operation. It's not a good engine for people who are not particularly attentive to vehicle ownership, however.
Last edited by Brons2; 01-01-2006 at 11:40 PM.
way off topic but i got a wr450 this year and sh!t i never want to set foot on a 2-smoker again. the thing is a rocket.
Accordtheory, i think i finally see your point with the direct injection 2 stroke gasoline engine. you want to use a supercharged setup with forced induction and an oil-lubricated bottom end (a la detroit diesel) instead of an oilburning or oil-injected crankcase induction system (a la chainsaw).
before those of you out there decide to correct me, ask and i can describe in great detail how each system functions, as well as how and why different fuels do what they do.
ICHIBAN!
"Now, even more better!"
the japanese have 2 stroke cars usually about 490 cc which fits their insurance bracket that is why our 3g's are not 2.0 liters but rather 1955? it falls short of 2000 cc so it is in a cheaper insurance/registry bracket, the 2 strokers are small as in cvcc small.
got pics just need a scanner of cars in jap junkyard circa 1986!
pic's of project at my homepage: home.earthlink.net/~andyk65
HA SAW it again!!
sorry guys but what is PITA? please pretty please!
pic's of project at my homepage: home.earthlink.net/~andyk65
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