shelleys_man_06

About tertiary spark plugs? I don't see a point in adding extra spark plugs, especially on a street-driven rotary engine. If you recall, the R26B used three spark plugs per rotor chamber. I think the third was for cleaning things up, or something like that. Perhaps a real rotary guru could explain this further. With the extra spark, I wouldn't see a change in gas mileage improvement.

rotarygod

Who are you directing that at, me? I am fully aware that ram air will have no effect when not moving. Hell, it won't have any effect until you are moving really fast. It is ultimtely only a top speed enhancement.

rotarygod

If you think he's bad, my girlfriend goes to U of H where shelley's does and she just graduated with a bs in math. She is currently in Grad school there going for her Masters degree in math. You think Eugene (shelley's) has it bad!

shelleys_man_06

Oh. It was a response for Celronx. :o

globi

Well then why not take a large exhaust wheel (turbine) and combine it with an electric motor and we're all set.

Besides no matter what engine: A supercharger probably couldn't compete against a turbocharger regarding efficiency and even ultimate power anyway. It appears as if the additional backpressure is less harmful to the efficiency than the parasitic power loss of the supercharger. Otherwise superchargers on diesel engines would be more common or they would have used superchargers on Formula 1 cars (They were allowed to use any supercharged engines up to 1.5 l displacement since 1966 (+/-) but they didn't until Renault 1977 (+/-) figured out a way to control turbochargers which started the Turbo era and displaced the naturally aspirated 3.0 l engines).

Regarding air consumption: I thought about it again and still believe you should do the calculations with 2.6 l (for the RAM intake).
Assuming you'd use the Renesis as an air pump it would pump the same amount of air as a 2.6 l piston engine assuming both have the same volumetric efficiency. Now you can argue that the volumetric efficiency of the rotary engine is higher but this still wouldn't make it a 4.0 l engine nor would I believe that the volumetric efficiency of the rotary engine is over 100%.

Regarding efficiency: Another reason (besides bad surface to volume ratio etc.) why the rotary engine is less efficient is because the combustionable mixture is not evenly distributed due to the moving combustion chamber. It is lean at the leading edge and rich at the trailing edge and it might also be leaner closer to the rotor. Maybe some gasoline direct injection system could compensate that, but this would also require several nozzles.

rotarygod

I'm going to let you go try an intake sized for a 2.6 liter engine on your own car. Tell me what happens to your power. I already know.

Aoshi Shinomori

From what I've read, it can be said that it displaces 3.9 liters because it takes 3 rotations of the e-shaft for a full engine cycle, 1.3+1.3+.1.3=3.9. I may be wrong, but from what I've seen and read on this forum that's why it is at the 4 liter mark in terms of displacement.

globi

I just thought about it again: If the rotary engine was a simple air pump, each rotor would pump 1.962l (3*0.654l) per 3 revolutions. There are 2 rotors, so it would pump 3.924l per 3 revolutions. Now this is exactly the same volume a piston engine would pump with 2.616l displacement. (It would pump 2.616l per 2 revolutions which would be 3.924l per 3 revolutions). Assuming both have the same volumetric efficiency.
So it really doesn't make sense to me. If the volumetric efficiency of the rotary was far superior than that of a piston engine, then I would understand it. And maybe this indeed the case?

wakeech

if you mean an improvement in fuel efficiency, yeah you would. the super-trailing plug was incorperated to fire very shortly after the trailing plug to enhance the motor's ability to combust the charge at the trail end of the rotor which was subject to being cut off from the flame front (basically wasted potential power... but makes great fireballs). a squish-type volume emerges at the trail end of the combustion chamber at the start of the power stroke cycle once the rotor face depression passes the little bumpy thingy on the vertical side of the rotor housing. this symptom became very pronounced in the race motor as speeds approached redline (9k rpm), and was compounded by the biased shape of the combustion chamber (toward the leading side of the rotor, IIRC).


if you really pay attention to the math, all you're doing in 'changing' your theoretical displacement is changing the number of rotations of the e-shaft you constitute as being a complete cycle. there is way more 'controversy" over this than there should be. the way the the real world sees it:

a motor is defined as having completed an entire combustion cycle when all combustion chambers have had a combustion event (fired their spark plugs). in a 2 stroke motor, that means once up, once down (one rotation of the crank shaft). in a 4 stroke piston motor, that means twice up and twice down (two complete rotations of the crank shaft). in a '4 stroke' (otto cycle) wankel motor, that means 120 degrees of rotation for each rotor (one full rotation of the eccentric shaft).

being that each rotor in a 13B mazda wankel engine displaces at theoretical maximum 654cc's per 120 degrees of rotation, and it has 2 rotors, it is a 1.308 L engine. case closed, and one more reason no one should listen to idiots who write in car magazines who think they know what they're talking about (thinking of the SCC article).
when it comes to calculating rate of mass flow, you need is a rate (which is, yes dependant on displacement, but not solely), so all this bullshit about the 'real' displacement is pretty pointless, especially since it really is 1.3L.

...and ram air is still extremely useless (drag, the necessarily unattainable velocities, etc).

globi

wakeech, I don't really care how the engine is defined. I'm just trying to understand why you need to assume that it is a 3.9 liter piston engine when you're working on the throttle body or installing a compressor.

All engines 2 strokes, gas turbines, coal power plant equipped with a steam turbine and even a horse are essentially air pumps and if you were using the Renesis as an air pump it would pump as much as air as a 2.6l piston engine, IF the volumetric efficiency was the same. But maybe the volumetric efficiency of the rotary engine is much better?
But then again: If the rotary engine has such a great volumetric efficiency why wouldn't it be used as a supercharger?

And regarding the displacement definition: You're forgetting the important fact that a 2.6l 4 stroke piston engine also displaces 1.3l per one rotation of the shaft.

wakeech

the vE varies by rpm, engine type, and setup (a p-port motor will get smoked by a small 4 port below 4k rpm, and at +6k rpm the p-port will beat the ever livin' everything out of the small port).

as i said in my post the real concern is the rate you're moving air (by mass is the most correct), which is dependant on internal displacement (which is not separable from each engine's specific definition) but that doesn't tell you how fast, so rpm is also a factor, as is the pressure of the gas you're inducting. RG's assumption for a 4L motor has something to do with his funny math (applying 'piston motor' calculations to a wankel) and just that he likes to bend the rules of classifying engines (like saying that each rotor has to fire all 3 of its sides to constitute a complete cycle, which i disagree with as the whole cycle isn't different each time, and it doesn't matter how the rotor is oriented, it's just the same event x3 meaning that it's three times too long for a complete combustion cycle). not to mention he does love being a tease and at times is very vague.

there are superchargers which operate on the wankel design.

...and how am i forgetting anything?? it doesn't matter that it does the same in 1 what an otto cycle piston motor does in 2, that just means it's doing it twice as fast. it is, really, a 1.3L motor. when you go racing, does this mean that it often gets lumped into the 2.5 - 3.0L class?? sure, but in the real world engines aren't classified by internal displacement, they are what they are.

hotpot

If I divert the cold air output from the aircon into the airbox and put the blower on max, will I get a boost in hp?
Or is this really dumb?

RX8-TX

Wakeech, I was going to go after you a little harder in here....but, since I don't know my hand from my rear, I will just ask. What about the group in charge of the Iternational Engine of the Year? Why would they classify the Wankel in the 2.5-3L category?

"They are what they are" is not nearly a good explanation. There has got to be a yard stick by which to effectively and accurately measure and compare things in general. Is the thing -wankel- gets bumper to the 2.5~3L category, it has got to be for a reason -I doubt its an arbitrary decission.

globi

When you go racing you have to compare what volume is being displaced per number of rotation of the shaft, that's simply not more than fair. Otherwise according to your definition a 3.0l V6 for instance should really be in the 1.5l class.

Only 2 stroke engines displace as much volume as their classification indicates. I'm sorry but that's just the way it is.

globi

First of all the AC is powered by the engine as well as is the alternator which generates the electricity to run the fan, so when you turn on the AC you will lose power.
But let's assume the AC and the fan was run by the battery at WOT. The engine consumes about nearly 200l of fresh air per second at 9000 rpm and your AC does not pump that much air by far not to mention increase the pressure. It might slightly increase the air density but that won't be noticable at all. However I guess it's a creative thought.

wakeech

there was talk about this ebfore in some other thread... i think the Ford Lightning does this?? *don't really know*
the thing is that it's not efficient, you're spending more energy to pull the heat from the air than you'll get burning a slightly denser air charge.

guys, about the internal displacement thing, i don't realize where the disagreement is. it's a 1.3L motor, but yes they throw it in with the 2.5-3.0L motors just like in bikes how the 250's compete with the 500's.

wvrx8

is the s/r a true ram air kit i do not know much about cars and looking for extra power at a low cost any HELP would be great and it sounds as if rg can help THANKS

rotarygod

Nope. Racing Beat's new duct for their REVi kit which has not been released yet will be about the closest thing to it.

Lock & Load

Wow my head is rammed with all this info

cheers
michael

xabjw4

Mine too, but the math is the math. RG has it right.
Great, Jeff B.

crossbow

Ram air, ram air, ram air, ram air, ram air, ram air, ram air, ram air, myth, myth, myth, myth, myth, myth.

I post a link to this thread almost weekly on 6club, and am tired of trying to figure out what to search for.



Thanks again for the thread RG.

rotarygod

I actually need to go back and update this a bit as I left some things out.

Asmoran

So if the ram air benefits are only attainable at high speeds, how do people with the RB ram air duct get better mileage? Is the mileage benefit only occuring as they cruise down the interstate @ low rpms, and while driving around town it doesn't really do any good (other than the sound, of course :D)?

rotarygod

That's one of the topics that I need to go back and add in.

kw1k

I still rather get the AEM CAI. oh wait i did