Cool_ManX

yeah

Aviator 902S

I checked the above site because those numbers just don't add up. What I found was that a) the site is based in Australia (the only country using U.S. gallons for purposes other than small aircraft use is the U.S.), and b) I didn't see anywhere on this site where it specified U.S. gallons.

So I looked up the proper multiplier and found that one liter = 0.22 Imperial gallons. Since 9 liters per 100km = 11.111 km per liter, and it takes 4.5454 liters to make one Imp. gallon, this means that 9L/ 100km = 50 km/ Imp. gallon. Since 1 km is about 5/8ths of a mile, this works out to 31.5 miles per Imperial gallon.

One U.S. gallon = 0.8327 Imperial gallons. 31.5 X 0.8327 = 26.2 miles per U.S. gallon--- a little better than my original estimate of 25m/ U.S. gallon.

Amur_

Well, that's no good at all.

Adam

im glad the aviator knows what hes talkin about. (math wiz)

Aviator 902S

LOL... Thanks Adam, but "math wiz" is a bit of a stretch. (I wish I was one--- it would make certain aspects of my chosen profession way easier ). I usually arrive at the correct answer, but it takes longer for me to figure it out than it does for the average person.

T2monster

not to mention given horsepower output per displacement. We rotary enthusiasts have some of the highest hp/liter of the IC engine world.

T2monster

more power will always mean more fuel.

Valkyrie

I wonder why no one has made a turbine-powered F1 car yet.

Aviator 902S

High HP per displacement certainly provides a degree af bragging rights, but low displacement doesn't provide good fuel economy unless the power output is also low.

Example: a 1300cc 4-banger in a typical 1970s era Japanese car returns about 40mpg, but only produces about 70hp. The same displacement engine in a Formula 1 race car puts out many hundreds of hp, but only gets about 2mpg. So much for the benefit of low displacement.

In the real world it's power-to-weight ratio that matters most, and here's where the rotary really shines. In aircraft or racing boat applications the rotary is capable of the same hp output as a V8 or larger displacement V6. But being lighter it will leave V6 and V8-powered planes and boats standing still because of a) the extra air load required to compensate for the extra weight of the piston-powered plane to keep it up there, and b) the fact that the heavier the boat is, the lower it sits in the water and the more hp required to overcome the viscous drag of the water.

This is not so critical in cars, especially if weight and balance problems caused by the V8 can be somewhat corrected by removing unnecessary components and placing other components in different locations.

BLK90TII

Can some one give me some insight on this guys question? I was kind of wondering the same thing.

Really what I know is how the engine design could be made more efficient in the combustion chamber area.

Aviator 902S

What the racing community does (and I'm not certain, but Mazda may have made this change on the Renesis engine as well) is to cut small grooves in the coolant passages in the vicinity of the spark plugs. This is the hottest part of the engine. The grooves cause the coolant to go turbulent in this area and also provide more aluminum surface area in contact with the coolant, resulting in better heat dissipation.

As for the surface area of the combustion chamber being too large and having a negative effect on fuel consumption, the only remedy I can think of here would be to use a wider rotor and housing along with a third plug placed beside the primary plug. While a wider chamber would cause actual surface area to increase rather than decrease, the hp potential and more complete fuel burning would provide a net decrease in fuel burn per hp produced. This is because with wider rotors the combustion chamber would be more square than rectangular.

That's my theory anyway, but until Mazda or somebody actually tries this using current technology we'll never know for sure...

rs_1101

im sure somewhere along the line mazda has tried all of these solutions. why do you think that theres a pit in your rotor? thats to decrease the total surface area, b/c to acheive the same displacement they would in fact have to make the rotor wider.

the only real way that you could increase efficiency is to increase the motors capability to withstand heat. this calls not to increase heat dissipation, but to actually make the motor run physically hotter. that way (as i see it) less heat will actually be dissipated per amount of energy..

of course.. the heat from our motors is a byproduct of this lack of efficency.

Valkyrie

So it has the right compression ratio.

NorCal90

So, this is a little off topic but still related, how would one get better milage? Would adding a S-AFC and a more powerful spark help that out? Will the S-AFC hurt emmisions? Personally, I'm getting aroung 16-17 in mixed driving which is so wonderful to me. My previous vehicle was a 90 Bronco that got maybe 10 mpg on the freeway and that's prolly wistful thinking.

Valkyrie

S-AFC's only control the fuel flow when you're WOT...apparently.

So, no.

patman

iTrader: (3)

One thing that is being overlooked here is the development potential of the rotary. Boingers have had massively more research and development on refinement, and IMHO are pretty much at the pinnacle of their efficiency..there isnt much left to do. THe simple fact is that a full reciprocating motion is inherently very inefficient, and in basic design, the semi- reciprocating rotary is much better.

While a lot of the same techniques carry over to rotaries, many dont. With the same amount of research, it should be possible to get much more efficiency out of a rotary. Different configurations, or general engine shapes could prove key to making them work much better. The moller rotary, for example, is supposed to be extremely more efficient than a 13B.

As far as current designs, you guys are all arguing over nothing. Aviator is entirely correct, BSFC (brake specific fuel consumption) is an exact and accepted measure of efficiency, and the numbers for a 13B vs a boinger are very close. All he is trying to say is that it is not a drastic difference, he isnt saying that it doesnt exist.

Of course the reason rotaries have a slightly higher BSFC is due to thermodynamic efficency in the engine. more surface area= less efficient. A change in shape could help with this some, as could ceramic coatings. see www.jhbperformance.com

as for tuning...it really isnt an issue...it applies equally to any type of engine. Rotaries do not have any inherent need to run richer than boingers, mazda just tuned them that way for reliability... back to the same thing...the design isnt refined enough to allow tuning right to the point of max efficiency.

Pat

Aviator 902S

Hey Patman, thanks for the vote of confidence.

Yeah, that's another point most if not all of us didn't bother to mention. The boinger had a 60-year head start on development over the rotary, and with no alternatives at the time nobody gave up on pistons. As for rotaries, Mazda was the only major manufacturer to take the ball and run with it. The results of course were spectacular, but who knows how far development of this engine would be if all others had given Mazda some real competition?

The Moller Sky Car rotary development sounds good, but less certain is if we'll ever see these engines available to the mass market for a decent price. Moller keeps saying all the right things and taking deposits but many of us in the aviation community have taken an "I'll believe it when I see it" stance. Here's hoping...

patman

iTrader: (3)

moller has a child company for their rotary engines now...looks pretty promising.

IIRC its www.freedom-motors.com

pat

Valkyrie

That guy is f'cking obsessed with his little project.

Apparently it's cost him 40 years, 2 marriages, and tens of millions of dollars so far.

And that it's still not a viable form of transportation yet.

Aviator 902S

Sounds believable, but I don't believe he's invested tens of millions of HIS OWN money. At least not yet. But he's still taking deposits so don't delay! Get your order in now and be the envy of your entire state....

NAVDREG

[B]I get about 9-11 MPG and I suppose that is because my car is a convertible and they are generally Heavier cars.

patman

iTrader: (3)

umm...no. there is something wrong with your car. 9-11 is waaay low for unmodded non-turbo.

Aviator 902S

Either that or you're spending 90% of your driving time in gridlock...

GUITARJUNKIE28

even if you're raping it, you should be getting more than 15

Amur_

http://www.fueleconomy.gov/feg/bymod...zda_RX-7.shtml


Although there isn't a separate listing for the vert, there's no way in hell it would be getting half the mileage of its counterparts. You've got some troubleshooting to do, guy.