mlx8

Ran a search on "volumetric efficiency" ~ too many hits/threads to try to plow through to see if this has been posted before, but .... in case is hasn't, and for those who've any interest in stuff like this, I came across the following link while searching for some information on rotary's stuffed into Caterham / Lostus 7's

It's some one name "Miguel P" and, at least to me, seems very well written, researched and full of rotary data, so I'd thought I'd share the link:

http://ezinearticles.com/?Volumetric...ained&id=47639

for those interested. Hard to believe the author, Miguel P, wouldn't be on this site under one pseudonym or another.

If it's already been posted before, maybe one of the moderators can delete this, or provide the internal link to the thread on the Rx8Club site. 94% VE that's a pretty high number.

Still searching for more information on rotary powered light weight Caterham's or their ilk.

Happy New Year to everyone

chetrickerman

that is a very good write up, but according to everyone on here, rotary engines arent more efficient than pistion engines

MazdaManiac

iTrader: (3)

That's not quite right.
Rotaries have a lower BSFC than piston motors because they are thermally inefficient.
However, their volumetric efficiency is quite high because of the relatively large ports.

I didn't get too far into that write-up (I'll do it later), but the Ve for the Renesis was already computed using actual MAF values by Hymee or one of the other Aussies, so its merely academic at this point.

NgoRX8

iTrader: (1)

haha, i actually was looking through that page yesterday as well. what a coincidence.

chetrickerman

oh. what is BSFC again? how can you change the thermal efficiency?

MazdaManiac

iTrader: (3)

Brake Specific Fuel Consumption. Most piston engines are in the 60% range. Rotaries are around 50%.

You can't. Not directly, anyway. Its inherent in the design because of the shape of the combustion chambers, amongst other things.

chetrickerman

thats what they said. but rotaries have a higher VE than piston engines? why would the port sizes make a difference in the efficiency? i thought it would be the combustion chambers.

what about insulating the chambers more?

PhillipM

Because the large ports allow a large amount of mixture in for the size of the chamber, but because of the shape of the chamber and other problems with the rotary it doesn't extract as much of the power available from that mixture as a piston engine could.

MazdaManiac

iTrader: (3)

More air in.


Insulting them from what? Themselves?
Its inherent to the moving combustion chamber of the rotary that work is wasted.

PhillipM

You could possible help with thick ceramic coatings but whether that is both practical or viable is another matter.

MazdaManiac

iTrader: (3)

That would only address heat lost through the coolant jacket (can't really be done anyway - apex seals will want to see SIP, not ceramic.
Much of the loss is the movement/shape-shift of the combustion chamber itself.

chetrickerman

got it. im just throwing ideas out there

BlackBird05

Here's a heavy read on some attempts to use ceramic inside the rotary engine:
http://www.rotaryeng.net/Adiabatic-rotary.pdf

I think if you were to use ceramic plates and bolt them onto the side housings, that could be more viable than a thick ceramic coating.

ShellDude

iTrader: (12)

Hello!