"rotaries have a high surface area to combustion chamber volume ratio, making it less likely to knock than a piston engine"

that sounds bass-ackwards.

the surface area in relation to the combustion chamber volume is high. This makes it less likely to detonate. I never said rotaries don't have more severe consequences when they knock, and i never said rotaries aren't more likely to fail when knocking, i just said that they are less likely to knock.

read the book: rotary engine by Yamamoto, and read some of the tech articles at this website of a rotary manufacturer. www.freedom-motors.com

Rotary Advantages:

Somewhat self sealing at high rpm. If it will build enough pressure to start, it will make very close to original power at high rpm. No need to start rebuilding because your leak down test is down 5%.......

Over-rev capability! The occaisonal grab for 4th gear may result in engaging 2nd gear. Doesn't matter how many rev limiters you have, you just hit 13,000 rpm if the drivetrain didn't grenade. Seems to be pretty fatal to piston engines. Doesn't seem to hurt much on a rotary. Plus, you get to show off the tell-tale tach wrapped 1/2 way around past 9,000 in the pits!

Over rev capability part two: You fall a bit behind in a corner and need a good run down the straight to stay in front. Move your shift point up a bit. (We don't all have perfect trans ratios...) If you need that extra little oomph out of the last corner up to the start line for an extra 0.1 secs off your qualifying time, just don't shift until after the timing stand. Not many piston guys driving big buck pro built motors are going to run the motor out 1,000 rpm past the motor builders recommendations.

Lack of valves make for very strong wave tuning potential.

And finally: No piston motor ever built can have it's hp doubled with a die grinder.

No rotary engine can either, show me ONE completely bone stock rx7 NA or TII with stock everything (boost levels, cats, headers, tune etc. etc.) with only a port job that doubled it's hp.

Yeah, but in general, no valvetrain is a big plus for the rotary. The valvetrain is usually the casualty on a piston engine over-rev, and not having to buy cams, valves, springs, and worrying about guides and valve seals is nice, too.

EDIT: oh yeah, not to mention rod stretch, parasitic drag from reciprocating motion, piston-to-valve interference, etc. All those things aren't an issue with a rotary.

O.K. See attachment.

84 12A with big street port, Nikki with large Primary Venturi (done with lathe, but die grinder would work in a pinch. Same for the jets, a small drill bit or really small die grinder will do.....) The exhaust manifold is stock, and while the 2.25" single pipe isn't stock, taking the guts out of a converter and the baffling out of the stock muffler would get you in the neighborhood. The flywheel is stock, and all the internals are stock, unbalanced, and unlightened. Although you could use a die grinder to lighten And balance it if you desired.

While I find it hard to believe you would want to claim that the manufacturers claimed 104 flywheel hp would equal more than 90 rear wheel hp, realize that the drop in power is where it ran out of fuel. That motor later tightened a bearing up at 11,000 rpm when the fuel situation was corrected. It kept making power until it blew up. And no, it wasn't a stock fuel pump, but the fuel lines were.......

In short, this was a dyno mule made out of junk stock parts that no one in their right mind would have used to build a motor that they wanted to last. Apply die grinder, test theory, then try again.

If this is a problem with a piston engine, it's not one that's doing very well in any race.

great info here! Honestly, I had just about given up this site as a bunch of flamers until I found this thread. It's nice to be able to find a piston vs rotor thread with no flaming. :beerchug: