Piston eng. vs Rotary eng.

[MAZDA1807]

Hello everyone.  I run a Mazda RX7 with a rotary engine and have found it very uncompetitive against the piston engines in the E class range where I run.  Last season I sent in a rule change to fix this problem, it was passed both by the committee and by the board, but then revoked.  ED=SV x 3 is what the rule book states, SV: swept volume, ED: equivalent displacement.  The 13b is the engine I run, witch is 80Cid accordingly to Mazda, but with the formula it is 240Cid.  I had it changed to ED=SV x 2, based on the thermodynamic cycle theory, before it was changed back. 

                                                       TELL ME WHAT YOU THINK
                                                          PISTONS vs ROTORS 

[Cole222]

I have had three RX7's that were all fun cars to drive. I did learn that anytime they are put against a piston engine in compatitiion the rules would favor the pistons. It is a compact, high reving engine that when put on par by displacement typically outperforms by wide margins. Advantage Pistons. This is not likely to change in our lifetime. 
Cole

[MAZDA1807]

It is a very complex engine, over 200 moving parts witch are mostly springs and seals, that's why I belive no one understands how it works.

[MAZDA1807]

Here's what I mean by moving parts

[Stainless1]

HUMMMMM 
 

[MAZDA1807]

That's only the rotors.  Most rotarys are twin, but there is the occasional triple!!

[maguromic]

Maybe Rex will chime in on this with his Mazda IMSA experience.

[MAZDA1807]

I believe the rotary engine is compareable to a 2.6-2.7L engine.  At Bonneville in '08, I actually had a chance to have the engine pumped out of curiosity.  It pumped out to 162Cid. or 2.65L.

[MAZDA1807]

I believe the rotary engine is compareable to a 2.6-2.7L engine.  At Bonneville in '08, I actually had a chance to have the engine pumped out of curiosity.  It pumped out to 162Cid. or 2.65L.

Just to make it clear, that was to the current formula: ED=SV x 3, ED=162. The swept volume of one side of the rotor was 27Cid.  So take that & times it by three sides, then times by two rotors and, WA-LA!! 162Cid rotary.

[McRat]

I believe the rotary engine is compareable to a 2.6-2.7L engine.  At Bonneville in '08, I actually had a chance to have the engine pumped out of curiosity.  It pumped out to 162Cid. or 2.65L.

Just to make it clear, that was to the current formula: ED=SV x 3, ED=162. The swept volume of one side of the rotor was 27Cid.  So take that & times it by three sides, then times by two rotors and, WA-LA!! 162Cid rotary.

But it's effectively a two stroke, right?  A 162ci inline 4 displaces 81ci per rev.

[MAZDA1807]

McRAT, the rotary I suppose you could compare it to a 2-stroke because it uses its own oil to lube the top end. It has four strokes, but no pistons or rods.  This engine acctully has a thermo-cycle of 1080deg. of rotation for a full burn.  Otherwise the rotor turns at 1/3 speed.          Peter.

[dwarner]

"Otherwise the rotor turns at 1/3 speed."

Would that be why the x3?

DW

[MAZDA1807]

Dan, it takes the rotor 1080 degrees of rotation to go from point "a" to point "a".  In that case a smallblock 350 should be x1.5, because it takes the piston 720 degrees to make a full burn.

[MAZDA1807]

Dan, it takes the rotor 1080 degrees of rotation to go from point "a" to point "a".  In that case a smallblock 350 should be x1.5, because it takes the piston 720 degrees to make a full burn.

I ment to say x2.0 (way too many numbers today).

[MAZDA1807]

Maybe I should barrow this engine from Mazda, the 26B, 4 rotor.  This would put me in A/GT, 80Cid x 2 x 3 = 480Cid. 
Check this engine out.http://www.youtube.com/watch?v=9675TKafw3g
That engine has titanium rotors compared to the cast iron one that everyone runs.  That's comparing 2-3lbs. to 9-10lbs. of rotating mass per rotor.