E=MC2????

[dick elliott]

Simple question! Since there are only three (3) sizes of Mazda rotary engines available to the average racer, (12a-13b-20?), why doesn't the rule book state what class these engines fit in. E=MC2 is great if your smart enough to work it out. I don't need a study in math, I just want to know where a rotary fits. You know (A-B-C-D-etc-etc) Thanks for any and all answers.

[jim32]

Seams like a fair question due to the fact that it is a current production engine. I would suggest that rotary engines have there own engine category such as the flat heads and other vintage types. This would make engine size easier to define and keep us out of the Factoring business as some feel the rotary design can not be compared to a piston engine based on displacement or sweep volume alone.[/list][/list]

[dwarner]

BTW, NHRA and other sanctioning bodies do think that swept volumn can be compared to cubic inch displacemnet.

DW

[dwarner]

Whoops  

The post before my last one didn't make the forum.

What I posted was that I am modifing the rule book next year to cut down on the number of pages. It will be a simple thing to add the rotory engine sizes to section 2, Send me the sweep volumn of each of the Mazda engine types, i.e. 12A = 35ci? and I can put that in.

Now read my BTW post and it will make sense

DW

[dick elliott]

Big problem here, is NHRA/SCCA/NASA have all based their classification many years ago, in relation to piston engines of that time frame. Well quess what! Piston engines have gone far ahead of where this classification was based upon, but the Rotary is still a Rotary and will always be a Rotary. If a flat head 4-6-8 can have its own class, why not a Rotary? Ever wonder why so few show up on the salt? Hell! One can't even find them in the rule book. My two cents worth.

Seams like a fair question due to the fact that it is a current production engine. I would suggest that rotary engines have there own engine category such as the flat heads and other vintage types. This would make engine size easier to define and keep us out of the Factoring business as some feel the rotary design can not be compared to a piston engine based on displacement or sweep volume alone.[/list][/list]

[dick elliott]

All I want to know is what class (engine size) does a rotary run in? Some one must have raced one on the salt since 1979. Did he/she just pick a class and race or? I can tell you SCCA shows a 12A at 2200 or so cc's and a 13B at 2600 or so cc's. SCCA's rule book is on the internet for the correct numbers if you need them. And don't worry, no body with a Rotary will show up with a stroker or .060 over bore. What ever size you give them is all they will ever have. More of my two cents.

Whoops  

The post before my last one didn't make the forum.

What I posted was that I am modifing the rule book next year to cut down on the number of pages. It will be a simple thing to add the rotory engine sizes to section 2, Send me the sweep volumn of each of the Mazda engine types, i.e. 12A = 35ci? and I can put that in.

Now read my BTW post and it will make sense

DW

[dick elliott]

My last two cents. 12A is 2292 cc's and 13B is 2616 cc's. How SCCA came up with this number is ? These #'s are out of the 2006 rule book on the internet. Hope this helps.

[dwarner]

2005 rule book

Page 88    F/M/MP   146.356 8/04
Page 90    E/BGT    238.442 8/86
Page 90    E/GT      183.904 8/78
Page 126  F/FS       186.220 10/98
Page 145  F/GMS    158.566 9/94
Page 145  F/M/MP   135.478 7/04
Page 149  F/GT       158.950 11/95

If the rotary is so out classed with the current formula why haven't these records been beaten? These records range from 1-27 years standing. The current piston engines which compete in the E/F classes certaintly have the technology to eclipse a record.

DW

[jim32]

Thanks Dan, you cleared up a lot of things for me and your purposed change for next years rule book will be a big help to those of us who don't work with the records every day, we don't know that these records were set by rotary engines. thanks

[dick elliott]

Since you only show two(2) engine sizes, (E and F), does this mean that a 12A runs in F and a 13B runs in E? If this is correct, please state so, so I can get on with this project. Thank you very much for putting up with an old mans lack of understanding of your engine classification. Yes rotarys are fast in each class. Hope to be one of them now that the rules are clear. Thanks again. DICK

[LittleLiner]

After owing a Mazda RX-7 roadster for about 4 years (now sorry I ever sold it) I really got to like the little rotary engine.

If you want a pretty good rundown on all the Mazda rotary engine incarnations I suggest you checkout the Renesis web site.  http://www.transporteon.com/Superlatives-R/Renesis.php

The most common engines are the 12 and the 13.   The 12 has a swept volume of 1146cc and the 13 has a swept volume of 1308cc (some references say 1310cc)

The SCTA factor is 3 to get the factored displacement for engine class.
 (1146cc x 3 = 3438cc) which is near the lower middle of the E class.
 (1308cc x 3 = 3924cc) which is near the top of the E class.

Mazda had an earlier version (1974 and earlier) called the 10 which had about 982cc.
 (982cc x 3 = 2946cc) which is right at the top of the F class.

One of these posts mentions that different sanctioning groups have different factors for rotaries.  Actually that makes some sense when you consider that they are trying to equate performance in vastly different situations.  I don't know what factor would be fair but for sure one size does not fit all when comparing road racing, drag racing and LSR.

An example of such a difference is that ECTA factors rotaries at 2.3 rather than 3.0.  I am not sure what the rationale was but for sure the different venue had something to do with it. A Mazda 12 or 13 would be in the F class at Maxton.  ECTA also has separate rotary classes for rotary motorcycles but not for cars.

FIA lists separate classes for Rotary records.  I haven't heard of any other group that has separate classes just for rotaries in cars.

[dwarner]

The records I mentioned in an earlier post are slightly in error. I spoke to Steve Shotrosky who owns most of the records. I found out from Steve that only the E reocrds were set with his rotary. The F class records were done with a water cooled V6 Mazda piston engine.

Sorry for the misleading post.

DW

[Rex Schimmer]

I am a big fan of the rotary as I was involved with 3 different race teams back in the early 80s that raced them in the IMSA GTU class. At that time there was a big protest by the recip guys that the rotary had an unfair advantage and made more hp than the 2.5 liter Datsuns and Porsches. Well I can tell you I spent many hours on making special parts and testing on the dyno and we never made more than 305 hp on a 12A with periferal ports. This was done with an engine that we built just for development work and it was built using "race tested" parts, ie. OLD. and used a mechanical fuel injection system that had a pair of 50mm slide valve throttles and a Kugelfisher injector from a BMW 4 cylinder race car. We tried lots of things, including 2 stroke style expansion chambers and every kind of port configuration you could think of and found that the standard Mazda race parts were the best. The engine like to be well broken in as they got more hours they ran better. We also found out that they liked to run lots of oil temp. Running the oil at 275 deg f was good for about 10-15 hp over running at 175 F. We never saw much more than 160-165 ft-lb of torque, we got 175 ft-lb once by making the injector stacks about 15 inches long. This got us thinking about making the intake lenght variable but the development money was gone by then. Mazda did this with their GTP cars.

The rotary had two real advantages in my mind, 1. They were "anvil" reliable. We would run 24 hour races with a 9500 rpm limit and 12 hour races at 10,000 and sprint races at anything it would take to win! 2. The rotary has a very low moment of inertia for the rotating parts, which means that they rev really fast. Add a two plate 6 inch dia clutch and a spidered flywheel and a good gear box and they would beat anything out of a corner.

If SCTA would go to a 2 times factor instead of the present 3 times sweep volume factor I would build my future lakester with a rotary in a heart beat! You can rebuild one in a couple of hours and again you just about can't break them.

Rex

[StraightSix]

Agreed with everything Rex said.

For completeness' sake, the 20B is 3/2 of a 13B, and thus in C class.

[Glen]

They are to loud and give the starter a head ache.