Landracing Forum
Misc Forums => LSR General Chat => Topic started by: MAZDA1807 on February 10, 2009, 11:09:14 PM
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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
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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. :cheers:
Cole
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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.
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Here's what I mean by moving parts
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HUMMMMM :roll:
:cheers:
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That's only the rotors. Most rotarys are twin, but there is the occasional triple!!
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Maybe Rex will chime in on this with his Mazda IMSA experience.
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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.
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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.
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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.
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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.
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"Otherwise the rotor turns at 1/3 speed."
Would that be why the x3?
DW
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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.
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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).
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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 (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.
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I think the record in A/GT is around 253 MPH or so. :-o
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It might get the record. It has over 670HP.
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That's a lot of power. You might be able to get it with that. :cheers:
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My car might fly at those speed. I don't Know, guess I'll have to find out.
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Just put somemore weight in it. :-D
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The Mazda already has almost 1000lbs of weight in it. I supose it could take some more.
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The Kugel's Firebird weighed a little over 5000 lbs. :-o
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Thats heavy, my car only weighs 3600-3900lbs now. I don't know if i have the room for that extra weight.
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That's pretty heavy too, and if it handles well I wouldn't change a thing. :cheers:
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The car handles pretty good depending on the tire/rim ste up on the rear.
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Is there any logic behind why there would be a multiplication factor for rotarys, and not two stroke piston engines?
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This subject has really been beaten to death in the past. Maybe you can still find it in the archives.
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Is there any logic behind why there would be a multiplication factor for rotarys, and not two stroke piston engines?
The SCTA I believe was following NHRA witch did the same at the time era. Now NHRA has no restriction for the engine, it must run in the bracket class. SCCA still multiplies the engine, only by 2, as well as FIA, witch is only 1.5.
Peter
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Is there any logic behind why there would be a multiplication factor for rotarys, and not two stroke piston engines?
Nope.
It was a matter of protecting what was already established by restricting the new and unknown. Imagine you're on the SCTA board back when the rotary motor started to make its presence. Word on the street is this little motor makes hellacious power and spins to 11,000 rpm with only 60 cid. Man oh man that's going to put a world of hurt on the old pushrod/connecting rod guys. So what did they do? They looked at it, realized it had a three sided rotor, and said "Well this thing has a three sided rotor so it must some how pump out three times as much air so lets take the actual CID and times it by three". Brilliant!
Fast forward a whole bunch of years and they (you know who you are) realize that they made a boo-boo and attempted to fix it. The change went through all the appropriate channels and was okay'd TWICE before being rescinded. WTF? A little technicallity screws everything up. Somebody starts crying the blues because they're going to lose their record.
But it's okay. Pete (the OP) is going to handle the record in question. We wouldn't want anyone to get their feelings hurt because they lost their record to a RULES CHANGE (which has happened MANY times before). Oh no. Pete is building a new race car and a new race motor just so he can go out and take the record away from it's current holder. This way the record will be Pete's and when the rotary restriction rule change comes down the pipe again guess who will be losing his record? Pete will so no one will have any reason to cry about it.
Pete, I wouldn't worry too much about it man. They know they were wrong, they tried to fix it, but then they screwed it all up. Just follow through with your plan. It means parking the RX-7 but oh well. You'll go plenty fast in your new Ford Ranger.
Now if only we can clean up this "Tuner/Sport Compact" disaster. Talk about FUBAR...
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Thanks for the support Nathan. I do believe that there is only one N/A rotary engine record left. E/M/M/P S&P Racing at 151mph(elmo). The other two have been beat, E/GT Racing Beat at 178mph(bonneville) and E/GL Steve's Machine(elmo). Both which have been beaten by V8 engines, one by 12mph and the other by 10mph. I believe that it's pretty unfair to penalize an engine that you can't do much to. That's right not much, but porting. It has no cylinders to bore, no crankshaft to stroke and no camshaft to regrind. It's just an air pump.
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Well, everyone who reads this thread, no rotary for now. I'm running a 1991 ford ranger with a 2.7l ford 4cylinder. before you ask, yes it's an Esslinger setup. The Mazda will be back in a couple of years, after the little resto. Peter
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I think I might know of a dyno that you can use in the Hawthorne area to get the beast tuned. :-D
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Hope you can bring the rotary to Speedweek in 2011.
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Actually, back in the 80's, NHRA would let you run a Rotary in Competition Eliminator in D/Econo Dragster and in Super Stock in the Modified Compact classes. Terry Hoard ran an RX-3 that ended up winning a lot of races, and my Dad ran a Rotary in D/ED. The factor on the Rotary engine used to be X2, but when we went out and ran a 9.32 at 131, NHRA decided to start factoring the engine at X2.2 and killed the Rotary engine. Then NHRA came out with the Sport Compact series, and the Rotaries were back, running at a factor of X2.5, and when the Sport Compact series went south, so did the Rotary engine classes. As far as NHRA is concerned, the Rotary can run in the E.T. Bracket classes (Super Pro, Pro, and Sportsman) but only if they can meet the sound requirements, which is normally 98 db at five feet above the ground at sixty feet from the racing surface.Now, if you have ever heard an unmuffled Rotary, you know that they are ear shattering. The dragster we had used to read 132 db at an idle of 3000 rpm, and we used to leave the line and shift at 13,500. No one could seem to get a decibel reading going down the track on the car. Hate that NHRA has factored out the Rotary, because they were a great little engine and a lot of fun to run.
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There you go Pete. Campaign for 2.2 or 2.5.
DW
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A typical piston engine cycles in 4 distinc motions, a rotory only in 3. Use the 3 to 4 ratio in favor of the piston engines and if you want to beat a rotary, build a better piston engine. It's 2010, you can't expect all of today's technology to follow a patern set up in the late 1800's! There's just too many ways to make a wheel turn!
-Chad-
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It's 2010, you can't expect all of today's technology to follow a patern set up in the late 1800's! There's just too many ways to make a wheel turn!
-Chad-
Don't rock the boat too hard, you will find yourself on the wrong side of the rules. Remember its not your sand box, if you want to play, you will have to conform. Tony
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I'm sitting quietly in the omega class not really knowing what to expect from my project(s). Currently working on a bio-diesel water injected turbineshaft with a secondary side project that could best be described as "fringe technology". I admire all of the hard work and careful consideration that goes in to making a piston powered, wheel driven vehicle accelerate to it's aerodynamic limits and last long enough to back up the figures with a second run. That's the purpose of hot rodding: see how fast you can go. When somone shows up with a Wankel(or Renesis or some homemade contraption made to move a vehicle)they're there for the same reason as you: see how fast it'll go.
-Chad-
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It's 2010, you can't expect all of today's technology to follow a patern set up in the late 1800's! There's just too many ways to make a wheel turn!
-Chad-
Don't rock the boat too hard, you will find yourself on the wrong side of the rules. Remember its not your sand box, if you want to play, you will have to conform. Tony
I agree with Tony
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Chad
there is also an experience in racing that's not to enjoyable.... that's having tech tell you to load yer fancy ideas up on the trailer and go home.... Lots of people on this board who have been there and done that.... ask questions... save yourself some trouble
kent
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This is why i'm here. I already forsee all kinds of questions arising during build progress and i'd rather find out the right answer before i get stuck with loads of re-work, or the long drive home without getting to run. I didn't mean to step on toes with my rant, just praising progress and enginuity.
-Chad-
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Well, looks like it's fair game for the rotary community.