Did 1991 Mazda 787b honestly wins at Le Mans ?
10-29-21, 10:46 AM
#1
Rotary Enthusiast
Thread Starter
Did 1991 Mazda 787b honestly wins at Le Mans ?
The 787b was entered as having the 2.6L R26B engine. Since then, this rating based on Dr Wankel's unique 4 stroke, one rev rating has been doubled in later racing events. That would put the R2.6B at an honest 5.2L. At Le Mans, the car was entered in the C2 class, and it appeared to be limited to 3.5L but I'm not sure. Any input would be appreciated.
1991 24hrs of Le Mans
Group C & C2 Classes
KevinK2
1991 24hrs of Le Mans
Group C & C2 Classes
KevinK2
10-29-21, 11:11 AM
#2
The 787b was entered as having the 2.6L R26B engine. Since then, this rating based on Dr Wankel's unique 4 stroke, one rev rating has been doubled in later racing events. That would put the R2.6B at an honest 5.2L. At Le Mans, the car was entered in the C2 class, and it appeared to be limited to 3.5L but I'm not sure. Any input would be appreciated.
1991 24hrs of Le Mans
Group C & C2 Classes
KevinK2
1991 24hrs of Le Mans
Group C & C2 Classes
KevinK2
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10-29-21, 11:17 AM
#3
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exactly, racing rules change all the time.
10-29-21, 12:59 PM
#4
RX-7 Bad Ass
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When I first got into RX-7's back a million years ago and heard about the Lemans win I assumed it was a class win or something like that - fastest of a certain type of car or something.
Nope, Mazda flat-out WON. First place.
If you have the Yamaguchi book on the third gen RX-7 it has a lot of detail on the racing effort, there was a LOT that went into that win.
It's a very prestigious win for a relatively small Japanese manufacturer, even more so with a "weird" engine. They deserve all the credit.
Dale
Nope, Mazda flat-out WON. First place.
If you have the Yamaguchi book on the third gen RX-7 it has a lot of detail on the racing effort, there was a LOT that went into that win.
It's a very prestigious win for a relatively small Japanese manufacturer, even more so with a "weird" engine. They deserve all the credit.
Dale
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10-29-21, 02:21 PM
#6
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Thread Starter
Rotary engine displacement
Dale, it was a great win, and inspired me to buy my 3rd gen based mostly on shape. But they sneaked in with the 2.6L engine rating.
Kevin (from original Big List days)
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DaleClark (10-30-21)
10-29-21, 02:45 PM
#7
Mazda has the trophy. This discussion (rotary displacement) is older than time. Why are we dredging it up all of the sudden? Cheating/bending/changing/evading the rules is the essence of the sport of racing. If things were different, things would be different. They're not. Mazda won. It's carved in the tomes of history. We're here now discussing it. So?
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Trending Topics
10-29-21, 04:14 PM
#9
This discussion is almost as old as I am (LITERALLY)! There's an infinite amount of stories throughout motorsports history highlighting different tactics race teams used to gain a competitive edge. At this point, I'm pretty sure it's become half of what racing is all about..."What can we do to make this team competitive, and win?" No use in questioning it 30 years later, because the rules of that day are always forgotten.
10-29-21, 04:19 PM
#10
Rotary Enthusiast
Thread Starter
Mazda has the trophy. This discussion (rotary displacement) is older than time. Why are we dredging it up all of the sudden? Cheating/bending/changing/evading the rules is the essence of the sport of racing. If things were different, things would be different. They're not. Mazda won. It's carved in the tomes of history. We're here now discussing it. So?
EDIT: There was a 1984 race there where the 13B was used and rated at 2.6L. At !984 Le Mans, 13B rated at 2.6L
So there was an early knowledge that the Dr. Wankel's displacement rating needed to be doubled, even if displacement was not considered in 1991.
Narfle, have a good day !
Kevin
Last edited by KevinK2; 10-30-21 at 10:14 AM. Reason: 1984 race at Le Mans
10-29-21, 04:34 PM
#11
Racecar - Formula 2000
The race officials set the rules. The Mazda team followed them. The fact that it really is more displacement than was allowed is immaterial.
This reminds me of Penske's 1000 HP pushrod engine at Indy. The fact that it was an unfair advantage doesn't matter - they built the engine to the rules. The fact that the rules allowed the Mazda and Penske teams to run that way is not the teams' fault.
This reminds me of Penske's 1000 HP pushrod engine at Indy. The fact that it was an unfair advantage doesn't matter - they built the engine to the rules. The fact that the rules allowed the Mazda and Penske teams to run that way is not the teams' fault.
10-29-21, 05:29 PM
#12
You're statement suggests the governing body simply took Mazda at their word regarding the displacement of the engine. Surely we can all agree that's a ridiculous notion. Their vehicle was scrutinized and audited just like everyone else's. It wasn't until x-time afterwards that the motorsport governing bodies reached a standardized consensus regarding how to calculate displacement for a rotary engine when comparing it to a piston engine. Like everyone else has essentially said.
Also, you're technically not describing the calculation method and comparison process correctly in your previous post. Completing 1 thermodynamic cycle (intake, compression, combustion, and exhaust in each chamber) is the standard for how piston engines are rated and that takes 720° of rotation or 2 complete revolutions of the crankshaft. On the same standard, it is accurate to say that a rotary engine completes a thermodynamic cycle in 360° or 1 complete revolution of the eccentric shaft.
BUT you can interpret the standard differently..
A. a thermodynamic cycle is achieving a combustion in each rotor housing = requires 360° of rotation and yields 1.3L
B. a thermodynamic cycle is achieving a combustion on each rotor face = requires 1080° of rotation and yields 3.9L
BUT BUT it has now been generally agreed that neither of these actually compares well to piston engine. So instead, it has been broadly accepted to take the degrees of rotation required for 1 thermodynamic cycle in a piston engine and calculate a rotary engine's displacement using the same amount of rotation.
A 4 piston engine has 4 combustions in one thermodynamic cycle or 720° of rotation
A 2 rotor engine has 4 combustions in 720° of rotation
That is why it is considered "normal" to think of a 1.3L rotary engine as a 2.6L. But if piston engines never existed, no person on earth would ever have thought to calculate a rotary engine's displacement this way.
Also, you're technically not describing the calculation method and comparison process correctly in your previous post. Completing 1 thermodynamic cycle (intake, compression, combustion, and exhaust in each chamber) is the standard for how piston engines are rated and that takes 720° of rotation or 2 complete revolutions of the crankshaft. On the same standard, it is accurate to say that a rotary engine completes a thermodynamic cycle in 360° or 1 complete revolution of the eccentric shaft.
BUT you can interpret the standard differently..
A. a thermodynamic cycle is achieving a combustion in each rotor housing = requires 360° of rotation and yields 1.3L
B. a thermodynamic cycle is achieving a combustion on each rotor face = requires 1080° of rotation and yields 3.9L
BUT BUT it has now been generally agreed that neither of these actually compares well to piston engine. So instead, it has been broadly accepted to take the degrees of rotation required for 1 thermodynamic cycle in a piston engine and calculate a rotary engine's displacement using the same amount of rotation.
A 4 piston engine has 4 combustions in one thermodynamic cycle or 720° of rotation
A 2 rotor engine has 4 combustions in 720° of rotation
That is why it is considered "normal" to think of a 1.3L rotary engine as a 2.6L. But if piston engines never existed, no person on earth would ever have thought to calculate a rotary engine's displacement this way.
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10-29-21, 06:17 PM
#14
Rotary Enthusiast
Thread Starter
The race officials set the rules. The Mazda team followed them. The fact that it really is more displacement than was allowed is immaterial.
This reminds me of Penske's 1000 HP pushrod engine at Indy. The fact that it was an unfair advantage doesn't matter - they built the engine to the rules. The fact that the rules allowed the Mazda and Penske teams to run that way is not the teams' fault.
This reminds me of Penske's 1000 HP pushrod engine at Indy. The fact that it was an unfair advantage doesn't matter - they built the engine to the rules. The fact that the rules allowed the Mazda and Penske teams to run that way is not the teams' fault.
10-29-21, 06:29 PM
#15
Racecar - Formula 2000
Sure, in hindsight you are correct. The meaning of rules is often contested. The fact is the rules allowed this to happen because they were not adequately defined.
10-29-21, 06:34 PM
#16
Rotary Enthusiast
Thread Starter
You're statement suggests the governing body simply took Mazda at their word regarding the displacement of the engine. Surely we can all agree that's a ridiculous notion. Their vehicle was scrutinized and audited just like everyone else's. It wasn't until x-time afterwards that the motorsport governing bodies reached a standardized consensus regarding how to calculate displacement for a rotary engine when comparing it to a piston engine. Like everyone else has essentially said.
Also, you're technically not describing the calculation method and comparison process correctly in your previous post. Completing 1 thermodynamic cycle (intake, compression, combustion, and exhaust in each chamber) is the standard for how piston engines are rated and that takes 720° of rotation or 2 complete revolutions of the crankshaft. On the same standard, it is accurate to say that a rotary engine completes a thermodynamic cycle in 360° or 1 complete revolution of the eccentric shaft.
BUT you can interpret the standard differently..
A. a thermodynamic cycle is achieving a combustion in each rotor housing = requires 360° of rotation and yields 1.3L
B. a thermodynamic cycle is achieving a combustion on each rotor face = requires 1080° of rotation and yields 3.9L
BUT BUT it has now been generally agreed that neither of these actually compares well to piston engine. So instead, it has been broadly accepted to take the degrees of rotation required for 1 thermodynamic cycle in a piston engine and calculate a rotary engine's displacement using the same amount of rotation.
A 4 piston engine has 4 combustions in one thermodynamic cycle or 720° of rotation
A 2 rotor engine has 4 combustions in 720° of rotation
That is why it is considered "normal" to think of a 1.3L rotary engine as a 2.6L. But if piston engines never existed, no person on earth would ever have thought to calculate a rotary engine's displacement this way.
Also, you're technically not describing the calculation method and comparison process correctly in your previous post. Completing 1 thermodynamic cycle (intake, compression, combustion, and exhaust in each chamber) is the standard for how piston engines are rated and that takes 720° of rotation or 2 complete revolutions of the crankshaft. On the same standard, it is accurate to say that a rotary engine completes a thermodynamic cycle in 360° or 1 complete revolution of the eccentric shaft.
BUT you can interpret the standard differently..
A. a thermodynamic cycle is achieving a combustion in each rotor housing = requires 360° of rotation and yields 1.3L
B. a thermodynamic cycle is achieving a combustion on each rotor face = requires 1080° of rotation and yields 3.9L
BUT BUT it has now been generally agreed that neither of these actually compares well to piston engine. So instead, it has been broadly accepted to take the degrees of rotation required for 1 thermodynamic cycle in a piston engine and calculate a rotary engine's displacement using the same amount of rotation.
A 4 piston engine has 4 combustions in one thermodynamic cycle or 720° of rotation
A 2 rotor engine has 4 combustions in 720° of rotation
That is why it is considered "normal" to think of a 1.3L rotary engine as a 2.6L. But if piston engines never existed, no person on earth would ever have thought to calculate a rotary engine's displacement this way.
I was trying to not to bring in the full treatment of the swept volume for an engine cycle, putting a 13B at 3.9L in 3 revs of the crankshaft. I provided a link that covered what you said about the rating, and it included a bit about Dr Wankel's initial work.
If they did a thorough check of that engine, it would have been 5.2L. They DID rely on common knowledge, unless you can prove otherwise.
EDIT: I was later convinced that displacement was not a major consideration at that event, as the cars were mostly limited on the fuel load. But Mazda did argue about the added weight they were to carry, getting it reduced a couple hundred pounds. Displacement may have come up in this regard.
Last edited by KevinK2; 10-30-21 at 09:40 AM.
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10-29-21, 07:29 PM
#19
Sometimes I wish there was a dislike button on the posts like Reddit.
To the OP: How is the displacement of a 2- stroke engine, either gas or diesel calculated?
The answer to all is displacement of the swept volume x number of chambers. There is no factoring involved for whether it is 4 stroke, 2 stroke or otherwise.
That's why it's 2.6L. That's why the FD is 1.3L.
To try to argue anything otherwise is futile as it doesn't meet the SAE definition of displacement.
Vince
To the OP: How is the displacement of a 2- stroke engine, either gas or diesel calculated?
The answer to all is displacement of the swept volume x number of chambers. There is no factoring involved for whether it is 4 stroke, 2 stroke or otherwise.
That's why it's 2.6L. That's why the FD is 1.3L.
To try to argue anything otherwise is futile as it doesn't meet the SAE definition of displacement.
Vince
10-29-21, 09:23 PM
#21
The rules at the time were dictated by fuel consumption, so displacement was kind of moot.
1991 was a transition year for Le Mans racers. For 1992 all cars would be required to have 3.5L naturally aspirated piston engines.
To give the new 3.5L cars a win, everyone racing with an older engine had weight added to them.
Mazda lobbied the organizers to run with the old weight limit. Since the rotary wouldn't be allowed after 1991 and they only finished as high as 7th, they probably didn't see them as a threat and didn't want to lose 3 cars on the grid so they let them.
Jaguar had a 3.5L car but withdrew it because they didn't think it would last. The extra weight with their 7.4 V12 killed their fuel economy so they had to go slower.
Mercedes was fastest, but both cars broke down due to broken alternator brackets letting the belts slip.
The 3.5L engines were essentially F1 engines so most of them didn't make it. They would get better but needed more work.
Jaguar still finished 2, 3, 4 position, so it wasn't a walk in the park for Mazda. The 4 rotor was still less powerful, but they squeezed more power out of it than in 1990 and improved fuel consumption.
If you look back at Mazda's endurance wins, their cars were slower but at the time the rotary was one of the few engines that could be driven flat out for 24 hours.
I know some people think if the car wasn't the fastest it doesn't deserve to win, but endurance racing is about reliability as it is about speed. Look at the Le Mans 24 races in 2016 and 2017.
edit: another tidbit, the other Mazda 787B was running well but finished 6th because one of the drivers (David Kennedy) insisted on shortening the final drive because he was sure there would be heavy rain. He scorns himself to this day for that.
1991 was a transition year for Le Mans racers. For 1992 all cars would be required to have 3.5L naturally aspirated piston engines.
To give the new 3.5L cars a win, everyone racing with an older engine had weight added to them.
Mazda lobbied the organizers to run with the old weight limit. Since the rotary wouldn't be allowed after 1991 and they only finished as high as 7th, they probably didn't see them as a threat and didn't want to lose 3 cars on the grid so they let them.
Jaguar had a 3.5L car but withdrew it because they didn't think it would last. The extra weight with their 7.4 V12 killed their fuel economy so they had to go slower.
Mercedes was fastest, but both cars broke down due to broken alternator brackets letting the belts slip.
The 3.5L engines were essentially F1 engines so most of them didn't make it. They would get better but needed more work.
Jaguar still finished 2, 3, 4 position, so it wasn't a walk in the park for Mazda. The 4 rotor was still less powerful, but they squeezed more power out of it than in 1990 and improved fuel consumption.
If you look back at Mazda's endurance wins, their cars were slower but at the time the rotary was one of the few engines that could be driven flat out for 24 hours.
I know some people think if the car wasn't the fastest it doesn't deserve to win, but endurance racing is about reliability as it is about speed. Look at the Le Mans 24 races in 2016 and 2017.
edit: another tidbit, the other Mazda 787B was running well but finished 6th because one of the drivers (David Kennedy) insisted on shortening the final drive because he was sure there would be heavy rain. He scorns himself to this day for that.
Last edited by j_tso; 10-29-21 at 09:46 PM.
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10-29-21, 09:34 PM
#22
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The race officials set the rules. The Mazda team followed them. The fact that it really is more displacement than was allowed is immaterial.
This reminds me of Penske's 1000 HP pushrod engine at Indy. The fact that it was an unfair advantage doesn't matter - they built the engine to the rules. The fact that the rules allowed the Mazda and Penske teams to run that way is not the teams' fault.
This reminds me of Penske's 1000 HP pushrod engine at Indy. The fact that it was an unfair advantage doesn't matter - they built the engine to the rules. The fact that the rules allowed the Mazda and Penske teams to run that way is not the teams' fault.
10-30-21, 07:12 AM
#23
Racecar - Formula 2000
The rules at the time were dictated by fuel consumption, so displacement was kind of moot.
1991 was a transition year for Le Mans racers. For 1992 all cars would be required to have 3.5L naturally aspirated piston engines.
To give the new 3.5L cars a win, everyone racing with an older engine had weight added to them.
Mazda lobbied the organizers to run with the old weight limit. Since the rotary wouldn't be allowed after 1991 and they only finished as high as 7th, they probably didn't see them as a threat and didn't want to lose 3 cars on the grid so they let them.
Jaguar had a 3.5L car but withdrew it because they didn't think it would last. The extra weight with their 7.4 V12 killed their fuel economy so they had to go slower.
Mercedes was fastest, but both cars broke down due to broken alternator brackets letting the belts slip.
The 3.5L engines were essentially F1 engines so most of them didn't make it. They would get better but needed more work.
Jaguar still finished 2, 3, 4 position, so it wasn't a walk in the park for Mazda. The 4 rotor was still less powerful, but they squeezed more power out of it than in 1990 and improved fuel consumption.
If you look back at Mazda's endurance wins, their cars were slower but at the time the rotary was one of the few engines that could be driven flat out for 24 hours.
I know some people think if the car wasn't the fastest it doesn't deserve to win, but endurance racing is about reliability as it is about speed. Look at the Le Mans 24 races in 2016 and 2017.
edit: another tidbit, the other Mazda 787B was running well but finished 6th because one of the drivers (David Kennedy) insisted on shortening the final drive because he was sure there would be heavy rain. He scorns himself to this day for that.
1991 was a transition year for Le Mans racers. For 1992 all cars would be required to have 3.5L naturally aspirated piston engines.
To give the new 3.5L cars a win, everyone racing with an older engine had weight added to them.
Mazda lobbied the organizers to run with the old weight limit. Since the rotary wouldn't be allowed after 1991 and they only finished as high as 7th, they probably didn't see them as a threat and didn't want to lose 3 cars on the grid so they let them.
Jaguar had a 3.5L car but withdrew it because they didn't think it would last. The extra weight with their 7.4 V12 killed their fuel economy so they had to go slower.
Mercedes was fastest, but both cars broke down due to broken alternator brackets letting the belts slip.
The 3.5L engines were essentially F1 engines so most of them didn't make it. They would get better but needed more work.
Jaguar still finished 2, 3, 4 position, so it wasn't a walk in the park for Mazda. The 4 rotor was still less powerful, but they squeezed more power out of it than in 1990 and improved fuel consumption.
If you look back at Mazda's endurance wins, their cars were slower but at the time the rotary was one of the few engines that could be driven flat out for 24 hours.
I know some people think if the car wasn't the fastest it doesn't deserve to win, but endurance racing is about reliability as it is about speed. Look at the Le Mans 24 races in 2016 and 2017.
edit: another tidbit, the other Mazda 787B was running well but finished 6th because one of the drivers (David Kennedy) insisted on shortening the final drive because he was sure there would be heavy rain. He scorns himself to this day for that.
10-30-21, 08:39 AM
#25
Rotary Enthusiast
Thread Starter
Originally Posted by j_tso
The rules at the time were dictated by fuel consumption, so displacement was kind of moot.
Kevin
Last edited by KevinK2; 10-30-21 at 08:49 AM.