Please help explain to me how the Rolex Mazda RX8's can be so fast??
04-15-2010, 09:52 AM
#1
Le Mans Master
Thread Starter
Please help explain to me how the Rolex Mazda RX8's can be so fast??
They have 1.3 Liter rotary engines and rule book states 2300ish lbs. I mean HOW much power can you get out of a 1.3 (non turbo) rotary engine?
The Corvette minimum is 2550lbs and has an LS6 5.7 Liter V8 with easily 450+hp and torque.
HOW THE HECK, can a 1.3L Mazda be in the same class...let alone beat a specially preppared Corvette with a 5.7L??? We are only talking a 250lb difference. I can't imagine that would be nearly enough to make up the power difference.
I have gone up against many Lotus Elise's weighting something like 2000lbs and our 3200+lbs Corvette's eat them for lunch all day at the track...and that is 1000lbs extra.
Obviously there is a good reason as they are winning (1st, 2nd and 3rd) at Barber. I guess I have never paid attention or gave it enough thought as to how these cars are so competitive.
The Corvette minimum is 2550lbs and has an LS6 5.7 Liter V8 with easily 450+hp and torque.
HOW THE HECK, can a 1.3L Mazda be in the same class...let alone beat a specially preppared Corvette with a 5.7L??? We are only talking a 250lb difference. I can't imagine that would be nearly enough to make up the power difference.
I have gone up against many Lotus Elise's weighting something like 2000lbs and our 3200+lbs Corvette's eat them for lunch all day at the track...and that is 1000lbs extra.
Obviously there is a good reason as they are winning (1st, 2nd and 3rd) at Barber. I guess I have never paid attention or gave it enough thought as to how these cars are so competitive.
04-15-2010, 10:12 AM
#3
Melting Slicks
-TJ
04-15-2010, 11:52 AM
#5
Le Mans Master
Thread Starter
04-15-2010, 12:09 PM
#6
Le Mans Master
the engine in question is a Wankel.
Exerpts from Wikipedia
The Wankel produces twelve strokes per revolution of the rotor
(four strokes per chamber times three chambers) (although the
spindle rotates three times faster than the rotor or three times
over the twelve strokes), as opposed to two strokes for each
crankshaft rotation of a single-cylinder single acting piston engine
- Wankel 3 rotor x 12 strokes/cyl = 36 strokes
- Otto 8 cylinder x 2 strokes/cyl = 16 strokes
A Wankel engine has no empty stroke like a reciprocating four stroke
piston engine, therefore a Wankel engine needs only half the volume
of a reciprocating four stroke engine.
If looking for the maximum possible displacement, a twin rotor Wankel
rotary displacing 654cc per combustion chamber (such as the Mazda
13B) has a maximum displacement of 3924cc (3.9 liters). This is
because there are three possible combustion chambers per rotor,
each displacing 654cc at full expansion. 654cc per face, three faces
per rotor (1962cc/2 liters), two rotors per engine (3924cc/3.9 liters).
Other notable rotaries such as the '2 liter' 3-rotor Mazda 20b in the
Eunos Cosmo (total displacement: 5886cc/5.9 liters) and '2.6 liter'
4-rotor Mazda R26b from the Le Mans winning 787b (total
displacement: 7848cc/7.8 liters) can have maximum
displacement calculated in the same way.
However comparing rotaries to piston engines using this method is
futile as the Wankel's subjects its full displacement to a power stroke
after three full rotations of the eccentric shaft. This means comparing
a hypothetical 3.9 liter piston engine to a '1.3 liter' Wankel rotary
(with a maximum possible displacement of 3.9 liters) using this
method will result in the piston engine's theoretical specific output
being approximately 50% higher than the Wankel rotary because the
piston engine will displace its 3.9 liters through a power stroke one
revolution (50%) sooner than the Wankel rotary.
For comparison purposes between a Wankel Rotary engine and a
piston engine, displacement (and thus power output) can more
accurately be compared on a displacement per revolution (of the
eccentric shaft) basis. This dictates that a two rotor Wankel
displacing 654cc per face will have a displacement of 1.3 liters per
every rotation of the eccentric shaft(only two total faces, one face
per rotor going through a full power stroke) and 2.6 liters after two
revolutions (four total faces, two faces per rotor going through a
full power stroke). This is directly comparable to a 2.6 liter piston
engine with an even number of cylinders in a conventional firing
order which will also displace 1.3 liters through its power stroke
after one revolution of the crankshaft, and 2.6 liters through its
power strokes after two revolutions of the crankshaft. Measuring
a Wankel rotary engine in this way more accurately explains its
specific output numbers, as the volume of its air fuel mixture put
through a power stroke per revolution is directly responsible for
torque and thus horsepower produced.
.
(four strokes per chamber times three chambers) (although the
spindle rotates three times faster than the rotor or three times
over the twelve strokes), as opposed to two strokes for each
crankshaft rotation of a single-cylinder single acting piston engine
- Wankel 3 rotor x 12 strokes/cyl = 36 strokes
- Otto 8 cylinder x 2 strokes/cyl = 16 strokes
A Wankel engine has no empty stroke like a reciprocating four stroke
piston engine, therefore a Wankel engine needs only half the volume
of a reciprocating four stroke engine.
If looking for the maximum possible displacement, a twin rotor Wankel
rotary displacing 654cc per combustion chamber (such as the Mazda
13B) has a maximum displacement of 3924cc (3.9 liters). This is
because there are three possible combustion chambers per rotor,
each displacing 654cc at full expansion. 654cc per face, three faces
per rotor (1962cc/2 liters), two rotors per engine (3924cc/3.9 liters).
Other notable rotaries such as the '2 liter' 3-rotor Mazda 20b in the
Eunos Cosmo (total displacement: 5886cc/5.9 liters) and '2.6 liter'
4-rotor Mazda R26b from the Le Mans winning 787b (total
displacement: 7848cc/7.8 liters) can have maximum
displacement calculated in the same way.
However comparing rotaries to piston engines using this method is
futile as the Wankel's subjects its full displacement to a power stroke
after three full rotations of the eccentric shaft. This means comparing
a hypothetical 3.9 liter piston engine to a '1.3 liter' Wankel rotary
(with a maximum possible displacement of 3.9 liters) using this
method will result in the piston engine's theoretical specific output
being approximately 50% higher than the Wankel rotary because the
piston engine will displace its 3.9 liters through a power stroke one
revolution (50%) sooner than the Wankel rotary.
For comparison purposes between a Wankel Rotary engine and a
piston engine, displacement (and thus power output) can more
accurately be compared on a displacement per revolution (of the
eccentric shaft) basis. This dictates that a two rotor Wankel
displacing 654cc per face will have a displacement of 1.3 liters per
every rotation of the eccentric shaft(only two total faces, one face
per rotor going through a full power stroke) and 2.6 liters after two
revolutions (four total faces, two faces per rotor going through a
full power stroke). This is directly comparable to a 2.6 liter piston
engine with an even number of cylinders in a conventional firing
order which will also displace 1.3 liters through its power stroke
after one revolution of the crankshaft, and 2.6 liters through its
power strokes after two revolutions of the crankshaft. Measuring
a Wankel rotary engine in this way more accurately explains its
specific output numbers, as the volume of its air fuel mixture put
through a power stroke per revolution is directly responsible for
torque and thus horsepower produced.
04-15-2010, 12:48 PM
#8
Melting Slicks
In general, in road course racing if two cars have a close power to weight ratio the lighter car is going to win. It will stop quicker, and it will transition quicker as well. Given equal tires and aero it will probably corner quicker too.
-TJ
04-15-2010, 01:02 PM
#10
Burning Brakes
Member Since: May 2001
Location: Coto de Caza CA
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They have 1.3 Liter rotary engines and rule book states 2300ish lbs. I mean HOW much power can you get out of a 1.3 (non turbo) rotary engine?
The Corvette minimum is 2550lbs and has an LS6 5.7 Liter V8 with easily 450+hp and torque.
HOW THE HECK, can a 1.3L Mazda be in the same class...let alone beat a specially preppared Corvette with a 5.7L??? We are only talking a 250lb difference. I can't imagine that would be nearly enough to make up the power difference.
I have gone up against many Lotus Elise's weighting something like 2000lbs and our 3200+lbs Corvette's eat them for lunch all day at the track...and that is 1000lbs extra.
Obviously there is a good reason as they are winning (1st, 2nd and 3rd) at Barber. I guess I have never paid attention or gave it enough thought as to how these cars are so competitive.
The Corvette minimum is 2550lbs and has an LS6 5.7 Liter V8 with easily 450+hp and torque.
HOW THE HECK, can a 1.3L Mazda be in the same class...let alone beat a specially preppared Corvette with a 5.7L??? We are only talking a 250lb difference. I can't imagine that would be nearly enough to make up the power difference.
I have gone up against many Lotus Elise's weighting something like 2000lbs and our 3200+lbs Corvette's eat them for lunch all day at the track...and that is 1000lbs extra.
Obviously there is a good reason as they are winning (1st, 2nd and 3rd) at Barber. I guess I have never paid attention or gave it enough thought as to how these cars are so competitive.
I would speculate that it is because none of the teams running them have the resources and experience that SpeedSource has with Mazda.
04-15-2010, 03:14 PM
#11
Drifting
250lbs is a lot at that level. We're talking a roughly 10% difference, which is huge. I don't know what each car is putting out, but I've heard the 'vettes have a pretty limiting restrictor on them. The 20b (even NA) is very capable of high-end HP. They don't make a lot of torque, but that doesn't really matter with a sequential trans and the right gearing. I wouldn't be surprised if the RX8 is pretty much comparable in power to weight ratio w/ the 'vette.
In general, in road course racing if two cars have a close power to weight ratio the lighter car is going to win. It will stop quicker, and it will transition quicker as well. Given equal tires and aero it will probably corner quicker too.
-TJ
In general, in road course racing if two cars have a close power to weight ratio the lighter car is going to win. It will stop quicker, and it will transition quicker as well. Given equal tires and aero it will probably corner quicker too.
-TJ
The Vette's are allowed to run a forged, stock displacement, stock
compression, unported heads or manifold, stock cam LS6 motor.
Valvetrain can be lighter and also use shaft rockers
or
same basic thing LS2 with dumb-downed cam, not even stock LS2 cam.
The 210hp lotus would lose at Putnam (and has 
)but the new 230 - 240 horse might be a different story.
04-15-2010, 08:25 PM
#14
The mazdas were pulling lap times late in stints that none of the heavier cars (Corvettes, Camaros, BMW, etc) were within seconds of due to tire wear
Not an excuse persay, but explaining why what happened, happened.
Even the Mazda teams were complaining about how hard Barber is on tires, and if they are complaining that is telling you something.
04-15-2010, 09:12 PM
#16
Drifting
Matt Connolly owned car is a Crawford tube chassis
LG is a stock tub car and I think the Whelen car is as well. prep 1
04-15-2010, 09:56 PM
#17
04-15-2010, 11:53 PM
#19
Former Vendor
We will get there. They have been developing those cars for a long time. Our car has barely 750 miles on it, and that was its first FULL race.
Riley designed everything but the green house on the mazda chassis, so you know its top notch, plus a DP gearbox ( the diff that we cant use due to prep 1 vs prep 2 rules)
04-16-2010, 12:08 AM
#20
Melting Slicks
We will get there. They have been developing those cars for a long time. Our car has barely 750 miles on it, and that was its first FULL race.
Riley designed everything but the green house on the mazda chassis, so you know its top notch, plus a DP gearbox ( the diff that we cant use due to prep 1 vs prep 2 rules)
Riley designed everything but the green house on the mazda chassis, so you know its top notch, plus a DP gearbox ( the diff that we cant use due to prep 1 vs prep 2 rules)
