Suspension Geometery comparison FD to RX8?
06-11-13, 10:46 PM
#26
how many Mazdaspeed models have ever had more power
As far as I know every single Mazdaspeed model had more power due to the addition of a turbo.
Mazdaspeed Protege (turbo-ed)
Mazdaspeed Miata (turbo-ed)
Mazdaspeed 6 (turbo-ed, awd-ed)
Mazdaspeed 3 (turbo-ed)
The new Mazda RX-whatever sadly has to be bigger than the RX-7 because Americans are fatter now than in 1993.
As far as I know every single Mazdaspeed model had more power due to the addition of a turbo.
Mazdaspeed Protege (turbo-ed)
Mazdaspeed Miata (turbo-ed)
Mazdaspeed 6 (turbo-ed, awd-ed)
Mazdaspeed 3 (turbo-ed)
The new Mazda RX-whatever sadly has to be bigger than the RX-7 because Americans are fatter now than in 1993.
06-12-13, 06:57 AM
#27
I just think buyers are going to consider the size and Mazda must consider the size of the competition. I saw a photo of an FD next to a BRZ and it looked much smaller though they are about the same weight. I think some people will be turned off if it's really small, like an elise or miata. It should not be any bigger than the RX-8 though.
06-12-13, 09:28 AM
#28
I guess I'm thinking of all the lame special edition Miatas that were just a special paint color and a Nardi steering wheel.
Screw making it bigger. If the BRZ is bigger and roughly the same weight, make it the same size and less weight. Compact packaging is a rotary strength. Torque isn't.
Size really isn't the issue—people bought Elises and Exiges, and least in the case of the Miata, it's in the styling. It looks like a chick car. If it's aggressively (but tastefully) styled, it'll be fine. It's never going to be a Corvette.
Screw making it bigger. If the BRZ is bigger and roughly the same weight, make it the same size and less weight. Compact packaging is a rotary strength. Torque isn't.
Size really isn't the issue—people bought Elises and Exiges, and least in the case of the Miata, it's in the styling. It looks like a chick car. If it's aggressively (but tastefully) styled, it'll be fine. It's never going to be a Corvette.
06-12-13, 10:33 AM
#29
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i hope the new Rx7 isn't too much bigger than the FD, new cars are all way to big
06-12-13, 11:04 AM
#30
^^^
Indeed.
Look at a new 911 next to a classic one. It might as well be a Panamera. I parked my wifes '94 geo prism 4-door (Toyota Corolla) next to a new Corolla, and it looked like a tank. In particular, cars all seem much taller now. I know it was partly platform-dictated, but anyone remember that comparo shot of the new Challenger next to it's late-60's counterpart? The 6o's version looked like a @#$%ing lotus.
WTF. It's not like parking places are getting any bigger, and there's more room on the roads. American fat-asses I guess.
Indeed.
Look at a new 911 next to a classic one. It might as well be a Panamera. I parked my wifes '94 geo prism 4-door (Toyota Corolla) next to a new Corolla, and it looked like a tank. In particular, cars all seem much taller now. I know it was partly platform-dictated, but anyone remember that comparo shot of the new Challenger next to it's late-60's counterpart? The 6o's version looked like a @#$%ing lotus.
WTF. It's not like parking places are getting any bigger, and there's more room on the roads. American fat-asses I guess.
06-12-13, 01:35 PM
#31
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there is some newish ford/mercury sedan that is as tall as a honda odyssey...
i think making a car bigger and heavier helps in crash tests, however if you look at like volvo/mercedes/mazda (rx8 is a 5 star crash rating, the FC was 4), they can make a car that does well without making it the size of a small moon.
i think making a car bigger and heavier helps in crash tests, however if you look at like volvo/mercedes/mazda (rx8 is a 5 star crash rating, the FC was 4), they can make a car that does well without making it the size of a small moon.
06-12-13, 02:32 PM
#33
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06-13-13, 12:06 AM
#36
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the 1st generation Rx7 is 169", FD is 168.5"...
06-13-13, 06:31 AM
#37
I guess I'm thinking of all the lame special edition Miatas that were just a special paint color and a Nardi steering wheel.
Screw making it bigger. If the BRZ is bigger and roughly the same weight, make it the same size and less weight. Compact packaging is a rotary strength. Torque isn't.
Size really isn't the issue—people bought Elises and Exiges, and least in the case of the Miata, it's in the styling. It looks like a chick car. If it's aggressively (but tastefully) styled, it'll be fine. It's never going to be a Corvette.
Screw making it bigger. If the BRZ is bigger and roughly the same weight, make it the same size and less weight. Compact packaging is a rotary strength. Torque isn't.
Size really isn't the issue—people bought Elises and Exiges, and least in the case of the Miata, it's in the styling. It looks like a chick car. If it's aggressively (but tastefully) styled, it'll be fine. It's never going to be a Corvette.
?
06-13-13, 11:15 AM
#40
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06-13-13, 12:23 PM
#41
So how bout that suspension geometry
see page 1, its the same but different
Exactly! I see the job of proper suspension geometry as-
1) keep roll center close to center of gravity
2) provide camber gain equal to the body roll movement in cornering
3) provide rigidity or correct deflection to preserve assigned geometry or desired varied geometry
Mazda nailed those points with the RX-7 and RX-8.
It is really the implementation (variable geometry FD) and the other factors I mentioned earlier that makes the difference between the two.
I chose to eliminate the FD (and FC) RX-7 variable geometry and I do believe it makes for a more "honest" chassis that I can predict for and correct more quickly.
On the FD eliminating/limiting the variable goemetry is done by replacing the stock sliding bushings with standard bushings made of poly, delrin or metal (though I believe the metal bushings are pillow ball to account for slight misalignments instead of standard bushings).
The less compliant the material and the lower the tire traction available the less geometry change you will have.
see page 1, its the same but different
Exactly! I see the job of proper suspension geometry as-
1) keep roll center close to center of gravity
2) provide camber gain equal to the body roll movement in cornering
3) provide rigidity or correct deflection to preserve assigned geometry or desired varied geometry
Mazda nailed those points with the RX-7 and RX-8.
It is really the implementation (variable geometry FD) and the other factors I mentioned earlier that makes the difference between the two.
I chose to eliminate the FD (and FC) RX-7 variable geometry and I do believe it makes for a more "honest" chassis that I can predict for and correct more quickly.
On the FD eliminating/limiting the variable goemetry is done by replacing the stock sliding bushings with standard bushings made of poly, delrin or metal (though I believe the metal bushings are pillow ball to account for slight misalignments instead of standard bushings).
The less compliant the material and the lower the tire traction available the less geometry change you will have.
06-13-13, 12:34 PM
#42
06-14-13, 07:40 AM
#43
As for the geometry I've been curious about what exactly made the RX8 so much better handling. but apart from shock travel , and optimized control arms seem to be the only real difference .
bushings can be changed , shock obsorbers can be swapped and adjusted for performance rather then compromise .
would the difference between the 2 cars be THAT much ?
Last edited by Tem120; 06-14-13 at 07:51 AM.
06-14-13, 11:19 AM
#44
As for the geometry I've been curious about what exactly made the RX8 so much better handling. but apart from shock travel , and optimized control arms seem to be the only real difference .
bushings can be changed , shock obsorbers can be swapped and adjusted for performance rather then compromise .
would the difference between the 2 cars be THAT much ?
Its not that stuff. In my FD I have replaced the sliding bushings with poly and new stock spherical bearings/bushed spherical bearings in multi axis positions. I have Ohlins DFV which really improved the ride over GAB Super Rs, alignment, etc. I have been developing it in autocross racing for 4 years.
With the RX-8 I just mounted up my FD wheels/tires and boom I am super impressed with the handling and cornering speeds.
I think it is the better chassis in terms of weight distribution and wheelbase first and then the little stuff you can change second.
06-14-13, 11:42 AM
#45
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don't forget the way that they have the roll centers (front and rear) pivoting around the CG, that is probably a big change in the way it feels at the limit.
don't forget the big change they made to the Rx8 is how it feels near the limit, the FD is intimidating, and the Rx8 is almost telepathic, so when you combine this with the Rx8 being completely unflappable (you can do stupid things behind the wheel in the 8, first hand experience here), and it not only doesn't bite, but its still quick.
and of course stock to stock, the Rx8 has more tire, the shock valving isn't completely insane, the body is stiffer, the subframes are stiffer, the bushing/ball joint arrangement isn't bad out of the factory, etc
don't forget the big change they made to the Rx8 is how it feels near the limit, the FD is intimidating, and the Rx8 is almost telepathic, so when you combine this with the Rx8 being completely unflappable (you can do stupid things behind the wheel in the 8, first hand experience here), and it not only doesn't bite, but its still quick.
and of course stock to stock, the Rx8 has more tire, the shock valving isn't completely insane, the body is stiffer, the subframes are stiffer, the bushing/ball joint arrangement isn't bad out of the factory, etc
06-15-13, 06:11 AM
#46
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I read somewhere that the Rx8 chassis has a torsional stiffness of around 30000 Nm per degree, while the FD chassis is at 15000. If true, that should make quite a difference.
I'm sure that Mazda will continue refining and improving their suspensions with the 4th gen Miata and the 4th gen Rx7. Possibly slightly tweaked geometries and other minor tweaks. I think it will be possible to have magnetorheological dampers installed in the next cars, at least as an option (Audi is already offering them in not-so-top-of-the-line models, so other manufacturers may follow soon).
There is always the possibility of going with an inboard rear brakes setup, which would greatly reduce unsprung weight (if differential overheating problems can be avoided).
Andrea.
I'm sure that Mazda will continue refining and improving their suspensions with the 4th gen Miata and the 4th gen Rx7. Possibly slightly tweaked geometries and other minor tweaks. I think it will be possible to have magnetorheological dampers installed in the next cars, at least as an option (Audi is already offering them in not-so-top-of-the-line models, so other manufacturers may follow soon).
There is always the possibility of going with an inboard rear brakes setup, which would greatly reduce unsprung weight (if differential overheating problems can be avoided).
Andrea.
06-15-13, 07:00 AM
#47
I had a conversation with an engineer from TRW (braking systems etc) a while back...
One thing you have to keep in mind is that during the days of the FC and FD, electronic stability control, brake force distribution, torque vectoring, etc wasn't available for non supercars. There was no way for a computer to step in and help guide the handling of the vehicle, except in the most simplest of way (crude ABS). Therefore the suspension geometry had to do a lot more. That's why you had special bushing designs and such like the FD and FC had to change toe and camber.
You can see that among more pedestrian kind of vehicles. A lot of cars had double wishbone or multilink suspensions in the 90s (Civic and Eclipse are a good example). Later on, they went back to cheaper suspensions and used the stability control system to help with handling and safety for normal non-performance driving situations.
One thing you have to keep in mind is that during the days of the FC and FD, electronic stability control, brake force distribution, torque vectoring, etc wasn't available for non supercars. There was no way for a computer to step in and help guide the handling of the vehicle, except in the most simplest of way (crude ABS). Therefore the suspension geometry had to do a lot more. That's why you had special bushing designs and such like the FD and FC had to change toe and camber.
You can see that among more pedestrian kind of vehicles. A lot of cars had double wishbone or multilink suspensions in the 90s (Civic and Eclipse are a good example). Later on, they went back to cheaper suspensions and used the stability control system to help with handling and safety for normal non-performance driving situations.
06-15-13, 03:49 PM
#48
You can see that among more pedestrian kind of vehicles. A lot of cars had double wishbone or multilink suspensions in the 90s (Civic and Eclipse are a good example). Later on, they went back to cheaper suspensions and used the stability control system to help with handling and safety for normal non-performance driving situations.
So as the cars got smarter, the suspensions got dumber? Mazda had better not do that to the next Rx7.
06-15-13, 04:31 PM
#49
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a lot of car bloat has to do with safety standards.
Taking the Hit: How Pedestrian-Protection Regs Make Cars Fatter - Feature - Car and Driver
Taking the Hit: How Pedestrian-Protection Regs Make Cars Fatter - Feature - Car and Driver
06-15-13, 04:38 PM
#50
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i'd take that with a grain of salt, Honda went Mc Pherson strut in 2000, that's before they had traction control or anything fancier than 4 channel ABS.
and then there are the pesky Germans, every BMW, and the 911 have always been Mc Pherson strut, from the beginning right up to now... maybe they are in the other camp, where they got to keep the economy car suspension, but got faster with ABS/TSC/DSC
and then there are the pesky Germans, every BMW, and the 911 have always been Mc Pherson strut, from the beginning right up to now... maybe they are in the other camp, where they got to keep the economy car suspension, but got faster with ABS/TSC/DSC
