Always thought they were great cars, best of the era of Japanese GT/sports except for two things -- the miserable head room (which also aflicts the RX-8 AFAICT from a brief showroom sampling) and the rotary. Yeah yeah, it's small and light and revs like crazy, but what an awesome car the RX-7 could be with a properly built, light, small-block under the hood... People tend to ignore pushrod engines, and lately GM has seemed to want to build them bigger, but there's little out there that can equal them for HP/pound, overall HWY mileage (considering the HP output), and longevity.
Always thought they were great cars, best of the era of Japanese GT/sports except for two things -- the miserable head room (which also aflicts the RX-8 AFAICT from a brief showroom sampling) and the rotary. Yeah yeah, it's small and light and revs like crazy, but what an awesome car the RX-7 could be with a properly built, light, small-block under the hood... People tend to ignore pushrod engines, and lately GM has seemed to want to build them bigger, but there's little out there that can equal them for HP/pound, overall HWY mileage (considering the HP output), and longevity.
A guy named Jim Labreck, who goes by the name "jimlab" on the RX7 forums, has produced a fair amount of documentation on fitting chevy 350s into the 3rd gen 7. As far as I know, the rationale for the new 6L in the GMs has to do with thee fact that they though 4.0L of V6, and 3.0L of V4, were needed when the cylinders shutdown. Plus, I'm happy with the move, since it ditches the English system. I hate the English system.
I am a big fan of the GM pushrods, but I will say that mazda made the right choice in going rotary. The problem are the twin sequential turbos. A 2.0L, 3 rotor, naturally aspirated rotary would have been much better. A single turbo would have been fine as well. The rotory keeps the car really light, the center of gravity really low, and I think it's the perfect engine for cars that are designed explicitly to perform well around a track. If that's the idea, which it was for the 3rd gen 7, then the rotary makes all sorts of sense.
Anyway, to be more specific, in the WRX I can put down half of the rear bench, fold down the front passenger's seat, and still fit two people and two surfboards.
Anyway, to be more specific, in the WRX I can put down half of the rear bench, fold down the front passenger's seat, and still fit two people and two surfboards. [/B]
Look at the Subaru Forrester Turbo as well - more room than a WRX, and it is fastest car 0-30 (faster than a Lambo or Fararri).
Always thought they were great cars, best of the era of Japanese GT/sports except for two things -- the miserable head room (which also aflicts the RX-8 AFAICT from a brief showroom sampling) and the rotary. Yeah yeah, it's small and light and revs like crazy, but what an awesome car the RX-7 could be with a properly built, light, small-block under the hood... People tend to ignore pushrod engines, and lately GM has seemed to want to build them bigger, but there's little out there that can equal them for HP/pound, overall HWY mileage (considering the HP output), and longevity.
I thought the big point of rotaries is power/weight ratio. What kind of weight and power do these small blocks have?
Remember, it's not just the weight that is the problem, it's weight distribution and the height of center of mass.
Since we're in speculation land, how about the Renesis engine from RX-8. 275lbs which I guess is very little... Splinemodel, how much does 13B-REW weigh? And the associated stock turbos, intercooler and tubing?
Just thinking about a hardcore Renesis two-seater at 1200kg or below. Mazda is already managing to make the MX-5 pretty light despite it being convertible, if they made a coupe, planted the Renesis in there and concentrated on keeping the weight down I think that would be sweet.
Pushrod engines can have a pretty low centre of gravity, the heads aren't as bulky as DOHC systems, and that keeps the overall engine height lower. The other big enemy is the deep sump used on a lot of these engines. It's effective and cheap, and that's why it gets used, but a switch over to a dry sump can make a substantial difference in centralizing mass.
I'm really keen to see GM's new three valve design. Rumor has it that two cams, twin plugs, and hemispherical chambers will grace H.O. versions of that head/engine. I think if they were to shave the deck height way down, and shorten the stroke, they could build a more oversquare engine that revs like crazy (for a small-block) gets even better mileage at low-rpm, and still has plenty of thrust when you put your foot down. But the real benefit would be in packaging -- the engine would be able to sit extremely low in a chassis while keeping enough of that small-block charm -- lotsa reliability from a relatively unstressed design...
One interesting tech is the rotary valve. It seems that some have finally got it working well enough for commercial use. Less mass, though not critical, since the bottom end is the limiter of modern designs. The real advantage may be that if you can make it work, you can employ some very high compression ratios.
I thought the big point of rotaries is power/weight ratio. What kind of weight and power do these small blocks have?
Remember, it's not just the weight that is the problem, it's weight distribution and the height of center of mass.
Since we're in speculation land, how about the Renesis engine from RX-8. 275lbs which I guess is very little... Splinemodel, how much does 13B-REW weigh? And the associated stock turbos, intercooler and tubing?
Just thinking about a hardcore Renesis two-seater at 1200kg or below. Mazda is already managing to make the MX-5 pretty light despite it being convertible, if they made a coupe, planted the Renesis in there and concentrated on keeping the weight down I think that would be sweet.
1) GM pushrods have better power-to-weight than do most overhead cam engines. However, they require a lot more volume. It makes for some interesting tradeoffs, since you need a larger car to hold it. I'm not sure what the net result is, but the Corvette, GTO, and CTSV are all fairly heavy. Then again, M3's, Porsches, and Ferraris are all pretty fat as well.
2) I think the MSPRE is even less than 275lbs. It is very similar to a keg of beer in size and weight. The REW is similar, but it's a little bit heavier even without the turbo. Regardless, you need an engine crane unless you're hulk hogan, but it just doesn't take much effort even with the cheap hand-crank ones. The turbo, BOV, and etc are pretty insignificant. The stock IC weighs about 10lbs and takes up more space than the other parts of the turbo combined. A good stock-mount aftermarket IC will weigh a little more, and will just manage to squeeze in, but is worth it.
3) For the last year I've been looking into the logistics of transplanting a turbocharged (or electronic hybrid supercharged) MSPRE [renesis] into a Lotus Elise. That's why I talk about them all the time. . . I don't expect it to be cheap, but when you have a car that is tasteful, can hand an Enzo its ass, and costs less than 80k, I think it's justified. Mazda is building the next Miata (2006) on the RX-8 chassis, but it won't have a rotary in it for at least the initial models. Expect it to have the same powerplant that will be in the Mazdaspeed3, which is also coming out soon.
Becomes useful to remind ourselves that an engine is a pump, basically. The small block do require volume, so maybe my small-small-block idea is not feasible, and you don't actually want to build these guys to rev past 7. Modern materials mean that valvetrain ain't the problem these days. Pushrods good for 11-15K rpm exist... I think a variable pressure supercharger could be used with a miller/atkinson cycle, to effectively vary compression and really increase overall mileage, power/displacement ratio. This does add complexity and weight though. I think Mazda tried it once...
With you on Elise. I'd LOVE a weekend at a track with an Exige. One day, if finances and time permits it...
I think a variable pressure supercharger could be used with a miller/atkinson cycle, to effectively vary compression and really increase overall mileage, power/displacement ratio. This does add complexity and weight though. I think Mazda tried it once...
By definition a supercharger is variable pressure. The pressure varies linearly with the engine rpms.
Mazda had a Miller cycle engine in the Millenia S 2.3. Once again, the big complaint was lack of low-end torque, even though the 2.3L in question is a relatively torquey engine. Ultimately, I think that stopped the experiment more than anything else. Several current Mazdas use a newer version of this block that adds direct injection and loses the blower. (hence making it a normal 4 stroke engine).
Was that Mazda engine a 6 ? I don't remember... I any case, with 2.3L it was being asked to move a fairly large car around, and the prevailing weakness of miller/atkinson cycle engines is that they are somewhat lacking in torque. This is where a CVT-like transmission for supercharger could be really useful. It would all have to be programmed right, but you could tell it to really give a lot of boost low down -- if you plant your foot -- and then tail off the boost as revs climb, so you don't blow up the engine. Likewise, if you only open her up part throttle, the supercharger only gives a small amount of boost, and you get the appropriate amount of acceleration (and fuel savings) It might be even simpler to do this with a computer controlled variable vane turbo + intelligent wastegate technology. Would make lotsa fun exhaust noises too!
There are two ways to achieve an atkinson effect, vary exhaust port timing, as most commercial engines do (I think there's a ford or toyota hybrid with this tech.) or actually have a hinged con-rod... icky...
I think we'll see more miller/atkinson motors in hybrid applications. One thing electric motors have is instant torque.
I see a future with lotsa little miller cycle inline 3 or 4 engines mater to electric motor-generators, maybe even boxer twos! Think about it, awesome packaging potential!
I see a future with lotsa little miller cycle inline 3 or 4 engines mater to electric motor-generators, maybe even boxer twos! Think about it, awesome packaging potential!
Ultimately, in hybrid applications a diesel powered turbine should work quite well. It can charge the battery during city driving, and can operate very nicely on the highway. Supposedly, turbines suck down gas, but I feel like there has to be a reason for this that can be easily remedied for this application.
The Smart is doing very well in Europe. Technologically, none of the individual drivetrain bits are really that interesting, even the car as a whole is not really interesting for its technology, except for the safety cage concept. The car is interesting for its philosophy. It is pared down to the essentials of personal urban motoring, it is a scooter on 4 wheels, and that's why it has done so well.
If I were BMW or FIAT, I would remake the Issetta and Cinquecento as more car-like alternatives to the Smart, perhaps not quite Mini's... A little technology, and some time thinking about what city dwellers need could reveal very unique, historically legitimate, and entertaining solutions.
FIAT Cinquecento? REAR engine boxer Twin. With the low centre of mass, and only two cylinders, it would have virtually none of the scary penduluum effect of a rear engine car. In any case, buy a few Porsches, and rip them apart to see how they deal with much heavier lumps hanging off the rear axle. With transmissions, electric motors, and fuel tanks ahead of the engine, enough weight would come forward anyway. Now you have a monospace cockpit where you could seat 2, 3, even 4 people, with leg-room and headroom that belies a micro/small car. The engine only really need run strong enough to cruise at highway speeds and create enough juice for motors to handle acceration and around town...
Rear engine packaging, easy to get at, easy to service. Dead simple, only two cylinders, light-weight exhaust, nice compact low package that is out of the way of the rest of the car...
Issetta. OK, it's got to have regular doors, but let Bangle be as strange as he wants, BMW already has lotsa experience making boxer twins. Liquid cool it, tune for torque/mileage, add electric motor and off you go, same monospace concept... Yes, FWD drop in drivetrains are easy on the assembly line, but RWD drop in rear engine packages should be similarly easy as well...
Imagine cars only about 2 feet longer than a Smart, that carry 4 instead of two...
The Smart is doing very well in Europe. Technologically, none of the individual drivetrain bits are really that interesting, even the car as a whole is not really interesting for its technology, except for the safety cage concept. The car is interesting for its philosophy. It is pared down to the essentials of personal urban motoring, it is a scooter on 4 wheels, and that's why it has done so well.
If I were BMW or FIAT, I would remake the Issetta and Cinquecento as more car-like alternatives to the Smart, perhaps not quite Mini's... A little technology, and some time thinking about what city dwellers need could reveal very unique, historically legitimate, and entertaining solutions.
FIAT Cinquecento? REAR engine boxer Twin. With the low centre of mass, and only two cylinders, it would have virtually none of the scary penduluum effect of a rear engine car. In any case, buy a few Porsches, and rip them apart to see how they deal with much heavier lumps hanging off the rear axle. With transmissions, electric motors, and fuel tanks ahead of the engine, enough weight would come forward anyway. Now you have a monospace cockpit where you could seat 2, 3, even 4 people, with leg-room and headroom that belies a micro/small car. The engine only really need run strong enough to cruise at highway speeds and create enough juice for motors to handle acceration and around town...
Rear engine packaging, easy to get at, easy to service. Dead simple, only two cylinders, light-weight exhaust, nice compact low package that is out of the way of the rest of the car...
Issetta. OK, it's got to have regular doors, but let Bangle be as strange as he wants, BMW already has lotsa experience making boxer twins. Liquid cool it, tune for torque/mileage, add electric motor and off you go, same monospace concept... Yes, FWD drop in drivetrains are easy on the assembly line, but RWD drop in rear engine packages should be similarly easy as well...
Imagine cars only about 2 feet longer than a Smart, that carry 4 instead of two...
It sorrows me that such a package would be an impossibly tough sell in the States, even in dense urban areas.
Why? Because you would be mocked for having such a tiny car, AKA penis.
Imagine cars only about 2 feet longer than a Smart, that carry 4 instead of two...
Smart Fortwo: 2.5m long. Smart Forfour: 3.7m long. It only has a tiny front overhang, there definitely isn't much extra space just laying around... you'd need to cut about 0.5m away from the Forfour to achieve the length you want. Doable?
So do I get this correctly, are you thinking of a rear-engine FWD since you say transmission is in front? Why would you want to run the power to the front when it's best used at the rear wheels?
Ever seen a porsche drivetrain complete but outside of the car? The engine hangs out the back, RWD, and the tranny joins the engine ahead of the rear wheels. The opposite of a mid-engine RWD car where the engine sits ahead of the rear wheels and the tranny hangs off the back.
Maybe you have to go 3 feet longer, I think you could do it with 2.5 feet, or about 30", the forfour is completely conventional front-engine/FWD and is not as packaging efficient as the ForTwo.
I'm talking about a small, compact, low profile engine, mounted out back, driving the rear wheels. Ahead of it, essentially is a monospace that pushes the front passengers way further forward, and puts two more in behind them. Typical crumple zone methodology need not apply. You have to build a stiff shell because there wouldn't be enough room to decelerate through crushing the body. Batteries go behind the front bumper, fuel cells under the rear seat (ahead of the engine) Electric motor is built in-line with the tranny. Works as a starter/motor/generator as per current hybrids. To save money you house it in one casting with the transmission and differential -- everything drives the rear wheels, full stop.
Comments
Originally posted by Matsu
Always thought they were great cars, best of the era of Japanese GT/sports except for two things -- the miserable head room (which also aflicts the RX-8 AFAICT from a brief showroom sampling) and the rotary. Yeah yeah, it's small and light and revs like crazy, but what an awesome car the RX-7 could be with a properly built, light, small-block under the hood... People tend to ignore pushrod engines, and lately GM has seemed to want to build them bigger, but there's little out there that can equal them for HP/pound, overall HWY mileage (considering the HP output), and longevity.
A guy named Jim Labreck, who goes by the name "jimlab" on the RX7 forums, has produced a fair amount of documentation on fitting chevy 350s into the 3rd gen 7. As far as I know, the rationale for the new 6L in the GMs has to do with thee fact that they though 4.0L of V6, and 3.0L of V4, were needed when the cylinders shutdown. Plus, I'm happy with the move, since it ditches the English system. I hate the English system.
I am a big fan of the GM pushrods, but I will say that mazda made the right choice in going rotary. The problem are the twin sequential turbos. A 2.0L, 3 rotor, naturally aspirated rotary would have been much better. A single turbo would have been fine as well. The rotory keeps the car really light, the center of gravity really low, and I think it's the perfect engine for cars that are designed explicitly to perform well around a track. If that's the idea, which it was for the 3rd gen 7, then the rotary makes all sorts of sense.
Anyway, to be more specific, in the WRX I can put down half of the rear bench, fold down the front passenger's seat, and still fit two people and two surfboards.
Anyway, to be more specific, in the WRX I can put down half of the rear bench, fold down the front passenger's seat, and still fit two people and two surfboards.
Look at the Subaru Forrester Turbo as well - more room than a WRX, and it is fastest car 0-30 (faster than a Lambo or Fararri).
Originally posted by Matsu
Always thought they were great cars, best of the era of Japanese GT/sports except for two things -- the miserable head room (which also aflicts the RX-8 AFAICT from a brief showroom sampling) and the rotary. Yeah yeah, it's small and light and revs like crazy, but what an awesome car the RX-7 could be with a properly built, light, small-block under the hood... People tend to ignore pushrod engines, and lately GM has seemed to want to build them bigger, but there's little out there that can equal them for HP/pound, overall HWY mileage (considering the HP output), and longevity.
I thought the big point of rotaries is power/weight ratio. What kind of weight and power do these small blocks have?
Remember, it's not just the weight that is the problem, it's weight distribution and the height of center of mass.
Since we're in speculation land, how about the Renesis engine from RX-8. 275lbs which I guess is very little... Splinemodel, how much does 13B-REW weigh? And the associated stock turbos, intercooler and tubing?
Just thinking about a hardcore Renesis two-seater at 1200kg or below.
I'm really keen to see GM's new three valve design. Rumor has it that two cams, twin plugs, and hemispherical chambers will grace H.O. versions of that head/engine. I think if they were to shave the deck height way down, and shorten the stroke, they could build a more oversquare engine that revs like crazy (for a small-block) gets even better mileage at low-rpm, and still has plenty of thrust when you put your foot down. But the real benefit would be in packaging -- the engine would be able to sit extremely low in a chassis while keeping enough of that small-block charm -- lotsa reliability from a relatively unstressed design...
One interesting tech is the rotary valve. It seems that some have finally got it working well enough for commercial use. Less mass, though not critical, since the bottom end is the limiter of modern designs. The real advantage may be that if you can make it work, you can employ some very high compression ratios.
Originally posted by Gon
I thought the big point of rotaries is power/weight ratio. What kind of weight and power do these small blocks have?
Remember, it's not just the weight that is the problem, it's weight distribution and the height of center of mass.
Since we're in speculation land, how about the Renesis engine from RX-8. 275lbs which I guess is very little... Splinemodel, how much does 13B-REW weigh? And the associated stock turbos, intercooler and tubing?
Just thinking about a hardcore Renesis two-seater at 1200kg or below.
1) GM pushrods have better power-to-weight than do most overhead cam engines. However, they require a lot more volume. It makes for some interesting tradeoffs, since you need a larger car to hold it. I'm not sure what the net result is, but the Corvette, GTO, and CTSV are all fairly heavy. Then again, M3's, Porsches, and Ferraris are all pretty fat as well.
2) I think the MSPRE is even less than 275lbs. It is very similar to a keg of beer in size and weight. The REW is similar, but it's a little bit heavier even without the turbo. Regardless, you need an engine crane unless you're hulk hogan, but it just doesn't take much effort even with the cheap hand-crank ones. The turbo, BOV, and etc are pretty insignificant. The stock IC weighs about 10lbs and takes up more space than the other parts of the turbo combined. A good stock-mount aftermarket IC will weigh a little more, and will just manage to squeeze in, but is worth it.
3) For the last year I've been looking into the logistics of transplanting a turbocharged (or electronic hybrid supercharged) MSPRE [renesis] into a Lotus Elise. That's why I talk about them all the time. . . I don't expect it to be cheap, but when you have a car that is tasteful, can hand an Enzo its ass, and costs less than 80k, I think it's justified. Mazda is building the next Miata (2006) on the RX-8 chassis, but it won't have a rotary in it for at least the initial models. Expect it to have the same powerplant that will be in the Mazdaspeed3, which is also coming out soon.
With you on Elise. I'd LOVE a weekend at a track with an Exige. One day, if finances and time permits it...
Originally posted by Matsu
I think a variable pressure supercharger could be used with a miller/atkinson cycle, to effectively vary compression and really increase overall mileage, power/displacement ratio. This does add complexity and weight though. I think Mazda tried it once...
By definition a supercharger is variable pressure.
Mazda had a Miller cycle engine in the Millenia S 2.3. Once again, the big complaint was lack of low-end torque, even though the 2.3L in question is a relatively torquey engine. Ultimately, I think that stopped the experiment more than anything else. Several current Mazdas use a newer version of this block that adds direct injection and loses the blower. (hence making it a normal 4 stroke engine).
There are two ways to achieve an atkinson effect, vary exhaust port timing, as most commercial engines do (I think there's a ford or toyota hybrid with this tech.) or actually have a hinged con-rod... icky...
I think we'll see more miller/atkinson motors in hybrid applications. One thing electric motors have is instant torque.
I see a future with lotsa little miller cycle inline 3 or 4 engines mater to electric motor-generators, maybe even boxer twos! Think about it, awesome packaging potential!
Originally posted by Matsu
I see a future with lotsa little miller cycle inline 3 or 4 engines mater to electric motor-generators, maybe even boxer twos! Think about it, awesome packaging potential!
Ultimately, in hybrid applications a diesel powered turbine should work quite well. It can charge the battery during city driving, and can operate very nicely on the highway. Supposedly, turbines suck down gas, but I feel like there has to be a reason for this that can be easily remedied for this application.
If I were BMW or FIAT, I would remake the Issetta and Cinquecento as more car-like alternatives to the Smart, perhaps not quite Mini's... A little technology, and some time thinking about what city dwellers need could reveal very unique, historically legitimate, and entertaining solutions.
FIAT Cinquecento? REAR engine boxer Twin. With the low centre of mass, and only two cylinders, it would have virtually none of the scary penduluum effect of a rear engine car. In any case, buy a few Porsches, and rip them apart to see how they deal with much heavier lumps hanging off the rear axle. With transmissions, electric motors, and fuel tanks ahead of the engine, enough weight would come forward anyway. Now you have a monospace cockpit where you could seat 2, 3, even 4 people, with leg-room and headroom that belies a micro/small car. The engine only really need run strong enough to cruise at highway speeds and create enough juice for motors to handle acceration and around town...
Rear engine packaging, easy to get at, easy to service. Dead simple, only two cylinders, light-weight exhaust, nice compact low package that is out of the way of the rest of the car...
Issetta. OK, it's got to have regular doors, but let Bangle be as strange as he wants, BMW already has lotsa experience making boxer twins. Liquid cool it, tune for torque/mileage, add electric motor and off you go, same monospace concept... Yes, FWD drop in drivetrains are easy on the assembly line, but RWD drop in rear engine packages should be similarly easy as well...
Imagine cars only about 2 feet longer than a Smart, that carry 4 instead of two...
Originally posted by Matsu
The Smart is doing very well in Europe. Technologically, none of the individual drivetrain bits are really that interesting, even the car as a whole is not really interesting for its technology, except for the safety cage concept. The car is interesting for its philosophy. It is pared down to the essentials of personal urban motoring, it is a scooter on 4 wheels, and that's why it has done so well.
If I were BMW or FIAT, I would remake the Issetta and Cinquecento as more car-like alternatives to the Smart, perhaps not quite Mini's... A little technology, and some time thinking about what city dwellers need could reveal very unique, historically legitimate, and entertaining solutions.
FIAT Cinquecento? REAR engine boxer Twin. With the low centre of mass, and only two cylinders, it would have virtually none of the scary penduluum effect of a rear engine car. In any case, buy a few Porsches, and rip them apart to see how they deal with much heavier lumps hanging off the rear axle. With transmissions, electric motors, and fuel tanks ahead of the engine, enough weight would come forward anyway. Now you have a monospace cockpit where you could seat 2, 3, even 4 people, with leg-room and headroom that belies a micro/small car. The engine only really need run strong enough to cruise at highway speeds and create enough juice for motors to handle acceration and around town...
Rear engine packaging, easy to get at, easy to service. Dead simple, only two cylinders, light-weight exhaust, nice compact low package that is out of the way of the rest of the car...
Issetta. OK, it's got to have regular doors, but let Bangle be as strange as he wants, BMW already has lotsa experience making boxer twins. Liquid cool it, tune for torque/mileage, add electric motor and off you go, same monospace concept... Yes, FWD drop in drivetrains are easy on the assembly line, but RWD drop in rear engine packages should be similarly easy as well...
Imagine cars only about 2 feet longer than a Smart, that carry 4 instead of two...
It sorrows me that such a package would be an impossibly tough sell in the States, even in dense urban areas.
Why? Because you would be mocked for having such a tiny car, AKA penis.
Originally posted by Matsu
Imagine cars only about 2 feet longer than a Smart, that carry 4 instead of two...
Smart Fortwo: 2.5m long. Smart Forfour: 3.7m long. It only has a tiny front overhang, there definitely isn't much extra space just laying around... you'd need to cut about 0.5m away from the Forfour to achieve the length you want. Doable?
Check out the Forfour here:
www.thesmart.co.uk/
BTW, Imperial units are yucky. Use proper ones.
Maybe you have to go 3 feet longer, I think you could do it with 2.5 feet, or about 30", the forfour is completely conventional front-engine/FWD and is not as packaging efficient as the ForTwo.
I'm talking about a small, compact, low profile engine, mounted out back, driving the rear wheels. Ahead of it, essentially is a monospace that pushes the front passengers way further forward, and puts two more in behind them. Typical crumple zone methodology need not apply. You have to build a stiff shell because there wouldn't be enough room to decelerate through crushing the body. Batteries go behind the front bumper, fuel cells under the rear seat (ahead of the engine) Electric motor is built in-line with the tranny. Works as a starter/motor/generator as per current hybrids. To save money you house it in one casting with the transmission and differential -- everything drives the rear wheels, full stop.