So I've been researching the slc for years. I have to build it myself and I just don't have the time and it's killing me.
So I just randomly popped on the board today and saw the new transaxle that is available, which is amazing btw.
So I was just randomly zoning out while watching TV and thinking about high rpm engines and their benefits. I see a lot of talk of building a high RPM small block, I actually thought of building one myself one day for the slc.
Now I think I had a bit of a revelation in my theoretical build. I have to admit, I did work on a car in my garage today, and the exhaust vent hose slipped off the exhaust pipe, and I didn't notice it for a very long time, so I could possibly be out of my mind.
Is there no point to building a high rpm lsx for these cars? I mean, do people even know why they want an engine to rev high? I think people just associate high revving engines with racing. Or think the powerband might be more manageable when the engine is not making "low end torque" so to speak.
After some thought, something which I've known for awhile, the only real reason any race cars, sports bikes, any car for that matter opt for a high rpm engine, is simply because torque requires more metal. Lets take a 600cc sport bike, 130hp, 17,000 rpm. Without tracking down a dyno graph, just using ol 5250 to estimate, that's probably around 40ft lbs of torque, which allows you to use extremely small and lightweight drivetrain components.
Now why many of you probably already knew this, did we ever think about the purpose of a high revving v8? I mean I really don't think people that want these are simply trying to do so to make use of a lighter transaxle. If you're using say a graziano rated for 600ft lbs (probably conservative), why would you want your ls2, or whatever base you are using to actually rev higher if you aren't coming close to it's torque limitations.
Now say if you want to argue the old traction debate. A high rpm motor will have more traction since the the lack of low end torque doesn't hit you like a brick wall every time you touch the throttle, and you can actually control the car on corner exits. Without driving one, I would imagine it's probably the biggest downside to owning an slc with a SBC. Torque madness.
That is all very true and a good argument. The problem is, I see people spending huge sums of money for high rpm lsx's to solve this problem. It's certainly not cheap to decrease the rotational mass and the entire valve train. I think there is a very cheap way to solve this.
There are plenty of ways to make serious power on a budget with these ls motors. 500hp is pretty cheap. 500hp and 8000 rpm is not. The difference between the two just being the powerband.
Then I had a thought, in order to make something lightweight like an slc more controllable with a torque monster like an lsx, why not simply limit the torque down low with some sort of variable air restrictor. I would think that would be pretty darn easy to design. It will be mostly unheard of since it is actually taking power away from the car. (not many cars have the power:weight ratio of an slc)
For example, if you had say a 500hp lsx, only rev's to 6000rpm. Which would mean torque is around 500 as well. Why not just cut the air flow at lower rpms. Essentially you could easily have any torque curve you wanted. In essence, you might even be able to take the dyno graph from your favorite car, and tune the restrictor to mirror the line on the graph. If you took that lsx and it's theoretical 400ft lbs of torque at 2000rpm, and turned that into 325ft lbs of torque using your restrictor, and simply kept gradually increasing the torque throughout the rev range, you engine would essentially just have the behavior of your favorite high rpm screamer.
This idea really only works for cars like the slc since the people building the engines and pairing the transaxles are not race teams or car companies. There are limited drivetrain selections. In some of the higher end builds, someone might be tailoring the engine to maximize the lightest drivetrain possible, but not in most home built cars. The point of this car is to keep in on a budget. Also the slc is in a very rare class as far as power:weight ratios go. In most cars more power at any rpm would likely lead to more fun. In the SLC, and other cars with ridiculous power to weight ratios, the power band can make or break your experience and/or lap time.
cliff notes:variable air restrictor, or probably just an electronic throttle body, tuned for less power at low rpm, could make the car far more enjoyable to drive, and faster on a track, and significantly reduce the cost and need of a high rpm build everyone so desires.
Anyway, where I come up short is the actual implementation of such a thing. While I have rebuilt a few engines, work on my own cars, done a little racing, and a little ecu tuning, I am for the most part a keyboard racer, and you guys would probably have a better idea if such a design would work.
So I just randomly popped on the board today and saw the new transaxle that is available, which is amazing btw.
So I was just randomly zoning out while watching TV and thinking about high rpm engines and their benefits. I see a lot of talk of building a high RPM small block, I actually thought of building one myself one day for the slc.
Now I think I had a bit of a revelation in my theoretical build. I have to admit, I did work on a car in my garage today, and the exhaust vent hose slipped off the exhaust pipe, and I didn't notice it for a very long time, so I could possibly be out of my mind.
Is there no point to building a high rpm lsx for these cars? I mean, do people even know why they want an engine to rev high? I think people just associate high revving engines with racing. Or think the powerband might be more manageable when the engine is not making "low end torque" so to speak.
After some thought, something which I've known for awhile, the only real reason any race cars, sports bikes, any car for that matter opt for a high rpm engine, is simply because torque requires more metal. Lets take a 600cc sport bike, 130hp, 17,000 rpm. Without tracking down a dyno graph, just using ol 5250 to estimate, that's probably around 40ft lbs of torque, which allows you to use extremely small and lightweight drivetrain components.
Now why many of you probably already knew this, did we ever think about the purpose of a high revving v8? I mean I really don't think people that want these are simply trying to do so to make use of a lighter transaxle. If you're using say a graziano rated for 600ft lbs (probably conservative), why would you want your ls2, or whatever base you are using to actually rev higher if you aren't coming close to it's torque limitations.
Now say if you want to argue the old traction debate. A high rpm motor will have more traction since the the lack of low end torque doesn't hit you like a brick wall every time you touch the throttle, and you can actually control the car on corner exits. Without driving one, I would imagine it's probably the biggest downside to owning an slc with a SBC. Torque madness.
That is all very true and a good argument. The problem is, I see people spending huge sums of money for high rpm lsx's to solve this problem. It's certainly not cheap to decrease the rotational mass and the entire valve train. I think there is a very cheap way to solve this.
There are plenty of ways to make serious power on a budget with these ls motors. 500hp is pretty cheap. 500hp and 8000 rpm is not. The difference between the two just being the powerband.
Then I had a thought, in order to make something lightweight like an slc more controllable with a torque monster like an lsx, why not simply limit the torque down low with some sort of variable air restrictor. I would think that would be pretty darn easy to design. It will be mostly unheard of since it is actually taking power away from the car. (not many cars have the power:weight ratio of an slc)
For example, if you had say a 500hp lsx, only rev's to 6000rpm. Which would mean torque is around 500 as well. Why not just cut the air flow at lower rpms. Essentially you could easily have any torque curve you wanted. In essence, you might even be able to take the dyno graph from your favorite car, and tune the restrictor to mirror the line on the graph. If you took that lsx and it's theoretical 400ft lbs of torque at 2000rpm, and turned that into 325ft lbs of torque using your restrictor, and simply kept gradually increasing the torque throughout the rev range, you engine would essentially just have the behavior of your favorite high rpm screamer.
This idea really only works for cars like the slc since the people building the engines and pairing the transaxles are not race teams or car companies. There are limited drivetrain selections. In some of the higher end builds, someone might be tailoring the engine to maximize the lightest drivetrain possible, but not in most home built cars. The point of this car is to keep in on a budget. Also the slc is in a very rare class as far as power:weight ratios go. In most cars more power at any rpm would likely lead to more fun. In the SLC, and other cars with ridiculous power to weight ratios, the power band can make or break your experience and/or lap time.
cliff notes:variable air restrictor, or probably just an electronic throttle body, tuned for less power at low rpm, could make the car far more enjoyable to drive, and faster on a track, and significantly reduce the cost and need of a high rpm build everyone so desires.
Anyway, where I come up short is the actual implementation of such a thing. While I have rebuilt a few engines, work on my own cars, done a little racing, and a little ecu tuning, I am for the most part a keyboard racer, and you guys would probably have a better idea if such a design would work.