Fully electric S2K!
Registered User
Joined: Oct 2000
Posts: 15,323
Likes: 28
From: Longmont, CO
Originally Posted by bblocher' date='Jan 21 2009, 12:41 PM
Hey guys. I noticed the S2KEV got quiet a bit of attention both positive and negative so thought I'd chime in and answer any questions I could.
I have a question about the use of the stock transmission - I haven't read up on anybody else's EV conversions, so was wondering if it's common to go that route? With an ICE, when upshifting during daily driving the engine speed typically drops when the throttle is closed an appropriate amount for the next higher gear. How does the electric motor behave when you take your foot off the gas^H^H^H accelerator pedal? If there's a big speed discrepancy between the electric motor speed and the transmission input shaft speed, I'd imagine that putting a lot of strain on everything when you release the clutch.
How sophisticated are your engineering skills? If you put in a gear selection sensor, combined with your vehicle speed info and electric motor speed info, you could program the electric motor's controller to automatically spin the motor up or down to the appropriate speed for whichever gear you've selected while the clutch is disengaged. You'd get perfect "throttle blip" downshifts (ala the new 370Z) and perfect, zero-strain upshifts.
(In fact, with sensitive enough sensors on the gear shift lever, you can do away with using the clutch entirely except for starting from a standstill.)
Registered User
Joined: Jan 2009
Posts: 17
Likes: 0
Originally Posted by Elistan' date='Jan 21 2009, 11:58 AM
I was wondering if you'd be stopping in.
I have a question about the use of the stock transmission - I haven't read up on anybody else's EV conversions, so was wondering if it's common to go that route? With an ICE, when upshifting during daily driving the engine speed typically drops when the throttle is closed an appropriate amount for the next higher gear. How does the electric motor behave when you take your foot off the gas^H^H^H accelerator pedal? If there's a big speed discrepancy between the electric motor speed and the transmission input shaft speed, I'd imagine that putting a lot of strain on everything when you release the clutch.
How sophisticated are your engineering skills? If you put in a gear selection sensor, combined with your vehicle speed info and electric motor speed info, you could program the electric motor's controller to automatically spin the motor up or down to the appropriate speed for whichever gear you've selected while the clutch is disengaged. You'd get perfect "throttle blip" downshifts (ala the new 370Z) and perfect, zero-strain upshifts.
(In fact, with sensitive enough sensors on the gear shift lever, you can do away with using the clutch entirely except for starting from a standstill.)
I have a question about the use of the stock transmission - I haven't read up on anybody else's EV conversions, so was wondering if it's common to go that route? With an ICE, when upshifting during daily driving the engine speed typically drops when the throttle is closed an appropriate amount for the next higher gear. How does the electric motor behave when you take your foot off the gas^H^H^H accelerator pedal? If there's a big speed discrepancy between the electric motor speed and the transmission input shaft speed, I'd imagine that putting a lot of strain on everything when you release the clutch.
How sophisticated are your engineering skills? If you put in a gear selection sensor, combined with your vehicle speed info and electric motor speed info, you could program the electric motor's controller to automatically spin the motor up or down to the appropriate speed for whichever gear you've selected while the clutch is disengaged. You'd get perfect "throttle blip" downshifts (ala the new 370Z) and perfect, zero-strain upshifts.
(In fact, with sensitive enough sensors on the gear shift lever, you can do away with using the clutch entirely except for starting from a standstill.)
I'm keeping the clutch to allow for fast shifting. The electric motor when I let off the accelerator will continue spinning but rev down (at a slower rate than an ICE). The close ratio of our tranny makes it nice so the synchros shouldn't have much work to do here especially since the motor spins so freely.
There will be less strain when releasing the clutch here. With the ICE you can down shift and really fell the compression of the engine slowing you down. There is no back pressure with an electric motor. If I down shift and release the clutch the motor will quickly just match the speed. These are series wound electric motors. A typical electric motor that many are use to has permanent magnets that make them hard to turn until electricity is applied. When I cut the power to this motor it free spins quiet easily making coasting great but I loose my down shift braking.
Brian
Registered User
Joined: Jan 2009
Posts: 17
Likes: 0
I just wanted to throw in another bit of info. My people think EVs are slow but reality is they will smoke an ICE setup anyday. You can't compare a high perf ICE with an economy EV setup which is what most people see.
If I had the money I would have went high end on the motor/controller side and I still may down the road when I can save up for it. You can buy some crazy setups that will blow away the most expesive exotic car.
Do youtube searching on electric vehicle racing.
This guy has a sleeper. Funny to watch this thing.
http://www.youtube.com/watch?v=zp_jwE0KdOk
If I had the money I would have went high end on the motor/controller side and I still may down the road when I can save up for it. You can buy some crazy setups that will blow away the most expesive exotic car.
Do youtube searching on electric vehicle racing.
This guy has a sleeper. Funny to watch this thing.
http://www.youtube.com/watch?v=zp_jwE0KdOk
Registered User
Joined: Feb 2008
Posts: 2,809
Likes: 0
From: Laurel
Originally Posted by frofro24' date='Jan 20 2009, 10:23 PM
Electric motors often make up for low horsepower numbers with torque. I could easily see this motor making torque than a stock F20/F22.
Registered User
Joined: Jan 2009
Posts: 17
Likes: 0
Originally Posted by ECale3' date='Jan 21 2009, 12:40 PM
Ha! The prius motor makes more torque than the F22C (192 lb/ft IIRC)
Joined: Mar 2006
Posts: 3,426
Likes: 5
From: Royal Oak, Michigan
Originally Posted by bblocher' date='Jan 21 2009, 10:41 AM
Somebody mentioned why use the original tranny. Tesla has 1 and 2 speed tranny. They are using an AC motor that can rev to something like 13k, this mixed with the torque makes it possible to use the single speed. My DC motor can only rev to 7k but is most efficient around 4-5k so more gears are needed....
Electric works opposite of ICE engines. With electric you keep your RPMs low to get amazing torque, with ICE you need to rev it up to that sweet spot first. So the six speed might come in handy here. Just like it allows the original ICE to stay in that sweet higher RPM range I should be able to use it stay in the sweet lower RPM range if I want my best acceleration.
Brian
Electric works opposite of ICE engines. With electric you keep your RPMs low to get amazing torque, with ICE you need to rev it up to that sweet spot first. So the six speed might come in handy here. Just like it allows the original ICE to stay in that sweet higher RPM range I should be able to use it stay in the sweet lower RPM range if I want my best acceleration.
Brian
I don't understand this. If the electric motor makes as much torque as it appears (at such low rpm with corresponding little power at higher revs), the extra gears are not going to be helpful at all. You are not gonna be able to effectively use gears 1-4. You're gonna want to start from a stop in 5 or 6, then you're gonna be wishing for a 7th and 8th gear after that.
Are you going to change the final drive ratio to compensate for this?
Good luck to you, I hope your project meets your expectations!
Regards,
Kamron
Joined: Jul 2008
Posts: 933
Likes: 74
Originally Posted by bblocher' date='Jan 21 2009, 02:41 PM
Hey guys. I noticed the S2KEV got quiet a bit of attention both positive and negative so thought I'd chime in and answer any questions I could.
Brian
Brian
I hope to see you on a drive some day, and good luck!