Hello Barry,
The responses are inserted in the following questions. ----- Original Message ----- From: Barry Oppenheim via EV<mailto:[email protected]> To: 'Electric Vehicle Discussion List'<mailto:[email protected]> Sent: Monday, December 01, 2014 10:20 AM Subject: Re: [EVDL] Converting with an Automatic Transmission Wayne wrote: "I built a lot of automatic conversions, its no big thing..." Wayne, Couple questions on your response. You mentioned that you have experimented with different torque converters and generally keep the stock TC. Can you elaborate on how automatic shifting performs given the torque curve on electric motors is different than the ICE torque curve? ** The standard stock TC had a higher lock up rpm over 3000 rpm for my existing engine. The 12 inch diameter TC recommended by TCI.com has a full lock up at 1700 rpm. The 11 inch WarP motor has its sweet spot rpm and torque at about 1800 rpm. The sweet spot according Net Gain is where the maximum hp and torque at 1800 rpm. ** In a 9 inch WarP motor the sweet spot is above 3000 rpm. Matching the full lock up to the sweet rpm is ideal. How do you determine what parameters (RPM/gear) to use when adjusting the shift points electronically with an aftermarket computer? ** There is no computer control for this transmission which is a GM-TH400 automatic converted to a manual. ** I use a large face tachometer right in front of me. The tachometer is converted by a program circuit in the Café Electric motor controller that has Motor amps On Tack Mode or you could use a amp meter with a shunt that is place in the output feeder wire to the motor. ** Every 1000 rpm on the motor is equal to 100 motor amps Have you tried without an idling circuit/EVTronics controller (just manually idling, with brake applied, in order to build up pump pressure)? ** Yes, You could start out without the idling control, but you have to push the accelerator peddle very lightly, but there is a little thrust when do that. For me, it is better to turn on the idle control and let the motor come up to speed where the EV will just barely move. I then at that time, increase the accelerator pressure to accelerated up to speed and then I may turn off the idle control, so the EV motor ampere will go to 0 ampere while coasting down during the drive. ** If I come to a quick stop and go, then I will not turn the idle control on, as the transmission oil pressure is still up. I am using a transmission oil gage to monitor the oil pressure. The transmission oil pressure can drop as low as 100 psi with no problems. The oil range pressure in a GM-TH400 transmission is normally from 100 to 200 psi to start moving. This is also depends on the overall gear ratio you are in. The higher overall gear ratio you are in, the lower oil pressure it takes to start moving. When using a stock transmission and TC how does the vehicle perform using manual shifting of the automatic? ** When using a stock transmission in automatic mode, the sweet spot of the motor rpm may not match transmission rpm at each shift point, which will reduce the performance of the EV, meaning more increase motor ampere which was true in my case. We had a standard GM-TH350 with a standard TC and we worn the transmission clutch pack in with a 1000 miles. There was too much thrust on take off. This was back when transmission was not computer control or the user did not have any indications of the rpm to sweet spot to motor ampere. Thoughts on lockup vs non-lockup converters? ** You could talk to TCI.com to verified the following statement. A torque converter is also rated in ratio like a overall gear ratio. Torque converters are normally rated from 1.7:1 to 1.8:1 ratio. If a torque converter is not rotating, it is consider at a ratio of 1.7 to 1.8 ratio. As the rpm of the TC is increase, the ratio decreases to 0.0:1 or may be just a little more than 0 which is close to full lock up. You want to be able to shift the transmission right at or about this 0.0:1 ratio of the transmission. ** For example: Starting out with my manual transmission that had a first gear ratio of 3.5:1 and a differential ratio of 5.57:1 gives a overall ratio of 19.495:1. Even with this high ratio, the starting thrust of the motor ampere would go to about 500 ampere. If I came to a quick stop and go, to prevent this high motor ampere start up, I would shift the transmission into neutral to prevent the motor to go down to 0 rpm. Leaving the motor above 1000 or 2000 rpm and gently easing off on the clutch, I can reduce my motor ampere. With the automatic transmission in manual mode, turn on the idle control, allows some oil pressure increase where it cushions the thrust. I now can start to accelerate moving very slowly with a motor ampere down to 50 amps. A lot of times, I may want to mover the EV around in my my garage a bit, I just first put the gear (I normally leave it in gear while parking) and by just turning on the Idle Control Switch, I can move the EV around with out pressing the accelerator pedal. ** The idle control is ideal when I take the EV to a shop to have alignment work or some other mechanical work done. I tell them to put the transmission in gear first and than turn on the idle control to move the EV around. Roland Thanks in advance, Barry _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub<http://www.evdl.org/help/index.html#usub> http://lists.evdl.org/listinfo.cgi/ev-evdl.org<http://lists.evdl.org/listinfo.cgi/ev-evdl.org> For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA<http://groups.yahoo.com/group/NEDRA>) -------------- next part -------------- An HTML attachment was scrubbed... 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