mrfred

iTrader: (50)

That looks like a pretty reasonable height in the rear. Are they height adjustable, or is it just preload adjustable? If you have 500 lb/in springs, another 125 lbs of battery would only drop the rear by ~0.2" (accounting for motion ratio).

detroit pistins

iTrader: (102)

Why did you order it from Tesla?

electron bom

iTrader: (17)

Safety Items
for the motor controller and battery

PMPN8EZ

Severe death. Is there any other kind?

BluEVOIX

iTrader: (69)

Having reached this point now, is there anything differently you would have done knowing then what you know now ?

electron bom

iTrader: (17)

Good question. If I could do it all over again, I wouldn't start with a salvaged Evo. I estimate that, if I had bought a perfectly working or a clean parted-out Evo chassis, I could have saved well over $5000 and about 6-8 months of work.

That Siemens motor is nice, but it would be more appropriate for a long distance highway-car. My setup is a grocery-getter and around-town gokart. Gokarts should be fast and relatively inexpensive. As such, there is no cost-benefit to an AC powerplant for my purposes. That Siemens motor with a DMOC controller/inverter is $5,000 for 118kW peak power. My DC motor and controller setup was $3500 for 160kW peak power. When I add a second motor, my motor/controller setup will total $7500 and should be capable of 500ftlbs. To get 500ftlbs from an AC setup would require dual stack Remy 250-90 Hairpin PM motors with twin Reinhart 150kW controllers, which costs in the neighborhood of $34,000. Also, the Remy motors wont mate with an Evo transmission.



The Remy 250-90 PM dual stack motor is an amazing thing.

electron bom

iTrader: (17)

I doubt that I'll ever remove the transmission. There are just too many good reasons to keep the transmission and avoid direct drive:

1. Direct drive has no true neutral; the motors are always connected to the drive wheels. If the motor controllers fail in an 'ON' position, then you have no recourse to stop the vehicle except for melting your brakes.

2. Direct drive means only one drive ratio. Electric motors have rpm & load dependant efficiency curves. Losing the option to shift into the efficiency zone means wasting energy.

3. Direct drive does not afford the option of mechanical grip from a center differential. Delete the gearbox in an Evo and you lose the center diff. If the vehicle is a single motor setup, then AWD is also lost.

4. Direct drive reduces driver control of the vehicle. A manual gearbox allows the driver to match road speed with motor speed.
The quickest, fastest, and most sporty electric vehicle in the world, the Rimac Concept One, uses a 2 speed dual clutch transmission. The quickest, fastest, and most sporty DC electric conversion road-vehicle, the EV West M3, also uses a 2 speed transmission.



Rimac Concept One, AWD, four-motor, rated at 1MW power (~1340hp)





EV West M3, RWD, Pikes Peak Racecar, twin 11" DC motors, 800-1100ish wtq

electron bom

iTrader: (17)

my new favorite safety item

BluEVOIX

iTrader: (69)

But arent those the the values for what ever they are rated at continuous or 1 hour etc... ? If true then cant we just pump more voltage, amperage and watts etc.. with the correct controller/battery setup to get even more short bursts of power on an AC setup? Not necessarily having to beat the volt per volt kw power or hp with AC vs DC but just make more power than rated ? Plus with the AC you get the regenerative braking.

1. Wouldn't a kill switch within reach of the driver take care of that ?

2. But Tesla is single gear. Thats what gets me thinking perhaps with AC motors that supposedly make less torque but have a more flat power curve might get away with it. Well at least thats what I think I understand from the the bits and pieces I’ve been reading.

3. Well with the dual motor setup we will still be AWD and not waste power trying to spin addition transmission, tcase, drive shaft parts. One motor in the rear diff, a second motor added to the front (with a EVO rear diff installed). We can even maybe turn off one controller and make it a RWD or Front Wheel Drive evo if needed to extend range slightly . Even for those non long distance driven EV.

4. Again I have to pull the Tesla card on this. They are making it happen with single gear why cant we ? Unless their motor is that much more superior over what is currently available for EV conversions ?

I’ve seen the M3 and there is also the Zombie 222 Mustang making 1800 wtq . They use the Gear Venders overdrive unit as its transmission . Your right about Rimac trying to make a direct drive supercar that has a separate motor for each wheel. It's because they see the benefits of removing the rest of the drivetrain. Though their setup will be more advance controlling power to each wheel for maximizing its cornering ability , the Evo can still be good with front and rear LSD.

I would love to do an EV conversion on my EVO as well but only with deleting the transmission and tcase. The things that hold me back is the uncertaintity about direct gear twin motor front and rear can work. That and the battery prices need to keep coming down!

Not trying to start a huge debate . Just sharing and throwing some ideas/thoughts. Thanks for sharing your input.

electron bom

iTrader: (17)

The manufacturer's continuous (1 hr) rating for the Warp 9 is 35kW. Based on individual testing, Warp 9 peak numbers are around 160kW for 20 seconds and as much as 220kW for 10 seconds. The Siemens motor you like is rated at 47kW continuous, but users have been able to extract as much as 120kW (or more) for brief periods.

Sure, but I'm not interested in passing 1000A through the cabin for this purpose.
I can open my main contactor from the cabin and kill power to the controller, but if there is a failure at the contactor then a true neutral is nice to have as redundancy.

Tesla AC motors make over 500hp, spin up to 18,000 rpm, and go for $12,000 used.
My DC motor makes 200hp, spins to 6,000rpm, and goes for $900 used.
It is like comparing Michael Phelps to my 2 y/o niece and then questioning why she needs arm floats to do a lap in the pool. Its pointless to compare the two.

Your idea of a twin motor setup is intriguing. I think mating a motor to the rear diff would be very difficult and probably cost you the rear seat. With enough money anything is possible, but I'm not aware of any torque vectoring software available for individual enthusiasts, nor a controller to run such software.

Tesla makes a 700hp/700tq car that falls on its face at 120mph and can't do a lap of most international race circuits without overheating. That is the limitation of an 18,000 rpm motor with a single drive ratio in a 4800lb car. Not bad at all really, but it's quite clearly not optimized for that type of driving. But why should it be? That is not the P85D's target market.

I welcome the conversation and conjecture. It seems you have a lot of ideas and questions. If you are planning a build and have further questions about details, I'm happy to answer them to the best of my ability. Just shoot me a PM so we're not derailing my build thread.

evoforstevo

iTrader: (15)

Loving the conversation, maybe a new thread in the general would be appropriate? Don't want to miss out due to PMs.

yellowevo82

iTrader: (100)

I dunno how you did this , still. Or how you know to make all this work . Still very impressed. Nobody is going to top or match this build. Very creative!!

deeman101

iTrader: (34)

Electron bom, I respect what you've done so far and have been an avid follower. I'm going to play devil's advocate to you though just to satisfy my curiosity.

You can use a solid state kill switch with a remote actuator.


In a sense, the awd teslas are really a non-traditional 2 speed setup. Each motor is coupled to a single ratio, but the front has a taller ratio than the rear. So really its maximizing its torque spread over a wider range of speed (low speeds favor the rear motor, high speeds favor the front motor). You could potentially emulate something similar. Also, remember than you don't have to stick with the evo rear diff (at least the USDM don't have torque vectoring anyways). You can use whatever diff you want and flip it around so that the motor sits where the trunk pan currently is. Something like a porsche front differential in the rear of the car will achieve this. You have a lot of batteries there right now anyways, just need to reorganize around a custom motor hump. You can also use a rear differential at the front for the same purpose. And hopefully you could find a diff with the correct ratio to match the speed range you desire for the front and rear.



I'm not sure of the warp9s in specific, but I know at least for the Remy motor you had linked they actually have a rather broad "power band". Something like 0-5000rpm. I guess it kind of depends on you and how much torque at the wheels / how fast you want your top speed to be to decide if you can make a 0-5000rpm powerband work for you or not. And I guess also on the warp9 engine's capability which I'm not familiar with.

It does seem though that you are taking a lot of efficiency loss through the stock drivetrain and allowing for many points of potential failure in the drivetrain especially considering your high torque motor. Ultimately you're probably doing this cause its the easiest way (barring that custom adapter plate) to get the thing on the street. But I think theres a lot of room for optimization still left on the table. Just my 2 cents.

electron bom

iTrader: (17)

I've already built and quite thoroughly tested a single gear EV. It had a torque to weight ratio of about 1:9. What I learned from that build has been used in this Evo project. Some of my observations from that build:

-In order to overcome the vehicle's inertia, the motor controller had to pull unacceptably high current from the battery which: increased motor temp, increased controller temp, increased commutator/brush wear, decreased range, and decreased overall efficiency.
-To hit the vehicle's intended top speed, I had to spin the crap out of the motor which: increased back EMF, increased motor temp, and decreased efficiency.
-Thus, I had to play the balancing act of top speed vs low end torque all while minimizing losses to thermal inefficiencies. To achieve a decent balance, I varied my drive and driven gear ratio (went through about 6 or 7 different combinations). I was never totally satisfied with the motor's performance, which was the top of its class but also a budget-conscious purchase. I either had to sacrifice low end grunt for a satisfactory top speed or accept a relatively low top speed for exciting off-the-line acceleration. Adding just one more forward gear would have drastically increased vehicle performance, even when accounting for transmission losses.

*It's worthwhile to note that the motor/controller package for my single gear vehicle cost around $1100. If I had been willing to spend $6000 on a motor/controller package, I would have likely been pleased with vehicle performance despite the single gear. In the end, budget is the limiting factor. If budget wasn't a concern, I'd walk right into the Mercedes F1 team and hire them to build an electric powerplant for my Evo

A single gear is a hugely limiting factor, especially when coupled with a motor that makes all its power in a restricted rpm range (consider the necessity of multiple gears in diesel semi-trucks). A 5 speed transmission is a relatively inexpensive means to increase motor usability, increase vehicle range, decrease system operating temp, and retain AWD. Tesla really is the benchmark for EVs, so I completely understand the inclination to compare my Evo to one of them. I really admire Teslas, but my Evo is nothing like them in design, function, and (most importantly) price -I could build 6 of my Evos for the price of a Model S.


Here are a few videos of my single gear experiment.

1. 0-Vmax run with 3.9:1 gear and heavy prismatic battery. Not geared for top speed or best acceleration, but a happy medium.
http://www.dailymotion.com/video/x2o87bl

2. Some features of the build with its large 7.7kWh LiFePO4 pack.
http://www.dailymotion.com/video/x2nmaa4

3. Cold weather testing an early iteration, light weight and low power.
http://www.dailymotion.com/video/x2i2ycu



Here are a few pictures

electron bom

iTrader: (17)

Good point. Even Tesla's pseudo-two gear drive system increases usable performance over a true single gear system.