Going Electric with my 996!
09-29-2014, 02:39 AM
#241
Banned
Thread Starter
I certainly wouldn't mind dropping 200 lbs! Any idea who might make custom transmission? I guess it couldn't hurt to look into and start figuring what it would take to accomplish.
In other news, when preparing to put the new clutch and flywheel in, it was apparent that the pressure plate had warped as well... ugh, now waiting on a new one... hope to have the drivetrain back together this coming weekend.
In other news, when preparing to put the new clutch and flywheel in, it was apparent that the pressure plate had warped as well... ugh, now waiting on a new one... hope to have the drivetrain back together this coming weekend.
10-14-2014, 02:46 PM
#242
Banned
Thread Starter
Sorry for the belated update (I know everyone is waiting on the edge of their seats)... but the car is getting VERY close to being done. There are many small electrical / cosmetic items to be completed, and they will all take some time, but we're to the point that it is ready to really drive and do more in-depth testing!
With the new ultra-lightweight flywheel, the car is more predictable and dare I say, easier to drive. The electric motor doesn't have friction to slow it down like a conventional internal combustion engine (ICE), and the heavier flywheel stored so much rotational energy you would hear the motor spinning at high RPM even though you put in the clutch, and it took a while for it to slow down. Not only does the new flywheel reduce rotational mass and make for a more entertaining launch, it also allows to motor to drop more quickly/traditionally in RPM similar to an ICE. What can I say, other than it just feels right! To anyone considering an EV conversion, this is a change I HIGHLY recommend. All upside, and the car feels more "stock" or as it should be.
As the car is basically done, it was time to check on the weight... Kirk drove out to a truck scale and saw some pretty eye-popping numbers shout out at him... with both axles on the scale it showed 3650! That's about 100 -150 lbs more than we hoped.
Trying a rudimentary front/rear weight distribution, he found this:
2250 = rear axle only
1450 = front axle only
-----------------
3700 = total of above
So, the scale isn't exactly accurate and it measures in 50 lb increments... I wouldn't mind trying to get better measurements. Unfortunately, I didn't weigh the car prior to the conversion, and it seems a little difficult to get an accurate weight. The closest one I can find is from a C&D review stating their car weighed 3239 lbs. Add in a full tank of gas (103 lbs) and we get 3,342 total. We've added about 300 lbs! Now, did the test car have 18" wheels? It certainly didn't have the weight of the stereo I added...
Showing a 61% rear weight bias is also not as significant a change as I'd have guessed, only a 1% or so off the supposed 62% stock, however I could venture to guess that the added cabriolet top increases rear weight and base numbers wouldn't account for this.
If anyone can find more definitive weight numbers for a 1999 Cab C2, as well as front/rear weight distribution, feel free to share.
Maybe I really need to find a way to get a single-speed transmission!
The plan is to get the car an alignment then go on a long-range test drive this weekend. I'll update, hopefully with video! Here's hoping for 100+ miles! If it all works out, I'll also be visiting a dyno soon!
With the new ultra-lightweight flywheel, the car is more predictable and dare I say, easier to drive. The electric motor doesn't have friction to slow it down like a conventional internal combustion engine (ICE), and the heavier flywheel stored so much rotational energy you would hear the motor spinning at high RPM even though you put in the clutch, and it took a while for it to slow down. Not only does the new flywheel reduce rotational mass and make for a more entertaining launch, it also allows to motor to drop more quickly/traditionally in RPM similar to an ICE. What can I say, other than it just feels right! To anyone considering an EV conversion, this is a change I HIGHLY recommend. All upside, and the car feels more "stock" or as it should be.
As the car is basically done, it was time to check on the weight... Kirk drove out to a truck scale and saw some pretty eye-popping numbers shout out at him... with both axles on the scale it showed 3650! That's about 100 -150 lbs more than we hoped.
Trying a rudimentary front/rear weight distribution, he found this:
2250 = rear axle only
1450 = front axle only
-----------------
3700 = total of above
So, the scale isn't exactly accurate and it measures in 50 lb increments... I wouldn't mind trying to get better measurements. Unfortunately, I didn't weigh the car prior to the conversion, and it seems a little difficult to get an accurate weight. The closest one I can find is from a C&D review stating their car weighed 3239 lbs. Add in a full tank of gas (103 lbs) and we get 3,342 total. We've added about 300 lbs! Now, did the test car have 18" wheels? It certainly didn't have the weight of the stereo I added...
Showing a 61% rear weight bias is also not as significant a change as I'd have guessed, only a 1% or so off the supposed 62% stock, however I could venture to guess that the added cabriolet top increases rear weight and base numbers wouldn't account for this.
If anyone can find more definitive weight numbers for a 1999 Cab C2, as well as front/rear weight distribution, feel free to share.
Maybe I really need to find a way to get a single-speed transmission!
The plan is to get the car an alignment then go on a long-range test drive this weekend. I'll update, hopefully with video! Here's hoping for 100+ miles! If it all works out, I'll also be visiting a dyno soon!
10-15-2014, 07:08 PM
#244
Banned
Thread Starter
3957=GVWR -which I believe is max legal carrying capacity.
1709/2524= GAWR FRONT/REAR -Gross Axle Weight Rating. Again, max legal carrying capacity.
Interesting that 2524+1709=4233 (not the GVWR). I think the GAWR is to prevent road damage. Where the 3957 has more to do with suspension & braking safety. No actual weight.
10-15-2014, 09:24 PM
#245
When I read this I had a *DOAH* moment... but then I looked. Here's all I found:
3957=GVWR -which I believe is max legal carrying capacity.
1709/2524= GAWR FRONT/REAR -Gross Axle Weight Rating. Again, max legal carrying capacity.
Interesting that 2524+1709=4233 (not the GVWR). I think the GAWR is to prevent road damage. Where the 3957 has more to do with suspension & braking safety. No actual weight.
3957=GVWR -which I believe is max legal carrying capacity.
1709/2524= GAWR FRONT/REAR -Gross Axle Weight Rating. Again, max legal carrying capacity.
Interesting that 2524+1709=4233 (not the GVWR). I think the GAWR is to prevent road damage. Where the 3957 has more to do with suspension & braking safety. No actual weight.
10-20-2014, 04:11 PM
#246
Banned
Thread Starter
97.5 Miles! - Long Range Test Drive
Sunday was a good day to go for a ride... and Kirk and I set out on a long-range test. We were both pretty excited to see the result.
10-20-2014, 09:20 PM
#250
Race Director
Because I'm lazy and your thread is now enormous, are you switching to lower rolling-resistance tires? I'm sure you don't want to go ultra-hard and narrow since the weight distribution still makes oversteer a potential issue...otoh, there's a lot of potential energy savings in the tires...
10-21-2014, 02:55 AM
#252
Banned
Thread Starter
First, thanks for the comments - it was great to see how far we could go. The one nice thing about trying to build a fun electric car is that you need more batteries so you can feed more power to the motor... which means if you are gentle, you'll also get more range.
That said, this was not an econo build. The long-distance test is really for general benchmarking, and we were pleased with the overall the system efficiency. This is to be a fun electric Porsche - and unless I'm going a long way, I'm sure my lead foot will find a way to deplete the batteries in 50 miles or less! The car is lots of fun, just as it should be, and that is the main priority. The plan is to get my car on a dyno late this week, so we'll see what kinds of numbers we're putting out.
To answer your question, when I purchase tires I will use low rolling-resistance as a serious factor, but the 18" sport technos which are much wider than the turbo twists they replaced will stay on the car. We need some serious rubber to put an estimated 400 fl/lbs of torque on the road!
I plan on sharing some video from the dyno test, then hopefully some more of the car in a more spirited setting, hopefully all which will happen within the next two or three weeks, as the car is almost finished and will soon be coming home from the shop!
That said, this was not an econo build. The long-distance test is really for general benchmarking, and we were pleased with the overall the system efficiency. This is to be a fun electric Porsche - and unless I'm going a long way, I'm sure my lead foot will find a way to deplete the batteries in 50 miles or less! The car is lots of fun, just as it should be, and that is the main priority. The plan is to get my car on a dyno late this week, so we'll see what kinds of numbers we're putting out.
Because I'm lazy and your thread is now enormous, are you switching to lower rolling-resistance tires? I'm sure you don't want to go ultra-hard and narrow since the weight distribution still makes oversteer a potential issue...otoh, there's a lot of potential energy savings in the tires...
I plan on sharing some video from the dyno test, then hopefully some more of the car in a more spirited setting, hopefully all which will happen within the next two or three weeks, as the car is almost finished and will soon be coming home from the shop!
10-21-2014, 11:03 AM
#253
Congrats in your long range test.
I would like to see a road course test driven above 8/10 to see how long your batteries can last and whether any heat related issues occur. 
I would like to see a road course test driven above 8/10 to see how long your batteries can last and whether any heat related issues occur.
10-22-2014, 03:23 PM
#254
Banned
Thread Starter
I can tell you that when we horse around pretty hard for 30 minutes or so, the batteries do get warm, up to about 115 degrees. The motor, with the current fan setup, seems to do fairly well.
The battery packs are not actively cooled, and we have put a little insulation on them where the motor blows hot air onto them. After the long range test, we did some examination of pack temperatures and found that where we were reading a 4 out of five on the gauge cluster (oil pressure sensor, set to measure in C) one sensor may be incorrectly skewing the reading or the programming may be off for that one. We'll examine and fix as necessary. If the packs do get hot, we'll have to add some active airflow over the tops of them. We're hoping this won't be required.
So, autocross capability to be determined... We're trying to schedule a dyno on Friday!
