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maschinenbau
maschinenbau Dork
5/31/19 8:48 a.m.

Every Friday night in summer, Atlanta Motor Speedway hosts some 1/8th mile drag racing, heads-up, no-time. It's very casual and open to pretty much anything. They divide you into some ambiguous classes, line you up on Turn 4, and let em rip. It's a lot of fun, close to home for me, and cheap. I brought my El Camino out last time and had a blast.

I also have this like-minded co-worker who built an Exocet with a Tesla powertrain, the "Electrocet". You may remember it from last year's Ultimate Track Car Challenge. It's an extremely amazing machine, right up until roughly 100 MPH when it runs out of motor speed. He also has a set of big ol' Mickey Thompson drag radials he wants to test out. It is not exactly street legal however.

Image result for electrocet

And of course I have my $2000 Challenge car, Datsaniti. Now equipped with some meaty drag radials, I've been itching to get it to a drag strip. 

The plan is to tow the Electrocet with my El Camino using my tow dolly, and co-worker follows me in Datsaniti. Coworker has even programed in a "towing mode" for the Electrocet, which uses the regen function of the electric motor to trickle-charge the battery, robbing about 5 hp from my truck. The level of sketchiness we are about to put on the road is very high, but it's a short 20 mile drive. 

Last night I went to pick up his car to leave at my house, where we would meet after work today and go straight to the event. That's where things have already gone wrong. 

Dolly wheel bearing is trashed. Luckily we noticed it in co-worker's neighborhood while testing out the "towing mode", which was having computer bug issues of its own. So we ran to the store before the closed, picked up a new bearing and I changed it out in his neighborhood street, while he de-bugged the Electrocet's brain and uploaded some fresh code. A couple hours later, we both succeeded and I was on the road.

It towered great and the trip was uneventful, except for a high-speed police chase that roared past me on I-20. That was pretty wild!

That brings us to roughly midnight last night. I'll start updating after work when we head for the track. So many unknowns in this equation.

John Welsh
John Welsh Mod Squad
5/31/19 8:59 a.m.

Teslas are quick with a body.  Just how fast in an 1/8th mile (or 0-60) is a Tesla with no body?  

Robbie
Robbie UltimaDork
5/31/19 9:06 a.m.

That electrocet man sounds awesome.

Is it 2wd or awd?

MadScientistMatt
MadScientistMatt PowerDork
5/31/19 9:11 a.m.

I went to the AMS Friday Night Drags a while ago with my brother-in-law. It's pretty interesting - it's an absolutely minimal operation, with no timing equipment that I could remember, but it attracts a lot of wild cars.

Dusterbd13-michael
Dusterbd13-michael MegaDork
5/31/19 9:13 a.m.

Subscribed for multifaceted awesomeness 

Professor_Brap
Professor_Brap Dork
5/31/19 9:14 a.m.

Im way to into this. 

 

AngryCorvair
AngryCorvair MegaDork
5/31/19 9:16 a.m.

it looks like rear-motor / RWD to me.  IIRC the AWDs have a motor at each end rather than a T-case and driveshafts -- because that stuff would cut into battery packaging space.

AngryCorvair
AngryCorvair MegaDork
5/31/19 9:17 a.m.

also sub'd because there are so many ways this can go.   plus el Camino.  i'm always down for some el Camino.

Robbie
Robbie UltimaDork
5/31/19 9:20 a.m.
AngryCorvair said:

it looks like rear-motor / RWD to me.  IIRC the AWDs have a motor at each end rather than a T-case and driveshafts -- because that stuff would cut into battery packaging space.

Yes, but who says you can't do a twin motor electrocet?

maschinenbau
maschinenbau Dork
5/31/19 9:26 a.m.

Yep it's rear-motor RWD, but most of the weight is in the battery pack, which is basically the floor.

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
5/31/19 10:08 a.m.

in for updates too

bluej
bluej UberDork
5/31/19 10:45 a.m.

THIS is how  you start the weekend off right!

1SlowVW
1SlowVW Reader
5/31/19 11:40 a.m.

This is so fantastic. All of it. Every single ounce.

AngryCorvair
AngryCorvair MegaDork
5/31/19 2:29 p.m.

as i stated in Monzora build thread, being smart is awesome.  so lets do some math, shall we?

ASSUMPTIONS:

  • ~65% weight on rear
  • tires are capable of 1.1 peak mu
  • negligible weight transfer in acceleration (because CG is so low)
  • power/weight will sustain peak mu accel EITHER through the 1/8-mi (660 ft) OR until Vmax is reached

THEN:

  • 0.65 (rear weight %) * 1.1 (peak mu) = 0.715 g acceleration

  • v^2 = 2 * a * s
  • s = 1/8-mile = 660 ft
  • 1 g = 32.2 ft / sec / sec
  • then a = 0.715 * 32.2 = 23.02 ft / sec / sec
  • and v = sqrt ( 2 * 23.02 * 660 ) =  174 ft / sec = 118.6 mph *THEORETICAL Vmax*

BUT we know ACTUAL Vmax = 100 mph = 146.67 ft / sec

SO, assuming no acceleration losses, this car should pull 0.715 g accel unti it hits 100 mph ( = 146.67 ft/sec), then it will hold that speed until it hits the finish line which is 660 ft from the start.

How long does it take to get to 100 mph ( 146.67 ft / sec )?

  • Vf = Vi + ( a * t)
  • Vf = 146.67 ft / sec
  • Vi = 0
  • a = 23.02 ft / sec

then t = 6.37 sec

and how much distance does it take to get to that speed?

  • s = 1/2 * a * t^2
  • s = 467 ft
  • so in 6.37 seconds he will hit his Vmax of 100 mph in a distance of 467 ft from the start.   

but he's not at the finish line yet, he's still got 193 ft to go ( = 660 - 467 ).

and at 146.67 ft / sec, it takes another 1.314 sec to cover those 193 ft.

so his theoretical standing start 1/8-mile performance is (6.37 + 1.314 = ) 7.684 sec at Vmax = 100 mph

maschinenbau
maschinenbau Dork
5/31/19 6:47 p.m.

ATL traffic in this heat, in cars without ac, 3 wide in the Camino's bench seat was a fun sweaty experience but we made it. 2 other guys in the Datsun had a similarly sweaty time. So worth it.

Datsaniti's throttle pedal position code is back, which means the potentiometer inside the pedal is dirty again. That means the engine idles until restarting...killing the run. Oh well. Unsurprising after all that bodywork. Electrocet is simplyfast. It just rips. Put a huge gap on a heavily turbod Civic on slicks. This is amazing.

 

maschinenbau
maschinenbau Dork
5/31/19 7:04 p.m.

Base camp

Dead_Sled
Dead_Sled Reader
5/31/19 7:50 p.m.

Thanks for bringing us along.  SWMBO was loving datsanity (first she's seen it with paint) until I scrolled up and showed her the elco.  "That's the perfect color on that car".  yes

maschinenbau
maschinenbau Dork
5/31/19 9:08 p.m.

Looks like the Electrocet and I are both classed in "Tuner" which is basically non-V8 cars with drag radials, so we're trying to get matched up. We've got beers on the line!

Dusterbd13-michael
Dusterbd13-michael MegaDork
5/31/19 9:09 p.m.

Does the return road include a section of high speed high banked oval?

maschinenbau
maschinenbau Dork
5/31/19 9:43 p.m.

In reply to Dusterbd13-michael :

Yes and I 3-wheeled lol

Mndsm
Mndsm MegaDork
5/31/19 9:50 p.m.

Holy E36 M3 man, the wagon is looking awesome. 

maschinenbau
maschinenbau Dork
5/31/19 10:32 p.m.

Electrocet gapped Datsaniti. We both had our best runs that time with no issues! Electrocet is in the finals.

maschinenbau
maschinenbau Dork
6/1/19 1:24 a.m.

Final round of "Tuner" class was against a 500hp turbo RX7. It was really close but the Electrocet took second. Overall a really fun night and we're excited to do it again. Both cars got a ton of attention and it's very satisfying to finally have something to show off after working on project after project for years. I needed this.

Here's the final round:

https://youtu.be/nDuYBdgjUk8

 

maschinenbau
maschinenbau Dork
6/1/19 9:30 a.m.

That red machine behind the Electrocet is a 3800-swapped and nitrous'ed Geo Tracker with 28" rear tires. It placed 3rd. This event is crazy.

maschinenbau
maschinenbau Dork
6/1/19 1:32 p.m.

Here is footage from the "gap cam" in the race between Electrocet and Datsaniti

https://youtu.be/qlx42KSLFSI

 

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