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he hasn’t stated numbers, and that set up could yield 350hp +
He has given performance targets, and 350 hp would be far short of adequate:
My goals going in were:​
180 mph top speed​
2.5 second zero to 60​
...​

And there is a version with a awd transfer case.
True... if there were only space under a Corvette floor for a transfer case and a shaft to the front, where a drive axle would take almost as much space as just running a separate front drive unit.
 

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Discussion Starter · #22 ·
I'm pretty sure that I'll still be able to put plenty of batteries in the engine bay: the '82 Corvette is almost 1/2 hood. Tesla battery modules are 27 by 11.5 by 3.5 inches, and looking at build space I'd say I have about 60 by 30 by 20 inches of hood space between the front wheels and the driver space. Using an ideal packing, I can fit about 20 battery modules in there, although I'd only use 16 at most in that space. That solves my battery storage problem.

One question I have is regarding the gearing on the Tesla motors: if the back motor tops out at 16,000 rpm and has a gear reduction of 9.73:1, then that connected to 20 inch wheels would top out at about 98 miles per hour. Given that this is the Tesla Ludicrous speed drivetrain which apparently tops out at at least 155 mph, there has to be something I'm missing. Maybe StealthEV posted the wrong reduction ratio?
 

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I have a lot of experience with the C3. I converted a C3. For enough money, any thing is possible.
Realistic number: $60K without batteries.
 

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I'm pretty sure that I'll still be able to put plenty of batteries in the engine bay: the '82 Corvette is almost 1/2 hood. Tesla battery modules are 27 by 11.5 by 3.5 inches, and looking at build space I'd say I have about 60 by 30 by 20 inches of hood space between the front wheels and the driver space. Using an ideal packing, I can fit about 20 battery modules in there, although I'd only use 16 at most in that space. That solves my battery storage problem.

One question I have is regarding the gearing on the Tesla motors: if the back motor tops out at 16,000 rpm and has a gear reduction of 9.73:1, then that connected to 20 inch wheels would top out at about 98 miles per hour. Given that this is the Tesla Ludicrous speed drivetrain which apparently tops out at at least 155 mph, there has to be something I'm missing. Maybe StealthEV posted the wrong reduction ratio?
That sounds like a plan. Keep in mind that all that battery will be pretty heavy and will certainly affect performance.

16,000 / 9.73 = 1644 wheel RPM.
20" wheel diameter = 1061 rev/mile. Yup, that creates ~95mph.
Now consider the Model S. 245/45R19 tires are 751 rev/mile. Bam, 131mph. (top speed of LR model S? 135.)
HSRMotors specs 18,000 rpm max for their 'sport plus' unit. That reaches 147mph. (top speed of performance model S? 155.)

The reduction ratio is known to be correct.

If you use smaller tires, the 4.5:1 gearset will actually work better, since it'll push you to ~200mph with 20" wheels. (that is total diameter incl. tires.)
 

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Discussion Starter · #25 ·
Okay, that makes sense. Do you know where I could get that gearset?

Edit: Nevermind, I found it with one search.
 

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One question I have is regarding the gearing on the Tesla motors: if the back motor tops out at 16,000 rpm and has a gear reduction of 9.73:1, then that connected to 20 inch wheels would top out at about 98 miles per hour. Given that this is the Tesla Ludicrous speed drivetrain which apparently tops out at at least 155 mph, there has to be something I'm missing. Maybe StealthEV posted the wrong reduction ratio?
No, the problem is the 20 inch dimension. We're not talking about golf carts or microcars here.

16,000 / 9.73 = 1644 wheel RPM.
20" wheel diameter = 1061 rev/mile. Yup, that creates ~95mph.
Without checking the math, that looks right. :)

Now consider the Model S. 245/45R19 tires are 751 rev/mile. Bam, 131mph. (top speed of LR model S? 135.)
HSRMotors specs 18,000 rpm max for their 'sport plus' unit. That reaches 147mph. (top speed of performance model S? 155.)
The issue with the original value does appear to be that the calculation must use the overall diameter (and thus the outside circumference) of the tire, not just the bare wheel. The easy (and most accurate) method is to get that revolutions per mile (or kilometre) value from tire specification charts, as shown here. The overall diameter of a 245/45R19 is nominally 703 mm or 27.7", and a random brand (Michelin) and model shows 28" overall and 743 rev/mile... exact dimensions vary.

The reduction ratio is known to be correct.
Yes, it's published by many sources. When a calculation comes up way off of published values, it's time to check the calculation.

If you use smaller tires, the 4.5:1 gearset will actually work better, since it'll push you to ~200mph with 20" wheels. (that is total diameter incl. tires.)
True, but no one is going to use 20" tall tires. A stock 1982 Corvette had 225/70R15 or 255/60R15 tires, which are about 27" tall... almost as tall as the base Tesla Model S tires.

The 4.5:1 gearset is for people who want to feed the Tesla drive unit outputs into front and rear final drive units (differentials) with their own substantial gear reduction; it is not useful for driving wheels directly in street-driven vehicles.
 

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I'm pretty sure that I'll still be able to put plenty of batteries in the engine bay: the '82 Corvette is almost 1/2 hood. Tesla battery modules are 27 by 11.5 by 3.5 inches, and looking at build space I'd say I have about 60 by 30 by 20 inches of hood space between the front wheels and the driver space. Using an ideal packing, I can fit about 20 battery modules in there, although I'd only use 16 at most in that space. That solves my battery storage problem.
Here's a suggestion: make a cardboard box 60" by 30" by 20", take it to the car, open the hood, and figure out how that entire box is going in there. When reality sinks in, start again...

Realistically, you have just the space currently occupied by the engine (with accessories), which is roughly half of that five feet, and narrower that you might guess looking at the outside of the car. The modules need to go in a supporting structure, and surrounded by a box. The suspension, steering, and brake master cylinder still need to be there (as well as a whole front drive unit if you're still thinking AWD). Although the stock radiator is larger than required, the drive unit and battery will still need a cooling system with radiator. About half of those 20 Model S/X modules will actually fit.

If you do extend modules way up into the nose, there's no need for a drive unit, as the result will handle so badly that there is no point in driving it.
 

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Discussion Starter · #31 ·
Okay, let's go through this:

1. I made a pretty big mistake in my calculations: I mixed up wheels and tires. You're absolutely right, I should have been doing it with about 27.7 inch tires.
2. I see your point, and I'm going to shrink my goals. I'll try for a top speed of 150 mph, but I can't really go lower without compromising my goals: the stock 82 has a top speed of 130, and I want to outperform that.
3. I'm going to have another look at the AMR motors, because I was comparing constant supply for those to peak supply for the Tesla drive unit. It will be expensive, but I'll see if I can meet my new goals with just 2 of the motors in the rear, keeping the corvette RWD.
 

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Discussion Starter · #32 ·
So I'm back from doing some number crunching, and the results are okay. I can use 2 motors in the back, and I can get 3.5 second zero to 60 with a 130 mph top speed. I can also get 4.2 second zero to 60 with a 150 mph top speed. (Additionally, this is with significant aerodynamic improvements.) It would be easier and cheaper to do this than to have 4 motor AWD in a car built for RWD, and it would free up more space in the front for batteries as well. My main problem, though, is that this feel's like it's not enough. My whole goal with this is to make an electric car conversion that blows most cars under a million dollars out of the water, for considerably less. That's another thing too, the performance on paper scales with cost, but I can't really justify spending probably $80,000 on a car with specs that are, while not lackluster, considerably worse than if I went a little further.

If I use 3 motors, the specs get much better.
This gives me a 0-60 of 3 seconds with a top speed of 160 mph, but it would necessitate me replacing the front axle assembly, and making some significant frame modifications.
I could also configure it for 0-60 in 3.5 seconds, which would have the benefit of letting me reach 300 km/h: in just 11.9 seconds. That is what we call blowing multimillion dollar cars out of the water for a fraction of the price. Tell me which one you think I should explore more.

I would also need to find a front AWD axle assembly that I can swap into the frame, so tell me if there are any options that spring to mind for that. It might actually be cheaper to just look at different classic cars that are already AWD, because although I personally think that the C3 corvettes are some of the most beautiful cars ever made, I'm open to other cars if they'd be easier.
 

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Discussion Starter · #35 ·
Yeah, I'm actually thinking about changing the donor car over to a Factory 5 GTM. I don't have the corvette yet, and if I switch over to the GTM I'll have a much better and safer car, with more downforce. I'll probably configure it for 300 km/h top speed, because that will give me 2.8 second 0-100 km/h times, and 9.9 second 0-300.

What do you think?
 

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I like your plan. Not that an '82 Vette is a bad car, they actually have ton of strengths like you've mentioned, and 82's are one of the coolest looking out there IMO. The issue is that making a 40 year old Corvette go 180MPH is probably just as much of a task as making a DIY EV whereas the Factory 5 just needs a powerplant. Not to mention the safety of a caged, modern car vs. a fiberglass one.
 

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Yeah, I'm actually thinking about changing the donor car over to a Factory 5 GTM. I don't have the corvette yet, and if I switch over to the GTM I'll have a much better and safer car, with more downforce. I'll probably configure it for 300 km/h top speed, because that will give me 2.8 second 0-100 km/h times, and 9.9 second 0-300.

What do you think?
If you have the budget and the time, building a GTM as an electric would certainly produce a better car (aside from aesthetics, which is just personal opinion).

This would presumably be RWD only. People have discussed building an AWD GTM, but it makes no sense because it is not designed for that and uses Corvette (C5) front suspension components... although this sort of thing has been done with other RWD cars.

It looks like there has been at least one electric GTM built, and a few discussed, but I don't know how many have been completed or if there are any with components that make sense now. The obvious components would be a Tesla Model S large drive unit and a battery pack split between the engine and fuel tank spaces.

Of course any similar kit (tubular steel frame, body in the general style of a race car such as the Ford GT40) is a potential candidate. With any of these kits you will hit the problem that frame tubes are located where they are in the way of fitting in the bulky and inflexible battery modules, because the frame is designed to work with an engine and a fuel tank that can be shaped to fit the available space. The GTM uses stock Corvette C5 "saddle" tanks, which makes sense for gasoline but are two small and awkward volumes to try to pack any battery module into.
 

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Awesome project if this becomes anything close to your goals.

I see the remarks about the Lexus transmissions as a much cheaper option, but will not reach your goals. But I agree with spending much more, it has to be justifyable.

One thing though about Lexus transmissions. They are one of few gearboxes out there that come with a (planetary) 2 speed gearbox from factory.
I don't mean the motor itself, which is equal to a Prius, I mean the two speed behind it.
And don't forget you could still bolt another big electric motor to the whole Lexus transmission case. Giving you 3 motors and a 2 speed gearbox. Lexus GS450h goes to 270km/h from factory and you could run a different final gear in the back. Lexus LS600h gives you AWD.
Anyway, I get it that you might choose a different route to compete with million dollar cars.
However, just wanted to say it is not a bad option, bringing the cost down and still giving you nice performance.
 

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An 89 Corvette with a blown engine costs almost nothing, so could a super low budget, low range accepted, low top speed, no regenerative brake car-build use a Corvette body and participate in autocross?
It seems one motor in the transmission tunnel and a minimal set of batteries for ~6 minutes total race time would weigh less than stock, which would increase performance around the twisties.
How much weight in batteries would be needed for racing, and how much in a removable pack to get ~50 miles range?
Would using a Corvette body be any more expensive than using a Honda Civic?

What's the cheapest it could be built, still doing 0-60 in under 6 seconds or better, and what equipment would you use?
 
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