# Building my own Racing EV car



## Kevin Sharpe (Jul 4, 2011)

Thorb4ndit said:


> I want the car to at least 0-60 MpH in less than 3 seconds.


Welcome to the forum 

Can you tell us what sort of racing you will be undertaking and your budget for parts? Please also add your location to your profile (it helps us give relevant advice)


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## Thorb4ndit (Jun 5, 2018)

Kevin Sharpe said:


> Welcome to the forum
> 
> Can you tell us what sort of racing you will be undertaking and your budget for parts? Please also add your location to your profile (it helps us give relevant advice)


I'm located in MA right now. I plan to use the car for circuit racing and drag racing. I hope to keep the budget under 15k, but if it is necessary I will go over


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## Duncan (Dec 8, 2008)

Hi
You need to find out the regs for your type of racing and also things like expected speeds, distances and so on

As far as increasing the power out of electric motors is concerned - yes - the key component is the controller

I am using a "10 Kw" forklift motor in my car - which is 208 amps and 48 volts
But I'm feeding it 1200 amps and 340 volts

There are a number of different race and road/race cars on this forum but a car designed for short twisty events looks different from something designed for high speed events

And (at the moment) long distance racing is not feasible for an EV


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## Thorb4ndit (Jun 5, 2018)

Duncan said:


> Hi
> You need to find out the regs for your type of racing and also things like expected speeds, distances and so on
> 
> As far as increasing the power out of electric motors is concerned - yes - the key component is the controller
> ...


So a controller is what increased the motors power? If I have a motor that produces 10 HP will a stronger controller allow it to go above that?


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## galderdi (Nov 17, 2015)

Hi Thorb4ndit,

Welcome and I hope you achieve your goals. I hope you are being realistic. $15k is not a big budget. Yes it is possible to build something for that money but it would only be a bit of fun you would not be at the top of the leader board. But if fun is your goal then go for it.

Without a controller between the battery and the motor (assuming DC motor) the motor will draw it's maximum current at the full voltage available from the battery. This would almost certainly blow the motor. Something like the windings would melt, arc, weld etc.

A DC controller "throttles" the power from the battery to the motor based on some input (usually a pedal). Each controller will have an upper limit eg mine is 175v 1000amps. So installing a bigger controller can give more power from the motor. But every motor has limits too. When talking about racing EVs it is tricky because the ratings on motors is always in terms of what they can handle continuously. The upper limit is a fine line. You can keep pushing more through the motor and all will be fine until suddenly you push too much through it and bang. volts and amps are not the only variables that figure in the calculation. Heat and duration are key variables too. Melting, arcing and welding are more likely as the motor heats up and a motor heats up as it performs hard for longer periods.
A motor rated at 144v 600amps can handle that continuously. The same motor might handle 170v and 1000amps for short bursts of 1 minute or so at normal temperatures. The same motor might handle 200v and 1500amps for a few seconds.

I agree with the previous post, you need to list out your specific performance targets as well as the base for your plan.
What maximum speed?
Acceleration? (already answered 0-60 sub 3 seconds)
What style of chassis/vehicle?
What target weight?
What range under heavy acceleration?

Once you decide on these targets we can advise on suitable component options and whether it is likely to fit under your budget.

If you only aim for 60mph then you might be able to achieve something for $15k (dependant on a lot of other factors).
But when you start talking about sprints and drags I doubt you will be satisfied with a top speed of 60mph.
You will need a light weight vehicle regardless. To get awesome acceleration you will need a system that can handle high current (more than 1000amps for your 4 second target) To get higher speeds you will also need high voltage. This combination of constraints usually means a big battery pack (Like in the Teslas). But the side effect of that approach is the increase to the vehicle weight. There may be other approaches like having two packs which switch from Parrallel to series part way through acceleration. But this would be a tircky and potentially dangerous approach which I would not recommend to anyone other than an electrical engineer.


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## Thorb4ndit (Jun 5, 2018)

The car is a replica Porsche 917. It uses an aluminium space frame chassis. The car weighs around 1,800LBS(It's a race car). I don't care much for the range as long as it is not too low. I want this EV to be AWD, and I want to use three motors to achieve this; Two in the back and One in the front. I want a maximum speed of something over 100.


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## Thorb4ndit (Jun 5, 2018)

galderdi said:


> Hi Thorb4ndit,
> 
> Welcome and I hope you achieve your goals. I hope you are being realistic. $15k is not a big budget. Yes it is possible to build something for that money but it would only be a bit of fun you would not be at the top of the leader board. But if fun is your goal then go for it.
> 
> ...


I've seen the zombie 222 and it amazes me. I want to create something that can destroy drag opponents like that beast. I'm willing to discard the 15k budget to achieve this.


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## brian_ (Feb 7, 2017)

Thorb4ndit said:


> The car is a replica Porsche 917. It uses an aluminium space frame chassis. The car weighs around 1,800LBS(It's a race car). I don't care much for the range as long as it is not too low. I want this EV to be AWD, and I want to use three motors to achieve this; Two in the back and One in the front.


It's interesting that a replica actually has a space frame of aluminum tubing like the original. Are you prepared to cut and weld tubing for the inevitable modifications?

It will likely be considerably heavier after conversion.

That will be interesting, but there will be very little of the original chassis left by the time you accomodate driving the front wheels and don't use the original style of transaxle. According to a poster and drawings on a page that I found about the 917, the driver's feet are ahead of the front axle line - that makes fitting a front drivetrain at least very challenging.


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## Karter2 (Nov 17, 2011)

Thorb4ndit said:


> The car is a replica Porsche 917. It uses an aluminium space frame chassis. The car weighs around 1,800LBS(It's a race car). I don't care much for the range as long as it is not too low. I want this EV to be AWD, and I want to use three motors to achieve this; Two in the back and One in the front. I want a maximum speed of something over 100.


 You seem to have some mixed and conflicting objectives..
Drag racing (competitive) requires a very different vehicle to circuit racing.
And a 917 was never intended as a drag car, so that in itself will introduce some disadvantages on the strip.
Why do you "want to use" 3 motors ?...that is not a objective you should start with.
....certainly for drag racing the front motor is an unnecessary addition of weight , cost, and complication, which will likely reduce the performance rather than improve it.
Even just 2 motors in the rear is an unnecessary complication for a good performance EV.
You should rethink what you really want to build .


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## brian_ (Feb 7, 2017)

To be fair, an issue in drag racing something with the configuration of a 917 is that it will leave substantial load on the front axle, limiting traction in a rear-drive-only configuration... so AWD is a fix for the unsuitability of the design as a traditional drag car.

But I agree, setting objectives then choosing a design to meet them beats choosing design then trying to make it work.


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## Kevin Sharpe (Jul 4, 2011)

Have a read through this thread and view the videos. How does the performance of this car compare with your expectations?

Tesla Powered Cobra Race Car

You say your budget can be disregarded... how much do you *really* want to spend on parts?


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## Duncan (Dec 8, 2008)

Or at the other end of the cost range

http://www.diyelectriccar.com/forum...dubious-device-44370p15.html?highlight=duncan

800 kg - about 500 hp and about $8,000


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## piotrsko (Dec 9, 2007)

Don't forget the Lithumaniacs fiasco/saga


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## Thorb4ndit (Jun 5, 2018)

Sorry if I keep confusing everyone. I'm working with two other people and they are very stubborn and cant make up their minds. 

I'm just going to post what I want to do from now on since i'm taking charge of this project because the other two cant stop bickering. I want to use a 50-60KWH Battery, so that is where the motors will be drawing power from. I want this car to have a quick acceleration and reach high speeds. I wanted to make it AWD because AWD cars accelerate quicker than 2WD. I do not mind modifying the chassis, and the whole car to reach my goals.


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## brian_ (Feb 7, 2017)

Thorb4ndit said:


> I wanted to make it AWD because AWD cars accelerate quicker than 2WD.


That's true if the 2WD car is traction-limited. It will take a lot of power for something with the configuration of a 917 to limited by rear traction, since it will be rear-heavy. If you actually hit the sub-3-second 0-60 target then yes, you will likely be traction-limited.


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## Kevin Sharpe (Jul 4, 2011)

Thorb4ndit said:


> I want this car to have a quick acceleration and reach high speeds. I wanted to make it AWD because AWD cars accelerate quicker than 2WD.


Can you take a look at the following table and tell us which version of the Model S meets your goals (if any)?

Tesla Model S Specification


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## Thorb4ndit (Jun 5, 2018)

Kevin Sharpe said:


> Can you take a look at the following table and tell us which version of the Model S meets your goals (if any)?
> 
> Tesla Model S Specification


What table and are you talking about the tesla model s?


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## Kevin Sharpe (Jul 4, 2011)

Thorb4ndit said:


> What table and are you talking about the tesla model s?


The text "Tesla Model S Specification" is a hyperlink which will take you to a wikipedia article on the Tesla Model S features (past and present).

The Tesla Model S provides a useful benchmark of what's possible today and the resulting weight and size of a car you might build. It also helps move away from phrases like "quick acceleration" and "high speed" which mean different things to different people. For example, 150 mph may not be a very "high speed" to you but it's near the limits of what most conversions can do today.


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## Thorb4ndit (Jun 5, 2018)

AWD Tesla 60D


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## brian_ (Feb 7, 2017)

Kevin Sharpe said:


> Can you take a look at the following table and tell us which version of the Model S meets your goals (if any)?
> 
> Tesla Model S Specification





Thorb4ndit said:


> AWD Tesla 60D


Hmmm... the 60D shows a 0-60 time of 5.2 seconds in that table, which is nowhere nowhere near sub-3-seconds. That model roughly matches your expected battery capacity and is AWD, but it doesn't match your performance goal. If you choose one that matches your expected performance (which I think is what Kevin was suggesting), it could be a starting point for a discussion of power and battery capacity needed.

On the other hand, if you have the same battery capacity and power as the Model S 60D, we could discuss what fitting comparable hardware in the 917 replica might be like, and what the resulting performance might be.


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## galderdi (Nov 17, 2015)

Not trying to turn you off the idea but I think you need to e more realistic. You are asking for too much.

You want awesome acceleration, handling, range, speed and price. Something has to give.

I do time trial motorsport (like autocross). For this reason I went with acceleration, handling and price but had to sacrifice speed and range. I sacrificed those because top speed is not important in my sport and I don't travel all that far. But this makes it unsuitable for drag racing or sprints.

Your battery capacity alone is likely to cost your total budget unless you stumble on to a 1 in a thousand deal.

I hope you can prove me wrong.


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## Kevin Sharpe (Jul 4, 2011)

brian_ said:


> Hmmm... the 60D shows a 0-60 time of 5.2 seconds in that table, which is nowhere nowhere near sub-3-seconds.





galderdi said:


> Not trying to turn you off the idea but I think you need to e more realistic. You are asking for too much.


Yeh, I'm trying to help the OP understand the tradeoffs that are required. *IF* the OP can live with ~5 second 0-60 time then we probably already have a couple of 'affordable' cars working and a good model to follow 

Very similar questions here


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## Karter2 (Nov 17, 2011)

One question..
Will this 917 EV be fully road legal also, or just a "track car" ?


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## John Metric (Feb 26, 2009)

Thorb4ndit said:


> The car is a replica Porsche 917. It uses an aluminium space frame chassis. The car weighs around 1,800LBS(It's a race car). I don't care much for the range as long as it is not too low. I want this EV to be AWD, and I want to use three motors to achieve this; Two in the back and One in the front. I want a maximum speed of something over 100.


Replica 917? Like this? for $15k


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## John Metric (Feb 26, 2009)

I am working on a close relative to a 917 right now. Group C chassis.
Specs would destroy Zombie 222. 
RWD only though. The original 917 was RWD, were those accelerations not fast enough for you?
Do you own the chassis already? That's probably the hard part.


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## Duncan (Dec 8, 2008)

Hi 
At the last 1/8th mile drags I did 8.6 seconds and 85 mph - I think that is about 5 seconds to 60 mph

It should have been better but I had too much wheelspin and the motor died before the end!

That's with my cheepo DC system


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## JasonPaulBennett (Aug 27, 2015)

I had similar goals, 
buy my stuff.

I wanted to bridge two 350 amp inverter drivers,
To feed each liquid cooled motor.
Easy 1000 lb/ft torque for a few moments.
I was thinking direct drive and dual rear axles.
This would be a very high voltage system.
Lots of small batteries and probably a super capacitor.
CAN bus programing and explosive electrical disconnects.
Could be a lot of fun.

http://www.diyelectriccar.com/forums/showthread.php/ultimate-ev-drive-system-2-siemens-196810.html


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## DavidDymaxion (Dec 1, 2008)

I'd love to have a project like yours to drive! Looks like it will be fun!

The Dodge Demon is a 2WD car and does 0 to 60 mph in 2.3 seconds, and is very fast in the 1/4 mile, too. Given it'll do wheelies and has a suspension optimized for acceleration, I imagine it does not corner great!

The La Ferrari is 2.4 seconds and is also RWD; the MacLaren 720S is 2.7 seconds and RWD. These cars do corner well.

You don't need AWD to accelerate well, but it takes great design, great tires, and near perfect conditions, and potentially a great driver if you don't have driver aids like awesome traction control. I'd lean towards doing a RWD car. Splicing FWD into that car would be a huge and costly challenge, and if not done well could actually slow the car down.

I don't think this has been mentioned yet: A transmission is your friend. You can get as much torque to the rear wheels as a Tesla, with 1/2 the electrical system, and 1/2 the speed (in that gear). It's a pretty worthy tradeoff to accelerate like a Tesla up to 77.5 mph (half of the Tesla's top speed) by leaving it in 3rd gear, but then have higher gears for more top speed. It might even be acceptable to accelerate like a Tesla up to 39 mph (1st gear) using 1/4 the electrical system.


Thorb4ndit said:


> ... I want this car to have a quick acceleration and reach high speeds. I wanted to make it AWD because AWD cars accelerate quicker than 2WD. I do not mind modifying the chassis, and the whole car to reach my goals.


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## Duncan (Dec 8, 2008)

DavidDymaxion said:


> I don't think this has been mentioned yet: A transmission is your friend.


Disagree - a transmission is a heavy object that gets in the way and gives little of no advantage


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## John Metric (Feb 26, 2009)

https://www.racingjunk.com/24-Hours...ale/183055287/Gulf-Porsche-917-Kit-Laser.html


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