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Old 07-28-2013, 03:15 PM   #1
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Default Miata Electric KERS

If you already don't know what KERS is you must not watch racing. KERS is Kinetic Energy Recovery System, it takes braking power to recharge the system.

I was going to keep the research on up and keep it only to my closest friends to what I was thinking of. So far so good after 3 months, only a few people know including (Plucas) and the components are almost all figured out. But know I am going to let Miata Turbo know what the full idea is and to see what you have to say. The system that I figured would able to be powered for 20 secs at a time or lap.


The Motor--is what I found is a AC motor from Hi Performance Electric Vehicle Systems. The motor would a chose between the AC-9 to AC-15

Power Output --The lowest power motor, the AC-9 will produce 28 HP and 70 FT-Lbs @ 48V/650 Amps DC. The Curtis Controller is what varies the power output and changes the DC power to AC for the motor.

Location--The motor would replace the location of the factory A/C compressor since the motor is about 6" in dia and overall 10.3" long. A A/C compressor clutch would allow the motor be turned off with out putting a draw on the engine. The A/C compressor clutch would be upgraded to support the torque of the electric motor.

Power Source--I was looking at using batteries, but there were two problems with that. One was the weight of the system and the other would be the recharge time. I found a ultra supercapacitor from Maxwell Technologies that will produce 4800A @ 75 volt for one sec. The Cap is a 95F cap and will last up to 17 years or 11,000 discharge cycles.

The problem I am coming up with is the price of 5-7k USD
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Old 07-28-2013, 03:31 PM   #2
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Intriguing, if you can make it work.
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Old 07-28-2013, 03:37 PM   #3
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It all depends on what you are trying to achieve. If the idea is to do something different and have some fun, then go ahead. it would be an interesting project.

If that is not the case, and you are seeking faster lap times, there are far less complicated and less expensive ways to achieve the same thing. F1 teams do it because the rules allow it (trying to make F1 'green') and it gives them a competitive advantage IF they can do it reliably. A lot of them cannot, even with lots of money and engineering talent. Ask Red Bull how well their KERS system performed this weekend.

So assuming you are going to do it for fun, I have some thoughts:
1. I do not see the need for the clutch on the A/C motor. It will produce some intertial loading on the motor, but otherwise, unless it is connected to an electrical load (recharging the system) it will not create a huge drag on the engine. The intertial load can be offset somewhat by lightening the flywheel.
2. The control system is going to be a big challenge. I am not up on what the Curtis controller can do, but if its hardware and software is set up for high performance regenerative braking, then maybe it will work. Whether or not it is up to the task of working in a race environment (thermally, power capacity) is another question.
3. It will be important to carefully implement the belt drive system (or whatever you are going to use) between the A/C motor and the crank.
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Old 07-28-2013, 04:11 PM   #4
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Charging through engine braking only I assume?
I don't know what torque normal engine braking transmits, this will need to be on top and will most probably close to replace the rear hydraulic brakes (if the cap isn't already loaded).
A tooth belt to the crank would be needed, since the multiribs might only take a few kW (e.g. about 1.5kW to the alt). Addons like for Dry Sump pumps might be enough but 28hp is not a little.

Drive the pinion flange? Many nifty things possible then for stability and traction control. Even better with one engine driving/braking each outgoing shaft on the diff.
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Old 07-28-2013, 04:15 PM   #5
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It will be important to carefully implement the belt drive system (or whatever you are going to use) between the A/C motor and the crank.
Yes it would be going through a belt, instead of doing a direct drive like Formula 1 does. I know that 03-04 Cobra uses 64hp (47.7 kW)to power the supercharger. A direct drive would also use to much room in front of the engine.

I would love to do a full electric Time Attack car but I don't have the money, nor the charge up time.
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Old 07-28-2013, 05:12 PM   #6
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ZX-Tex-- as you were saying...Would it be easier to make power other ways, then the answer is yes. I want to try something different and maybe one day it could cost $1,500-$2,500 for the system.

I will be starting on doing my engine sway soon and the most made naturally aspirated is around 330-375 hp. I do not want to go with a turbo or supercharger.

One day I will go to a full electric car like this motor with the diff included Getrag electric transaxles

A petrol powered engine is max of 25% efficient and a electric motor is 83-92%. So it could be better if the charging time could be more efficient.
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Old 07-29-2013, 10:45 AM   #7
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I'd run it off the diff flange with a chain drive. Look at that 600hp 1700lb miata on miata.net for his alternator solution.
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Old 07-29-2013, 01:43 PM   #8
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The problem with running it off of the drivetrain is that the motor is limited to 7500-8000 rpm.

The reason I was looking this as extra power, is not for the HP but for the Torque. It would be nice for the 120+Mph straights, the drag from the downforce would do its toll on the high speed areas.
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Old 07-29-2013, 01:58 PM   #9
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Quote:
Originally Posted by 1993ka24det View Post
The problem with running it off of the drivetrain is that the motor is limited to 7500-8000 rpm.
This is solved by proper choice of pulley size on driveline and AC motor. I would mount it either at the transmission output yoke or diff input yoke to keep the additional weight off the nose of the car.
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Old 07-31-2013, 12:08 AM   #10
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Belt regen systems exist for mild hybrids in production. Kits can be purchased for various configurations from various manufacturers. Hardware issues largely solved though there would be a lot of time sorting out details on a solid wheel motor system. Marginal benefits, high cost, tons of time invested. Recommended only for education / development for the hell of it. Equivalent time / money spent on traditional hardware would make a genuinely go fast miata IMHO.

That said, the benefits are in the controls. Potential wheel vectoring, intelligent charge and discharge controls in front of the motor controller make the difference. Good white papers and data on formula student electric (FSE) cars and a few electric race series are available online. If you like this kind of thing, I would suggest a wheel driven approach with vectoring. The belt driven method could be pulled straight from a mild hybrid gm application with moderate integration effort.
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Old 08-01-2013, 03:01 AM   #11
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I have never understood how adding 80hp in electric power increases power to the drive train.

Wouldn't the existing power need to see the current power AND the add on power for it to make any difference.....

Oops, that is confusing.

Does adding 50 Hp via Kers (or whatever) to a 100Hp petrol engine increase total Hp to 150 (ignoring losses). In my head the add on would need to produce more than the original 100hp to add anything to the party.....

or does it only add to the torque figure and not the HP figure....??

Growing up I used to love twin engine minis, dual motor cycle engine (one on each rear wheel) vehicles. Very intriguing.

I always thought that the added motor didn't increase HP as such but did increase something, maybe torque...is that the case?

We have a pretty famous "historic" drag car down here...front engine x 2 rail. It doesn't perform as though it has the horsepower of 2 engines and in drag racing circles dual engines very quickly lost favour.......

I follow F1 very closely and still don't get how an added 80 HP makes any difference to an engine already making 600+ hp.....

I hope this isn't off topic....
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Old 08-01-2013, 03:32 AM   #12
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Yes in lets say Formula 1 80 more HP on top of the 700hp it already has does help. In a sectioning body that measures in fractions of a sec per lap = advantage. Since the motor is directly connected to the engine it will add 80 more hp. In the way I was looking at it, I wanted to add more torque rather than hp. But a motor with 1.21 gigawatts will not make you go back in time.

Kinetic Energy Recovery System - The Formula 1 Wiki

Here is a Jag with a 1.6 liter making 500 hp and two electric motors to help. (I wasn't going to post up the Mclaren P1 or LaFerrari just because that's already been talked about enough)

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Old 08-01-2013, 10:33 AM   #13
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kiwi -
I'm not sure where you learned that, but it's entirely incorrect...

Think about a large breaker bar on a stubborn bolt. You are pulling on the breaker bar with all your might but the bolt still wont budge (and amazingly, your tools/the bolt head are not failing in this scenario) With all your might, you are able to put 300lbs of force on the breaker bar. Now your 6 year old son walks into the garage and sees you struggling, and he's obviously going to want to help daddy, so he walks over to you and starts pushing on the opposite side of the breaker bar with all of his might. He is able to exert 20 lbs of force on the bar. Almost instantly, the subborn bolt moves breaks free.

When your son joined you at the end of the lever, you and he put a combined 320 lbs of force on the lever. Not just 300.

Consider if, in order to increase a 100hp engine to 120hp with an additional engine you did in fact need to add an engine capable of 120hp. Well if you have a 120hp engine, what the heck are you dragging it down with the 100hp engine for? The 100hp engine is obviously not helping the additional 120hp engine.

In each case, you are adding torque, which by definition increases horsepower. The only scenario in which you would not add horsepower is where the added engine is either RPM limited (which means that you have to spin the whole system slower to keep the added engine safe, definitively reducing horsepower) or if the added engine has inertial losses that are so significant that it can't keep up with the first engine - which is generally unrealistic - we would be talking about an engine with a flywheel weight in the hundreds or thousands of pounds.

If you had 10 identical engines and strapped them altogether, the combination would produce 10 times the torque of a single engine setup while being limited at the same RPM. The result is 10 times the horsepower. This of course assumes that we can ignore the power loss associated with the device used to connect all 10 engines.
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Old 08-01-2013, 11:46 AM   #14
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Quote:
Originally Posted by fooger03 View Post
Consider if, in order to increase a 100hp engine to 120hp with an additional engine you did in fact need to add an engine capable of 120hp. Well if you have a 120hp engine, what the heck are you dragging it down with the 100hp engine for? The 100hp engine is obviously not helping the additional 120hp engine...

If you had 10 identical engines and strapped them altogether, the combination would produce 10 times the torque of a single engine setup while being limited at the same RPM. The result is 10 times the horsepower. This of course assumes that we can ignore the power loss associated with the device used to connect all 10 engines.
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Old 08-01-2013, 01:56 PM   #15
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Aha!

So now I see the logic behind the OP !!

Great analogy thank you.
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Old 08-01-2013, 04:14 PM   #16
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Quote:
Originally Posted by fooger03 View Post
If you had 10 identical engines and strapped them altogether, the combination would produce 10 times the torque of a single engine setup while being limited at the same RPM. The result is 10 times the horsepower. This of course assumes that we can ignore the power loss associated with the device used to connect all 10 engines.
See tractor pull multiple insanely powerful engine badassery for example. Try five 2500hp engines strapped together.
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Old 04-23-2014, 05:02 PM   #17
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Any progress on this project? Instead of a belt-driven motor/generator could you use one of the beefed up "start-stop" starter motors? IRRC they are still decoupled like a normal starter but it seems to me that you could setup a speed-driven decouple that would disconnect the motor at a speed above the max RPM of the motor.

I've also thought about installing a motor on a custom diff cover that would connect to the diff ring 180* away from the pinion gear coming from the engine. There are kits out there for Ford Rangers
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Old 04-23-2014, 05:30 PM   #18
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If you connected it to the diff, you would need to make sure your electric motor could spin fast enough to keep up in higher gears, as you would no longer have the transmission helping.

I know you could find out how fast the ring is spinning at 7200rpm in 5th/6th gear with math, but I can't do it in my head.
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Old 04-23-2014, 05:33 PM   #19
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not sure if this would be of any help but a few years back a company was planning to offer electric assist to FWD cars by converting the rear drums to two huge electric motors.
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Old 04-23-2014, 05:36 PM   #20
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You would have to choose a pinion size that gave you the correct ratio for the speed range you wanted and the optimum motor RPM. If you were worried about over-spinning the motor you could add a mechanical decoupler or clutch too.

My thinking is the added torque would be nice coming out of corners or to "torque-fill" while the turbo is spooling up
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