renesisking

iTrader: (1)

For some reason I tend to do my best thinking while I am behind the wheel. Possibly because of my commute or because the greenie in front of me in their Prius was going no more than 42mph in a 50mph speed limit road preventing from getting me to get where I needed to go. I finally got fed up and was thinking about passing the ugly thing but I unfortunately had little room and a turn was approaching. At that moment thoughts about the F1 Grand Prix at Monaco I was watching previous night popped into my head. I believe it was a couple years ago that I heard that the F1 organization was introducing new technology into their already tech filled cars. The system is called KERS (Kinetic Energy Recovery System) and truth be told, it is exactly how it sounds. In essence it works as a typical Hybrid system when it comes to storing and regnerating energy from braking or in F1's case the flywheel as well. In F1, it gives the drivers the ability to use that stored energy from braking as a temporary "boost" in power for short bursts so that they can use it to pass an opponent in order to help them win. I know Ferrari is working on this system and plans on introducing it in their regular car lineup, which brings me to the point I am trying to make. Why not have KERS in your regular sports car??

With CAFE strong arming companies to submit to its regulations, sports cars as we know it are slowly changing whether we like it or not. Raw sports cars are now a rare breed and hybrid powertrains finding their way into cars is only inevitable. KERS would provide sports car a nice boost in power when necessary similar to a NOS system without the drawbacks of blown motors and false egos. With the flexability of using the brakes or the flywheel as a charging system for the electric motor the uses would be beneficial and not just in powergains. Now, don't misunderstand my point. I am by no means saying we should just throw in a Prius drive train in a Mustang and have a good looking appliance, afterall that is sacreligious. What I am trying to get across is that having an electric motor to assist the engine so that you can achieve better fuel economy and more power is not such a horrible idea. If you had asked me this same question last year I probably would have been crying after laughing so hard, however it is something that will probably come to fruitition whether we like it or not. I am all for rumbling V8s, or in my case, high strung rotaries, but having your go and being "green" is not such a bad thing. You can have your cake and eat it too. You can have your 400+hp, and get fuel economy that some may have thought would've been impossible for these big high powered motors. This way, the V8s and other high powered motors can live on and still be enjoyed. I understand the drawback of added weight in the cars with the battery for storing the energy, the electric motor(s) and the corresponding components but in my opinion, it is a sacrifice I am willing to make in order to keep my favorite motors alive in the cars that I love.

Before any of you think that I am a traitor and not a true sports car enthusiast, you couldn't be any further from the truth. I love raw sports cars like the venerable Viper, the Corvette, the Z, etc, but our planets resources are limited and getting consumed as more countries are industrializing and there appears to be no end in sight as more bad news rolls in as talk of electric vehicles becomes a normal topic of conversation in auto forums across the web. What about cars such as the Tesla Roadster, you ask? As it too is a sports car but is all electric. Unfortunately they just don't have the soul and feel of a car with an actual internal combustion engine. Its hard to describe, as any sports car owner would probably sympathize and agree with me. Having the KERS system just provides a little bit of longevity to some of the true enthusiasts that are left remaining in the automotive world. After I die, I don't care what happens, but until then, let me enjoy my sports cars.

I wrote this on a Blog at another car forum I am on, let me know what you think.

ASH8

Good god, I hope not, but I guess when an American "Car Driver" from Top Gear America drives a Ferrari California and raves about its Automatic Gearbox and how great it is, I guess the true rare Manual Sports car is in the past...as are DRIVERS.

To answer your KERS question, I guess COST has something to do with it??

Nathan Atkins

I'm right now looking into making a KERS system using a Netgain WarP 7 and a switchable 48v/72v battery pack.

It would provide peak torque of 65 ft lbs from 1500 drive shaft rpm (about 26 mph with a 4.444 diff) tapering off linearly to 20 ft lbs at 3600 drive shaft rpm (62mph)

The basic idea is to section the factory drive shaft and install the warp7 inline with the remaining first half of the drive shaft. Netgain uses a similar system on freight trucks, but the warp7 is small enough to be mounted to a bracket welded onto our power plant frame.

Power from the engine can be driven through the electric motor even when the system is off (If you wanted to remove the battery pack for say an autocross, to save weight) The electric motor stops providing useful torque at about 4000rpm (70mph)but can be spun to 5500 continuously (about 95mph, a more than adequate limit for a street/autocross car)

Motor weight is 93 lbs and couldn't possibly be situated lower in the car, so CoG impact is negligible and the battery pack can go either in the well in the floor of the trunk or up against the rear seat backs in the forward part of the trunk. battery weight depends on what type of cells but for my power requirements in Lithium Ion it's about 100 pounds. So a total weight gain with wiring and controller heads of about 200-225 pounds (the weight of a fat friend)

Maintaining speed at 45-50 mph, as I do commuting and running by sons to school, requires minimal engine torque, I think this system would allow you to basically let the engine idle along for much of the commute ( you'd need to keep it on for accessory drive, EAPS, brake vacuum, etc.)

Power recovery through this motor is possible and with as much uphill/downhill as there is on my commute, it would be very useful, but for starters I'm interested in just topping off from the garage every night)

So there you have it, additional torque at the speeds I travel most often with relatively easy setup using off the shelf components.

All told this project should come in below $5000 (the cost of a nice turbo setup) At least that's the optimistic figure i pitched to my wife...

Motor Specs:
http://www.go-ev.com/motors-warp.html

and a cartoonish depiction of the system they use on freight trucks:
http://www.netgaintechnologiesllc.com/the-solution.html

Nathan Atkins

A few additional thoughts,

You could use this system to sustain some torque to the wheels during shifting since it is after the gearbox.

you could run Electric only in stop go traffic and save gas and clutch wear

A turbo system stresses your mechanical components more, this system relieves stress on them, (additionally the turbo system adds somewhere around 100 lbs itself) I'm not saying this is a viable alternative to turbocharging, i aim only to point out the performance potential. If you're going to spend 5 grand to increase performance, you could look into 5 grand for a little bit less performance gain coupled with a bit more efficiency.

bse50

225lbs to add nothing? that's a waste!
What kind of "Boost" do you need at 4k rpms? that's barely cruising speed, we make enough power to move the car on the highway and that system would just add marginal power in situations where power is not needed.
It would be ok for a prius or honda insight but i guess they already work that way...

A kers system on a sports car should make more power available on demand where you need it. 7\9000rpms in our case imho. I'd love 40 extra hp to get to the les combes

rotarygod

In regards to what sports cars are becoming just remember that at one time all sports cars had solid rear axles. Today almost none do. Only the Mustang is the holdout but it's debatable whether or not it can still be considered a true sports car.

Sports cars used to only have 2 doors. People call the RX-8 a 4 door sports car. I personally still consider a true full blown sports car to have 2 doors though but I wouldn't say the RX-8 isn't one even though I do believe it always should have remained a 2 door design.

Modern day automatic transmissions are a far cry from what they were 20 years ago. Many of them today are faster and better than any driver with a manual. I personally like manuals out of tradition and simplicity but wouldn't say that the newer ones have no place in a sports car.

The definition of a sports car is evolving and changing with the times. I personally feel a sports car should be light, nimble, fairly small, and simple. Technology is adding complexity. While I feel some is good, in many ways it just makes things worse. KERS would be an example. It may have a neat function but as with full hybrid types of systems it's just something else to add weight and potential issues.

Car evolution happens. In 30 years a sports car won't look much like it does today which isn't very much like they were 30 years ago.

Nathan Atkins

I think i might have made that difficult to understand,

I was trying to point out the Jekyll and Hyde nature of the system...

Make no mistake it is there for efficiency, but also introduces a mild performance gain at low to mid-range vehicle speeds

The motor is in the place of part of the drive shaft and if you can imagine, when you're zinging away at 8500 rpm in first gear the electric motor is turning at drive shaft speed (in 1st gear at 8500 engine rpm would be 2260 rpm) and providing additional torque, which it could continue to do as you shift into second.

Useful torque from the electric motor drops off around 3500 drive shaft rpm which is about 60 mph at which time (if you're going for all out acceleration) you're in the thick of the cars power band anyway just about to hit red-line in second.

For most legal street driving 60 is about all you'll see anyway, and you get a 20-30% boost in fuel economy if you're jut puttering around normally like 30-40 mph. The point is to use the on board electric system to relieve the gasoline motor of a portion of the more sedate side of it's work. The fact that it can give a firm shove at low speeds when you really want it is just gravy

Most of my street driving is between 25 and 50 mph and at just a fraction of the throttle being used:

Example 1:


So it's perfect for saving fuel then, and at autocross speeds, it gives an extra shove!

Example 2:

Nathan Atkins

To reply to Rotary God, I agree with you about the pure sports car ideal, that's essentially what my wife's Miata is, (and essentially what the BRZ were going to trade it for is too)

The Rx8 has been fantastic for me as a family car for my family of 4. It has much of the practicality we need from a sedan.

Thanks to a discretely mounted trailer hitch and a 4'x8' trailer it also serves as my pickup truck when needed. And thanks to a hitch hauler, I was able to take all the things to Ocean City with my family every summer vacation without having to own a station wagon.

And it does all that while still retaining most of the character of a pure sports car.

The idea behind the hybrid system is to address my one complaint about the car which is the **** poor fuel economy. Of course i knew about it going in but now that realize i can "fix" it, what's not to get excited about?

The 8 may not be pure, but it suits all of my needs for automotive grunt work while still being just a little naughty and fun.

besides it'll be a fun mod to engineer and if it isnt what I'm hoping it'll be I imagine i can ebay the components and say i at least tried it. That's the Worst case scenario.

RIWWP

iTrader: (2)

Nathan,

I was researching the Warp series motors just last week. No space or funds to do much about it, but I've always thought that there was potential to couple the concept of the turbocharger (energy recovery from waste heat) with the in-line electric motor. Basically, rather than using a battery pack or engine-driven generator, use the exhaust stream to drive the electrical generator. Some level of electrical controls would have to be in place of course, but basically rather than using the waste energy to feed more air (and more fuel along with it) into the engine, use it to provide power directly to the drivetrain without the extra fuel. More exhaust flow (from more throttle) = more power to the drivetrain at no additional fuel cost. Hybrid, but using it in a way very few enthusiasts would object to.




Even if that's too much of a complication, what about using a generator off of the exhaust flow to power the electrical components of the car? Remove the alternator and all the drag that produces. Papers out there indicate running without an alternator's drag is an efficiency improvement of 3-5%.

Nathan Atkins

That's very clever outside the box thinking, you'd need to gear down the turbine a whole lot, bringing about 120,000 rpm down to about 4000 rpm for the generator, a set 2 axially paired low mass gears (perhaps a gearbox from a centrifugal supercharger would work, if it could take the heat) should get you there, as long as there is good thermal separation between the hot turbine and the generator i think this is a good concept for range extension.

You would have to use a small turbo to keep it spooled up while cruising and a waste gate which is massive enough to pass a nearly stock flow of exhaust gases to keep the turbine from acting as a choke point in the exhaust stream when your batteries are topped off.

you would need a solenoid actuated waste gate since there is no boost pressure to regulate it.

it's a lot to wrap your head around but lord knows the RX8 throws more energy away via the tailpipe than pretty much anything else on the road.

It also wouldn't be suited for what i had in mind since i don't even really need range extension with my 30 or so miles of driving per day and I'd top off from the house power at night.

Thanks for the response, I like your idea and i hope that you get a chance to explore it in the future.

RIWWP

iTrader: (2)

Yeah, we have an advantage here over piston engines, in that we have much more exhaust flow than piston engines. The design of the exhaust impeller would a large part of the R+D, as the difference between ~5g/s at idle vs ~40g/s at cruise vs ~210g/s at full throttle means that for best benefit you would have to compound the effect as much as possible low, but have it scale correctly so that you have little to no compounding at higher flows, and even the bypass/relief to prevent a restriction. And you are correct about the heat shielding, since the generator itself would be generating quite a bit of heat as well, and the exhaust heat would compound that badly.

Even if all of that could work correctly, getting the motor geared correctly would be important, as this would be much more likely to be used in a performance oriented environment, so capping a top speed to ~95 to protect the motor wouldn't be realistic. The nature of greater torque at lower motor RPM means the torque boost would be the greatest in 1st gear, decreasing with each additional gear.


I've even though about 'what if' there is a way of actually feeding the exhaust flow directly to a drive-shaft mounted turbine. Steam engine concept of using the expanding hot gasses to provide direct pressure to the driveshaft. The problem with this is managing how much backpressure the engine is taking, and if that pressure is even enough to provide a boost of torque through the drivetrain before it hits harmful/power-sapping levels on the engine. Likely answer is 'no' here


Another idea I've thought of is using a different 6 speed transmission. Gears 1 through 5 go to the normal output shaft for normal power, but gear 6 has a different output shaft to an electrical generator, and the ECU shifts to a power-generator mode, and the power from the electrical generator gets fed to the in-line electric motor. Full petrol burning enthusiasm for the first 5 gears, series hybrid economy for the 6th gear.



And do we really need to have an "in-line" motor? What if we just use a differently designed driveshaft that IS the core shaft of the electric motor. Build the needed motor components around the driveshaft itself. You could even, in theory, have the components around the driveshaft slide forward or backwards as needed to "engage" or "disengage" on the matching components mounted to the driveshaft. Could work for any of these ideas, including yours. Effectively removes the electric motor from the drivetrain when speeds exceed motor limitations, or power demand would be either damaging or net power loss by keeping the motor engaged.


Plenty of crazy ideas go through my head


For me, any of these concepts are largely performance oriented, because I don't care all that much about the mileage. Any mileage considerations are simply because it would give a boost to one of the rotary's weakest points and improve it's marketability to people that actually do care.