we thought about that, but the reality is that the power required from the alternator is minimal ( worst case, it comes all from the alternator and thats about 1-2hp. in actuality, the battery is charged by voltage drop, so most the voltage drop is small, which means the current from the alternator is fairly low, but goes up as the supercharger is used. the nice thing about this design, is that you never would use the device more than 7 seconds at a time, unless you are drag racing, where it goes to under 15 seconds. Then, the alternator puts the current back at a slower rate during braking or non full throttle situations.

On the track,ive used it for 50 min races, with a battery that weighs only 14lbs!
At Laguna, we have measured that we are at full throttle about 40% of the time over one lap.

we also did a bunch of dyno runs to see if the gains were changed by using a separate power source or by using the battery on the car. there was really no difference in the gains.

Mk

 

Mark, this is very interesting to me. I've thought about why there are not electric charger on production cars. Or why there are not electric motors supplementing turbochargers to reduce turbo lag and spool-up time.

But I have a question: why do you need 48 volts? Isn't there a motor powerful enough that runs on 12V? Like a starter motor for example?

 

Mark, I see where you are coming from with the current low-powered electric supercharger. But with the high-powered ones, I think there is some value here. What am I missing?

Let me see if I can try to understand this. I read somewhere at Zena that an alternator needs 1 hp per 30 amps of output power produced. So if you decide to go with a 48V 100 amp blower, that would be the equivalent of 400amps at 12V from the battery. So it would max out a 100-amp alternator, which would require 3.3hp to run. With a system that generates around 36hp, and extra 10% can be had just by installing this imaginary cut-off switch.

 

part of the problem, is if the traditional supercharger was electrically driven, it would have to run all the time to keep air flowing through the intake. an axial flw compressor can also compress air and provide air flow, but needs to spin at very high speeds, directly (no gearing) a great idea would be to do a belt driven axial flow compressor off a large electric motor. but, for all that mechanics, it would probably be easier to buy/build a traditional belt driven supercharger.

we did a bunch of testing of 12 volt 200 amp controllers and they just couldnt get the speeds we needed out of the compressors. so, when we tapped in on the jet model world, we found 36 -48 volt systems that could run at lower amps and provide more power. This system now requires a complex charging system, with contactors, PLC control, etc to engage and disengage the array of batteries to drive the axal flow compressor (ducted fan)

I think the reason for their lack of use by car manufacturers, is that lag is not much an issue for turbos, and belt driven superchargers are relatively in expensive. There was a company that made an electric turbo for reducing lag . generally it was for the truck industry. they never really took off, yet they were supposed to work.

mk

 

You got it. However, with the 48 volt system the alternator is removed during operation, and when not in use, the batteries are charged via the 12 volt system in parallel. (hence the reason for a switching matrix to do this)

currently, i would think you assesment of the gains are right as well. we are only getting around 10hp max on any application. so, that extra 1hp might be worth the cut off circuit. Its just one more thing we need to add to the kit.

in a perfect world, we could run that 48 volt system, with a step up transformer of some type and use the cut off switch for the alternator, as it would max out at 100amp, and that would cost near 3hp at least. But, that is not an economically feasible option for the design.


Mk

 

What about an solenoid by-pass valve? When the engine is breathing normally, air is routed from the air filter around the blower. When the driver smashes the throttle, the blower spins up and the valve changes direction.

Maybe that's true for the variable-geometry Porsches, but not so true with others. I drove an Eagle Talon in the last 90s and a friends' Subaru flat-4 turbo a few years back. It's the reason why Porsche spent so much time trying to find a solution to it. Still not convinced? Check out the youtube of the Mitsubishi Lancer Evolution MR FQ400 with 400hp and horrendous turbo lag: http://www.youtube.com/watch?v=n_ALKKBr5zQ

 

MK
Interesting.....so your new design is basically a brushless DC jet turbine engine lifted from a model RC jet...... While your at it.....most of those electric RC planes also use VERY efficient & light batteries....way better than NiMH.....last I knew they were past Li-ion and onto Li-Po (lithium polymer) which are very light and have incredible power storage.....they only become unstable and blow up every once in a while.....

I read somewhere that a standard RC nicad battery had somewhere between 1600-2400mah....with Nimh up to 3300mah......but Li-Po's were over 8000mah......

 

Yes its a very efficient design, and packs quite a punch. However, the battery issues now are very expensive to deal with. the switching network, made up of contactors and basically a PLC, is not cheap. However i would be interesting to see what we could do with the lipos. problem with them , is that even though the discharge rates are good enough now. (like with the 8000maH Lipos being near 20c or near 160amps, they cant be charged much faster than 1c or 8amps) thats an issue. But, if you wanted a 8amp hour battery to drop 120amp for 3.5 mins, it would work (and then an hour to charge it )
The Lipos are not cheap either, for this kind of battery, it might be 2-500 bucks depending on the voltage. (cell count) but, you are right, man, they are LIGHT!!! they only blow up when they are being charged incorrectly. (or discharged incorrectly)

mk

 

Thats exactly what the company i was referencing did. they had a bypass valve electronically operated. The company was called turbodyne.


With the turbo lag not being really much of an issue racing, as the rpms are kept very high constantly, it is a big deal for street cars where you are not in the max HP range all the time. adding an eRAM to these cars doesnt really assist with turbo lag too much, although, if we can add 6% more mass flow, there is more mass flow out the exhaust to drive the turbo quicker, but its a small effect. your idea (or turbodyne's) of having a second turbo kick in electrically, makes sense to solve this problem. thats why it was such good idea for the trucker market.

Mk

 

How heavy are these new batteries since that becomes a factor also...

In the current case I don't think alternator cut off is a good idea for a single battery system (especially single small gel battery) for racing since with heavy duty cycle use the battery will fade very fast and will cause engine cut out if you go too far... You'd need a dedicated battery for the fan motors with a priority charging system and ideally a big Ah one if the duty cycle is high... (and then its probably still heavy).

...so trade-offs & extra complexity...

Alan

 

good points

with the current 70amp max draw system, its not a big deal. there is very little loss, and even if it was an alternator cut off system, since full throttle and braking is about 50%, the charging could theroetcialy keep up with the draw. However, you are right, if it couldnt, then it would run fine when not at full throttle, but if the big voltage drop eventually gets to a level beyond 10volts, then you will see engine misfires like you have never seen before. its sucks! ask me how i know!! it cost me a race last year. (had to do with the alternator failing, not eRAM. eRAMs were not running on the car at that point)

the High powered system using a DC bushless motor and separte batteries , will get away from the chance of any engine performance issues, but then the only issue is the battery weight. (which is about 40-50lbs), or if it was in a sprint format (lets say, 2x 8amp hour lipo batteries) the weight would be in the single digit lbs. They are amazingly light) in fact, i could run my car with no alternator with a 16 amp hour lipo array and it could dump 400amps for starting and only weigh a few lbs. 36oz approx.

edit: for road racing, the 35hp gain would be good, but it would be at a trade off with having to add 25-50 lbs (depending if it was 24 volt vs 48volt) that would hurt braking and handling.
I would lean toward using the 16amp-hour Lipo array and do away with the charging circuit . However, I think we are using a 24 volt system now. so, that could be done with 4 x 8amp-hour lipos for almost no weight. and since the lipos wouldnt be charged normally, that would be less weight and complexity.
But, 28lbs and 35hp wouldnt be that much of a big deal and a heck of a lot cheaper and would be self contained as far as charging. (whats the equivilant of 6 extra gallons in the gas tank as far as weight goes, among friends anyway? )

For the drag racing crowd, the lipo idea is a good one. remember, they only need this thing for 15 seconds a few times a day. or auto xing. 24volt 8amp-hour lipo batteries would cost about $300bucks vs two $50 dolllar oddessy batteries. so, $200 bucks more for 25 less lbs. Not bad.

mk