On eBay - 911/944/928/Boxster Supercharger - turbo
 

Hey all,

I found this Supercharger on ebay. Is this for real? will it really work?

Has anyone seen, heard or better yet, used one of these things?

http://cgi.ebay.com/ebaymotors/Porsche-911-944-928-Boxster-Supercharger-turbo_W0QQitemZ8000237330QQcategoryZ33741QQrdZ1QQc mdZViewItem

:confused:

Thanks,
Will

Youll just throw away your $140 for a useless "Leaf Blower"...LOL...There are absolutely no benefits from installing this POS device.

If it sounds to good to be true.....

Appreciate the input. I like the part in the description that states that when you need it you "turn it on." Wouldn't I want it on all the time?

I think it was crazy talk, but I had to ask.

:cheers:
Will

Interesting mix of feedback for this seller.

1. I always find it surprising that people will still buy from sellers with so much bad feedback (this guy's isn't as bad as many power sellers I've seen), but 32 people in the last 12 months did not have a good experience.

2. It seems he sells superchargers for many makes and models and surprisingly some folks felt a power increase. Suspiciously, all the item #s are "private" so perhaps it works for some cars. However, a good number of people left positive feedback before installing, another unexplainable phenomenon.

3. Got a good laugh out of this feedback:

"Pretty good product got more power with it switched off"

Buyer muffdivr69 ( 3 ) Aug-18-05 13:56 Private

LOL!!!
Gota love the feedback:)
It should work how ever the key will be the blower. It has to spin up fast enough(not normaly a problem) most important have a high enough flow rate. I doubt that one could realy make 2psi of boost.
Just my 2 cents.

Richard

Hi,

Sorry, but it's mostly a waste of time. As one mentioned, it is a Leaf Blower.

There are no free lunches where making power is concerned, everything is a trade-off. If it were that easy, the Supercharger and Turbocharger would have been put to death years ago, in favor of an electric induction system.

Turbine (fan) design is a very intricate science. It would be very easy to have this 'Fan' cavitate long before it ever produced any appreciable boost. Also, for it to be effective, it would have to draw so much electrical power that every other system in the car would fail and your alternator would burn up in a block.

Just as an example, take the Supercharged Jaguar XKR. At full boost, it produces a net 390-400HP, but the parasitic draw of Crankshaft power by the Supercharger is 86HP. If you had an electric Fan which was more efficient, even twice as much, it would still need a 43HP motor, can you imagine the power draw of this thing?

I suspect most of the positive feedback was done either prior to installation of the device, or it's just a Placebo Effect, because the Science simply doesn't add up.

Happy Motoring!...JIm'99

Let's not forget to say that lots of unscrupulous Ebay powersellers have numerous login names and buy their own product to build positive feedback. It ain't right, but it's done all the time.

There is an electric supercharger that has been shown to work. It is mostly for smaller, smaller than the boxster, engines 1.4-2.0 's. Adding the electrical capacity(weight) negated the effect of the horsepower increase. This leaf blower looks nothing like the real electric supercharger I saw documented.

Jim 99 from what you are saying it would take a Honda CRX just to turn over the supercharger on the xkr???

Hi,

Well, not exactly, but essentially, correct. All the ancillaries on an engine cause a Parasitic draw on the Crankshaft which powers them.

For many, this draw is variable (on some, like the PS Pump and AC Compressor(when on), the draw is more or less constant). The Waterpump and Alternator for instance, draw varying amounts of Crank HP depending on the load put upon them.

A waterpump draws around .5-1 HP at idle, but may jump to 6HP when it is really churning due to the increased resistence of the coolant to the impellor blades.

An alternator draws maybe 0.1 HP at idle w/ no electrical demand on it, but can draw up to 10 HP under full load.

The same is true of the Supercharger. At idle, it draws next to nothing because it has a variable clutch to allow it to Freewheel, but the power draw increases at it spins faster and experiences more resistance by the air it's compressing. On the example I used, the XKR makes 400 HP at full boost. Compare this to the 290 HP produced by the NA XK8. But, this HP gain is a Net gain of 110HP. The Supercharger draws 86HP in making this additonal 110 Net HP, so in total, it makes 196HP. It makes about 2.5 times what it draws, so it is a positive compromise. This is one of the advantages of a Turbocharger, that it doesn't consume Crank HP, the energy it makes is essentially Free. And, unlike a Supercharger, which is limited to the Crank HP available, the faster a Turbo turns, the more power it makes, allowing it to turn even faster, allowing it to make even more power - the limiting factor here is turbine blade efficiency. But, of course Spool-up time (Lag) and excess heat are the most apparent trade-offs, or disadvantages.

Motive force is fairly easily calculated. 745.5 Watts is equivalent to 1 HP of Work. In my example, I stated that the electric motor driven fan may be twice as efficient as the mechanical Supercharger (this isn't so, but I wanted to add some perspective to the example).

Anyway, twice as efficient would mean it would draw only 43 HP to make the same amount of boost. Doing the math, this means that it would take 34,293 Watts of power to do the same work. In converting the Watts to Amps (not an exact conversion, but an accepted way of averaging it) the equation is Watts/Volts=Amps. So, 34293/12= 2,857.75 Amps.

There is only so much Work available from the 120 Amps the Alternator creates. And, since the Maximum Output of the Alternator is 120 Amps, you would need the equivalent of almost 24 Alternators, dedicated to only the Supercharger, to accomplish the same work (and remember, this assumes a 2X efficiency) as a mechanical Supercharger. Now, if the Alternator drew 10HP at max Load, and you needed 24 Alternators (all at Max Load), these alternators combined would draw 240 Crank HP to spin them, while the Machanical SC only draws 86HP, so clearly this is not nearly so efficient (and remember we assumed a 2X efficiency). This is why Electric Superchargers are not really feasible. So, there really is no way that an Electric Supercharger can support the claims made by the manufacturer.

Happy Motoring!...Jim'99

The one I saw only claimed 1-2 psi boost and it delivered. You are talking the extremes at 400hp or a net of 110hp.

I repeat again, it was not the so-called SC in this post. This is just some fan/blower and most likely would do nothing but at worst would come apart and go downstream.

Why would anyone think of ruining the efforts of the best german engineers by putting anything spawned from/for ebay on their car.

Hi,

I understand what you mean, and I didn't say anything negative about the one you're describing. The XKR produces about 12PSI on maximum boost unlike the 1-2PSI you describe. But, the science stays the same.

So, 1-2PSI is possible without installing an Electrical Power Station under the hood to power it, but probably just. This is probably why the available boost is so small, anything more and you run into trouble.

Happy Motoring!...Jim'99