graham_mitchell

Does anyone know of a "twin screw" (aka Autorotor/Lysholm/Whipple) kit for the 993?

If I were to supercharge my car (and I am very, very tempted) I would also go for the "twin screw" variety supercharger.

Advantages are*:
Incredibly high adiabatic and volumetric efficiencies
Positive displacement design
Very flat efficiency curve combined with positive displacement design gives the most achievable torque of any method
Instant boost
A true compressor
Direct drive from the crankshaft
Compact and lightweight design
Virtually silent operation
Low temperature increases during operation
Very little power consumption
Unique combination of low rpm torque and high rpm horsepower due to the screw compressor design
Have the ability to run from 1 to 60 lbs. of boost
(* see <a href="http://www.superchargeronline.com/techarticles_detail.asp?RecordID=9" target="_blank">http://www.superchargeronline.com/techarticles_detail.asp?RecordID=9</a> )

Examples of this style include: Opcon Autorotor and Whipple.

The TPC kit uses an Eaton Type 90, which I believe is a 'roots' type - reliable, good low-end boost but with the disadvantage of rather high discharge temperatures.

Jack Ennuste

Graham,

look at this article:
<a href="http://www.rsamerica.net/articles/member/zane_d_article.htm" target="_blank">http://www.rsamerica.net/articles/member/zane_d_article.htm</a>

<img src="http://www.rsamerica.net/images/gallery_pics/zanedofok3.jpg" alt=" - " />

If it fits 964, it fits 993???

TPC uses Eaton 90 supercharger:
<a href="http://www.automotive.eaton.com/product/engine_controls/M90.html" target="_blank">http://www.automotive.eaton.com/product/engine_controls/M90.html</a>

graham_mitchell

Tänan, Jaak. I read it, but it is unclear whether it was a custom installation or a kit. There was one clue I saw which I hadn't seen before: it is described as "German Auto's Whipple system".

Chasing that up now

johnfm

Graham

if you find anything out: re whipple kits for 964/993 can you post it or e-mail me.

Thanks

Jack Ennuste

Graham

I frankly believe that You have worked throught massive amount of supercharger data. But still I recommend reading about Eaton roots type supercharger. Point is, that Modified Roots type charger is almost like Whipple charger, but read Yourself:

How is the Eaton supercharger different? The Eaton supercharger is essentially a Roots blower pump, with one substantial design wrinkle; each rotor has been twisted 60 degrees to form a helix. The two counter rotating rotors have three lobes, which intermesh during operation. These twisted rotors, along with specially designed inlet and outlet port geometry, help to reduce pressure variations resulting in a smooth discharge of air and a low level of noise during operation. This arrangement also improves efficiency over traditional Roots superchargers. With helical rotors and an axial inlet the Eaton supercharger can be spun to up to 14,000 rpm, thereby reducing package size.

<img src="http://www.automotive.eaton.com/images/products/diagram2.jpg" alt=" - " />
Modified Roots type (used by TPC)

full article: <a href="http://www.automotive.eaton.com/product/engine_controls/whysuperchargers.html" target="_blank">http://www.automotive.eaton.com/product/engine_controls/whysuperchargers.html</a>

Tim Ashfield

You can tell it's cold and wet and icy out there and you guys can't (like me) drive your 993's enough - your thoughts drift toward yet more speed and of course the $$!!

Have fun and spend wisely.

Mark Budgen

Jack, Graham,

I believe with the twist lobes the eaton is around 65ish% efficient against the whipple at 85ish%. I've been running a TPC kit for about 18months at 9lb with a small intercooler and water injection to keep everything under control. Could probably have down without the intercooler with a Whipple. But at the time I didn't know about twin screws.

Mark.

Jack Ennuste

Tim,
You figured it out. If You followed the FIS cross country skiing World Cup event last Sunday, You know what is the wether here in Estonia. It was delayed a day because of -24 degrees C.
So, lot of extra time to spend here.

Tim Ashfield

Jack,

-24 yikes! We had a few days last week when it was freezing or a few degrees below but I really don't want to think about -24!I hope the car is tucked up somewhere warm.

<img border="0" title="" alt="[Eek!]" src="eek.gif" />

YellowC4S

ok, so where can I get one of these whipple kits? how are they priced in reference to teh TPC kit?

graham_mitchell

YellowC4S:

Well that was the original question!

The twin screw superchargers are easy to find on their own, but a complete kit would make life a lot easier.

WillyC4S

Graham,

I've been thinking about adding a supercharger lately, must be getting used to the HP.

Does the twin screw supercharger have some of the upper end limitations that other supercharger designs have? From what I've read about superchargers vs. turbochargers is that superchargers operate better at the lower end vs. turbochargers which are better at the higher RPM's. I'd like a design that's biased for the higher RPM's.

Mark, what kind of power are you putting out w/ 9PSI? How's the top-end compare before and after the TPC kit? Is most of the improvement at the bottom end?

Thanks,

*****

graham_mitchell

Jaak, thanks for the interesting link!

----------

*****,

I will leave this to the experts to answer properly

I believe that the twin screw designs are the most efficient of the superchargers.

AFAIK, superchargers have many advantages over turbos (e.g. easier install, cheaper, no turbo cooling problems, better discharge temps, no turbo lag, flatter torque curve, always on boost, better low end performance) with just one disadvantage - the peak power increase tends to be higher with turbos (at the same boost) due to the lower parasitic losses.

For street cars using the complete rev range, the supercharger should be faster and more driveable with all the other advantages.

For circuit use where the engine is always in the peak rev range where the turbo shines, the turbo should be the better solution.

There is no right answer - it boils down to personal preferences and intended use of the vehicle.

Mark Budgen

*****,

since I speeded up the SC and added the intercooler the top end seems to have got better when compared to low end at 6lb. I don't know why. However with a tip I'm now putting out about 320 at the wheels.

Cheers, Mark.

Jack Ennuste

Guys

I like supercharger especially because of low grunt torque. You can hit the gas at any revs and get INSTANT acceleration. I drove 996 TT and surprise-surprise, in some real-world situations it is slower. Because of turbo lag on low rpm-s.

Supercharger and turbo are two totally different animals.

One non-technical differentiator -- price. SC is a lot cheaper. Total budget around U$ 7 K.