[Twinscrew928]

You've obviously taken a lot of time to develop your system and I bet it hauls ass. But this just doesn't quite cut it for me. Your idea of fact leaves a lot to be desired. Can you please address the following?

Originally Posted by Herr-Kuhn

Myth 1: The twin turbo system will cost 2X what a supercharger system will cost.
Fact: No it won't!

How can this be a fact? How much? What will be included with your price? When will it be available for purchase?

Originally Posted by Herr-Kuhn

Myth 2: Turbochargers don't make the midrange power of a supercharger.
Fact: This depends on the supercharger used and your definition of "mid-range"....

Generally I agree with the above information and consider it to be fact. However, as with any system, part of the design requires one to select an appropriately sized "pump," turbo, twin screw, or centrifugal. You suggest that one can over-rev a supercharger, but not a turbo. Just like you selected a particular turbo per your design requirements, the backbone to any supercharger design is the size of the supercharger. To date, I have yet to hear of anyone using an undersized supercharger on a 928 and over-revving it. That's a fact.

Originally Posted by Herr-Kuhn

Myth 3: The twin turbo system won't make any more power than a supercharger system
Fact: First off comparisons based on this statement must have several variables which are fixed, those being the same engine, same fuel, same boost pressures, same compression ratio, etc. When one says "it makes the same power as the turbo car", ask them at what boost pressure that power was made and ...

You're right that every system has its benefits and detriments - that is a fact. I believe I could probably hit your number RWHP numbers with the same or less amount of boost. A twin screw setup will make about 440RWHP (dynojet) at about 6.5 psi. At 9 psi, I expect to hit 500RWHP. If I were to go up to 12 psi, I suspect I would hit 560RWHP, but I don't need to hit those kind of numbers because my boost comes on for all intents and purposes... instantly and does not need to build progressively with RPM unlike a turbo or centrifugal SCer. Fact is, this doe not mean my setup is better or worse, just different characteristics.

Originally Posted by Herr-Kuhn

Myth 4: The twin turbo system places far more heat into the engine bay than a supercharger system
Fact: Is this statement based on running at the same HP level or the same boost pressure level? Since the turbo engine doesn't have to burn as much fuel as supercharged engine to make the same power, there is less overall heat produced per pony...

Where are your facts? All you post here is conjecture. The fact is whenever you compress a gas you will generate heat in the process. Turbos are no different. Compressing air to 12psi will generally generate the same amount of heat whether it's done via a turbo or a twin screw or a Centrifugal. A belt driven SCer will use fractionally more fuel, less than 10%, but with the added back pressure of a turbo, the exhaust heat is held captive longer than on a SCed engine. Which adds more heat? I can't say, but you seem to imply that it is equal or less with the turbo. Where are your facts?

Originally Posted by Herr-Kuhn

Myth 5: A turbocharged 928 will burn up exhaust valves while one with a supercharger system will not.
Fact: Is one supposed to assume a supercharger places no additional heat on the exhaust valves as compared to its normally aspirated sibling? I'm still perplexed on this statement. Granted there may be slightly more heat on a turbocharged system exhaust valve compared to a supercharged system exhaust valve...

Well here you say that the turbo does make more heat on the valves, so the added fuel consumption by your own words is less of a heat concern than a turbo. Porsche certainly felt it necessary to do something on the 951 to protect against heat. You don't seem to address this in any fashion. Maybe it won't be an issue, but until there are several tens of thousands of miles on your system on a 928 without issue, I think it would be unwise to simply ignore the real possibility.

Originally Posted by Herr-Kuhn

Myth 6: The twin turbo system forces you to cut "lots of holes" in the engine bay.
Fact: Two 2.5" holes are required to get the intercooler discharge pipes back into the engine bay. I'm sorry, I was not aware people cherished that 10 square inches of material so much.

Some people don't like to cut their cars up. The fact is that your "kit" requires its owners to do so. They will never be able to return t back to stock. Zero holes in my car!

Originally Posted by Herr-Kuhn

Myth 7: The twin turbo system will require more maintenance than a supercharged system will.
Fact: This one really confuses me . The turbocharger is such a simple device as the rotating assembly is one part housed in dual ball-bearings. A supercharger has more moving parts, especially a centrifugal supercharger with its overdriven gearing system. Additionally, any belt driven pump will require retensioning of the belt and replacement of the belt. I can guarantee there will never be a broken crankshaft bolt, broken crankshaft pulley, slipping belt or broken belt with the twin turbo system. There is no additional maint. required with the turbocharger beyond routine oil changes. It's really that simple.

Let's see... a belt needs to be replaced every two years at most on a SCer system. Cost of a belt is at most $40. That's $20 per year. You state your system requires more frequent oil changes. Let's assume one additional oil change per year for the sake of argument. With 8 quarts of your favorite synthetic oil for $5 a quart, that's an additional $40 a year (without filter). By my calculations this means a turbo setup costs at least 200% that of a SCer system for annual maintenance.

Originally Posted by Herr-Kuhn

Myth 8: The twin turbo system suffers from excessive "turbo lag"!
Fact: This has to be the most over-used statement by a supercharger salesman . True, a twin screw pump makes nearly immediate off-idle boost which is why they are really nice for stoplight to stoplight racing. On the other hand, a centirfugal supercharger simply can't make any appriciable boost until it is a full 2/3 up the RPM scale. When you hear statements like this ask them how much boost their system makes and ask to see the boost curve the system produces on your engine. Then remember that torque (and consequently HP) at that point in the speed range follows the manifold pressure (minus any power robbed to drive the pump).

The only fact that I see in this statement is the one about a TS making more boost off the line. The fact is there is lag with a turbo. Making lemonade out of lemons by saying it helps to make the car more streeatable is like playing 3-card monty with your customers. Why not just admit that there is lag, address it in a professional manner and let people choose whether its of concern to them or not.

Originally Posted by Herr-Kuhn

Myth 9: It's simply not worth it!
Fact: Beauty is always in the eye of the beholder. In my opinion the twin screw system makes a nice functional and aesthetic addition to the engine bay of any 928. Of course, I also think the twin turbo system also makes a very nice addition to the engine bay of the 928.

Finally, something that is factual.

Originally Posted by Herr-Kuhn

Myth 10: A centrifugally supercharged car is faster in the real world than an equally boosted turbo car!
Statement: Prove it.

Top fuel dragsters have what kind of boost generator? Oh yeah... belt driven superchargers! And on many 928's we all run out of gearing before we run out of power, so I guess there's no real difference on the top end - so I guess in that regard they're equal.

Originally Posted by Herr-Kuhn

Myth 11: The centrifugal boys are in reactionary mode
Fact: Well, I guess this in one myth that actually IS true!

Just trying to keep you honest, although I'm not centrifugal...

Originally Posted by Herr-Kuhn

Additionally I'd like to add that if people are so sure about all of their fabricated negatives of my system, why don't they come here and state these negatives to me? I think I'm pretty reasonable and use facts and not opinion to back up my statements.

I'm not knocking your system - what you've done probably came close to bankrupting you! Kudos on your accomplishment! Your system makes gobs of power... fah sure! But your use of conjecture intermixed with opinion does not constitue fact.

Originally Posted by Herr-Kuhn

I would also recommend that before you make a significant purchase like this to go on and drive an equally prepared car with each of the three systems before you purchase. Come to KY any time if you would like a ride in my car as part of your comparison. Then buy what you want to buy, we live in a free market economy!

We should all be happy right now, it's nearly Christmas!

1000% agreed!