Geoffrey

You can contact Automobile Associates in Canton, CT (860-693-0278) who have a number (10 or so) 964/993 cars equipped with the TPC superchargers installed. Some are US Cup Cars, some have factory chips, some have Cup car chips, some have aftermarket chips. One of the cars has been featured in a recent Excellence article and is well tracked. All of the cars produce between 305-330rwhp depending on configuration (pully size, chip, intercooler, etc.) Some have over 3 years of DE and track usage on them.

As mentioned earlier, I have seen intake air temp issues, even with the superchargers and I was not able to overcome the issues without employing a similar strategy as TPC where fuel in the intake manifold cools the charge air temp. The issue is that the supercharger is a huge heat sink and unlike the blowers found in a muscle car with carburators, the fuel does not go through the blower so there is no cooling effect.

A further datapoint is that I was working on a 32valve Mustang Cobra today which comes with a supercharger from the factory. Using an OBD II programmer to alter timing and fuel, the HP ranged from 440hp on the first pull to 370hp on the 3rd pull with the same programming. The difference being the elevated intake air temps and heat soaking of the engine which happens very quickly. This is just to say that the heat issue isn't specific to the Porsche engine. Obviously supercharging works, however, it just needs to be approached thoughtfully.

Smokin

I read about a similar issue in a recent magazine... I can't remember which. (Excellence I think.) They talked of a 993 that had similar issues as you describe and sorted it out to be a needed remapping of the chip to accept pump gas with the supercharger. Seems that after the remap... They were golden.

I know that there are potential issues in supercharging... I'm keeping my options open... But the draw is there... At least for me.

tonytaylor

Thanks for the reply and explanation Geoffrey.

Interesting to see the tracked cars running ( relatively) low hp

shesminetoo

If you're in Australia and interested in purchasing one of these here is a link thats current:

http://carpoint.ninemsn.com.au/Deskt...ias=carpointau

The guy has done a magnificent job by the look of it! Not a bad price either, considering the amount of money that's gone in. (Remember it's Aus$)

Cheers!
Frans

PS: If the link doesn't work, just search for 964 on the site.

bzh on the loose

geoffrey,

i am very interested in understanding and "solving" the air intake temperature when using a blower. I am NO mechanic, but like to understand how things works... so don't be offended if my questions-suggestion are a bit "naive"

in some turbo installation (most nowadays actually) you have an intercooler which reduce the temp and then allow to have more air suck by the turbo. Would an intercooler solve the temp issue?

would it be possible to oil-cool the charger itself, admitting that such a charger exist?

thanks for taking time to explain why none of those solution works... because i guess the pros would have thought of that long time ago!

Heirsh

Its been a while since I read it, but I think TPC offers an intercooler option. They also increase the hp at the same time, so probably similar problems. Now if they left the hp alone and added an intercooler...

just speculation. I'm sure they would be glad to burn the chip (program the systems, whatever) the way you want.

Red rooster

There seemto be some dubious bhp numbers floating around on this topic.
With stock 11:1 compression the maximum boost that can be used on pump gas at the most detonation sensitive area ( about 4000 rpm ) is around 5 lbs.
With a linear supercharger this sets the boost limit across the rev range.

Atmospheric pressure is about 15 lbs absolute , so the increase in pressure is 33% . With no charge air temperature increase, this is also roughly the power increase .On a 250 bhp motor this is + 83 bhp , so up to 333 bhp absolutely maximum.
Screw type compressors are not too efficient thermally ,so roughly 25 of the 83 bhp is lost due to temperature rise and reduction of compressed air density.
Bottom line is that anything over 310bhp measured , with this type of linear supercharger is OK.
Where the impression of big numbers comes from is that the torque will rise by about the same 33% .
If the compression is lowered to allow more boost then more bhp and torque will result, or if a square law centrifugal compressor is used, the 4000 rpm
5 lbs, is not the top end boost limit.

Sorry to sound like a lecture but it annoys me when basics are ignored and dreams become facts !!

Just my $0.02

Geoff

Geoffrey

I have corrected the post above, the 305-330hp is to the wheels, not the flywheel as measured on a Dynapack dyno. The base pully for the TPC kit produces peak boost of about 6psi and drops to about 4psi near redline. Since a supercharger compresses the air (like a turbocharger), the air is heated up. If you cool it with an intercooler, then you can increase the boost pressure slightly which produces more power. If you simply bolt on the TPC intercooler (air to water) you will actually loose power due to the restriction (pressure drop) the intercooler causes. If you install a smaller pully you will raise the speed of the supercharger and will run more boost, and therefore more power.

As Geoff mentions, the superchargers are not that efficient and they produce a lot of heat so the entire unit including the intake manifold.