Supercharging a 3.2 - Questions

[Mike Feinstein]

Haven't seen this rehashed in a while so I thought I'd rattle the tree to see if some more information falls out.

Of intrest is the low pressure Eaton (Whipple) unit by SOK that provides about 345 hp at .7 bar of boost. It will supposedly fit under the stock Carrera tail (or none at all), and only requires relocating the AC condenser to the rear fender well. As a light boost setup, it's supposedly not too hard on the engine. I don't feel the need for 400+ hp.....345 would make me quite happy!

As I understand, the kit sells for about $7400 complete (old info). Is this a DIY project? Has anyone done it? OK, does anyone know anyone that's done it? How is the performance and reliability? Etc., etc., etc.

Spending way too much time day dreaming about more horse power. I like the reversability of light pressure supercharging for resale reasons. Did some searching but there's definately a shortage of first hand accounts on this BBS. Is there somewhere else that the Supercharger guys hang out?

[89911]

$$$$$$$=???????

[Mike Feinstein]

Oh, come on Michael.....a 3.6 swap a la Timmins would run about $13,400, less the resale of my 3.2 (4-5k), assuming all went smoothly. And then, it's not reversable and takes hp from about 220 to about 280.

This SC option is interesting as it provides 345 hp for about $2k less than the swap....and it's reversable. I know that my engine is tight and solid with minimal oil consumption...a swap comes with questions in this area. So, in Porsche terms, the SC seems to offer more bang for the buck. No?

FYI. . .here's some information from Paul Burch of SOK:

LOW-BOOST AUTO-ROTOR KIT FOR THE 3.2

This kit is essentially the same horsepower, @ 350, as the Paxton kit,
but
it uses the Auto-Rotor supercharger running at 7 - 8 pounds of boost.
The
price is $7400.

The advantages of this kit over the Paxton kit are:

a. It comes on a much lower rpm, meaning that although the maximum
horsepower is about the same, the car is much quicker.

b. The Auto-Rotor is somewhat quieter and smoother than the Paxton
unit.

c. The Auto-Rotor kit with its small intercooler WILL FIT* under the
stock
rear decklid, no tail at all. The Paxton kit, which is not
intercooled,
requires a Turbo tail.

* - Requires that the a/c condenser be relocated into the left-rear
quarter
panel like a C2/C4.

[1fastredsc]

345 hp from a supercharger is a pretty big gain, I don't know about the technicals, but .7bar of boost is about 10psi, which is a lot with the high compression of a carrera motor. Does this kit include lowering the compression of the motor or is it a strict bolt on? The only SC carrera i ever new of was at 6 psi and made like 250 at the wheels or somewhere around there.

[dd74]

Hi Mike: I have not done this project personally, nor do I know anyone who has. The closest I've come to a pressurized Porsche engine, was RFNG's turbo SC, which, aside from a stuck throttle, seemed to work quite well. With that said, it seems to me that the feasability of such a project is good. There have been several threads on the subject, and from what I glean off them is one has to be prudent with the boost so that the engine will stay together. Aside from that, much of the stock 911 componentry, including the clutch and gearbox, will hold up fine.

Superchargers of Knoxville sell two versions: one a Whipple, the other a Paxton. The Paxton is what I would use on an early 915 gearbox, particularly if it is equipped with a small ring and pinion. From what I understand, the Paxton's torque nature is to not provide the entire amount of torque low in the power range, which is where the small ring and pinion is most susceptible to breakage. In your case, if you have a G50 or well-operating late-model 915, you should be safe with the Whipple, which provides a flatter torque curve that comes on earlier.

Hence, the nature of the two units are this: the Paxton has more of a turbo-like effect; lower torque, but comes on strong as RPMs rise. The Whipple creates much, if not all of its torque, early on in the rev range, creating power more akin to a V8.

Good luck. I'd be interested to read what you decide.

[ChrisBennet]

While the supercharger setup is reversable what are you going to do with the SC when you're done?
-Chris

[Mike Feinstein]

Good question.....since it wouldn't add a nickel to the value of the car (it might even make it harder to sell), it could be resold to someone else longing for better performance from their 3.2. No plans to sell in the forseeable future anyway but it'd be nice to return it closer to "stock" to expedite the process when that day comes.

[mm86911]

Originally posted by ChrisBennet
While the supercharger setup is reversable what are you going to do with the SC when you're done?
-Chris

EBAY! . . . and I'll let you know exactly what you reseve should be

Mike - not sure I ever shared the story of riding in "The Beast" in San Deigo last year when it was supercharged - serious torque monster!!! See this thread for the latest mods (twin turbo) and send Mark an email - he's a great guy and an excellent tuner/fabricator.

Natchamp's Latest

[jyl]

You might check if the heater blower and associated tubes need to be relocated. Seems they are where the supercharger needs to go.

When I first joined the BBS, I spent a lot of time searching the BBS, Rennlist, books, etc about the SoK supercharger kits for 3.2s. There isn't much first-hand user info out there. But I didn't run across any horror stories and did hear of - second-hand, usually - SoK kits that were installed and apparently worked.

I would be very interested if you, or someone else, were to try this kit and and report thinking, progress, cost, results, etc to the BBS. It would certainly be new and interesting information.

Incidentally, I note that Protomotive's Stage 1 turbo kit for the 3.2, which install on a motor with stock internals including compression ratio, uses only 0.5 bar boost. The Stage 2 kit which adds an intercooler uses 0.7 bar.

[masraum]

I have seen emails and dialogged with someone on the Rennlist and know of another person, I think, on the Rennlist who added superchargers from SoK and ended up with major blowby at the rings after a while. I emailed one of them when he started asking about the high pressure in his oil tank to ask about the state of the engine before he added the s/c thinking that maybe it had been a tired motor, but he detailed the rebuild that accompanied the s/c install and to me it sounded like it had definitely been done right, so it may be an issue with this type of setup.

I did a search on the Rennlist for "3.2 supercharger" and a few messages down found a thread called "oil smoke" which was about a pressurized crankcase due to blowby at the rings and then another thread called

" Oil breather blow-out diagnosis!"

What follows is a reply to a message. So that's at least three people with the same problem. Apparently the cars run well, but I'd not want this issue, it can't be good in the long run.

I'm in the same situation as you, my '88 Targa is also supercharged and has
the same problem with the oil vent. I went to a well known mechanic [and
friend] in the area and had him look at it and his determination was that
the supercharger was pressurizing the crankcase thus causing this problem.
Like you my car runs great, I just need to find a way of venting the tank
without all of the mess.
Lane


----- Original Message -----
From:
To: "911/993/996" <911@rennlist.org>
Sent: Friday, March 29, 2002 2:24 PM
Subject: [911] Oil breather blow-out diagnosis!


> My trusted P-car tech. diagnosed my oil tank breather blow-out as
> follows:
> Because of the high boost pressures in the supercharged engine, air is
> blowing past the rings and pressurizing the crankcase thus forcing
> air/oil out of the breather. He said the the crankcase normally runs in
> a vacuum but when he measured its internal pressure, he got 20 psi. He
> thinks new rings are the answer but is not sure. The engine has 20K
> miles since a complete split-case rebuild which included new pistons,
> cylinders, and rings. Since so many on the "list" run turbocharged cars
> with the same dynamics, is my tech. on the right track? The engine
> starts, idles, runs smoothly & powerfully. No fouled plugs and gobs of
> power.
> Any advice from the experts on this list will be very much appreciated.
>
> TIA!!!!

[Quicksilver]

There is nothing special about air that is compressed in a supercharger when compared with air compressed with a turbo charger. Boost is boost. If it had blow-by caused by the load of a supercharger then is would have had blow by if fed by a turbo.

The only real difference is that the supercharged motor will produce slightly less power because you have to subtract the HP that it takes to drive the supercharger. Plus you have to be sure that the crank snout and bearings can take the load.

217hp X 1.7 = 368.9hp. With normal losses from driving the pump and from heating the intake charge I think 345hp is a touch optimistic. That's only 24hp to drive the supercharger, ignoring the losses in the system. I don't believe it. It still would be a serious quantity of power though.

I do question boosting a motor 70% without intercooling and/or a compression reduction. If the 3.2 was that "under compressioned" then everyone would be bumping it up a lot and still running pump gas.

Easy to prove me wrong though. Just supercharge it and then get it to hold together for 80,0000 miles.


Wayne

[Mike Feinstein]

I was thinking the same thing. I wonder how the turbo's get around this problem. Hmmmm.

[dickster]

mike

i'm no expert but i've done quite a bit of reading on the subject.

i would think that the boost is acceptable on the sc because it is intercooled. the stage 1 promo turbo is not intercooled.

as for the blow by passed the rings, i agree with the other poster - that would not be unique to a sc.

if i had the cash i wouldnt hesitate, but would probably go for the promo turbo. if only

[masraum]

Agreed, the blowby should not be unique to a supercharger, but possibly it is due to the kit boosting too high on an otherwise normal compression ratio engine. Since 3 separate people have had the same problem i might think twice or do a lot mero research before getting that particular kit.

Another possible problem with that much blow by on a system that has more fuel than an NA engine is that you would probably end up with more fuel in the oil which isn't a good thing.

[dd74]

So what is, in everyone's estimation, "safe boost" for an SC engine; particularly one with 9.3:1 compression?

Thanks.

[RickM]

Non-intercooled: 7 lbs
Intercooled: 9-11 lbs

These are approximate as each car will have different tuning characteristics.

[Mike Feinstein]

Spoke with SOK today. Light boost charger runs 6-8 lbs. Paul says he's never heard of anyone with a "healthy" engine having problems with a pressurized crankcase. If rings are tired / warn, it could occur. Says system produces 350hp and 342 torque at ~7 lbs.

Installation estimate is 30 hours!!! He advises installing with engine in the car. No cutting, welding, etc....just nuts, bolts, clips, and wires. He says that anyone who adjusts their own valves, could do the install. I asked about the 30 hour estimate and he said there is a lot of "detail" to the install. I can't imagine what could take that kind of time without lowering or opening the engine. Still very intrigued. Might be a winter project.

[Mark McClure]

Wheather it is intercooled or not would not effect the blowby. It is the sheer pressure that would cause this.

Could it be that the S/C creates boost from idle all the way up where as a turbo creates it when it has spooled upto its operating speed. Is there more chance of the pressures having a greater effect on the rings at low engine speeds........less forces on the rings tocreat a good seal?

Cheers

Mark....

I also have been pondering the Turbo/SC upgrade......the SC was winning as it is a much simpler installation.

[jyl]

Installation estimate is 30 hours!!! He advises installing with engine in the car. No cutting, welding, etc....just nuts, bolts, clips, and wires. He says that anyone who adjusts their own valves, could do the install. I asked about the 30 hour estimate and he said there is a lot of "detail" to the install. I can't imagine what could take that kind of time without lowering or opening the engine. Still very intrigued. Might be a winter project. [/B]

The whipple kit uses a different intake manifold, right? If you have to remove the EFI stuff, remove manifold, install S/C, install new manifold, install pulley stuff, re-install EFI, etc etc seems like might be a lot easier with engine out. Did he say anything about the heater?

Intrigued also . . . hoping to learn from your experience.

[Mike Feinstein]

John,

Interestingly, it seems the heater is the toughest part. It is not part of the kit and requires some creative plumbing. The AC is supposedly simple by comparison. A fender mounted condenser and some longer plumbing. If I go for it, I figure I'll get the thing in and running first and worry about heat later. There's got to be a way.