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BoxsterGT's Avatar
 
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Porsche Crest 3.8 RS Air Cooled



I see that the 3.8 Super Cup Water Cooled motor from Porsche Motorsport puts out 440 hp.



What does the earlier air cooled 3.8 version of this motor put out for HP?

Can the air cooled version be fitted with Kats for use on the street?

Does anyone have this air cooled combination in an early 911?

Thanks,

Len

Old 11-03-2008, 08:02 AM
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I saw a 3.8RS aircooled engine in a racer this weekend with BIG HONKING stacks, they were claiming 385 horsies.

I do not know if that is high, low, or expected for these beasts.
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1980 911SC sunroof coupe, silver/black: The Wurster
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Old 11-03-2008, 08:07 AM
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Len,

3.8RS air-cooled motors make anywhere from 300-325HP depending on exhaust systems. These are very streetable, smog-compliant, and very durable if properly done. Cats can be fitted for minimal restriction.

3.8RSR air-cooled motors make anywhere from 350-420HP depending on intake system, cams, compression ratio and exhaust systems. This is a full-out race engine and NOT streetable at all. Further, these are basically 25-100 hour engines. No cats.

We've built & installed quite a few 3.8 RS-spec engines in '69-'89 911's,... Some of these 2200 lb cars make this a potent combination.
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Old 11-03-2008, 08:19 AM
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Quote:
Originally Posted by Steve@Rennsport View Post
3.8RSR air-cooled motors make anywhere from 350-420HP depending on intake system, cams, compression ratio and exhaust systems. This is a full-out race engine and NOT streetable at all. Further, these are basically 25-100 hour engines. No cats.
What I saw might have been an RSR, they had "3.8RS" on the carbon fiber wing. It was a full glass bodied, non-street race car.
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1980 911SC sunroof coupe, silver/black: The Wurster
2006 Mazda3 5 door, M-speed exhaust: The Ricer
Putting the sick back into sycophant!
Old 11-03-2008, 08:22 AM
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Quote:
Originally Posted by Pazuzu View Post
What I saw might have been an RSR, they had "3.8RS" on the carbon fiber wing. It was a full glass bodied, non-street race car.
LOL,..All of those RS wings have that logo on there,...

The giveaway is found by looking at the engine since the intake systems are totally different between the RS and RSR version of each engine.
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Old 11-03-2008, 08:32 AM
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Len, here is my version of a 3.8 RSR motor. It's got the full RSR treatment of heads, cylinders, etc. but is detuned slightly (cams) for the street and as Steve W. says it really isn't streetable. I dread coming to lights or stop & go traffic & avoid it like the plague. The motor stalls at the drop of a hat unless the revs are high but then everybody looks at you like you're crazy and it is LOUD. I wanted heat so the flipped-flange bischoff HE's were used, mated to a custom M&K. Because of not using race headers, etc. there is a flat spot at 3500 but above 4K it pulls like crazy & I'm told it is one of the nicest sounding exhausts they've heard due to the combo of PMO's, custom cam, HE's, M&K, etc. On the dyno it was 357 at the wheels (~ 420 at the crank) with about 270 ft lbs. I gave up a bit of torque to have the heat and may scrap the HE's at a later date. I am running 12.5 CR which requires Sunoco purple (110 leaded). It has a redline of 8K but was told if I shifted at 7K the motor would last much, much longer. All in all, it's a boatload of fun in a 2500 lb car! Can't wait to get it on the track.







Old 11-03-2008, 03:47 PM
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Old 11-03-2008, 08:44 PM
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Whole project was documented here (ran concurrent with the masterwork by Matteo):

My '74 RS IROC project

I'll go one better...you can hear it here when I picked up the car. The video quality is a little low but not the soundtrack. The car leaves in the beginning & comes back at the end (sounds like a big block chevy) but a little before the halfway point, my friends are waiting for the car to take off onto the main road in the distance through the woods. The test driver rips through 1st & 2nd...turn up the sound, it'll make the hair on the back of your neck stand up. Enjoy: http://video.google.com/videoplay?docid=2875195681434852402
Old 11-04-2008, 05:43 AM
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Porsche Crest



This is wonderful.
Great exhaust sytem too!
Any photos of the exh system as installed?

Len

Old 11-04-2008, 06:20 AM
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Just this one, if you need more photos of the welds, inlets, etc. I'll have to snap them.

Old 11-04-2008, 06:27 AM
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Stock '95 M64/20 993RS was rated at 300hp@6500, 355Nm@5400(262lb ft)

That was w/ mild hyd cams, Motronic, MAF intake, cats and mufflers. They usually can be tuned to the loww 300s w/ chip and exhaust.

To get power they need cams and revs, to do that lighter/stronger valve train and lighter/stronger recipricating components and a change of engine management to Motronic(or similar) w/ those tools you can have a reliable and streetable high 300 hp engine.

A great example is Geoffrey Rings 3.8RSR a winning powerplant that after 100 hrs of track use it is still getting an honest 340hp to the rear wheels and is still a very streetable power plant, I briefly considered buying it for that purpose.
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Old 11-04-2008, 07:37 AM
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Nice clean exhaust work by Ben.. as usual! :-)
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Old 11-04-2008, 07:46 AM
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Onboost, I think this time around the muffler was delivered without any inlets/outlets welded on so that they could be fitted by Auto Assoc. I agree though that Ben's mufflers are works of art, I had an earlier R muffler for a 70 that was beautiful.

In this instance, the shop put larger outlets than were supplied by Ben. They also flowbenched the muffler to help determine cam specs & jetting.
Old 11-04-2008, 07:58 AM
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As Steve said, the best you're going to get for a streetable 3.8 motor is 300-325 HP. A completely stock European 993 3.8 motor dynos 300 hp on a Superflow engine dyno. The GT3 watercooled motors have lots of modern technology going for it allowing it to rev out to 8400 and make peak HP at 7800, the key to breaking the 420 barrier on 91 octane, get 24 mpg, and be completely streetable. Primary technologies are 4 valve/cylinder heads with central located spark plugs, 12:1 CR, titanium connecting rods, VarioCam, dual stage intakes, ram air induction, a vacuum setup that draws air out of the crankcase to minimize windage losses at high rpms (+8 hp), and on the street cars, a switchable exhaust that bypasses all mufflers and becomes open exhaust out of the headers/cats after 4000 rpm, all while still meeting US LEV II (Low Emission Vehicle) standards.

Below you can see rear wheel HP numbers for them on a Dynojet. Divide by 0.85 to get the engine hp values. The red curve is a race built 3.8 964 with headers and open exhaust on race fuel outputting 291 rwhp at 6100 (or 342 at the engine. The blue curve is a stock 997 3.6 GT3 street car, and green curve is a 997 3.6 GT3 Cupcar that around 7800 is approaching 370 rwhp and continuing to rise. The Cupcar produces less low and midrange hp because it lacks the variable cams of the regular GT3 motor. If you assume a Dynojet is accurate, this shows the 3.6 GT3 motors make/exceed 435 hp at the engine. For a 3.8, add about 5% to that and it gives you the proportional increase in power for the RSR motors.

Old 11-04-2008, 09:26 AM
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Quote:
Originally Posted by mpeastend View Post
Len, here is my version of a 3.8 RSR motor. It's got the full RSR treatment of heads, cylinders, etc. but is detuned slightly (cams) for the street and as Steve W. says it really isn't streetable. I dread coming to lights or stop & go traffic & avoid it like the plague. The motor stalls at the drop of a hat unless the revs are high but then everybody looks at you like you're crazy and it is LOUD. I wanted heat so the flipped-flange bischoff HE's were used, mated to a custom M&K. Because of not using race headers, etc. there is a flat spot at 3500 but above 4K it pulls like crazy & I'm told it is one of the nicest sounding exhausts they've heard due to the combo of PMO's, custom cam, HE's, M&K, etc. On the dyno it was 357 at the wheels (~ 420 at the crank) with about 270 ft lbs. I gave up a bit of torque to have the heat and may scrap the HE's at a later date. I am running 12.5 CR which requires Sunoco purple (110 leaded). It has a redline of 8K but was told if I shifted at 7K the motor would last much, much longer. All in all, it's a boatload of fun in a 2500 lb car! Can't wait to get it on the track.







wow!!!!
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Old 11-04-2008, 09:33 AM
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