Porsche 993 twin turbo

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Re: Porsche 993 twin turbo

Post by ptuomov »

Exhaust photos from a very helpful Rennlister:

Cat-pipe between the turbine outlet and muffler inlet:
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CatPipe.jpeg
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CatPipeInlet.jpeg
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OutletToMuffler.jpeg
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The weird second "cans" in the cat pipes are heater vents, from flow perspective think of them just as straight pipes.


The mufflers:
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StockMuffler.jpg
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MufflerInlet.jpeg
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MufflerOutlet.jpeg
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Re: Porsche 993 twin turbo

Post by ptuomov »

What do you think is adequate size for turboback exhaust piping in a street car? In the 928 turbo project, we decided to not exceed 0.1hp/mm^2 or 65hp/sqin. How about you, what are your rules of thumb for turboback exhausts?
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Re: Porsche 993 twin turbo

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ptuomov wrote: Sun Aug 07, 2022 2:19 am
rp930 wrote: Sat Aug 06, 2022 3:19 pm Keep in mind those cars are worth a lot and they are worth more unmolested. Really a great car as delivered. If you want to modify get a 996 Turbo. Less expensive and easy to get hp.
996 Turbo is a great car, but it's cheap mainly because it's ugly. Horsepower with 996 Turbo is cheap and easy because the engine is water cooled, the head has 4 valves per cylinder, the exhaust pulses are grouped to turbos in three 240-degree separated pulses, and ECU is better than in the older models. But the looks...

The car I bought is high miles car and it's not 100% original. https://www.instagram.com/p/Cg5rn38oO3G ... _copy_link

And it's a sickness, I'm not sure I can stop my self from spending a lot of EUR to make this car slightly less valuable.
I agree on the looks. I see the 993 is a euro car. Have at it. It’s your car. Plenty of people ready to take your money.
Remember the bigger you make intake path the more lag you are likely to build in. HP up- longevity down.
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Re: Porsche 993 twin turbo

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rp930 wrote: Sun Aug 07, 2022 9:59 amI see the 993 is a euro car. Have at it. It’s your car. Plenty of people ready to take your money.

Remember the bigger you make intake path the more lag you are likely to build in. HP up- longevity down.
Sometimes it's a problem to get people to do anything here in Europe, but I think Porsche prices are so high that people can be bothered to accept the money. ;-)

I don't think that it makes sense to do much between the compressor outlet and the turbine inlet. It's well sorted from the factory and hard to improve on.

The only thing there might be switching from the stock 993 Turbo cams to 993 Euro RS cams. Those are still Euro-2 legal in substance and possibly in letter and still run hydraulic lifters that work great at the contemplated rpms:

993 Turbo: Intake 234@0.05"/.454, Exhaust 218@0.05/.430
GT2 EVO: Intake 248@0.05"/.485, Exhaust 232@0.05"/.470
RS Euro: Intake 242@0.05"/.490, Exhaust 228@0.05"/.455

I think that reducing the turboback exhaust back pressure should be a net positive in every way, including reliability, because that allows one to run less exhaust manifold pressure and heats up the air cooled engine less.
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Re: Porsche 993 twin turbo

Post by dannobee »

I just looked these up. The "street" 993 GT2 Evos used K24's, PN 993 123 013 82 and 993 123 014 82. The factory race car GT2 Evos used K24/26 hybrids, pn 993 123 013 84 and 993 123 014 84 (now discontinued). I suppose there could be others, too. I don't see them using a K27 as the technology was outdated by then, and it would require an external wastegate, but I suppose it could have happened. And of course, race teams could put on whatever they wanted.

Porsche Factory Motorsport Division has always been very helpful if you want to get the real skinny on which ones they used.
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Re: Porsche 993 twin turbo

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dannobee wrote: Sun Aug 07, 2022 3:38 pm I just looked these up. The "street" 993 GT2 Evos used K24's, PN 993 123 013 82 and 993 123 014 82. The factory race car GT2 Evos used K24/26 hybrids, pn 993 123 013 84 and 993 123 014 84 (now discontinued). I suppose there could be others, too. I don't see them using a K27 as the technology was outdated by then, and it would require an external wastegate, but I suppose it could have happened. And of course, race teams could put on whatever they wanted. Porsche Factory Motorsport Division has always been very helpful if you want to get the real skinny on which ones they used.
Thank you.

I haven't decided which direction to go with this, but right now I'm leaning towards a "factory stock appearing" car with a little power. I could, for example, "upgrade" the car with parts that externally look like the 450hp "X50" WLS2 XLC+XE7 parts. Internally, they could be improved with today's technology.

Can you see exactly what extra parts were included in the base 993 Turbo (not S, not GT2) that was ordered from the factory with the European WLS2 450hp "XLC" engine enhancement package? I am thinking that it was bigger turbos, revised ECU, and 5bar fuel pressure regulator (maybe?), anything else?

XE7 Additional oil cooler in front -- This I understand
XLC Turbo Powerkit 331 kW -- What exactly is in this?

By the way, this Porsche source does say that they did stick some K27's in some GT2 Evos:
gt2evo_copy1.jpg
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Re: Porsche 993 twin turbo

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http://tech-racingcars.wikidot.com/porsche-993-gt2-evo

Specifications
21 units built

M64/83, boxer 6 (180o), 4 stroke, petrol engine, located rear longitudinally
3600-3800cc
600 HP @ 7000 rpm
900 Nm @ 5000 rpm
forged steel crankshaft with 8 plain main bearings 60mm diameter, 55mm big end journal diameter
titanium connecting rods, 58mm big end bearing diameter
DOHC, 2 valves/cyl - 12 valves total. 49mm inlet valve diameter, 42.5mm hollow exhaust valve diameter cooled by natrium
2 x KKK K27 turbochargers with Bosch Motronic multipoint electronic Fuel Injection. Thielert engine management. 2 x 40,4 mm inlet restrictors
Firing order: 1-6-2-4-3-5
dry sump
6 speed sequential Gemini gearbox
steel monocoque chassis with lightened and reinforced Matter roll cage. 2 door coupe steel bodyshell with aluminium front lid and doors
Front suspension, McPherson strut with lower A-arm, coil spring, telescopic gas shock absorber, anti-roll bar
Rear suspension, upper dual lateral links with lower A-arm, rear-center toe link, coil spring, telescopic gas shock absorber, anti-roll bar
rack and pinion
tracks increased by 7 cm
front wheels 18" x 12" (270/650/R18 Yokohama)
rear wheels 18" x 13" (330/690/R18 Yokohama)
1060 kg
fuel tank 100 lt
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Re: Porsche 993 twin turbo

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ptuomov wrote: Sun Aug 07, 2022 5:13 pm http://tech-racingcars.wikidot.com/porsche-993-gt2-evo

Specifications
21 units built

M64/83, boxer 6 (180o), 4 stroke, petrol engine, located rear longitudinally
3600-3800cc
600 HP @ 7000 rpm
900 Nm @ 5000 rpm
forged steel crankshaft with 8 plain main bearings 60mm diameter, 55mm big end journal diameter
titanium connecting rods, 58mm big end bearing diameter
DOHC, 2 valves/cyl - 12 valves total. 49mm inlet valve diameter, 42.5mm hollow exhaust valve diameter cooled by natrium
2 x KKK K27 turbochargers with Bosch Motronic multipoint electronic Fuel Injection. Thielert engine management. 2 x 40,4 mm inlet restrictors
Firing order: 1-6-2-4-3-5
dry sump
6 speed sequential Gemini gearbox
steel monocoque chassis with lightened and reinforced Matter roll cage. 2 door coupe steel bodyshell with aluminium front lid and doors
Front suspension, McPherson strut with lower A-arm, coil spring, telescopic gas shock absorber, anti-roll bar
Rear suspension, upper dual lateral links with lower A-arm, rear-center toe link, coil spring, telescopic gas shock absorber, anti-roll bar
rack and pinion
tracks increased by 7 cm
front wheels 18" x 12" (270/650/R18 Yokohama)
rear wheels 18" x 13" (330/690/R18 Yokohama)
1060 kg
fuel tank 100 lt
Track only. And VERY expensive.
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Re: Porsche 993 twin turbo

Post by dannobee »

What are the part numbers for these K27's?

I'll be in Monterey in a couple of weeks and there's supposed to be a GT2 Evo there for auction. If I can get close enough, I'll crawl under there and look.
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Re: Porsche 993 twin turbo

Post by ptuomov »

I don’t know about the part numbers, but I would guess the part numbers are likely 930 or 964 K-27 turbos. That’s a pure guess!

Also on the guess department is that the change to even larger turbos may have been motivated by the rules-imposed compressor inlet restrictor. Perhaps the K27s worked better across the power band at that specific restrictor size.
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Re: Porsche 993 twin turbo

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Re: Porsche 993 twin turbo

Post by Fusion Works »

Why would you want to use any of the ancient K series turbo designs? The wheels and wheel aerodynamics are now 30+ years old. Turbo technology has come a long way from there. I can't see any reason to use those turbos when there are much better options. (unless you are trying to "keep it stockish")

What do the OE headers look like? The 930 turbos really benefited from better headers going into the turbo. Are you required to keep some variant of catalyst to keep the emissions standards?
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Re: Porsche 993 twin turbo

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ptuomov wrote: Mon Aug 08, 2022 8:14 am. . . Also on the guess department is that the change to even larger turbos may have been motivated by the rules-imposed compressor inlet restrictor. Perhaps the K27s worked better across the power band at that specific restrictor size.
2 x 40mm restrictors will flow about 800 hp choked. At choked flow the air density at the compressor inlet can easily be half which means the compressor will need double the flow capacity to flow the 800 hp (compared to a compressor with atmospheric inlet). The PR would also need to be doubled.

At 600 hp the restrictors would pull the compressor inlet pressure down to about 0.75 bar so the compressor would need to be 33% bigger than with no restrictor. PR would be 33% higher also.
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Re: Porsche 993 twin turbo

Post by ptuomov »

Fusion Works wrote: Mon Aug 08, 2022 5:04 pm Why would you want to use any of the ancient K series turbo designs? The wheels and wheel aerodynamics are now 30+ years old. Turbo technology has come a long way from there. I can't see any reason to use those turbos when there are much better options. (unless you are trying to "keep it stockish")
Yes, the idea is to keep everything stock appearing. The other thing is that the engine is air cooled and the turbos are cooled by journal bearing air flow. So fluid cooled ball bearing center housings are out, because even if one is using oil in the coolant circuit it’ll look obviously non stock.

Whatever wheels that fit in the stock casting are fair game, however. Based on the compressor maps, though, the ancient KKK’s aren’t leaving that much to the table when they are sized right. Or do you have an idea how to change the whole game here?
Fusion Works wrote: Mon Aug 08, 2022 5:04 pm What do the OE headers look like? The 930 turbos really benefited from better headers going into the turbo. Are you required to keep some variant of catalyst to keep the emissions standards?
The OE headers look good except the primaries are too big for my taste. They are fine for stock cams, though, and durable. All the available aftermarket headers are even larger and have a reputation if cracking in six months.
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Re: Porsche 993 twin turbo

Post by Fusion Works »

Contact Brian @ http://rarelyl8.com/home.html

He can build you some headers that will work properly with your engine with proper primary sizes, made out of 321 stainless. They won't crack.
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