 1.8L VS 2.0L T4 exhaust systems |
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| technicalninja |
 Dec 22 2024, 12:51 AM
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#1
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Advanced Member  Group: Members Posts: 2,091 Joined: 31-January 23 From: Granbury Texas Member No.: 27,135 Region Association: Southwest Region 
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I've wondered why Porsche built different exhaust systems for the T4.
It appears that any year complete exhaust system can be installed on any year T4. And yet the systems are so different that even the mount at the transmission needs to match the exhaust. Why? It seems the systems have the same size pipes. The 1.8/1.7 have a short "S" kick up at the back that doesn't look like it will affect flow very much. What am I missing? Are the 2.0L mufflers higher flow? Was it just a sound difference? I didn't "see" an obvious flow difference when I bought a pair of used 1.8L SSI exchangers and the Bursh muffler that fit them. Was I wrong? |
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| Jack Standz |
Dec 22 2024, 05:48 AM
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#2
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Member Group: Members Posts: 418 Joined: 15-November 19 From: Happy Place (& surrounding area) Member No.: 23,644 Region Association: None
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The 2 liter exhaust system heat exchangers have a very slightly larger inside diameter. This probably allows for greater flow, especially on modified motors. Not sure if it makes a meaningful difference to stock 914s.
Other than that, trying to get into the minds of what Porsche engineers were thinking 55 years ago is a difficult task. Why all the complicated stuff on 914s and other Porsches? Why do we have to buy all these special tools? Why did they run the full power of the starting system through the ignition switch? (clearly they knew about relays) And why did they not provide a safer better way to jack up the car so you can work on it? |
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| Geezer914 |
Dec 22 2024, 08:30 AM
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#3
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Geezer914 Group: Members Posts: 1,791 Joined: 18-March 09 From: Salem, NJ Member No.: 10,179 Region Association: North East States
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I believe the aftermarket SS exhaust use the the same diameter pipes. The intake runners on the FI 2.0 are slightly larger than the 1.7 and 1.8L.
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| Jack Standz |
Dec 22 2024, 11:58 AM
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#4
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Member Group: Members Posts: 418 Joined: 15-November 19 From: Happy Place (& surrounding area) Member No.: 23,644 Region Association: None
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Am out of town and won't be back for a couple weeks, so can't measure things right now. But, someone has probably posted the dimensions here somewhere. At least have OEM 1.7 and 2.0 as well as 1.7/1.8 SSI aftermarket ones (which I think are the same size as the 2.0 SSIs).
Not sure, but one of the changes to the heat exchangers, exhaust hanger, and muffler may have something to do with the end of the 901 tailshifter in 1972 and the 2 liters production after then? |
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| bdstone914 |
Dec 22 2024, 12:40 PM
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#5
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bdstone914 Group: Members Posts: 4,732 Joined: 8-November 03 From: Riverside CA Member No.: 1,319 |
1974 1.8 stock heat exchangers have the same tube size as 2.0.
@mb911 might have flow info on stock mufflers |
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| 914sgofast2 |
Dec 22 2024, 12:45 PM
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#6
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Senior Member Group: Members Posts: 654 Joined: 10-May 13 From: El Dorado Hills, CA Member No.: 15,855 Region Association: None |
Aren't the exhaust outlet ports on the heads all the same, regardless of engine displacement? They all use the same infernal copper exhaust washer between the pipe and the port on the head.
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