Turbo's aren't interference design???
12-01-2004, 11:38 PM
#1
Burning Brakes
Thread Starter
Turbo's aren't interference design???
I was just reading a Pelican Tech article on timing belts and it said that because of the low compression the turbo is not an interference design?
Really, I have never heard that in over a year on the board. If it is so, I think that makes the turbo all that more attractive. The article went on to say that it didn't mean you would ignore the timing belt. Is this true?
Really, I have never heard that in over a year on the board. If it is so, I think that makes the turbo all that more attractive. The article went on to say that it didn't mean you would ignore the timing belt. Is this true?
12-01-2004, 11:47 PM
#2
Cast Iron Man
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I've read in numerous places that they are all interference motors (NA, 951, S, S2 it doesn't matter). Are you sure they weren't talking about a 924T?
12-01-2004, 11:58 PM
#5
They are dead wrong, it is most certainly an interference design.
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12-01-2004, 11:59 PM
#8
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the only Porsche in the series that I know of that isn't an interference design is the 924 NA...IIRC the 924 Turbo (a.k.a. 931 [just showing off my porsche knowledge 
]) is an interference, as is the 924S, 944, 951, 944S, 944S2, and 968
]) is an interference, as is the 924S, 944, 951, 944S, 944S2, and 968
12-02-2004, 12:07 AM
#10
Burning Brakes
Thread Starter
found it again: from Pelican tech articles: Affordable Porsches:
see near bottom about turbo's
The 944 has several major pluses, from its modern design to its galvanized bodywork, but there are a few problem areas that need to be addressed. For one, these engines feature an interference design, so a broken timing belt can be an expensive problem as the valves meet the pistons. Figure a grand or two to fix that mess. Old oil and coolant seals can be a cause of belt problems, as these liquids attack rubber engine components. Worn engine mounts are also common, and Randy reports seeing lots of water pump problems. "Water pumps can be a pretty weak spot on that car," he reports. The hot fix there is to upgrade to the 944 Turbo water pump. Sunroof assemblies can also be a problem. "The cable system gets goofy," Randy says, and replacement parts can be hard to find. Unfortunately, buying a new sunroof assembly may be the only fix. He has also seen rear windows leak, more on cars from hot climates.
The cars feature good electronics, although problems can come up. Electrolyte and acid leaks from the battery can attack the alarm controls, while a bad DME relay can immobilize any car. The DME relay controls the engine’s spark and fuel delivery, so our experts recommend carrying a replacement. Engine rebuilds for the 944 are not as pricey as those for the 911, but could still cost a few thousand dollars. As an alternative, Randy says a 968 conversion would be cool, as the later engine features 3.0 liters of displacement, Variocam variable valve timing and a clutch setup that allows easier changes. (The 944 features a rear-mounted transaxle, and clutch changes can be a bear.)
Everything that goes for the 944 pertains to the 944 Turbo models, as more power can only be a good thing. "A good running 944 turbo is a joy," Randy says, even though there is some turbo lag. "It’s pretty much on or off." On the plus side, the 944 Turbo’s lower compression ratio means the engine doesn’t have an interference design. We’re not saying it’s okay to neglect the timing belt, but you’re not totally screwed should it breaks. On the downside, the 944 Turbos still command more money. For $10,000, Randy figures there are two choices: Buy the the world’s nicest "regular" 944, or pick up a 944 Turbo that probably needs some attention. What about the original 924? Wayne says he would shy away from one of them, as the parts are still expensive, the cars don’t have a great performance image, and other Porsches tend to have a larger enthusiast following. Add up those factors, and you have a lot of ratty, unloved cars flooding the marketplace.
see near bottom about turbo's
The 944 has several major pluses, from its modern design to its galvanized bodywork, but there are a few problem areas that need to be addressed. For one, these engines feature an interference design, so a broken timing belt can be an expensive problem as the valves meet the pistons. Figure a grand or two to fix that mess. Old oil and coolant seals can be a cause of belt problems, as these liquids attack rubber engine components. Worn engine mounts are also common, and Randy reports seeing lots of water pump problems. "Water pumps can be a pretty weak spot on that car," he reports. The hot fix there is to upgrade to the 944 Turbo water pump. Sunroof assemblies can also be a problem. "The cable system gets goofy," Randy says, and replacement parts can be hard to find. Unfortunately, buying a new sunroof assembly may be the only fix. He has also seen rear windows leak, more on cars from hot climates.
The cars feature good electronics, although problems can come up. Electrolyte and acid leaks from the battery can attack the alarm controls, while a bad DME relay can immobilize any car. The DME relay controls the engine’s spark and fuel delivery, so our experts recommend carrying a replacement. Engine rebuilds for the 944 are not as pricey as those for the 911, but could still cost a few thousand dollars. As an alternative, Randy says a 968 conversion would be cool, as the later engine features 3.0 liters of displacement, Variocam variable valve timing and a clutch setup that allows easier changes. (The 944 features a rear-mounted transaxle, and clutch changes can be a bear.)
Everything that goes for the 944 pertains to the 944 Turbo models, as more power can only be a good thing. "A good running 944 turbo is a joy," Randy says, even though there is some turbo lag. "It’s pretty much on or off." On the plus side, the 944 Turbo’s lower compression ratio means the engine doesn’t have an interference design. We’re not saying it’s okay to neglect the timing belt, but you’re not totally screwed should it breaks. On the downside, the 944 Turbos still command more money. For $10,000, Randy figures there are two choices: Buy the the world’s nicest "regular" 944, or pick up a 944 Turbo that probably needs some attention. What about the original 924? Wayne says he would shy away from one of them, as the parts are still expensive, the cars don’t have a great performance image, and other Porsches tend to have a larger enthusiast following. Add up those factors, and you have a lot of ratty, unloved cars flooding the marketplace.
12-02-2004, 12:09 AM
#11
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I don't buy it. that article is a load of crap. Ask some turbo owners here who have snapped their timing belts if it's an interference engine or not...
12-02-2004, 12:15 AM
#12
Race Director
Someone at Pelican must've have been on heavy-duty crack when they wrote that article. Here's some 951 pistons after proving the non-interference theory wrong:
I'll get around to taking picture of 6 bent valves too...
I'll get around to taking picture of 6 bent valves too...
12-02-2004, 12:22 AM
#13
Spell Checker
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I think they are using the interference term a little too tightly here. I am not sure there is even a grade of "interferenceness". It is obviously possible. I guess with the lower compression pistons on the NA 2.5L it is somewhat more possible to have a problem. Whatever. They are flat wrong.
