Intake hose question and progress report
12-28-2010, 10:29 AM
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Intake hose question and progress report
Well I finally got an afternoon to work on my new acquisition - Black/black 88 S4 auto. I spent it under the hood removing the worst of 220,000 km and 23 years (it was made in 87) of grime. There's nothing like cleaning everything you can touch to get a feel for what-is-what and what-goes where IMO. I still lots more in-depth cleaning to do, but it already looks way better. The left cam cover was noticeably oily, and sure enough, it looks like the spark plug seal for the front cylinder on that side is shot - the outside of the spark plug, plug adapter and cover were all coated in fresh oil. I'll be ordering a seal set for the cam cover on that side. Doubtless I'll have to do the right side soon - but right now I'm on the 'fix what is already broken' regime. That includes new plugs (worn and way too large gap) and leads/cables (outside casings visibly cracked and looking like they are the originals!). The PO did tell me he had not changed the plugs over the 11 yrs and 100k kms he had the car. He was fanatic about fluids though...
There were leaves and maple keys in every nook. The air cleaner was full of leaves. I'm surprised there is no grill over the intake since I gather this is a common problem. The filter is a dirty K&N. I'll be keeping that for now (I've seen the paper vs. oiled filter threads) but cleaning and re-oiling it.
Thin plastic pieces are shot - both the cowl panel cover and intake/suction hoses (see picture). I was debating fabricating a replacement for the cowl cover since I find $65-74 (plus shipping and Canada customs) for a piece of thin plastic more than I want to pay, but then I found Auto Atlanta have it for $27.
My question is related to the intake hoses that need to be replaced. $44 ea does not seem too exorbitant, but frankly they seem of poor quality. It would be pretty easy to fabricated a silicon and aluminum system for less that would be more effective, if I can figure out the design intent. There is a hole punched in each hose that fits over the TB cover, presumably to supply some air for cooling under the cover. That said, the hole is small and at right angles to the air flow, so could only work if there is a significant pressure difference. Given the placement of the intake in a high pressure zone I assume that is the case, but then I wonder what the purpose of the restriction in the intake hose is downstream of TB cover vent - a change from 3" diameter to 2" diameter is a greater than 50% reduction in cross section. I can't believe this is to increase pressure to the TB vent but I'm not sure what else it could be for. It looks like the 85s and 86s don't have this restriction but earlier and later cars do... Ideas?
There were leaves and maple keys in every nook. The air cleaner was full of leaves. I'm surprised there is no grill over the intake since I gather this is a common problem. The filter is a dirty K&N. I'll be keeping that for now (I've seen the paper vs. oiled filter threads) but cleaning and re-oiling it.
Thin plastic pieces are shot - both the cowl panel cover and intake/suction hoses (see picture). I was debating fabricating a replacement for the cowl cover since I find $65-74 (plus shipping and Canada customs) for a piece of thin plastic more than I want to pay, but then I found Auto Atlanta have it for $27.
My question is related to the intake hoses that need to be replaced. $44 ea does not seem too exorbitant, but frankly they seem of poor quality. It would be pretty easy to fabricated a silicon and aluminum system for less that would be more effective, if I can figure out the design intent. There is a hole punched in each hose that fits over the TB cover, presumably to supply some air for cooling under the cover. That said, the hole is small and at right angles to the air flow, so could only work if there is a significant pressure difference. Given the placement of the intake in a high pressure zone I assume that is the case, but then I wonder what the purpose of the restriction in the intake hose is downstream of TB cover vent - a change from 3" diameter to 2" diameter is a greater than 50% reduction in cross section. I can't believe this is to increase pressure to the TB vent but I'm not sure what else it could be for. It looks like the 85s and 86s don't have this restriction but earlier and later cars do... Ideas?
12-28-2010, 12:17 PM
#2
Martin,
I looked at Atlantic Auto (thanks for the link) and the $27 part number has been superseded by a $80.27 part.
A suggestion ... for fragile parts like this cowl cover, I purchase through the dealer. In that manner, if it is damaged in shipment, it is their problem .. and not mine. Buying from a supplier via the internet can result in additional headaches if the part arrives damaged. Typically, the receiver needs to file a claim with the shipping company (and not the seller). For me, life is just too short.
I believe I only paid $103 for my cowl cover - but that was before Porsche cranked up the prices (again).
Cheers
Glenn
I looked at Atlantic Auto (thanks for the link) and the $27 part number has been superseded by a $80.27 part.
A suggestion ... for fragile parts like this cowl cover, I purchase through the dealer. In that manner, if it is damaged in shipment, it is their problem .. and not mine. Buying from a supplier via the internet can result in additional headaches if the part arrives damaged. Typically, the receiver needs to file a claim with the shipping company (and not the seller). For me, life is just too short.
I believe I only paid $103 for my cowl cover - but that was before Porsche cranked up the prices (again).
Cheers
Glenn
12-28-2010, 12:21 PM
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Lots of ideas. Just do a search on "venturies".
12-28-2010, 02:02 PM
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Jim: I understand the venturi effect - higher flow speed and lower pressure - I'm actually a scientist by training. However, what puzzles me is that the TB cover opening is well upstream of the constriction so would not experience the venturi effect (http://en.wikipedia.org/wiki/Venturi_effect). There is no intake port in the constriction, and following the restriction the pipes slowly expand back to 3" dia. before entering the air cleaner - again with no ports. I notice that on the 928sRus EIS there no such constriction before the new filters in the 32V version and the 16V pics show no TB cover on one side.
12-28-2010, 06:16 PM
#7
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Welcome!
Well I finally got an afternoon to work on my new acquisition - Black/black 88 S4 auto. I spent it under the hood removing the worst of 220,000 km and 23 years (it was made in 87) of grime. There's nothing like cleaning everything you can touch to get a feel for what-is-what and what-goes where IMO. I still lots more in-depth cleaning to do, but it already looks way better. The left cam cover was noticeably oily, and sure enough, it looks like the spark plug seal for the front cylinder on that side is shot - the outside of the spark plug, plug adapter and cover were all coated in fresh oil. I'll be ordering a seal set for the cam cover on that side. Doubtless I'll have to do the right side soon - but right now I'm on the 'fix what is already broken' regime. That includes new plugs (worn and way too large gap) and leads/cables (outside casings visibly cracked and looking like they are the originals!). The PO did tell me he had not changed the plugs over the 11 yrs and 100k kms he had the car. He was fanatic about fluids though...
There were leaves and maple keys in every nook. The air cleaner was full of leaves. I'm surprised there is no grill over the intake since I gather this is a common problem. The filter is a dirty K&N. I'll be keeping that for now (I've seen the paper vs. oiled filter threads) but cleaning and re-oiling it.
Thin plastic pieces are shot - both the cowl panel cover and intake/suction hoses (see picture). I was debating fabricating a replacement for the cowl cover since I find $65-74 (plus shipping and Canada customs) for a piece of thin plastic more than I want to pay, but then I found Auto Atlanta have it for $27.
My question is related to the intake hoses that need to be replaced. $44 ea does not seem too exorbitant, but frankly they seem of poor quality. It would be pretty easy to fabricated a silicon and aluminum system for less that would be more effective, if I can figure out the design intent. There is a hole punched in each hose that fits over the TB cover, presumably to supply some air for cooling under the cover. That said, the hole is small and at right angles to the air flow, so could only work if there is a significant pressure difference. Given the placement of the intake in a high pressure zone I assume that is the case, but then I wonder what the purpose of the restriction in the intake hose is downstream of TB cover vent - a change from 3" diameter to 2" diameter is a greater than 50% reduction in cross section. I can't believe this is to increase pressure to the TB vent but I'm not sure what else it could be for. It looks like the 85s and 86s don't have this restriction but earlier and later cars do... Ideas?
There were leaves and maple keys in every nook. The air cleaner was full of leaves. I'm surprised there is no grill over the intake since I gather this is a common problem. The filter is a dirty K&N. I'll be keeping that for now (I've seen the paper vs. oiled filter threads) but cleaning and re-oiling it.
Thin plastic pieces are shot - both the cowl panel cover and intake/suction hoses (see picture). I was debating fabricating a replacement for the cowl cover since I find $65-74 (plus shipping and Canada customs) for a piece of thin plastic more than I want to pay, but then I found Auto Atlanta have it for $27.
My question is related to the intake hoses that need to be replaced. $44 ea does not seem too exorbitant, but frankly they seem of poor quality. It would be pretty easy to fabricated a silicon and aluminum system for less that would be more effective, if I can figure out the design intent. There is a hole punched in each hose that fits over the TB cover, presumably to supply some air for cooling under the cover. That said, the hole is small and at right angles to the air flow, so could only work if there is a significant pressure difference. Given the placement of the intake in a high pressure zone I assume that is the case, but then I wonder what the purpose of the restriction in the intake hose is downstream of TB cover vent - a change from 3" diameter to 2" diameter is a greater than 50% reduction in cross section. I can't believe this is to increase pressure to the TB vent but I'm not sure what else it could be for. It looks like the 85s and 86s don't have this restriction but earlier and later cars do... Ideas?
I trust you've seen the following?
https://rennlist.com/forums/928-foru...ke-system.html
