venturi does not speed up air!!!
#32
Rennlist Member
I agree with everything dr bob said except for one correction. The stub for the belt cooling is located several inches forwards of the throat of the venturi. The tube still draws air through the stub to cool the belt though. The way that dr bob described it would have been even more efficient at drawing air through the belt area.
#33
Rennlist Member
xgfhsth, you are a spambot-- that is an echo of what Mike Schmidt said 12 years ago. Go away.
Jerry, the missing page from the Porsche '81 service info (post #25) says that "air is drawn from housing (2) through opening (1) for cooling of the toothed belt (3)". That's how you know
Jerry, the missing page from the Porsche '81 service info (post #25) says that "air is drawn from housing (2) through opening (1) for cooling of the toothed belt (3)". That's how you know
#34
Rennlist Member
xgfhsth, you are a spambot-- that is an echo of what Mike Schmidt said 12 years ago. Go away.
Jerry, the missing page from the Porsche '81 service info (post #25) says that "air is drawn from housing (2) through opening (1) for cooling of the toothed belt (3)". That's how you know
Jerry, the missing page from the Porsche '81 service info (post #25) says that "air is drawn from housing (2) through opening (1) for cooling of the toothed belt (3)". That's how you know
On the other hand, I do think that air enters the belt "housing" from somewhere besides the stub openings and gets pumped up into higher pressure probably around its outer areas and then is blown into the intake tubes through the stub openings. I don't know that because I don't have any other knowledge about the pressure differentials in respect to the three or four areas that might be involved.
#35
Team Owner
Jerry the air that passes through the the timing cover starts at the bottom center of the timing cover note the little opening next to the crank damper,
the air is drawn upwards, and is assisted by the heat of the engine as it rises inside the housing towards the top of each cover,
also assisted by the lower pressure air as its moved through the intake tubes.
This system was also made to capture any combustion fumes that might escape the seals at the front of the engine.
NOTE air movement process can be confirmed by observing the small pieces of rubber that accumulate in the air filter .
Take a fresh timing belt job and a fresh air filter run for a few hundred miles,
then tap the air filter onto a white piece of paper,
the particulates will contain rubber shards from the belt as it wears into the belt run.
the air is drawn upwards, and is assisted by the heat of the engine as it rises inside the housing towards the top of each cover,
also assisted by the lower pressure air as its moved through the intake tubes.
This system was also made to capture any combustion fumes that might escape the seals at the front of the engine.
NOTE air movement process can be confirmed by observing the small pieces of rubber that accumulate in the air filter .
Take a fresh timing belt job and a fresh air filter run for a few hundred miles,
then tap the air filter onto a white piece of paper,
the particulates will contain rubber shards from the belt as it wears into the belt run.
#37
Nordschleife Master
It's always puzzled me that they would duct hot air into the tubes designed to bring cool air into the engine.
I use 3" brake duct with no connection to the belt covers. No venturi. No sound deadening. Worth a pony or three, I figure. Setting the way-back machine... I once ran a dyno test with an open air filter and lost 5 hp! The cool air works.
And... Curse you, Steve, for trolling us all!
I use 3" brake duct with no connection to the belt covers. No venturi. No sound deadening. Worth a pony or three, I figure. Setting the way-back machine... I once ran a dyno test with an open air filter and lost 5 hp! The cool air works.
And... Curse you, Steve, for trolling us all!
#38
Rennlist Member
Jerry the air that passes through the the timing cover starts at the bottom center of the timing cover note the little opening next to the crank damper,
the air is drawn upwards, and is assisted by the heat of the engine as it rises inside the housing towards the top of each cover,
also assisted by the lower pressure air as its moved through the intake tubes.
This system was also made to capture any combustion fumes that might escape the seals at the front of the engine.
NOTE air movement process can be confirmed by observing the small pieces of rubber that accumulate in the air filter .
Take a fresh timing belt job and a fresh air filter run for a few hundred miles,
then tap the air filter onto a white piece of paper,
the particulates will contain rubber shards from the belt as it wears into the belt run.
the air is drawn upwards, and is assisted by the heat of the engine as it rises inside the housing towards the top of each cover,
also assisted by the lower pressure air as its moved through the intake tubes.
This system was also made to capture any combustion fumes that might escape the seals at the front of the engine.
NOTE air movement process can be confirmed by observing the small pieces of rubber that accumulate in the air filter .
Take a fresh timing belt job and a fresh air filter run for a few hundred miles,
then tap the air filter onto a white piece of paper,
the particulates will contain rubber shards from the belt as it wears into the belt run.
It's always puzzled me that they would duct hot air into the tubes designed to bring cool air into the engine.
I use 3" brake duct with no connection to the belt covers. No venturi. No sound deadening. Worth a pony or three, I figure. Setting the way-back machine... I once ran a dyno test with an open air filter and lost 5 hp! The cool air works.
And... Curse you, Steve, for trolling us all!
I use 3" brake duct with no connection to the belt covers. No venturi. No sound deadening. Worth a pony or three, I figure. Setting the way-back machine... I once ran a dyno test with an open air filter and lost 5 hp! The cool air works.
And... Curse you, Steve, for trolling us all!
while there is still a venture with the stock tubes, which is mainly for sound, the fact is, the air speeds up and then slows down again, at a cost of mass flow, if you didn't have the venture. its a pressure drop, plain and simple. getting rid of the tubes, smoothing them out, is a good thing for subtle power gains. most of the air filter and intake tube comparisons are so in accurate, due to the loose fitting tubes and leaky airboxs on most systems.
Im still very anxious to do the air filter test. I was there at the dyno and couldn't find the stock air filter to test at the dyno vs the KN. next time, ill get a good paper filter and do the test.
#40
You can call me Otis
Rennlist Member
Rennlist Member
Join Date: Feb 2013
Location: Terre Haute, Indiana
Posts: 6,662
Likes: 0
Received 10 Likes
on
10 Posts
It's always puzzled me that they would duct hot air into the tubes designed to bring cool air into the engine.
I use 3" brake duct with no connection to the belt covers. No venturi. No sound deadening. Worth a pony or three, I figure. Setting the way-back machine... I once ran a dyno test with an open air filter and lost 5 hp! The cool air works.
And... Curse you, Steve, for trolling us all!
I use 3" brake duct with no connection to the belt covers. No venturi. No sound deadening. Worth a pony or three, I figure. Setting the way-back machine... I once ran a dyno test with an open air filter and lost 5 hp! The cool air works.
And... Curse you, Steve, for trolling us all!
#42
Rennlist Member
Holy airpressure, Batman. I often wondered about which way the air was moving in the covers, but I do know the opening at the top is essentially a venturi, a la Bernouli (and his principle). And Stan just cleared up the question about how air is allowed in. Otherwise Bernouli would be diminished. And I would have not understood the rest of it if you guys hadn't explained it all for me.
#44
Electron Wrangler
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Alan
#45
Rennlist Member
I get (measured with sensitive sensor) .18psi at 120mph..... in the tubes................ thats the max you can harness from the oncoming air. hardly enough to blow anything apart or off.