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And yes we stock the best baffle by far - GB is the way to go. His custom designed, proven and tested baffle works and is a work of art.
__________________
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
I'm having fun reading books and learning about these things.
Good luck to you, too.
I obviously read and study to avoid "re-creating the wheel".
Raw scientific theory is tough to find and usually tough to apply. I use it for rough guidelines....saves time...sometimes.
I'm very untrusting of books and articles where someone takes theory and perverts it into fact....very dangerous. Authors generally are looking for "filler" material to "plump up" their text and will start writing absolute bullsh^t, trying to pass it off as knowledge or fact.
For instance, I've just finished another (yes, done this several times before) couple of days trying to figure out offset piston pins. It's very difficult for me to understand why Porsche, in the majority of the 928 engines and virtually all of the 911 engines, installs half of the pistons with the offset in one direction and them, on the other side of the engine, installs the offset in the other direction. Makes no sense, no matter how many times I try to figure it out.
In these "offset pin with non symetrical identical piston" engines, half of the connecting rods go "over center" before TDC and half don't go over center until after TDC. The half that go over center ATDC (5-8 side) slap the pistons pretty hard against the cylinder walls...which as clearance between the piston and cylinder grows, fools the knock sensors into thinking there is a knock event starting to occur.
I've searched and searched....read and read....pages and pages of theory perverted into fact....without any clue why a major engineering firm, like Porsche, would do something like this.
There's certainly volumes of "filler" written about piston offset...going back many years. Fact and scientific data are tough to find!
Thanks for the responses. While most of the technical details are well over my head I appreciate the level of knowledge none the less. Perhaps I don't understand, so please correct me if I'm wrong, but if I go with the GB solution I'll install his baffle, then on top of that the stock metal louvered baffle, then the filler neck?
Reading dead people's minds is always difficult. We have one person here on the internet who's an expert on that, but he doesn't come to RL anymore.
I can however answer why I would use just one piston part number in a V8 engine.
The marketing department gives me a noise-vibration-harshness spec. That spec makes it so that I can't use centered piston pins as those slap the whole piston side to the wall at the same time and make the engine a bit louder and harsh sounding when cold. So I have to offset the pin.
The noise reduction is achieved no matter which direction I offset the pin. This is because the noise in a centered pin piston comes from the top and the bottom of the piston transferring sides simultaneously. Offsetting the pin on either side will cause the top and bottom of the skirt transfer at different times, and I can spec the piston skirt "cam" to be a little barrel faced so it'll transfer around TDC very smoothly and quietly.
The accounting department is going to dock me $$$ for each part number and $$$$$ for each casting. So even if the casting is symmetric, I don't want to have any different machining (say valve reliefs) or markings in the left side and right side pistons, because that would force me to pay for another part number from my budget.
The solution is obvious, I just use the same piston on both banks, spend money only on one part number, install the pistons with different wristpin offset (relative to crank rotation) in the two banks, and don't care about the minor differences between rod angles between banks. (If the piston crown is symmetric, I'll flip half the pistons for my own car in the privacy of my own garage.)
Originally Posted by GregBBRD
I obviously read and study to avoid "re-creating the wheel".
Raw scientific theory is tough to find and usually tough to apply. I use it for rough guidelines....saves time...sometimes.
I'm very untrusting of books and articles where someone takes theory and perverts it into fact....very dangerous. Authors generally are looking for "filler" material to "plump up" their text and will start writing absolute bullsh^t, trying to pass it off as knowledge or fact.
For instance, I've just finished another (yes, done this several times before) couple of days trying to figure out offset piston pins. It's very difficult for me to understand why Porsche, in the majority of the 928 engines and virtually all of the 911 engines, installs half of the pistons with the offset in one direction and them, on the other side of the engine, installs the offset in the other direction. Makes no sense, no matter how many times I try to figure it out.
In these "offset pin with non symetrical identical piston" engines, half of the connecting rods go "over center" before TDC and half don't go over center until after TDC. The half that go over center ATDC (5-8 side) slap the pistons pretty hard against the cylinder walls...which as clearance between the piston and cylinder grows, fools the knock sensors into thinking there is a knock event starting to occur.
I've searched and searched....read and read....pages and pages of theory perverted into fact....without any clue why a major engineering firm, like Porsche, would do something like this.
There's certainly volumes of "filler" written about piston offset...going back many years. Fact and scientific data are tough to find!
Reading dead people's minds is always difficult. We have one person here on the internet who's an expert on that, but he doesn't come to RL anymore.
I can however answer why I would use just one piston part number in a V8 engine.
The marketing department gives me a noise-vibration-harshness spec. That spec makes it so that I can't use centered piston pins as those slap the whole piston side to the wall at the same time and make the engine a bit louder and harsh sounding when cold. So I have to offset the pin.
The noise reduction is achieved no matter which direction I offset the pin. This is because the noise in a centered pin piston comes from the top and the bottom of the piston transferring sides simultaneously. Offsetting the pin on either side will cause the top and bottom of the skirt transfer at different times, and I can spec the piston skirt "cam" to be a little barrel faced so it'll transfer around TDC very smoothly and quietly.
The accounting department is going to dock me $$$ for each part number and $$$$$ for each casting. So even if the casting is symmetric, I don't want to have any different machining (say valve reliefs) or markings in the left side and right side pistons, because that would force me to pay for another part number from my budget.
The solution is obvious, I just use the same piston on both banks, spend money only on one part number, install the pistons with different wristpin offset (relative to crank rotation) in the two banks, and don't care about the minor differences between rod angles between banks. (If the piston crown is symmetric, I'll flip half the pistons for my own car in the privacy of my own garage.)
I wish it was that simple....I'm quite surprised that someone who critically thinks about virtually everything would accept that reasoning.
Pistons flipped over to the "wrong side" are supposed to make more power because of the reduced rod angle on the power stroke and decreased friction on the power stroke (I've never seen any dyno results from this theory), but they "slap" much more than pistons with "centered" wrist pins.....that is a known thing.
The result is an engine with pistons that are as quiet as one can make them on one side and as noisy as possible on the other side.
Interestingly enough, in the "high output small engine world".....motorcycles and rumored in Formula One....engine designers have taken this "offset" to new levels. They have moved the actual bores of the engine over to create even more "piston offset" (the bores are not centered over the crankshaft.) This reduces the rod angle on the power stroke to the point where the "loads" on the pistons and rods are so reduced that they can significantly reduce the weight of the rod and the piston....resulting in increased RPM potential.
When Chevy paid a lot of attention to whatever Smokey Yunick said (Smokey insisted that one should stuff in as long a connecting rod as possible and offset the pistons to further reduce the rod angle), Chevy actually made offset pistons with part numbers for each side of the engine, so that they could run the offset in the "increased noise/higher power" direction. This only lasted for a short period of time and Chevy went back to making engine with centered wrist pins.
Regarding our 928 engines: Only in the 1987-1995 S4, GT, and GTS engines did Porsche realize that the pistons would be noisy on one side of the engine and make the valve reliefs symmetrical, with an arrow points to the front of the engine....so that the pistons would be installed with the offsets all be towards the "quiet direction". I assume that they were forced to do this, because they added knock sensors at this same point in time.
911 engines continued to be "confused"....with pistons "upside down" on one side of the engine. Porsche even did this with 911 "full race" engines....for many, many years....which made absolutely no sense. Only now, do the very recent water cooled race engines have two different pistons....to take advantage of the reduced rod angle and reduced friction on the power stroke....on both sides of the engine.
I wish it was that simple....I'm quite surprised that someone who critically thinks about virtually everything would accept that reasoning.
Pistons flipped over to the "wrong side" are supposed to make more power because of the reduced rod angle on the power stroke and decreased friction on the power stroke (I've never seen any dyno results from this theory), but they "slap" much more than pistons with "centered" wrist pins.....that is a known thing.
The result is an engine with pistons that are as quiet as one can make them on one side and as noisy as possible on the other side.
Interestingly enough, in the "high output small engine world".....motorcycles and rumored in Formula One....engine designers have taken this "offset" to new levels. They have moved the actual bores of the engine over to create even more "piston offset" (the bores are not centered over the crankshaft.) This reduces the rod angle on the power stroke to the point where the "loads" on the pistons and rods are so reduced that they can significantly reduce the weight of the rod and the piston....resulting in increased RPM potential.
When Chevy paid a lot of attention to whatever Smokey Yunick said (Smokey insisted that one should stuff in as long a connecting rod as possible and offset the pistons to further reduce the rod angle), Chevy actually made offset pistons with part numbers for each side of the engine, so that they could run the offset in the "increased noise/higher power" direction. This only lasted for a short period of time and Chevy went back to making engine with centered wrist pins.
Regarding our 928 engines: Only in the 1987-1995 S4, GT, and GTS engines did Porsche realize that the pistons would be noisy on one side of the engine and make the valve reliefs symmetrical, with an arrow points to the front of the engine....so that the pistons would be installed with the offsets all be towards the "quiet direction". I assume that they were forced to do this, because they added knock sensors at this same point in time.
911 engines continued to be "confused"....with pistons "upside down" on one side of the engine. Porsche even did this with 911 "full race" engines....for many, many years....which made absolutely no sense. Only now, do the very recent water cooled race engines have two different pistons....to take advantage of the reduced rod angle and reduced friction on the power stroke....on both sides of the engine.
I get the rod angle logic and how piston pin offset relates to that. If the cylinder pressure varies (as it does) over the strokes, one can get a better rod angle for the power stroke that has the high pressure.
BMW has offset crankshafts in production cars, I want to say 328i for example.
I don't understand why piston pin offset in either direction would be noisier than centered piston pin in terms of the piston slap. My logic says it should roll no matter which way it's offset. I've read people claiming that this is the case, but that's not the same as understanding it. But then again, there are great many things that I don't understand.
I get the rod angle logic and how piston pin offset relates to that. If the cylinder pressure varies (as it does) over the strokes, one can get a better rod angle for the power stroke that has the high pressure.
BMW has offset crankshafts in production cars, I want to say 328i for example.
I don't understand why piston pin offset in either direction would be noisier than centered piston pin in terms of the piston slap. My logic says it should roll no matter which way it's offset. I've read people claiming that this is the case, but that's not the same as understanding it. But then again, there are great many things that I don't understand.
I know which direction I install pistons with offset pins for street engines.
I know which way I install them for a track engine.
I know how I order all my custom pistons.
That's about the total depth of my knowledge about this subject....and I've seen studying it on and off for years.
I've just been hoping that I could find someone who really knew....the Internet seems to be filled with people that simply repeat what they have heard....which is what my original point was.
Thanks for the responses. While most of the technical details are well over my head I appreciate the level of knowledge none the less. Perhaps I don't understand, so please correct me if I'm wrong, but if I go with the GB solution I'll install his baffle, then on top of that the stock metal louvered baffle, then the filler neck?
That is fine - when I changed to a metal oil neck I separated the plastic baffle from the plastic filler neck, trimmed it down to fit the bottom of the metal filler neck and riveted it in place.
This is a great thread to resurrect to ask a couple questions as I put my engine back together.
A. Oil filler neck baffle installation order. Please correct, add/remove as necessary
1. Drei-bond on block
2. Gasket
3. Drei-bond on gasket
4. GB baffle
5. Drei-bond on baffle
6. Oil filler neck with stock baffle.
B. For a boosted engine, it was suggested to block off both ports on my oil filler neck, as well as the port on the MAF boot. Is it ok to run a hose from one port to the other on the oil filler neck, with hose clamps? On an 89 engine, is it suggested to then tie the 2 cam cover breather hoses on the LS together and vent to a catch can/separator or what?
This is a great thread to resurrect to ask a couple questions as I put my engine back together.
A. Oil filler neck baffle installation order. Please correct, add/remove as necessary
1. Drei-bond on block
2. Gasket
3. Drei-bond on gasket
4. GB baffle
5. Drei-bond on baffle
6. Oil filler neck with stock baffle.
B. For a boosted engine, it was suggested to block off both ports on my oil filler neck, as well as the port on the MAF boot. Is it ok to run a hose from one port to the other on the oil filler neck, with hose clamps? On an 89 engine, is it suggested to then tie the 2 cam cover breather hoses on the LS together and vent to a catch can/separator or what?
The block is rarely/never warped at the filler neck....and if it is, there is more wrong than just that!
Here's what I do:
1.Thin layer of Drei Bond between block and my baffle.
2. Plastic Filler Neck: Check for flatness. Use the stock "O-ring". Thin layer of Drei Bond on that O-ring (between the O-ring and my baffle.)
3. Tighten the hardware, before the Drei Bond goes off. Run around perimeter of completed installation with your fingertip. Make a nice, thin, flat "caulking" job about 1/4" total width. Wipe off excess.
(For metal filler necks, I have a new trick gasket that is made from the same material as my pan gaskets.)
I don't know squat about supercharged cars, but I would question the sanity of blocking off the only direct vents to the crankcase by blocking off the ports on the filler neck.
And if you decide to do this....think about it....my extra baffle is useless.
Consider buying my valve cover oil separators.....absolutely one of the very best "breather system" upgrades we've invented.
The block is rarely/never warped at the filler neck....and if it is, there is more wrong than just that!
Here's what I do:
1.Thin layer of Drei Bond between block and my baffle.
2. Plastic Filler Neck: Check for flatness. Use the stock "O-ring". Thin layer of Drei Bond on that O-ring (between the O-ring and my baffle.)
3. Tighten the hardware, before the Drei Bond goes off. Run around perimeter of completed installation with your fingertip. Make a nice, thin, flat "caulking" job about 1/4" total width. Wipe off excess.
(For metal filler necks, I have a new trick gasket that is made from the same material as my pan gaskets.)
I don't know squat about supercharged cars, but I would question the sanity of blocking off the only direct vents to the crankcase by blocking off the ports on the filler neck.
And if you decide to do this....think about it....my extra baffle is useless.
Consider buying my valve cover oil separators.....absolutely one of the very best "breather system" upgrades we've invented.
I considered them, but I didn't want to pull the cam covers, as I never seem to get the spark plug towers sealed properly again and end up with oil leaks. (Is there a trick to it?) But, I also didn't want to pull the intake and I ended up doing that anyway. :-) So, might as well do these while the engine is out.
I just ordered an "O" and an "H" from Mary.
Last edited by Brett Jenkins; 09-11-2020 at 05:39 PM.
I considered them, but I didn't want to pull the cam covers, as I never seem to get the spark plug towers sealed properly again and end up with oil leaks. (Is there a trick to it?) But, I also didn't want to pull the intake and I ended up doing that anyway. :-) So, might as well do these while the engine is out.
I just ordered an "O" and an "H" from Mary.
I agree. The spark plug towers were a constant battle, for me, too. I tried "doubling up" the aluminum washers to squeeze the valve covers tighter, with no success.
I finally came to the conclusion that the seal rings were thinner than they originally were (I've used all three of the major manufacturer's offerings.....and still had leaks.)
In desperation, I finally added Drei Bond to these seals.
Thin layer between the valve cover and the seal. Thin layer on the seal side that touches the head. Yes, keeping them on the valve cover, in the correct location is impossible, but as long as they are "close" to the correct position when you install the valve cover, they seem to find their own home. And it is really easy to see the entire black inner diameter all the way around, by simply looking down the spark plug opening. I have everything ready to go, before I put Drei Bond on either side....and as soon as humanly possible, I put in the valve cover hardware and run it down, with a Snap Off electric screw tool. I then put my finger down into the spark plug hole and smear the (still wet) residual Drei Bond all the way around the two aluminum surfaces and the visible black rubber. Again, a bead about 1/4" wide is about all you need. Then I finish torquing the hardware.
Haven't had one even sweat, since I started doing this (versus having them all seep, before.)
Drei Bond is your friend....as long as you don't use it on paper style gaskets.
This is a great thread to resurrect to ask a couple questions as I put my engine back together.
A. Oil filler neck baffle installation order. Please correct, add/remove as necessary
1. Drei-bond on block
2. Gasket
3. Drei-bond on gasket
4. GB baffle
5. Drei-bond on baffle
6. Oil filler neck with stock baffle.
B. For a boosted engine, it was suggested to block off both ports on my oil filler neck, as well as the port on the MAF boot. Is it ok to run a hose from one port to the other on the oil filler neck, with hose clamps? On an 89 engine, is it suggested to then tie the 2 cam cover breather hoses on the LS together and vent to a catch can/separator or what?
Brett,
I run a modified Murph supercharger kit on my car and have gone through many variations of breather systems. I currently run Greg Brown's baffle and cam cover mods on my car. I capped the bottom ports of the oil fill neck and added two at the top.
Here's a diagram:
I've run this for the last 7 years and have not experience any problems with this set up. That includes 5 Open Road Races at 170 mph average and 2 at 180 mph average classes. In fact the catch cans get so little oil (mostly water vapor) that you could probably use just one.
__________________
George
90 S4 Grand Prix White (Murf #5 - 219.0 mph top speed)
94 GTS 5-Speed Midnight Blue
06 Cayenne S Havanna/Sand Beige (PASM) http://928.jorj7.com
05-07-2015, 12:01 PM
George Layton March 2014
