Breather Venting, weight reduction and other ramblings.
03-07-2009, 08:31 PM
#1
Burning Brakes
Thread Starter
Join Date: May 2007
Location: Birmingham, UK.
Posts: 963
Likes: 0
Received 0 Likes
on
0 Posts
Breather Venting, weight reduction and other ramblings.
On many cars, it seems a common practice - law not withstanding of course - to remove the recycling of the breather fumes to the intake system and vent to atmosphere instead.
Another common one (not on our engines) is the coolant passing thru the throttle body - good for figures not so good for performance i believe.
Now i know Porsha are obviously very clever - but are there and small mods like this that do make a difference?
Personally, i've just bought a new breather hose as mine is split, i just thought i'd ask the question prompted by the ITB thread and the fact i need to replace the hose.
then i'm thinking about weight reduction. the trip out in the 9meister 964 got me thinking, i really need to lose weight. and the car! 1295kg at the moment, so obviously lots more to go i suppose, it just depends on a cost per performance, if i wont notice 20kg, whats the point, if 100kg is noticable, but going to cost thousands, again, not worth it. I just want to make sure i've done all the easy stuff. sunroof is the next contender to go, i'll glue some smoked perspex in for now until i go for the carbon roof skin, the front AC fan\rad\evap stuff has still got to come out, so there has got to be some weight to come from there.
I'm going to do perspex rear window and side windows, thinking about ditching the spare tyre and fabbing in some reinforcement.
How were the cup cars so light?
Basically, is there any other crap to come out?
I'm on rs lightweight carpets, light door cards, light seats...
I think I'm just bored and need to do some modding.
Must be something i can do!
Another common one (not on our engines) is the coolant passing thru the throttle body - good for figures not so good for performance i believe.
Now i know Porsha are obviously very clever - but are there and small mods like this that do make a difference?
Personally, i've just bought a new breather hose as mine is split, i just thought i'd ask the question prompted by the ITB thread and the fact i need to replace the hose.
then i'm thinking about weight reduction. the trip out in the 9meister 964 got me thinking, i really need to lose weight. and the car! 1295kg at the moment, so obviously lots more to go i suppose, it just depends on a cost per performance, if i wont notice 20kg, whats the point, if 100kg is noticable, but going to cost thousands, again, not worth it. I just want to make sure i've done all the easy stuff. sunroof is the next contender to go, i'll glue some smoked perspex in for now until i go for the carbon roof skin, the front AC fan\rad\evap stuff has still got to come out, so there has got to be some weight to come from there.
I'm going to do perspex rear window and side windows, thinking about ditching the spare tyre and fabbing in some reinforcement.
How were the cup cars so light?
Basically, is there any other crap to come out?
I'm on rs lightweight carpets, light door cards, light seats...
I think I'm just bored and need to do some modding.
Must be something i can do!
03-07-2009, 09:26 PM
#2
RL Community Team
Rennlist Member
Rennlist Member
Did you ever see Robert Linton's post on the 5HP modification with regards to the breather fitting? You can simply buy this GT3 part (one-way valve) and hose clamp it into the vent line to achieve the same result (without needing his unobtainable part).
03-08-2009, 01:38 AM
#4
Addict
Rennlist Member
Rennlist Member
Join Date: Apr 2002
Location: Apex, NC
Posts: 2,426
Likes: 0
Received 0 Likes
on
0 Posts
they work 
i've got a prototype on my car.
best bang for the buck up to a point is getting lighter. - in Auto X trim my car is 2575 or 1170.5kg on Cup 1's.
Bob's car is 1000kg i believe or slightly less - w/Ac, stereo, etc.
i figure i can get it down to 2500 w/ the BBS Mg's and further deleting of unnessecary stuff.
for instance your headline has a pad above it which weights 2lbs (1Kg)
i don't run a spare (no debate please), remove all the lower dash, Recaro RSR seats, light weigh FB's (wood, Rennline for street), no AC stuff at all, no Oil cooler fan, no bumper bars F/R. only a B/K harness mount. H4's w/plexi lens, Stripped trucnk/boot, no air bags/sensors, no radio, etc. Al. Hood, etc....
no reason to do any panels other than the hood (Boot) and the engine lid, IMHO. \
an Off can be bad. (my last one i was running the bumper bars and a full cage, btw)
i've got a prototype on my car. best bang for the buck up to a point is getting lighter. - in Auto X trim my car is 2575 or 1170.5kg on Cup 1's.
Bob's car is 1000kg i believe or slightly less - w/Ac, stereo, etc.
i figure i can get it down to 2500 w/ the BBS Mg's and further deleting of unnessecary stuff.
for instance your headline has a pad above it which weights 2lbs (1Kg)
i don't run a spare (no debate please), remove all the lower dash, Recaro RSR seats, light weigh FB's (wood, Rennline for street), no AC stuff at all, no Oil cooler fan, no bumper bars F/R. only a B/K harness mount. H4's w/plexi lens, Stripped trucnk/boot, no air bags/sensors, no radio, etc. Al. Hood, etc....
no reason to do any panels other than the hood (Boot) and the engine lid, IMHO. \
an Off can be bad. (my last one i was running the bumper bars and a full cage, btw)
03-08-2009, 11:32 AM
#7
Burning Brakes
Thread Starter
Join Date: May 2007
Location: Birmingham, UK.
Posts: 963
Likes: 0
Received 0 Likes
on
0 Posts
i do use it on the road aswell, but the original plan was to strip it totally, but when the glue was a bugger to get off i went for the carpets instead.
cup car spec - with cup car parts is WAY over my budget!
cup car spec - with cup car parts is WAY over my budget!
Trending Topics
03-08-2009, 11:32 AM
#8
Nordschleife Master
You can simply buy this GT3 part (one-way valve) and hose clamp it into the vent line to achieve the same result (without needing his unobtainable part).
On an engine dyno with a clear tube connected to the breather system, I've seen a column of oil come out of the breather section at higher RPM. This of course depends on the ring seal and overall crankcase pressure.
03-08-2009, 01:37 PM
#9
RL Community Team
Rennlist Member
Rennlist Member
It's not quite that simple. Depending on your engine's heath, and the RPM it is run, you may have issues with the GT3 part. This year we tried it twice on a 993RSR and the first time it caught the car on fire on the dyno due to the oil pressure pulling the hose off the breather cover, and the second time it blew out the rear main seal. There are some other things that need to be taken into consideration here to make the system work. Don't forget that the GT3 has a 2 stage scavage section in the oil pump, and two additional scavage pumps, one on each side of the cam tower which help evacuate oil out of the engine case.
On an engine dyno with a clear tube connected to the breather system, I've seen a column of oil come out of the breather section at higher RPM. This of course depends on the ring seal and overall crankcase pressure.
On an engine dyno with a clear tube connected to the breather system, I've seen a column of oil come out of the breather section at higher RPM. This of course depends on the ring seal and overall crankcase pressure.
Just kidding.
Interesting findings, though... did it blow out, or suck in the main seal to make it leak?
03-08-2009, 01:53 PM
#11
Racer
Join Date: Dec 2003
Posts: 497
Likes: 0
Received 0 Likes
on
0 Posts
My race car was the test subject for this experiment. Once I got the breather hose to stay on, the rear crankshaft seal was blown out by crankcase pressure. Once a new seal was installed and the valve removed, there were no more problems.
The reasons for all the trouble are not really that clear. What is clear is that you cannot just install this part and expect it to work flawlessly on a 993 RSR sprint engine.
I don't know if the Cartridge Ltd. part differs in operation from what I used. I don't want to imply that the Cartridge Ltd. part will create the same problems because I do not know if it would or would not.
Chris Cervelli
Spline Technologies
The reasons for all the trouble are not really that clear. What is clear is that you cannot just install this part and expect it to work flawlessly on a 993 RSR sprint engine.
I don't know if the Cartridge Ltd. part differs in operation from what I used. I don't want to imply that the Cartridge Ltd. part will create the same problems because I do not know if it would or would not.
Chris Cervelli
Spline Technologies
03-09-2009, 12:52 AM
#12
RL Community Team
Rennlist Member
Rennlist Member
Chris and Geoffrey, that almost sounds like the valve was installed backwards! The original idea was to create a vacuum in there, right? Neat concept to reduce windage...
03-09-2009, 07:54 AM
#13
Racer
Join Date: Dec 2003
Posts: 497
Likes: 0
Received 0 Likes
on
0 Posts
The valve was not installed backwards.
I think the opening is too small to let the pressure out. The water cooled engines have the three additional scavenge pumps (and probably much less blowby) which must greatly reduce the pressure in the case.
Chris Cervelli
Spline Technologies
I think the opening is too small to let the pressure out. The water cooled engines have the three additional scavenge pumps (and probably much less blowby) which must greatly reduce the pressure in the case.
Chris Cervelli
Spline Technologies
03-09-2009, 10:38 AM
#14
Nordschleife Master
I think there are two issues; one is the amount of oil the oil pump can scavage out of the case, and second, the restriction the valve creates in the breather circuit.
The GT3R oil pump is the best production pump available from Porsche (outside of some of the specialty pumps like GT1, 962, 959, etc) because it has a 2 stage scavage section compared with a single stage scavage section of the 964 oil pump. I believe it also has a smaller pressure section which reduces the amount of excess oil that will be bypassed from the internal pressure release circuit and dumped into the case. In addition, the GT3 runs higher oil pressure through the oil circuit (which uses more oil). Once the pump can keep up with removal of oil, it will begin to create a vacuum in the case (assuming it is sealed). On a GT3 Cup car at sea level, I see absolute pressure (100kPa absolute = 0in of vacuum) of 35kPa to 45kPa in the crankcase as it is running. On Chris's car, with the standard 964 oil pump, it is likely that it was not able to keep up with the oil scavaging under certain conditions which resulted in excess oil in the crankcase. Normally this oil will be pushed back to the tank through the breather on the top of the engine by the internal crankcase pressure. However, since the valve is designed to flow air, not liquid and is too restrictive and the oil continued to accumulate in the case and the pressure eventually pushed out the rear main seal. I believe this was problem #1 - the oil pump capacity on both the scavage and the pressure circuits.
The second problem is that the crankcase is getting pressurized. This occurs from the ring package sealing. The ring package on a 3.8RSR piston is designed to operate to 7600, however we all run them to 8000rpm. These rings are very thick (large) and do not operate as well at higher RPM as a more modern thinner ring package. An example is that a Nascar engine that runs to 9500rpm with a 500g piston/pin combination and 106.3mm bore will run a top ring as small as .6mm where the RSR is 1.5mm. At the higher RPMs, the rings can flutter in the ring groove and lose the seal on the bore. This will cause excess crankcase pressure as the combustion pressure is pushed past the rings into the crankcase. The air cooled engine also has an unstable cylinder shape due to the heating and cooling of the air cooled cylinder and will not retain its shape as well as a water cooled cylinder in the later engines. Though the Gotze rings are ductile iron and soft, due to their size, they cannot conform to the changing bore size as well as a thinner ring. We saw this on Chris's car on the dyno when the engine was being held steady state at 8000rpm when the oil from inside the case was pushing against the valve which could not flow enough oil and it pulled the hose off the oil breather cap and pumped 2 qts of oil all over the engine in about 3 seconds and caught fire on the headers.
I'm sure there are things that we're missing, however, this was our experiences with the check valve (GT3 part).
The GT3R oil pump is the best production pump available from Porsche (outside of some of the specialty pumps like GT1, 962, 959, etc) because it has a 2 stage scavage section compared with a single stage scavage section of the 964 oil pump. I believe it also has a smaller pressure section which reduces the amount of excess oil that will be bypassed from the internal pressure release circuit and dumped into the case. In addition, the GT3 runs higher oil pressure through the oil circuit (which uses more oil). Once the pump can keep up with removal of oil, it will begin to create a vacuum in the case (assuming it is sealed). On a GT3 Cup car at sea level, I see absolute pressure (100kPa absolute = 0in of vacuum) of 35kPa to 45kPa in the crankcase as it is running. On Chris's car, with the standard 964 oil pump, it is likely that it was not able to keep up with the oil scavaging under certain conditions which resulted in excess oil in the crankcase. Normally this oil will be pushed back to the tank through the breather on the top of the engine by the internal crankcase pressure. However, since the valve is designed to flow air, not liquid and is too restrictive and the oil continued to accumulate in the case and the pressure eventually pushed out the rear main seal. I believe this was problem #1 - the oil pump capacity on both the scavage and the pressure circuits.
The second problem is that the crankcase is getting pressurized. This occurs from the ring package sealing. The ring package on a 3.8RSR piston is designed to operate to 7600, however we all run them to 8000rpm. These rings are very thick (large) and do not operate as well at higher RPM as a more modern thinner ring package. An example is that a Nascar engine that runs to 9500rpm with a 500g piston/pin combination and 106.3mm bore will run a top ring as small as .6mm where the RSR is 1.5mm. At the higher RPMs, the rings can flutter in the ring groove and lose the seal on the bore. This will cause excess crankcase pressure as the combustion pressure is pushed past the rings into the crankcase. The air cooled engine also has an unstable cylinder shape due to the heating and cooling of the air cooled cylinder and will not retain its shape as well as a water cooled cylinder in the later engines. Though the Gotze rings are ductile iron and soft, due to their size, they cannot conform to the changing bore size as well as a thinner ring. We saw this on Chris's car on the dyno when the engine was being held steady state at 8000rpm when the oil from inside the case was pushing against the valve which could not flow enough oil and it pulled the hose off the oil breather cap and pumped 2 qts of oil all over the engine in about 3 seconds and caught fire on the headers.
I'm sure there are things that we're missing, however, this was our experiences with the check valve (GT3 part).
03-09-2009, 10:47 PM
#15
Demon,
Since buying my car, it's been my (admittedly random) mission to see how much weight I could get out of my car, without going completely stripped and/or "full race". My car is probably used 50% of the time on the street, and I drive it to and from track events, so I still desire SOME accommodations (albeit minimal).
My best advice is don't overlook the "little" things. If you really want to save weight, literally remove EVERYTHING you can do without. The little stuff will add up, and combined with the bigger hits (e.g., remove sunroof, swap seats, etc.), you may be surprised where you can end up. I think I've pretty much reached the end, for my tastes: 2,650lbs (all fluids, 1/2 tank, no driver).
I certainly can't say, in the end, it's been inexpensive getting here, but it's been a lot of fun, and great experience (if only for the exercise of taking things apart).
Good luck!
Dave
Since buying my car, it's been my (admittedly random) mission to see how much weight I could get out of my car, without going completely stripped and/or "full race". My car is probably used 50% of the time on the street, and I drive it to and from track events, so I still desire SOME accommodations (albeit minimal).
My best advice is don't overlook the "little" things. If you really want to save weight, literally remove EVERYTHING you can do without. The little stuff will add up, and combined with the bigger hits (e.g., remove sunroof, swap seats, etc.), you may be surprised where you can end up. I think I've pretty much reached the end, for my tastes: 2,650lbs (all fluids, 1/2 tank, no driver).
I certainly can't say, in the end, it's been inexpensive getting here, but it's been a lot of fun, and great experience (if only for the exercise of taking things apart).
Good luck!
Dave