Another stupid idea, this time for strokers
03-06-2009, 08:11 PM
#16
Nordschleife Master
Thread Starter
I think 944 and 951 compression height is about 2.34 mm or so lower than that of 928. All hearsay.
I've thought about the Subaru pistons in the past too . . . at least enough to do a search. Here are some of the piston weights from various suppliers: http://forums.nasioc.com/forums/showthread.php?t=999055
My idea was that you could get 100mm Mahle pistons & have them coated by Mahle Motorsports w/ Ferroprint. Unfortunately, I've read that the Green Bay guys had some issues with their coated Mahles.
Or, as you mentioned, get some JE, Cosworth, CP, etc. pistons & have them coated in Swaintech PC-9. It's tempting when you see CP's for $400 a set (4 pistons) and coating for only $100 more. To my knowledge, no 928 has that combo, so you could be a pioneer! One problem with these Subaru pistons is that the valve reliefs probably don't match the 928 or 968 valves. Another would be if the ring pack compatible with the Alusil bore would match up to the available ring grooves/lands.
A third combo would be to use the Woessner 944 pistons & rods. Supposedly they have a coating meant to work with Alusil. According to their catalog, their 944 rods are 150mm, just like stock. So I have to assume their compression height is the same as stock too. You wouldn't be altering the rod:stroke ratio but again you'd be on the bleeding edge.
That's nice of you to say. I love this motor and the pull in 3rd gear to 7100 rpm. The whole thing has been a great experience, both working on the motor & the final result. I gotta give credit to Jim & Bill - they know their stuff!
My idea was that you could get 100mm Mahle pistons & have them coated by Mahle Motorsports w/ Ferroprint. Unfortunately, I've read that the Green Bay guys had some issues with their coated Mahles.
Or, as you mentioned, get some JE, Cosworth, CP, etc. pistons & have them coated in Swaintech PC-9. It's tempting when you see CP's for $400 a set (4 pistons) and coating for only $100 more. To my knowledge, no 928 has that combo, so you could be a pioneer! One problem with these Subaru pistons is that the valve reliefs probably don't match the 928 or 968 valves. Another would be if the ring pack compatible with the Alusil bore would match up to the available ring grooves/lands.
A third combo would be to use the Woessner 944 pistons & rods. Supposedly they have a coating meant to work with Alusil. According to their catalog, their 944 rods are 150mm, just like stock. So I have to assume their compression height is the same as stock too. You wouldn't be altering the rod:stroke ratio but again you'd be on the bleeding edge.
That's nice of you to say. I love this motor and the pull in 3rd gear to 7100 rpm. The whole thing has been a great experience, both working on the motor & the final result. I gotta give credit to Jim & Bill - they know their stuff!
03-07-2009, 08:48 AM
#18
Addict
Rennlist Member
Rennlist Member
In this case hearsay is true. For some strange reason 928 vs 944 compression height is different even though so many other dimensions are same. Plan is to check 928, 951 and 968 piston compression heights later today. This is for one engine project which will use S4 squirter block, GTS crank, hopefully early S4 rods and some custom Alusil pistons. Another option is to use 951 pistons and about 1mm shorter rods. Either shortened stock S4 or some custom rods.
03-07-2009, 08:53 AM
#19
Nordschleife Master
Thread Starter
I think I got that 2.34mm number from you. Hearsay meaning I didn't measure it myself, not to question the reliability. By the way, all the measures and dimensions that you've provided to me and others here are incredibly valuable!
In this case hearsay is true. For some strange reason 928 vs 944 compression height is different even though so many other dimensions are same. Plan is to check 928, 951 and 968 piston compression heights later today. This is for one engine project which will use S4 squirter block, GTS crank, hopefully early S4 rods and some custom Alusil pistons. Another option is to use 951 pistons and about 1mm shorter rods. Either shortened stock S4 or some custom rods.
03-07-2009, 09:38 AM
#21
Nordschleife Master
Thread Starter
bearings
It's IMO the best engine out there so far. This judgment probably reflects mostly my personal preferences.
Here's a question to you. I couldn't find the answer in the existing threads. With the drilled crank, what main bearing modifications did you make? In particular, did you groove #3 in the middle? If you did, how exactly? Or is the crank drilling pattern designed to match with completely stock bearings?
Here's a question to you. I couldn't find the answer in the existing threads. With the drilled crank, what main bearing modifications did you make? In particular, did you groove #3 in the middle? If you did, how exactly? Or is the crank drilling pattern designed to match with completely stock bearings?
03-07-2009, 02:53 PM
#22
Road Warrior
Rennlist Member
Rennlist Member
In this case hearsay is true. For some strange reason 928 vs 944 compression height is different even though so many other dimensions are same. Plan is to check 928, 951 and 968 piston compression heights later today. This is for one engine project which will use S4 squirter block, GTS crank, hopefully early S4 rods and some custom Alusil pistons. Another option is to use 951 pistons and about 1mm shorter rods. Either shortened stock S4 or some custom rods.
be careful w/aftermarket pistons for the alusil block. mahle-porshe pistons use a proprietary ferrostan coating that isn't used by anyone else. mahle motorsports can't even use it either.
I saw a piston recently that looked like crap after only a few hundred miles. coating was gone/motor destroyed.
cheaper to just do nikasil and use custom forged aluminum stuff anyway. and the nikasil has better olification properties, less friction and flat won't wear at all. porsche uses that process on their high end motors for the cgt, 911 TT, as does mercedes, most motorcycle OEMs and other high performance builders - like the Nascar guys, etc..
I siezed a piston once in a race bike w/a nikisil cyl (radiator hose got a stick through it/motor got superheated). all we had to do was break the piston free, run a bead hone through it to get a bit of stuck AL off the bore, and the cyl was perfect!! slapped another piston in and bwaaaahh
try that w/alusil and you'll likely end up with a nice table base/boat anchor block. porsche used that process cause it was cheap, according to their production engineers. still used in cayannes and boxters, iirc.
03-07-2009, 03:26 PM
#23
Nordschleife Master
Thread Starter
Although chrome rings and Swaintech PC-9 pistons apparently work on alusil, my block will be Nikasil coated. Precisely for the reasons you list + the ability to repair any imperfection in the process. Heat conductivity is better and oil just loves to hang out with Nikasil late into the night shooting **** and pounding shots.
I've played with 2-stroke engine Nikasil cylinders. Often outlasted pretty much all other components in an engine. They (Mahle) must have been excited when they came up with the method to apply it cost effectively back in the day in the 60's. AFAIK, they only have one weakness, which is that this stuff dissolves into sulfur fuels. BMW learned it the hard way, it wasn't caught by their QA since they could not possibly imagine the Americans putting such garbage in the gas tank! http://www.usautoparts.net/bmw/engines/nikasil.htm
The history of Ferrocoat / Ferrostan / Ferroprint is interesting. I am confident that Mahle has a workable solution, as I think (but do not know) that my wife's 997 for example has alusil cylinders. So some kind of reliable coating can be applied even today. Without knowing anything about the issues, a layman like me would suspect that the issue of trashing the bore and pistons may have had something to do with the rings. Just a suspicion.
There is a good chance that I'll produce a couple of coffee table cores over the next two years, nikasil or no nikasil! ;-)
I've played with 2-stroke engine Nikasil cylinders. Often outlasted pretty much all other components in an engine. They (Mahle) must have been excited when they came up with the method to apply it cost effectively back in the day in the 60's. AFAIK, they only have one weakness, which is that this stuff dissolves into sulfur fuels. BMW learned it the hard way, it wasn't caught by their QA since they could not possibly imagine the Americans putting such garbage in the gas tank! http://www.usautoparts.net/bmw/engines/nikasil.htm
The history of Ferrocoat / Ferrostan / Ferroprint is interesting. I am confident that Mahle has a workable solution, as I think (but do not know) that my wife's 997 for example has alusil cylinders. So some kind of reliable coating can be applied even today. Without knowing anything about the issues, a layman like me would suspect that the issue of trashing the bore and pistons may have had something to do with the rings. Just a suspicion.
There is a good chance that I'll produce a couple of coffee table cores over the next two years, nikasil or no nikasil! ;-)
be careful w/aftermarket pistons for the alusil block. mahle-porshe pistons use a proprietary ferrostan coating that isn't used by anyone else. mahle motorsports can't even use it either.
I saw a piston recently that looked like crap after only a few hundred miles. coating was gone/motor destroyed.
cheaper to just do nikasil and use custom forged aluminum stuff anyway. and the nikasil has better olification properties, less friction and flat won't wear at all. porsche uses that process on their high end motors for the cgt, 911 TT, as does mercedes, most motorcycle OEMs and other high performance builders - like the Nascar guys, etc..
I siezed a piston once in a race bike w/a nikisil cyl (radiator hose got a stick through it/motor got superheated). all we had to do was break the piston free, run a bead hone through it to get a bit of stuck AL off the bore, and the cyl was perfect!! slapped another piston in and bwaaaahh
try that w/alusil and you'll likely end up with a nice table base/boat anchor block. porsche used that process cause it was cheap, according to their production engineers. still used in cayannes and boxters, iirc.
I saw a piston recently that looked like crap after only a few hundred miles. coating was gone/motor destroyed.
cheaper to just do nikasil and use custom forged aluminum stuff anyway. and the nikasil has better olification properties, less friction and flat won't wear at all. porsche uses that process on their high end motors for the cgt, 911 TT, as does mercedes, most motorcycle OEMs and other high performance builders - like the Nascar guys, etc..
I siezed a piston once in a race bike w/a nikisil cyl (radiator hose got a stick through it/motor got superheated). all we had to do was break the piston free, run a bead hone through it to get a bit of stuck AL off the bore, and the cyl was perfect!! slapped another piston in and bwaaaahh
try that w/alusil and you'll likely end up with a nice table base/boat anchor block. porsche used that process cause it was cheap, according to their production engineers. still used in cayannes and boxters, iirc.
03-08-2009, 06:27 PM
#24
Nordschleife Master
Thread Starter
more mechanical Dawrin awards material
An update to the stupid ideas thread:
How about running this cobination in the valvetrain:
- PAC 7-degree steel retainer, part number R312. Weight 8g. Compresses the spring 1mm more than the Porsche original retainer.
- Crower Modular Ford 4.6 4v beehive spring, part number 68194-X2. Weight 43g, 20g of which reciprocating.
- Porsche original 7-degree valve keepers, part number 928 105 221 10. Weight 2.5g per two pieces
- Ferrea SBC LS1/LS7 seat locator disc, part number SL1066. Weight irrelevant. Compresses the spring 3mm less than the Porsche original
This combo allows the spring to be installed at 2mm longer installed height than the Porsche original outer spring. This extra 2mm gives the stiff and long Modular Ford beehive springs little more room to lower the seated load.
Here are the estimated spring load data:
Height (mm) Height (inches) Computed force (lbf)
37.8 1.486 81 Intake installed height with Ferrea SL1066 locator disc
36.8 1.447 94 Exhaust installed height with Ferrea SL1066 locator disc
28.8 1.132 197 S4 cam intake at max lift
28.8 1.134 196 S4 cam exhaust at max lift
27.8 1.093 209 928MS 32vS1 cam intake at max lift
27.8 1.094 209 928MS 32vS1 cam exhaust at max lift
26.9 1.058 221 928MS 32vS2 cam intake at max lift
26.9 1.058 221 928MS 32vS2 cam exhaust at max lift
26.5 1.044 225 928MS 32vR3 cam intake at max lift
26.6 1.049 224 928MS 32vR3 cam exhaust at max lift
Bit stiff for the street, but for a race engine where wear resistance is less important than preventing valve float this might be worth it.
In an case, don't try this at home! I haven't tried this in an engine. I've just searched catalogs, ordered random parts, and measured them. If you try this, something will possibly go very wrong and wreck your engine. Caveat emptor.
How about running this cobination in the valvetrain:
- PAC 7-degree steel retainer, part number R312. Weight 8g. Compresses the spring 1mm more than the Porsche original retainer.
- Crower Modular Ford 4.6 4v beehive spring, part number 68194-X2. Weight 43g, 20g of which reciprocating.
- Porsche original 7-degree valve keepers, part number 928 105 221 10. Weight 2.5g per two pieces
- Ferrea SBC LS1/LS7 seat locator disc, part number SL1066. Weight irrelevant. Compresses the spring 3mm less than the Porsche original
This combo allows the spring to be installed at 2mm longer installed height than the Porsche original outer spring. This extra 2mm gives the stiff and long Modular Ford beehive springs little more room to lower the seated load.
Here are the estimated spring load data:
Height (mm) Height (inches) Computed force (lbf)
37.8 1.486 81 Intake installed height with Ferrea SL1066 locator disc
36.8 1.447 94 Exhaust installed height with Ferrea SL1066 locator disc
28.8 1.132 197 S4 cam intake at max lift
28.8 1.134 196 S4 cam exhaust at max lift
27.8 1.093 209 928MS 32vS1 cam intake at max lift
27.8 1.094 209 928MS 32vS1 cam exhaust at max lift
26.9 1.058 221 928MS 32vS2 cam intake at max lift
26.9 1.058 221 928MS 32vS2 cam exhaust at max lift
26.5 1.044 225 928MS 32vR3 cam intake at max lift
26.6 1.049 224 928MS 32vR3 cam exhaust at max lift
Bit stiff for the street, but for a race engine where wear resistance is less important than preventing valve float this might be worth it.
In an case, don't try this at home! I haven't tried this in an engine. I've just searched catalogs, ordered random parts, and measured them. If you try this, something will possibly go very wrong and wreck your engine. Caveat emptor.
