Another stupid idea, this time for strokers
03-06-2009, 11:53 AM
#1
Nordschleife Master
Thread Starter
Another stupid idea, this time for strokers
Ok, here's another stupid idea that popped in my head, and another thread. You are probably tired of these, but it doesn't matter since you'll just ignore this, which is probably the smart thing to do. Anyways, here's something dumb that you shouldn't try.
How about using Subaru WRX STi EJ25 pistons for stroker builds?
The pistons have the same diameter, the pin is only 1mm narrower than 928's, and the engine dimensions are otherwise very similar. The pin for Subaru is 23 mm and 24 mm for stock Porsche 928. The dish is 22cc for Subaru and 25cc for stock s4.
I think the compression height is 30.7 mm for the Subaru piston and 42.6 mm for the stock 928 piston. This would give one 11.9 mm to play with for longer stroke and/or longer rod.
Why bother? The Subaru pistons are extremely strong and light. See for example: http://cgi.ebay.co.uk/SUBARU-WRX-STI...215139003r7224
In any case, just surfing the databases, bored. Please ignore everything above beyond its entertainment value.
How about using Subaru WRX STi EJ25 pistons for stroker builds?
The pistons have the same diameter, the pin is only 1mm narrower than 928's, and the engine dimensions are otherwise very similar. The pin for Subaru is 23 mm and 24 mm for stock Porsche 928. The dish is 22cc for Subaru and 25cc for stock s4.
I think the compression height is 30.7 mm for the Subaru piston and 42.6 mm for the stock 928 piston. This would give one 11.9 mm to play with for longer stroke and/or longer rod.
Why bother? The Subaru pistons are extremely strong and light. See for example: http://cgi.ebay.co.uk/SUBARU-WRX-STI...215139003r7224
In any case, just surfing the databases, bored. Please ignore everything above beyond its entertainment value.
03-06-2009, 11:59 AM
#2
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Off the cuff...
Is the Subaru block the same material as the 928 block? If not, then you must either coat the block, or perhaps the pistons. If either of those are required, then going to an less expensive piston like a JE would seem to allow you whatever configuration you want at a lower price.
Is the Subaru block the same material as the 928 block? If not, then you must either coat the block, or perhaps the pistons. If either of those are required, then going to an less expensive piston like a JE would seem to allow you whatever configuration you want at a lower price.
03-06-2009, 12:45 PM
#3
Nordschleife Master
Thread Starter
I said it was a stupid idea? ;-)
In any case, I think one could take these http://store.jepistons.com/256058.aspx and then send them to be PC-9 coated at Swain to run on alusil. (Then maybe buying a new motor if PC-9 is not all that it's cracked up to be...)
In any case, I think one could take these http://store.jepistons.com/256058.aspx and then send them to be PC-9 coated at Swain to run on alusil. (Then maybe buying a new motor if PC-9 is not all that it's cracked up to be...)
Off the cuff...
Is the Subaru block the same material as the 928 block? If not, then you must either coat the block, or perhaps the pistons. If either of those are required, then going to an less expensive piston like a JE would seem to allow you whatever configuration you want at a lower price.
Is the Subaru block the same material as the 928 block? If not, then you must either coat the block, or perhaps the pistons. If either of those are required, then going to an less expensive piston like a JE would seem to allow you whatever configuration you want at a lower price.
03-06-2009, 01:13 PM
#4
Road Warrior
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+1 on what stan said.... also, custom JE's are pretty cheap at 1k/set. course you do have to nikasil the block 1st, but that has lots of additional benefits anyway.
main reason not to use jap parts is that stupid jingle - zoom, zoom, zoom it'll start making... enough to drive U nuts and even w/a german accent it just doesn't seem right w/a pcar
main reason not to use jap parts is that stupid jingle - zoom, zoom, zoom it'll start making... enough to drive U nuts and even w/a german accent it just doesn't seem right w/a pcar
03-06-2009, 01:25 PM
#5
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Tuomo the thing about being on the cutting edge is YOU often get cut ! Most people only take one shot at building their dream engine and should it turn into a nightmare and consume much of the available credit card balances they are forced to bail on the project. Trust me on his the project will ALWAYS take twice as long as you expect and cost twice as much ! And that is BEST case ! We have people who post who have spent $100,000 on their 928 project.
03-06-2009, 01:56 PM
#6
Nordschleife Master
Thread Starter
I am not going to put those Subaru pistons into my Porsche! What, you think I am crazy?! ;-) But some people put Chevy stuff etc. in their Porsches, so I thought that maybe someone would be insane enough to think about this for a second before rejecting the idea. Sanity is overrated.
Fortunately, my project is not one in which personal credit is likely to be necessary. (Famous last words?) Unless I have to buy a house with a big garage (from a foreclosure auction, of course, the stuff doesn't trade anymore outside those). In any case, pretty much the worst thing that can happen is that my pride is hurt and someone gets a great deal on a pile of combined scrap metal and car parts! It's a win win for the rennlist, no matter how my project goes!
But I hear you, and I also get the point of Ryan Perella now that I am a bit calmer, that changing everything at once is going to be an "adventure." So what I am planning, and maybe this never works out, is to keep as many of the important design decisions and interfaces between components stock. For example:
- Stock stroke
- Stock bore
- Stock crank
- Stock rod dimensions
- Stock piston pin diameter
- Stock compression height
- Stock valve length
- Stock valve collet angle
- Stock bearings (with one possible modification to the mains)
- No shaving off the head or thick head gaskets
- Stock computers (reprogrammed)
- Stock fuel injector external dimensions
This is going to be much less radical than any stroker project beyond going to the GTS crank.
Even within the confines of those parameters, I am mostly speculating and bouncing off ideas here. They are just ideas. Not all ideas are good or should be even tried! (Although in other contexts my motto has often been I try anything twice...)
Fortunately, my project is not one in which personal credit is likely to be necessary. (Famous last words?) Unless I have to buy a house with a big garage (from a foreclosure auction, of course, the stuff doesn't trade anymore outside those). In any case, pretty much the worst thing that can happen is that my pride is hurt and someone gets a great deal on a pile of combined scrap metal and car parts! It's a win win for the rennlist, no matter how my project goes!
But I hear you, and I also get the point of Ryan Perella now that I am a bit calmer, that changing everything at once is going to be an "adventure." So what I am planning, and maybe this never works out, is to keep as many of the important design decisions and interfaces between components stock. For example:
- Stock stroke
- Stock bore
- Stock crank
- Stock rod dimensions
- Stock piston pin diameter
- Stock compression height
- Stock valve length
- Stock valve collet angle
- Stock bearings (with one possible modification to the mains)
- No shaving off the head or thick head gaskets
- Stock computers (reprogrammed)
- Stock fuel injector external dimensions
This is going to be much less radical than any stroker project beyond going to the GTS crank.
Even within the confines of those parameters, I am mostly speculating and bouncing off ideas here. They are just ideas. Not all ideas are good or should be even tried! (Although in other contexts my motto has often been I try anything twice...)
Tuomo the thing about being on the cutting edge is YOU often get cut ! Most people only take one shot at building their dream engine and should it turn into a nightmare and consume much of the available credit card balances they are forced to bail on the project. Trust me on his the project will ALWAYS take twice as long as you expect and cost twice as much ! And that is BEST case ! We have people who post who have spent $100,000 on their 928 project.
03-06-2009, 02:46 PM
#7
Road Warrior
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no doubt stock is fine, proven and safe.
but be advised, the temptation to "make things just a bit better" often disrupts the entire balance/design and often results in a complete redesign/upgrade due to the codependencies inherent in a modern motor. for example - change the crank to a gts crank? u just required changes in bearings, cams, fuel management, rods, pistons, etc...
nothing wrong w/exploring, that's how I did mine and many others here have done some amazing things. I was one of, if not the 1st to create custom JE's, dual mapped late model ECU's, nickisil, use A series carrillo rods, late model/custom cams, heads, intake, oil control, etc all in 1 motor... took almost 2yrs to complete, but results were/are awesome too.
do a search here on "stroker" and you'll see some of the discussions / decisions that have gone into great detail on what has to be changed just from a "simple crank change". might save you some money and pain, give you some good ideas.
also keep in mind, there are tons of changes done under the hood based on MY - oil pump gears, tbelt, tensioners, harnesess, valves, heads, oil control, ECU's, fuel system, exhaust, etc... it's not plug and play btween MY's by any means. undoubtedly cheaper to go buy an old 240Z or 911 and slap in a 350 cheby crate motor
but be advised, the temptation to "make things just a bit better" often disrupts the entire balance/design and often results in a complete redesign/upgrade due to the codependencies inherent in a modern motor. for example - change the crank to a gts crank? u just required changes in bearings, cams, fuel management, rods, pistons, etc...
nothing wrong w/exploring, that's how I did mine and many others here have done some amazing things. I was one of, if not the 1st to create custom JE's, dual mapped late model ECU's, nickisil, use A series carrillo rods, late model/custom cams, heads, intake, oil control, etc all in 1 motor... took almost 2yrs to complete, but results were/are awesome too.
do a search here on "stroker" and you'll see some of the discussions / decisions that have gone into great detail on what has to be changed just from a "simple crank change". might save you some money and pain, give you some good ideas.
also keep in mind, there are tons of changes done under the hood based on MY - oil pump gears, tbelt, tensioners, harnesess, valves, heads, oil control, ECU's, fuel system, exhaust, etc... it's not plug and play btween MY's by any means. undoubtedly cheaper to go buy an old 240Z or 911 and slap in a 350 cheby crate motor
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03-06-2009, 02:59 PM
#8
Nordschleife Master
Thread Starter
I am planning to do what at this point seems to be a revolutionary thing, namely keeping the stock crank, stroke, and bore and planning to build a 5.0L engine! And I would bet most people on the board at this point would probably bet against me ever getting it done and running. ;-O
If I could just get Dennis Kao's engine it would be perfect! Except I would like to have lower compression pistons. And lighter rods. And maybe beehive springs. And... And... You get the point!!! ;-)
If I could just get Dennis Kao's engine it would be perfect! Except I would like to have lower compression pistons. And lighter rods. And maybe beehive springs. And... And... You get the point!!! ;-)
no doubt stock is fine, proven and safe.
but be advised, the temptation to "make things just a bit better" often disrupts the entire balance/design and often results in a complete redesign/upgrade due to the codependencies inherent in a modern motor. for example - change the crank to a gts crank? u just required changes in bearings, cams, fuel management, rods, pistons, etc...
nothing wrong w/exploring, that's how I did mine and many others here have done some amazing things. I was one of, if not the 1st to create custom JE's, dual mapped late model ECU's, nickisil, use A series carrillo rods, late model/custom cams, heads, intake, oil control, etc all in 1 motor... took almost 2yrs to complete, but results were/are awesome too.
do a search here on "stroker" and you'll see some of the discussions / decisions that have gone into great detail on what has to be changed just from a "simple crank change". might save you some money and pain, give you some good ideas.
also keep in mind, there are tons of changes done under the hood based on MY - oil pump gears, tbelt, tensioners, harnesess, valves, heads, oil control, ECU's, fuel system, exhaust, etc... it's not plug and play btween MY's by any means. undoubtedly cheaper to go buy an old 240Z or 911 and slap in a 350 cheby crate motor
but be advised, the temptation to "make things just a bit better" often disrupts the entire balance/design and often results in a complete redesign/upgrade due to the codependencies inherent in a modern motor. for example - change the crank to a gts crank? u just required changes in bearings, cams, fuel management, rods, pistons, etc...
nothing wrong w/exploring, that's how I did mine and many others here have done some amazing things. I was one of, if not the 1st to create custom JE's, dual mapped late model ECU's, nickisil, use A series carrillo rods, late model/custom cams, heads, intake, oil control, etc all in 1 motor... took almost 2yrs to complete, but results were/are awesome too.
do a search here on "stroker" and you'll see some of the discussions / decisions that have gone into great detail on what has to be changed just from a "simple crank change". might save you some money and pain, give you some good ideas.
also keep in mind, there are tons of changes done under the hood based on MY - oil pump gears, tbelt, tensioners, harnesess, valves, heads, oil control, ECU's, fuel system, exhaust, etc... it's not plug and play btween MY's by any means. undoubtedly cheaper to go buy an old 240Z or 911 and slap in a 350 cheby crate motor
03-06-2009, 03:39 PM
#9
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03-06-2009, 05:00 PM
#12
Nordschleife Master
Thread Starter
Speaking of pistons, and custom pistons in particular... How about this for another stupid idea:
Suppose one gets custom pistons. What kind of piston dish should one get?
I have this theory that I came up with while trying to avoid watching the stock market cratering and world ending. It seems that it would be good to have the combustion chamber nice and compact, especially at the point when the pressure in the cylinder is highest at about 15 degrees ATDC crank angle. Why not shape the piston dish such that all points on the dish surface are equally far from the spark at that crank angle?
Just for the hell of it, I tried to make a little spreadsheet that would help to compute how deep and how wide spherical dish one would need, depending on what compression ratio one needs.
All distances measured in cm Case 1 Case 2 Case 3 Case 4
Bore b 10.00 10.00 10.00 10.00
Stroke s 7.89 7.89 7.89 7.89
Peak cylinder pressure angle after TDC (degrees) pd 15.00 15.00 15.00 15.00
Peak cylinder rpessure angle after TDC (radians) pr 0.26 0.26 0.26 0.26
Rod length l 15.00 15.00 15.00 15.00
Distance from spark to deck d1 1.00 1.00 1.00 1.00
Distance deck to piston deck at pd crank angle d2 0.17 0.17 0.17 0.17
Dish depth from piston deck d3 1.00 1.50 2.00 2.50
Distance of spark from dish bottom r 2.17 2.67 3.17 3.67
Dish volume V 5.77 15.33 31.45 55.68
Radius of the dish h 1.83 2.40 2.95 3.48
S4 compression ratio c 12.31 10.63 8.70 6.92
This is probably a stupid idea, and the spreadsheet is wrong. It's useless. I suspect that playing with it will nevertheless beat working in the financial services industry today. Typing it up sure did!
Formulas
Row 6 =(F5/360)*2*PI()
Row 9 =-((F4/2)*COS(F6)+SQRT(F7^2-((F4/2)^2)*(SIN(F6)^2))-(F4/2)-F7)
Row 11 =F10+F9+F8
Row 12 =(PI()/3)*(F10^2)*(3*F11-F10)
Row 13 =SQRT(F11^2-(F11-F10)^2)
Row 14 = (((F3/2)^2)*PI()*F4+(41+8+F12))/(41+8+F12)
Suppose one gets custom pistons. What kind of piston dish should one get?
I have this theory that I came up with while trying to avoid watching the stock market cratering and world ending. It seems that it would be good to have the combustion chamber nice and compact, especially at the point when the pressure in the cylinder is highest at about 15 degrees ATDC crank angle. Why not shape the piston dish such that all points on the dish surface are equally far from the spark at that crank angle?
Just for the hell of it, I tried to make a little spreadsheet that would help to compute how deep and how wide spherical dish one would need, depending on what compression ratio one needs.
All distances measured in cm Case 1 Case 2 Case 3 Case 4
Bore b 10.00 10.00 10.00 10.00
Stroke s 7.89 7.89 7.89 7.89
Peak cylinder pressure angle after TDC (degrees) pd 15.00 15.00 15.00 15.00
Peak cylinder rpessure angle after TDC (radians) pr 0.26 0.26 0.26 0.26
Rod length l 15.00 15.00 15.00 15.00
Distance from spark to deck d1 1.00 1.00 1.00 1.00
Distance deck to piston deck at pd crank angle d2 0.17 0.17 0.17 0.17
Dish depth from piston deck d3 1.00 1.50 2.00 2.50
Distance of spark from dish bottom r 2.17 2.67 3.17 3.67
Dish volume V 5.77 15.33 31.45 55.68
Radius of the dish h 1.83 2.40 2.95 3.48
S4 compression ratio c 12.31 10.63 8.70 6.92
This is probably a stupid idea, and the spreadsheet is wrong. It's useless. I suspect that playing with it will nevertheless beat working in the financial services industry today. Typing it up sure did!
Formulas
Row 6 =(F5/360)*2*PI()
Row 9 =-((F4/2)*COS(F6)+SQRT(F7^2-((F4/2)^2)*(SIN(F6)^2))-(F4/2)-F7)
Row 11 =F10+F9+F8
Row 12 =(PI()/3)*(F10^2)*(3*F11-F10)
Row 13 =SQRT(F11^2-(F11-F10)^2)
Row 14 = (((F3/2)^2)*PI()*F4+(41+8+F12))/(41+8+F12)
03-06-2009, 05:47 PM
#13
Nordschleife Master
https://rennlist.com/forums/928-foru...o-for-8-a.html
Also, don't be so self denegrating - you're going to run into resistance from people when pushing boundaries wherever in life you push. Groupthink and egoism are inevitable in tight communities.
[Note to potential flamers - I'm not saying bad things about you personally
it is a comment on human nature in general]Just wear your extra thick internet skin, and realise that text on a forum is a less than ideal medium for effective communication. Lots of the people here are probably very different over a beer
Keep pushing the ideas - there are a few people who are very knowledgeable (not me - I'm just learning) and read these forums but rarely post these days. Remember that for most people, a troker is a huuuge expense, and the idea of experimenting for more power with the build is scary compared to going with a known proven formula (of course, the known proven formula was at some point probably faced with detractors who said it wouldn't work when proposed!)
Last edited by Hilton; 03-06-2009 at 06:21 PM.
03-06-2009, 06:27 PM
#14
Nordschleife Master
Thread Starter
With Subaru Outback pistons one would be straight outta closet.
03-06-2009, 08:00 PM
#15
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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!