Drilling GTS pistons?
02-08-2009, 11:58 AM
#31
Rennlist Member
In fall '93 connecting rods were chabged to stronger ...2R casting number design. Change date on production line was September 14th 1993. I can't recall if its known what engine numbers were first M28/49 (5sp) and M28/50 (automatic) engine to receive ...2R rods. In any case this means some early '94 MY cars still got ...1R rods which according to factory should be changed to later ...2R style whenever rod bolts are opened.
928 GTS engines as of September 14, 1993 received the new connecting rods starting at Engine numbers 85R00533 and 81R50597
Not sure if this helps.
02-08-2009, 02:01 PM
#32
Nordschleife Master
AFAIK all cars which are in reality '92 MY cars have 1st style GTS piston and piston ring variation. They also have block lower half mounted with studs and simpler S4/GT style crank case breather system. These were made between 08/91 and 08/92, US model production started in 01/92.
US VIN used '93 MY P VIN as sales were so slow that PCNA expected some cars to remain unsold so long that they would appear old to buyers if they had '92 MY VIN. US low allows use of next year VIN starting from January 1st of previous year. These 88 cars can be identified with M718 option code. AFAIK they should have '92 MY engine in them.
Automatic gearbox diff lost MY digit from number sequence in '92 MY but at least early '92 MY manual gearboxes still had N in number to identify MY.
All GTS which are in reality '93 MY cars have 2nd style piston and ring setup as do all '94-95 MY cars. At same time in beginning of '93 MY block lower half mounting was changed to bolts and crank case breather setup was changed to include exit at drivers side (left side) cylinder head. These cars were made between 08/92-08/93.
Some time after January 1st 1993 US VIN series where changed to '94 MY R VIN as sales were so slow that PCNA expected some cars to remain unsold so long that they would appear old to buyers if they had '93 MY VIN. These 19 cars can be identified with M718 option code. AFAIK they should have '93 MY engine in them.
Below are true '94 MY cars. They have Cup II wheels without RDS sensors and pollen filter for AC. Automatic cars have dynamic kickdown. These were made between 08/93-08/94.
In fall '93 connecting rods were chabged to stronger ...2R casting number design. Change date on production line was September 14th 1993. I can't recall if its known what engine numbers were first M28/49 (5sp) and M28/50 (automatic) engine to receive ...2R rods. In any case this means some early '94 MY cars still got ...1R rods which according to factory should be changed to later ...2R style whenever rod bolts are opened.
Below '95 MY cars have all the updates factory made. They were made between 08/94-08/95.
Total GTS production were 2887 cars over four model years if above VIN sequences are correct. Engines used in them can be split into three different types.
1. '92 MY
- Block mounted with studs
- ...1R rods
- 1st style pistons
- 1st style piston rings
- Simple crank breather
- Number of cars using these engines is 1043
2. '93 MY to early '94 MY made before September 14th 1993
- Block mounted with bolts
- ...1R rods
- 2st style pistons
- 2st style piston rings
- Complex crank breather
- Number of cars using these is 742 '93 MY made and maybe little under 1/5 th of '94 MY production which would be something like 100 first '94 MY cars out of 626 made. This means something like 80 first ROW and 20 first US '94 MY models used ...1R rods.
3. '94 MY strarting from September 14th 1993 to end of '95 MY
- Block mounted with bolts
- ...2R rods
- 2st style pistons
- 2st style piston rings
- Complex crank breather
- Number of cars using these are 500+ late '94 MY and 476 '95 MY.
Then there are possible changes done to late '95 MY engines which are not documented anywhere.
AFAIK both '92 MY and '93-95 MY piston styles had all eight oil holes blocked and have extra oil collector groove in skirt below oil ring which isn't used in any other Porsche piston, certainly not in 928 and 944 series engines. Only difference in two piston styles is how thick certain areas in skirt is. Both styles should weight the same within allowed tolerance.
US VIN used '93 MY P VIN as sales were so slow that PCNA expected some cars to remain unsold so long that they would appear old to buyers if they had '92 MY VIN. US low allows use of next year VIN starting from January 1st of previous year. These 88 cars can be identified with M718 option code. AFAIK they should have '92 MY engine in them.
Automatic gearbox diff lost MY digit from number sequence in '92 MY but at least early '92 MY manual gearboxes still had N in number to identify MY.
Code:
MY Model Market Smallest VIN Largest VIN Qty Total --------------------------------------------------------------- 92 928 GTS ROW WP0ZZZ92ZNS800061 - 801015 955 93.E 928 GTS USA+CAN WP0AA292_PS815061 - 815148 88 1043
Some time after January 1st 1993 US VIN series where changed to '94 MY R VIN as sales were so slow that PCNA expected some cars to remain unsold so long that they would appear old to buyers if they had '93 MY VIN. These 19 cars can be identified with M718 option code. AFAIK they should have '93 MY engine in them.
Code:
MY Model Market Smallest VIN Largest VIN Qty Total --------------------------------------------------------------- 93 928 GTS ROW WP0ZZZ92ZPS800061 - 800681 621 93.L 928 GTS USA+CAN WP0AA292_PS820061 - 820162 102 94.E 928 GTS USA+CAN WP0AA292_RS820061 - 820079 19 742
In fall '93 connecting rods were chabged to stronger ...2R casting number design. Change date on production line was September 14th 1993. I can't recall if its known what engine numbers were first M28/49 (5sp) and M28/50 (automatic) engine to receive ...2R rods. In any case this means some early '94 MY cars still got ...1R rods which according to factory should be changed to later ...2R style whenever rod bolts are opened.
Code:
MY Model Market Smallest VIN Largest VIN Qty Total --------------------------------------------------------------- 94 928 GTS ROW WP0ZZZ92ZRS800061 - 800566 506 94.L 928 GTS USA+CAN WP0AA292_RS820080 - 820199 120 626
Code:
MY Model Market Smallest VIN Largest VIN Qty Total
---------------------------------------------------------------
95 928 GTS ROW WP0ZZZ92ZSS800061 - 800459 399
928 GTS USA+CAN WP0AA292_SS820061 - 820137 77 476
1. '92 MY
- Block mounted with studs
- ...1R rods
- 1st style pistons
- 1st style piston rings
- Simple crank breather
- Number of cars using these engines is 1043
2. '93 MY to early '94 MY made before September 14th 1993
- Block mounted with bolts
- ...1R rods
- 2st style pistons
- 2st style piston rings
- Complex crank breather
- Number of cars using these is 742 '93 MY made and maybe little under 1/5 th of '94 MY production which would be something like 100 first '94 MY cars out of 626 made. This means something like 80 first ROW and 20 first US '94 MY models used ...1R rods.
3. '94 MY strarting from September 14th 1993 to end of '95 MY
- Block mounted with bolts
- ...2R rods
- 2st style pistons
- 2st style piston rings
- Complex crank breather
- Number of cars using these are 500+ late '94 MY and 476 '95 MY.
Then there are possible changes done to late '95 MY engines which are not documented anywhere.
AFAIK both '92 MY and '93-95 MY piston styles had all eight oil holes blocked and have extra oil collector groove in skirt below oil ring which isn't used in any other Porsche piston, certainly not in 928 and 944 series engines. Only difference in two piston styles is how thick certain areas in skirt is. Both styles should weight the same within allowed tolerance.
THIS IS A FANTASTIC POST!
Can you, or I or anyone quote this in a new thread titles something like "GTS engine changes through model years"
Having the information thats in this post in a properly titled thread (as obviously this covers more then just piston drilling) would be huge for those looking to search for this at anytime in the future.
This answers all mechanical changes throughout the GTS production run.
Thanks guys!
02-08-2009, 02:12 PM
#33
Former Sponsor
Do the pistons in the stroker have the drilled holes? 968 pistons. Do you think the JE pistons have the holes as well. mine actually is using more oil than the holbert machine. Im doing more street driving and less all out tesing on the freeway now, so ill see how many miles i get for a quart. It seems to be near 1 quart per tank as it stands now. Is this due to holes in the pistons or ring design? S4 had the holes? sorry for all the questions. just curious.
mk
mk
Those holes allow the oil that the oil control ring wipes off of the cylinder, to go somewhere. Without them, the oil is trapped and can't go anywhere., except up into the other rings. This is why the GTS engines ping and form excessive oil deposits on the pistons and in the combustion chambers.
I drill the holes just like the holes in the 5.0 pistons. It isn't rocket science. All you need is the proper size drill and a drill press to keep the holes straight. Something to hold the piston helps...but his could be made from a block of wood, or two.
Ryan: If you really want a GTS piston, PM me your address and I'll send you one.
02-08-2009, 02:17 PM
#34
Nordschleife Master
Theo thanks for the pics, i can see the "blind holes" under the oil rings. I obviously assume that had i looked at them up close I would see that they are sealed. Makes drilling them fairly easy I would imagine.
Also about the differences between the early and late pistons. Erkka you mention that the only real difference in pistons are the location of the rings in relation to one another. This makes me think that although the piston design was changed, is it possible that the early pistons are in no way inferior compared to the later ones when 4-8 holes have been drilled out.
I mean the piston ring location (along with ring design) was changed by porsche to alleviate oil consumption. Or rather the ring design is likely what was changed, but in order to do that they must have played with the actual ring location relative to the piston itself.
SO....being that the later cars still had oil consumption issues, can we assume that both pistons are really of equal quality, but the real solution to oil consumption seems to be removal of the pistons and drilling of the holes?
Also about the differences between the early and late pistons. Erkka you mention that the only real difference in pistons are the location of the rings in relation to one another. This makes me think that although the piston design was changed, is it possible that the early pistons are in no way inferior compared to the later ones when 4-8 holes have been drilled out.
I mean the piston ring location (along with ring design) was changed by porsche to alleviate oil consumption. Or rather the ring design is likely what was changed, but in order to do that they must have played with the actual ring location relative to the piston itself.
SO....being that the later cars still had oil consumption issues, can we assume that both pistons are really of equal quality, but the real solution to oil consumption seems to be removal of the pistons and drilling of the holes?
02-08-2009, 02:23 PM
#35
Former Sponsor
Theo thanks for the pics, i can see the "blind holes" under the oil rings. I obviously assume that had i looked at them up close I would see that they are sealed. Makes drilling them fairly easy I would imagine.
Also about the differences between the early and late pistons. Erkka you mention that the only real difference in pistons are the location of the rings in relation to one another. This makes me think that although the piston design was changed, is it possible that the early pistons are in no way inferior compared to the later ones when 4-8 holes have been drilled out.
I mean the piston ring location (along with ring design) was changed by porsche to alleviate oil consumption. Or rather the ring design is likely what was changed, but in order to do that they must have played with the actual ring location relative to the piston itself.
SO....being that the later cars still had oil consumption issues, can we assume that both pistons are really of equal quality, but the real solution to oil consumption seems to be removal of the pistons and drilling of the holes?
Also about the differences between the early and late pistons. Erkka you mention that the only real difference in pistons are the location of the rings in relation to one another. This makes me think that although the piston design was changed, is it possible that the early pistons are in no way inferior compared to the later ones when 4-8 holes have been drilled out.
I mean the piston ring location (along with ring design) was changed by porsche to alleviate oil consumption. Or rather the ring design is likely what was changed, but in order to do that they must have played with the actual ring location relative to the piston itself.
SO....being that the later cars still had oil consumption issues, can we assume that both pistons are really of equal quality, but the real solution to oil consumption seems to be removal of the pistons and drilling of the holes?
02-08-2009, 02:23 PM
#36
Nordschleife Master
I've never seen another piston that doesn't have the drain back holes, from the oil contol rings. I've shown the GTS pistons to almost every "piston" guy that I've ever ran into and they all just shake their heads and say, "Well, that won't work."
Those holes allow the oil that the oil control ring wipes off of the cylinder, to go somewhere. Without them, the oil is trapped and can't go anywhere., except up into the other rings. This is why the GTS engines ping and form excessive oil deposits on the pistons and in the combustion chambers.
I drill the holes just like the holes in the 5.0 pistons. It isn't rocket science. All you need is the proper size drill and a drill press to keep the holes straight. Something to hold the piston helps...but his could be made from a block of wood, or two.
Ryan: If you really want a GTS piston, PM me your address and I'll send you one.
Those holes allow the oil that the oil control ring wipes off of the cylinder, to go somewhere. Without them, the oil is trapped and can't go anywhere., except up into the other rings. This is why the GTS engines ping and form excessive oil deposits on the pistons and in the combustion chambers.
I drill the holes just like the holes in the 5.0 pistons. It isn't rocket science. All you need is the proper size drill and a drill press to keep the holes straight. Something to hold the piston helps...but his could be made from a block of wood, or two.
Ryan: If you really want a GTS piston, PM me your address and I'll send you one.
Great information, and i will take you up on your offer.
It seems to me this relatively simple mod in itself (obviously you have to tear an engine down to do this though) would have a huge impact on the overall running condition of all GTS engines.
02-08-2009, 02:30 PM
#37
Former Sponsor
This is how it goes when dealing with a German....who will never admit that they did anything wrong.
They will insist that the real problem is that the oil control rings are in the wrong place in relationship to the other rings due to some harmonic or frequency that they have found, previously unknown to all others. They will redesign the piston, moving the rings, a bit. The oil drain back holes will magically appear in the redesign, but will not be talked about. All parties will know what the problem was and what the solution was, but they will never talk about it. It's the German way.
They will insist that the real problem is that the oil control rings are in the wrong place in relationship to the other rings due to some harmonic or frequency that they have found, previously unknown to all others. They will redesign the piston, moving the rings, a bit. The oil drain back holes will magically appear in the redesign, but will not be talked about. All parties will know what the problem was and what the solution was, but they will never talk about it. It's the German way.
02-08-2009, 02:33 PM
#38
Nordschleife Master
Are there still different ring PN's for early and late GTS's?
Or did Porsche just supercede all rings to the later part number? In which case this would prove what little effect the ring land location has to the overall design
I will check the PET now actually (EDIT: The only difference i see in rings is for overbore or tolerance group, there is no distinction for early or late rings)
Q: if i was going to rering one of these, would i still be fine with S4 rings, or are there OEM Goetz rings for the GTS?
Or did Porsche just supercede all rings to the later part number? In which case this would prove what little effect the ring land location has to the overall design
I will check the PET now actually (EDIT: The only difference i see in rings is for overbore or tolerance group, there is no distinction for early or late rings)
Q: if i was going to rering one of these, would i still be fine with S4 rings, or are there OEM Goetz rings for the GTS?
02-08-2009, 02:37 PM
#39
Former Sponsor
Yes, it fixes them....there never has been a question of that. Combine that with the updated connecting rod and you have a great car. They no longer ping and the oil consumption becomes normal. Turns a questionable running car into the car that everyone thinks it should be. Makes the GTS a better car than the GT models. If you have an automatic and you fix the thrust bearing issue, at the same time...it is also now a better car than the earlier models.
02-08-2009, 04:04 PM
#40
Rennlist Member
02-08-2009, 04:18 PM
#41
Nordschleife Master
02-08-2009, 05:19 PM
#42
Addict
Rennlist Member
Rennlist Member
Numbers also shows ratio of 5sp vs automatics at the time. 25% sounds little high for ROW cars for two earlier years as production numbers were higher then. There were very likely some 500-600 5sp cars among 2481 ROW models made leaving 1900-2000 automatics. 5sp US models made was 167 cars vs 239 automatics. This means total number of 5sp GTS is very likely between 600-750 cars.
02-09-2009, 08:25 AM
#43
Rennlist Member
Question?
I have the later style pistons - BUT:
- they have cut-outs for 39mm intake valves
- they are made by Kolbenschmidt, usually its Mahle
- they have 4 blind holes (the ones closest to the pin) and 4 holes drilled through
- the engine has been sleeved by Porsche with some material, which is not alusil - remarkably different from the block material. Seems more like steel
- Material code does not match what Porsche has in the literature
What have I got - experiMental engine?
- they have cut-outs for 39mm intake valves
- they are made by Kolbenschmidt, usually its Mahle
- they have 4 blind holes (the ones closest to the pin) and 4 holes drilled through
- the engine has been sleeved by Porsche with some material, which is not alusil - remarkably different from the block material. Seems more like steel
- Material code does not match what Porsche has in the literature
What have I got - experiMental engine?
02-09-2009, 10:18 AM
#44
Rennlist Member
Yes, it fixes them....there never has been a question of that. Combine that with the updated connecting rod and you have a great car. They no longer ping and the oil consumption becomes normal. Turns a questionable running car into the car that everyone thinks it should be. Makes the GTS a better car than the GT models. If you have an automatic and you fix the thrust bearing issue, at the same time...it is also now a better car than the earlier models.
02-09-2009, 10:21 AM
#45
Rennlist Member
It does. I might have seen same info before but didn't remember it and could not find numbers with quick search. Are you sure second number is correct? I think it should be 81R05097. Then it would be in line with previous MY automatic engine numbers. In anycase 32 manual and 96 automatic gearbox engines were made for '94 MY before rods were changed to ...2R style. This is little more than I expected but not far off.
Numbers also shows ratio of 5sp vs automatics at the time. 25% sounds little high for ROW cars for two earlier years as production numbers were higher then. There were very likely some 500-600 5sp cars among 2481 ROW models made leaving 1900-2000 automatics. 5sp US models made was 167 cars vs 239 automatics. This means total number of 5sp GTS is very likely between 600-750 cars.
Numbers also shows ratio of 5sp vs automatics at the time. 25% sounds little high for ROW cars for two earlier years as production numbers were higher then. There were very likely some 500-600 5sp cars among 2481 ROW models made leaving 1900-2000 automatics. 5sp US models made was 167 cars vs 239 automatics. This means total number of 5sp GTS is very likely between 600-750 cars.