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How should correctly exposed Alusil cylinder look like? I got my cylinder back from shop, they say everything was done to exact spec, but better safe than sorrow..
This is how my cylinder looks like, is this dull enough, I kind of think it is still too shiny?
Dont find any relevant pictures of cylinders that worked.
From samples found in water passages, it looks like they used two different lapping compounds, green and gray. Based on web search, green should be diamond lapping paste, gray looks a lot like AN-30, correct?
Hard to tell exactly from pictures. I remember when looking at the cylinder walls when the block came back and it looked like a perfect running motor that had just came apart. Really no sheen and no evidence of machining. Here's a pic but again the picture is deceiving in that it looks shiny.
As long as the shop used the AN30 and correct honing oil I think You're going to have to trust they got it right. What pistons,rings and clearance are you using ?
How should correctly exposed Alusil cylinder look like? I got my cylinder back from shop, they say everything was done to exact spec, but better safe than sorrow..
This is how my cylinder looks like, is this dull enough, I kind of think it is still too shiny?
Dont find any relevant pictures of cylinders that worked.
From samples found in water passages, it looks like they used two different lapping compounds, green and gray. Based on web search, green should be diamond lapping paste, gray looks a lot like AN-30, correct?
..]
I don't think you can check it out according to a picture. Here on page 68 of 100 (Reconditioning of Aluminium Engine Blocks by Kolbenschmidt PDF) they explain two important factors which are essential:
...The quality of a finished aluminium silicon surface depends essentially on two important factors: the depth of the exposure of the silicon crystals that has been achieved and the degree of destruction of the crystals. The depth of the exposure ensures that sufficient oil can get between the silicon crystals to lubricate the piston rings and the piston. Remark: the thickness of the film of lubricant on the cylinder surface can be measured with modern instruments. It is 1–2 μm. Depth of the exposure
The depth of the exposure can be measured exactly only with a roughness tester with the appropriate evaluation software. ....
Apart from that the whole brochure is very interesting.
By the way I'm working on the same project like you. The engine to work on is already on the engine stand
gpr8er: thanks, it looks very much like your cylinder on the picture. What ring gap & piston to wall clearance have you used? Are you happy with the outcome?
blade7:
I bought these, Andial/Mahle ferrostan 104.5mm with mahle rings.:
H.F.B.: I know, but profilometer costs €2k and I have no clue where to find it. Is your engine already assembled? Same 104.5mm setup?
I now have everything to assemble the engine, but I want to be 100% positive that pistons/cylinders will work as supposed to.
My engine is still to be disassembled and then inspected. I'm not sure, if I really have get the cylinders honed. The engine is a US M44/12 (automatic) and according to the previous owner only 70214 miles on the engine. Porsche claims that the Alusil cylinders should at least be good for 250 000 km. So I hope I could save this job and that there is just the need for new pistons. The 3.0l crank is already in stock and waiting to be installed.
Did you buy Pauter rods? Where did you buy them?
Yes I remember now. Did Mahle specify that clearance ? I think Wossner suggest 0.08mm for their pistons.
Wossner has different expansion rate.
Workshop manual suggest (if I remember correctly) new engine clearance with Mahle pistons from 0.018 to 0.032, and service limit is 0.080. I fugured 0.050 should be the safe side of things.
Originally Posted by H.F.B.
My engine is still to be disassembled and then inspected. I'm not sure, if I really have get the cylinders honed. The engine is a US M44/12 (automatic) and according to the previous owner only 70214 miles on the engine. Porsche claims that the Alusil cylinders should at least be good for 250 000 km. So I hope I could save this job and that there is just the need for new pistons. The 3.0l crank is already in stock and waiting to be installed.
Did you buy Pauter rods? Where did you buy them?
Cylinders should be good with matching pistons. If you install new pistons, your piston to wall clearance may vary . Even more worrying is edge in cylinder where top piston ring stops. If you change the type of pistons and stroke, your top ring might ride over that edge and that would probably destroy at least piston ring.
Workshop manual suggest (if I remember correctly) new engine clearance with Mahle pistons from 0.018 to 0.032, and service limit is 0.080. I fugured 0.050 should be the safe side of things.
I hope everything works well. I'm not sure if clearances in the workshop manual apply to a forged piston in a 104mm turbocharged block though.
Porsche used the same workshop manual clearances on 951 that has forged mahle pistons with same piston material & coating. Considering that and few mm wider piston, I think. 050 should be good.
HFB, looks like you are tearing down a 2.7, can you PLEASE do me a favor and let me know the part number on the camshaft?
I've been searching and searching and can't seem to find an answer as to exactly what the 89 cars used for a camshaft.
Yep, will do on Saturday. I'm interested as well. According to Porsche the 2.7l camshaft is different from the 2.5l camshaft.
2.7 --> 944.105.155.10R
2.5 --> 944.105.155.09R
As far as I know the revision was related to the intake lobe.
I'll post photos of the two cams, so we can see the change.
03-02-2015, 07:07 AM
Alusil Cylinder, how should it look?
