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Discussion Starter #1
I noticed that the guys on this forum running low compression pistons are also sleeving their blocks. Is this something that is absolutely necessary or something done to sleep better at night? At what point does it become a necessity?

thanks for the feedback!
 

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I think the main necessity for sleeving the block, once you go for low compression pistons, is due to the fact that low compression pistons are not designed to work with the Alusil coating of our stock bores.

Second point is that if you go for forced induction then with our inherently (over bored) narrow inter cylinder wall thickness, you are very limited in terms of absolute boost pressure. By sleeving we can increase the inter wall thickness thus allowing one to run much higher levels of boost.

Thirdly I think with a sleeved block you are left with an overall much stronger engine block that will be less likely to crack with extreme power setups.
 

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The real question is how much do the sleeves weigh?

It's not so much that you are increasing the wall thickness, but you are making the walls out of a stronger material.

You are also changing one of the things that makes the s62 unique ;)
 

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Discussion Starter #4 (Edited)
The real question is how much do the sleeves weigh?
Already on top of that one! Assuming 1mm thick and 200mm tall, 8 of the sleeves weigh 3.7kgs, net impact (less the aluminum removed) is 2.6kgs. ;)

I have mixed feelings on the sleeves: you're right it does render the whole alusil casting moot. On the other hand, the block is going to get sleeved eventually, right? And it does make finding aftermarket pistons much simpler.

Regarding making the block stronger: is that really the case? Narrowing the "connecting" alusil walls between cylinders down to 2mm would reduce the block strength, no? Sure the cylinder walls are stronger and can better handle higher cylinder pressures, but they don't help block stiffness and should make block twist worse, right?

thanks again for the feedback.
 

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I have become ambivalent about sleeving. It definitely enhances the strength of the cylinders and facilitates piston selection. On the other hand, it significantly increases the heat retained by the engine, and things can go wrong with the sleeves (slipping, twisting, etc.). Dinan sleeves none of their blocks and uses stock head bolts and stock main bolts--yes, even on the Daytona prototype engines and on their S3 E39 setups. On the other hand, the standard VAC/D/A Automotive formula for an FI S62--Darton sleeves, CP pistons, Carillo or Arrow rods--is tried and true. The NA build I am doing for Sam will follow Dinan's formula, but I am hesitant to do so on a serious FI build. I have seen what too much cylinder pressure can do to a stock block--burning right through the cylinder walls as if they were never there. (That block, BTw, was subsequently sleeved and is running in a big power FI setup today). One definitely can have the stock cylinder walls re coated and honed (E.g., US Chrome does it) and buy Mahle aftermarket pistons designed to work with the coating. Maybe one of these days, I will try that rout with an FI setup. For NA, I absolutely would NOT sleeve.

--Peter
 

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I would only use sleeves if you are increasing the size of the bore, especially if the cylinder walls can be re honed properly and there are rings sets and pistons that work with the stock bore material.

Blocks are sleeved all of the time (the vast majority of aluminum blocks use sleeves from the factory) and there is no magic to it, just solid machine work. I think you folks run into trouble when looking for the magic solution, as usual ;)
 

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Blocks are sleeved all of the time (the vast majority of aluminum blocks use sleeves from the factory) and there is no magic to it, just solid machine work. I think you folks run into trouble when looking for the magic solution, as usual ;)
I like magic though! I actually think that's why some people do NOT get into DIYing: they like NOT knowing the ins and outs and instead just enjoy marveling at the performance, as if it were accomplished by magic. I truly understand that feeling. But it is not me.

Sorry for going OT.

--Peter
 

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Discussion Starter #8
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If you are going much above 600hp, sleeves are a good idea.

Been running a sleeved motor since 2006 without any problems.
 

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One definitely can have the stock cylinder walls re coated and honed (E.g., US Chrome does it) and buy Mahle aftermarket pistons designed to work with the coating.
I talked to US Chrome about this. They says that CP will also make pistons and supply rings that are compatible with their Nikasil Coating. They say the benefits for a NA engine would be much better heat transfer than sleeves, the ability to run tighter tolerances with pistons and better wear resistance of Nikasil than a steel liner. I asked them specifically if they had done any BMW engines before and their response was "The v8? Yeah, we have done tons of them". Its also a common coating for Porsche so there should be some knowledge out there.
 
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I talked to US Chrome about this. They says that CP will also make pistons and supply rings that are compatible with their Nikasil Coating. They say the benefits for a NA engine would be much better heat transfer than sleeves, the ability to run tighter tolerances with pistons and better wear resistance of Nikasil than a steel liner. I asked them specifically if they had done any BMW engines before and their response was "The v8? Yeah, we have done tons of them". Its also a common coating for Porsche so there should be some knowledge out there.
Thanks. There is a US Chrome coated block with 70k on it on eBay right now for the absurd price of $3200. Apparently, the coating and honing process runs about $1-1.5k.

--Peter
 

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Thanks. There is a US Chrome coated block with 70k on it on eBay right now for the absurd price of $3200. Apparently, the coating and honing process runs about $1-1.5k.

--Peter

Time to make an offer :)
 

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ill be using the Raikku formula in my NA build and it will make proper power and will not blow up
 

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Discussion Starter #15
I have seen what too much cylinder pressure can do to a stock block--burning right through the cylinder walls as if they were never there. (That block, BTw, was subsequently sleeved and is running in a big power FI setup today).
Just wondering: was that due to detonation or normal operating cylinder pressure? I'll try some calculations in Solidworks to estimate deformation (just as soon as I'm through with the holiday festivities).
 

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Just wondering: was that due to detonation or normal operating cylinder pressure? I'll try some calculations in Solidworks to estimate deformation (just as soon as I'm through with the holiday festivities).
Don't know, John. Suspicion is that the car was running too much boost for a stock bottom end and stock compression. Burned right through the wall between cylinders 6 and 7, I believe.

--Peter
 

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Discussion Starter #17
Some numbers to consider:

Running an Eaton TVS R1900 on the S62, I get a max cylinder pressure of around 11MPa according to Engine Analyzer Pro. That translates to a radial tension in the thinnest part of the cylinder wall of 11MPa*94mm cylinder inner diameter/(2*4mm wall thickness)=130MPa. According to Matweb, Alusil (A390) with T6 heat treatment has a fatigue strength of 115MPa (at 5*10^8 cycles). However, that is with full reversal of the stress (one cycle is 115MPa compression followed by 115MPa tension) and is (I think) measured at room temperature. I found a pdf on the Kolbenschmidt web site that shows fatigue strength to be about 50% higher when only tension is cycled (no compression). This is for their high-pressure cast hypereutectic aluminum, which they state has nearly the same strength properties as Alusil, which is low pressure cast.

So two questions:

1) does anyone know the heat treatment done to our blocks?
2) anyone have any high temperature strength numbers for Alusil? I haven't found anything, but my understanding is that Alusil has good high temperature properties.

Bottom line is, I think I'll be fine without iron liners at the volumetric efficiencies that I would be looking at (good for 550ftlbs of torque). 5*10^8 cycles works out to running the engine at WOT and 8k rpm continuously for 7 years!
 

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A couple of things I've run into with regard to sleeving blocks:



  • Running a smaller cylinder bore affects the flow relationship between the cylinder wall and valves. Sometimes this would affect absolute flow, sometimes it would affect homogenation effeciency of mixture preparation prior to ignition event. And further, this "could" affect burn-speed and pattern.
  • Heat transfer into the block through the cylinder is not desired. If one was entirely focused on this, you'd actually look at using an exotic liner material like stainless. So along those lines, because most of the combustion heat is tranfered out of the combustion chamber through the head, this point is moot. As long as clearances are maintained through the block, and oil is at the right viscosity for rate of rotation, you in theory could run the block at any temperature.
  • Sleeving sometimes intrudes into the oil squirter distribution galleries, or can affect the placement and angle of spray. This all depends on the height of the liner, and it's circumference.
  • Sleeving gives you the oportunity to use coatings that are optimized for specific material application. One of the main reasons why Capricorn recommends sleeving, is so that they are able to reliably apply cylinder wall coatings. While steel may be uniform in appearance, the specific metalurgy may deviate from the top to the bottom of the liner. This affects the grain structure, which a coating may be optimzed for. I'm told that to get a consistent coating, you need a consistent base material.
  • In addition to coatings, there are now very specific laser etching processes that can be performed on the cylinder bore where the rings reach TDC. The purpose is to modify the clearance and friction characteristics for ring force reversal events.

So in short, liners also give the ability to add technology to the friction surface, at the potential cost of flow changes around the valves.

I however have no practical experience with this on the S62, so you may all consider me to be a troll if you like. :p
 
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