What are the advantages/disadvantages of slipper skirt pistons. I know they are lighter, but are they practical on a daily driver or are the mainly for race applications. I have heard the are noisy. Why is that?
Thanks
Slipper Skirt Vs non-slipper
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Muffler Mike
- Posts: 3186
- Joined: Tue Feb 20, 2001 12:01 am
I think for daily driver there is no subsitute for the cima/mahle. they use a material that does not expand like the higher end forged pistons. so they can run a much tighter clearance.
the nice thing about the slipper skirt or what ever they call them is it does put the side walls that hold the wrist pin closer together, witch helps support the middle of the crown, and makes for a shorter wrist pin as well. But typically done in an alloy that is stronger but needs more room for expansion. thus the noise or splap can arise.
NOW i dont know how the AA cast pistons might work. I would assume they can run a tigher tolerance like a cima, but have the design of a slipper.
Weather the cima is a true forge or not is up for debate but they have taken some major abuse in the past.
At least this is how i understand it.
the nice thing about the slipper skirt or what ever they call them is it does put the side walls that hold the wrist pin closer together, witch helps support the middle of the crown, and makes for a shorter wrist pin as well. But typically done in an alloy that is stronger but needs more room for expansion. thus the noise or splap can arise.
NOW i dont know how the AA cast pistons might work. I would assume they can run a tigher tolerance like a cima, but have the design of a slipper.
Weather the cima is a true forge or not is up for debate but they have taken some major abuse in the past.
At least this is how i understand it.
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cnavarro
- Posts: 455
- Joined: Fri Nov 02, 2001 12:01 am
JE and others do have high-silicon forgings for reduced expansion, but i'd have to agree with you Mike that the mahle pistons are the best match to the cast iron cylinders. Just to give you an idea, I once set up a set of Nickies with the factory recommended clearance with the mahles and ended up having to strip and replate the cylinders down to .001 clearance to eliminate the piston slap under full load. Knowing that, they expand almost nothing and are the perfect match for the original cast iron cylinders. Just like the mahles are best suited to the original cylinders, the high-strength forgings are best suited to our cylinders. Any deviation from the norm and you have to try the waters to find what works best without scuffing or piston slap.
Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance
Charles Navarro
LN Engineering
http://www.LNengineering.com
Aircooled Precision Performance
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funkSoulP
- Posts: 88
- Joined: Mon Sep 12, 2005 6:13 am
I heard about an interesting trick how to get rid of excessive slap a while ago.
A guy drag racing a Harley used teflon, or some other high temp plastics, "buttons" in the skirt. Not the ones used to hold the pin in place, but similar in shape just smaller machined into the skirt. When cold the buttons supported the piston and when hot the plastic is soft enough not to jam the piston. The mechanic claimed that they raced one season using just one piston instead of four or five without the buttons. I forgot to ask though if they replaced the buttons between runs or used the same all season long.
I can imagine that it may work in a dragster where cooling is insufficient (too cold in the start, too hot in the end), but have no clue if it will make any sense in a street car. Anyone know/seen/have tested such plastic buttons?
A guy drag racing a Harley used teflon, or some other high temp plastics, "buttons" in the skirt. Not the ones used to hold the pin in place, but similar in shape just smaller machined into the skirt. When cold the buttons supported the piston and when hot the plastic is soft enough not to jam the piston. The mechanic claimed that they raced one season using just one piston instead of four or five without the buttons. I forgot to ask though if they replaced the buttons between runs or used the same all season long.
I can imagine that it may work in a dragster where cooling is insufficient (too cold in the start, too hot in the end), but have no clue if it will make any sense in a street car. Anyone know/seen/have tested such plastic buttons?