Piston Drillings?
Discussion
I would think they are used to 'clean' up the bores..
The air pressure under the piston on the down stroke - some air will vent to these holes and agitate any oil on the cylinder walls making the oil scraper ring have an easier time lifting it off the surface.
Then again - maybe there are just there to look pretty
The air pressure under the piston on the down stroke - some air will vent to these holes and agitate any oil on the cylinder walls making the oil scraper ring have an easier time lifting it off the surface.
Then again - maybe there are just there to look pretty
grahambell said:
Some older piston designs used to use slots which would crack at the ends, which could eventually lead to a big chuck of piston skirt dropping off. Using a series of holes instead makes for a stronger piston.
Those are thermal slots to keep the heat in the crown away from the skirt thus allowing a much tighter piston to bore clearance.
My guess is that the drilling help on the downstroke when there's oil building up below the scraper rings. Probably doesn't work as I've never seen anybody else do it. Or, the Essesx has it's own oiling problems, like to much splash and no windage tray
Boosted.
These look like cosworth pistons to me, the vents / holes are designed to allow the oil to pass through from the oil groove as its scraped off the bore by the oil control ring. If you have no vents or slots then the oil has nowhere to go and the scraper doesn't work so well, we tried deleting them on the F1 engine and the oil consumption was tripled.
Matt
Matt
The piston is a little narrowerfrom the bottom of the oil control ring down to halfway down the drilled holes. The idea was that the oil would be scraped off the bores and could be pushd inwards through the holes. Seen it on other engines but don't know if it really works. Like the theory though.
SuPaSpArK said:
Just wondering if anybody knows the reason for these drillings just below the oil ring. The pistons all look like they have been balanced and modified
post your thoughts cos I'd like to use them.
Supes.
post your thoughts cos I'd like to use them.
Supes.
They are absolutely standard and there's not a piston made that doesn't have them. They allow the oil scraped off the bores by the oil ring to pass to the inside of the piston and run back to the sump. Sometimes the holes, or it may be a slot, will be in the oil ring groove itself and sometimes just below it.
Pumaracing said:
SuPaSpArK said:
Just wondering if anybody knows the reason for these drillings just below the oil ring. The pistons all look like they have been balanced and modified
post your thoughts cos I'd like to use them.
Supes.
post your thoughts cos I'd like to use them.
Supes.
They are absolutely standard and there's not a piston made that doesn't have them.
You're right about the function but plenty of pistons are made without the oil drillings. It's just that 'proper' pistons tend to have them
Boosted.
Pumaracing said:
SuPaSpArK said:
Just wondering if anybody knows the reason for these drillings just below the oil ring. The pistons all look like they have been balanced and modified
post your thoughts cos I'd like to use them.
Supes.
post your thoughts cos I'd like to use them.
Supes.
They are absolutely standard and there's not a piston made that doesn't have them. They allow the oil scraped off the bores by the oil ring to pass to the inside of the piston and run back to the sump. Sometimes the holes, or it may be a slot, will be in the oil ring groove itself and sometimes just below it.
Puma - welcome to PH.
I'm a real fan of your no nonsence web site :
www.pumaracing.co.uk/
Some great stuff on there .. especially the types of customer
rev-erend said:
Pumaracing said:
SuPaSpArK said:
Just wondering if anybody knows the reason for these drillings just below the oil ring. The pistons all look like they have been balanced and modified
post your thoughts cos I'd like to use them.
Supes.
post your thoughts cos I'd like to use them.
Supes.
They are absolutely standard and there's not a piston made that doesn't have them. They allow the oil scraped off the bores by the oil ring to pass to the inside of the piston and run back to the sump. Sometimes the holes, or it may be a slot, will be in the oil ring groove itself and sometimes just below it.
Puma - welcome to PH.
I'm a real fan of your no nonsence web site :
www.pumaracing.co.uk/
Some great stuff on there .. especially the types of customer
Yes, that's a good read, made me chortle! I've come across a few type 2's. Usually they email you and take up your time that way. It's a way to vet them and saves to many consultations in person.
Boosted.
Boosted LS1 said:
You're right about the function but plenty of pistons are made without the oil drillings. It's just that 'proper' pistons tend to have them
Boosted.
Boosted.
In 30 years of building engines I haven't seen a piston without oil drains but by all means give me a reference or pic of one that doesn't. On most production pistons they are behind the oil ring as I said above. This is often done by casting the piston with an undercut in the right place so that when the oil ring groove is machined it breaks through to leave a slot for the oil to go through. This weakens the ring land area a bit but the design takes this into account. It saves a time consuming drilling op which would put the cost up.
On forged pistons you can't produce undercuts inside the piston or the forging boss wouldn't pull back out of the mould so the drains have to be drilled. Again this will be either inside the ring groove, below it or even 50/50 where the hole intersects the bottom of the ring groove.
If a piston had no oil drains there would be no way for the oil that got onto the bore walls to be replaced with fresh oil. The same oil would go up and down until it turned into charcoal, the bores wore out and the piston seized into place. Clearly not a cutting edge design feature. However, reference me any piston without them and we'll chat again.
Puma, please read my reply again.
Supes was referring to oil drillings (not slots) and in my reply to you at 09.36 I was also referring to drillings, commenting to the effect that's what you get with proper pistons. I wasn't passing comment on the need for oil slots, grooves, channels or whatever as didn't need to.
No doubt we'll chat sometime.
Boosted.
Supes was referring to oil drillings (not slots) and in my reply to you at 09.36 I was also referring to drillings, commenting to the effect that's what you get with proper pistons. I wasn't passing comment on the need for oil slots, grooves, channels or whatever as didn't need to.
No doubt we'll chat sometime.
Boosted.
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