best way to oil cool pistons?

[goose]

I've been considering oil cooling for pistons as a good way to keep pistons from melting under high temps, and have seen two different ways of accomplishing this. One is to drill a tunnel down the length of the rod and have it exit out the side of the small end of the rod, so that oil from the big end goes through the rod and sprays on the underside of the piston. The second way is to install oil jets in the block that point to the underside of the piston. Anybody have any pro/con for these two methods? The oil jet method seems to be fairly complex to me and also would only spray the piston well when it is near the bottom of the stroke...

[rumblefish360]

I have heard of some wild things before but this one takes it. If it's that hot inside that pistons are melting, I would think somethings wrong.
Wrong pistons, pistons to small for bore, to big for bore, bad timing, to much N0x, to much pressure from turbo/supercharger, and of course, not enuff fuel. Runnin lean up's the temp.
Keeping it cool with a good rad. hi flow pumps, correct mix of anti-frezze, good air flow through the rad, enuff rad? get a bigger one.
Keeping the oil cooler is a good idea. But that mod seems over the top. I never heard that one before.
Rods have oil passages in them allready.Right?

[goose]

This would be for a high boost and/or aircooled engine application. Porshe turbo aircooled motors use this, also so do many industrial turbo diesels. It's also used in motorcycles. The main problem in an aircooled or high boost engine is high combustion chamber temperatures causing preignition; one way to lower the chamber temp is to lower the compression ratio (VW's have CR's around 7:1). Cooling the chamber (usually with water passages in the head) is the other way that is used to lower chamber temps. Keeping the piston cool would be a good way to remove a lot of the heat from the combustion chamber (remember the piston is roughly half the chamber!). Your oil gets hotter, but you just run a bigger oil cooler... so anybody else have any experience with this?

[cuda66273]

Huh?
What are we talking about here??

I always drill a hole in the top of the small end of the rod to help lube the wrist pin, but this is a new one on me.....oil cool the piston??? Hummm gotta think some on this one.....

Goose,
Doug and I could send you one of our liitle white pills....seems to help some when the 60's flashbacks start...LOL

[Hittman55]

If forged pistons are good enough for NIRO METH 10,000 horse alchol engine they should not melt in you engine............LOL

People who say size dont matter..................have small engines!!!!

[brian phillips]

Seems everyone here thinks he is crazy. he's not. He appears to be concerned about high cylinder temps due to high cylinder pressures ( Lots of Booooossstttt!)

Actually "dodge aka mitsubishi" used this from 91 to 99 in their turbocharged stealths and 3000 GT-vr4. There are actually jets located to mist the underside of the pistons get keep deadly pinging and meltdowns from ocurring on the superheated piston tops.

If more people would never venture out into the strange and overlooked we would not be where we are today!

[pishta]

Isnt there a notch between the rod caps that does just this, spray up the pistons skirts to cool them? In a rebuild, it says these notches should face inward to oil the opposite cylinder (wall or skirt or bottom, or all three!)

[gmblows]

A tight quench area helps keep the piston cool.
And fuels with a high final boiling point help by
bringing liquid fuel to the piston to cool it.

[Hittman55]

Running a jet size or so bigger will help I was told for cooling heat down due to the cylinder pressure. This also helps you get away with a little more compression if spark knock, and detnation is a problem!

[rumblefish360]

If more people would never venture out into the strange and overlooked we would not be where we are today!

OK, I'll bite, where are we?
Seriously now. I have never heard this before. I don't think he's crazy, just seems to be overkill. Once I read his post, it makes a lot of sense. Now, just how to get this done is a mystery to me.
We have a spinning crank with those pesky rods in the way. I supose you'll have to use the gray matter and think off something. Like a fuel pump, pumping oil instead of fuel into a pair of spray bars mounted on the oil pan (?) Pump could be extrenal with a hole drilled into the pan. "T" the lines off to there respective cyl. banks and aim jets at pistons @ BDC.
Oil could come from an oil cooler. Something like a dry sump suction line could feed the cooler.
Hmmm. For thinking of this off the top of my head, it sound like it could work. Maybe I should write down my rambleings. They might start to think I'm not crazy.

[goose]

Rumblefish, your description is very close to what is actually installed in many engines. Usually a separate oil pump is used and feeds nozzles placed at the bottom of the bore, that are pointed such that the oil sprays the bottom of the piston. The pressure is high enough (usually ~60 PSI) that the oil hits the bottom side of the piston no matter where it is in the stroke. In doing more research after posting, I discovered that the dual pump with nozzle setup is a lot more effective than the oil-down-the-rod system. It's more work but it's worth it. Like I mentioned before, many factory engines are equipped like this... almost all of them turbo engines. Subaru WRX, Duramax, Porsche, Audi, Mercedes (both diesel and gas), also almost all the industrial turbodiesels have this system. After all, if you cool the top half of the combustion chamber why not cool the bottom half (the piston?) And what fails in an overboost situation? That's right, you melt the piston. I've never heard of melting a head... probably because it's watercooled! Even in aircooled engines (chainsaws, VW's, karts) piston damage is the only thing that happens; it is common to hole a piston in an aircooled engine but I've never seen a melted head.

[rumblefish360]

Cool man. Thanks for the lesson. Close to what they do huh? Maybe I should redirect my efforts towards automotive work instead of choo-choo trains.

[goose]

Actually in my searching I noticed a 2-stroke diesel for a diesel-electric application that advertised oil cooled pistons... and also a steam engine (for a locomotive) that used oil-cooled pistons... so you're covered no matter where you put your efforts!

[Tarrbabe]

The last time I heard of oil cooled pistons was in refrence to the old engines that used cast iron or steel pistons. In theory it makes sence, with the newer style pistons and the fact that they don't expand as much because of heat, the down side outweighs the upside. The upside is a cooler unit and the down side is you increase the problems of oil control in the engine (getting past the oil control rings) and also more drag due to the increased mass weight of the oil that must be moved each rev. of engine. The hardest test for an engine is a endurance race, such as 12-24 hours of Daytona or Nascar type engines. Do they use the oil cool set-up? I've never heard of it being used but then I guess I don't know everything about those type engines. (As usual, just thinking out loud.)

[JVMopar]

What about water misting the engine to cool the charge? Wouldn't that be easier?

[goose]

For racing the fuel is high enough octane that you probably don't worry about detonation as much as you would with pump gas, so oil cooling wouldn't be necessary. Also with a turbo engine the revs are usually lower (don't need to rev the snot out of it to get the HP figures) so the extra mass of the oil isn't as much of a worry as it would be with a non-turbo engine. I have heard of oil spray cooling sometimes causing higher oil consumption, but since it's commonly used in production turbo cars I would assume that the problem can't be very severe.
Water injection is a great way to cool the charged air and to also increase the knock resistance of the A/F mixture. The only drawback is that you have to have a supply of water, and keep refilling a tank. Not a big deal really, but just one more thing to hassle with. The oil cooled pistons would be a "hidden" feature, requiring no input or maintenance by the operator. Water injection also doesn't cool the combustion chamber, which is what the water circulating through your heads does and the oil on the piston would do. Two different ways of preventing knocking... both of them could be combined to make an engine that would last forever under really hellish boost!! Anybody up for trying them out?

[Tarrbabe]

Wouldn't oil spray defete the advantage of windage trays and baffels controling the oil to keep it out of the crank. rods and pistons, thus robbing hp?

[goose]

Windage trays etc. usually free up HP at the higher revs, but since a turbo engine doesn't need to rev high there shouldn't be excessive power lost due to the oil. It would become a definite problem at the higher revs though. That's probably why a lot of diesels use this, they don't rev much at all...

[HankL]

Bo Laws Peformance:

http://www.blp.com/index.htm

makes a 'jig' for small block mopars that sets in place and allows you to drill a tiny hole into the oil galleries to spray a jet of oil onto the bottom of the pistons at the center of the crown as the piston nears their lowest point close to the crank bearings.

He used to have a picture of it on his old 'rough' design webpage, but now the new 'slick' webpage design doesn't have that picture anymore.

Give them a call

BLP Products Inc
1015 W. Church Street
Orlando FL 32805
407-422-0394 Tech Line
800-624-1358 Order Line
407-422-2741 Fax Line
sales@blp.com

and they may still sell the drilling jigs. I seems like a good idea to me and the amount of oil used is small.

DC's 4.7 and 5.0 Mercedes V8 used in the ML series SUV's have oil jet cooling of the pistons, as to other engines.

I have heard this is standard practice here in NC engine shops doing NASCAR work.

As a previous poster said, on huge diesel pistons in ships and stationary electric power plants there are passages up thru the con rods that channel either water or oil to cool the pistons.