Piston cooling jets?

[SloGN]

This line has never made sense to me. Basic science would dictate that things actually suspend more easily when they are exposed to vacuum. If it were the other way around it would eliminate one of the reasons for a pump shot in a carburetor (or pump shot code in wet manifold FI systems for that matter).
Also, oil has a very low vapor pressure and is not a factor in an engine application. If I understand vapor pressure correctly, it means that pressure changes don't easily affect its state as a condensed liquid.
Beyond that, I don't think that oil lubricates the walls of the cyl and pins because it is suspended in some type of vapor form. I think its just flung around. So actually, if it did "suspend" that would be a bad thing.


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well actually since there is a vac in the crankcase there is no air to be whipping around the crank. So if there is no air the oil can't be suspened in the air. this is why they use the oil squirters. Also since they use the crankcase vac the oil drops to the pan faster to help reduce drag on the rotating parts. they also knife edge parts and dedur the parts to they can't hold oil for added drag. do just a little bit of research and you will find out what they do and why.

 

[turbodave231]

You may not have seen signs of piston overheating but think about this: The piston could be well within the temp limits of the alloy it is made of but could be significantly hotter than the rest of the combustion chamber and potentially hotter than what the octane of the fuel can support without detonation when pushed to its limit.

Here is what I'm thinking: It is generally accepted that if you contain the heat of combustion in the cylinder, you can utilize the heat to expand the gasses and create work (downward force on the piston). Transferring heat into the cylinder head, cylinder wall or piston pulls heat away from the expanding gasses and decreases the efficiency of the combustion process.

In some instances, it is desireable to pull heat away from components that tend to absorb more of the heat of combustion. (exhaust seats and exhaust valves as an example)

It stands to reason that avoiding the transfer of heat into these components will make the combustion process more efficient. As you stated, the piston has very little transfer path to shed heat.

In an engine the piston will reach an average temperature that it will maintain during any given operation condition. I have no data to support that my pistons are ever operating at a temp that contributes to detonation. If I am not experiencing detonation and not damaging the piston, pulling heat away from the piston using piston oilers will only increase heat transfer from the combustion process and raise oil temps. Why would I do that?

I might even benefit by raising the average piston temps so that they will not absorb as much of the heat of combustion!! Heat transfers faster when delta T is great!! I make this last statement with tongue in cheek. Intuitively, raising piston temps would not be directionally correct!

The only time I would consider piston oilers is if I had data that told me I was operating my pistons beyond their temps limits -or- that piston temps were contributing to detonation. In my specific situation, with the fuel I use and the operating conditions, I don't see either problem.

If I were concerned about piston temps, I would seriously consider a heat barrier coating for the piston dome, rather than continuously pulling heat out of the combustion process and raising oil temps.

No flames intended here.............but enjoying the discussion!

 

[GARY HARVEY]

TD123... Nice to see you understand the show.
Some do, some don't and then there are those that don't care.
It's interesting to witness the look on a doubters face when seeing results of what coating's can accomplish.
Ceramics, Dry Film, and the other tech advancements are viable.
There is stacks of information written over the decades.
Bill Elliott (Denver, NC) ended being Rusty's Crew Chef and went into the coating business in the early 90s for good reason. A copy of 1989 StockCar will explain his understanding of coating's, too bad he quit, he is a very sharp engine man.
Dave Emanuel wrote the article, it is one of the best out there and it's 20 years old.

 

[Pablo]

well actually since there is a vac in the crankcase there is no air to be whipping around the crank. So if there is no air the oil can't be suspened in the air. this is why they use the oil squirters. Also since they use the crankcase vac the oil drops to the pan faster to help reduce drag on the rotating parts. they also knife edge parts and dedur the parts to they can't hold oil for added drag. do just a little bit of research and you will find out what they do and why.

Wow. Ok.. theres a few points you have wrong.
First there is air in the crankcase. No matter how much vacuum you pull, there is no such thing as a perfect vacuum that humans can create. If you could create one, you'd certainly win the nobel prize. I don't think nascar is to this level (yet ). The term vacuum in the sense that we see on a vacuum gauge is not even an absolute measurement, its a relative measurement to whatever atmospheric pressure you are in.
Cranks are knife edged for a few reasons, one of which is aerodynamics. I don't have a 9 second car much less a college degree, nor do I have an automotive business, so I can understand your likely skepticism to this statement. However, thanks to the internet, all kinds of information is free now.
Lack of air has little to do with something's ability to suspend. How do you think cosmic dust and rock floats around in space? It still has mass and still can be flung yet it exists in an environment with pressure maybe thousands of times lower than anything you could produce in an engine on earth.

I am unaware of any mechanism that would allow oil to drop to the pan faster because you have imparted a relative vacuum to the crank case. If you could tell me how this happens I would be glad to know except that maybe there is a miniscule amount of aerodynamic drag imparted upon the oil droplets as they run down the walls of the engine. I'd like to see how much faster an oil droplet runs down a lifter valley wall at 20 kpa vs 100kpa. Actually I'd bet we would not be able to measure a difference with current human technology but hey I've been wrong before. That is just my gut instinct. I'd be pretty amazed if there was a difference. Do you have any data on this?
Most of the mods Ive seen to increase oil return involve polishing and de-burring specific areas of the block and even that has a downside/or added consideration as you've now decreased surface area for the block to transfer heat to the oil.
And finally, if cyl wall lubrication was a problem they would address the issue by lubricating the cylinder wall vs the backside of the piston where the squirters are aimed

 

[Pablo]

Here is what I'm thinking: It is generally accepted that if you contain the heat of combustion in the cylinder, you can utilize the heat to expand the gasses and create work (downward force on the piston). Transferring heat into the cylinder head, cylinder wall or piston pulls heat away from the expanding gasses and decreases the efficiency of the combustion process.

In some instances, it is desireable to pull heat away from components that tend to absorb more of the heat of combustion. (exhaust seats and exhaust valves as an example)

It stands to reason that avoiding the transfer of heat into these components will make the combustion process more efficient. As you stated, the piston has very little transfer path to shed heat.

In an engine the piston will reach an average temperature that it will maintain during any given operation condition. I have no data to support that my pistons are ever operating at a temp that contributes to detonation. If I am not experiencing detonation and not damaging the piston, pulling heat away from the piston using piston oilers will only increase heat transfer from the combustion process and raise oil temps. Why would I do that?

I might even benefit by raising the average piston temps so that they will not absorb as much of the heat of combustion!! Heat transfers faster when delta T is great!! I make this last statement with tongue in cheek. Intuitively, raising piston temps would not be directionally correct!

The only time I would consider piston oilers is if I had data that told me I was operating my pistons beyond their temps limits -or- that piston temps were contributing to detonation. In my specific situation, with the fuel I use and the operating conditions, I don't see either problem.

If I were concerned about piston temps, I would seriously consider a heat barrier coating for the piston dome, rather than continuously pulling heat out of the combustion process and raising oil temps.

No flames intended here.............but enjoying the discussion!

Nice post Turbodave, and I too enjoy the discussion

I have a few counterpoints and things for you to consider;

First, this whole heat thing I think is misunderstood. Yes, keeping heat in the chamber increases efficiency which would be great if you were concerned with brake specific fuel consumption since you can use more btus from your fuel to move the car forward instead of spitting them out of your radiator.
For drag racing though, we aren't really worried about that because we are not limited by the amount of fuel we can carry or add. Horsepower is not directly related to BSFC, case in point, turbo engines have pretty bad BSFC numbers when you compare them to N/A engines. The extra fuel is used for cooling the chamber which enables us to stuff more air, and thus more fuel to generate more horsepower.
We may lose some thermal efficiency in the process, but the loss is more than made up for by the gain in air consumption.. Actually you can see this in two engines; one of which with a low bsfc, ., and one of them with a high bsfc and the high one generating more hp despite having the same displacement. One is more aerodynamically efficient at filling the chambers with air than the other despite maybe having to consume more fuel than the other per horsepower.


As far as piston temps go, you may not have detonation issues now, but you could if you wanted to. Raise the compression, raise boost, etc, you are going to raise the mean combustion temp high enough to eventually induce detonation. The thing is, the combustion chamber doesn't in practice induce detonation because of an average temp.

All it takes is one hot spot. In this case, if you keep raising the combustion temp, your piston would theoretically be the first spot in the chamber (not necessarily, and maybe just a contributor) to cross the threshold from detonation tolerance to detonation intolerance. It could just be a very big straw that breaks the camel's back. The rest of your chamber could be good for a couple more points of compression or a couple more pounds of boost without pushing the fuel past that point. There could be a little bit of liquid fuel left whose latent heat could be used to cool the errant exhaust valve. With a hot piston, some of that or all of that was used up cooling the piston. With an uneven chamber temp you now have sacrificed some breathing room in this regard.
Instead of coming up on the limits of your fuel because of one part, or two parts, wouldn't it be much better to hit the absolute limit because everything was at the limit at the same time and to an equal degree?

Transferring the heat to the oil makes it manageable. You can always add oil coolers or oil capacity and take that heat that would otherwise limit your dynamic compression ratio and put it outside of the car.

And as far as heat barrier coatings go, I am really curious to see what kind of thermal conductivity reductions these thing show in practice. I propose a test of heating a non coated piston with say a propane torch held to a precise temperature, and then heating a coated piston the same way and then measuring the temp at the backside of the piston. I def. think coatings work but I would be surprised if they were capable of rejecting heat as efficiently and quickly as a liquid such as oil. The OEMs use of oil jets in addition to coating I think supports this.

Anyway great discussion I look forward to your thoughts

 

[Mad_Trbo]

Good Read _ To The Top

This was a good read especially for those of you just looking for something interesting to chew on.

 

[GARY HARVEY]

reading and testing are all good

trouble is.... it's all been done and history proved all of the previously mentioned questions and many more than I can't remember.
Find a few old copies of the NASA Tech Brief's and other examples of the research and catch up, this info has been out there for decades.

BTW, [how] can you compare a full time heat test source with the physics of internal combustion, unless you are dealing with the turbine exhaust side of a jet (typically ceramic coated, you bet).
And thermal heat barriers are how thick ?

Keep this little tidbit of info in mind:
ceramic coating deal in microns that create a barrier of isolation. Thinner the better.

BTW, I'm not a big fan of thick condoms either...
(how's that for an analogy?)

 

[DeltaT]

Back from the dead...

After doing a bunch of research, I decided to get my new pistons ceramic coated and to add piston cooling jets. I am planning on pushing this thing pretty hard and wanted the extra edge in reliability.

Here's a piston shot:

And here's some info on the piston oilers:

http://www.blp.com/pdf/NP2006.pdf
http://www.blp.com/pdf/install/DomeOilerInstall1.pdf
http://www.blp.com/pdf/install/DomeOilerInstall2.pdf
BLP Racing Products


This was a great thread that helped make my decision.

Jim

 

[DeltaT]

This is what I was doing last weekend, using the Bo Laws Performance kit to modify the block for piston oil sprayers. It comes with 2 fixtures, one for cyl. 1-7 and one for cyl. 8. Here I'm doing cylinder 3. I have already drilled the hole then stuck the bit through to show the angle:

Here's some other progress pictures as I work on getting ready to install the piston oiling jets.

A better picture of one of the oil feed channels that will feed the jet. The jet will slightly protrude where the bit is sticking out:

This one shows cylinders 2-7 oil feed holes drilled and marked for cutting the feed channels:

The oil feed channel for cylinder one cut and ready for deburr:

Lastly, the tools for the next steps: a drill/tap, tap and 8 jets. The holes don't get completely threaded; you leave the last 1/2" or so unthreaded to prevent the jet from vibrating loose into the motor:

I will finish the cutting this weekend and hope to finish many or all of the jet installations. Then on to some minor block cleanup with a grinder, then another full cleaning. Then finally on to the shortblock assembly.

This kit could be adapted to the Buick V6 block, or BLP may already have something to fit.

In addition to one picture with a bunch of Turbo Buicks, there's a lot of build pictures at my main website if anyone's interested:

More Photos (Edited 04/14/07)

Jim

 

[GARY HARVEY]

Pistons are constantly cooled from several areas.
Fresh Air/Fuel Charge, Skirt/Ring Transfer, Crankshaft Wash and in your application the Ceramic Coated Top.

 

[DeltaT]

Excellent! Since I didn't want to have to go back into the block again (hopefully ever), I wanted to build in the capabilty to be reliable at a much higher HP than I plan to throw at it right away. In a couple years, I may switch over to twins or maybe one large turbo. I like the German practice - overbuild and understress.

Jim

 

[Mad_Trbo]

Excellent! Since I didn't want to have to go back into the block again (hopefully ever), I wanted to build in the capabilty to be reliable at a much higher HP than I plan to throw at it right away. In a couple years, I may switch over to twins or maybe one large turbo. I like the German practice - overbuild and understress.

Jim

Agreed!!!

squirter set up looks familiar!

Much success with your set up.

 

[DeltaT]

More 421ci motor build pictures here:

The Grey Ghost, updated 2/25/11

Jim

 

[novaderrik]

piston oilers are one of the tricks that are used to get more power and reliability our of forced induction engines- anything to pull heat away from the piston is a good thing.
i think pretty much ever modern forced induction engine built by the oems has a piston oiling setup on it- i know GM uses it in the direct injected ecotech 4 cylinders and Ford probably uses it in all of the Ecoboost engines.

 

[TurboDave]

Yes, Ford and GM both use piston jets on their new boosted engines.

 

[DeltaT]

And the final result:

Now I can start the shortblock assembly.

Jim

 

[Mad_Trbo]

Looks familiar

Like it was meant to be there all along.