(800) 853-2651
SHOP NOW

High Compression Pistons

SweetFeet

SweetFeet

Well-known Member
More than once I have seen "high altitude", high compression pistons. I understand that you get more power with them.

QUESTION IS:
Do you actually need them if you live at high altitudes or is it just more of a descriptor because the piston has a thicker area at the top... so are they calling it "high altitude" because it is taller than a normal piston?
 
Yes if you want the HP the engine can produce. The higher in altitude the less dense the air so why not compress it more.
 
Any engine, gas or diesel loses 3% of its power for every 1000 feet above the ocean. Some companies offered high-altitude pistons if tractors were used at heights of 4000 feet and never lower. "Altitude compensators" were also used - that later became called "turbochargers."

At the request of a customer we put high-altitude pistons in a Deere 2020 gasser once - at 1200 feet above sea level. It ran so bad we had to tear it back apart. Even with high-test gas and the timing retarded it knocked something awful.
 
Hello sweetfeet,

High altitude operation on an internal combustion engine, makes it run rick .On small air cooled gas engines, you need to change the main carburetor jet to compensate for it.
Are you having a problem or just asking ?
I have a chart somewhere with the jets info.
High compression pistons are not always the answer.
Guido.
 
Guido,

Thanks. No problem, just asking because I see them advertised and just wondered about the reason for them.

All of our tractors have normal pistons.
 
LJD,
Thanks. Interesing info. I hear guys talk about them and thought that tractor pullers sometimes install them to get more power (not sure though).
 
gene bender,

Thanks for the info. So engines do actually run poorly in higher altitudes.
 
(quoted from post at 04:03:09 12/08/12) More than once I have seen "high altitude", high compression pistons. I understand that you get more power with them.

QUESTION IS:
Do you actually need them if you live at high altitudes or is it just more of a descriptor because the piston has a thicker area at the top... so are they calling it "high altitude" because it is taller than a normal piston?
Click to expand...

Remember these tractors were built to run on Kerosene not gasoline, Kerosene is a heavy fuel and needs to be hot to fully vaporize. It needs to be vaporized fully and at the proper air fuel ratio. The high altitude pistons were necessary to adjust the engine to properly compress and burn kerosene in thinner air. So if you live at altitude and want to efficiently burn Kerosene in your tractor you need them.
 
As you go up, air is less dense and there are two effects on internal combustion engines. One is that the air/fuel mixture will lean out and the other is that the dynamic compression ratio will change.

Compression ratio is the change in volume from when the piston is at the bottom of the stroke to the top of the stroke has a significant effect on engine power. By adding more and more dome to a piston and changing the static compression ratio, a manufacturer could maintain the same power in say, Denver as they could in Houston. If you take that same "high altitude" engine and move it to Houston, it will make more power than the lower compression engine but it will be more picky about fuel and ignition timing.

Aircraft with piston engines work these problems by a pilot operated mixture control and with turbocharching.
 
Natural Apirated Engines just make less power at high altitudes because there is less air/fuel mixture drawn into the combustion chamber.
As previously stated the high altitude pistons restore the dynamic compression ratio by increasing the static compression ratio.
 
Not correct on the part about kerosene needing more
compression to burn. The octane rating of kerosene and diesel
is very low.
High altitude kerosene pistons are either to reduce the
power loss on an all-fuel tractor which tended to be dogs at the
best of times. Or for a little more power and efficiency if the
tractor was usually operated on gasoline and occasionally on
"fuel".
 
in addition to the comments about air density which was their original purpose, later on, after WWII gasoline became a lot more available and it likes more compression than kerosene or distillate so people found out that by using the high altitude pistons and running on gasoline and switching to the gasoline manifold that their tractors made a lot more power and got more work done on the farm.
 
Hello sweetfeet,
H.P. ratings at sea level, and SAE H.P. are not taken in the same conditions. I got more if you need it. H.P. ratings are undestood to be SAE.
Which means they are taken at the same conditions-air temp, and elevation.
Guido.
 
If you take an old tractor that only had a compression ratio of 5 to 1 or 6 to 1, you could stick high altitude pistons in and work it OK with decent gas. But a more modern tractor that aleady had 8 to 1 did not usually respond well the higher compression at normal altitudes unless you were using super-high-octane fuel.
 
It's just like when a person climbs a tall mountain it's hard to breath since the air pressure is lower in high altitudes. The air doesn't enter our body at the same velocity.
Normally the people that live in higher altitudes all their life breath slower than those of us at the bottom of the hill. I hope this makes sense.
 
for those old tractors to burn distillate the engine temp had to be up to operating temp. then switched over. these engines just had flat top pistons.
 
They WERE needed in tractors sold to be used in high altitudes in order to get them to make near their rated horsepower. At a high altitude, their is less air getting into the combustion chamber and that means less compression and less fuel can be burned. Two good ways to raise it. One is to raise the "mechanical compression ratio" with a high-top piston or smaller chamber in the head. Another method is to raise the "effective compression ratio" by forcing more air into the engine via intercooling and supercharging. A turbo was the common fix (exhaust driven supercharger). Mr. McCulloch of chainsaw fame invented one of them that were popular. Called the "Paxton" which was Robert McCulloch's middle name.

On the subject of higher mechanical compression - Oliver still holds the record for fuel efficiency in a gas tractor with a very high mechanical compression ratio. It's the Oliver 1800 tested in 1960. Gas tractor that was more efficient then many diesel farm tractors. An Allis Chalmers D10 took 2nd place for the record.

The high compressoin Oliver 1800 gas tractor tested more efficient than these diesel tractors e.g.
Oliver 1755, IH hydro 186, Massey Ferguson 205, Kubota L185, John Deere 2010, Ford 6000, John Deere 3020,
 
We live at 5000 ft,and sometimes work at 8000 ft.You can feel a noticible difference with the "hialtitude" pistons.IH had 5000ft and 8000ft pistons availablle.
 
Nobody seemed to have answered your actual question- "high altitude" refers to pistons designed to make the tractor run better at high altitudes, as has been explained below. It doesn't refer to the height of the actual piston itself. Although you're right, they actually are a little taller than a stock piston.
 
It was thoroughly answered many times with all aspects that you've mentioned.
 
Yeah . . I was thinking the same, but I guess if you breathe "faster" and more often, you can get more volume into your lungs with the less density and come up with the equivalent of oxygen.
 
I had high compression pistons in my Case LA they were about 1/8 above the top of the block. When put the the LP Head on they would turn over because the LP HEAD has a different shape and requires different pistons specially shaped to fit. Two for left and two for right shaped. The compression for these pistons is way above the 6 to 1 standard and requires high octane fuel to run correctly. Aviation fuel is the answer but hard to get unless you own a plane or have a friend with one.
All in all it runs pretty good but is sure hard to crank I had to go to 12 volt as 6 just wouldn't turn it over.
Walt
 
Hello LJD,
My Cummins engines specification booklet has the deration of 3% for each 1000 feet as you stated.
However it also has a deration of 4% for each 1000 feet for turbocharged engines.
Old booklet, 4/73, but I would think still valid?
Guido.
 
Just to add to all the good info below , just pretend you are in tha ocean. If you are in the first 10' of water there is virtually no pressure on your body. (shallower the water the harder it is to float) at the bottom of the ocean you will be crushed to death by that same water. And Buick&deere is wrong when he says it "isn't velocity" making the difference in power , it is compression ratio AND velocity. More pressure forces in more oxygen faster. Pressure by definition creates velocity. Hense the use of forced induction as a remedy for high altitude (low pressure). Actually raising the compression ratio is the least desirable way to make up for low pressure as you are just squeezing that same unfilled cylinder of air into a smaller area to fire it. You still have to lean up the fuel because there is still less oxygen to mix with it. Opening up the supply passages and or forced induction is the only way to get MORE air for more fuel for more power. Raising compression is a "bandaid" that will give a little more "snap" to it but in the absense of sufficient air pressure to completely fill the cylinder with oxygen to be able to efficiently burn a good amount of fuel you will not make much more power with just the bandaid. When the NHRA pro stock cars run their event at Denver each year they look sick. Their rules only allow carbs and of a set size. The supercharged cars don't suffer much and only because there is less down force on their rear wing so a little less traction to hold all their power.
 
More power is arrived from having more air/fuel mixture in the combustion chamber. That is density . The combustion chamber with more moles of fuel and oxidizer will release more energy.
The high compression piston was a low cost partial compensation to restore combustion chamber pressure to "sea level " pressure with standard pistons. Certainly cheaper than adding forced induction .
Mixing up density, velocity and weight is about as common as those who mix up work, power and torque.
 
"Certainly cheaper than adding forced induction". Have you heard about supercharging small displacement engines utilizing a GM 454 smog pump? Some of the guys on the N board swear by it. A simple bracket to hold the smog pump in place driven by the fan belt with a relatively short induction tube to the carburetor. On the Ns they use an NAA carb. It fits better. Gives, as I recall, 6-7 psi over atmospheric. There's more on this at a website entitled: "Dirt-cheap supercharger by Steven Richmond".
 
Have to go draw through carb setup or otherwise pressurize the fuel system if it's blow through.
Then again back in the day of high altitude pistons in gasser and all fuel engines. There were no emissions air pumps on 454's.
Today a whippel supercharger off a Buick 3800 is the bargain blower.
 
Might be the reason they use the NAA carb. Just works better although my basic understanding of it was because they could turn it around so intake faced the front. With only 6 or so psi over atmospheric coming in I doubt that fuel blow back would be a problem. And evidently it isn't or at least that's what I'm led to believe. Never saw the actual installation. Interesting, though.
 
My guess is that it probably didn't use all that much more fuel. Smog pump was just enough to give it a little boost, Maybe 5hp. ??? In that case, that's probably why they're using the NAAs carb. NAA put out about 6 more HP (belt) than the N. Fuel consumption of the '48 N (belt) was 2.4 gal per hr. Fuel consumption of the '53 NAA was 2.9 gph. Maybe it's all BS. I'd like to see the installation.
 
So you are saying that forced induction which only increases the velocity of a set density of atmosphere entering a closed cylinder through valves or ports that are only open for a preset amount of time doesn't make up for the lack of natural pressure at sea level of 14>7 psi? Density is the amount of oxygen content in the atmosphere as a percentage. It is the same "density" at 5000' as it is at sea level but it doesn't have the pressure to move it into a low pressure area such as a cylinder or even your lungs. What does eventually fill them is still the same density as far as oxygen content but there is less total volume because of less pressure/velocity pushing it in there. The more cu in of "atmosphere" the more oxygen but the actual density (ratio) is the same. Atmosphere is not 100% oxygen.
 
Forced induction increases the density, the weight, the number of moles per cu" volume of the gasses in the intake manifold/port/combustion chamber. Velocity will increase as a function of increased delta P.
I have no idea why you think the velocity of the gasses increase but the density stays the same.
 
(quoted from post at 11:58:04 12/08/12) Just to add to all the good info below , just pretend you are in tha ocean. If you are in the first 10' of water there is virtually no pressure on your body. (shallower the water the harder it is to float) at the bottom of the ocean you will be crushed to death by that same water. And Buick&deere is wrong when he says it "isn't velocity" making the difference in power , it is compression ratio AND velocity. More pressure forces in more oxygen faster. Pressure by definition creates velocity. Hense the use of forced induction as a remedy for high altitude (low pressure). Actually raising the compression ratio is the least desirable way to make up for low pressure as you are just squeezing that same unfilled cylinder of air into a smaller area to fire it. You still have to lean up the fuel because there is still less oxygen to mix with it. Opening up the supply passages and or forced induction is the only way to get MORE air for more fuel for more power. Raising compression is a "bandaid" that will give a little more "snap" to it but in the absense of sufficient air pressure to completely fill the cylinder with oxygen to be able to efficiently burn a good amount of fuel you will not make much more power with just the bandaid. When the NHRA pro stock cars run their event at Denver each year they look sick. Their rules only allow carbs and of a set size. The supercharged cars don't suffer much and only because there is less down force on their rear wing so a little less traction to hold all their power.
Click to expand...

As another has posted you have mixed up a few things: Your example of the ocean and the pressure increasing as we go to deeper water is correct. In a simliar manner we are all in an ocean of air and the air pressure increases as we go deeper in that ocean of air. However, air is a little different than water in that it's density increases significantly as the pressure is increased. At sea level we are in the deepest part of the air ocean and the pressure and density of air is at its maximum. Conversely at the top of Pikes Peak we are in "shallow air" and the pressure and therefore density is much less than at sea level. This air pressure is applied equally at the inlet side and the exhaust side of an engine so the change in power output results from the change in air density. An exception would be for forced induction engines; the inlet air is pressurized which increases the density and in the event delta pressure is increased across the inlet system the air velocity can also increase. In this case the change in power results from the air density increase and to a smaller degree the velocity increase.
 
Because I'm defining "density" as the ratio of oxygen to the other gasses that make up the atmosphere. When you blow "atmosphere into a cylinder , you are forcing volumn in but you are not changing the ratio. It isn't all oxygen and oxygen is the only gas giving power. A piston only has a set amount of travel to get itself filled. At 5000' it needs something to get the pressure at least back to 14.7#. A "volumn" of air needs needs pressure to move it effectively and pressure acting on volumn equals velocity. Basically I think we are referring to two different "densities" , fuel/air mixture and atmospheric oxygen levels.
 
I'm not quallified to discuss the issue any further because I don't know how to spell "volume" correctly. Prolly cuz I don't have a degree or sumpin?
 
You must log in or register to reply here.

Similar threads

M
John Deere A high compression piston rings
Replies
12
Views
635
Stuart
S
D
Ford 640 with high compression pistons
Replies
10
Views
627
RBnSC
RBnSC
E
General MF 35 piston question
Replies
4
Views
777
Ericp351
E
B
JD 720 Gas Compression test
Replies
12
Views
446
BMAN in Detroit
B
R
Kohler 301S ,Don''t get screwe
Replies
2
Views
645
Riderrider
R
Tractor Parts Tractor Manuals

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Copyright © 1997-2024 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters
Website Accessibility Policy

Back
Top