The Importance of Friction Reduction

[LarryD]

I came across an interesting article on friction reduction and how the drag racing engine builders deal with it. The article says that, due to friction, an engine is only about 85% efficient. That means on a 200 hp engine, there is 30 hp loss of potential power. The engine builders deal with it by more efficient engine components, but the rest of us just add our favorite friction reducer to the oil.

Free Horsepower

 

[MolaKule]

Interesting article and you might want to put this post in the Racing Section.

 

[mechtech]

Isn't most of that friction due to the internal drag of the oil?
That's why many Nascar vehicles qualify with 5W oil.

 

[Mystic]

The actual efficiency of a gasoline engine is only about 25% or less. There is an equation in Physics that shows this. I can't remember it offhand.

I think a diesel locomotive is something like 35% efficient. The old steam locomotives were only something like 5%-10% efficient and plus required a huge amount of maintenance so you can see the reason they were replaced.

I think a gas turbine is something like 40% efficient.

You have the Carnot efficiency and then the actual efficiency. No heat engine can be more then 40% efficient in terms of actual efficiency very easily.

 

[Ken2]

Modern industrial diesel engines are the most efficient engines going, something in the 45% range. Gas turbines have the advantage of small size, light weight, and quick to bring up to power, but they are not high in efficiency--no gas turbine trucks, trains, boats, or ships except the Navy that needs the small size, light weight, and big horsepower.


Ken

 

[Rodbuckler]

He only mentions windage briefly, and discusses mostly the ring package and oil control. Adding a vacuum pump for the crankcase can make a major difference in power in a high-RPM engine. You don't want to spend power beating the crackcase air to death with the back sides of the pistons if you don't have to.

 

[Rick20]

I think alot of the article deals with the importance of properly operating rings. Alot can carry over into a daily driver. A carboned up ring pack with a ported piston design is basically useless. I think alot can carry over as well with oil control robbing the combustion efficiency of a good fuel air mix. If we don't have money to burn, then clean ring packs performing optimally ought to produce economy in a motor, unless the excitement of newly found power goes directly to the right foot. ARX can get you there. Although thought of as a cleaner, ARX was originally designed as a friction reducer.

Thanks Larry, I am impressed with the verbage of the middle ring function, often refered to as a compression ring is really much more in the overall scheme of design, namely oil control. May be it should be called the hybrid ring.

 

[carock]

Engineers can estimate the friction of an engine by rotating it at low speeds with the spark plugs removed. We measure the torque required to do this with racing engines all the time. With and without valves installed. If the engine is too difficult to rotate ( too much torque) then we strip it and start over. We also test used race engines this way. It is very important to identify sources of friction and deal with them.A used engine that still requires a lot of muscle to turn the bottom end always means you have a real problem.The Formula V ( air cooled VW's)guys have developed identifying friction sources to an art form.

 

[Kestas]

Our lab has done work for Roush Racing. I can categorically state that the racing teams go through herculean efforts to reduce the friction in an engine.

 

[Mitch Alsup]

A) there are large turbo diesel engines that are 50% efficient. What I mean here is that 50% of the energy content of the fuel is converted in to useful power at the output of the crankshaft.

B) natural gas turbines are (can be) nearly 50% efficient

C) a gasoline engine can be as efficient as 31%-32%, but typically operate near 25% at low-to-moderate throttle openings.

Of the 75% energy that is lost, about 25% goes out through the water jacket, 25% goes down the tail pipe, and 20% goes into heating the oil, and 5%-odd goes into pumping losses.

D) the equation you are looking for can be found on the following page::

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/adiab.html#c1

 

[quick_16]

I have been building own Big Chevy Drag engines for a few decades. Many things are done to a drag engine that can't be done on a street engine that improve the efficiency. In fact some things you don't even see on a NASCAR engine, like Roller Cams.
Some of the items I have that help are:
Titanium valves and retainers
Belt driven Vacuum pump for oil pan
14.5:1 Compression
Coated bearing inserts
Low tension oil rings, Gas ported pistons
Major cylinder head porting and valve job.
Belt driven camshaft
Belt drive oil pump and dry sump (my wish list)
All these add up and make for better efficiency

It's a relative statement so don't go off on me.
Hope this helps

 

[TheTanSedan]

In the late 1960's, Chrysler engineers figured that the V8-440 in Magnum/TNT/Commando form needed 125-HP to overcome internal friction at above 5,200 rpm.

The whole point, in my mind, of a custom motor (old fashioned V8 or straight 6) is to be able to bring internal friction way down, and to re-cam a bit to take advantage. That is, a bit more power, more easily obtained, at a lower rpm, and over a broader rpm range.

Or, less cam to do the same work.

And if one can optimize intake and exhaust pressures for a given vehicle, then one has practically a new motor, as if it had been increased in size.

But it sure is expensive to do it right.

 

[Mitch Alsup]

Quote:

---

I have been building own Big Chevy Drag engines for a few decades. Many things are done to a drag engine that can't be done on a street engine that improve the efficiency. In fact some things you don't even see on a NASCAR engine, like Roller Cams.
Some of the items I have that help are:
Titanium valves and retainers
Belt driven Vacuum pump for oil pan
14.5:1 Compression
Coated bearing inserts
Low tension oil rings, Gas ported pistons
Major cylinder head porting and valve job.
Belt driven camshaft
Belt drive oil pump and dry sump (my wish list)
All these add up and make for better efficiency

It's a relative statement so don't go off on me.
Hope this helps

---

I have a street engine (355 Ferrari) that happens to be bone stock, yet has a) belt driven vaccum pump to the pan--actually its a dry sump system with 2 scavenge pumps; b) pistons have gas ports; c) the heads flow more air then the cylinders can consume--that is a serious port job from the factory; d) belt driven camshafts--check; e) belt driven oil pump and dry sump--check;

You forgot some components: f) piston oil squirters-- allows higher cylinder pressures without detonation; g) velocity stacks; h) throttle valve per cylinder; i) ti rods; j) forged billet crankshaft; k) forged billet camshafts; 180 degree crankshaft for better breathing--that is the intakes and headers work in concert--which is not easy with 90 degree V8 cranks.

About the only thing missing is the ti valves and 14.5:1--its down at 11.5:1, since you really don't want low tension rings and expect to pass the 120K mile emissions requirements.

But none of this was done for "better efficiency" in any metric that the consumer would understand as "Better efficiency"