Friction losses in engines

[MikeWaggoner at UW]

Anyone have a good ballpark figure for this, and from each component? John Bucknell mentioned if he was going to build an FSAE-Spec motor, "friction would be tiny". I figure hydraulic bearings ain't so good, and ring friction sucks too. I've heard 5-7% is typical, but we spin our motors pretty fast....

[MikeWaggoner at UW]

Anyone have a good ballpark figure for this, and from each component? John Bucknell mentioned if he was going to build an FSAE-Spec motor, "friction would be tiny". I figure hydraulic bearings ain't so good, and ring friction sucks too. I've heard 5-7% is typical, but we spin our motors pretty fast....

[BeaverGuy]

Ballpark figures for individual items? i don't really have a clue. Or even an Idea for an overall figure. I know there are some friction models available in various places, Design and Simulation of 4-Stroke Engines is one. There is a suggested way to estimate cylinder friction in Introduction to Internal Combustion Engines, by Stone, that involves disabling one cylinder at a time while on the Dyno.

As far as components I don't think the Coutte flow of bearings would be too bad, but I could always do the calculation, maybe tomorow night. But roller bearings or no bearings, DLC anti-friction coatings, could be better. The major component that I see for "frictional" losses would be the valve train. It takes a lot of work to open valves and then there is the sliding friction involved too. After that I would think the Oil Pump and water pumps would be the large losses after that.

[Bowtie Man]

This might not be anything you're looking for but have you considered rotary valvetrain? ya it's expensive and I'm not even sure which engines it can be put on, I've seen some V-twins with it. But you'd lose a lot of friction as well as the losses from compressing the valvesprings.
check it out, pretty cool stuff

Luc
University of Manitoba

[Ryan McCauley]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by MikeWaggoner at UW:
Anyone have a good ballpark figure for this, and from each component? John Bucknell mentioned if he was going to build an FSAE-Spec motor, "friction would be tiny". I figure hydraulic bearings ain't so good, and ring friction sucks too. I've heard 5-7% is typical, but we spin our motors pretty fast.... </div></BLOCKQUOTE>
Piston friction is one of the highest contributing factor to frictional losses. The piston skirts friction mean effective pressure increases linearly with engine speed, while the piston rings fmep decreases with engine speed. Another huge frictional loss is due to the pumping friction. The work required in getting the fuel/air into and out of the cylinder, especially at high rpms is enormous. With THIS you might be able to get a pretty decent idea of your individual frictional losses at different rpms. Hope that helps you some!

[VFR750R]

hydrodynamic lubrication is better then anything. A roller bearing crankshaft would have MORE friction. Coatings are almost worthless as there is no surface to surface contact. There are gains to be had though. Bearing sizes and clearances can have a substaintial effect on friction and load capacity, and stock motorcycle bearings are a compromise in manufacturability and materials. Piston skirts are a high percentage of friction and flat tappet buckets suck too (most of you have 16 of those).

There are some books out there on F1 engines and high speed motorcycle engines that outline many changes to reduce friction. One thing I can tell you is the gains in any one area are small and expensive.