OHC vs OHV

Appleseed wrote: You want gnarly induction? Look up sleeve valves. I'd like to see this make a comeback with today's synthetic oils to cut down friction. Bristol Hurcules Head may explode.

You beat me to it! They are interesting.

Wonder how that single sleeve valve engine would do with, say, 12:1 compression? I would think the sleeve would deform and stick.

depends on what you made it of and how much "gap" it was allowed between the block and cylinder

Sleeve and rotary valve engines will never fly because of combustion chamber shape issues.

Proper shape is KEY to power and fuel economy and emissions. You can't get a decent shape with a valve like that.

What really drove this home was when Ford realized something like a 10% drop in idle HC on one engine by eliminating the stamped arrow on top of the piston.

2 stroke direct injection.

Work it like the old 2 Stroke Detroits!

1966stang wrote: Trying to find rational info on why car makers are using OHC vs OHV. Would seem that OHV would be a simpler valve train, but everyone is going to OHC...what are the advantages of OHC motors, and how do they stack up against OHV motors?

• Is an OHV configuration simpler if you have a global manufacturing strategy and all of your plants around the globe are tooled for OHC configurations?

• If you're selling a vehicle aimed at fuel concious buyers and the (uneducated) consensus is that OHC is inherently more fuel efficient (same as OHV engines 'make more torque'), does it make sense to swim upstream with an OHV configuration that goes against market expectation even if the data shows it is the equal of an OHC?

• If an OHV and OHC engine are the same in package/weight and performance until 4500rpm, but the OHV engine is much cheaper and the OHC engine makes 30 more hp at 6500 rpm, is it a technical decision which configuration is 'better'?

Outside of emissions driven hardware most automotive technology is driven by fashion, is not really so new or innovative, and would be instantly recognisable and intelligible to engineers at the start of the 20th century. The much more difficult question is what will drive people to spend large sums of money on cars, and the answer has always been technology. The trick is to make the new technology a basic need for the general population instead of a luxury. It's a surpise to us that Apple and other such device manufacturers have accomplished this as of late, when auto manufacturers have been doing this since their inception.

Which is a good thing, because there is no other music like a pack of 410" dirt late models at 8k rpm...

grpb wrote: - Is an OHV configuration simpler if you have a global manufacturing strategy and all of your plants around the globe are tooled for OHC configurations?

No.

- If you're selling a vehicle aimed at fuel concious buyers and the (uneducated) consensus is that OHC is inherently more fuel efficient (same as OHV engines 'make more torque'), does it make sense to swim upstream with an OHV configuration that goes against market expectation even if the data shows it is the equal of an OHC?

Chevy and Dodge got a lot of truck sales after the F-150 went to the 4.6 and 5.4. Yes, the engines were also downsized at the same time, but the message was made.

Truck sales are NOT a trivial market in the US.

- If an OHV and OHC engine are the same in package/weight and performance until 4500rpm, but the OHV engine is much cheaper and the OHC engine makes 30 more hp at 6500 rpm, is it a technical decision which configuration is 'better'?

For a V engine, the OHV will be significantly better in packaging and weight, allowing either a smaller, lighter engine, or a larger engine in the same package space.

A large, low-revving engine can and will get better fuel economy than a smaller engine. The car determines how much power is needed, but a larger engine that revs lower has more time for complete combustion and will usually have lower internal friction due to the lower ring speeds.

The much more difficult question is what will drive people to spend large sums of money on cars, and the answer has always been technology.

I thought it was road salt

Doesn't the 3cyl EcoBoost have the oil-bathed timing belt?