car GURUS -- is PUSHROD as "efficient" as OHC or DOHC?

[TuffGuy]

yes or no and why? i'm trying to resolve an argument. i think that ohc/dohc is more efficient than pushrod, but i don't know the reason.

 

[Viperoni]

Less rotating mass.
plain and simple.

 

[OpalFrost98GT]

Yeah....my Mustang Gt has a 4.6 litre Sohc engine....lots of balls top end...however OHC engines lack low end torque

 

[MisterNi]

To add to what Viperoni said (which is true), less moving parts = less friction.

 

[Pacfanweb]

OHC is more efficient. Friction, weight, strength.

Friction in that the aren't all the extra parts involved with OHV.

Weight, for the same reason, since it takes HP to move that extra weight.

Strength since by eliminating the pushrod, you eliminate a major weak link. Pushrods also flex a lot, which causes loss of valve lift/duration. Not really that critical except in racing applications, but it does happen.

 

[Cyberian]

How stuff works

 

[OpalFrost98GT]

To Add:
OHC's are More efficient because all the mechanical action required to open and close the intake and exhaust valves is contained in a single unit(HEAD) less parts..weight..chance of breakage...wear...

 

[toph99]

Then what is the advantage of a DOHC system?

 

[Viperoni]

Probably the fact that you can keep the valves much further apart physically in the head.

 

[OpalFrost98GT]

OHC=2VALVES PER CYLINDER
DOHC=4VALVES PER CYLINDER

 

[MisterNi]

<< Then what is the advantage of a DOHC system? >>



DOHC = Dual OverHead Camshaft

Only really useful on cars with 4+ valves/cylinder, one camshaft can control either an exhaust or intake valve, or more commonly 1exhaust, and 1 intake valve. This gives the engine a much better range and flexibility for intake/exhaust.

Downside, cost and more moving parts = more money if something goes wrong with your valvetrain.

 

[351Cleveland]

Pushrods are wasted motion... but OHC setups are soooo expensive to work on...

 

[OpalFrost98GT]

The more air that can be introduced into an engine...the more efficient the engine is. 4 valves per cylinder allow the engine to breathe MUCH better and produces far more horsepower than an equvalent 2valve engine.
Take the Mustang GT 2valve and Cobra 4valve for example....the Cobra's 4 valve DOHC head is what gives it the extra 85 horsepower out of the same 281 cubic inch block. Well..prolly a bit more to it than just the heads but that is the main advantage...

 

[351Cleveland]

Opal -

I am fairly confident the Cobras also have different cam aspects and different intakes (which includes the manifolds, MAS, throttle bodies, etc.), not to mention a different computer controlling the whole show. While the extra 2 valves is helpful, it is not the only contributing factor.

 

[Linux23]

i think DOHC setups allow for a higher response engine. I do know that DOHC setups use a sh!t load of fuel. my pops 8 cyl. pushrod engine seems to go 100 miles to the gallon, my car only goes about 15 mpg.

but i have a lot more fun with my baby, hehehe!