Your test for today

[Russ]

After CocoPops asked about Twinport yesterday, i thought of this one for you..

Who know's what SOHC and DOHC are? which is more benifitial? and why?

Good luck

[Allen]

Single overhead cam and double overhead cam?

Wouldn't have a clue which was more advantagous, but at an estimated guess, I would say double was better.

[Shad]

http://auto.howstuffworks.com/question562.htm

I thank you

[Russ]

well done shad

[unrealrocks]

What they don't mention is obviously this adds to the weight of an engine alot because cam shafts are bloody heavy.

[Russ]

yep, your right mate, 2 x camshafts and twice the valves can add a lot of wait, but its all about

power:weight

and the performance gain is worth what the extra weight is.

[Scrumpyjack]

But if you use duralumin alloy it can save weight

[wol]

Thought so, my moggie was a SOHC, had to replace it as well. Quite an easy job really.

[Russ]

For those of you who are interested.

SOHC has 1 cam shaft, when it turns the cams on the shaft push down the inlet AND outlet valves. If your car has DOHC, there is a seperate cam shaft, 1 is used to push the inlet valves (fuel air), and 1 is used to push down the outlet valves (exhaust gasses). the DOHC is better because is can more air fuel mix in, and discharge it faster.

[Jiff Lemon]

For those of you who are interested.

SOHC has 1 cam shaft, when it turns the cams on the shaft push down the inlet AND outlet valves. If your car has DOHC, there is a seperate cam shaft, 1 is used to push the inlet valves (fuel air), and 1 is used to push down the outlet valves (exhaust gasses). the DOHC is better because is can more air fuel mix in, and discharge it faster.

Correct right up "the DOHC is better because is can more air fuel mix in, and discharge it faster".

Camshafts deal with the opening and closing of the valves.

Whether you have one or two cam isn't going to change the amount of air you can pull into an engine, or how much you can expell from it.

How much air you can pull in or push out is governed by the displacement of the cylinder and how long the valves stay open for.

[Russ]

ah is that why performance cars have both valves open at the same time for longer then Jiff?

[Knoxville]

DOHC is definatly better, F1 cars are way ahead of that though, they're using Quad overhead cams now

[Allen]

well done shad

I don't get a well done for knowing what SOHC and DOHC stand for off the top of my head without having to resort to the net?

He couldn't even be bothered to cut and paste the answer from howstuffworks.com!

Ok, I may not have known why DOHC is best, but I think that's good of me considering I know hardly anything about motors!

[Jiff Lemon]

ah is that why performance cars have both valves open at the same time for longer then Jiff?

Performance cams will allow the valve to open for a longer duration and give greater lift (open the valve wider).

It's not as simple as leaving it open as long as possible though.... It all starts getting hideously complex - hence why entire books have been written on the subject!

[Russ]

yea i understand jif. its like whipped cream on cake, theres aggressive and then theres too much

ok maybe cake was a bad example.

[Rave]

Yeah, it is complicated, I once got a hooooge combustion engine textbook out of the library and I came nowhere near finishing it. I learnt a lot about valve timing, swirl, squish, compresion, gasflow etc. so it was worth it, even though I've probably forgotten most of it now.

Rich :¬)