I know the Protege is DOHC but what's the difference between SOHC and DOHC really? I keep on hearin' people sayin' DOHC is a lot better, but why?

 

You have to seperate cams to move your gasses. One is an exhaust cam and an intake cam. On a SOHC there is only one cam.

 

Also not all Protegé's are DOHC. I have a 1st gen with a SOHC 1.8L. Yes DOHC's are better. Mine makes only 103 hp stock, the DOHC makes 125 hp stock. But, they're both 16 valvers which really makes me wonder why an extra cam would make it put out, like, 20-some percent more power. Which leads me to wonder "What if Mazda had made a triple cammer?" Would it put out like 150-160 hp? Oh well, probably not possible and if possible not practical. It would be cool, though if Mazda came out with a 20-valve (5 valves per cylinder) head. Yeeeaaaah.... We can always dream, can't we?

P.S. It's about time for Mazda to come out with their next big thing. You know, the rotary engine, the Miller cycle engine. What next? (Sigh)Hopeful/hopeless daydreams.

 

doesn't the mustang cobra have 4 to 5 valves per cylinder? That would explain why it make so much more hp over the normal 4.6. Think of squeezing that one into the protege eh? Also I'm not sure what SVT is doing to the focus 2.0 but they are getting it put out 160 to 170 at the wheels for the focus SVT. Maybe mazda can take some advice from SVT and actually get some hp in the protege! I know that the focus zetec is quite different from ours (and ours is a lot more durable) but that's a 40 to 50 hp power increase.

 

honda made the early prelude engines with 3 valves per cylinder with one over head cam. i don't know any thing more about that engine, though.

with two cams, as opposed to one, you get less friction when they are spinning trying to open the valves. that is why you get more power. anything you can do to reduce the friction/losses in your engine will give better power. this is why an overhead cam can make more power than an in-block cam also.

take a look at the following for more information:
http://www.howstuffworks.com/camshaft2.htm

 

Sorry I shouldn't have said that Zetec wasn't durable. Just that Ford has had some QC issues with them and all of thier engines. I have the Duratech in my Tour and really love it but have seen other people have so many problems with them that they don't ever buy a ford again. My experience with Mazda on the other hand has been mostly good and it appears that there are a lot less QC issues. (possibly because it's still controled mostly by Mazda instead of Ford) I like some of the new offerings by Mazda that are using ford ideas ie the 6! But am a little apprehensive as to what it means for Mazda QC.