Dohc...

For Automobile's "Tech Talk" in a special issue:

<<DOHC: Camshafts are responsible for opening an engine's valves. Engineeers have stuck them all over the place, but the current concensus is that using two for each bank of cylinders and mounting the camshafts atop the cylinder heads is the best arrangement, hense the term "DUAL OVERHEAD CAMSHAFTS".>>

Our SVXs have quad overhead cams, right? It says "4 cam" on the engine cover. So, doen't that mean that there's two for each cylinder bank, like most cars, and like most cars also, there's two cylinder banks, so...shouldn't this term be called QOHC for quad overhead cams?

<<VARIABLE VALVE TIMING: To make engines cleaner and more efficient than walking, car companies have turned every stone seeking performance gains. A recent method is to alter how and when the valves open versus engine speed and load. Variable valve timing is a very effictive method of increasing top end power while maintaining low end smoothness and response>>

Our SVXs have IRIS (Intake Resonance Induction System) that is supposed to do the same thing as VVT, right? I'm pretty sure this is true, because with my BlitZe intake, when i'm accelerating and I hit past 4k RPM, the engine rips open, pulls harder, and you can hear the wooshing of the air going through the cone filter. So, is IRIS basically the same as VVT and VTEC?

Thanks for the info

well a v6, v8, v10, v12 or v16 with two sets of camshafts per cylinder bank is still called a twin cam engine.. i don't exactly think "quad cam" is a necessary term when talking about our engines..

and as far as the IRIS goes, i'm really not sure

-adam

[immortal_suby]

We are really only dohc - just 2 cams for each cylinder but 4 total due to the boxer layout

The iris varies the air intake into the runners before it hits the valves. (open/ closed to both sets of runners)

vvt/vtec (or whatever) varies the actual opening of the valves (lift/ duration)

I think it might be a stretch to call ours variable valve timing - since it is not varying the actual valve timing one bit. But it does do something and you can definitely feel it when it comes on.

[CDG]

As above on the Quad-Cam thing, we still only have double-overhead-cam on each bank. Concider how many cams control all the valves in one cylinder.

Variable Valve timing requires some really slick technologies attached to the valves and/or the cam drive.
The SVX does not have this technology.

[homemade wrx]

really depends who you are taling with...MRT rally calls them quad cams...some Muscle car guys say they have quad cams....but generally only count the number of cams per cylinder...not total number of cams.

Thanks for the input

[GreenMarine]

Ya know that DOHC question seemed a little....... duh didn't it??? I mean when you call an engine a "Quad cam engine" you are saying that it has 4 camshafts total... Not Four on each bank of cylinders... Just think about it...

And there is no such thing as "QOHC"... When you say Dual Overhead Camshaft, that means that there are only 2 camshafts "Overhead" .....


I'm done with that...

[homemade wrx]

well I seen a TOHC (triple overhead cam) in real life...it was designed for some crazy piston powered Airplane....go figure...sort of like having the 5 valves per cylinder....why?...really?
And I believe there is actually a QOHC engine out...I think it is bugatti....not sure though

[GreenMarine]

Triple over head cam???? If you can show me a picture of that then it will be the first time I've ever seen that...

[CDG]

My Honda XR500R had triple overhead cam, with an override for a compression release, let me see if I can find a blowup of it, its very cool.
double with an extra gear driven cam for valve #5.

[GreenMarine]

That's crazy... I've never heard of TOHC before..... I guess there's a first time for everything and hey, you're suppose to learn something new every day right, or that day is wasted...

[Ron Mummert]

Does anyone know the cam configuration on VW's "W" engines?

Ron (I know what a Camry is).

[CDG]

Hey Ron.
I bet someone does
just not me

OOO
Quick quiz:
Name 2 engines with no camshafts.

[Ron Mummert]

Originally posted by CDG
Hey Ron.
I bet someone does
just not me

OOO
Quick quiz:
Name 2 engines with no camshafts.

Mazda & NSU's rotarys.

Name an engine without valves (as we know them).

Ron.

[CDG]

Very good, a Rotary engine has no camshafts. and no valves, persay.

One more type of engine.
???