hey, this nut at my school was telling me about his hybrid civic today. as he was yacking away i was reading the names of all his "sponsors" (read stickers). the biggest one up there was DOHC VTECH. i know what vtech does but what is the big deal about DOHC? so asked the guy and he was like, its the key to his power. he goes on to say that if he had the same motor that was sohc, it would have 50% less power because the engine can rev up faster, thus more power. that made a little sense, but i really didn't believe him it so i'd thought i'd ask you guys.

 

Acronym lesson.

DOHC = Dual OverHead Cam
SOHC = Single OverHead Cam

This relates to the number of total camshafts in each cylinder head -- there are two cylinder heads in a V-motor, one cylinder head in an inline motor.

VTECH is a mispelling of the Honda/Acura "VTEC" system. VTEC is Honda's method of adjusting cam duration and lift by means of a "dual-mode" camshaft. At higher RPM's, the rocker arms that make the valves move switch over to a 3rd cam lobe on the VTEC cams. This altherante lobe is much taller / more aggressive than the "normal" lobes, whicih provides a flat torque curve throughout the rev band -- which equates to more top-end horsepower.

DOHC is not a "wonder of the universe", and is not responsible for his power. There are VW Bugs (old ones) that run 8-valve SOHC heads that make way more power than he does.

And if he wants to argue "horsepower per liter" of his might 1.6L motor, then he can argue with a brick wall. More horsepower per liter is not a function of "technical prowess" or "efficiency". Horsepower per unit of fuel is efficiency, and VTEC-equivalent systems have been around since the 1940's. In fact, DOHC has been around longer than pushrod designs, so DOHC is "less futuristic" than pushrod motors.

He's a ricer, a poseur, and obviously knows little or nothing about motors or what make them work. He is likely one of the many people who expect their intake to add 15 horsepower, and is also likely one of the many morons who "build up" their car and run a whopping 17.9 @ 84mph when they take it to the track.

-Red-

 

thanks red!

so what does JDM stand for?

 

Japanese Domestic Market

 

That is true about DOHC not producing all of his power but I have to disagree in saying that it doesn't help. A DOHC engine allows us to produce more valves per cylinder than a SOHC. This does make an increase in power and response. Maybe back in the day you could get more power out of an 8 valve SOHC than a dual but nowadays it's a lot less likely. True not all DOHC engines produce a lot of power but in Ricer Hondas a DOHC will destroy a SOHC anyday.

(and Red i'm sure it's a 1.8 not a 1.6)

 

nope, 1.6. The Civic Si is the first Civic to offer the 1.8L motor..technically an Integra Type R motor. All other Civic's have the puss 1.6

On another note..I would never buy less than a 2.0L motor. What's the point? They need to make more 2.5L 4cylinders..*drool*.

 

Give me a dinner-plate-piston 5.0L I4 any day.

 

You are incorrect.

Double overhead camshafts do NOT allow more valves per cylinder. The Civic EX (D16Y8) motor is a SOHC 16-valve VTEC head. That's a single cam, and 16 valves. The number of camshafts is NOT related to the number of valves.



Incorrect as well. All Civics (up to the 2000 model year) are equipped with 1.6L motors. The Civic Si (or SiR in Canada) comes with the B16A2 powerplant, a 1.6L 16-valve DOHC VTEC motor that pushes 160HP and 111 lb/ft of torque.

The 2001 model Civics come with a 1.7L motor, I believe the designation is K17xx (where the xx is a single letter and a single number, but I don't remember what letter or number)

The Integra motors are all 1.8L motors; the Integra Type-R is a B18C5.

Double overhead cams have little or nothing to do with performance. It's simply an alternate method of operating your valves. Quite honestly, SOHC designs rob less power and operate just as well as DOHC designs. More rotating components simply means more losses and more things to break.

-Red-

 

As a humorous aside,

450 horsepower out of an Acura DOHC 16-valve 1.8L drag-only motor that runs at 25psi really isn't that impressive.

Fact: Jack Roush was building (many years ago) 2.3L and 2.5L Ford Pinto motors that made 700HP and above. This is on 8-valve SOHC setup, and these motors were built for road racing events that ranged between 2 and 24 hours.

Let's see an Acura 1.8L make 700 horsepower and continue doing so for 24 hours in a row. In short -- you never will.

8-valve technology is sturdy and is definately still relevant in the current "import" market. Dual overhead cams are likely quieter and definately get better gas mileage, but if you're racing, you don't care about either.

-Red-

[ September 26, 2001: Message edited by: Red ]

 

Ahh yes pintos...the ultimate sleepers...seriously...I've seen some pintos get up and go like no other... wink.gif