hey . Read in todays newspaper and they advertise the 2007 with sohc ivtec . My 2nd gen crv is a dohc ivtec . Both are 2.0 . What the diff a ?

This post has been edited by minde: Sep 9 2007, 12:00 AM

SOHC = single over head cam
DOHC = double over head cam

DOHC VTEC
Honda's VTEC system is a simple method of endowing the engine with multiple camshaft profiles optimized for low and high RPM operations. Instead of one cam lobe actuating each valve, there are two: one optimized for low-RPM stability & fuel efficiency; the other designed to maximize high-RPM power output. Switching between the two cam lobes is controlled by the ECU which takes account of engine oil pressure, engine temperature, vehicle speed, engine speed and throttle position. Using these inputs, the ECU is programmed to switch from the low lift to the high lift cam lobes when the conditions mean that engine output will be improved. At the switch point a solenoid is actuated which allows oil pressure from a spool valve to operate a locking pin which binds the high RPM cam follower to the low rpm ones. From this point on, the poppet valve opens and closes according to the high-lift profile, which opens the valve further and for a longer time. The switch-over point is variable, between a minimum and maximum point, and is determined by engine load; the switch back from high to low rpm cams is set to occur at a lower engine speed than the up-switch, to avoid surging if the engine is asked to operate continuously at or around the switch-over point. The DOHC VTEC system has high and low lift cam lobe profiles on both the intake and exhaust valve camshafts.

The VTEC system was originally introduced as a DOHC system in the 1989 Honda Integra and Civic CRX SiR models sold in Japan and Europe, which used a 160 bhp (119 kW) variant of the B16A engine. The US market saw the first VTEC system with the introduction of the 1990 Acura NSX, which used a DOHC VTEC V6 with 270 hp. DOHC VTEC engines soon appeared in other vehicles, such as the 1992 Acura Integra GS-R (B17 1.7 liter engine). And later in the 1994 Honda Prelude VTEC (H22 2.2 liter engine) and Honda Del Sol VTEC (B16 1.6 liter engine).

Honda has also continued to develop other varieties and today offers several varieties of VTEC: iVTEC, iVTEC Hybrid and VTEC in the NSX and some Japanese domestic market cars.


SOHC VTEC
As popularity and marketing value of the VTEC system grew, Honda applied the system to SOHC engines, which shares a common camshaft for both intake and exhaust valves. The trade-off is that SOHC engines only benefit from the VTEC mechanism on the intake valves. This is because VTEC requires a third center rocker arm and cam lobe (for each intake and exhaust side), and in the SOHC engine, the spark plugs are situated between the two exhaust rocker arms, leaving no room for the VTEC rocker arm. Additionally, the center lobe on the camshaft can only be utilized by either the intake or the exhaust, limiting the VTEC feature to one side.


By the way Vios is using DOHC and City is using SOHC. I also wondering y.

This post has been edited by kevinlim001: Sep 8 2007, 11:31 PM

IINM, SOHC will give better FC and power at the low-end.

the Accord 3.0 is SOHC

This post has been edited by nerd: Sep 8 2007, 11:37 PM

i tot DOHC will give more FC as the cam is reserve only will be use when needed with sohc the cam will be use all the time..

well, but there's no such thing that when the engine is running, the intake cam will not be used right?

having two hands to shift items is faster than one right?

using the same analogy in DOHC/SOHC, hence DOHC = higher FC.

i may be wrong, feel free to correct me.

This post has been edited by nerd: Sep 8 2007, 11:47 PM

SOHC is better than DOHC......?
r u kidding me.......
than what is the perpose of having the extra cam.....

should be higher FC where u need to pull 2 cam together...

never said that. both have their pros and cons. read the posts properly, he was asking the difference between SOHC and DOHC, not which is better.

if indeed DOHC is better than SOHC just because of the twin cams, tell me why top carmakers are still using SOHC instead of sticking with DOHC altogether.

answer is, neither one is better than the other per se. they have their pros and cons.

This post has been edited by nerd: Sep 8 2007, 11:55 PM

err ... mind stating the pro's and con's of SOHC and DOHC ? Im kinda curious , but when i read wikipedia , i get confused ... i dont understand a thing . hehe . thanks .

the cam is the thing that control the valves and the valves control the input of air and fuel into the engine.......so clearly all the V type engine nowadays must have more than one cam to control the valves.....



back on the topic, a SOHC 16 valve engine would have better torque on the low end where the DOHC valvetrain's weight results in lower torque. But at high engine speeds, the 16 valve DOHC engine's peak torque and horsepower would be greater. That's the trade-off. With the amount of valves being equal, SOHC has better low-end torque because the valvetrain package is lighter while DOHC has better top-end power......

i agree to what u say, i personally exprienced both 4g93 SOHC and campro DOHC, the pickup in the 4g93 SOHC is marvelous

To sum it, I guess it can be said that SOHC is for high torque @ low rev = City driving
While DOHC is for high power = spirited driving...

vios must use DOHC due to VVTi where it varies the cam timing for intake n exhaust since VVT-i = continous VVT
i might be wrong

what is V type engine

like v6, v8 v10 and v12 lor

Who said SOHC has no power? The most powerful RB engine in Australia is a hybrid SOHC RB30 producing 750hp. Mind u... even those humongous muscle power engines (above 5L) are SOHC in V8 configuration.

ooooh, the piston configuration paiseh paiseh
btw, how come Naza Ria having Quad cam

I'm not saying that SOHC has no power... An engine that does not produce power is useless in a car...
It's just that DOHC produces more power than SOHC...

it can be done but the setup is more complex and more cost involve......

Well, playing with performance ain't cheap to begin with unless u are into auto saloon...

even most mercedes benz engine is sohc, lol

Quad-cam is just a gimmick la... it is two 3-pots engine mated together with 1 crank.

There are people who mated two Hayabusa engines together producing a V8 capable of revving beyond 10000 RPMs. The cost? Don't ask...



Best part is... it about the same size as a typical 4-pots engine and can be configured in FF or FR. I would love to shove that engine into my old car... some day... if it doesn't cost the same as typical Damansara apartment...

This post has been edited by acbc: Sep 9 2007, 01:39 AM

carmakers built car gain maximum profit......more cost mean higher price and less buyer.......less cost mean lower price and defenitely more buyer......

ooo, if mating 3pots engine with quad cam config vs V6 dohc, which generally produce more power?
all i know is naza ria is super fuel guzzler

SOHC and DOHC both also same technology lar.. So why argue?
The only different is the valve number in DOHC configuration is double the valve in SOHC configuration. Manufacturer can built and claim what they wanted, but DOHC was a quick way to achieve better output and efficiency that SOHC couldnt reach at high~max RPM.

Initial D give a very good example when Takumi tried the SOHC version of AE85. At high~max RPM, the engine output/efficiency actually drops while DOHC able to compensate it. I wouldnt go as far as saying DOHC will eventually have better output or vice versa, lets just said both will give more or less the same power at its most efficient period. In fact, I do feel easier to redline with my Vios compared to my mom City VTEC.

Conclusion...

For more power at mid-high rev ranges, take DOHC.
For fuel economy and instant power at low rev ranges, take SOHC.

However, some people added turbo to SOHC engine to compensate for the lack of power at mid-high rev ranges. I know of someone who BOT onto a stock standard 4G92 Proton engine and easily tapau Campros and even stock GSR 4G93T (all manual) in 400m track.

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Added on September 9, 2007, 9:16 amFrom Wikipedia...

"Due to the odd number of cylinders in each bank, V6 designs are inherently unbalanced and can benefit from some auxiliary counterbalancing. A V6 is basically two straight-3 engines running on the same crankshaft, and since the straight-3 suffers from a dynamic imbalance which causes an end-to-end rocking motion, the V6 also suffers from the same problem. Unlike the V8, the V6 cannot be laid out so that the vibrations from the two banks cancel each other or can be offset by counterweights on the crankshaft. This vibration is particularly bad in V6s derived from V8 engines with a 90 degree angle between cylinder banks. As a result, V6s can develop significant odd-order harmonic crankshaft vibrations, which can be counteracted by the use of a heavy duty harmonic damper to avoid possible crankshaft failure at higher engine speeds. These vibrations can be reduced significantly by using more sophisticated crankshaft designs, and can be eliminated completely by adding a balance shaft. Unlike a straight-4 engine, which requires two balance shafts rotating in opposite directions at twice crankshaft speed to cancel its vibrations, a V6 needs only one rotating at crankshaft speed, which can be nestled between the cylinder banks in an overhead camshaft design.

Six-cylinder designs are more suitable for larger displacement engines than straight-4s because the power strokes of pistons overlap. Since each power stroke lasts 180 degrees of crankshaft rotation, while a new piston starts its power stroke every 120 degrees, there are 60 degrees of overlap on each stroke in which one piston is finishing while the next is starting. This results in a smoother delivery of power than a four cylinder engine, in which each piston must come to a complete stop before the next piston commences its power stroke.

Modern computer-aided design (CAD) techniques allow modern V6 engines to be designed to have far fewer vibration problems than older engines had, which is a major reason for their increase in popularity in recent years. As a result, V6 engines are generally used in mid-range cars where a big straight-4 would have too much vibration, and a V8 would be too large and expensive for the market."

This post has been edited by acbc: Sep 9 2007, 09:16 AM

the piston arrangement its like V shape.. There are also flat engine which also known as boxer engine.

This post has been edited by kevinlim001: Sep 9 2007, 06:17 PM

4 IN-LINE is a V engine???? then y not name it V4 just like V6,V8 or V12 but call it 4-inline?

i think he typo there lar... 4 inline is straight not V

DOHC engine has an additional valve for intake and exhaust per cylinder. So a DOHC can achieve the power compression ratio faster, that will ignite and push down the piston, and drives the crankshaft which will then be delivered to the wheel. So a DOHC will have more FC compared with SOHC.

whoa..me din knw sohc engines were so powerful...

hmm..the vtec city is a sohc car??

Is it possible to have a single overhead camshaft for a V engine? Dont think DOHC engines must have more than 2 ports per cylinder. The old ALFAs have Double cams but was still using a port for intake and a port for exhaust.

inline 4 is known as straight 4, not V4

examples of straight 4 :

mitsubishi 4g9x, 4g6x engines, denotated by the number 4 in front of each engine
porsche and subaru engines, mostly are boxer based engines, otherwise known as flat engines
V4 engines are generally noticed in the lancia delta integrale, V6 in the perdana and V8 in the GM, ford muscle cars, V10 in the M5 and V12 in the mercedes benz
rotary are pistonless engines, based on its wankel setup
W setup is a combination of two V engines, that form into one

isn't that what i said, minus the elaboration?

I was wondering...does a DOHC V6 and higher car engine actually has one cam driving all the valves in each block? That means like one cam controlling intake and exhaust valve?

read the bolded parts carefully and you'll answer your own question