SOHC vs DOHC

[VoLcAnO]

Hi guys, real noob abt cars so i had to ask some silly qns. Do bear with me..

 

I heard SOHC cars are basically like 2 stroke bikes that requires higher maintainance. Izzit true?

 

Hopefully with this thread i can understand more abt SOHC and DOHC .. will appreciate all the comments.

[fmx]

no way dude, cars are 4stroke combustion cycle.

 

the difference between sohc and dohc lies in the cam shaft, sohc having single cam gear but dohc using double cam gear.

 

this is the basic difference without getting into the technicalities.

[VoLcAnO]

Any diff in maintainance? Or performance? Or wear and tear?

[GerardSantaCruz]

i hijack your thread. what about rotary engine? compared to "normal" engine?

[ali_baba]

sohc which is more suitable for city driving, and save fuel, but less power.

 

dohc is more powerful, expensive than sohc. fuel drinker as compare to sohc.

 

i might not be correct, so do correct me if i'm wrong.

[WildCard]

i hijack your thread. what about rotary engine? compared to "normal" engine?

 

Consumes more petrol compared to a standard piston engine.

But able to output much more power compared to its equivalent in displacement as well as physical dimension & weight.

Rotary engines are like 2-stroke engines for cars. No crankshafts, no conrods, no valves, no moving parts except the rotor itself. Also much lighter.

 

http://en.wikipedia.org/wiki/Wankel_engine

 

My fren ever wondered why a 1.3L Mazda RX8 can outgun his 1.5 modified Lancer (before he siao-siao installed a TD-04 unit)....

[NSRog]

rotary also runs hotter right?

[fmx]

Any diff in maintainance? Or performance? Or wear and tear?

 

in terms of performance, dohc has better torque when accelerating.

 

......and better performance usually leads to more wear & tear

[Kan]

so what's good about SOHC? Lancer is using SOHC

[VoLcAnO]

The new Honda Civic 1.6/1.8 is also using SOHC.. only 2 litre is using DOHC.

[xiaoxiao]

mazda using DOHC~!

[Demon]

i hijack your thread. what about rotary engine? compared to "normal" engine?

 

http://img.photobucket.com/albums/v469/udaloy/4-stroke.gif

 

http://img.photobucket.com/albums/v469/udaloy/wankel.gif

[Kan]

why SOHC when there is DOHC? Cut cost? lower price?

[sheep]

well.. 2 stroke cars sounds good if they are available.

hehehe need to put 2T though

[archenemy]

why SOHC when there is DOHC? Cut cost? lower price?

 

lower price is 1 thing...DOHC will have higher consumption....my van is SOHC...the newer model is DOHC..and the consumption is considerably higher...about 100km more for roughly every 45 litres of diesel..

 

people who dont go for performance will not fancy DOHC...no point...

[Kan]

Lancer seems to be a performance car but uses SOHC, Vios DOHC and pple say VIOS have good FC leh... confused.

 

and what is teh difference betweem Dvvti and Cvvti

[gorgonitz82]

Some terms used in valve timing

 

VVT ==> Variable valve timing is a generic term for an automobile piston engine technology. VVT allows the lift or duration or timing (some or all) of the intake or exhaust valves (or both) to be changed while the engine is in operation.

 

VVTI ==> Variable Valve Timing with intelligence, is an automobile variable valve timing technology developed by Toyota.

 

VVT-iE ==> Variable Valve Timing - intelligent by Electric motor, is developed by toyota for lexus

 

VANOS ==> (Variable Nockenwellen Steuerung) is an automobile variable valve timing technology developed by BMW in close collaboration with Continental Teves. VANOS varies the timing of the valves by moving the position of the camshafts in relation to the drive gear. This movement varies from 6 degrees of advanced to 6 degrees of retarded camshaft timing.

 

VTEC is an acronym for Variable Valve Timing and lift Electronic Control. VTEC is a valve train system developed by Honda to improve the volumetric efficiency of a 4-stroke internal combustion engine. This system uses two camshaft profiles and electronically selects between the profiles.

 

i-VTEC ==> intelligent-VTEC, introduced continuously variable camshaft phasing on the intake cam of DOHC VTEC engines.

 

MIVEC ==> Mitsubishi Innovative Valve timing Electronic Control system, is the name of a variable valve timing engine technology developed by Mitsubishi Motors. MIVEC, as with other similar systems, varies the lift of the valves by using two different camshaft profiles.

[gorgonitz82]

Some types of common automotive transmission

 

Manual transmission => clutch and movable gear selctor

 

Automatic transmission => automatic gear box that change gear ratios automatically as vehicle moves

 

Tiptronic => type of discrete automatic transmission from Porsche. Allows driver to override auto mode by moving the shift lever into tiptronic shift gate with up or down. Tiptronic design is implemented using a torque converter like auto transmissions. It is not computer controlled clutch-manual transmission like semi-auto.

 

Semi-automatic transmission => clutchless manual transmission or automated manual transmission or paddle shift gearbox. Uses electronic sensors, processors and actuators to do gear shift on command from driver.

 

CVT, Continously variable transmission => change the gear ratios over a range rather than between set gear ratios, hence providing an infinite number of possible gear ratio.

 

IVT, infintely variable transmission => a specific kind of cvt. IVT has an infinite range of input/output ratios in addition to its infinite number of possible ratios. This implies that its range of ratios includes a zero output/input ratio that can be continuously approached from a defined "higher" ratio.

[spy622]

Consumes more petrol compared to a standard piston engine.

But able to output much more power compared to its equivalent in displacement as well as physical dimension & weight.

Rotary engines are like 2-stroke engines for cars. No crankshafts, no conrods, no valves, no moving parts except the rotor itself. Also much lighter.

 

http://en.wikipedia.org/wiki/Wankel_engine

 

My fren ever wondered why a 1.3L Mazda RX8 can outgun his 1.5 modified Lancer (before he siao-siao installed a TD-04 unit)....

 

a TD-04 wif mods on the 1.5 glxi might only come on par wif a stock RX8 or a slightly beefed up 1..but nvtheless running along side wif other Glxi n cars of the same range things r much different..of coz it also very much depends on wat other performace mods u got install to make the things work in a better package

[archenemy]

lancer is a performance car??

 

errr..i dont think so...

 

lancer evolution yes lah...

[natgw]

lancerlution

[redbeacon]

VTEC is an acronym for Variable Valve Timing and lift Electronic Control. VTEC is a valve train system developed by Honda to improve the volumetric efficiency of a 4-stroke internal combustion engine. This system uses two camshaft profiles and electronically selects between the profiles.

 

How about VTEC for bikes?

 

I've got some questions for ya:

 

1. Is VTEC's design concept universally same across all vehicles. And if it is,

2. Would it be "electronically" actuated on a bike, such as a Super 4 -- or does the camshaft move mechanically to "switch" profiles.

[fmx]

Lancer seems to be a performance car but uses SOHC, Vios DOHC and pple say VIOS have good FC leh... confused.

 

mostly because fuel consumption is not solely dependent on whether its sohc or dohc. other factors make a difference too.

 

a better comparison would be a sohc versus dohc version of the same make and model. but then again, no manufacturer would put this option in the market.

[archenemy]

a better comparison would be a sohc versus dohc version of the same make and model. but then again, no manufacturer would put this option in the market.

 

well...the new opel combo is a 1.7 CDTI...friends driving that is averaging 600 per full tank..

 

mine is the slightly older version, 1.7 DTI...getting around 750km per full tank...

 

almost the same specs...weight...engine capacity...just that theirs is a euro 4 common rail engine, while mine is a slightly older euro 3...

[boofeng]

How about VTEC for bikes?

 

I've got some questions for ya:

 

1. Is VTEC's design concept universally same across all vehicles. And if it is,

2. Would it be "electronically" actuated on a bike, such as a Super 4 -- or does the camshaft move mechanically to "switch" profiles.

 

i typed a lot but always type "backspace" by mistake. i give up le. so just short answers for you (a bit simplistic sorry but i'm tired)

 

1. in general yes. in specifics no.

 

2. for bikes, usually mechanical since triggered by rpm, no need make things complex. for cars or advanced bikes with "smart" timing, maybe electronically mediated to factor in other variables. something like passing all data through an electronic brain (e.g. ECU).

 

3. many other systems exist to improve engine versatility and performance, ignition timing changes (CDI/ECU maps), changes in intake and exhaust lengths/shapes (2-stroke exhaust power valve, 4-stroke exhaust valve e.g. EXUP, 4-stroke intake systems, e.g. TDM 900's airbox, or MV Agusta's trumpet intakes; think '07 R1 has something similar too... not sure)

 

 

 

btw, from what i know, the main difference between SOHCs and DOHCs are that DOHCs use much smaller, lighter components, e.g. smaller cams actuating smaller valves. and these lighter components, with less inertia, spin up faster (revs up faster), and can actually withstand spinning at higher speeds (higher max rpm), which in turn equates to more power since power = revs x torque.

 

also it might be easier to design/tune an engine with independent intake and exhaust timings (DOHC, one cam for each) than those with integrated intake and exhaust timings (SOHC uses one cam to control both).

 

as a result, SOHC engines in general make less power (due to less revs), make more power low down (since it won't be tuned for top-end power, as it doesn't rev anyway), consume less fuel (less fuel for less power) than an equivalent DOHC. of course there're many other factors to consider but this is a general trend i see in bikes.