SOHC vs. DOHC


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Canew

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#1
Hello everyone,

Another motoring related question from me again. :)

Q: What is the advantages and disadvantages of SOHC and DOHC?

I see the trend (I am more interested in the 1.5/1.6 liter car segment) of vehicles utilising the DOHC design. But there are still cars (eg.: MITSUBISHI Lancer) that are still using SOHC (c/w CVT version) technology. If DOHC is better, why would so cars using the SOHC? Hope that some knowledgeble CS-ers will be able to help me shed light on this matter. :)

TIA.
 

jeryltan

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SOHC.. Lower fuel consumption.. Lower inertia.. And most importantly, cheaper to produce :)

DOHC.. Better overall power, especially high end.. Higher fuel consumption.. More modification potential (If it applies :))

BTW, if possible, give CVT a miss..

Canew said:
Hello everyone,

Another motoring related question from me again. :)

Q: What is the advantages and disadvantages of SOHC and DOHC?

I see the trend (I am more interested in the 1.5/1.6 liter car segment) of vehicles utilising the DOHC design. But there are still cars (eg.: MITSUBISHI Lancer) that are still using SOHC (c/w CVT version) technology. If DOHC is better, why would so cars using the SOHC? Hope that some knowledgeble CS-ers will be able to help me shed light on this matter. :)

TIA.
 

eyes

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#3
SOHC, single overhead cam are more fuel efficient then DOHC, D = dual = 2 cams.

If you are into performance thing, ie. playing "pick-up", racing etc, DOHC is good. If you wanna save your life from being sucked (& i mean really being sucked) by the petroleum companies, then SOHC is the way to go.

Imagine the difference avg. of 10l / 100km on SOHC and 15l on DOHC. (this is avg. figures)

Buying a car is a lifeliong commitment esp in S'pore. Think wisely on what you want.
 

Canew

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jeryltan said:
SOHC.. Lower fuel consumption.. Lower inertia.. And most importantly, cheaper to produce :)

DOHC.. Better overall power, especially high end.. Higher fuel consumption.. More modification potential (If it applies :))

BTW, if possible, give CVT a miss..
Thanks jeryltan, but care to elaborate more on the reason why CVT should be avoided? I like the smooth pick-up of CVT.
 

markccm

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Del_CtrlnoAlt

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markccm said:
really?

my friend's Mit Lancer which is an SOHC is getting 10km/l

my Vios which is a DOHC is getting 14km/l.

The overhead cam shafts is a mechanical shaft that opens & closes the inlet & outlet valves via the car's ECU.

http://auto.howstuffworks.com/question562.htm
http://auto.howstuffworks.com/camshaft.htm
i think it depends on the way u drive as well... ecu timing... alot... body weight etc...
 

markccm

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Del_CtrlnoAlt said:
i think it depends on the way u drive as well... ecu timing... alot... body weight etc...
i rev quite alot.
to 5,000rpm during launch.

most Vios owners get an avg of 14km/l to 16km/l.

anyway my driving pattern is similar to my my friend who is driving the Lancer.
but of coz the Lancer has a heavier chasis as compared to a Vios.
 

jeryltan

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The CVT gearbox is weak.. I used to drive the Civic EK3 VTi, changed gearbox twice over 7 yrs.. My current Civic ES8 VTi, just changed CVT gearbox at 3 yrs.. I've also have friends driving Fit / Jazz who's had problem with their CVT, including the Mitsubishi Lancer CVT..

Canew said:
Thanks jeryltan, but care to elaborate more on the reason why CVT should be avoided? I like the smooth pick-up of CVT.
 

Del_CtrlnoAlt

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markccm said:
i rev quite alot.
to 5,000rpm during launch.

most Vios owners get an avg of 14km/l to 16km/l.

anyway my driving pattern is similar to my my friend who is driving the Lancer.
but of coz the Lancer has a heavier chasis as compared to a Vios.
u drive manual ar? :thumbsup:

currently rediscovering the usage of clutch, previously on a 6 speed clutchless semi auto/ manual... now 'downgrade' to 5 speed manual with clutch no abs, i find that by downshift depressing the clutch continuously, can slowdown the car yet maintaining the highspeed than using brakes... can't do that with an auto car...never... ;p

anyway, i newbie driver... :sweatsm:
 

Del_CtrlnoAlt

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jeryltan said:
The CVT gearbox is weak.. I used to drive the Civic EK3 VTi, changed gearbox twice over 7 yrs.. My current Civic ES8 VTi, just changed CVT gearbox at 3 yrs.. I've also have friends driving Fit / Jazz who's had problem with their CVT, including the Mitsubishi Lancer CVT..
how much is a gearbox for honda? i scared expensive... my previous car gearbox was quoted about 18k (siao rite... more expensive than the car price...)
 

jeryltan

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Different thing.. Ok, if I may be blunt :)

Mitsubishi is not known for making efficient engines.. We should compare SOHC and DOHC from the same manufacturer..

The 2 manufacturers with the most efficient engines are Toyota and Honda.. Also, your Vios is also light <1ton which is also the reason why it's efficient..



markccm said:
really?

my friend's Mit Lancer which is an SOHC is getting 10km/l

my Vios which is a DOHC is getting 14km/l.

The overhead cam shafts is a mechanical shaft that opens & closes the inlet & outlet valves via the car's ECU.

http://auto.howstuffworks.com/question562.htm
http://auto.howstuffworks.com/camshaft.htm
 

Del_CtrlnoAlt

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jeryltan said:
Different thing.. Ok, if I may be blunt :)

Mitsubishi is not known for making efficient engines.. We should compare SOHC and DOHC from the same manufacturer..

The 2 manufacturers with the most efficient engines are Toyota and Honda.. Also, your Vios is also light <1ton which is also the reason why it's efficient..
VTI is a SOHC rite? den SIR is DOHC rite... how much diff is that? think if we compare that will be easier, cos using same chassis... btw wats ESI then? but den again, VTI max 1.8, SIR 2.0
 

markccm

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jeryltan said:
Different thing.. Ok, if I may be blunt :)

Mitsubishi is not known for making efficient engines.. We should compare SOHC and DOHC from the same manufacturer..

The 2 manufacturers with the most efficient engines are Toyota and Honda.. Also, your Vios is also light <1ton which is also the reason why it's efficient..
yup, but Mit Lancer was mentioned 1st, so i continued to use it as a comparison.

cannot think of other SOHC cars.
maybe Hyundai?

think of it, Honda makes powerful cars with DOHC, yet fuel efficient.
hehe ;)
 

jeryltan

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Yes.. EK VTi is SOHC and EK SiR is DOHC.. EK VTi is 1.5L, SiR is 1.6L..

EK VTi, average fuel consumption ~14km/L
EK SiR, average fuel consumption ~11km/L

EG ESi is the older '92~'95 model.. It's 1.6L SOHC..

I think the 1.8L and 2.0L model you referring to is the new Civic FD.. I would love to get the 2.0L Manual model, if I could sell my car without topping up to finance ;(

Del_CtrlnoAlt said:
VTI is a SOHC rite? den SIR is DOHC rite... how much diff is that? think if we compare that will be easier, cos using same chassis... btw wats ESI then? but den again, VTI max 1.8, SIR 2.0
 

jeryltan

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Honda Civic previous model, ie. ES, is all SOHC one mah.. Even the EK VTi is also SOHC :)

markccm said:
yup, but Mit Lancer was mentioned 1st, so i continued to use it as a comparison.

cannot think of other SOHC cars.
maybe Hyundai?

think of it, Honda makes powerful cars with DOHC, yet fuel efficient.
hehe ;)
 

sk.images

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Del_CtrlnoAlt said:
u drive manual ar? :thumbsup:

currently rediscovering the usage of clutch, previously on a 6 speed clutchless semi auto/ manual... now 'downgrade' to 5 speed manual with clutch no abs, i find that by downshift depressing the clutch continuously, can slowdown the car yet maintaining the highspeed than using brakes... can't do that with an auto car...never... ;p

anyway, i newbie driver... :sweatsm:
How do you slow down and maintain speed at the same time?:confused:
 

sk.images

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"Taken from the web...

Advantages to having a DOHC engine over a SOHC is that the engine has twice as many intake and exhaust valves as a SOHC motor. This makes the engine run cooler and more smoothly, quietly, and efficiently. But the downfall is that DOHC engines cost more for repairs."

Running cooler and smother is more efficient, therefore uses less petrol!
 

markccm

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#19
thats bcoz there is 2 overhead cam shafts to control the inlet & outlet valves accordingly.
of coz, via the ECU giving instructions when to open & close.

therefore giving better control & accuracy in timing.
one overhead shaft controls the inlet valves, the other controls the outlet valves.

the shafts run parallel to each other above the cylinders.
 

CYRN

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#20
markccm said:
thats bcoz there is 2 overhead cam shafts to control the inlet & outlet valves accordingly.
of coz, via the ECU giving instructions when to open & close.

therefore giving better control & accuracy in timing.
one overhead shaft controls the inlet valves, the other controls the outlet valves.

the shafts run parallel to each other above the cylinders.
The valves are mechnically linked to the engine leh. ECU got no say.

control and accuracy of the valves "opening" and "closing" are also mechnically adjusted. the term is Tappet clearance adjustment.

DOHC are so called better cuz, as mentioned, they are able to be linked to more valves.
Also the air inlet and exhaust outlet valves timings can be adjusted independently, maximising the compression in the cylinders.

Down side that it consumes more fuel.. not because it's less fuel efficient, but rather why designed for more power but dun tap the potential. And I inderstand that initially, DOHC cars got problem meeting some EU emmission standard. Now I dunnoe cus since I take up photography... no time and $$$ to dwell into cars liao.
 

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