SOHC is better then DOHC

[najibkl]

What i alwayz "kena"...My car is SOHC, alwayz kena tapau at first gear with kelisa. But now, goodbye kelisa.

So, the point is DOHC much pick up than SOHC ler

 

[NukeeZoid]

Originally posted by najibkl@Feb 22 2005, 14:55
What i alwayz "kena"...My car is SOHC, alwayz kena tapau at first gear with kelisa. But now, goodbye kelisa.

So, the point is DOHC much pick up than SOHC ler

you running a DOHC head now??

i was also thinking about this upgrade...to change my head from the SOHC to the DOHC one....im running a satria 1.6 as well...

thats why im wondering whether its worth the cost. changing the head like that would cost about RM900-RM1000...

if i add another RM500 more i can port and polish my engine which would gain me about 8-10BHP....

is the cost for head swapping justified? :blink:

 

[AccordRacing]

i think SOHC for FC n nice pick up at city area(cause SOHC is lighter)
DOHC for performance n FC at high speed compare with SOHC

 

[lozo]

from my understandings
DOHC engine is much more refined, giving it more hp and it can withstand high revs.
SOHC is lighter, less components..therefore being light, it provides good response esp. in the low rpm's

 

[reddice]

update us if you have done your swap to DOHC head..i also wanted to swap..but must see first la..more benefit or not..if same..better use SOHC..

p/s : but they say,using dohc "jimat minyak" la.and more power to..thay say la... :D :D

 

[ettk2003]

hi

previously i was running a 4G92 sohc, with port & polish head and forged piston too...then i did the dohc conversion as well...and what i found is that for the pick-up its more or less the same but at high rpm i can feel slight increase in hpower...

might need a ecu that is for dohc to fully utilize the new head...i didnt do that so i cant tell u the result..

but the other things i found is that with dohc, the engine is much more quiet, and the sound from the exhaust is much nicer....also looks good with a dohc rather than sohc inside the engine bay :D


cheers

 

[moppy]

Originally posted by ettk2003@Feb 23 2005, 10:46
hi

previously i was running a 4G92 sohc, with port & polish head and forged piston too...then i did the dohc conversion as well...and what i found is that for the pick-up its more or less the same but at high rpm i can feel slight increase in hpower...

might need a ecu that is for dohc to fully utilize the new head...i didnt do that so i cant tell u the result..

but the other things i found is that with dohc, the engine is much more quiet, and the sound from the exhaust is much nicer....also looks good with a dohc rather than sohc inside the engine bay  :D


cheers

Agree too, look nice and more queit that before.

Mine is 4G92 did a conversion, with 4G91 Head. I was in dilema of swapping the head for so long and finally I did it. I hv studied a lot of the 4G91 head and 4G93 and gather up the information. There's a little different between this 2 head.

1) The cams profile different
2) Valve spring - 4G93 is about 5mm higher
3) The valve porting size, needn't to say the smallest is 4G91
4) The piston head, 4G93 is bigger so obviously can see which is 1.5 and which is 1.8.

I hv done a polish but not porting, my mechanics advice me cos might occur pick up power lost. Comparison 4G91 DOHC n 4G92P, the power output is more or less the same therefore 4G92P is ideal to use 4G91 head. His personal opinion said 4G93 head is bigger port as a result might loose a lot of pick up power compare using 4G91.

After the conversion, yes I dmit I loose some pick up power but not much loosing. Anyway still notice the different, at around 3200 rpm I could feel the power is in control until I rev. 7000 rpm without any problem. My car is auto, but normally I rev. until 6000 rpm.


Another case, my brother driving a 4G93P SOHC and he swapped to DOHC. He was conned by a foreman (in Shah Alam, dun go there anymore) said that swapped with 4G93 DOHC. That moron foreman took out the EGT as a result my bro. car disposed a lot of carbon. Then finally I took his car back to my mechanics and overhaul the head. At the end everything restore to be original with EGT and DOHC head. The head finally being ported back to 4G93P valve porting size except the cams. Can't do anything about it cos can't find a 4G93 cams.

The results, my brother car suffer a serious problem at the pick up but has a good top end. Very good top end, and at 120km/h the car still can drop gear. By the way it's auto as well.

The above result might not be the same as in different car and just my bro. n my experience. There are a lot of reason why this has happen.

 

[yiheng85]

read from a book..merc went back to using 3 valves because they wanna incrase fuel efficiency...:) the theory behind it i dunno :P

 

[ettk2003]

ya...agreeded with what moppy said...

my friend did the same conversion with me at the same time, but he was using a 4G93T head whereas i was using a 4G91

we tested both cars after the conversion...and his car is a bit on the slow side in term of pick-up...it takes a while to kick in

cheers

 

[SloMo]

still researching here... what kind of DOHC head suits 4g18p's block?... can 4g15 DOHC mivec from the new lancer fit in?... any other option?...

 

[softmuffin]

Alright.. For who has already done this SOHC to DOHC.
Care tell the the workshop name: address and phone..
thanks..

 

[xin]

4G92P change to 4G93 block is consider still SOHC or DOHC ?

i heard changing like this will get higher compresions ..izzit worth it ?

 

[ultimate_satria]

if i'm using 4G13, willing to convert to DOHC,
which engine head shold i use?

any coment? :(

 

[fstr]

ultimate satria, no need swap head lar bro.. change ur valve springs can edi...cos urs is carbie, same like mine.

 

[kinki_kidz®]

Originally posted by fstrader@Apr 17 2005, 12:57
ultimate satria, no need swap head lar bro.. change ur valve springs can edi...cos urs is carbie, same like mine.

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change valve spring..whats the effect on this?
my fren advices me to tune my carbie wira's valve as well :/

but he havent tell me what improvement i can see

 

[ZR650]

Originally posted by taqu@Feb 21 2005, 13:21
The more complete question is "4G92 12-valve SOHC convert to 4G92 16-valve DOHC, pros/cons?" :) Coz there're 4-cylinder engines having 16 valves but only use SOHC eg Waja engines or some Honda engines.

About pros & cons of 12-valves (3 valve per cylinder) vs 16-valves (4 valve per cylinder), I copy-paste this statement from Autozine :

A typical 2-valve engine has just 1/3 combustion chamber head area covered by the valves, but a 4-valve head increases that to more than 50%, hence smoother and quicker breathing. 4-valve design also benefit a clean and effective combustion, because the spark plug can be placed in the middle.

4 valves are better to be driven by twin-cam, one for intake valves and one for exhaust valves. Honda and Mitsubishi models prefer to use sohc, driving the valves via rocker arms like the aforementioned Triumph. This could be a bit cheaper, but introduce more friction and hurt high speed power. Therefore the sportiest Honda and Mitsubishi still use dohc.

Hmm it is correct to say that generally DOHC engines have abit weaker low-end compare to SOHC (coz DOHC results in larger intake area resulting in slower air flow) , but most DOHC engines have smaller-diameter & curved intake manifold to improve those low-end torque (I think this also applies to 4G92), so u won't notice that low-end loss, on the other hand this may effect hi-end power, but since DOHC have more potential for hi-revving than SOHC, this is OK.

So, gor for it dude :)

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Bro, 4G92P SOHC is not 12-valve la, it's 16. ;)

 

[shammam]

hi all....

another one user of 4G92 SOHC and planning swap to DOHC using 4G91. already sent the head to engenering shop for adjustment at distributor. After doing some study i also decided to use 4G91 head insted of 4G93. Anyway still can't give a lot of comment since my mechanic will do this by next week....

This engenering work cost me around rm200 to rm250 just for engineering work at distributor only (used back 4G92)...is it consider cheap or expensive??? ;)

Hoping that the result might be the same as Moppy....

 

[lozo]

Originally posted by yiheng85@Feb 23 2005, 13:47
read from a book..merc went back to using 3 valves because they wanna incrase fuel efficiency...:) the theory behind it i dunno :P

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with 3 valves, the air will create a turbulent effect in the combustion chamber. and improves the combustion at the low-mid revs. why merc uses 3 valves? most of merc owners only revs two thirds of the entire rev range thus by using 3 valves gives better driveability(fuel economy). same also with honda D15 engine.