Comments on: SOHC vs DOHC Valvetrains: A Comparison

By: Saibal Das

Saibal Das — Thu, 01 Oct 2009 07:26:06 +0000

Being a marine engineer i always work with pushrod-rocker type engine( medium speed diesel engine) or hydraulically operated exhaust valve( slow speed diesel engine) and i donot have any exposure to petrol/gasoline engine. my question is there any cam follower in the dohc system and how the valve clearance is adjusted? how valve timing is adjusted?

By: vikas

vikas — Fri, 11 Sep 2009 13:46:11 +0000

kindly advice fire 1.4 starjet in linea is better than ford duratech technically or if compare fire with duratech and i vtech which is best

By: KK

KK — Sun, 16 Aug 2009 06:53:41 +0000

Hey!!!! This is a really good piece of info. Really informative. Keep up the goodwork…..

By: Frank

Frank — Sun, 09 Aug 2009 16:32:58 +0000

Thanks for the info. But for a layman …all I want to know is ….the new 2009 Honda Accord 2.0 VTiL has a SOHC configuration while the older generation 2005 Honda Accord 2.0 iVtec has a DOHC configuration . Just tell me which is better !!! Thanks .

By: Frank

Frank — Sun, 09 Aug 2009 16:31:52 +0000

Thanks for the info. But for a layman …all I want to know is ….the new Honda Accord VTiL has a SOHC configuration while the older generation has a DOHC configuration . Just tell me which is better !!! Thanks .

By: Cicma

Cicma — Fri, 07 Aug 2009 23:27:59 +0000

Low end and High end is referred to the RPM’s, that means to low RPMS (a soft drive) or high RPM (accelerating to the top), so when you are a high speeds your engine will need be in high end (High RPM’s) to maintain the power (velocity) that’s when a DOHC is better. Of course that was just an example, also depends of the engine configuration; so if you like rev your car a top that means drive fast with fast shift changes its better a DOHC, but if you drive smooth in the city you will no need a DOHC and with SOHC would be enough, the difference could be more noticed, as said, in how many valves per cylinder the engine has

By: frank

frank — Sun, 19 Jul 2009 15:21:39 +0000

SOHC has better low-end power, DOHC has better high-end power and overall maximum power.

what do you mean by low end power and high end power ? from your conclusion DOHC is better ??

By: ken nguyen

ken nguyen — Thu, 21 May 2009 22:25:15 +0000

I just visited a Dodge dealer. I saw the Grand Caravan I like very much, but one of the main differences between its engine and the toyota minivan is the SOHC (toyota van has DOHC). I wonder if this makes the Toyota more reliable van, but after reading your article, I understand this is not the reason why Toyota is more reliable. Thank you!

Ken N.

By: Yantho

Yantho — Sat, 11 Apr 2009 08:27:45 +0000

hey paul, i’ve had a mazda 323f 1.6L 16v dohc for ebout 250000kms, now i’ve bought the exact same car but in a 1.8L grsi 16v dohc version at around 175000kms,
now i’m looking to transplant some parts from my old one, but i can’t quite get my finger around that grsi thingy sticking on to the back end like ted kennedy on a hogie, what does it mean, and is it possible to somehow supercharge the engine (turbo)? as you have no doubt guessed i know jack about car engine’s but i know what i like so can anyone help, some tips on how to do this, and what grsi stands for?

cheers,
Y

By: Charlie Bader

Charlie Bader — Tue, 07 Apr 2009 04:50:40 +0000

You left out the biggest reason for 4 valves/cyl- valve area. The total area of the valves is much greater because the non-valve area is smaller with 4 valves. It’s like the jar of marbles problem- you can fit more in if the particles are smaller.

By: pranesh

pranesh — Sat, 21 Mar 2009 15:29:18 +0000

its great dude.. can u give more detail over the complication of having 4 valves in sohc and explain me the example 4G92P which you have used…
if possible post to my mail…please…..great work

By: Susan Loving

Susan Loving — Tue, 17 Mar 2009 19:07:24 +0000

Paul,
I may be stupid on all of this but can you just tell me which one would be best for normal driving on a 1991 Dodge Stealth RT 3.0 5 speed.
Susan

By: maxmatterz

maxmatterz — Thu, 17 Jul 2008 11:40:02 +0000

Between DOHC and SOHC which one is more fuel saver?

By: Honda Man

Honda Man — Fri, 30 Dec 2005 08:04:26 +0000

Wait a minute Paul, are you saying that the City 1.5 VTEC actually just shuts one intake valve at low rpm, and have all intake valve operating at higher rpm? What about valve timing and lift? Does that stays the same or does that varies too?

By: Prometheus

Prometheus — Sat, 12 Nov 2005 11:18:55 +0000

These were better times in your blog Paul.. Less flaming, more information. Time to change all that.. You have to make the change

By: Vince

Vince — Sun, 06 Nov 2005 06:20:35 +0000

Just a note, I realized I placed the Si model in my questions to what may seem, as a SOHC. I know it is a DOHC, but I just wanted to know the comparisons results or theory between these 2 DOHC engines just as well as the SOHC vs. DOHC results.

By: Vince

Vince — Sun, 06 Nov 2005 05:43:57 +0000

Hi Paul,
I found this Blog on SOHC vs. DOHC to be very informative. I just have a question or two concening today’s technology and your information in relation to the new 2006 Honda Civic (Si). Obviously changes in technology are always changing things, and create new alternatives.
Now, if you compare two vehicles with the same amounts of valves, the new 2006 Honda Civic’s (Si) SOHCs with it’s systematic timing and control in valve configurations (i-vtec), to let’s say the Scion tC’s DOHC (possibly w/o a supercharger), same engine used on the Toyota Camry, Would these new configurations change the overviews (rules)?
According to your explanation and my limtied knowledge, the Civic (Si) would probably beat the tC in a 1/4 mile but not in the long-run. I cannot say I understand the Si’s engine configurations completely, but Would these rules still apply in low-end torque, high engine speeds, peak torque, and horsepower?

By: Jimmy

Jimmy — Thu, 06 Oct 2005 20:35:31 +0000

Let’s say a race a DOCH VTEC with my SOHC 16 valves, you think i will bet the DOCH VTEC? What is the difference what are my advantages.

By: Mohd Fairuz

Mohd Fairuz — Sun, 11 Sep 2005 09:41:27 +0000

I’m thinking of getting a Honda Accord 2.2 with auto transmission.. but I don’t know what to choose.. sohc vtec or dohc vtec.. the salesman told me that if I’m going for auto, then dohc will make no big difference over the sohc.. so sohc is a wise choise.. is that true?

By: Paul

Paul — Sun, 28 Aug 2005 02:39:22 +0000

sakaic: yup, that was what i was trying to say in my blog post. honda’s 1.5 vtec used in the jazz and city vtec actualy works like the T-VIS you mentioned.

By: sakaic

sakaic — Sat, 27 Aug 2005 20:06:18 +0000

I feel there is something small to clarify and I’m sorry if I unintentionally offend anyone.

The main reason why there is a difference in torque between the 2 engines is not because of the no. of camshafts but the number of valves.

When you have 2 valves, the intake pressure at low revs is actually higher cos the intake port is smaller and that gives more pressure. Thats why at one time toyota 16v heads came with T-VIS. it shut one of the 2 intake ports per cylinder to increase intake speed at low revs. Higher pressure increases intake speed resulting in more air.

Nowadays, they put a medium sized port size to reduce this problem.

By: bangau

bangau — Fri, 24 Jun 2005 13:48:47 +0000

Good job!!!!! We always have some idiots who would thrash Proton for using SOHC engine, but Honda is also using it but goes scot free without any bashing.

Anyway, if you are referring to the Savvy and MyVi, it wont be a fair comparisons because the SAvvy, eventhough has a lower hp rating, will still run circles around the MYVI since the MYVI is a class larger and heavier. I’ve tried both cars back to back.

By: Paul

Paul — Thu, 23 Jun 2005 07:11:32 +0000

Ezmil: the honda city and jazz are using SOHC, and only has 2 valves per cylinder for the i-DSI versions. they couldn’t fit more valves per cylinder because of the dual sparkplug design. takes up alot of space.

the VTEC SOHC 1.5 in the honda jazz vtec uses a 12V/16V design where there are 4 valves per cylinder but only 3 valves work at low RPM and all 4 valves work at high RPM.

By: maniam

maniam — Thu, 23 Jun 2005 07:06:48 +0000

macam tu sesuai ler savvy pakai SOHC emmmm …tak ler ketinggalan cam tu

By: Ezmil

Ezmil — Thu, 23 Jun 2005 07:00:46 +0000

Very good explaination. It is interesting to know that Honda City and Jazz are using SOHC config to their engine, and nobody complains about it

By: Paul

Paul — Thu, 23 Jun 2005 03:48:56 +0000

karheng: 4G92P… the P stands for Proton! LOL! It’s a normal single cam 1.6 lar… not Mivec. 4G92 engine code as far as I know could mean 3 engines… 4G92 SOHC, 4G92 DOHC and 4G92 DOHC Mivec

By: karheng

karheng — Thu, 23 Jun 2005 03:38:09 +0000

hmmm…just hit me…ur car running on a mivec? I know it’s 4G92 but i duno where ur P came from..ehhehe

By: edw

edw — Thu, 23 Jun 2005 02:05:33 +0000

Good job Paul.
Never did understand this till now, with more and more car going to DOHC, I always think DOHC is better then SOHC… but it become clear now.

By: JAWA

JAWA — Wed, 22 Jun 2005 15:04:16 +0000

thik = think
felp = help
hehe… sorryyy, speed typing, but not speed driving..

By: JAWA

JAWA — Wed, 22 Jun 2005 15:01:08 +0000

waaah… barulah clear skit!!! hehehe good work Paul!!! i did my automotive subject in those univ day, but in arabic country in the middle east the abriviation always wind my head in pening kepala… hey, i thik you should post these article of yours to the univ or college that major in auto as a side reference, it will felp a lot to student to understand more easy!!! good work Paul!!!