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Helfen
Samba Member
Joined: January 19, 2009
Posts: 3450
Location: Vulcania
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 Posted: Sat Aug 18, 2018 4:08 pm Post subject: Re: DOHC vs. OHV |
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| Onceler wrote: |
| Helfen wrote: |
| Onceler wrote: |
| Don't get me wrong, I'm all for new technology as well as appreciating the old. I just find it odd that in 2018, 4 valve engines aren't ubiquitous by now, that's why I'm questioning. Too be honest I would prefer to travel to work in a automated drone aircraft, would cut commute time and I could sleep on the way, lol |
[I just find it odd that in 2018, 4 valve engines aren't ubiquitous by now.]
I was just looking at 2018 NISSAN model line. Every single car model or truck model has DOHC four valves per cylinder and VVT. With Nissan, this trend was started over 20 years ago. |
VVT is also applied to pushrods 2 valve engines, for example the ram 5.7 hemi mentioned above. Japanese usually are very mindful of material, cost/pc., and physical size usage, however in this case it's the total opposite. 2x the cams, 2x the valves, more physical size. then again, as mentioned gov't. Intervention can have strange effects |
The Chrysler Hemi VVT can only advance and retard the cam through increase lift. Nissan controls the intake cam and the exhaust cams separately. |
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Onceler
Samba Member
Joined: May 28, 2010
Posts: 1647
Location: Indiana
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| Posted: Sun Aug 19, 2018 7:43 pm Post subject: Re: DOHC vs. OHV |
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I've got nothing else, will be interesting to see what the big 3 do in the next 10 years...
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Helfen
Samba Member
Joined: January 19, 2009
Posts: 3450
Location: Vulcania
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| Posted: Sun Aug 19, 2018 7:45 pm Post subject: Re: DOHC vs. OHV |
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| Onceler wrote: |
| I've got nothing else, will be interesting to see what the big 3 do in the next 10 years... |
You know that more than half of G.M. cars as well as Ford are DOHC already. |
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Onceler
Samba Member
Joined: May 28, 2010
Posts: 1647
Location: Indiana
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| Posted: Sun Aug 19, 2018 7:51 pm Post subject: Re: DOHC vs. OHV |
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Yes, just power braked my ex-wife's 2015 v6 Camaro, fun times, lol.
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12740
Location: Western Canada
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| Posted: Sun Aug 19, 2018 8:51 pm Post subject: Re: DOHC vs. OHV |
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| Helfen wrote: |
OHV and SOHC cams use two valves per cylinder.
DOHC use two cams and use four valves per cylinder, also DOHC engines control their cam timing events depending on the RPM and load on the engine. This is what we call variable valve timing. By controlling intake cams and exhaust cams by retarding and advancing SEPARATLY we can get more torque out of the engine at lower rpm and by changing the events can get more HP at higher RPM. We also can tune the adjustable cams for better mileage. And four valves get more in and more out by volume and faster.
In the 60's some of the cam companies like Isky made mechanical advanced cams for V-8 engines, primarily for the SBC. This gave some low end torque and at high rpm it would advance the cam, problem was it advanced and retarded both the intake and exhaust events at the same time. DOHC is better because #1. 4 valves instead of two, and 2. you can control intake and exhaust valves separately for optimum HP and Torque. |
There are lots of DOHC engines that don't' have all that technology and there are SOHC engines that do. |
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Helfen
Samba Member
Joined: January 19, 2009
Posts: 3450
Location: Vulcania
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| Posted: Mon Aug 20, 2018 8:30 am Post subject: Re: DOHC vs. OHV |
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| oprn wrote: |
| Helfen wrote: |
OHV and SOHC cams use two valves per cylinder.
DOHC use two cams and use four valves per cylinder, also DOHC engines control their cam timing events depending on the RPM and load on the engine. This is what we call variable valve timing. By controlling intake cams and exhaust cams by retarding and advancing SEPARATLY we can get more torque out of the engine at lower rpm and by changing the events can get more HP at higher RPM. We also can tune the adjustable cams for better mileage. And four valves get more in and more out by volume and faster.
In the 60's some of the cam companies like Isky made mechanical advanced cams for V-8 engines, primarily for the SBC. This gave some low end torque and at high rpm it would advance the cam, problem was it advanced and retarded both the intake and exhaust events at the same time. DOHC is better because #1. 4 valves instead of two, and 2. you can control intake and exhaust valves separately for optimum HP and Torque. |
There are lots of DOHC engines that don't' have all that technology and there are SOHC engines that do. |
Lots? name them. |
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TDCTDI
Samba Advocatus Diaboli
Joined: August 31, 2013
Posts: 12858
Location: North Carolina
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| Posted: Mon Aug 20, 2018 8:53 am Post subject: Re: DOHC vs. OHV |
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| Helfen wrote: |
| oprn wrote: |
| Helfen wrote: |
OHV and SOHC cams use two valves per cylinder.
DOHC use two cams and use four valves per cylinder, also DOHC engines control their cam timing events depending on the RPM and load on the engine. This is what we call variable valve timing. By controlling intake cams and exhaust cams by retarding and advancing SEPARATLY we can get more torque out of the engine at lower rpm and by changing the events can get more HP at higher RPM. We also can tune the adjustable cams for better mileage. And four valves get more in and more out by volume and faster.
In the 60's some of the cam companies like Isky made mechanical advanced cams for V-8 engines, primarily for the SBC. This gave some low end torque and at high rpm it would advance the cam, problem was it advanced and retarded both the intake and exhaust events at the same time. DOHC is better because #1. 4 valves instead of two, and 2. you can control intake and exhaust valves separately for optimum HP and Torque. |
There are lots of DOHC engines that don't' have all that technology and there are SOHC engines that do. |
Lots? name them. |
Does '80s/'90s DOHC technology count? Because everything from VW, Mitsubishi, Toyota, & most of Honda fall into this category. 
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Everybody born before 1975 has a story, good, bad, or indifferent, about a VW.
GOFUNDYOURSELF, quit asking everyone to do it for you!
An air cooled VW will make you a hoarder.
Do something, anything, to your project every day, and you will eventually complete it. |
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Helfen
Samba Member
Joined: January 19, 2009
Posts: 3450
Location: Vulcania
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| Posted: Mon Aug 20, 2018 9:48 am Post subject: Re: DOHC vs. OHV |
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| TDCTDI wrote: |
| Helfen wrote: |
| oprn wrote: |
| Helfen wrote: |
OHV and SOHC cams use two valves per cylinder.
DOHC use two cams and use four valves per cylinder, also DOHC engines control their cam timing events depending on the RPM and load on the engine. This is what we call variable valve timing. By controlling intake cams and exhaust cams by retarding and advancing SEPARATLY we can get more torque out of the engine at lower rpm and by changing the events can get more HP at higher RPM. We also can tune the adjustable cams for better mileage. And four valves get more in and more out by volume and faster.
In the 60's some of the cam companies like Isky made mechanical advanced cams for V-8 engines, primarily for the SBC. This gave some low end torque and at high rpm it would advance the cam, problem was it advanced and retarded both the intake and exhaust events at the same time. DOHC is better because #1. 4 valves instead of two, and 2. you can control intake and exhaust valves separately for optimum HP and Torque. |
There are lots of DOHC engines that don't' have all that technology and there are SOHC engines that do. |
Lots? name them. |
Does '80s/'90s DOHC technology count? Because everything from VW, Mitsubishi, Toyota, & most of Honda fall into this category. |
I suppose it does, however the thread kind of moved into the here and now. |
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oprn
Samba Member
Joined: November 13, 2016
Posts: 12740
Location: Western Canada
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| Posted: Mon Aug 20, 2018 8:10 pm Post subject: Re: DOHC vs. OHV |
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| Porsche has been producing DOHC engines for what - 40 years without all the trappings you are talking about. |
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Helfen
Samba Member
Joined: January 19, 2009
Posts: 3450
Location: Vulcania
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| Posted: Mon Aug 20, 2018 8:21 pm Post subject: Re: DOHC vs. OHV |
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| oprn wrote: |
| Porsche has been producing DOHC engines for what - 40 years without all the trappings you are talking about. |
No trappings from me. Be specific. Who? |
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