That might be the case with the current generation of the CRV, but previous generations were built on the Civic’s platform.
The 2.4 has been in use in the CRV since 2002.
One problem with SOHC engine heads is that the cam usually happens to be right where you would ideally have the spark plugs located, so you either have to have the spark plug in a less than ideal location or you have to have that spark plug at some weird angle to miss the camshaft. DOHC also does away with the complexity of rocker arms.
Unless it’s a BMW with hydraulic lifters and similar designs.
OK, there are exceptions. There is also the Geo Metro engine which is a SOHC engine that does not use rocker arms by using a two valve wedge shaped combustion chamber.
I wouldn’t go that far. Certainly high fuel taxation and ridiculous insurance rates on anything displacing more than 2 liters has something to do with it. If fuel costs and insurance rates were more comparable to the U.S., I think you’d see more powerful cars in Europe, larger (by EU standards) cars would be more popular, you’d see more Mondeos than you would Foci for example. They wouldn’t be buying F-250’s or anything, but the typical car would likely be larger than it is now.
You can argue that the higher fuel and insurance costs are the necessities, but my view on it is that the populace allows such policies to continue, and are presumably okay with it. So that would make it a choice rather than necessity. .
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Unless I’m mistaken, I think they introduced the second generation CRV in 2002. The first generation was built on the same platform as the Civic.
Honda’s V-tec relies on using two different intake cam lobe profiles for each cylinder, so even the DOHC uses rocker arms. The rockers are liked together so that both valves operate from one of the cam lobes depending on the engine needs at that time.
Because there are two different lobes, the profiles can be set for different cam timing as well as lift and duration. With SOHC, the angle between the intake and exhaust lobes is also limited to two steps. With DOHC, the cam angle between the intake an exhaust valves can be continuously varied to optimize for conditions regardless of which cam lobe is currently in use.
Also, the Civic Si uses the 2.4L engine so why couldn’t the Civic based CRV also use the 2.4L engine?
Sometimes I wonder how such a complex system with so many moving parts can be reliable. My Civic doesn’t have a VTEC engine, but it’s had issues with its variable spark timing, and sometimes I wish I could find a simple reliable car with a simple reliable internal combustion engine rather something with new or complicated technology (although I know VTEC has been around for at least 18-20 years).
I asked someone with Mech Eng b/g - this is what he says about SOHC:
SOHC that’s mean one intake valve and one exhaust valve. The speed for cylinders feeding with air+gasoline isn’t too high and output result for delivered power is limited. Almost the same is the status for exhaust valves. On the engines designed DOHC are equipped with x2 exhaust valves and x2 intake valves for each cylinder. This decision added more output power to the engine because the cylinders (engine) are supplied with air+gasoline more fast and with additional amount of this mixture. During the exhaust cycle, evacuations of the burned fuel is most successful and faster. All these increase drastically the output engine’s power!
I don’t understand why HRV simply didn’t use the more powerful engine from a Civic!
Wrong. SOHC does not mean one intake and one exhaust valve, and DOHC does not mean 2 intake and 2 exhaust valves. The advantage of one overhead cam is less moving parts and a simplified timing belt or chain system. The advantage of dual overhead cams is the ability to independently alter intake and exhaust valve timing.
Someone will correct me if I’m wrong, but I imagine the speed of the intake mixture in through a single intake valve would be faster than in a dual intake valve system, given identical engine displacement.
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What @asemaster said - your engineer friend is clueless when it comes to engine design. There have been 2-valve DOHC engines for decades, and Honda makes lots of 4-valve SOHC engines.
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My 1994 Tercel is SOHC . . . with 3 valves per cylinder
so much for that theory
SOHC that’s mean one intake valve and one exhaust valve. The speed for cylinders feeding with air+gasoline isn’t too high and output result for delivered power is limited. Almost the same is the status for exhaust valves. On the engines designed DOHC are equipped with x2 exhaust valves and x2 intake valves for each cylinder. This decision added more output power to the engine because the cylinders (engine) are supplied with air+gasoline more fast and with additional amount of this mixture. During the exhaust cycle, evacuations of the burned fuel is most successful and faster. All these increase drastically the output engine’s power!
Even I know that the above is Malarkey !
Thanks @texases
I’m glad that we got to the bottom of it.
Nissan employees debate and make a decision and move on!
If four valve heads “drastically” increased the power output, we would have seen them used a lot earlier.
Supercharging drastically increases engine power output, four valves just increases it a little. You have to take into consideration that by using only two valves, you have room for bigger valves.
That’s true. And higher intake velocity can be an advantage in that it helps the fuel mix with the air better plus more turbulence and swirl when the spark fires speeds up the combustion process.
My '88 fuel injected Accord had 2 intake valves per cylinder with separate manifold runners for each intake valve.
There was a butterfly valve in the intake manifold to close off half the intake valves below 4500 rpm to increase intake velocity.
There has been a lot of discussion/viewpoints w.r.t SOHC Vs DOHC - would any of u offer to write a summary (a tutorial) of the findings in a points form? There are so many terminology used.
Already done:
@texases - Thanks
I was reading wikipedia and it said “DOHC with a multivalve design also allows for the optimum placement of the spark plug which, in turn, improves combustion efficiency”
If the combustion efficiency is improved on DOHC, can I deduce to think that it also does (assuming everything else is identical other than SOHC vs DOHC - if not under what other assumption it become true):
- improve power
- reduce emission?
Naturally, I have another question - what is the cost-benefit of SOHC vs DOHC, especially if DOHC is not delivering anything that SOHC can not deliver?