Why is Honda is anti DOHC?

[3Razors]

I just dont understand what Honda has against dual overhead cam engines!? There unicam design on the 450r really needs to be scrapped to compete with the yfz450.

[wanta250r]

All there cars are DOHC aren't they? They probably think its uneccesary in smaller engines?

[Tri-ZNate]

the 350x is DOHC, but I get what you are saying about newer machines. The 450r isnt DOHC:wondering? That is weird.

[Jason Hall]

I'm glad the 450-R does'nt have dual cams. When it comes time to buy 1 cam you spend half the money. I don't see where the 450-R or the crf 450 is lacking one bit because of only having one cam. It's pretty smart on hondas part to build a motor with a single over head cam, that can STOMP motors with dual cams. The 450's have a roller tipped rocker on the exhaust side. The 450-R has lightning quick throttle response, there is no need for the second cam. Thanks honda, now when I get my 450-R I will be able to afford to put A camshaft in it, unlike If I owned a YFZ (NOT).

[3Razors]

The 350X is a single cam engine. With the yamaha yfz450''s you dont need to buy aftermarket cams because yamaha gives the customer high performance ones right from the factory installed on the bike. Just retard the exhaust cam one tooth (a free mod) and you have the same cam and specs as the wr450f! With Honda you have to buy the power up kit which comes with a cam and other components. Dual cams are superior to a single design for the reason that you get a motor that revs much quicker. Also add that the yamaha motor is a 5 valve motor and not 4 valves like the honda.

[Lomax]

Its to hard for honda to put to cams in there "sideways" ass motors that they put on most everything. I think that the 450r should be a DOHC though. SOHC is simpler for the average person to fool with. Try adjusting the Valves on a DOHC like, say, a Kawasaki Mojave, pain in the ass!!!

[3Razors]

I agree. For the recreation and utility machines a single cam would be better and more user friendly not having to use shims to adjust the valves. But the flagship 450r should have a dual design.

[slothminx]

Explain why having two is an advantage? you can have a single cam doing exactly the same job and as said when it comes to upgrade time its cheaper

[3Razors]

With two cams you can run more valves per cylinder as well as having more radical cam timing. You would never have to upgrade the stock cams in the yfz, they are the same cams that you get in the dirt bike. Yamaha put a ton of design and engineering in them. You just have have to retard the exhaust cam one tooth (yamaha bike specs) and you are set to scream!

[OldSchoolin86]

With two cams you can run more valves per cylinder as well as having more radical cam timing. You would never have to upgrade the stock cams in the yfz, they are the same cams that you get in the dirt bike. Yamaha put a ton of design and engineering in them. You just have have to retard the exhaust cam one tooth (yamaha bike specs) and you are set to scream!
There's sizable advantages to changing the cams in a yfz. A single cam can run 4 vavles per cylinder with ease. Are you saying they're missing the boat not running 5 valves?

[slothminx]

With two cams you can run more valves per cylinder as well as having more radical cam timing. You would never have to upgrade the stock cams in the yfz, they are the same cams that you get in the dirt bike. Yamaha put a ton of design and engineering in them. You just have have to retard the exhaust cam one tooth (yamaha bike specs) and you are set to scream!

RUBBISH! we have a lancia engine here that is a V4 and it has ONE camshaft per bank. Its a hemi head aswell Theres no loss. You could run 5 valves off one cam easily More radical cam timing? thats purely to do with how it has been ground and how its been setup. On my old 70 we check the stock 3 bolt no adjustment cam timing. It was 4 degrees out as they are nver all the same. Instead of looking at twin cam engines they should be looking at having fully adjustable cam timing, so you can set it for your specific engine.

[3Razors]

The Honda 450r is a great bike. Honda always has and will build top notch vehicles. But from a "pure performance aspect"' you want to get as much fuel/air through the motor as possible to make hp. Every roadracing factory team kawasaki, suzuki, yamaha, and yes honda uses dual cams in there motorcycles. Same with performance cars like ferrari, lamorguini?sp, etc uses the dual setup. When you get a very aggresive single cam setup in a 4 valve arrangement the idle and operation of the machine becomes erratic at low rpm. I do think a reason behind the unicam design was partially for weight savings in there 450 dirtbike lineup. Dirtbikers are CRAZY about weight savings!

[slothminx]

Its only done to have less complicated valve gear, less moving parts at high RPM the better. There would be no wieght advantage as the valve gear probably weighs as much as another cam

[OldSchoolin86]

The Honda 450r is a great bike. Honda always has and will build top notch vehicles. But from a "pure performance aspect"' you want to get as much fuel/air through the motor as possible to make hp. You get the same air flow with a single cam pushing 4 valves as a twin cam.

[thedeatons]

I am not sure of the exact specific differences, but I do know that the guys hopping up Honda Civics use primarily DOHC motors because they can produce more hp from them than the SOHC motors.... There are a few hard nosed underdogs getting high power out of the SOHC motors, but there is always a DOHC that is making more.... Once again, not quite sure exactly why, maybe I will research it....

[Six Stroke]

A DOHC design allows for ideal spark plug placement, and it also lets you use a more efficient chamber design.

But then again, that only matters if you're pushing the ragged edge of performance with your motor. :cool:

[OldSchoolin86]

I am not sure of the exact specific differences, but I do know that the guys hopping up Honda Civics use primarily DOHC motors because they can produce more hp from them than the SOHC motors.... There are a few hard nosed underdogs getting high power out of the SOHC motors, but there is always a DOHC that is making more.... Once again, not quite sure exactly why, maybe I will research it....
The reason is there is less power loss in a twin cam due to the lack of rockers, Honda just probably doesn't think a little single cylinder will gain enough from it to do it.

[slothminx]

I am not sure of the exact specific differences, but I do know that the guys hopping up Honda Civics use primarily DOHC motors because they can produce more hp from them than the SOHC motors.... There are a few hard nosed underdogs getting high power out of the SOHC motors, but there is always a DOHC that is making more.... Once again, not quite sure exactly why, maybe I will research it....


Thats because the SOCH in that case only have 2 valves per cylinder, the soch were talking about has 4.

Six, if the valve gear is right you can have the plug where you want anyway ;) with a full hemi crossflow head

Im not downing the twin cams at all! they are the way to go. just that it wont lose hardly anything

[3Razors]

I pulled this exerpt from a jaguar page. And although it is not the final verdict it does have truthful info.

DOHC VS SOHC (2)


Although the low reciprocating mass of DOHC valve trains is often touted as their greatest advantage, that is not quite so. A well designed SOHC valvetrain using rocker arms usually has less mess moving up and down than a DOHC system does.

The biggest advantage of the DOHC engine is the STIFNESS of the valvetrain. With the cam lobe directly depressing a bucket tappet, whihc, in turn, directly depress the valve stem, there is nothing in the system to deflect. No rocker arms to deflect, no pushrods to buckle slightly, no nothing.

This stiffness allows a DOHC engine to use a more agressive cma profile to pop the valves open more quickly and keep them near their fully open position longer. This in turn promotes breathing.

It also makes for a more tractable engine. In a high performance, single cam, pushrod engine, for example, a cam grind with a very long duration is usually needed in order to get the valves open long enough and far enough to breather properly at high revs. Ironically, at low revs, such a design transfers the cam's long duration to the valves more effectively than it does at high revs, which is why such engines tend to have lumpy idles and very little torque at a low revs.

The DOHC engine, on the other hand, due to its stiff vavle train, does not need such long camshaft durations to achieve useful valve openings at high revs. Consequently, it can idle smoothly and pull strongly throughout the rev range.

DOHC designs have another advantage when coupled with four-valve cylinder heads. It allows the spark plug to be placed smack in the center of the combustion chamber, which promotes efficient combustion and reduces the engine's taste for high octane fuel. With an SOHC engine, the camshaft is usually in the middle of the head, precluding this optimal plug location.

DOHC designs do cost more, but their advantages in power and combustion efficiency make them beneficial even for non-sporting cars. Which is why they have become available on Toyota Corollas and Ford Contours.

[slothminx]

I pulled this exerpt from a jaguar page. And although it is not the final verdict it does have truthful info.

DOHC VS SOHC (2)


Although the low reciprocating mass of DOHC valve trains is often touted as their greatest advantage, that is not quite so. A well designed SOHC valvetrain using rocker arms usually has less mess moving up and down than a DOHC system does.

The biggest advantage of the DOHC engine is the STIFNESS of the valvetrain. With the cam lobe directly depressing a bucket tappet, whihc, in turn, directly depress the valve stem, there is nothing in the system to deflect. No rocker arms to deflect, no pushrods to buckle slightly, no nothing.

This stiffness allows a DOHC engine to use a more agressive cma profile to pop the valves open more quickly and keep them near their fully open position longer. This in turn promotes breathing.

It also makes for a more tractable engine. In a high performance, single cam, pushrod engine, for example, a cam grind with a very long duration is usually needed in order to get the valves open long enough and far enough to breather properly at high revs. Ironically, at low revs, such a design transfers the cam's long duration to the valves more effectively than it does at high revs, which is why such engines tend to have lumpy idles and very little torque at a low revs.

The DOHC engine, on the other hand, due to its stiff vavle train, does not need such long camshaft durations to achieve useful valve openings at high revs. Consequently, it can idle smoothly and pull strongly throughout the rev range.

DOHC designs have another advantage when coupled with four-valve cylinder heads. It allows the spark plug to be placed smack in the center of the combustion chamber, which promotes efficient combustion and reduces the engine's taste for high octane fuel. With an SOHC engine, the camshaft is usually in the middle of the head, precluding this optimal plug location.

DOHC designs do cost more, but their advantages in power and combustion efficiency make them beneficial even for non-sporting cars. Which is why they have become available on Toyota Corollas and Ford Contours.


There comparing that overhead cam jag engine to a pushrod motor. No comparison

[Six Stroke]

Thats because the SOCH in that case only have 2 valves per cylinder, the soch were talking about has 4.

Six, if the valve gear is right you can have the plug where you want anyway ;) with a full hemi crossflow head

Im not downing the twin cams at all! they are the way to go. just that it wont lose hardly anything

SOCH? Single over cam head? GM 2.5 liter? :lol:

True, you can get ideal spark plug placement by moving the valvetrain around on a pushrod motor, but not on a SOHC engine. Why? Because the cam will still be in the way. Also, by moving the valvetrain around on a pushrod engine, you are very likely to compromise the intake and exhaust ports.

I say two stroke all the way!:w00t:

[slothminx]

There comparing that overhead cam jag engine to a pushrod motor. No comparison


sorry i cocked up there lol, didnt read it properly

[slothminx]

SOCH? Single over cam head? GM 2.5 liter? :lol:

True, you can get ideal spark plug placement by moving the valvetrain around on a pushrod motor, but not on a SOHC engine. Why? Because the cam will still be in the way. Also, by moving the valvetrain around on a pushrod engine, you are very likely to compromise the intake and exhaust ports.

I say two stroke all the way!:w00t:


What says the cam has to be in the middle?;)

[3Razors]

Same here. Screw cams all together and run a two stoke!

[OldSchoolin86]

What says the cam has to be in the middle?;)
In a 4 valve where else ar they going to place it?

[Six Stroke]

Where else would you put it on a SOHC engine? Then you'd have some goofy valvetrain.

[slothminx]

In a 4 valve where else ar they going to place it?


direct connect like in a DOHC on the intake valves but with rockers on the exhaust? LOL man im full of ideas:crazy: . My aim here was just to say that 5 valves are possible on a single cam, and theres no huge loss;) ;)

I agree screw cams............ get a pinger:beer

[Six Stroke]

direct connect like in a DOCH on the intake valves but with rockers on the exhaust? LOL man im full of ideas:crazy: . My aim here was just to say that 5 valves are possible on a single cam, and theres no huge loss;) ;)

I agree screw cams............ get a pinger:beer

Oh yeah, I've seen a setup like that on some 32v heads for the Chrysler Hemi. Those are some looong exhaust rockers!

[Blown 331]

I just dont understand what Honda has against dual overhead cam engines!? There unicam design on the 450r really needs to be scrapped to compete with the yfz450.

:crazy: 2006 450R > 2006 YFZ450

[3Razors]

450R for trails and playbike riding

YFZ450 for the track

The 06 450r is much better than the previous years, but the frame geometry is still hindered for serious track competion.

[OldSchoolin86]

450R for trails and playbike riding

YFZ450 for the track

The 06 450r is much better than the previous years, but the frame geometry is still hindered for serious track competion.
Really? The last time I looked a season standings the 450r was right at the top with the yfz. I think we might be confusing preference with performance.

[3Razors]

Yes that is just my opinion. It is my preference along with any other rider to pick the machine that works best for the track. Go to any race and the yfz450 far outnumbers the 450r. True the 450r gets a good showing by a few riders and thats great for the sport. The 450r frame design is similiar to that of the 400ex. The yfz450 has a frame design of the 250r the most dominate quad in atv mx history.

[Blown 331]

Yes that is just my opinion. It is my preference along with any other rider to pick the machine that works best for the track. Go to any race and the yfz450 far outnumbers the 450r. True the 450r gets a good showing by a few riders and thats great for the sport. The 450r frame design is similiar to that of the 400ex. The yfz450 has a frame design of the 250r the most dominate quad in atv mx history.

So you're saying a 250R and 400EX don't have a similar frame? Damn near everything interchanges.

[3Razors]

Yes, thats what im saying. On the 400ex it has a higher seating position than the 250r. The 250r has a "squatty" lower center of gravity style of riding to it more suited for mx. I have ridden both the 450r and yfz and to tell you the truth i have alot more fun on the 450r in the dunes and trails. But on the local track that other riders and i race with the yfz feels and handles better the corners and jumps.

[3Razors]

Its a tough call. No quad is the best at everything, just gotta decide what fits ** style the best. My KX500 trike is purpose built for hill shooting and dune riding but would probably get slaughtered by a blaster (with a good rider) on the mx track! lol Im very interested in seeing suzuki's attempted to dominate the track with its purpose built LTZ450.

[Blown 331]

A 250R and 400EX have very, very similar handling, they're damn near the same. I don't think a YFZ feels anything like a 250R, though I have heard the comparison. If you wanna talk seat height the YFZ and 400EX have the same seat height at 31.9 inches. The 250R is at 30.5.

http://www.yamaha-motor.com/sport/products/modelspecs/323/0/specs.aspx

http://powersports.honda.com/atvs/sport/model.asp?ModelName=TRX400EX&ModelYear=2006&ModelId=TRX400EX6

250R is 3rd post down

http://forums.atvconnection.com/messageview.cfm/catid/8/threadid/449887.cfm