Single vs. Dual cam engine design

wildbill · Jan 21, 2005

SOHC uses rocker arms and does not safely rev as high as a DOHC.The DOHC like Yamaha holds the valve adjustment better.The downside is they can be mean to adjust as in having to remove the cams or needing a special tool to do so.For a small engine the easiest way to get more power is to rev it.For the larger bikes a SOHC is fine but where high rpm is concerned I think a DOHC is better.

LINEAWEAVER · Jan 21, 2005

Hello Friends,
In addition to the many pros and cons of each engine configuration may I also point out that using more than one camshaft often allows for a straighter inlet and / or exhaust tract. Such has the potential to improve cylinder filling in particularly during high rpm. Unfortunately current (offroad) chassis design does not lend itself well to a downdraught inlet port. (ie vertical inlet).

Example:
Both DOHC and SOHC versions of the ever popular Rotax 600cc single are available. Said engines differ only from the crankcase spigot up. The DOHC model has yet to prove of advantage as in order to market said engine for a conventional chassis design the inlet is still required to be that of a side draft design (ie horizontal inlet).

Note:
The twin cam top end is liquid cooled where that of the single is by air. 8O

Just my two cents regarding this interesting thread.

Kind Regards,
Dale

Splat · Jan 22, 2005

hribman said:
So they designed a new 250 ccm engine. An tell me what you want, but IÃ‚Â´m convinced that Husaberg supported them with their "know how" and helped them to design this new power-engine.
Some details let me think that.

I met several KTM factory guys at the WORCS race and we discussed the new 250sxrfs. I asked if Husaberg helped in the design, they replied that they borrowed the Cosworth Indy car engine design. That is why the original prototype has the gear drive cams. They would really like to keep the gear drive valve train, but they know the reality is that too many consumers won't understand or appreciate the benefit and will instead focus on the noises; which in the opinion of most squids will be excessive and unacceptable. KTM doesn't want the battle of trying to educate the consumer that the noises from a gear drive valve train are normal. The complaint would be "Something is wrong with my engine, that noise can't be normal. Why doesn't the Honda make all that noise? " Blah, blah, blah.

Splat · Jan 22, 2005

Taffy said:
3 inlets doesn't flow much if any better than 2. the surface area which the air is slowed by, the 3rd guide, the third valve in the way all add up.

Several independant studies of the 3 valve intake do in fact prove that it is more efficient than a 2 valve inlet design. Both in volumetric efficiency and in power production.

LINEAWEAVER · Jan 22, 2005

Building on the previous point made by Splat:
Harley Davidson went to chain driven camshafts on the Twin Cam 88 to reduce engine noise. Unfortunately said chain drive has proven to be a "weak link" (pun intended). S&S gear driven replacement camshafts were made available shortly after the TC release.

Dale

Ps
Eliminating the CB from late model Husaberg engines considerably reduces engine clatter as a pair of spur gears are eliminated.

Splat · Jan 22, 2005

LINEAWEAVER said:
Hello Friends,
In addition to the many pros and cons of each engine configuration may I also point out that using more than one camshaft often allows for a straighter inlet and / or exhaust tract. Such has the potential to improve cylinder filling in particularly during high rpm. Unfortunately current (offroad) chassis design does not lend itself well to a downdraught inlet port. (ie vertical inlet).

Didn't the Cannondale head design overcome that issue?

I recall that was one of the reasons they chose EFI.

LINEAWEAVER · Jan 22, 2005

Splat said:
LINEAWEAVER said:

Hello Friends,
In addition to the many pros and cons of each engine configuration may I also point out that using more than one camshaft often allows for a straighter inlet and / or exhaust tract. Such has the potential to improve cylinder filling in particularly during high rpm. Unfortunately current (offroad) chassis design does not lend itself well to a downdraught inlet port. (ie vertical inlet).

Click to expand...

Didn't the Cannondale head design overcome that issue?

I recall that was one of the reasons they chose EFI.

Hi Splat,
As is most often the case you are indeed correct.

Best Regards,
Dale

wildbill · Jan 22, 2005

Here is a idea, a short stroke 250cc engine with DOHC using a downdraft carb with the backbone of the frame as the airbox.Sound familar?

Splat · Jan 22, 2005

wildbill said:
Here is a idea, a short stroke 250cc engine with DOHC using a downdraft carb with the backbone of the frame as the airbox.Sound familar?

Sorry Bill,

You must have been daydreaming again :wink:

Splat · Jan 22, 2005

LINEAWEAVER said:
Eliminating the CB from late model Husaberg engines considerably reduces engine clatter as a pair of spur gears are eliminated.

Too bad that we can't just trade the CB spur gear noise for a gear driven valve train. It would probably be a pretty close swap on the db levels. Eliminate two Achilles' heels with one swipe of the engineering pen.

Now I'm daydreaming. :lol:

dsducati · Jan 22, 2005

Why is it that the younger fellows don't like the whine of a gear drive cam, yet the older guys marvel over the sounds that, for instance, a bevel drive Ducati makes. I remember always wondering if the valves were closing or not in my Pontiac Gran Prix when I sold my old Super Bee (in 1979) which had a 440 6 pack and solid lifters. Could always hear that reassuring clatter in the Dodge. I continue to show my age one more time.
Dan

steve · Jan 23, 2005

Splat · Jan 23, 2005

dsducati said:
Why is it that the younger fellows don't like the whine of a gear drive cam, yet the older guys marvel over the sounds ....

Because they never took a shop class, didn't have to rebuild their first car (test drives were for the rich kids, we towed ours home and rebuilt it, THEN got to drive it for the first time), probably never even owned any tools before they moved out of their parents house,.....

my old Super Bee (in 1979) which had a 440 6 pack and solid lifters.

For you young guys, that is not a 6 pack of beer.

Could always hear that reassuring clatter in the Dodge. I continue to show my age one more time.
Dan

THOSE really were the days.

Now they buy a computer chip and brag about their hp gains. They don't even get grease under their nails.

wildbill · Jan 23, 2005

All gear drive to the cams doesn`t make that much noise (had a streetbike that was that way and it was quiet) to me anyway.That would fix a bunch of ills. There is a problem ,building a engine like that would not be cheap.I`am either day dreaming or having a fantasy :lol: Time will tell.

littleyellowbat · Jan 23, 2005

Steve,

I believe you are right. To my knowlege VOR and Vertematis use a gear driven cam configuration. Does anyone know of any other production dirtbikes that use gear driven cams?

dsducati,

Who says young guys cant appreciate a symphony of gear whine?? Of course my dads Ducati 750GT probably slightly biased my tastes.

steve · Jan 23, 2005

I believe that the Vertamati brothers started out as the Italian Husaberg importers. They started modifying and racing them and ended up with a largely new bike that bacame the VOR. They sold the company and have started again as Vertamati building a handful of bikes every year.

VORs currently have a gear drive cam, RHS foward rotating kick starts Ohlins suspension and a Berg heritage. I've yet to experience a better suspension and it was a stock, 04 450.

LINEAWEAVER · Jan 23, 2005

steve said:
I believe that the Vertamati brothers started out as the Italian Husaberg importers. They started modifying and racing them and ended up with a largely new bike that bacame the VOR. They sold the company and have started again as Vertamati building a handful of bikes every year.

VORs currently have a gear drive cam, RHS foward rotating kick starts Ohlins suspension and a Berg heritage. I've yet to experience a better suspension and it was a stock, 04 450.

You sir are absolutely correct.

schwim · Jan 23, 2005

whee! engine noises

There is no more beautiful sound than a 2 liter VW aircooled engine with dual DLRA's, straight cut cam gears and a serpentine belt drive....

Well adding a turbo makes a better sound, but I never got to keep any that I built

thanks,
json

Splat · Jan 24, 2005

wildbill said:
There is a problem, building a engine like that would not be cheap...

Cost of production is not the concern. There isn't much difference. They pursued the gear drive design for the mechanical benefits and they knew the costs involved.

All gear drive to the cams doesn`t make that much noise (had a streetbike that was that way and it was quiet) to me anyway.

Unfortunately, we can't get the dirt bike editors to let you write the review.

You can only guess how much they would complain in their reviews.

Now, if Honda used a gear drive first, they would sing a different tune.

justin_yz426 · Jan 24, 2005

Splat said:
dsducati said:

Why is it that the younger fellows don't like the whine of a gear drive cam, yet the older guys marvel over the sounds ....

Click to expand...

Because they never took a shop class, didn't have to rebuild their first car (test drives were for the rich kids, we towed ours home and rebuilt it, THEN got to drive it for the first time), probably never even owned any tools before they moved out of their parents house,.....

my old Super Bee (in 1979) which had a 440 6 pack and solid lifters.

Click to expand...

For you young guys, that is not a 6 pack of beer.

[quote:1ljcanwu]
Could always hear that reassuring clatter in the Dodge. I continue to show my age one more time.
Dan

THOSE really were the days.

Now they buy a computer chip and brag about their hp gains. They don't even get grease under their nails.[/quote:1ljcanwu]

HEY!!!! I'm 18 damn it!. I aint nothing like that! I'm rebuilding a 62 c-10 fleetside with a virgin block 283.

Single vs. Dual cam engine design

Help Support Husaberg:

wildbill

LINEAWEAVER

Splat

Splat

LINEAWEAVER

Splat

LINEAWEAVER

wildbill

Splat

Splat

dsducati

steve

Splat

wildbill

littleyellowbat

steve

LINEAWEAVER

schwim

Site Founder

Splat

justin_yz426

Similar threads

Register CTA

Recent Discussions

Recent Discussions