Short Pushrods and Tall RPMs in Real World Performance

[Tom68]

I'm again assuming SOHC is a typo, and you meant DOHC, since I don't see how finger followers can be utilized with a single overhead cam design. As far as I know, only double overhead cams can act directly on valve springs without the use of rocker arms.

However, if I am wrong, please correct me, as I would very much like to know how finger follower design could successfully replace the typical rocker arm design typically associated with SOHC engines.

SOHC finger follower designs are quite common, but more in the motorcycle world.
See for example a KTM 450 SXF cylinder head. Or several Honda designs (marketing name "UNICAM") for 450ccm engines.
There are a lot of engines like this, but these are recent examples.
Some theory could be found in Mahle publications and books from Ludwig Apfelbeck.

Too expensive for automotive engines, so only common in motorcycle engine design.

Automotive uses the more expensive dohc with or without rockers, they do it for vvt.

[juuhanaa]

Automotive uses the more expensive dohc with or without rockers, they do it for vvt.

Aand valve speed

IMG_20210518_174655.jpg

-juhana

[nicholastanguma]

I'm again assuming SOHC is a typo, and you meant DOHC, since I don't see how finger followers can be utilized with a single overhead cam design. As far as I know, only double overhead cams can act directly on valve springs without the use of rocker arms.

However, if I am wrong, please correct me, as I would very much like to know how finger follower design could successfully replace the typical rocker arm design typically associated with SOHC engines.

SOHC finger follower designs are quite common, but more in the motorcycle world.
See for example a KTM 450 SXF cylinder head. Or several Honda designs (marketing name "UNICAM") for 450ccm engines.
There are a lot of engines like this, but these are recent examples.
Some theory could be found in Mahle publications and books from Ludwig Apfelbeck.

Too expensive for automotive engines, so only common in motorcycle engine design.

Thank you for the correction and examples.

[Tom68]

Automotive uses the more expensive dohc with or without rockers, they do it for vvt.

Aand valve speed

IMG_20210518_174655.jpg



-juhana

Lobes look bigger than their clearance area.

[nicholastanguma]

SOHC finger follower designs are quite common, but more in the motorcycle world.
See for example a KTM 450 SXF cylinder head. Or several Honda designs (marketing name "UNICAM") for 450ccm engines.

Okay, I just looked at some diagrams of these SOHC mills, and indeed they do use finger followers as you state. Now I understand how finger followers can be used to replace rocker arms in single overhead cam architecture, a picture is worth a thousand words. Danke, ich weiß deine Hilfe zu schätzen!

[juuhanaa]

Automotive uses the more expensive dohc with or without rockers, they do it for vvt.

Aand valve speed

IMG_20210518_174655.jpg



-juhana

Lobes look bigger than their clearance area.

You make it sound radical But yes, the lobes makes a positive affect. That was a Renault F4R valvetrain, hydraulic finger rocker arm thing. Catcams 5502423 with a lift to valve diameter ratio of .336. 8000rpm in a endurance hi performance is like pushing luck. I would like to push the l/d ratio to max using this kind of valve train. A basic engine like this has a mean piston speed of 5500ft/min @ 9000rpm.



-juhana

[Tom68]

Okay, I just looked at some diagrams of these SOHC mills, and indeed they do use finger followers as you state. Now I understand how finger followers can be used to replace rocker arms in single overhead cam architecture, a picture is worth a thousand words. Danke, ich weiß deine Hilfe zu schätzen!

and on DOHC. Patent applied for by Louis Chevrolet in 1917.

Louis.jpg

[Tom68]

and this desmodromic sohc one.

https://www.chevroletbrothers.com/_file ... bb5ccc.pdf

L C.jpg

[SchmidtMotorWorks]

The potential depends on the base circle of the cam and the lobe designs that can work with the follower geometry.