EN40B cam with unknown cam follower material

[tatertots89]

Hey, I am designing a 4-lobed fuel pump cam and was wondering if I could get some insight into choosing a material. I am planning on using EN40B Nitrided Steel but am not positive on the cam follower material it will mate with, presumably it's stainless steel (PN 06L109311). Is this something I need to look into further? Or, since EN40B Nitrided Steel has a similar surface hardness to most OEM automotive spec (chilled cast iron), should I be fine choosing it?

I am not sure of the importance (scuff characteristics) of mating a specific cam material for a given cam follower material, or if I should be going with a "harder the cam material the better for a given cam follower material" approach.

Thanks for your help.

 

[TugboatEng]

Is the contact going to be rolling or sliding?

 

[RodRico]

I believe Maraging 350 is the hardest, toughest, and strongest steel, but it sells for a premium over other steels. As usual it boils down to requirements. See

http://fountainheadalloys.com/maraging-c-350/

 

[gruntguru]

How is the contact surface lubricated?

je suis charlie

 

[dgallup]

The only flat lifter I ever worked on was in a heavy duty diesel about 40 years ago. It had a carbide wafer brazed on for the contact surface. Probably overkill.

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[tatertots89]

Thanks for the replies everyone!

- The contact is going to be rolling and not sliding (roller tappet not flat tappet).
- Thanks RodRico for the material suggestion but I think that may be a bit overkill, I am just looking to meet or exceed OEM automotive camshaft material specs which as I understand are usually chilled chrome cast iron.
- The contact surface is lubricated with automotive engine oil (synthetic 5W40).
- Thankfully this is for a roller tappet and not a flat tappet but interesting to hear about the brazed carbide wafer of the flat lifter.

 

[RodRico]

I am just looking to meet or exceed OEM automotive camshaft material specs

Material selection derives from load and wear analysis at temperature in the given lubrication environment. If your design is identical to a successful OEM design, then you can probably get away with using what they used. Of course, if they don't *say* what they used, you're left guessing. That's why some Chinese knock-offs fail... they copy the design but don't use the right materials (or intentionally use cheaper materials thinking "it will work most of the time").

 

[BigClive]

What sort of "fuel pump cam" is this? Why does it need to be so tough? If you are using a roller tappet I don't think you will have much choice of material.

 

[enginesrus]

There are tools that can ID materials. Just look see what others are using.

 

[tatertots89]

-Rodrico: Yes I understand that. What I am assuming is that a Nitrided EN40B steel cam is going to be suitable since this is for a roller cam (not a flat-tappet) and the OEM (mass produced) cam is cast iron. I'm making low quantities also.
-BigClive: Fuel pump cam is for a high-pressure fuel pump in a turbocharged 2.0 4-cyl gasoline engine. Previous engine generations were plagued with cam failures due to design (3-lobed versus 4-lobed cam changing the pressure angle). What do you mean by "If you are using a roller tappet I don't think you will have much choice of material"? Are you referring to most roller cams being steel over cast iron flat-tappet cams?
-Enginesrus: Yes I am aware, thank you.

Thanks again for your help!

 

[BigClive]

How does this fuel system work? - it doesn't seem to be a common rail type? Like an old diesel injector with a separate cam and piston for each cylinder?

A wise old cam grinder once told that there really was nothing better than nitrided 4140 for the cam and follower. But people do use stellite facings on really extreme cams - and on the followers. I presume your cam is physically fairly small? - maybe make it entirely entirely of stellite?

As for the roller followers - you can't really make your own rollers (although Stan Sainty did for his top fuel engine). So the rollers will have to be bought off the shelf - choose the best and most suitable.

The same wise old cam grinder also told me that if you can't get your cam to last with 4140/stellite etc. there is something seriously wrong with the design.

 

[dgallup]

The common rail gasoline direct injection systems use a piston pump driven by a cam lobe. There is a high failure rate in all of them.

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