knife edged crank shaft

[bajansuperman]

Hi , i've seen a couple of these in most of the builds on here. I would like to know what happens when this is done

[H_D]

The lobes on the crank are grounded to look like the edge of a knife,

Knife edging causes less friction when the lobes hit the oil when they rotate.

It also makes the crank lighter which helps rev up faster but can also cause the revs to drop too fast when changing gears.

[bajansuperman]

The lobes on the crank are grounded to look like the edge of a knife,

Knife edging causes less friction when the lobes hit the oil when they rotate.

It also makes the crank lighter which helps rev up faster but can also cause the revs to drop too fast when changing gears.

thanks for the information

[Azz]

Mines been done for my engine, knife edged, pollished and balanced mainly to aid in reving to help spool the gtx30

[bajansuperman]

Mines been done for my engine, knife edged, pollished and balanced mainly to aid in reving to help spool the gtx30

Nice are you getting the problem h_d was talking about?

Edited November 20, 2013 by bajansuperman

[AdamB]

Not worth it in my opinion, it removes too much material and makes the crank considerably weaker. If you do get it done I would say to have the crank go through some heat treatment to bring its tensile strength back up.

[morgey]

I dont really get it, you say when the crank hits the oil. There's a girdle between the oil in the sump and the crank so it never gets in direct contact with much. Other than what's falling down the oil returns .

I'm sure I'd does have a purpose but I struggle to see unless running mad revs on a highly strung engine, isn't zisco using a stock one still?

[H_D]

Not worth it in my opinion, it removes too much material and makes the crank considerably weaker. If you do get it done I would say to have the crank go through some heat treatment to bring its tensile strength back up.

x 2

[Azz]

Nice are you getting the problem h_d was talking about?

I have accounted for the revs to drop in my build so I changed ecu from the dta s40 to the dta s60 so I can run antilag when using full boost.

Fingers crossed everything works out well.

[AdamB]

Personally if it was me I would use a vacuum pump or a dry sump kit to create a vacuum in the crankcase to help reduce engine parasitic losses, it only takes a small amount of crank whip or knock and it will have you replacing the crank.

[Phil]

Personally if it was me I would use a vacuum pump or a dry sump kit to create a vacuum in the crankcase to help reduce engine parasitic losses, it only takes a small amount of crank whip or knock and it will have you replacing the crank.

yup, dont lighten.

your pick up is less with the knife edge.

and whip is impossible with a stock crank as its not the full assembly(clutch flywheel) balance that stops whip its the single element, ie the crank needs balanced bang on (like stock)

if you know what you want and can explain it to you engineer and there is some benefit that you need it done for, then fire away.

but i would be MASSIVELY surprised if even the 9sec malta drag 4e runs anything lightened in the flywheel/crank department.

Phil

[Azz]

Personally if it was me I would use a vacuum pump or a dry sump kit to create a vacuum in the crankcase to help reduce engine parasitic losses, it only takes a small amount of crank whip or knock and it will have you replacing the crank.

This would be for more of a track prepped car i should.

General driving with a oem sump would be more than efficient ( I hope haha )

[Phil]

General driving with a oem sump would be more than efficient ( I hope haha )

100% grand, if you were worried you could maybe go baffled if your going to find long corners you enjoy taking at full chat lol

Phil

[AdamB]

This would be for more of a track prepped car i should.

General driving with a oem sump would be more than efficient ( I hope haha )

It would be the route I would choose rather than lightening the crank. If I was to lighten the crank it I would just use a billet crank tbh.

That's if the reasoning for knife edging was to reduce windage, if its for weight then I think its just silly and not needed, could potentially be more of a ballache than it's worth unless its a race car that your prepared to magnaflux the crank every so often.

Phil do you know if Spuddy ran a knife edged crank? I'm sure it was stock but thought you would know better.

[Phil]

It would be the route I would choose rather than lightening the crank. If I was to lighten the crank it I would just use a billet crank tbh.

That's if the reasoning for knife edging was to reduce windage, if its for weight then I think its just silly and not needed, could potentially be more of a ballache than it's worth unless its a race car that your prepared to magnaflux the crank every so often.

Phil do you know if Spuddy ran a knife edged crank? I'm sure it was stock but thought you would know better.

not sure but i doubt it.

will ask him when i next chat to him.

Phil

[Azz]

Here's a quick picture of mine just for reference