16v KR crank knife edging

[Preen59]

Hey guys,

I've got myself a 1.8 16v that i'm currently working on and i was wondering about knife edging the crank.

I'm a machinist/ Toolmaker and i've got a big enough lathe and other equipment in my workshop to do the job- that's not a problem, but i was wondering if anyone on here has info on how much material to take off aswell as angles and dimensions?

Some pics would be great too, if anyone has any.

Thanks,

Chris Preen.

[velly_16v_cab]

i have a friend back in the uk how does this, i will email him and see what info i can get off him for you.

i used to have a write up on it in a mag but that back in the uk too lol

[Preen59]

Thanks for the quick reply, Velly. I'd appreciate it very much if you could get that info for me.

[VW Convert]

Hey guys,

I've got myself a 1.8 16v that i'm currently working on and i was wondering about knife edging the crank.

Hi Chris,

Pardon my ignorance, what is knife edging?

Cheers

George

[KI11Z]

instead of the bulky crank ends, you essentially "grind" it down to create a "knife edge" so that it can cut through the oil more efficiently creating less drag as well as lightening it and thus releasing valuable hp!

[velly_16v_cab]

Knife edging the crank is mainly for increasing horsepower by reducing the windage loss in the crankcase while reducing the crankshaft's rotational mass, allowing for the engine to accelerate faster

the top on is std, bottom one has been machined

[twin eng, twin turbs]

Hey Chris, knife edging reduces the "parastatic friction loss" as the crank cuts through the oil in the crank case and sump. You need to match the angle of the web between the main bearing to the big end bearing when machining the counterweight, but avoid machining the web between the bearing journals as this will obviously reduce the strength of the crank. Lighten your flywheel aswell and ill dynamic balance it at work for you to 0.1 of a gram and linish it to A tiny amount of low end torque and smoothness will be lost at low rpm due to the weight reduction but its not an issue in comparison to the top end power gain!!!

[rayray086]

Wow good info guys. I didn't know what knife edging was either until now. Just wondering, is there a more technical term to it?

[velly_16v_cab]

no, lol

[gotrice]

Reading through I cant believe that people still think that lightening the rotating mass gives you more power. It reduces the time taken to get to your peak power but you dont get any more horsepower. And yeah I know that I am going to cop a burning now lol.

[velly_16v_cab]

i dont think u get more power, just the engine reponse better

[Preen59]

Reading through I cant believe that people still think that lightening the rotating mass gives you more power. It reduces the time taken to get to your peak power but you dont get any more horsepower. And yeah I know that I am going to cop a burning now lol.

Well, you're right, it doesn't actually allow the engine to produce more power because it doesn't change the thermal efficiency or the size of the charge, but it does effectively lower the drag on the engine, allowing the engine to pull through it's rpm range faster.

How's that for not burning you.

[99gti]

That makes purfect sense realy.

[gotrice]

There is so much love here that I am going to need a hug

[velly_16v_cab]

this was off my mate who does alot of engine building

Anyway. Lightening a crank. Hard one to explain really. He can either take a load of a little, but it has to come off the counterweights. Most tuners will cahmfer the bottom edge of the counterweight. It doesn't remove alot of material, but it will cut better through the oil and mist in the sump. The cranks I've done for myself and my mate, I've machined the whole side of the counter weight into a lon taper. I've aslo machined the flat edges at the end to get the crank equal along it's length as the factory unit is all shapes. All I can say is to take little at a timeand see how it goes. I's easy to ruin a crank in seconds either by machinin the wrong part, or even bending it between centres in the lathe!


he is currently running a 2.1 16v on twin 45's putting out over 200 bhp in a mk1

IT"S QUICK!!!!!!!!!!!!!!!!!!!!