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> Type-IV Crank mods, What needs to be done?
URY914
post Nov 4 2004, 12:11 PM
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What needs or can be done to a 2.0 crank to improve on it?

Knife edge?
Polish it?
High tech coatings?
Soak it in Jack?

(and don't give me any shit like "drill it full of holes to lighten it' (IMG:style_emoticons/default/wacko.gif) )

Paul
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brant
post Nov 4 2004, 12:32 PM
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Definitely boat tailing/knife edging..

I've been down this road before and for a true race car its a necessary.

brant
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Aaron Cox
post Nov 4 2004, 12:48 PM
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what is knife edging?
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brant
post Nov 4 2004, 12:58 PM
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QUOTE(acox914 @ Nov 4 2004, 11:48 AM)
what is knife edging?

I was using it as another slang work I've heard used for boat tailing the crank.

brant
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MattR
post Nov 4 2004, 12:59 PM
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You basically sharpen one end of the connecting rod so it has less resistance through the oil (think of an airfoil).

We used to do it all the time when we modified RC Car engines.
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URY914
post Nov 4 2004, 01:01 PM
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Its when you tapper the yokes of the crank so it cuts through the oil in the sump easier.

I think that part of the crank is called the yoke (IMG:style_emoticons/default/confused24.gif)

Paul
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MattR
post Nov 4 2004, 01:15 PM
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Oh, you taper the crank? My mistake! I thought it was con - rod work. I guess 2 stroke is a bit different then 4 stroke...
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SLITS
post Nov 4 2004, 01:17 PM
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"Knife edging" involves a Dremel / Do - Mor grinder wherein you make the edge of the counterweights a "knife edge". This is supposed to help with parasitic drag caused by oil flying around inside the crankcase because it sticks to the crankshaft - you would also polish the counterweights to provide a smoother surface.

It also has the benefit of reducing crankshaft weight resulting in lower rotating mass and faster spinups. It could also expose flaws in the casting too.

Of course, the type 4 crank is not counterweighted.

All this applies when you are looking for fractional horsepower or you have a shit pile of time on your hands. You won't gain a pile of HP.
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J P Stein
post Nov 4 2004, 01:21 PM
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I dunno what it is in the world of T-4, but in the rest of the world it involves chamfering...big chamfers to bring them to nearly a point.... both sides of the crank's counterweights.


(edit) Keerist, now I'm slower than Slits...gettin' old sux.
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URY914
post Nov 4 2004, 01:22 PM
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QUOTE(SLITS @ Nov 4 2004, 11:17 AM)
All this applies when you are looking for fractional horsepower or you have a shit pile of time on your hands. You won't gain a pile of HP.

I see it as a lot of work with little gain also.

I'll clean up and lighten the rods, but the crank I'm leaving as is.

Paul
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machina
post Nov 4 2004, 01:26 PM
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What about balancing? That may be more important than anything else.

You can have your entire rotating assembly balanced for a couple hundred bucks.
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Walter
post Nov 4 2004, 01:27 PM
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QUOTE(URY914 @ Nov 4 2004, 10:11 AM)
What needs or can be done to a 2.0 crank to improve on it?

Knife edge?
Polish it?
High tech coatings?
Soak it in Jack?

(and don't give me any shit like "drill it full of holes to lighten it' (IMG:style_emoticons/default/wacko.gif) )

Paul

IMHO, just the best balance job you can get. (together with the rods, flywheel etc...)

Stock (new) type 4 cranks are - as mentioned before - not counterweigthed and IIRC are nitrated from the factory. First undersize wouldn't usually need a re-nitrading either.
Better put your money in other engine parts, since the crank is nearly bulletproof...

Regards,
Walter
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MattR
post Nov 4 2004, 01:28 PM
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85 bucks from rimco for pressure plate to fan balancing.
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Rough_Rider
post Nov 4 2004, 01:33 PM
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Knife edging & boat tailing are similar but different.

Knife edging, as folks have already stated, is done on the crank. Streamlines the crank to cut through the oil. Less necessary on dry sump systems.

Boat tailing is done on the castings inside the crank case. Idea being it promotes smoother oil & air flow.

Don't honestly know whether any of these things make a difference. I'd guess its tiny % points either way. If everything else has been optimised, weight, suspension, tyres, brakes, nut behind the wheel, etc. Then why not give it a go.
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SLITS
post Nov 4 2004, 01:35 PM
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I think if I were into this again - I would do the following:

1.) Lighten the piston as much as possible
2.) Cut the seats of the cylinders and pop the piston out so that I had about 0.030 from the top of the cyl to the first ring land.
3.) Cut the deck of the piston to compensate.
4.) Gun drill the piston pins to reduce weight
5.) Lighten the big and little end of the rod as much as I could
6.) Lighten and polish the rod beams
7.) Massage the crankshaft as mentioned
8.) Buy hi-strength fasteners for the rod caps
9.) Reduce the flywheel weight as much as possible
10.) reduce the impeller fan weight as much as possible.
11.) Port match the heads
12.) Use Manley Pro-Flo ss valves
13.) Ahhh Hell with it
14.) Build a stock motor to spec and motor happily down the road (IMG:style_emoticons/default/biggrin.gif)
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URY914
post Nov 4 2004, 01:40 PM
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I'm making some carbon fiber rods.
Should be pretty light.
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Britain Smith
post Nov 4 2004, 01:46 PM
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Here is a pic of mine 78mm crank...knife edged, counterweighted, with carrillo rods.

-Britain

(IMG:http://www.britainsmith.com/Porsche/912Project/TurboMotor/BottomEnd/images/124_2466_JPG.jpg)
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Britain Smith
post Nov 4 2004, 01:48 PM
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another...

(IMG:http://www.britainsmith.com/Porsche/912Project/TurboMotor/BottomEnd/images/128_2824_JPG.jpg)
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SLITS
post Nov 4 2004, 01:51 PM
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"BIG BUCKS"
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URY914
post Nov 4 2004, 02:00 PM
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SICK
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