Type-IV Crank mods, What needs to be done? |
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Type-IV Crank mods, What needs to be done? |
URY914 |
Nov 4 2004, 12:11 PM
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#1
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I built the lightest 914 in the history of mankind. Group: Members Posts: 120,446 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
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 |
brant |
Nov 4 2004, 12:32 PM
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#2
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914 Wizard Group: Members Posts: 11,622 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
Definitely boat tailing/knife edging..
I've been down this road before and for a true race car its a necessary. brant |
Aaron Cox |
Nov 4 2004, 12:48 PM
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#3
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
what is knife edging?
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brant |
Nov 4 2004, 12:58 PM
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#4
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914 Wizard Group: Members Posts: 11,622 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains |
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 |
MattR |
Nov 4 2004, 12:59 PM
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#5
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Advanced Member Group: Members Posts: 3,279 Joined: 23-January 04 From: SF Bay Area Member No.: 1,589 Region Association: Northern California |
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. |
URY914 |
Nov 4 2004, 01:01 PM
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#6
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I built the lightest 914 in the history of mankind. Group: Members Posts: 120,446 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
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 |
MattR |
Nov 4 2004, 01:15 PM
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#7
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Advanced Member Group: Members Posts: 3,279 Joined: 23-January 04 From: SF Bay Area Member No.: 1,589 Region Association: Northern California |
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 |
Nov 4 2004, 01:17 PM
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#8
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
"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. |
J P Stein |
Nov 4 2004, 01:21 PM
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#9
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Irrelevant old fart Group: Members Posts: 8,797 Joined: 30-December 02 From: Vancouver, WA Member No.: 45 Region Association: None |
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. |
URY914 |
Nov 4 2004, 01:22 PM
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#10
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I built the lightest 914 in the history of mankind. Group: Members Posts: 120,446 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
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 |
machina |
Nov 4 2004, 01:26 PM
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#11
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Advanced Member Group: Benefactors Posts: 2,030 Joined: 21-June 03 From: Miami Beach, FL Member No.: 848 |
What about balancing? That may be more important than anything else.
You can have your entire rotating assembly balanced for a couple hundred bucks. |
Walter |
Nov 4 2004, 01:27 PM
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#12
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Member Group: Members Posts: 70 Joined: 10-August 04 From: The Netherlands, Europe Member No.: 2,499 |
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 |
MattR |
Nov 4 2004, 01:28 PM
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#13
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Advanced Member Group: Members Posts: 3,279 Joined: 23-January 04 From: SF Bay Area Member No.: 1,589 Region Association: Northern California |
85 bucks from rimco for pressure plate to fan balancing.
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Rough_Rider |
Nov 4 2004, 01:33 PM
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#14
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Smurf Zone Group: Members Posts: 525 Joined: 16-August 04 From: Beaverton, OR Member No.: 2,547 |
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. |
SLITS |
Nov 4 2004, 01:35 PM
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#15
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
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) |
URY914 |
Nov 4 2004, 01:40 PM
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#16
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I built the lightest 914 in the history of mankind. Group: Members Posts: 120,446 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
I'm making some carbon fiber rods.
Should be pretty light. |
Britain Smith |
Nov 4 2004, 01:46 PM
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#17
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Nano Member Group: Members Posts: 2,354 Joined: 27-February 03 From: Hillsboro, OR Member No.: 364 |
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) |
Britain Smith |
Nov 4 2004, 01:48 PM
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#18
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Nano Member Group: Members Posts: 2,354 Joined: 27-February 03 From: Hillsboro, OR Member No.: 364 |
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SLITS |
Nov 4 2004, 01:51 PM
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#19
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"This Utah shit is HARSH!" Group: Benefactors Posts: 13,602 Joined: 22-February 04 From: SoCal Mountains ... Member No.: 1,696 Region Association: None |
"BIG BUCKS" |
URY914 |
Nov 4 2004, 02:00 PM
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#20
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I built the lightest 914 in the history of mankind. Group: Members Posts: 120,446 Joined: 3-February 03 From: Jacksonville, FL Member No.: 222 Region Association: None |
SICK
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