What do you guys prefer out their for NA cars

*Whould you rather have a Knifed edge crank thats balanced and micro polished *or a stock crank or
* a stock crank thats just micropolished and balanced

PLease let me know your guys Opinions matter thanx

 

street car, basic setup, the stock crank is fine. I would only use a race prepped/knife edged crank for race use or serious builds only. No need for it on a daily driver.

 

micropolish only if necessary. Stock definitely

Save the money for a better vavletrain or rage/hytech header.

 

I use a stock crank that I had balanced..

 

I run a knife edged crank in my street car. The difference is night and day. Its a hard thing to sell to customers because it doesnt create any hp at all.

 

what exactly does a knife edged crank do?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vincent001 &raquo;</TD></TR><TR><TD CLASS="quote">what exactly does a knife edged crank do?</TD></TR></TABLE>

You are basically reducing the weight of the crank, which in turn, reduces the overall weight of the rotating assembly. Furthermore, the knive edged crank would have less resistants as it passes through the oil in the oil pan. The less the resistants, the better.

As for the original post/question, if this is a street application, I would stick with a stock crank. The extra weight will give you some better torque numbers down low and in the mid range.

 

This may be a stupid question, but would polishing a stock crank help at all? Say for restriction purposes, you'd decrease surface friction, and maintain the stock weight for torque numbers.

 

Taking weight off the crank doesn't lose torque.

 

so its like a lightened flywheel?

 

Whenever I see people with knife-edged cranks they often seem to put a sharp knife edge on the leading edge when the most aerodynamic form is actually a round more "blunted" leading edge with a "knifed" trailing edge--kind of like a teardrop shape.

I have never run one or even driven a car with one but I understand it can hurt reliability in a long stroke high rpm application--although I don't have any facts to back that up.

Although I don't believe that knife-edging/lightening will hurt torque output anywhere in the power band.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by d16dcoe45 &raquo;</TD></TR><TR><TD CLASS="quote">I have never run one or even driven a car with one but I understand it can hurt reliability in a long stroke high rpm application--although I don't have any facts to back that up.</TD></TR></TABLE> How high of RPM are we talking about? I've been wondering these same questions for my D16Z6 build (90mm stroke / 7800 - 8000 Revlimit)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by d16dcoe45 &raquo;</TD></TR><TR><TD CLASS="quote">Whenever I see people with knife-edged cranks they often seem to put a sharp knife edge on the leading edge when the most aerodynamic form is actually a round more "blunted" leading edge with a "knifed" trailing edge--kind of like a teardrop shape.

I have never run one or even driven a car with one but I understand it can hurt reliability in a long stroke high rpm application--although I don't have any facts to back that up.

Although I don't believe that knife-edging/lightening will hurt torque output anywhere in the power band.</TD></TR></TABLE>

You bring up a good point.

Would a "teardropped" crank with weight inserts (say tungsten) work? As long as the crank were balanced properly, that is. So, you could maintain the stock weight, but get the benefits of lesser surface friction.

 

I've seen a knifed crank with weight inserts before. Can't think of the shops name, but its up in Canada (I think), built a high power H22. They offer airfoil crank services

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chillinit &raquo;</TD></TR><TR><TD CLASS="quote">

You are basically reducing the weight of the crank, which in turn, reduces the overall weight of the rotating assembly. Furthermore, the knive edged crank would have less resistants as it passes through the oil in the oil pan. The less the resistants, the better.

As for the original post/question, if this is a street application, I would stick with a stock crank. The extra weight will give you some better torque numbers down low and in the mid range. </TD></TR></TABLE>
you do realize that the crank doesnt actually touch the oil in the oil pan in these motors right? your statement about "resistants" is incorrect...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Aquafina &raquo;</TD></TR><TR><TD CLASS="quote">Taking weight off the crank doesn't lose torque.</TD></TR></TABLE>

Aquafina,

This subject has be in discussed many times before. Do you think a lighter flywheel effects torque down low (especially in a heavier vechile)?

I think a lightened crank will effect you torque numbers down low. If your rotating assembly is lighter, you will have less interia. The less interia you have, the less moment you have (ie torque). However, you will benefit from a light rotating asembly up top in the RPM range.

 

It doesn't affect torque. My car isn't any harder to move from a stop with a 7.5lb FW versus the stock FW. and it is already torqueless.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Aquafina &raquo;</TD></TR><TR><TD CLASS="quote">It doesn't affect torque. My car isn't any harder to move from a stop with a 7.5lb FW versus the stock FW. and it is already torqueless.</TD></TR></TABLE>

id have to disagree...i have a 8.8lbs flywheel it takes quite a bit more to get moving from a stop

 

Learn to drive better then. Until I see dyno proof, I'll stand by my statement.

 

lol but i agree with^ x2

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Aquafina &raquo;</TD></TR><TR><TD CLASS="quote">Learn to drive better then. Until I see dyno proof, I'll stand by my statement.</TD></TR></TABLE>

stand by it all you want, if anybody has told you that a lighter flywheel will not harm off line power, they are either misinformed or wrong. a lighter flywheel can't store the energy that a heavier one can. thats why, when driving up a slight incline, one will notice that the car needs more gas to maintain the rpm with a light f/w. that's why cars with heavier f/w can leave the line harder...stored energy. we can all go back and forth about this forever, but, its a fact. whether you believe it or not has nothing to do with the fact that its true. now, if you expecting to see the change on a dynosheet, it won't happen. its not a internal mod

 

they drill a hole and fill the hole with "mallory" I don't know exactly what that is--I assume its some sort of extremely dense metallic material--this way there are no open holes which can add resistance.

In response to dr_latino999--I have a stock stroke a6 which I take to 8100--7500 to 7600 power peak--the friction really goes up in a d16 at that high of an rpm, I personally at this point would not want to mess with a lightened crank in a high rpm d16 if I was looking for "street car" type reliabiltiy--as opposed to a road race motor that might see 1000 race miles between freshening.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Suck my DX &raquo;</TD></TR><TR><TD CLASS="quote">
you do realize that the crank doesnt actually touch the oil in the oil pan in these motors right? your statement about "resistants" is incorrect...</TD></TR></TABLE>Actually, even if the crank doesn't spin through the oil pool when the car is idling in park, in any other condition like hard acceleration or in a corner or going up or down a hill the oil pool is not static--its constantly moving and being splashed everywhere from the movement of the car and inertia of the weight of the oil, and a more aerodynamic crank shape will let it spin with less resistance.


Even the vibration of the motor at high rpm is enough to really get the oil in the pan moving like a rough sea.

 

You said it affects torque, now you say you won't see anything on a dyno.

It doesn't affect power. All you have to do is adjust your launch RPM and its taken care of. I'm barely on the throttle when going up hill. Takes the same amount to go up hill as it does to cruise.

 

The simple fact that you have to adjust your launch RPM is evidence that your rotating assembly does not have the same amount of interia. Unfortunately, I cannot provide you with any dynos given that this isn't a bolt on, bolt off component.

Fact of the matter is, all this is relative to the weight of your car. If you have a really light vehicle, the effects of an extra light rotating assembly are far less significant because there is less static energy to begin with. In a heavier vehicle, you will definately be able to tell that a lighter rotating assembly will be detremental to the power band down low.