ive read about why you shouldnt edge th crank, and it makes perfectly good sense, BUT why not slightly edge it. i think you take off about 4-5 lbs off the crank by completely edging it, but what about only taking 2-2.5 lbs off, after balanceing it of course.

what are your thogughts?

 

If you're going to have it knife-edged, you'd want to balance everything out afterward.

My "thogughts" are that 2-2.5lbs off the crank probably isn't worth the money and/or risk if you believe there is one.

 

prepare for the n00b question. but im curious to know...

what are some of down sides to knife-edging your crank?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by MN_BB4_Si &raquo;</TD></TR><TR><TD CLASS="quote">prepare for the n00b question. but im curious to know...

what are some of down sides to knife-edging your crank?</TD></TR></TABLE>

Not grabbing enough oil? Not to mention weakening it....
HONDA cranks have stood so tough that I wouldn't mess with one beyond the balance and polish. Not sure that the polish is even worth it. The crank is probably the strongest part of the Honda engine.

 

huh, that makes sense now. Well looks like I can scratch out cost of knife edging for my build!

 

another idea behind knife edging besides dropping weight is to reduce windage losses, however, some machinists do not believe that knife edging is the answer to reducing this. Others believe in the tear drop shape.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ::NirVTEC:: &raquo;</TD></TR><TR><TD CLASS="quote">Not grabbing enough oil? </TD></TR></TABLE>

What?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">

What?</TD></TR></TABLE>

i dont think grabbing was the term he was looking for....

 

Look at high revving motors' cranks; the counter-weights are huge. This is one area of the motor I wouldn't feel comfortable messing with oem. It's not like the crank is the way it is because Honda was trying to cut costs. Removing mass and revving higher than stock seems doubly bad.

If you want to save weight of the rotating mass, get something like a Tilton twin-disc/flywheel. You'll save more than 20lbs compared to the couple you want to take of the crank.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">

i dont think grabbing was the term he was looking for....</TD></TR></TABLE>
couldn't think of the right term and thats why I put the ? at the end. I remember my old wrencher telling me something about knife edging being bad because the crank glides through the oil......Old wrencher....who knows....I tend to remember things that older people say about cars in general.

 

i didnt think that our cranks actually "sat" in the oil?......

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">i didnt think that our cranks actually "sat" in the oil?......</TD></TR></TABLE>
Could very well be. He is an old school Porsche racer...
Can anyone clarify this?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ::NirVTEC:: &raquo;</TD></TR><TR><TD CLASS="quote">
couldn't think of the right term and thats why I put the ? at the end. I remember my old wrencher telling me something about knife edging being bad because the crank glides through the oil......Old wrencher....who knows....I tend to remember things that older people say about cars in general.
</TD></TR></TABLE>

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 98vtec &raquo;</TD></TR><TR><TD CLASS="quote">i didnt think that our cranks actually "sat" in the oil?......</TD></TR></TABLE>

They don't. The windage tray is there to block the wind coming off the crank from blowing oil all over the place down there, and the oil is at least an inch below even there, depending on how high you fill it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">
They don't. The windage tray is there to block the wind coming off the crank from blowing oil all over the place down there, and the oil is at least an inch below even there, depending on how high you fill it.</TD></TR></TABLE>
That answers that! Thanks Dr. Mgags7
I'm sure its the case in some applications but obviously not Hondas. If porsche knowledge kept him from making Honda mistakes....awesome! He did have a little bullet of a CRX so he must have done something right.

 

Not to kick the bucket, but I'd be pretty surprised if there are engines that have the crank splashing in oil. That would cause major losses it seems to me, but I'm sure this dude knows something more than I do.

 

Vin said exactly what I was thinking. If you compare the H23 counterweights to H22 ones...You get the notion that higher revving engines = bigger counterweights. I think that the piston and rod assembly threatens to pull the crank with it (especially the faster they travel). It seems counterweights help dampen that motion?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">Not to kick the bucket, but I'd be pretty surprised if there are engines that have the crank splashing in oil. That would cause major losses it seems to me, but I'm sure this dude knows something more than I do.</TD></TR></TABLE>

who knows....we ARE talking about Porsche though!
Ive never seen a sort of windage tray on the V8's I have worked on......We're talking 50's and 60's tech though. They didn't care about loss....there was so much TQ to spare!

 

I'm not sure I'd say that, my reasoning would be something along the lines of "heavier counterweights would help stabilize the crank at high rpm when instability can be a big problem".

I'd like to hear from somebody that actually knows though.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mgags7 &raquo;</TD></TR><TR><TD CLASS="quote">I'm not sure I'd say that, my reasoning would be something along the lines of "heavier counterweights would help stabilize the crank at high rpm when instability can be a big problem".

I'd like to hear from somebody that actually knows though.</TD></TR></TABLE>

wheres Billy at?!?!?! He knows this stuff!

 

i meant too bealance it afterwards. my fault. ill just have my crank polished, and that be that. ill just get a Fluidmpr too save a few lbs.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Dr.Honda &raquo;</TD></TR><TR><TD CLASS="quote">i meant too bealance it afterwards. my fault. ill just have my crank polished, and that be that. ill just get a Fluidmpr too save a few lbs.</TD></TR></TABLE>

Good choice with the fluidampr, most cheap out and buy those crappy unorthodox pullies with no manner of harmonics protection.

 

You know...depending on the general mood...this might get some cool answers in the all motor forum. The time might be right. There's been nothing, but "guess my HP threads lately". The lions might be hungry.

 

It's the older V8's, and still many today that have the crank partially sitting in the oil. Cross-plane V8s (95% of V8s on the road) inherently produce end-end vibration, so the counterweights must be pretty large/heavy to produce balance and reduce vibration.

OT: The reason most V8s produce that gurgling sound is due to the fact of the crankshaft arrangement. Ferrari et al use flat-plane crank arrangements which are basically two I4s slapped together. The advantage is that the counterweights can be much smaller than in crossplane cranks= better response. The downside is packaging and cost, which is the reason almost all engine makers will go for the crossplane layout. They have the balance shafts and all. The main reason Ferrari's sound so good is not the exhaust.

 

Good info Vig, thats a surprise to me.

 

ok i have noticed alot of threads on cranks have shown up lately, i don't mean to thread jack but is micropolishing a crank bad?