I am just curious if lightining a crankshaft in a D16 is really worth it? The engine is a D16A6 bottom end with a D16Z6 head. I know the theory behind it, less moment inertia, but is it really worth it? Will I notice a difference with it? Eventually, the head is going to be rebuilt with aftermarket valvesprings and a big cam, so I will rev it to at least 8000rpms and I'm thinking it may be worth doing to help it rev, but what would ya'll suggest?

 

just get a lighter flywheel. you will notice a difference.

 

hmmm.......but would lightning the crank be worth it? Reason I'm asking is because I'm debating to do a rebuild as my car smokes and was curious if it would be good to do if I'm going to rev the D16 to at least 8krpm? I would add a lighter flywheel as well.

 

yes it would help but you have to understand those counterweights on the crank are there to help absorb some of the harmonic distortion from the rotating assembly. Lightening it will help but it will also put more wear on the rotating assembly especially the bearings.

 

Well, the car at that point wouldn't be a daily driver. It was be a fun/race car. So it wouldn't see many miles. I realize what you are saying about faster wear.

 

I think it could very well hurt it in revving high. The crank is one of those pieces that I'm sure they went out of their way to make as light as possible while still doing its function.

Type R crank is heavier than a GSR....

 

Lightening a crank is definately going to increase your rpm, but you're going to lose some torque. This can be made up for by an overall increase in horsepower. The area below the line in your torque vs. rpm cure will be greater therefore producing more power. There are several example which we can look at to prove this point. Let's take a tractor for example. A 60 hp tractor with a very low redline is a big engine in a tractor. Well, to make 60 hp at very few rpm's you're making gobs of torque. We'll take sportbikes as our next example. Absolutely no torque at all, but an R6 does make over a 100 hp due to the 16k redline. So...... a question for you, "Would you rather ride an R6 or drive a tractor?" I've lightened many cranks for engines I've built and have always been happy with the results. Just be sure to have everything balanced. The vibration caused by components being out of balance is exponential with rpm. I had a friend that balances tell me a story one time about balancing an airplane crankshaft. He usually balances normal engines to 10k and 16k for race applications. When he started to balance the crank it was well over several ounces out because his balancer couldn't even read it due to all of the vibration so he had to call the owner and tell him. Funny thing is that aiplane propellers distort at over 2600 rpm and can never run over that. So in reality the crank was very close to being balanced for the rpm it was to be run. I have lightened many cranks for many different applications and have always been happy with the results, as long as everything else was done right.

 

Its really not worth it, lightening it will also make it weaker; getting a lighter flywheel will have more of an impact on revs.
comparing a tractor and a bike.....funny

 

Why would you lose torque by lightening a crank?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mmuller &raquo;</TD></TR><TR><TD CLASS="quote">Its really not worth it, lightening it will also make it weaker; getting a lighter flywheel will have more of an impact on revs.
comparing a tractor and a bike.....funny </TD></TR></TABLE>

Make it weaker? How?

Plus, I have a lightened and knife edged crank for sale along with a set of AEM forged rods with Arias high comp. pistons. The crank is used, but the pistons and rods are new. And everything has been balanced together to 1/4 gram. Let me know if you want any more info. Oh yah, it is all for a D16A6.

The rules for my racing class got changed, so I can legally run a B16 in my 89 Civic bu-bye D-series.

Just in case you are wondering why the hell I have this stuff and selling it.

 

How much are you looking to get for the crank with rods and pistons?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sicivic &raquo;</TD></TR><TR><TD CLASS="quote">How much are you looking to get for the crank with rods and pistons?</TD></TR></TABLE>

I would sell the lot for $1500 US. You are basically getting the crank (knife edged) and everything balanced for free. That is a little less than what I paid for the pistons and rods.

The balancing and knife edging cost me about $350 and it was done by Leitner Bush in Toronto, Canada.


Modified by MightyMouseTech at 5:16 PM 2/27/2004

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Building_rice &raquo;</TD></TR><TR><TD CLASS="quote">Lightening a crank is definately going to increase your rpm, but you're going to lose some torque. This can be made up for by an overall increase in horsepower. The area below the line in your torque vs. rpm cure will be greater therefore producing more power. There are several example which we can look at to prove this point. Let's take a tractor for example. A 60 hp tractor with a very low redline is a big engine in a tractor. Well, to make 60 hp at very few rpm's you're making gobs of torque. We'll take sportbikes as our next example. Absolutely no torque at all, but an R6 does make over a 100 hp due to the 16k redline. So...... a question for you, "Would you rather ride an R6 or drive a tractor?" I've lightened many cranks for engines I've built and have always been happy with the results. Just be sure to have everything balanced. The vibration caused by components being out of balance is exponential with rpm. I had a friend that balances tell me a story one time about balancing an airplane crankshaft. He usually balances normal engines to 10k and 16k for race applications. When he started to balance the crank it was well over several ounces out because his balancer couldn't even read it due to all of the vibration so he had to call the owner and tell him. Funny thing is that aiplane propellers distort at over 2600 rpm and can never run over that. So in reality the crank was very close to being balanced for the rpm it was to be run. I have lightened many cranks for many different applications and have always been happy with the results, as long as everything else was done right.</TD></TR></TABLE>

Damn, someone toss me a life preserver, cause I'm almost drowning in the BS!

WTF are you comparing a tractor to a sports bike for? Aside from the motor, don't you think weight has something to do w/ that? How about the balancing to a certain RPM....never heard of that one. If it's balanced at 10k, it's balanced at 2k. It's just that the minute amount that the crank may be out of balance will start to wreak havok at higher RPM's, while at lower RPM's the crank can be more out of balance and nothing will break.

It's not worth lightening the crank. It has been proven that a crank with heavier counterweights is much better for revving high. You may gain a bit of power from the lighter rotational mass, but the heavier counterweights will dampen the crank at higher RPM's, and generally store more power and make a better motor. Put the money somewhere else.

 

well i don't even think you'll win hp on the dyno from removing weight, it'll do like a lightweight flywheel, put your power faster to the ground, nothing more.

but since you have more harmonics, yes you may gain some acceleration time in the low rpm, but you may not be able to run at higher RPM.

balanced and micro-polish it, that's it!

 

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

I would sell the lot for $1500 US. You are basically getting the crank (knife edged) and everything balanced for free. That is a little less than what I paid for the pistons and rods.

The balancing and knife edging cost me about $350 and it was done by Leitner Bush in Toronto, Canada.
</TD></TR></TABLE>

OOps, gotta stop doing currency conversions in my head when I am tired.

I would be looking for about $800 US.


Modified by MightyMouseTech at 10:19 PM 3/1/2004