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View Full Version : Crank Pulley Theory???



a20a3rdGen
04-19-2006, 10:06 PM
Hey ive heard of a theory with your crank pulley to where if you have a drill press you can drill holes in the pulley itself to where your taking out weight....I dont kno how big people are talking about but i geuss enough weight to where its suppose to add Throttle response. I'm a little iffy on this so im just wondering what the 3GEE community thinks......

ZackieDarko
04-19-2006, 10:25 PM
well yeah if you remove metal you are reducing the rotating mass thus giving you a higher RPM range giving you more power

a20a3rdGen
04-19-2006, 10:30 PM
hmm makes sence to me. But would the weight tooken off reduce the strength and risk it gettin busted or something??...hey i see your from auburn...shoot i live right down the street haha

ICEMAN707
04-19-2006, 10:36 PM
if you mess with the crank pulley, you will mess with the harmonic balancing and you will have extreme vibrations at high rpm. that's why i didn't get a lightweight aluminum pulley for my civic. they are only good for short bursts of runs like on a 1/4 mile track but bad for daily driving or road course race where you run the car for a long time and the vibrations can get very inconvenient. although you can have your stock crank pulley lightened - taking off excess metal like the parts for the a/c and power steering, leaving only the alternator part without messing with the harmonic dampeners. kingmotorsports.com is one such shop that does it for civics. i'm pretty sure they can do the same service for any car's crank pulley. hit them up and ask.

rjudgey
04-20-2006, 08:24 AM
Easy solution to that get it balanced, but really what you should aim for is a single Ally pulley which you could get made if you got the money and contacts and you would have that balanced, but really you should ditch the AC and PS and just run one pulley for the Alternator.
Then after that get the flywheel lightened or an ally one and have that balanced as well with the plate.

Vector
04-20-2006, 10:08 AM
honestly i dont see how drilling holes in a crank pulley to reduce weight will give you anything for power with the other components still riding off of it, now if you got a pully that was smaller in diameter, that could make a minor diference.

AccordEpicenter
04-20-2006, 10:11 AM
they are saying that less rotating mass=more performance, and thats true. If your really care, aluminum flywheel > lightened crank pulley by far. What you guys MUST realize is that the stock honda crank pulley is also a harmonic balancer, and if you mess up the balancer portion or eliminate it then the bottom end and bearings will eat itself to metal shavings (seen it happen) so i would highly reccomend not eliminating the harmonic balancer

Vector
04-20-2006, 10:19 AM
they are saying that less rotating mass=more performance, and thats true. If your really care, aluminum flywheel > lightened crank pulley by far. What you guys MUST realize is that the stock honda crank pulley is also a harmonic balancer, and if you mess up the balancer portion or eliminate it then the bottom end and bearings will eat itself to metal shavings (seen it happen) so i would highly reccomend not eliminating the harmonic balancer

flywheel yea i can understand, look how big it is lol:cheers:

BDaccordguy
04-20-2006, 11:37 AM
ive got an aluminum UDP on my beretta, but the stock one wasnt a harmonic balancer. Its about an inch smaller in diameter, also about half the wieght of the OEM peice. I noticed some gains, and was dyno proven for about 5hp at the wheels... and 8-10 at the crank. In your case, i would probably leave it alone, and find a lightened pulley set, or make one work for the other pulleys.

a20a3rdGen
04-20-2006, 01:58 PM
So where do you think i can get a lighter pulley set??

Accordtheory
04-20-2006, 05:44 PM
waste of time and money..

lostforawhile
04-20-2006, 07:29 PM
they are saying that less rotating mass=more performance, and thats true. If your really care, aluminum flywheel > lightened crank pulley by far. What you guys MUST realize is that the stock honda crank pulley is also a harmonic balancer, and if you mess up the balancer portion or eliminate it then the bottom end and bearings will eat itself to metal shavings (seen it happen) so i would highly reccomend not eliminating the harmonic balancerthank you!someone on here who said what i was about to. the difference that little bit of metal makes vs the engine damage is not worth it. that tiny bit of weight could be better saved by not supersizing that meal you ate at mc. donalds. or you could throw the stereo and all the cd.s,the interior,the carpet,the pesky heavy back seat,the glass,scrape off the paint,it depends on how much weight you want to save. don't forget the paperclip you left on the floor,it's a whole tenth of a gram. for crying out loud this is not a freaking drag car where you need to save those .001 of a second.

bobafett
04-20-2006, 10:07 PM
lol however 5whp might be realistic gain for a lightened crank pulley, and thats VERY worthwhile, and every pound lost on rotating parts is FAR MORE beneficial than static weight lost by stripping parts out of the car. its like if you removed 60 lbs of shit from your trunk its not that much, but if you added that 60 lbs to your wheels or your flywheel, ur car would be god damn slow.

if shaving off the PS and AC grooves on teh stock pulley is safe and doesnt mess with the harmonics, I am alllll for losing them to drop 2-3 lbs. because im sure its worth at least 2-3whp, and that is certainly worth the time.

HostileJava
04-21-2006, 04:10 AM
if shaving off the PS and AC grooves on teh stock pulley is safe and doesnt mess with the harmonics, I am alllll for losing them to drop 2-3 lbs. because im sure its worth at least 2-3whp, and that is certainly worth the time.

I wouldn't do that, unless you have it proffesionally rebalanced.

rjudgey
04-21-2006, 04:20 AM
You can get a pulley of a JDM or Euro 2G lude that only has a single V belt groove for alternator, yeah you'd have to change your water pump pulley and alternator pulley but can be done, these are very light and as far as i can see do not have any harmonic balancing weights on them, they also have massive drilled holes in the pulley too also great for sticking a crank wheel for ignition.
But as the others said i'd spend money on machining off the ps and ac part ahve it balanced and job done, then get a ally flywheel too and you'll be well away!!

bobafett
04-21-2006, 07:20 AM
I wouldn't do that, unless you have it proffesionally rebalanced.

haha maybe your not familiar with my build. everything has been proffesionally everythinged. :D
it would be done by the machine shop that built my motor, which i DEEEEFFFINITELY trust to do the job right. :D

rjudgey are those plentiful around your parts? i sure wouldnt mind a good light CP, and alt and wp pulley to go with it.... if those are parts you can find easily enough, let me know what it might set me back. im certainly interested.

guaynabo89
04-21-2006, 12:53 PM
Actually if you have a quality machine shop nearby they should be able to balnce the pulley out if anyone has any fears. I personally had my complete rotating assembly balanced including flywheel, crank, rods, rod pins, pistons, and crank pulley.

Just for the record heres what a good lightened aluminum crank pulley looks like on the a20.
And this ones been going strong for about 5 years and 15,000 miles.

http://www.imagestation.com/picture/sraid204/p6df4cb689927a3ade2f096658b086649/ef54fb37.jpg

Oh and I also have the power steering, alt (underdriven pulleys) and the water pump in aluminum

bobafett
04-21-2006, 06:59 PM
did you get those made just for you, or did you luck out and buy them from some weird chance of luck

and more importantly, how did you like the power gains?

HostileJava
04-21-2006, 07:23 PM
I was under the impression that the inside of the pully had to be coated with somthing to keep the belts from tearing up the aluminum, but it looks like you are just running bare aluminum there?

MessyHonda
04-21-2006, 07:28 PM
Actually if you have a quality machine shop nearby they should be able to balnce the pulley out if anyone has any fears. I personally had my complete rotating assembly balanced including flywheel, crank, rods, rod pins, pistons, and crank pulley.
Just for the record heres what a good lightened aluminum crank pulley looks like on the a20.
And this ones been going strong for about 5 years and 15,000 miles.
http://www.imagestation.com/picture/sraid204/p6df4cb689927a3ade2f096658b086649/ef54fb37.jpg
Oh and I also have the power steering, alt (underdriven pulleys) and the water pump in aluminum

where did you get the pullys or did you have to take them out and get them done....i want to take off some weight but its a bitch to turn the wheel with no power stering pump when parking. some onder drive pullys would make the car faster right?

Accordtheory
04-21-2006, 09:10 PM
I wrote earlier that this is a waste. I think as far as mass reduction, it is. However, I think that as far as underdriving the p/s and a/c, it isn't. Underdriving your alternator makes no difference, if you understand how electric motors/alternators work, you know why. You shouldn't really underdrive the h20 pump in my opinion for normal driving, but for high rpm, that is a good idea.

The reason why I say it isn't worthwhile as far as mass reduction goes is that the small amount of mass you could remove is too close to the rotational axis to make a difference. Effort would be much better spent on a lighter flywheel. For those of you contemplating an undampened aluminum pulley, there is a long, picture filled thread on h-t about the undampened ctr pullies causing engine destruction by shattering the oil pump (b series oil pump is directly driven by the crankshaft, so the harmonics go right into it, unlike the a20) While I don't see anything like that happening on a low rpm n/a a20, I would say that it is generally accepted that a pulley lacking any dampening will reduce the bottom end bearing life. I think a lighter flywheel and a fluidampr would be the way to go.

BDaccordguy
04-22-2006, 07:27 PM
I was under the impression that the inside of the pully had to be coated with somthing to keep the belts from tearing up the aluminum, but it looks like you are just running bare aluminum there?


mine is running on bare aluminum as well, and has been since the end of October.

mykwikcoupe
04-22-2006, 09:30 PM
underdrives are ok to a point. you need to realize however that the total gain is like 6-15 hp. on my thunderbird by going with aftermakret rods, pistons and such i saved 520g a set. thats 520gx6 so as a recpicating mass thats a total of like 3 lbs. Huge. As far rotational masses thats your low end torque and where its generated. Does everyone remember newtons law os mass in motion? Anyway without the pysics lessons you NEED the rotational masses. cut as far down on the recipricating masses you can and still be strong. Im going to run stock flywheel, yes it wont rev as fast but Ill kepep my torque up which is what the a20a are biult for.
Knife edge the crank, lighter pistons, rods, stuff like that. youd be amazed how effective it was on my bird. I lost.2 compression and was alittle owrried about it but when you hit the gas it goes

accord upset
05-17-2006, 02:51 PM
i understand mass = lowend torq,,+ mass also means forever to spin up ur rpms. i wanna lighten a stock flywheel and was thinking bout the crankpully also i dont run a/c or p/s so i wouldnt think you would need that part of the pully. some have brought up the concept of harmonic balencer or dampener. i work on cars all day im a mechanic,, i see many harmonic balencers from the inside out this is what i see.usually theres the part that connects to the crank made of some sort of metal, then a rubber,urathane or fluid dampner, and an outer ring made of metal that the v-ribs of your belt ride on.. (on most cars that require dampning) but im sure u guys have looked at our crank pullys,,, its just that a crank pully solid metal. it does not look like there is anything to do any dampning on our crank pully.(it is most likely balenced thou) my question is if u have a machine shop cut the ps and ac parts of our crank pully off ,lighten the rest ,and have them rebalence it would that work, or would someone be rebuilding there bottem end in a few months. if it wouldnt work please explain in detail as to why it would not. ps has anyone tried this and fu**ed there bottem end or tried it and is still running the setup.

HostileJava
05-17-2006, 03:03 PM
I'd say don't bother with it unless you are also lightening the flywheel and at that point take it all to a shop, have them lighten the flywheel, shave the unnessary stuff off the pully and have the whole thing balanced as one.

accord upset
05-17-2006, 03:34 PM
thats my plan but will it work or destroy my lower end?

HostileJava
05-17-2006, 03:49 PM
thats my plan but will it work or destroy my lower end?

No, as long as you ahve the flywheel/crank/gear/pulley balanced as one you should have no problems with vibration.

AccordEpicenter
05-17-2006, 04:02 PM
lol... and dynamic balanced with the rods and pistons too. Its hard to eliminate the harmonics, its easier to dampen them. Even if everything was perfectly balanced, there are no guarantees

HostileJava
05-17-2006, 04:05 PM
Yeah I didn't really mean to place the "what so ever" in there and I edited it out. My point being that he should have them all balanced together since they will end being basically one big rotational mass.

AccordB20A
05-17-2006, 04:08 PM
yeah my exs civic sucked for torque with a lightened flywheel. in 5th gear at 100 km/h it cdnt even go up a slight Hill without loosing speed... yet the 1st gen teg i had with the same engine started at 100 at the bottom of the hill and does 130 at the top. makes ya use HEAPS more gas and all. Im leaving my flywheel how it is but yeah they are great for raceing around with.

accord upset
05-18-2006, 09:53 AM
so what you guys are saying is to just wait till i do my rebuild this winter and get it all balenced after im threw, like everything dynamically balenced (rods,pistons,crank,crank pully,flywheel) did i miss anything? ps anyone know what the highest compression u can run on pump gas without it knocking

AccordEpicenter
05-18-2006, 02:57 PM
that depends on your tuning and what octane pump gas you have available.

A20A1
05-18-2006, 03:20 PM
I don't think the motor itself would make more power.

But it will have more power available to the wheels but lose the momentum quicker to the wheels with a light weight, while the regular weight flywheel will have less power available to the wheels but what is already in the flywheel momentum is slower to drop off to the wheels.
However the motor (combustion) applys the same amount of torque to turn the crank no matter if you stick on a light weight flywheel or a frozen turkey... its not like you get more air and fuel or less and and fuel because you lighten a flywheel... you only change how much of that energy is used or lost in this instance. Light weight = Less loss of HP out of the air fuel mix combusted becasuse there is less mass to rotate.

So in essence you free up horsepower that you had previoulsy wasted to turn a heavy flywheel, not make more power, the power is pretty much set... you want to try and use as much of it as efficiently as you can.

If you can shift fast then you can still do good with a lightweight flywheel right? I mean if you keep the revs up all the time it's fine. You just have less time to shift cause the rpms will drop quicker with the lightweight flywheel.

Accordtheory
05-18-2006, 03:53 PM
Why do people think a lighter flywheel kills your low rpm torque? Because thye have no idea what they are talking about. The less mass, the less energy it takes to accelerate it. The same energy, less mass= quicker acceleration. It might be harder to let the clutch out at a stoplight, but your car will accelerate more quickly at any engine speed with a lighter flywheel.

And yes, this does show up on an acceleration dyno. Or in the quarter mile.

guaynabo89
05-18-2006, 04:53 PM
Why do people think a lighter flywheel kills your low rpm torque? Because thye have no idea what they are talking about. The less mass, the less energy it takes to accelerate it. The same energy, less mass= quicker acceleration. It might be harder to let the clutch out at a stoplight, but your car will accelerate more quickly at any engine speed with a lighter flywheel.
And yes, this does show up on an acceleration dyno. Or in the quarter mile.

Agreed.
My car breaks the wheels loose anytime I want it to. I lost nothing and gained quicker accelaration

Oh and Boba I had the pulleys made a while back by a local man that has a machine shop and works pretty much solely on aluminum.

He made me all the pulleys a fuel rail valve spring retainers. and more misc things i cant think of right now.

the gains were good. All this talk about losing low end tourque while correct I havent found it to be the case in my perticular car. With all that alum the car accels like it has nothig better to do than accelarate. All in all it was worth it. Besides what hapaned to that formula for every pound taken off the rotating assembly is a X amount of horses gained.

The pulleys werent coated with anything. I do notice that they will slip easier than regular pulleys when wet or to loose etc.

HostileJava
05-18-2006, 04:57 PM
Thanks for chiming in. I have a lightened flywheel and I wanted to have the accesories machined off of the crank pulley or have a new one made and all this talk back and forth was concerning me. Glad to hear somone who actually experienced it on our engine say it helps more then hurts.

accord upset
05-19-2006, 07:18 AM
im with a20a1 on this one. example heavy flywheel drop clutch by accdent ur car lurches and tries to die. light weight flywheel u do the same and ur engine dies meaning lighter will be extra touchy at lights, stop signs ect.,,, it will give you unreal response from ur engine thou. no harm in not wasting horsepower turning ur engine = lighten ur rotational mass and it takes less to turn ur engine... think u get ur car up to 80 and stop it, now hook a trailer up to it and do the same. its easier to stop just the car cause it's lighter. so if you lightend ur engine will be more suseptable to jars,jerks,hills,anything that would cause it to work harder will cause a drop in rpm. the only cure to the rpm drop is more horsepower, if your engine is putting out 500 hp than it wont matter how touchy it is.

here's a artical on mass and inertia http://en.wikipedia.org/wiki/Inertial_mass