Lightweight Pulleys

[Bennoz]

The motor is out finding things to do (RB30)

Light weigh pulleys

Are they worth it ? Has anyone gone down the path of changing them over

would like to hear your thoughts

also if any one knows if can buy them from anywhere (iam in melb)

or would i be better of going to some kind of metal shop with my old ones

and ask to turn them up, if so what kinda of metal/alloy would i bee looking at to get them mad off

Cheers

[s13rb26]

your wasting your money.

[s13rb26]

The motor is out finding things to do (RB30)

Light weigh pulleys

Are they worth it ? Has anyone gone down the path of changing them over

would like to hear your thoughts

also if any one knows if can buy them from anywhere (iam in melb)

or would i be better of going to some kind of metal shop with my old ones

and ask to turn them up, if so what kinda of metal/alloy would i bee looking at to get them mad off

Cheers

<{POST_SNAPBACK}>

id only use them for looks,

but yer

alloy with holes in it like how the sr20's use (i.e URAS pullys etc)

that way they are mega light

[Bennoz]

Is there much power gain to be made

to justify spending the money ?

[T04GTR]

what ever you do, dont touch the crank pully :lol:

all the other ones are fine, but having said that, if you have a bigmac before you drive it you would of made them redundant (with that extra balast of a burger lol)

[s13rb26]

power vs money-

no

[PHATR32]

its probly been asked a million times, and i cbf'ed searching, but dont the crank pulleys need a harmic balancer?

will any damage result from not having one?

steve

[rev210]

The motor is out finding things to do (RB30)

Light weigh pulleys

Are they worth it ? Has anyone gone down the path of changing them over

would like to hear your thoughts

also if any one knows if can buy them from anywhere (iam in melb)

or would i be better of going to some kind of metal shop with my old ones

and ask to turn them up, if so what kinda of metal/alloy would i bee looking at to get them mad off

Cheers

As mentioned you don't change the crank pulley.

However yes they are worth it.

Reduced inertia is always worth the bother when it comes to the pulleys. It gives increases in the 'response' of the motor. The trust set I have reduced the pulley setups weight by around 2kg. The switching over to an electric thermo fan (thermo switched) reduces this by another kilo or two as well. After that you have a gain similar to a lightweight flywheel in basic inertia reduction.

What does reduced inertia give you?

No horsepower gains as such, but even better a gain in accelleration. A reduced time taken to reach rpm in any given gear.

Reducing inertia is the smart path to reliable speed. It doesn't increase wear on anything unlike horsepower increases. For that reason paying a little more for an accelleration gain up front is worth it because you DONT KEEP PAYING FOR IT.

Most people don't understand this or have more often than not have never been told.

while I'm on the topic I have a good idea that a $2,000 carbon fibre tail shaft makes for rather good value for money when you consider you are saving fuel ,contributing less wear and require no extra supporting mods to go significantly faster 0-100kmh.

Once I get round to installing one I will time it on the dyno for those who's brains can't concieve of anything other than what their mates tell them about how to make a car go quicker.

[lukits01]

Suppose we leave the crank pulley stock, what other pulleys can you change?

A/C? Power Steering? anything else?

and where to buy them? never seen them made for RB engines, only SR

[rev210]

trust make a set for the RB26dett. Alternatively get some made out of alloy would probably cost less.

UniqueAutoSport.com.au may have a set?

[Sick_R31]

http://www.fabre.com.au/news.htm

[Busky2k]

I remember reading once on GFB's site which said they don't make light weight pulley's for the RB motors because of reliability reasons.

[rev210]

gfb kits include the replacement of the harmonic balancer with a plain pulley. RB's need a balancer

The Ross balancer is very nice, saves 3kg off the weight there too.

[Dahtone Racing]

im getting a gilmer drive pulley kit made up for my car

anyone know much about them on RBs??

[FATGTS-R]

Ok so reducing the inertia by lightening the pulleys is a good thing.

By underdriving the gearing is going to improve the response further, possible slight power increase?

So, doing the above is in turn going to reduce load on the engine correct?

Just thinking aloud but load is what helps a turbo spool, so would reducing the load and getting the increase in acceleration speed be offset by a later spooling turbo as load has been reduced?

[rob82]

Ok so reducing the inertia by lightening the pulleys is a good thing.

By underdriving the gearing is going to improve the response further, possible slight power increase?

So, doing the above is in turn going to reduce load on the engine correct?

Just thinking aloud but load is what helps a turbo spool, so would reducing the load and getting the increase in acceleration speed be offset by a later spooling turbo as load has been reduced?

I love this topic. Any way to reduce roational inertia will increase acceleration of the enigne and acceleration on the raod. Increase in acceleration of the engine means that additional timing can be added which increases torque. And as for turbo engines it doesn't matter if your reducing the load on the motor becuase it will be offeset by the addition exhaust gas flow due to the quicker reving motor.

And as was said earlier never remove a harmonic balancer on a motor that was designed to use one, unless you want to twist you crank.

[Wazz]

excellant topic.. as for the pulleys i have them on my rb26 in my s13 cost me 300 bux for the set how ever you might have to be a bit carfull seeing as there goin on a rb30.. find out which rb20 or 25 has the same size pulleys because rb26 to rb20/25 have different size pulleys especialy water pump pulley

[Mik]

As mentioned you don't change the crank pulley.

However yes they are worth it.

Reduced inertia is always worth the bother when it comes to the pulleys. It gives increases in the 'response' of the motor. The trust set I have reduced the pulley setups weight by around 2kg. The switching over to an electric thermo fan (thermo switched) reduces this by another kilo or two as well. After that you have a gain similar to a lightweight flywheel in basic inertia reduction.

What does reduced inertia give you?

No horsepower gains as such, but even better a gain in accelleration. A reduced time taken to reach rpm in any given gear.

Reducing inertia is the smart path to reliable speed. It doesn't increase wear on anything unlike horsepower increases. For that reason paying a little more for an accelleration gain up front is worth it because you DONT KEEP PAYING FOR IT.

Most people don't understand this or have more often than not have never been told.

while I'm on the topic I have a good idea that a $2,000 carbon fibre tail shaft makes for rather good value for money when you consider you are saving fuel ,contributing less wear and require no extra supporting mods to go significantly faster 0-100kmh.

Once I get round to installing one I will time it on the dyno for those who's brains can't concieve of anything other than what their mates tell them about how to make a car go quicker.

You are contradicting yourself there...just a little though. Yes, lightening things that turn, reduces inertia in the torsional axis, and you say that this won't lead to an increase in horsepower, which it won't as everyone knows, you can't create energy. You say that the car will accelerate faster...which it will, but it is impossible for the car to accelerate faster without having more power.

Accerlerating something that turns requires a certain amount of torque, for a certain amount of time (A certain amount of power) Just like accellerating something in the linear plane requires a certain amount of force for a certain amount of time.

When rotating parts are lighter, less torque is needed for less time to accelerate to the same RPM. (IE less power). So, you are consuming less power to accelerate rotating parts, you have more energy in a given second (power) to use to accelerate the car in the linear plane.

IE, you are putting more power down to the road OR the dyno. So...the power 'gain' should be able to be measured on the dyno.

Looking at it anohter way...if you think about how a dyno works, it lets the engine accelerate in RPM a certain number of RPM per second. The dyno then measures how much torque it needs to hold the engine at this rate of acceleration. Power is then calculated. So, if the car is going to accelerate faster, the increase in power will show on the dyno.

Also, a lightweight carbon prop shaft that saves say 10kg, will make no where near as much difference as a lightened flywheel that saves 5kg.

The reason is the steel prop shaft's moment of inertia is much lower than that of a the flywheel. IE. The average mass of the prop shaft is much closer to the axis of rotation than it is for the flywheel.

The lower the moment of inertia, the less torque is needed per second to accelerate the mass to a given RPM. I can’t remember the exact relationship, but it would be a square law. I could dig it out a of an old physics textbook if I could be bothered.

You can test this by rolling a ball bearing, a shot put and a steel pipe down a hill. All else being equal, the ball bearing and the shot put should reach the bottom at the same time. The pipe should arrive last, because it has the highest moment of inertia, meaning more energy is wasted accelerating the pipe in the torsional axis.

[Roy]

The reason is the steel prop shaft's moment of inertia is much lower than that of a the flywheel. IE. The average mass of the prop shaft is much closer to the axis of rotation than it is for the flywheel.

I tend to agree, but it would be interesting to see.

[rev210]

Mik,

Accellerate without more power you are saying no?

I think there is a little confusion here. Mass is a part of the equation. If we lessen the mass and apply the same power to it's accelleration it takes place faster.If the same engery is used and 'conserved' in the equation when mass is reduced,

accelleration (over a delta T ---- remember it's meters per second per second)

or velocity (moment-------meters per second) is increased to give the same value in a blunt expression. Variations of this sum occur according to round and round or linear motion but, pretty much thats what happens.

Tailshafts are hollow too, this means the outer edge contains the mass, the middle is air. Then there is the twisting forces on them which the flywheel doesn't have to cope with etc....

Propshaft wise it seems that there is more complicated equations involved than the simple approach we would taken. To save headaches on this thread I suggest that you email the guys at www.acpt.com they are the aerospace company that make the shafts for Mines and others.

All I can comment on is the experience I have had over the years making bits lighter and going faster as a result. The fact that people have trouble 'getting it' has meant I end up going quicker often in the same vehicle with less money spent and less power. Like people really ought to consider 'learning how to drive your car' as a mod of great value for money. This approach may have an up front cost but, it's free thereafter.

Extra power always costs you more for every second you use it.