balancing and lightening

[JCB]

does this provide any reliability and power gains ?? whilst i am fitting a new engine i am thinking about how to make it a bit more reliable due to the stresses of 12 or so trackdays per year (no road driving -track car only). any advice on improving reliability most welcomed.

[DRIFTBOY]

From what I have read and heard balancing (with crank, rods, pistons, front pulley and clutch assembly) is good for for long term reliability and smoothness of the engine. However, I took my M30 engine crank to a machine shop, when I was rebuilding the 180,000mile engine, to be re-ground and balanced and they said that there was nothing wrong with it and just polished the journals!
If all BMW engineering is that good I doubt there would be be much benefit unless the car is an out and out racing car! Doing only track days then might be worth the expense, even for just peice of mind whilst you are thrashing it senseless!

[Jhonno]

reliability yeah, power gains not really, but will allow the engine to rev up quicker..

[E30BeemerLad]

so that would mean more power then fella

[Dunx]

not gains as such (minimal gains 1/2 bhp for pulleys on an e36 328i for example) - would mean less power loss so more power at the wheels,

[DRIFTBOY]

Yeah, balancing is not about power. It's to do with smoothness of the engine and longevity of the crank bearings etc. Worth doing though if the engine is going to get a really hard time I suspect!

[Kos]

I took my M30 engine crank to a machine shop, when I was rebuilding the 180,000mile engine, to be re-ground and balanced and they said that there was nothing wrong with it and just polished the journals!

m30 cranks dont like a regrind!!

[DRIFTBOY]

I'm glad I took mine to an honest bloke then!
By the way it was Laurence Hodson at Hodson Engineering in Hildenborough, Kent.
He was a top bloke, I totally reccomend him. Really good service and very helpful.

[stevetigger]

A flywheel is a heavy rotating disk used as a storage device for kinetic energy. They come as an alternative energy storage device. Flywheels resist changes in their rotational speed, which helps steady the rotation of the shaft when an uneven torque is exerted on it by its power source such as a piston-based, (reciprocating) engine, or when the load placed on it is intermittent (such as a piston-based pump). Flywheels can also be used by small motors to store up energy over a long period of time and then release it over a shorter period of time, temporarily magnifying its power output for that brief period. Recently, flywheels have become the subject of extensive research as power storage devices; see flywheel energy storage.

A momentum wheel is a type of flywheel useful in satellite pointing operations, in which the flywheels are used to point the satellite's instruments in the correct directions without the use of thrusters.

The kinetic energy stored in a rotating flywheel is


where I is the moment of inertia of the mass about the center of rotation and ω (omega) is the angular velocity in radian units. A flywheel is more effective when its inertia is larger, as when its mass is located farther from the center of rotation either due to a more massive rim or due to a larger diameter. Note the similarity of the above formula to the kinetic energy formula E = mv2/2, where linear velocity v is comparable to the rotational velocity, and the mass is comparable to the rotational inertia.

The flywheel has been used since ancient times, the most common traditional example being the potter's wheel. In the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine, and his contemporary James Pickard used a flywheel combined with a crank to transform reciprocating into rotary motion.

[maxfield]

Who's been doing there homework

[DRIFTBOY]

Couldn't agree more! I forgot to mention the flywheel!
Although a heavy flywheel is designed into engines to help provide a smooth idle (mainly) and to prevent revs dropping too much between gear changes (making the gear change smoother) I have had quite a few flywheels lightened and found a greater throttle response, especially in lower gears and hardly any detrimental effect to anything else. Worth doing in my opinion!

[Jhonno]

so that would mean more power then fella

no it wouldnt.

it means less rotating mass

[E30BeemerLad]

so i was wrong then, oh well

reason why i said what i did was because you said it would spin up faster, which really is a measure of the work rate of an engine or power isn't it?

[maxfield]

It does mean less power loss from the flywheel to the wheels so you could say that i suppose

[Dunx]

Nope - just that less energy/power is needed to spin it.

[E30BeemerLad]

suppose it's a solution for an engine which is going to spend it's life being ragged at the redline, but surely lightening the flywheel will reduce the torque of an engine and torque is what gets you down the road isn't it

[Jhonno]

nope

a flywheel is method of storing energy, it has nothing to do with torque output of an engine

only time you will notice a lighter flywheel is if you climb hills at low speed in 5th gear, and its slightly harder to pull away without stalling depending on amount of lightening

[E30BeemerLad]

maan, I really do know fuck all

[DRIFTBOY]

I'm afraid I disagree.
The affect of a lightened flywheel is more noticeable in the lower the gear that you are in (for the better). But yes, it is more easy to stall the engine due to it dropping the rev speed more quickly.

[Jhonno]

i was talking in terms of detrimentally if you read the posts

in terms of positively the 1st 3 gears will show the biggest difference 1st and 2nd in particular

[Kos]

on the IS' alloy fly wheels make one hell of a difference, and i'm getting one if i dont sell it by next week !!

[reggid]

a light weight flywheel will increase hp on a dyno becasue less energy is used accelerating it and more gets to the wheels. But at full load constant rpm it won't increase hp (the reduced inertia only affects the engines ability to change speed so if you aren't chnaging speed it has no affect, but this is what most dynos use to measure torque). And this is the reason why inertia based dynos can produce different results to eddy current and other dynos and why the speed (ramp rate) at which the dyno operates also affects the power and torque output.

[JCB]

ok -the next question is ...how easy (and thus how expensive) is it to lighten the flywheel and balance the crank ?

[HartgeH27]

I paid £30 to lighten the flywheel and £90 to have the crank polished, clutch,crank,flywheel and front pulley balanced.

[JCB]

thats not bad. i guess my problem is that i am an "engine numskull" and have no idea how to get the crank out !! might have to pay someone to do that for me as well !!!

[HartgeH27]

JCB

Trust me, its worth having done.

[jonb]

Who's been doing there homework

steves a keen user of google. he uses it to spell also.

[stevetigger]

Who's been doing there homework

Steve's a keen user of google. he uses it to spell also.

No I use my knowledge to spell, What do you use? That's right, nothing because your spellings crap!

[benjy]

Handbags at 10 paces ladies! hahahahahahahahaha

[jonb]

steve

theres reasons for my bad spelling. ive destroyed many a brain cell in the past few years.lol

whats this about knowledge.

you annoy people, have done for months. you spout shit, and then you protest that your car is worth 6 grand. that was the final nail in the coffin.

the only stuff that does make sence is what you copy and paste from google.

will you take 5.8k for your unfinished "project"?

[stevetigger]

Why unfinished? Been out all day today! Cheers mate!

Also its not google I use, Its Wikipedia!

[jonb]

well come do gaydon then steve.

you will be paid too! and i will eat my socks.