5 cylinder balance factor

[JP]

OK got a bit of a weird one here that I cant find the answer to. I've always balanced my own rods and pistons as I am in possesion of the relevant equipment to do so. But due to the size of the equipment and the financial investment involved I've always farmed out crankshaft balancing.
This was all fine until I dropped of my 5 cyl crank today at my regular and he asked me for the balance factor of an inline 5 as he's never had to do one before as he mainly deals with yank tanks and the 4 pots I throw him. the yanktanks having a balance factor of 50% and the 4 pots not needing one due to the crank configuration. I really wanted to get my new engine together before going away in August so that I can drive the car on my holiday abroad. But I cant find the formula online to calculate it nor any literature defining the percentage value. Does anyone on here by pure chance have this information to hand? As it is the only thing holding me back from finishing the motor.

I thank anyone with this info in advance.

Cheers JP

[4WheelDrifter]

Balancing the I5 is a specialist job. Take all your rotating engine parts to:

Bassett Down Balancing
Unit 19 Lower Bassett Down Workshops
Basset Down
Wroughton
Swindon
Wiltshire
SN4 9QP
Tel: 01793 812331

[Jamo]

Balancing the I5 is a specialist job. Take all your rotating engine parts to:

Bassett Down Balancing
Unit 19 Lower Bassett Down Workshops
Basset Down
Wroughton
Swindon
Wiltshire
SN4 9QP
Tel: 01793 812331

Have to 100% agree

But see post 14 of this thread http://www.s2forum.com/forum/showthread.php?t=6797

Dont post asking question in that thread though.

If you do a search I believe the crank is balanced at 50%

[JP]

Thankyou for the info Jamo the 50percent was the fig I was seeking a couple more seaches have confirmed this.
The link was an interesting read although a long winded way to make the bobs as these are readily available with interchangeable weights which my guy uses on the v8's.
Anyways thank you once again as it means I can get my new lump finished. Just got to chuck the head on the flowbench now and job's a good un

[Jamo]

Thankyou for the info Jamo the 50percent was the fig I was seeking a couple more seaches have confirmed this.
The link was an interesting read although a long winded way to make the bobs as these are readily available with interchangeable weights which my guy uses on the v8's.
Anyways thank you once again as it means I can get my new lump finished. Just got to chuck the head on the flowbench now and job's a good un

Your forgetting the Pisobiker is just a average owner who balanced it himself, no access to pre-made weights!

[JP]

^^^ very valid point. which makes his achievment all the more impressive really. Definatelly great reading his project and very interesting info.
My background is originally v8's and since then the 4 pot VAG's. I'm learning new stuff on the 5cyl's everyday solely because I bought one as a daily. Threads like Pisobikers are a wealth of info for us all and his abilities a great credit to forums like this.

[S2central.net]

The man is a legend !

[Thuppu]

Can someone explain what is the meaning of the bob-weights when balancing a crank? Why can you not balance the crank to zero, then add the damper and flywheel and balance them to zero? Then weight all rods, bearings and pistons, rings, pinns... made them all the same weight..? Does this destroy the engine?

[driftin jo]

Yes it destroys the engine.
The bob weights simulate the rotational mass of the pistons and rods and are attached to the crank
big ends when balancing.
I our case I think a value of 50 % of the weight of the rod an piston is used.

Also our engines are externally balanced so the crank flywheel and pulley are all balanced as one assembly.

You can have the crank machined to reduce the weigh so that it can be neutral balanced and then use a neutral balance flywheel and pulley.
The crank is still balanced with bob weights when this is done.

If you really want to know more in depth about it give basset down balancing a call they are
very friendly and highly regarded as the best in the busyness when it comes to balancing.

http://www.bassetdownbalancing.co.uk/

[Thuppu]

Yes it destroys the engine.
The bob weights simulate the rotational mass of the pistons and rods and are attached to the crank
big ends when balancing.
I our case I think a value of 50 % of the weight of the rod an piston is used.

Also our engines are externally balanced so the crank flywheel and pulley are all balanced as one assembly.

You can have the crank machined to reduce the weigh so that it can be neutral balanced and then use a neutral balance flywheel and pulley.
The crank is still balanced with bob weights when this is done.

If you really want to know more in depth about it give basset down balancing a call they are
very friendly and highly regarded as the best in the busyness when it comes to balancing.

http://www.bassetdownbalancing.co.uk/

Yeah, with my english skills I propably don't understand anything if I call them and get an explanation.

Most 5 Cylinder Engines in road cars are considered group 2 engines and in most cases are externally balanced, therefore their crankshaft and other rotating and reciprocating parts need to be balanced in the correct manner to achieve a smooth vibration free engine at all times.
Below is a list of items we will need to be able to balance your engine components for you.

Crankshaft
Flywheel
Front Pulley/Damper
Conrods with Shells
Pistons with Rings,Pins & Circlips

Note: All parts must arrive clean and fit correctly before any work can be carried out.


Balancing/Lightening Options (Works Engine Conversion)

It is worth noting that Audi 5 cylinder crankshafts can be converted to a neutral balance state (This type of conversion was done on the famous Audi Quattro works rally car engines) giving you the option to run a more standard and lighter flywheel. In the process the crankshaft is llightened by knife edging the crankshaft and removal of the external balance weights from the damper and flywheel, if a standard flywheel was to be reused.

With the above options completed this will free the engine to rev higher and produce more power, coupled with a perfectly balanced assembly giving an improvement in both efficiency and avoidable wear and tear. Total cost of this conversion would be £380 plus vat and includes all machining work and balancing work, a next day turn around could also be arranged if required (subject to booking)

So if you do it the first way, your balancing is out if you change the damper or flywheel? Thats not good.