Underdrive pulley idea

[Blu Divil]

After reading the flame war on couple of members, I have searched through some books and found following:

The factory balancing jobs are in the magnitude of 10 grams, "aftermarket" balancing is in the tighter tolerances of 0,2 grams.
Before 86 then they used 2 thin metal layer pulleys and at balancing their weight was ignored. After 86 then the famous harmonic dampers took over, the factory included dampers into balancing job.

So if we now reduce weight on one end then it will affect dramatically.
To back that up - I have had a most odd pulley in my car for 2 years, then the factory pulley ran out - our actually the rubber section ran out.
I was in a hurry back then, had friend in a Ford WRC race team, so they replaced the rubber section with machined stainless steel and balanced
that sucker.

Over two years time nothing has happend and everything is in factoryspecs. Im going to try rebuilding my engine (rods, pistons, knife-edged) , I will take the hole thing: crank, flywheel with pressureplate and UD pulley to the balancing.

Any comments on this?

 

[Awdboost]

I've never really seen why people don't want to run pulleys, I guess because people are scared because of all the talk of crankwalk. I don't see how it could cause it.

 

[Tevenor]

Harmonic balancer. You are spinning a weight on the end of a stick. It needs to be perfect, and even when it is, it amplifies any inherent oscillations in the crank. All this for an additional 10 hp at the crank?

Underdrive pulleys are nothing new and neither are the reports on the dangers of undampened crank pulleys (noticed I didn't say dampended underdrive pulleys).

 

[Blu Divil]

What Im getting at is that the factory is using dampened pulleys for their 10 gram balancing and for wear in engine parts.
The engine must last a lot of miles.
For race engine its very good to last to end of race.

So if one can balance the whole thing, crank, flywheel, undampened pulley together to tighter tolerance - there is no urgent need for dampener.
Or actually how big ocillations can the dampener - damper

When you do it right - you gain the extra 10hp and never have to worry about bearings and rubber dampener. (the worst part for me was the rubber dampener went out in the middle of nowhere)

 

[Tevenor]

Even on a balanced rotating system, there are harmonics. You can't 'balance' those out. Ever ride in a car with no shocks? I don't care how smooth the road is, you are going to get bumped.

 

[Blu Divil]

I agree with you - but can the rubber dampener eliminate it?
or it just minimizes them, just like shocks, you ride is better but you still feel the bumps.
- as you can do with whole assembly balancing minimize the harmful effect.

Thats my guess aslo why some people seem to get away with UD pulleys, because their engines are better balanced in factory.

 

[Blu Divil]

to: Awdboost

I think the crankwalk has two issues or actually three
1. too strong pressure plate
2. if you change parts on one of two ends of a crank - these parts are a lot heavyer or lighter from factory parts and you dont get the hole new assembly balanced.
3. just like all Mclaren F1 or Aston Martin engines were handbuilt and each of them had a sound of their maker - you are able to get away with UD pulley, cause actually your engine is balanced better!

 

[Blue97GST]

Would using a lightweight flywheel (say, a Fidanza) contribute to crankwalk?

 

[NDgsx]

Originally posted by Blu Divil
I think the crankwalk has two issues or actually three
1. too strong pressure plate

You mean to heavy release pressure. Clamp load does not put any pressure on the thrust bearing.

 

[Blu Divil]

Originally posted by NDgsx


You mean to heavy release pressure. Clamp load does not put any pressure on the thrust bearing.

Exactly.

About Fidanza without balancing the whole assembly - yes, in my opinion.

Does any of Dsm tuning members have access to engine designing and development software, then he could easily simulate the situation?

 

[Awdboost]

Originally posted by Blu Divil
to: Awdboost

I think the crankwalk has two issues or actually three
1. too strong pressure plate
2. if you change parts on one of two ends of a crank - these parts are a lot heavyer or lighter from factory parts and you dont get the hole new assembly balanced.
3. just like all Mclaren F1 or Aston Martin engines were handbuilt and each of them had a sound of their maker - you are able to get away with UD pulley, cause actually your engine is balanced better!

that very intersting.