Lightweight crank pulley

[S.B.TEC]

I have a question for everyone in this room.
What are the disadvantages of fitting a lightweight crank pulley?
I'd like to hear from people who have similar vehicles with similar specifications and usage, and who have fitted them and who haven't.

The vehicle specifications and usage are as follows.
The engine internals and ECU are original to Renault.
The use of the vehicle is road and track.

 

[Bankrupt_drunk]

I'm not sure a lightweight crank pully will reduce the reciprocating mass enough to be noticeable. The total mass of the moving engine parts, gear box, drive shafts and wheel at a guess must be around 40-50kg so saving 500g on the pulley is just too small to make a difference on it's own. Worth doing if you're fitting a lightweight flywheel, pistons etc and chasing low weight.
I'd have to check, but i know on some cars the crank pulley is a harmonic balancer, so you may end up with some odd vibrations with it

 

[Bankrupt_drunk]

Have a read of this:

ATI - The Dangers of Power Pulleys & Understanding the Harmonic Damper

ATI harmonic Super Dampers add horsepower and torque to race, street and truck engines.

www.atiracing.com

 

[bozothenutter]

This, it is not ONLY a pulley.
even with a perfectly balanced bottom end, a 4 pot still needs a harmonic balancer (and a pulley).

 

[scullyg40]

This, it is not ONLY a pulley.
even with a perfectly balanced bottom end, a 4 pot still needs a harmonic balancer (and a pulley).

Are you sure, as I believe there are plenty 4 pots that do not have them.

 

[Bankrupt_drunk]

If i had the luxury of a lightened, blueprinted, balanced engine and a race team that would strip and rebuild it every season then i'd definitely have one. But for marginal gains on an occasional track day day i wouldn't bother. To go faster I'd spend the money on ported heads, cams, mapping etc. Or some really lightweight wheels.

 

[bozothenutter]

Are you sure, as I believe there are plenty 4 pots that do not have them.

yeah, pretty much, as it is an inherent property of inline 4 engines (not an engineer, but the construction means you have second order vibrations)
If engines don't have them (which ones?) then the problem might have been solved another way, (dual mass flywheel?)

 

[bozothenutter]

I'm actually looking at Fluidampr stuff as we speak, good idea, but the difference in pulley weight makes it unattractive.
They have a broader rev dampening range because of the viscous fluid combined with an inertia ring.
They don't make a pulley for Clio's, so I took the closest diameters.
Still wondering if some weight can be removed somewhere.
The Honda one looks least promising (unless the thick front ring can be removed), the Subaru one more so, IF you could seperate the front and rear
Standard: 123.0mm (1.0-1.2kg)
530601 Honda S2000 139,7mm (2.65kg)

531101 Subaru EJ 136,525mm (3.13kg)

 

[robzracing]

I've been running a lightweight pulley on my race engine for the past 3 years but that is along with a bottom end that's been dynamically balanced complete with clutch and flywheel. It also allows me to run lightweight pulleys on everything else so I'd hope the overall drag on the engine is reduced.
However, I would expect the rebuild the bottom end every couple of season which is what has been done so far.

 

[S.B.TEC]

I have a question for everyone in this room.
What are the disadvantages of fitting a lightweight crank pulley?
I'd like to hear from people who have similar vehicles with similar specifications and usage, and who have fitted them and who haven't.

The vehicle specifications and usage are as follows.
The engine internals and ECU are original to Renault.
The use of the vehicle is road and track.
View attachment 1527256View attachment 1527257View attachment 1527258

Thank you all!

I don't have time for that now, so I'll get back to you later.

 

[S.B.TEC]

Thank you all for your invaluable input!

In fact, my 172 has been using lightweight pulleys since about 2012.
Of course we knew that it was unbalanced and that the crankshaft would twist.
However, the advantages of the lightweight pulleys were twofold.
1. Good engine response.
2. Semi-permanent use as there are no vibration dampers.
The disadvantages are as follows.
1. Concern about crankshaft twisting.
2. Rapid deterioration of the accessory belt, belt squeal.
Aluminium pulley in the image.

This aluminium pulley has been used since about 2012 for about 5,000 km (31,000 miles).
My 172 currently has a total mileage of approximately 180000km (112,000miles).

I am the second owner and to date I have not had any major engine problems.

I think I'll go back to the original Renault pulley after your feedback.
Original Renault pulleys are available in my country.

The engine of a 172 I know has broken down.
Can I ask your opinion on this subject in another thread?

 

[scullyg40]

yeah, pretty much, as it is an inherent property of inline 4 engines (not an engineer, but the construction means you have second order vibrations)
If engines don't have them (which ones?) then the problem might have been solved another way, (dual mass flywheel?)

Well, my old Polo G40 never had one, and it came with a single mass flywheel as well, and I'm sure, lots of older cars were produced like this.

 

[bozothenutter]

got some drawings off Fluidampr, trying to see if it is possible to add the core of the OEM pulley to a fluidampr ring.

 

[Brane421]

You don't have to worry, I have instaled lightweight pulleys on daily and race clios, also lightweight flywheels and some lightened crankshafts, and cars run for years now with no problem at all.
Check www.elmet.hr for this parts