Lightweight pulleys - how effective?

[Galaxian 6]

I've been thinking about the effect of removing weight from the moving parts of the engine, e.g. flywheel, pulleys etc  and I was wondering just how effective they are. basically, I need the man maths!

 

so, I came across this description - is this right? does it really effectively lose 45 KG ?

 

The PERRIN Performance Crank Pulley weighs just 1.2 lbs, which is 3.7 pounds lighter than the stock OEM crank pulley. This reduction in weight from the crank shaft is equal to removing more than 100 lbs of vehicle weight! Throttle response, horsepower and torque are all increased with this easy to install part

 

so 3.7 lbs is 1.67 KG, so going on from here, if I fitted the fensport pulley kit that is 2.095 lighter do I then effectively remove approx. 56 KG ??

 

and if I fit a lightened flywheel, does the same maths apply?

 

thanks for any feedback.

[Keethos 842]

No idea about the maths side but not sure about the horse power increase. You definielty get more response and urgency to get going but I've not really noticed or seen more power in any way. Though I wondering if it's now too sensitive sometimes as I have noticed that my car feels a lil more jerky sometimes and it often feels like when I get a sudden jerk, my foot moves a bit which ends up adjusting the throttle thus making the car jerk more.....or it could be something else entirely that makes my car feel jerky.

[Stan Hawrylak 23]

I've been thinking about the effect of removing weight from the moving parts of the engine, e.g. flywheel, pulleys etc and I was wondering just how effective they are. basically, I need the man maths!

so, I came across this description - is this right? does it really effectively lose 45 KG ?

The PERRIN Performance Crank Pulley weighs just 1.2 lbs, which is 3.7 pounds lighter than the stock OEM crank pulley. This reduction in weight from the crank shaft is equal to removing more than 100 lbs of vehicle weight! Throttle response, horsepower and torque are all increased with this easy to install part

so 3.7 lbs is 1.67 KG, so going on from here, if I fitted the fensport pulley kit that is 2.095 lighter do I then effectively remove approx. 56 KG ??

and if I fit a lightened flywheel, does the same maths apply?

thanks for any feedback.

Not sure about the man maths, but the reduce rotating mass route has worked for me. If you're going to reduce rotating mass, you're best off reducing it everywhere you can so you can feel the cumulative effect, rather than just doing pulleys etc which you 're probably not going to notice much.

On my car I've got the pulley kit, flywheel, carbon prop and lighter wheels (although oem wheels already light). They're probably all worth a few wheel hp each. The prop is reckoned to be about 5 whp, not a lot but as I say combined with the others, makes a difference. More throttle response, better pickup. If you shorten the final drive as well, then you've got so much more push out of the turns. The standard ratios are too wide for an NA. I remember a Toyota engineer saying the ratios had been tuned for 'environmental performance'!!

Doing TSS last year, some of the speeds I was pulling on the straights weren't far behind the forced induction crowd. There's more you can do of course, filter, intake, header, exhaust, power blocks. It's possible to make an NA go quickly but to do it properly might cost you as much as forced induction!

Haversack

[Guest]

I have read that having lightweight flywheel AND pulleys can lead to premature bearing failure?

I have no evidence, and have not witnessed the issue, but I have read about it? Any thoughts out there??

[Kodename47 446]

I have read that having lightweight flywheel AND pulleys can lead to premature bearing failure?

I have no evidence, and have not witnessed the issue, but I have read about it? Any thoughts out there??

Some say it will as you've removed the harmonic damping of the crank, others say that the flat 4 doesn't require it and will be fine. Who you believe is up to you, personally I'd err on the side of caution and I won't be doing it. The main decision is whether you're keeping the car long, as I bet many who have read the advice have said "bugger it, I won't have the car if the engine does lunch itself" or whether you want to risk based on forum knowledge. Certainly on this platform it's too new to know if it's an issue or not

 

As for evidence, I've not seen any directly to suggest it is detrimental, but as above it could take a long time to surface.

[Sideways? 33]

I believe this concern is a hangover from the Subaru impreza engines, this apparently caused trouble with crank position sensor because of the vibration which lead to trouble with the bearings... So far our little rockets don't seem to have the same trouble, since it is a new engine rather than a re-hash of the impreza engine... Having said that, Knightryder is right that the engines are still a little new for this problem to have reared its head "over time"...

[Mark@Abbey M/S 235]

My take on this , manufacturer are always looking at saving costs nowadays so if they didn't need to add a damper that helped the harmonics they wouldn't;

 

We have built a couple of FA20 motors both where balanced prior to being built both come back with some work on the front pulley to get the balance spot on.

 

Personally I wouldn't remove the stock damped front pulley. The light weight propshaft/flywheel will make the motor respond quicker, but this also makes the motor drop it revs quicker as there isn't as much inertia in the rotating items.

 

Pro and cons like a lot of things on cars/engines. 

[Keethos 842]

Continuing with what Mark just said, revs do drop quicker so I found that I had to adjust my timing of toe heeling on normal roads (rather than balls out on track). What I have also read though that with all these light weight internals, you are more susceptible to idling problems, if true, I'm sure you could map that out.

[Galaxian 6]

thanks for all the replies.  though I am still unaware of the maths for this, and I have also tried researching it to no avail, I think I will give this mod a miss - there are just too many unknowns for me. 

 

so, I'll stick to what I know, the more simple things I understand.  it's been an interesting learning curve though! 

 

 

[Keethos 842]

Yeah....sorry about the rambling there

[Kodename47 446]

BTTT

Just seen this: Fluidampr Internally Balanced Damper

They have released some data vs stock and lightweight crank pulley:

[Church 209]

Lightweight pulleys by themselves are not giving enough gains to be noticed by "butt-dyno". But if one goes all the way also installing LW driveshaft, LW wheels, lighter aftermarket brakes, worth changing them too. All of that improves actual acceleration in measurable way, and can be worth doing to squeeze out most performance from underpowered NA car.

But just like with doing exhaust upgrades, i'd probably would leave them stock, if i had gone forced induction way. Even milder FI upgrades in SC or Turbo way give more then enough missing power for these relatively light cars to better spend that money elsewhere, for example on more seat time on track

As advise to lighten just LW crunk pulley OR LW flywheel came from tuner that rebuilt / overhauled several FA20 & EJ engines, i'd prefer to trust his warning. Yes, boxer engines need less vibration/harmonics dampening among different engines, yes, manufacturers prefer playing on safe side and reusing parts bin, but if in real life mechanics seen issues with subaru engines with both crank pulley and flywheel lightened, i also will choose to play safer for car that i wish to run for at least 150K km.

[Keethos 842]

What exactly is that saying Steve? I've got the GFB light weight pulleys and after having all the pulleys put on (initially only ran with the 2 smaller ones cos couldn't get the crank one off) I have noticed a difference in how quickly the car picks up / how eager the car is with these light weight pulleys...can I expect issues to arise because of it or only if I go lightweight flywheel too?

[Sideways? 33]

The graphs are showing that lightweight pulleys lose power at the top end due to a significant spike in vibration... However, which pulley did they test, and what was the stock pulley like vibration wise is not shown here - probably could look up the original source and find out though... What the first graph is intended to show is that there is a difference between the one they're selling and a lightweight pulley - however, they have only shown one order of vibration which has a large difference, and of course on the internet, that spike means ENGINE DESTRUCTION!

[Kodename47 446]

What exactly is that saying Steve? I've got the GFB light weight pulleys and after having all the pulleys put on (initially only ran with the 2 smaller ones cos couldn't get the crank one off) I have noticed a difference in how quickly the car picks up / how eager the car is with these light weight pulleys...can I expect issues to arise because of it or only if I go lightweight flywheel too?

The top one shows the difference in vibrations, it's a shame the stock one isn't included however I assume it's the same or better than the Fluidampr one.

The bottom is actually a dyno pull, surprisingly showing that the lightweight one makes less power.

Those are actually FA20 based charts too, not generic.

[Sonic 4]

the vibration angle graph is a scary one as a 6th order vibration ( meaning it occurs 6 times in 1 revolution)  so the crank is torsionally vibrating +/ -0.25 degrees 6 times a rev at 6000 rpm...

 

 

thats quite enough to buzz the nose of the crank off over time

 

Still think a lightweight / undamped pulley a good idea......?

[Keethos 842]

That's the thing, I have no idea, some people say it's ok some say it isn't. Can issues occur with just the lightweight pulleys and no lightweight flywheel and if so, what issues can I expect?

[Lauren 2259]

I've got tbh, I wouldn't touch a light weight undamped pulley with a barge pole. That the stock pulley has a harmonic damper means it is there for a reason. 

[Sonic 4]

Do the people who say a LW undamped pulley is OK , happen to sell them? Or perhaps own a set already?

 

torsional vibraiton is a complex scary subject that can destroy an engine - its interesting to note that the last generation of Formula 1 V8's tended to have a fluid crank damper, fluid cam dampers, flexible drive quills in the front of each exhaust cam, flexible 'compound' gears to sit between the cams and crank and the auxilaries also driven by flexible drive quills ( shafts)

 

this was mainly down to the engines having a very large rev range (3000 to 18,000rpm) and very big cam profiles so producing high levels of 'stab' torque into each engine revolution

 

more mundane engines still suffer from these issues just not as much - but then they do run for 150K Km instead of 3K Km

 

so to throw away the only damping element on the engine a bit daft in my book

[Church 209]

Keethos: from what i know, many people had used LW pulleys on subaru boxer engines, both used for long time/distances daily usage and for track racing without much issues. Same for LW FW. But in case of using both for some there were shot bearings in engine sometimes even as soon as after 2K miles. Though maybe some had better luck, i don't want to risk my daily driver car, if there are many other safe for sure upgrades to install that will net more performance per buck.

P.S.

BTW, if max NA performance matters, imho one should consider installing different ratio Final Drive. Yes, economy and top speed will suffer, but on track it's wonderful companion if staying NA.

[JamesP1991 222]

Hmmm interesting. I have already a lightweight flywheel fitted and a shorter FD sat in my room waiting to go on. I spoke to Adrian when I was at Fensport and he told me that there were many pre conceptions being made about how aftermarket pulleys were bad for the engines. He categorically told me that a lightweight pulley kit combined with a lightweight flywheel should do no long term damage to the car. Even on his turbo build he has combined both of them with a lightweight prop too and has found no issues whatsoever so far, and that car is being pushed to the limit.

On his advice I have bought a lightweight pulley kit to compliment both the FD and the flywheel I have, and I am more than happy to play guinea pig for everyone. It seems a lot of the people who had trouble with their pulley kits in the states were down to them not correctly pitting the kit on in the first place. We know that bullshit spreads like wildfire on that forum and there are plenty too that have had no issues whatsoever.

I trust Adrian to offer me the best advice for my car, and if he says its 100% fine to combine both then I am willing to bite the bullet.. Which I have!

I also didn't think dampening was as important on a boxer engine compared with a standard 4 banger?

[Lauren 2259]

The point you have to remember is that the stock crank pulley would not have a harmonic damper if it did not need it.

 

You take your chances, your engine etc. 

 

Until you've done a decent amount of mileage with a lightweight pulley it is difficult to tell if it's an issue. Low mileage race cars don't really give you that info. 

 

I must admit, I see no appeal in being a guinea pig.

[Kodename47 446]

These went up last night, thus showing a more full picture:

Stock

Lightweight

Fluidampr

Full dyno from lower RPM:

[Sideways? 33]

I need to get my books out, but those graphs seem to be telling me that the fluidampr is not as good at damping vibration as the stock damper, and the lightweight pulley does a great job, apart from in the 6th order vibration... In short, if lightweight pulleys were a creation of the devil, many more people would have problems with them - although, these graphs do show that there is a significant difference in behaviour between stock, damped, and undamped, and therefore definite potential for something to happen...

[Kodename47 446]

Here's more info from the development:

Stock: The first crankshaft resonance appeared at 88Hz and was almost below the testing rpm range. A second crankshaft resonance was also seen near 260 Hz.

Lightweight: The lightweight pulley shifted a third crankshaft resonance into the operating range at 600Hz. The 600Hz resonance excited 5.5th and 6th order vibrations. High frequency amplitudes carry much more stress than equivalent low frequency amplitudes because they occur more times per revolution. Crankshaft driven timing components and oil pump drives can be more susceptible to high frequency vibrations.

Fluidampr: The Fluidampr performance damper effectively reduced all vibration amplitudes to less than 0.25 degrees peak across the testing range. Amplitudes also show a general reduction trend while approaching the upper limit of the rpm range.

More info here with a pdf of development and testing where the info has come from: http://www.ft86club.com/forums/showthread.php?t=89734