I will post up once people are able to order!
Thanks! It truly is a win win situation. You are doing preventative maintenance AND adding performance at the same time.
I am not super familiar with lightweight crank pulleys. How much power could you realistically expect from one?
There’s some estimates out there for 1.5hp per lb dropped (reduced parasitic drag). idk if its necessarily something you can measure on a dyno, in normally just makes the engine more responsive/rev happy. You’ll also see under drive pulleys (spins the accessories slower) but with the blower thats a more involved option beyond the concerns of under driving the alternator.
So what about negatives regarding LW crank pulleys? I’ve heard these reduce torsional damping, which is needed to attenuate higher order harmonics from the crank, especially with an inherently unbalanced engine like ours.
Not trying to drive the discussion in a negative direction, just interested about the technical discussion. Maybe there are some good threads here? If you search the web on this subject, you can probably find plenty of information to support either stance.
But we do know now that the factory crank pulley can fail relatively early on, so it is a welcome choice to have aftermarket solutions. Wasn’t there already another LW crank pulley made for our engine? I’ve seen it discussed on AZ, where people were pretty negative. It might have also been a larger radius.
Generally speaking, the front pulleys are heavy OEM because they are acting like a small flywheel- dampening torsional vibrations like you said. It stands to reason that if BMW and Audi among others have stated they use aluminum fasteners on the engine to save weight, they wouldn’t have put a 5lb mass on the crank snout if they could have put a 2lb aluminum one. It’s there because they think it’s necessary. How bad is it if it’s not there? I dunno but as you said I’m sure there’s engineering docs on it somewhere.
If I were racing a car it’s probably a great idea to go with a solid pulley if the OEM one is known to come apart. But for a street car I think there’s no real need for it.
On the “it makes HP” front, it’s easy enough to calculate using formulas how much power you’d get from a lighter crank pulley. It’s an inertia calculation so it’s HP freed up based on how fast the engine is accelerating, therefore gear dependent with the greatest amount in the lowest gear.
There are some decent calculators out there which can cover the basic simplified calcs to give you and idea of the ballpark HP you could gain by swapping to lighter pulley damper or brake rotors etc.
- http://www.w8ji.com/rotating_mass_acceleration.htm (good basic explanation of HP stored/gained etc from different rotating masses)
- calculator used in the above URL: http://www.botlanta.org/converters/dale-calc/flywheel.html
- http://hpwizard.com/rotational-inertia.html good one for calculating gains from lighter brake rotors in particular (equivalent mass is about 1.2x static mass for a typical brake rotor)
Looking at the data for a 5-7lb and 7 diameter inch (guess) pulley damper, it looks like the gains are going to be pretty small using the links in #1 and #2 as Hp/sec is less than 1 to begin with. Just not enough mass and too close to axis of rotation for it to amount to much.
No offense, but this is a poor argument. I noticed your car is stock, so that makes some sense. Here’s why.
Audi also puts a restrictive set of cats on your car, as well as a restrictive intake. Does that mean those can’t be improved? Hell look at the 1320 supercharger…it is not being used anywhere near its capabilities. People replace their blower pulley and ECU tune all the time in the pursuit of performance and don’t say ‘oh well Audi must have done this for a reason, so we shouldn’t change it’. Audi makes the stock exhaust super quiet on all of their cars. Some like it a bit louder…but Audi’s market isn’t the 2nd and 3rd buyers of these cars. They’re the people who pay $100,000 or $80,000…the first buyer. Those people usually like it quiet as a church mouse.
Reality is that Audi isn’t after 100% maxed out performance on all of these cars. Especially the entry level sedan’s midrange option (S4). Perhaps Audi recognizes that they need to maintain a delta between the S4 3.0T and the RS4 4.2 FSI thus they hold back in a number of areas.
Another factor is that a lump of steel is far cheaper than a balanced aluminium piece. On the aluminium vs. steel debate, my RS4 has aluminium fenders, aluminium hood, aluminium trunk. The S4 has none of that. Does that mean that the steel parts on the S4 were made in steel for a reason, and that it must be better? Or does it mean that Audi just frankly doesn’t give the S4 all of the toys. Going further, the R8 has an aluminium frame, whereas my RS4’s is heavy steel. Which one is ‘right’? Or is right not the answer…budget, power delta and model positioning being the main factors driving these decisions.
On my B7 S4 I had a JHM lightweight crank pulley. It stands to reason that taking 5.5 lbs of rotating mass off at the crank will help the engine rev, and if the stock part is shit, why the heck wouldn’t you do this instead of replacing it with the steel lump that is apparently prone to failure (that’s shocking in itself)
[quote]There are some decent calculators out there which can cover the basic simplified calcs to give you and idea of the ballpark HP you could gain by swapping to lighter pulley damper or brake rotors etc.
- http://www.w8ji.com/rotating_mass_acceleration.htm (good basic explanation of HP stored/gained etc from different rotating masses)
- calculator used in the above URL: http://www.botlanta.org/converters/dale-calc/flywheel.html
- http://hpwizard.com/rotational-inertia.html good one for calculating gains from lighter brake rotors in particular (equivalent mass is about 1.2x static mass for a typical brake rotor)
Looking at the data for a 5-7lb and 7 diameter inch (guess) pulley damper, it looks like the gains are going to be pretty small using the links in #1 and #2 as Hp/sec is less than 1 to begin with. Just not enough mass and too close to axis of rotation for it to amount to much.
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Calculators are fun. Reality is that feeling your engine rev freer is more compelling. A LWFW and crank pulley in combination really feel fantastic and while putting an hp number on it is impossible (we’re talking about reducing loss, not making gains) it is one of those things like LW brake rotors that people say doesn’t help when they use a calculator (even though the cars accelerate faster with them).
Jake - how much for the crank pulley?
there was a bigger pulley to generate boost accompanied with a tune. It was from some little shop that refused to show performance of any sort. Usually a bad sign lol.
Are you guys serious that the stock pulley is ‘failing’? Any specifics other than the OP?
LW pulleys by JHM have been in place for 7 years on S4s/RS4s. Great little ‘every little bit helps’ mod.
If you think the resistance to LWCP from posts like yours above or boosteasy’s are bad, you should have seen them on the B67 S4. It was a nightmare to produce for JHM because the engine was externally balanced and the manufacturing of the pulley to maintain that balance was delicate to say the least. Everyone said that it was impossible to improve on the Audi design. Well, after selling hundreds of them for a number of years and flawless results, I’d say JHM silenced those doubts. Another company created an aluminium crank pulley for the B67 S4 (ironically the same one referenced above for the larger B8 crank pulley) that was not factoring in the BHF engine being externally balanced, and they made a name for themselves destroying engines as a result. That’s one of the reasons so many of us were vocal against that company when they made another foray into the crank pulley business lol.
it’s not for sale based on his post where he says this is a sneak preview of a product in development, however they’re usually 250-350. Not sure what goes into this one.
The 3.0T is a pretty poorly balanced engine from my experience. Lots of posts on AZ going “wtf is wrong with my idle”. You really feel the NVH when coming to a stop at a stop light, likely not helped by the factory motor mounts, which we have seen fail pretty regularly at low mileage. 034 has an upgrade available, but I haven’t heard much feedback and that discussion is probably for another thread.
With regards to the stock crank pulley failing, it also happened to infinkc along with the OP. Not a huge sample, but enough to raise an eyebrow.
that’s standard V6 fare, the rough idle.
Funky design I guess.
If you read through the post, the OPs failed, there has been another documented instance on vendorzine, and mine. People also said in the post their friends also failed the same manner, but was not posted. All failed in the same fashion around the same mileage.
Side question, would taking 5lbs off the pulley equate to the same as if you were taking 5 lbs off a flywheel? seems logical as both are connected directly to the crank.
Pricing hasn’t been set yet, but will be soon.
One of the biggest reasons for all the rubber and weight (on an internally balanced engine) , is because of of the NVH.
Audi wants to have a comfortable ride, and a majority of the people buying an Audi want to feel like they are driving a cloud.
People like all of us on the other hand will make the very very small sacrifice of added NVH (I couldn’t tell the difference in NVH when adding the LWCP to my car) for the added performance. Additionally in this case, the preventative maintenance aspect as well.
People add lightweight flywheels to their cars all the time. That’s attached to the other side of the crank and you don’t see LWFWs causing engine damage ;D
Calculators are fun. Reality is that feeling your engine rev freer is more compelling. A LWFW and crank pulley in combination really feel fantastic and while putting an hp number on it is impossible (we’re talking about reducing loss, not making gains) it is one of those things like LW brake rotors that people say doesn’t help when they use a calculator (even though the cars accelerate faster with them).
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Wow Saki. The gloves really come off when I comment about a product from your fav vendor.
Re HP I’m not going to argue newtonian physics with you- its record is pretty well established. Dyno tests for similar LW dampers on other platforms are out there as well and they showed what the value was.
Re Alum vs “a lump of steel” being cheaper from the OEM standpoint- I highly doubt that. If you read the original post, you’d know the OEM pulley and damper are a two piece design with a rubber column (prob vulcanized) joining them. There’s zero chance that’s cheaper than what would certainly be a cast aluminum damper/collar if VAG thought the steel/rubber damper was unnecessary for torsional damping.
gloves off? huh? how about addressing what I wrote?
who mentioned HP? and newtonian phsyics?
I get that you’re not happy that someone pointed out your hysterically bad argument but why not engage and address what I wrote?
Why is it that so often when an engineer thinks he’s right, he blindly thinks so without engaging…and he throws his textbooks around the room when people point out huge weaknesses in his argument. It’s amazing.
" I’m not going to argue newtonian physics with you"
Good…because at no point did I discuss hp.
Basically the crux of your post was
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if Audi didn’t do it, it must not be worth doing - I showed you that this is a terrible argument, as Audi do things for a multitude of reasons, namely money, comfort, model hierarchy protection etc. I also showed you half a dozen other areas in your car where Audi didn’t do the best they could, again for those reasons outlined.
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it’s too small of a benefit to be worth doing - again, I showed you that calculators are fun, however real world acceleration and driving feel show that reducing rotating mass in these cars helps, and then you pair a LWCP with a LWFW for example, it really changes the character of the car. While we’re not going to see it on a dyno graph, taking care of these ‘every little bit’ items is a good strategy to produce a totality of effect. i.e. if we replace the UNSPRUNG 50lb hood on your car with an aluminium one that weighs 24 lbs…you won’t really notice it, and your calculator will tell you not to bother. If we then do the same with every body panel…and the trunk…suddenly we’re seeing a result and the car benefits. But 1 on its own doesn’t really move the needle…does that mean you shouldn’t do any of them?
But instead you chucked your toys out of your pram in protest and addressed none of it, other than misinterpreting something I wrote and implying I was talking about hp? Then you really showed your weakness when you tried to dismiss my post as it was only because of my fondness for JHM. Reality is it was my fondness for this being a discussion forum and when someone gives what I think is crap advice, I will address it. Easy.
Deja vu…
LWCP was a new product for the STi about 10 years ago. The OEM pulley was a heavy, internally dampened unit that had significant engineering, and precision assembly.
The technical forum discussion went wild… 30+ pages of arguments. Replacing God’s own crank pulley with an inferior LW aftermarket pulley was heresy.
Guess what? Bullshit. It was there for NVH, and (for the STi) possibly to help new car buyers drive a stick shift.
10 years and tens of thousands of pullies later… the only detrimental issue is a bunch of bruised keyboard jockey egos.
This pulley is now available!
http://www.audizine.com/forum/showthread.php/657537-NEW-JHM-HD-Lightweight-Crank-Pulley-for-3-0T-FSI-V6-IN-STOCK
Ordered mine yesterday. Probably just have Audi do it when I take it in for my Audi care 45k service.
We appreciate the order!
This LWCP is an arguement Jake and I have all the time. We agree on most things but not this one.
Everything that I have ever read about the front crank pulley(harmonic damper) shows that its not worth the removal. Basically there is a very good reason why Audi decided to not just bolt a piece of steel to the front of the engine.
Mr. Dinan explains it quite well :
http://www.atiracing.com/products/dampers/damper_dinan.htm
Will you gain some speed from a lwcp? Perhaps, marginally. But is it worth the added stress on your engine? Not for me. being .0001s faster isn’t worth the money or the engine stress that a LWCP causes.
now on the 3.0t where you have a pulley failure, I could see some guys swapping over to it, but realistically, you just need to keep tabs on it. Every oil change get in there, slack the belt and feel for play in the pulley, if its getting loose, just replace it.
Every engine has its failure points, the 3.0t is no different, but I would most likely still replace it with an OEM unit.