Any Feed back on the JHM light weight crank pulley?

[overboostts]

Just wondering has any feedback on the JHM light weight crank pulley. Seems like its common with the S4 boys on the Zine.

"bank pulley" edited! damn ipad spell check!

[Teutonic Tuner]

Welcome first of all!

This isn't listed for the RS4 on their website just the S4 and haven't heard any talk of it being fitted. I would contact Dru at JHM and ask him if it fits/works, but I doubt it otherwise they would list them for the RS4 on their site.

[sonny]

Welcome

"S4 boys on the Zine" sounds like a boy band. any good?

As above, however im sure a company did list them. Think TTS did one as part of its TTS S/C kit. I could be wrong.

[HYFR]

FIXED

Welcome

"S4 boys on the Zine" sounds like a gay band. any good?

[overboostts]

Actually, JHM did respond to me sometime back, and confirmed there is a LW pulley for the rs4. I will be getting it soon. Will do a short review after!

[Teutonic Tuner]

Sneaky, you may become the first RS4 owner ‘anywhere’ to have one of these fitted due to JHMs under selling! Let us know how you get on how easy it is to fit.

I fitted under drive pulleys to my E46 M3 and it freed-up the engine nicely allowing the engine to rev freer and added a nice weight to the steering. Simple but effective.

Is this the item: http://jhmotorsports.com/shop/catalog/j ... a7cad37640

[stu]

Can anyone explain the downsides to installing a lightweight crank pulley?

I ask because:
(a) I didn't know such a think existed until five minutes ago; and
(b) Surely during engine R&D, Audi designed the original one to particular specs for a reason.

[Teutonic Tuner]

Stu, possible downside I would expect is less refined driving experience ie if you're not gentle when coming off the throttle with lightened parts the engine won’t settle down as smoothly and be jerkier, same reason a weighted flywheel is used, it's all to aid smooth driving. Removing rotating masses sharpens throttle response and releases HP. Manufacturers will always err on the side of refinement.

[adsgreen]

The main disadvantage I see of any lightweight component on the engine is balance.
For a big v8 8.5 k rpm is a lot and balance is very important. I've always had engines balanced as a whole system.

Changing one component at one end may cause issues with overall balance.

[stu]

[ArthurPE]

Can anyone explain the downsides to installing a lightweight crank pulley?

I ask because:
(a) I didn't know such a think existed until five minutes ago; and
(b) Surely during engine R&D, Audi designed the original one to particular specs for a reason.

upset the balance of the engine

a good, forget about it, lol
b yes, if it could be lighter, it would be

the rotational mass is so small (as is the radius) it is moot compared to clutch, pumps, rotating assembly (piston/rod/crank), etc.
don't screw around with this engine, it is a jewel

why do all these shade-tree engineers (not you, the guys who can improve on every part Audi made) think they can out think a dozen phd's with hundreds of years experience?

[ArthurPE]

The main disadvantage I see of any lightweight component on the engine is balance.
For a big v8 8.5 k rpm is a lot and balance is very important. I've always had engines balanced as a whole system.

Changing one component at one end may cause issues with overall balance.

yep, both axially and radially, harmonics are a strange phenomenon, doesn't take much to cause them

[adsgreen]

I do think improvements are there to be made.
Need to remember that whilst Audi engineers may be excellent they are restrained by the commercial realities of business.

But yes... And crank pulley is a bit small fry.

[sakimano]

upset the balance of the engine

a good, forget about it, lol
b yes, if it could be lighter, it would be

the rotational mass is so small (as is the radius) it is moot compared to clutch, pumps, rotating assembly (piston/rod/crank), etc.
don't screw around with this engine, it is a jewel

why do all these shade-tree engineers (not you, the guys who can improve on every part Audi made) think they can out think a dozen phd's with hundreds of years experience?

arthur do you not know JHM's team? One of the members is one of those OEM engineers who you worship in your posts. He works at the performance division of Ford (SVT) and is able to help JHM with product development.

To say they are 'shade tree' is a ridiculous comment. I'd like to see you say that about MRC while you're at it...you'll be banned in all likelihood. Further, to say things like 'if it could be lighter/faster/better it would have been' and to say that JHM is 'out-thinking' Audi is missing a very important fact - Audi is constrained by budget, emissions, noise regulations, mass affluent general public need for a cushy car etc. They could have made the RS4 500 hp at the crank from the factory. They choose not to. They weren't out-thought by JHM. JHM just offered what Audi chose not to give us.

Your statement that if it could have been lighter it would, would imply that the car couldn't be improved upon from the factory. Ever bought 2 lbs of aluminium vs. 6lbs of steel? Guess what...aluminium is bloody expensive, especially when you're buying 20,000 lbs of aluminium vs. 60,000 lbs of steel. Want to talk about the 26 lb stock steel flywheel vs. the JHM 13lb lightweight flywheel? Again...'if it could be lighter it would'. Well...Audi chose to buy 260,000 lbs of steel for the flywheels rather than 130,000 lbs of aluminium.

Further, on performance, If Audi gave us all they could, why didn't they run the dual intake setup the RS5 and B8 RS4 got (and that they had already developed for the S6/S8 before the RS4, as shown below)? Why didn't they run 2.75" exhaust as JHM and MTM (MTM stands for Motoren Technik Mayer, started by someone you'd call a shadetree engineer...when in fact Roland Mayer was a long time Audi engineer). Why didn't they run forged wheels? Why didn't they run ceramic brake rotors as standard? And the tune that helped them develop an extra 30 hp at the crank on the newer cars from a similar engine with a dual clutch DSG and launch control in the tune? You really think Audi gave us everything possible, and that they can't improve upon the B7 RS4 engine as it was from the factory?

Not only could they have improved it...they did in the next gen. The new car is faster even though it's much larger and heavier. So what happened? Maybe...just maybe...Audi left a bunch of power/performance on the table with the B7 RS4 as they always do, knowing they would re-use this type of engine (NA 4.2 V8 FSI) on two more RS platforms that they'd need to sell from 2012 to 2014.

[sakimano]

The main disadvantage I see of any lightweight component on the engine is balance.
For a big v8 8.5 k rpm is a lot and balance is very important. I've always had engines balanced as a whole system.

Changing one component at one end may cause issues with overall balance.

is the RS4 engine externally balanced? JHM spent a fortune on the B6/7 S4 crank pulley because it was externally balanced. The precision Audi goes to in fitting the stock pulley has to be replicated on the JHM LWCP. It was. I had one on my S4 and it shaved 5.5 lbs of rotating mass at the crank. A pretty significant chunk. They have a connection to Ford SVT and Roush that allowed them to develop the part. Otherwise, the costs would have been WAY out of reach. They still spent a fortune on it.

p.s. another company (ASP) made a B6 S4 supercharger without a properly balanced crank pulley, and kept grenading engines but didn't know why. After 2-3 they quit. A quick look at the pic revealed the answer to just about anyone who knew the car. Odd that they didn't. These are the monkeys that I believe Arthur is referring to. His comments are maybe a bit under-informed with respect to the talent JHM has access to.

here's the ASP supercharger + improperly balanced (not balanced lol) crank with their pulley



Here's the one JHM developed for the B6 S4 and the OEM steel one. Don't you think ASP would go 'oh...<beep>...this is not just a billet aluminium wheel...there's some thought in this OEM part. Should we check if the engine is externally balanced? Naaah....let's just slap this solid one on and hope for the best. Well, unbelievably, that's what they did.

The costs JHM incurred (including calling in favours thanks to their connections) are the reason nobody offers a LW crank pulley for the B6/7 S4. I'm not sure if those same rules apply to the RS4 (I don't think they do).