underdrive pulley or not?

[kyle2blue]

should i get an u/d pulley kit? pros and cons please

[Furious]

get them. there really is no cons to them as long as you dont underdrive the alternator or the crank. they say its safe to underdrive the alternator but i dont think (personally i would take the chance) there are underdrive pullies for the crank as well but once again its a bad idea to do this, especially if you decide to do a lightweight flywheel in the future.


they are a decent mod to do , i will be putting mine in , in the spring

[///M Power]

My buddy has them onhis e36. It's annoying as shit

[SpeedInfusion]

like mark said...no alternator or crank pully's...

[cloaked95]

Originally Posted by ///M Power

My buddy has them onhis e36. It's annoying as shit

Did he say what annoyed him? I was thinking about it too.

[Teh Prof]

Steve Dinan is generally against them. He knows a lot about our cars.

http://dinancars.com/whitepapersFile.asp?ID=5

[vwk]

With a light flighwheel you'll always get unbalance in your crank, eventually causing your crank to break.

[WALSRU]

Good link M3UOND. That was more detailed than anything I've found but it did make me feel pretty good I'd already decided against underdriving. I'm still planning on a fan delete mod though. I would think that should free up just as much without the damage (Ohio isn't that warm anyway). http://www.understeer.com/onlinestore-engine.shtml

[Furious]

that link is pretty much talking about the dangers of underdriving the crank pully, i dont recall anything bad said about underdriving the other accessories.

[vwk]

Any underdriving is bad. Weither it's for your waterpump, dynamo etc.

I can assure you it's bad.

@Walsdru
Don't get your hopes up to high about the fan delete mod.
It's nice to do when your fan clutch is broke, but otherwise please keep the money in your pocket.
Dyno tests I've seen have proven a 1~3bhp gain, so IMO it's not word the effort.

[Furious]

Originally Posted by vince318i

Any underdriving is bad. Weither it's for your waterpump, dynamo etc.

I can assure you it's bad.

@Walsdru
Don't get your hopes up to high about the fan delete mod.
It's nice to do when your fan clutch is broke, but otherwise please keep the money in your pocket.
Dyno tests I've seen have proven a 1~3bhp gain, so IMO it's not word the effort.

thats odd, can you link me to these dyno graphs? or PM me some? im curious as i will be doing it, and friends that have done this mod have seen a gain of around 4-5wrhp (like a hp gain of like 8-9hp)

as for the pullies i dunno, ive yet to read any cautions where someone had damaged the car due to it.. ive talked to bmw about pullies, they obviously dont recommend them , but they do say there is a tolerance that most do follow, because most accesories do use more power than is required,

[vwk]

Originally Posted by Furious

thats odd, can you link me to these dyno graphs? or PM me some? im curious as i will be doing it, and friends that have done this mod have seen a gain of around 4-5wrhp (like a hp gain of like 8-9hp)

as for the pullies i dunno, ive yet to read any cautions where someone had damaged the car due to it.. ive talked to bmw about pullies, they obviously dont recommend them , but they do say there is a tolerance that most do follow, because most accesories do use more power than is required,

I don't have the dynocharts myself, I would like to give them to you to prove it, so you just have to believe me based on the fact that I drive a bimmer

I often visit this guy over here in Holland, he makes his living with car maintainance, mostly BMW. He also races professional with bimmers, makes racecars, build an M3 3.2L engine into a 323ti compact tuned to 350PK, so the guy really knows his deal.

I've asked him what he thinks about the commond mods like fan delete, underdrive pulley's etc. When I said if the fan delete mod really produced 6PK gain, he just laughed. He tested it himself on the Dyno, and showed 1 to 3PK gain.

Ofcourse it's something that makes your car "slower", but why spend that amount of money for so little gain... was his advise.

I've asked him because with my accident the fan got stuck between the engine and the radiator, so my clutch is fucked.
In his opinion this would be the only valid reason for me to do the fan delete mod.

If you want to spend 100~150 dollars for a fan + 99 dollars for the thermostat, waterwetter etc. just to gain 3PK, please do so.. But IMO it's not worth the money.

[cloaked95]

I guess if we all look at HP on a financial matter it should break down to approximately $40.00 per HP. I think this is a pretty close estimate on what we all spend to get the extra umph!!! out of our engines. SO, If anyone has the money to spend just do it. A little HP from the C/A a little from the Chip, a little from the exhaust a little from the fan delete and a little from the underdrive pulley WOW! if I get an average 5 HP for every addition that calculates to Ahhhhhhh?
25 HP I think that a hell of a lot of little HP.
Not I dont want to believe anyone but if there is no documentation its just heresay or someone elses opinion. I myself like to see it on paper.

[Furious]

im gonna be putting my car on the dyno this spring, we will see what my mods will be able to get. im hoping to see around 215-220wrhp but its along shot we will see i guess when everything is done.



as for the fan delete, i guess , much like most mods, it depends on the car, some cars react very well to mods and some do not react to them at all

[vwk]

That I agree with you, but in my case I'd spended the bucks on a OEM M3 GT Class II spoiler and the paint for that. Rather doing that then the risk of gaining 2PK :P

But as far as the underdrive pulleys go: Just don't