Under Drive Pulleys

w1phil

Member
 Teddington, Middix
Hi All,

i've nearly owned my Z4MR for a year now and I am starting to get the mod bug. i've already done pads and hoses, shim kit, intravee, retro fit cruise and stereo upgrade (mine came with the bog standard 6 speaker set up) and now i am looking at what else is available.

i've been through all of the intake posts and am leaning towards an afe intake and rpi scoop. i'm not really looking for power gains on the afe (more the inductiuon noise) and the RPI scoop is cheap enough that as long as it has no detrimnetal effect i'm game for trying it.

however i haven't been able to find anything on the forum regarding Under Drive Pulleys. The concept (lifted direct from the TMS website) is pretty simple and seems to make sense "Specifically, we have designed them to underdrive the water pump, and power steering pump. Adding these is like getting FREE HORSEPOWER. There are no downsides and underdriving both of these accessories has been proven safe through years of on and off-track use. We do not believe it is safe to change the crankshaft pulley due to the potential harm to the crankshaft. These kits provide a 10%-20% overall reduction in driving your car's systems and have been dyno-tested with a gain of up to 11hp." the product can be seen here http://www.turnermotorsport.com/p-3465-mz4-power-pulley-upgrade-kit-z4-m-roadster-coupe.aspx

normally i am hugely sceptical of tuner claims in relaiton to any HP increases but i've used Turner Motorsport lots in the past and they have a great reputation so i would be really surprised if they would sulley that reputation with unfounded claim. obviously its caveated to the eyeballs with the words "up to" but wondered what thoughts you all have and does anyone have any experience of this type of mod?

cheers
 
I've done it in the past on my Corrado VR6 (about 5bhp gain) and Polo G40 (25bhp gain) - but the Polo got a smaller supercharger pulley at the same time. It's just a different method of releasing a few ponies - i.e. rather than increasing engine output it's reducing parasitic losses.

However, if they've got all these years of experience/proof then where is the actual gain for a 2006+ Z4M? Why only show an old figure/dyno chart for a 17 year old M3?

If you are not using super-unleaded all the time then that will make a bigger difference.

BTW, if you've still got BMW Insured Warranty then be careful that any claims can't be apportioned to any mods you make (so if your alternator, water pump, or an under-driven item fails you may find you're not covered).
 
Thanks mmm-five

My warranty is due to expire in June and I can't decided whether to renew. It cost me a grand last year but Ive had a new sat nave screen, new hood and new roof motor this year plus wheel caps so thinking the cars bullet proof now (famous last words...)

It's getting less use as I've stopped driving to work so thinking of garaging and keeping as a weekend toy and occasional track weapon...what to do...

With my old zed as soon as I lapsed the warranty the drivers window regulator went and heated seat...

Think I will but the bullet and give it a whirl along with the rpi scoop and afe CAI
 
srhutch said:
Did you do the cruise control yourself or did a Indi fit it for you?

Had a local Indy fit it for me. He based in Byfleet Surrey. Let me know if you want the details. I've used him for my lat three fours cars and always very happy with the work done
 
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