mx5cartalk.com

Am getting into the build of my engine. In doing so, I have inspected the pulleys, and most of them are in bad shape, dinged, chipped etc.

Is there any benefit in after market pulleys, or underdriving? And conversely, any \"cost\" in terms of reliability etc. I did see another thread where under driving the main (crank)was universely frowned upon.
http://www.aus-cartalk.com/viewtopic.ph ... ght=pulley

I dont mind paying if there is something to gain. Conversely, I have access to a lathe if just making them up in aluminium is a benefit.

Underdriving the crank without the proper vibration damper induces vibration into the oil pump which is believed to lead to premature failures. GFB were interested in making pulleys but there was not enough interest in this community. Unless you are reving past 8000 consistently, I personally have not seen a use for them on a BP engine. In that case, only changing the accessory pulleys would be advised.

You were the one trying to set up a group-buy on underdrive/lightweight pulleys right CT?
Have you since gotten them for yourself?
I am interested in knowing if they really work or not as they are a fairly new \"fad\"

\"fairly new fad\" - are you kidding?

They're dyno proven to give a very minor power gain.

There are few if any known failures due to the removal of the harmonic damper on atmo MX-5s.

Turbo MXs are a different story. Turbo + UD pulley = engine go boom boom. It's all due to the amplitude of vibration, which is proportional to your torque output.

The crankshaft pulley has the harmonic balancer built in. What CT said about the oil pump gears if it's stuffed or you're putting a huge amount of power through. Replacement options are OEM Mazda for $240 or an ATI one from the states for about $US550.

Matty wrote:"fairly new fad" - are you kidding?

Well .... I'm sure it's been used in racing for decades, but I've only seen them available to the public and advertised in mags over the last few years.

so, no concensus is....

leave the crank pulley alone, but underdrive the others perhaps?

Yep, GFB approached me after seeing my car on the dyno - I said yes for the alternator and the power steering but needed 10-20 sets to be ordered before they would commit. I wasn't all that interested - rather spend money on thinks that would actually be a benefit!

CT wrote:Yep, GFB approached me after seeing my car on the dyno - I said yes for the alternator and the power steering but needed 10-20 sets to be ordered before they would commit. I wasn't all that interested - rather spend money on thinks that would actually be a benefit!

Hey that's cool for a manufacturer to approach a private person wanting to make something for them AND the type of car they owned.
I bet you missed out on some sponsorship deal too hey?

I wouldn't have mind trying it out, but the cost to benefit ratio is way out of kilter, plus the fact that there would be issues with tensioners and/or different size belts.

so, getting back on topic....a new set of OEMs all round then?