Under Drive Pulley's Performance

Bling Bling · Post by **Bling Bling** » November 12th, 2006, 2:23 pm

Looked around a little but wanted to know if the UDP for a 2.5 Litre will fit on a factory 1.8 Litre? Asking because until I do my swap, I want it for my K8.

papa roached · Post by **papa roached** » November 12th, 2006, 3:16 pm

sure will

hgallegos915 · Post by **hgallegos915** » November 12th, 2006, 3:21 pm

Try to get an unorthodox one tho. I got an obx and didnt work for me.

Bling Bling · Post by **Bling Bling** » November 12th, 2006, 7:01 pm

Thanks...Unorthodox it is

JM1EC-V6 · Post by **JM1EC-V6** » November 19th, 2006, 9:26 am

yeah, get an unorthodox, just bought a RR-Racing one and needed modifications to fit (i.d. to small) and the crank sensor trigger holds in place with ridiculous chinese-type screws (tried to remove them and fasten them up with loctite and broke one in the pulley ...)

Bling Bling · Post by **Bling Bling** » November 19th, 2006, 9:44 am

So I have an Unorthodox UDP coming but what I really want to know now is does it ACTUALLY do any good for the performance that YOU have noticed? I know the small HP change wouldn't be too obvious but would like hear about any gains you did notice!

Yoda · Post by **Yoda** » November 19th, 2006, 10:29 am

As far as performace goes it is 2 steps forward and one 1 back kind of deal. If you spend a lot of time in traffic or at idle your alternator isn't turning fast enough to keep the battery charged. In turn the alternator is forced to work harder once the rpms come up to the speed to top up the battery. So you do get a slight increase in power but often you will need to wait a couple minutes of high speed driving before you see the full affect of this mod. To get the maximum benefit I had to get an alternator overdrive pulley to use with the U/D crank pulley. While I was at it I also added an U/D P/S pump pulley.

A couple of things to think about Unorthodox UDP. I have found a thickness issue at the hub of the pulley. I have seen several where they were under spec so no matter how tight the crank bolt is there is still about .002-.003 play. The problem here is that they wobble destroying the whole hub of the pulley. Also Loctite the screw for the crank sensor tigger ring. I've known a couple guys that have ring seperate from the pulley in the middle of the night in minus double digit temps. It seems that someone at Unorthodox didn't consider that steel and alumimum don't contract at the same rate and didn't specify the right type of tap for the screw holes in the aluminum for steel screws.

Bling Bling · Post by **Bling Bling** » November 19th, 2006, 12:01 pm

Where might I find an O/D pulley for the alternator? Or is it a HUGE deal?

Nd4SpdSe · Post by **Nd4SpdSe** » November 19th, 2006, 12:58 pm

wound't getting OD pullies to compensate void the benefits of the UD pully to begin with?

Yoda · Post by **Yoda** » November 19th, 2006, 1:28 pm

Bling Bling wrote:Where might I find an O/D pulley for the alternator? Or is it a HUGE deal?

I went out in the stock room and found a block of aluminum the right size and turned it on a lathe in the old prototype shop in the R&D dept. So as far as I know that are not commercially available for the MX-3 although I am starteing to see them for other new cars.

papa roached · Post by **papa roached** » November 19th, 2006, 1:48 pm

Bling Bling wrote:Where might I find an O/D pulley for the alternator? Or is it a HUGE deal?

had mine on my car without a OD pulley for over a year, never had a start issue

Yoda · Post by **Yoda** » November 19th, 2006, 2:55 pm

Nd4SpdSe wrote:wound't getting OD pullies to compensate void the benefits of the UD pully to begin with?

The OD alternator pulley with the U/D under drive pulley basically cancels each other out so you have a the original drive ratio or maybe just slightly underdriven. Underdriving the alternator does not free up as much power as the P/S or water pumps as people think. The alternator only creates a lot of mechanical loses when it is charging with the UDP the alternator is making less than 12V at idle so you are running off the battery. Also the stock alt. pulley ratios are set up to spin the alt to be most efficent at 3000-3500rpm where the engine will spend most of it time. EFI engine need a lot of juice to run at peak power even more for things like the lights and ICE. If the alternator is not charging 100% the regulator will ask the alternator to try to supply more current increasing the mechanic power load on the engine. Sometimes this load is often greater that the savings of spinning it slower with a UDP and the additional load remains even after the alternator is driven at it optimum speed until the batterey is fully charged. If the battery is old and has lost a cell or developing internal resistance this will also place a load on the alternator so U/D it here is a handcap as well. To a point the faster it spins the less work it will do. Where as the water pump is also optimized for the same 3000-4000rpm to achieve the best cooling but once you pass this speed it is fight back pressure in the cooling system which only increasing the faster the engine revs. The P/S pump is slightly different it has a pressure relief valve that allow it to work over a larger rpm range but is still over pressures at + 6000rpm. Unless it is a pure race car you are better of not U/D the alternator at all. On my SOHC for example I removed the water pump and thermostat completely for a gain of between 10-13hp over the UDP on the water pump itself. There was little difference between on the UDP on the alternater and the stock pulley once the engine was over 4500rpm but there was a big difference on the bottom end where the the stock pulley had a slight advanages the longer the engine sat at idle.

Yoda · Post by **Yoda** » November 19th, 2006, 3:04 pm

papa roached wrote:
Bling Bling wrote:Where might I find an O/D pulley for the alternator? Or is it a HUGE deal?
had mine on my car without a OD pulley for over a year, never had a start issue

You wouldn't have a starting issue the car will start and run as low as 10V The question is would there be any performance benefit and how much with a UDP and I was just saying that underdiving the alternator can change the gains depending of the charging state of the batterey.

mx3autozam · Post by **mx3autozam** » November 19th, 2006, 3:25 pm

I used mine for 5 months. Not a problem charging the alternator or the trigger ring come apart. Mine is the unorthodox one

mazdaspeedmx_3 · Post by **mazdaspeedmx_3** » November 20th, 2006, 12:29 am

get a 110a alt and the problems solved
I have a cosmo racing UDP and have never had any chargin issues but i have the 110A alt...i had to grind that 1/2" ledge on the crank case but mine works great.....i had it off raced my buddy's h22 civic HB and our cars were dead even...went home put it on an i would get a huge jump off the line and he couldn't touch me.... They rudce the weight on the crank shaft lettin it revv up quiker same priciple as a light weight flywheel