ERAUMAZDA

Many people have many views on under driving pullies and I just wanted to know is it ok and is it, well necessary.

I have talk to a lot of rotary guys and they are saying don't do it...it ill underdrive the water pump and you will drive hot.

1. Does it really underdrive the water pump so much that it will over heat. Can't buy and upgrade radiator defeat this problem and doesn't the fan run at just about idle anyway.

2. Under driving the alternator. What if you had an FD upgrade alternator with combination capacitor. Would under driving be so bad.

I just want to know whats up because possibly I am getting advice from people how must put on under drive pullies and do not upgrade whats beging underdrived.

mazdaspeed7

First off, Ill go ahead and tell you dont get both the main and alt UD pulleys. I had both(RB), and sold them recently.

I never had any problems with cooling, and I had a permacool 14" e fan. I DID have some serious charging problems though. With my lights and fan on, my votlage would drop to around 13V. With the wipers on, it would drop to 12V. I burned out a voltage regulator, and I believe it was from the car drying to draw too much power from the alternator.

It did seem to make my car rev a little faster, but now I have the atkins serpentine set(stock size pulleys), and my car idles better, and I see 14V at idle, with my lights and fan on.

All in all, the very minor gains arent worth the price, let alone the problems.

Aaron Cake

iTrader: (1)

If you are experiencing cavitation problems in the water pump due to constant high RPM use, then get a set of underdrive pullies. If you aren't, or are looking for some kind of performance boost, then don't.

Ryde _Or_Die

What about getting an FD alternator and underdrive pullies? I wouldn't think you would have any problems, and would rev quicker. I plan on trying them anyways, later down the road when I don't have anything left to try.

s5spd

Mazda Racing claims their pulleys were good for over 14whp and 10lb/ft-lb. I can't believe it myself but they're all sold out now:
pulley dyno

Ryde _Or_Die

Thats pretty impressive, don't most underdrive companies claim more HP gains from turbo cars?

rx7freddie

what if someone just used the main under drive pulley ?

fastrotaries

Personally i have both from RP and NEVER had Electrical issues, and or overheating. I ran an E-fan Spal 16", Jacob's Box, 85W bulbs.

My friends have even added small systems to theirs and not have had problems. It's been 3 year and counting. Granted we were smart enough to replace our Alt, with good solid new units.

Did idle a tad better, and it's certainly much lighter than the stock unit. Acceleration felt better. I can't speak for all units available, but at least mine haven't given me any probs.

ERAUMAZDA

So don't do it

fastrotaries

It's up to you.

mattrx7N/A

iTrader: (2)

I run the Mazdaracing.com eliminator system (kit came with both main and alt pulley). I have a new stock radiator and some type of ford electric fan and my car runs at 180 all day without using the fan. I've never had any voltage issues even when i run my fan and lights (i dont have wipers or a/c) so not sure if that would draw enough amps to cause a problem.

Ezekiel702

How would the install be on that mazdaracing.com pullys?

fastrotaries

The RP pulleys really don't underdrive all that much, they make most of their power from the fact that they far lighter than the stock units

carx7

iTrader: (31)

Personally I don't belive an underdrive pully will gain HP like that...

PLUS, given the fact that mazdaracing.com ripped me off for $1400 a few years ago and after 6months of arguing they gave me $1000 back for an engine that NEVER showed up, I don't belive ANYTHING they say. Bunch of liars they are.

The underdrive thing is probably personal preference. I'm selling my RP one if you want one.

NZConvertible

No it wouldn't. The faster you turn an alternator, the more electrical power it makes and the more engine power it uses. So if you slow them down they make less electrical power but use less engine power.

A higher capacity alternator takes more engine power to turn (you don't get nothing for free), so if you slowed it down with pullies it would use less engine power than it normally would, but it would also make less electrical power than it's rated at, and you end up right back where you started, except for being poorer.

Ryde _Or_Die

Less power than its rated at, but more than an FC is rated at correct?

bingoboy

wow that sounds like total BS....

NZConvertible

Depends on the pullies. 20% underdrive pullies would turn a 100A FD alternator into an 80A one, so you might as well have saved yourself a bunch of money and time and just fitted an 80A S5 alternator.

ERAUMAZDA

yeah but if you get a 80A alternator you would then run at 60A

JGard18

I had one on my Impreza. Totally not worth it. I never saw a performance gain, and at idle, my lights would dim a lot.

So yeah, personally, I don't think pulleys are worth it at all.

jetfire76

i STILL have my unorthodox underdrive pulley in my RS. but i agree w/ JGard...totally worthless. no HP gain that i can tell...maybe 1 HP? if i wasnt so damn lazy, i woulda taken it out and sold it already.

-jet-

ERAUMAZDA

So far the only advantage is underdriving the water pump...(well, if you have pump cavitation.) Thanks a lot guys you were very helpful. I think its more logic to find horsepower else were. I am just looking to find horsepower gain by reducing load instead increasing power. I just perfer making up lost power than trying to over come engine/driveline friction by adding more fuel and more air, thanks.

JGard18

if you want more from less...lighter flywheel would be more effective.

carx7

iTrader: (31)

JGard18 has it. I have an Al flywheel on my car... huge difference, and very driveable

mazdaspeed7

Do you like redlining 4th gear a lot? If not, you probably wont ever even see a change in temp from water pump cavitation.