What's a under drive pulley?

[blue_ute]

Mine was already tuned before the underdrives and I got it tuned after so 10 kw is not gained by tune alone but this was on a boss 260 engine with full bolt ons and billet oil pump gears which was recommended

[cs123]

Originally Posted by Big Damo

With an alternator, it free spins easily, but when you load it up by turning on more electrical stuff it gets harder to turn.

The alternator is rated at what? 100 amp, So that is 1.2KW at full load.

[Zaxx]

The Underdrive weighs 2.4kg the std balancer weighs 4.2kg this is where the power comes from ...

[Franco Cozzo]

Originally Posted by cs123

The alternator is rated at what? 100 amp, So that is 1.2KW at full load.

Thats the amount of power it can generate at full load, its not 100% efficient as well mind you, it takes a good effort to spin it up under 100% load, and it might not do that 100a until 2000 RPM+.

Something interesting is I wired up a pair of spot lights for my mate on his Hilux, standard carby 22R engine, when he put his lows, highs and spotlights on the engine RPM dropped a fair bit, I reckon there is a good 5KW or so just on the alternator if its loaded up.

So you've lost around 5KW on the alternator, you've also got a power steering pump and a water pump constantly working, aircon compressor when it kicks in is another.

It all adds up, especially if you're at the point where you've hit the price/performance point on where you can't go anymore without engine rebuild, you look at all the little niggling things here and there, they add up.

I'm not keen on the slowing of the water pump though with the under drive, but I guess many people here have them and their cars are obviously doing OK.

[Drizz06]

Originally Posted by cs123

The alternator is rated at what? 100 amp, So that is 1.2KW at full load.

Alternator will never run at or anywhere close to 100% efficiency so you will need more engine power then equivalent alternator output.

[cs123]

Originally Posted by Drizz06

Alternator will never run at or anywhere close to 100% efficiency so you will need more engine power then equivalent alternator output.

Let's go with 50% then and on a chassis dyno the electrical load would be around 20amp. Fans off, AC off, just powering the computers, pump and ignition. So that would be around 480W with total load elimination. The underdrive does not negate this load anyway.

The whole idea of under driving the ancillaries is to protect them from high RPM operation.

I really find the claims of 10KW power improvement with underdrives dubious. I'd be more inclined to believe a back to back test without any tuning involved on the same day.

[Drizz06]

I agree with 10rwkw being optimistic, I'd be happy with a gain of 5.
http://youtu.be/kLKfYFXpqGI

[mike_nofx]

With a lighter balancer, is torque reduced?

[blue_ute]

It was 10 on a v8 I doubt you'll get that from the six and I was always told you need to get a tune on a b series for it to work

[FPV GTHO]

Theres been other underdrive threads before, and somebody had figures before of removing their drive belt and thus completely removing power to their accessories, and the power gain was only in the region of 15kw. So a 20% 6 cylinder kit isnt going to get 50% of that gain clearly.

[335POWER]

I'm umming and arring about getting this. Can't get it yet anyway but still contemplating it. Let's see if someone can convince beyond doubt....

[Zaxx]

Originally Posted by Troy23

I'm umming and arring about getting this. Can't get it yet anyway but still contemplating it. Let's see if someone can convince beyond doubt....

Why bother?

I don't want you to spend your money to go faster, i might get beaten.

Those with one run quicker those without don't simple.

[XR6T0Y]

Oh who ******* cares what power gains there are. Simple fact is, there is power gains. It's a cheap and good mod. Just ******* leave it there

[XR6_661]

Blah blah blah get one, don't get one who gives a flying.

[mike_nofx]

Originally Posted by XR6_661

Blah blah blah get one, don't get one who gives a flying.

This is a forum mate. You know, a place to discuss pros and cons of vehicles/products/whatever and to offer advice to people considering these things.

YOU obviously cared enough to open the thread, read through 2 pages then leave a comment.

Next time you are researching something and ask a question, hopefully you receive the same advice you have given here.

[SpoolMan]

Originally Posted by Troy23

I'm umming and arring about getting this. Can't get it yet anyway but still contemplating it. Let's see if someone can convince beyond doubt....

Tech guide for Mustang that explains it in detail, same principal on the workings for all models.
http://www.americanmuscle.com/underd...ech-guide.html

Some of you are getting steamed up over this thread, its being watched don't risk getting whacked with a few points.

[05_ENFORCER]

Double demerits Spooly ???????



.

[Kable72]

School holidays, double demerits :P

OT: I had one in my old BA and it gave it a little bit more oomph. Steering was heavier but I like heavier steering. Only thing I could tell that changed was the steering. Engine spun up a bit faster, too.

[Dash_XR]

Interesting, I wonder if this will put more strain on cars equipped with premo sound?

I was seriously considering this but the cost of a new alternator outweighs the extra few kw's you gain from these (mine is 100k old). People say anything under a 10% power increase you won't notice anyway.

I can understand why the NA guys do it as they don't have much else but for the rest doesn't seem much point to me.

[cs123]

Originally Posted by Dash_XR

Interesting, I wonder if this will put more strain on cars equipped with premo sound?

What you do have to be careful of is that at idle your alternator is spinning fast enough and the water pump working properly.

You don't want to be stuck in heavy traffic on a hot day with your engine overheating and your electric fans draining the battery.

Edit: Bad typing....

[SpoolMan]

Originally Posted by 05_ENFORCER

Double demerits Spooly ???????



.

Points system can lead to a member being banned once they have racked up a certain level of points in a period of time.
I like the idea of double points during silly seasons..j/k ..lol

[Madaya]

"You don't want to be stuck in heavy traffic on a hot day with your engine overheating and your electric fans draining the battery."
Kinda been there and done that. Removed the mechanical fan from my old Valiant and ran a manually operated thermo fan which was slightly undersized. Okay, engine quieter, heated up faster and if stuck in traffic, a flick of the switch and it was apples.
That was until I was stuck in Perth traffic on a blistering day, and the fan could not keep up. Had to pull over onto kerbs to let the motor cool. btw it was fine whilst motoring along, you don't need a fan, and my water pump and alternator where still at normal speed.
I reckon this could be the limiting factor. Ford test their vehicles to operate in certain extremes, and I would imagine extended idling in 40+ degree heat would be one of those tests.
Slow the water pump down, and the alternator to drive the radiator fans, it's 40 degrees and you want to operate the A/C. Mate, you might find trouble.
Underdrives are for racing and dragging. Obvious.

[mike_nofx]

Originally Posted by mike_nofx

With a lighter balancer, is torque reduced?

Still curious about this one???

[Bossxr8]

I can't see why people doubt them, they have been proven to work on Mustangs for over a decade or 2. Usually a gain of 8-10 hp at the wheels and a tenth or 2 on the strip. There must be literally hundreds of Mustangs with these fitted.

10rwkw claims are a bit excessive to me though.

[mike_nofx]

Why dont manufacturers fit them as standard?
If there is 5-10 extra kilowatts to be made, for no real loss, and for no extra money... They'd be mad not to???

note: I know manufacturers dont always fit the best parts from factory, but thats usually to save money. It wouldnt cost more for a lighter balancer.

[SpoolMan]

Originally Posted by mike_nofx

Why dont manufacturers fit them as standard?

Post 14.

[2011G6E]

Originally Posted by XBROO

Yeah never thought you would need that unless you were turning big revs, or of coarse blown. It won't do anything to the motor but it slows all the assessories down. Like just mention the steering might get a little heavier, aircond mighting pump as hard and the water will flow slower from the water pump.

Well that all sounds great...I'm sure that on a modified engine you want less coolant flowing around...

I'm sorry, but it all sounds a little too good to be true...you're still driving the exact same amount of equipment, so it shouldn't matter if it's slower or faster...and a "light balance" is just doing away with what its there for in the first place...plenty of guys years ago snapped cranks thinking doing away with that "big heavy balance" hanging off the crank snout was a good idea...

I thought under and overdrive pulleys were only for superchargers...?

[flappist]

Originally Posted by Bossxr8

I can't see why people doubt them, they have been proven to work on Mustangs for over a decade or 2. Usually a gain of 8-10 hp at the wheels and a tenth or 2 on the strip. There must be literally hundreds of Mustangs with these fitted.

10rwkw claims are a bit excessive to me though.

power = torque * rpm

By increasing the mechanical advantage on the belt you reduce the parasitic loss of the system but as the frictional losses are not linear and increase significantly as rpm increases the "10kw" will be demonstrated at peak rpm but will not be so evident at lower rpm.

There will also be a reduction in inertia with is really a two edged sword as although it will allow quicker rev increase it will also allow quicker rev loss with load increases such as hills etc. making the vehicle more "jerky". This also may introduce unwanted vibrations at various rpm. A graphic example of what can happen when you get it wrong is the clutch debacle in the early BA2 F6s where the V8 clutch from USA did strange things at certain rpm on the I6 as well as the oil pumps being destroyed on BA 5.4s.

You also reduce the efficiency of the components attached to the belt system which may lead to overheating, battery drain and in severe cases loss of steering response in extended periods of low rpm such as traffic jams.

The engineers who design these engines consider a lot more than 0-60km/h outside maccas on a Friday night. If you change the basic design of the engine be aware it may behave in ways that you don't expect and possibly bite you.

[2011G6E]

Why a, I reminded of what happened many years ago when they started measuring the horsepower of a car with all the ancilleries fitted, such as water pump and drive belts, an air cleaner, full exhaust system, alternator, etc? Some people complained bitterly that it suddenly made their dream cars look a lot less powerful, when all it did was face reality that a street car needs to drive things off the crank.

No idea why anyone would think it's a good idea to make your water pump and alternator work less efficiently...

[mike_nofx]

If your accessories spin 15-20% slower, but you drive your car at 15-20% higher RPM (than the standard Falcon drier does) all evens out?