25% Underdrive pulleys, are they worth it?

[MyM8V8]

?

[ringram]

Of course mate
I have a spare 25% underdrive ATI pulley, wont fit my Corvette configuration.
Im not sure what power they free up, but quite a few blokes swear by them. Probably worth a few bhp.

[tinker-27]

use ati and nothing else as we have had issues with cam chains snapping and it looks like it was the under drive pulley !! ati are the best dont use anything else .

[stevieturbo]

Why would it cause the cam chain to snap ?

I use Powerbond, and never had a problem...although it isnt underdrive. I'd only ever consider an under drive for a high rpm engine, that sees high rpm a lot.

[MyM8V8]

ringram said:

Of course mate
I have a spare 25% underdrive ATI pulley, wont fit my Corvette configuration.
Im not sure what power they free up, but quite a few blokes swear by them. Probably worth a few bhp.

Is that the one that keeps falling off or dropping the belts?

I have a lovely Powerbond corvette 10% underdrive supplied to me by.... But it bloody don't fit my Ute and I don't seem to be able to get it swapped for the right one!!!

I got it for the weight reduction more than the underdrive. Are the ATI units lighter than stock?

Edited by MyM8V8 on Tuesday 21st July 13:52

[MyM8V8]

stevieturbo said:

Why would it cause the cam chain to snap ?

I use Powerbond, and never had a problem...although it isnt underdrive. I'd only ever consider an under drive for a high rpm engine, that sees high rpm a lot.

Is that one the corvett or GTO offset? Is it lighter than stcok Stevie. Why the change for you?

[MyM8V8]

tinker-27 said:

use ati and nothing else as we have had issues with cam chains snapping and it looks like it was the under drive pulley !! ati are the best dont use anything else .

Did you see any power gains Craig, or is it just the extra acceleration?

[well_fans]

I was under impression all the underdrive did was reduce the losses through the ancilliaries like the alternator, air con pump etc by reducing the rpm they were driven at so gaining a few hp back? Didnt think it would make a real difference to acceleration on its own?

[Boosted LS1]

My take is that if the engine's revving higher you use an underdrive to stop the water pump cavitating and the alternator and other ancilliaries revving their nuts off, maybe sapping power. Downside might be that the alternator doesn't kick in as quickly as usual at low revs which can effect charging.

[ringram]

They say 25% underdrive needs an idle of 800rpm min for it to work.

Thats stock vxr8 idle speed for an LS2 anyway.

[MyM8V8]

ringram said:

They say 25% underdrive needs an idle of 800rpm min for it to work.

Thats stock vxr8 idle speed for an LS2 anyway.

That would not appear to be a problem then.

Do you want to get rid of yours?

[stevieturbo]

MyM8V8 said:

stevieturbo said:

Why would it cause the cam chain to snap ?

I use Powerbond, and never had a problem...although it isnt underdrive. I'd only ever consider an under drive for a high rpm engine, that sees high rpm a lot.

Is that one the corvett or GTO offset? Is it lighter than stcok Stevie. Why the change for you?

Same as Camaro/GTO, its steel and its heavy.


But it allows me to bolt my blower drive to it

[toothrot]

I have a spare YPVS Powerband

[Brummmie]

There is thought that they can provoke timing chain failure, harmonics/dampening and all that.

[tinker-27]

harmonics the skyline boys have the same problem, i woulnd bother maybe a couple of bhp gain but never done one back to back.

[MyM8V8]

toothrot said:

I have a spare YPVS Powerband

What's that then mate? Do you mean PowerbOnd? Was it off your old LS1?

[Bonnie and Clyde]

MyM8V8 said:

toothrot said:

I have a spare YPVS Powerband

What's that then mate? Do you mean PowerbOnd? Was it off your old LS1?

He means UPVC. Its the trim of his bathroom window

[toothrot]

MyM8V8 said:

toothrot said:

I have a spare YPVS Powerband

What's that then mate? Do you mean PowerbOnd? Was it off your old LS1?

Of an old RD350 - this underdrive sounds like a good idea in theory but is it worth it over all? Personally I'd rip the Aircon out

[MyM8V8]

toothrot said:

MyM8V8 said:

toothrot said:

I have a spare YPVS Powerband

What's that then mate? Do you mean PowerbOnd? Was it off your old LS1?

Of an old RD350 - this underdrive sounds like a good idea in theory but is it worth it over all? Personally I'd rip the Aircon out

Well put it like this, if I can get another 12-15rwhp it gets me into the 11's

[toothrot]

Thought you had the potential already? Ditch the AC if possible though, thats a good few KG saving