Bigger idler or aux idler?

[Larsonator]

I'm sure this is a dumb question, but I can't seem to find what the difference is between upgrading the stock idler to 90mm vs adding an aux idler.

I'm planning to put a 2.5" upper on my 2011 and it's unclear if I should be looking for the 90mm, aux idler setup, or both. I realize the aux idler will give better belt wrap, but I don't know when that becomes a concern.

Thanks for the help.

 

[Carbd86GT]

Replacing the stock idler with a 90mm idler helps take up the extra slack when installing a smaller pulley on the blower, and that's about it. The auxiliary idler not only takes up that slack, but also improves belt wrap around the blower pulley to help eliminate belt slippage.

 

[Larsonator]

so I should just skip the 90mm idler and go with just an aux idler setup.

 

[Carbd86GT]

That would be my recommended set-up. The 90mm idler does work to an extent because it allows you to keep your stock belt length, but it doesn't increase belt wrap which is what's needed with the smaller supercharger pulleys. It's more expensive in the short run, but I believe it will prove to work better and be more consistent over time.

We have an assortment of auxiliary set-ups that can be found here: http://www.lethalperformance.com/2011-2012-shelby-gt500/pulleys/idler-pulleys-and-tensioners.html

I prefer the looks of the DivisionX set-up and the fact that it comes standard with a dual bearing idler for even better durability, but Metco and Steeda also make nice kits.

 

[SRT8tech]

I run both on mine with a 2.4 upper pulley and stock belt. I found just the 90mm idler was not enough and had a very small amount of belt slippage. I added the Steeda aux adjustable tensioner and all is well. I didnt have to really tighten the aux tensioner that much to stop the belt slippage.

 

[Larsonator]

Thanks for the feedback guys. I'll start with the aux idler and 2.5" upper and add the 90mm later if it seems like it needs it.

 

[Van@RevanRacing]

I'm sure this is a dumb question, but I can't seem to find what the difference is between upgrading the stock idler to 90mm vs adding an aux idler.

I'm planning to put a 2.5" upper on my 2011 and it's unclear if I should be looking for the 90mm, aux idler setup, or both. I realize the aux idler will give better belt wrap, but I don't know when that becomes a concern.

Thanks for the help.

I've got a number of customers running the 2.5" pulley and 90 mm idler and no belt wrap problems. Recently in a thread here on SVTP I had a customer trying to install a belt with an aux idler. There is a downside to the aux idler. They have a tendency to cause a lateral load on the snout essentially pulling on the snout due to the increased tension. There have been internal supercharger gear failures attributed to the aux idler with many different brands of superchargers.

Van

 

[John@Lethal]

Thanks for the feedback guys. I'll start with the aux idler and 2.5" upper and add the 90mm later if it seems like it needs it.

Let myself or Derek know if you need anything else in the meantime, here's a link to the DX Aux kit.

DivisionX GT500 Auxiliary Idler Bracket with Dual Ball Bearing Idler

Bracket, and DX dual ball bearing already included. In stock and ships for free.

Thanks!

 

[Carbd86GT]

Van,

That doesn't make any sense, to blame an aux idler for blower damage. The aux idler doesn't add any tension at all, you are still using the same belt tensioner. All the aux idler does is take up the slack when using a smaller pulley and then add additional belt to pulley contact. The grip comes from more surface area of pulley being covered by the belt, not more tension (or load on the bearings which is what you're describing).

 

[dirtyo2000]

op:

 

[Van@RevanRacing]

Van,

That doesn't make any sense, to blame an aux idler for blower damage. The aux idler doesn't add any tension at all, you are still using the same belt tensioner. All the aux idler does is take up the slack when using a smaller pulley and then add additional belt to pulley contact. The grip comes from more surface area of pulley being covered by the belt, not more tension (or load on the bearings which is what you're describing).

Derek

I'll clarify. The aux idlers that are adjustable and allow the owner to place added pressure and tension on the belt have caused internal gear failures on the supercharger and gasket failure, perhaps in the most extreme position setting. The number of failures is low but it has happened and documented. I had a customer with an oem blower using one that was road racing in the most extreme position with a Metco, the blower got hot, everything was hot, and the front gasket seal of the supercharger expired and oil leaked out of the supercharger. The gasket was compromised on the upper portion of the blower and not the lower due to the added wrap and tension.

Van