8 replies to this topic

[enormous]

Bangastang recently released this pulley for the stock Eaton.

http://www.bangastan..._5_4_Blower.htm

[mullens]

I thought the snout had to be reconfigured for a 2.5 pulley? I know VMP had to do some modifications for theirs to fit.

[mustang loco]

mullens, on 07 February 2012 - 12:06 PM, said:

I thought the snout had to be reconfigured for a 2.5 pulley? I know VMP had to do some modifications for theirs to fit.

No, actually these were machined to fit without any mods done to the Eaton's snout!!

Edited by mustang loco, 08 February 2012 - 12:06 AM.

[Justin00Stang]

mullens, on 07 February 2012 - 12:06 PM, said:

I thought the snout had to be reconfigured for a 2.5 pulley? I know VMP had to do some modifications for theirs to fit.

I have not seen that pulley, but I can tell you what my experience was when we designed the VMP spec TVS.

We adhered to eaton minimum specifications and tolerances when designing the VMP TVS to handle a 2.5" pulley. We also noted the maximum possible tolerance stackup and took that into account. There is litterally a specification down to the thousandth for every part of a blower. We had to take an extra 3mm off the snout to safely accomodate a 2.5" pulley. 3mm is 1/8" so its a good amount. I believe steigmeire and metco also state that there is special machining required to use a 2.5" pulley.

I just did some math, and based on the minimum cross sectional area, minimum clearance, and minimum groove depth for the belt, the smallest I would go on a stock diameter snout is 2.58". Certainly you can cheat on groove depth, but then your belt makes flat contact instead of angular contact, that results in less surface area, and now your belt is riding up higher making the effective diameter larger. We all know what happens if you cheat on cross sectional area.

I will also add, I have measured pulleys that had the ribs mis-aligned by as much as 1/16" and totally deviated from the SAE groove profile in terms of section width and angles. If you put the pulley on an optical comparator you can spot it very easily. You know all those belt squeal problems people have? it's from deviating from the SAE groove profile too much. Within a few thousand miles the belt gets a funny wear pattern and squeaks when cold.

I tend to over-analyze everything, and in the process of designing our pulleys I found a myriad of intricacies.

[UnleashedBeast]

For the record, the Bangastang 2.5" pulley made for the stock Eaton M122 supercharger is manufactured by Sylvain "Autoliberte".

 Justin00Stang, on 10 February 2012 - 09:38 PM, said:

I have not seen that pulley, but I can tell you what my experience was when we designed the VMP spec TVS.

We adhered to eaton minimum specifications and tolerances when designing the VMP TVS to handle a 2.5" pulley. We also noted the maximum possible tolerance stackup and took that into account. There is litterally a specification down to the thousandth for every part of a blower. We had to take an extra 3mm off the snout to safely accomodate a 2.5" pulley. 3mm is 1/8" so its a good amount. I believe steigmeire and metco also state that there is special machining required to use a 2.5" pulley.

I just did some math, and based on the minimum cross sectional area, minimum clearance, and minimum groove depth for the belt, the smallest I would go on a stock diameter snout is 2.58". Certainly you can cheat on groove depth, but then your belt makes flat contact instead of angular contact, that results in less surface area, and now your belt is riding up higher making the effective diameter larger. We all know what happens if you cheat on cross sectional area.

I will also add, I have measured pulleys that had the ribs mis-aligned by as much as 1/16" and totally deviated from the SAE groove profile in terms of section width and angles. If you put the pulley on an optical comparator you can spot it very easily. You know all those belt squeal problems people have? it's from deviating from the SAE groove profile too much. Within a few thousand miles the belt gets a funny wear pattern and squeaks when cold.

I tend to over-analyze everything, and in the process of designing our pulleys I found a myriad of intricacies.

Justin....sounds good with all the technical talk, but I assure you, Sylvain's 2.385" pulley on my VMP TVS is rock solid with zero belt slip/squeals/noises. After sending him the 2.5" that was removed, it was determined that a 2.375" is possible. In all fairness, I am using a bolt on 90mm idler to eliminate the possibility.

With that said, I will tell you this.....My car with the standard 2.5" pulley, your (VMP) stock location 90 mm idler replacement pulley (no metco bolt on style 90mm installed), and a thump tensioner did have belt slip above 4,000 rpm. My assumption is the smaller pulley on the Thump tensioner wasn't capable of taking up enough belt slack like the stock tensioner pulley size would. The same stock length belt was used for both configurations discussed in this post.

17-17.5 PSI with stock lower, no cats, and 3" exhaust all the way from the stock exhaust manifolds back.

Edited by UnleashedBeast, 22 February 2012 - 12:30 PM.

[lawdude]

 UnleashedBeast, on 22 February 2012 - 12:07 PM, said:

For the record, the Bangastang 2.5" pulley made for the stock Eaton M122 supercharger is manufactured by Sylvain "Autoliberte".



Justin....sounds good with all the technical talk, but I assure you, Sylvain's 2.385" pulley on my VMP TVS is rock solid with zero belt slip/squeals/noises. After sending him the 2.5" that was removed, it was determined that a 2.375" is possible. In all fairness, I am using a bolt on 90mm idler to eliminate the possibility.

With that said, I will tell you this.....My car with the standard 2.5" pulley, your (VMP) stock location 90 mm idler replacement pulley (no metco bolt on style 90mm installed), and a thump tensioner did have belt slip above 4,000 rpm. My assumption is the smaller pulley on the Thump tensioner wasn't capable of taking up enough belt slack like the stock tensioner pulley size would. The same stock length belt was used for both configurations discussed in this post.

17-17.5 PSI with stock lower, no cats, and 3" exhaust all the way from the stock exhaust manifolds back.

I have a polished TVS SC that was part VMP group buy done right before he came out with the VMP TVS. It has a 2.59" pulley, which Justin says is the smallest that will fit. Do you have an opinion as to whether this 2.5" pulley would work?

Edited by lawdude, 22 February 2012 - 05:45 PM.

[mustang loco]

 UnleashedBeast, on 22 February 2012 - 12:07 PM, said:

For the record, the Bangastang 2.5" pulley made for the stock Eaton M122 supercharger is manufactured by Sylvain "Autoliberte".

+1

 lawdude, on 22 February 2012 - 05:42 PM, said:

I have a polished TVS SC that was part VMP group buy done right before he came out with the VMP TVS. It has a 2.59" pulley, which Justin says is the smallest that will fit. Do you have an opinion as to whether this 2.5" pulley would work?

Don't want to try the same as UnleashedBeast,s?

[Justin00Stang]

That is understandable that it would slip with the thump tensioner and smaller pulley it comes with, which is there for extra clearance. it is possible to swap the stock pulley back onto the thump tensioner though, however if you have a metco aux idler bracket its not a big deal.

We can't work that far outside the minimum spec on pulley design, but if someone wants to assume the risk and go thinner than they can certainly do that. Though based on your quoted boost number it doesn't seem that it was much of an improvement, much bigger gains would be seen from a lower.

Mike, emailing you.

 UnleashedBeast, on 22 February 2012 - 12:07 PM, said:

For the record, the Bangastang 2.5" pulley made for the stock Eaton M122 supercharger is manufactured by Sylvain "Autoliberte".



Justin....sounds good with all the technical talk, but I assure you, Sylvain's 2.385" pulley on my VMP TVS is rock solid with zero belt slip/squeals/noises. After sending him the 2.5" that was removed, it was determined that a 2.375" is possible. In all fairness, I am using a bolt on 90mm idler to eliminate the possibility.

With that said, I will tell you this.....My car with the standard 2.5" pulley, your (VMP) stock location 90 mm idler replacement pulley (no metco bolt on style 90mm installed), and a thump tensioner did have belt slip above 4,000 rpm. My assumption is the smaller pulley on the Thump tensioner wasn't capable of taking up enough belt slack like the stock tensioner pulley size would. The same stock length belt was used for both configurations discussed in this post.

17-17.5 PSI with stock lower, no cats, and 3" exhaust all the way from the stock exhaust manifolds back.

[UnleashedBeast]

 Justin00Stang, on 23 February 2012 - 08:27 AM, said:

Though based on your quoted boost number it doesn't seem that it was much of an improvement, much bigger gains would be seen from a lower.

Your supercharger with the 2.5" pulley, my car with high flow cats on the 3" JBA setup, only made 16 PSI at max boost. When I gutted the cats and added the 2.385" upper pulley, it now peaks at 17.5 PSI. I'd say that's a big improvement with losing the cats. Sure, I would have gained more with a 10 or 15% lower, but this puts me right on the edge of max boost without race gas. That's as much as I want.

 lawdude, on 22 February 2012 - 05:42 PM, said:

I have a polished TVS SC that was part VMP group buy done right before he came out with the VMP TVS. It has a 2.59" pulley, which Justin says is the smallest that will fit. Do you have an opinion as to whether this 2.5" pulley would work?

The 2.385" will not fit the stock snout on that blower. Sylvain does make a special 2.55" that will fit any FRPP TVS style blower, which is what the polished version is.

Edited by UnleashedBeast, 23 February 2012 - 08:54 AM.