Get more boost from your Roe Blower!

[David Weaver]

I have been toying with the idea of making a larger crank pulley. Finally did it and the results have been outstanding so far. Sean Roe told me the max RPM for his blower is 21,000 RPM's. By my calculations, the 8 inch diameter pulley I have built puts the blower at that limit with a 2.5 inch pulley.

The test car is a built motor with ported blower manifold, ported heads, custom camshaft, 2.5 inch blower pulley. The VEC2 log was indicating 9 to 9 1/2 lbs of boost. The car was making 680 HP on a conservative, Texas hot climate tune. I bolted on the pulley and made 721 with no other changes. The log indicates 12 lbs of boost at the hit and 11 through the dyno run.

In addition, this larger pulley will allow you to go to a larger blower pulley while maintaining the same boost level. This should make for better belt wrap/adhesion and less belt slip by using the larger diameter blower pulley.

The pulley is made from billet aluminum on a CNC machine. I have not done any "durability" testing. I built this identical to an aftermarket Viper underdrive pulley. The only difference is the diameter so I am confident that the pulley will hold up just fine. There is just enought clearance between the pulley and the water pump to be able to change the belt.

You can see pics of the pulley at the alley under viper discussion. My user name is the same there. I will be heading out of town this evening and will return on Tuesday the 6th. I am offering these pulleys for $249.99 for the initial run. Please PM me for more information.

Thanks, DW
www.americanracingtech.com

[v10kingsnake]

no durability testing sounds risky unless you were referring to durability of the part. how about the effects of spinning the sh*t out of the blower. doyou have an idea of what rpms the roe spins at say 5,8, 10 psi on a stock crank pully car. this would help us visualize the safty aspect of this.

[David Weaver]

by durability, I mean I haven't had this part on the car for weeks and miles, I am referring to the part. I do not see any other issues this would cause other than more power and torque.

Like I said above, max blower rpm per Sean Roe is 21,000 which with this pulley and the 2.5 inch blower pulley equates to 21,000 blower rpms at 6000 engine rpms. Easy math to calculate the other pulley's rpms, I have not taken the time to do that. I wanted to meet Roe's spec for max blower rpms.

DW

[plumcrazy]

and i bet if ya dont run up to 6000 rpm there is LESS chance of hitting the max.

right ?

[orlandov10]

I'm not familiar with Viper underdrive pulley's but coming from the Supra world, we had some people including myself pull off the factory harmonic balancer (underdrive pulley) and replace it with a billet aluminum lightweight underdrive pulley from Unorthodox Racing, the result was broken flywheel bolts, we came to figure out the lighter underdrive pulley threw off the balance in the crankshaft, causing vibration that eventually broke flywheel bolts, I can imagine this wasn't very good for the rod bearings either. Just thought I'd throw this out there.

[David Weaver]

and i bet if ya dont run up to 6000 rpm there is LESS chance of hitting the max.

right ?

the way I calculate the numbers, you would be correct. 6000 engine rpm's equal 21,000 blower rpm's

[David Weaver]

I'm not familiar with Viper underdrive pulley's but coming from the Supra world, we had some people including myself pull off the factory harmonic balancer (underdrive pulley) and replace it with a billet aluminum lightweight underdrive pulley from Unorthodox Racing, the result was broken flywheel bolts, we came to figure out the lighter underdrive pulley threw off the balance in the crankshaft, causing vibration that eventually broke flywheel bolts, I can imagine this wasn't very good for the rod bearings either. Just thought I'd throw this out there.

This is not the balancer, it is a larger diameter belt pulley, basicaly, an overdrive pulley, to spin the supercharger faster.

[ab]

I have a 8.5" lower crank pulley..

If you are worried about harmonic damage..I would get an ATI damper.

I see nothing wrong what David Weaver is doing nor can I see any damage it would cause, plus there's less chance of belt slippage since you are keeping a larger pulley diameter on the blower but getting the benefit of a smaller pulley without the slippage.

[Sean Roe]

Hi David,
Good idea and HP gain.
What did the torque increase look like?
Regards,
Sean

[v10kingsnake]

is the sean roe unit made by the same company that produces the kenne belle unit for the cobra crowd. i know hood clearence is tight with current setup, but is there any plans to increase the blower displacement like they do in the mustang forums or not. this help these cobra guys run lower boost with same or more power than the unported or smaller displacement blowers do running greater boost and timing.

[00prowler]

Sounds like a good idea...do you have to rework the vec2 cards for timing,fuel,etc? What about going over 10 lb of boost with a stock fuel pump with a booster? Thanks...Al

[proracer1]

I would be in for a pulley.I already have a beefed up bottom end and Jeff Morys cyl heads...What kind of changes did you make to the VEC 2....

[Simms]

I'm interested.

[VIPR GTS]

More info?

[BlueGTS]

Now how would this work if you already pinned your stock crank?

[BobK898]

I had my crank pinned this weekend, highly recommended.

[BlueGTS]

I know that pinning is a good thing as I did it when I put my blower on. My question is how do I pin the new crank pulley considering I have 2 half circles in my crank from the original pinning.

[David Weaver]

Hi David,
Good idea and HP gain.
What did the torque increase look like?
Regards,
Sean

Thanks Sean, the torque went from 712 to 770.

Of course you have to make changes to the VEC programs as you are now moving more air so it will be leaner and you may need to reduce the timing for the higher boost levels.

Again, this is only the belt pulley, not the balancer so it does not affect the pinning of the crank.

This car is a 99 with a stock bottom end, ported heads, ported blower manifold, custom cam specs.

DW

[Shelby3]

What's the latest on this mod? Anyone running with it that wants to share their experience to date?

[Joseph Dell]

I've heard of a couple of folks running the pulley but I have no 1st hand experience with it... yet. planning on installing it on a car in a couple of weeks so i'll report back then.

i did this with a mustang a few years back(had ASP make me a custom pulley) and it worked like a champ!

JD

Now wouldn't the power steering and air conditioner run much harder since they still have the smaller diameter pulley wheels? At what point would their smaller wheels and faster RPMs do damage to the power steering and air conditioner?

Other than that, this larger main pulley wheel looks like a potential winner.

I have been toying with the idea of making a larger crank pulley. Finally did it and the results have been outstanding so far. Sean Roe told me the max RPM for his blower is 21,000 RPM's. By my calculations, the 8 inch diameter pulley I have built puts the blower at that limit with a 2.5 inch pulley.

The test car is a built motor with ported blower manifold, ported heads, custom camshaft, 2.5 inch blower pulley. The VEC2 log was indicating 9 to 9 1/2 lbs of boost. The car was making 680 HP on a conservative, Texas hot climate tune. I bolted on the pulley and made 721 with no other changes. The log indicates 12 lbs of boost at the hit and 11 through the dyno run.

In addition, this larger pulley will allow you to go to a larger blower pulley while maintaining the same boost level. This should make for better belt wrap/adhesion and less belt slip by using the larger diameter blower pulley.

The pulley is made from billet aluminum on a CNC machine. I have not done any "durability" testing. I built this identical to an aftermarket Viper underdrive pulley. The only difference is the diameter so I am confident that the pulley will hold up just fine. There is just enought clearance between the pulley and the water pump to be able to change the belt.

You can see pics of the pulley at the alley under viper discussion. My user name is the same there. I will be heading out of town this evening and will return on Tuesday the 6th. I am offering these pulleys for $249.99 for the initial run. Please PM me for more information.

Thanks, DW
www.americanracingtech.com

[Catwood]

Have had a blower car, non Viper, that I ran a big crank pulley and small blower pulley all I can say is the improvement to mid range was awesome. I did overspin the blower at higher RPM but in my case that was a loss of efficiency and a creation of heat. For the few seconds on the track it didn't seem to hurt but the explosive power on the street was well worth the tradeoff.

[Shelby3]

I bought one today and should have it on by next week. I'm hoping it will blow the pickles out of my Belangers and free up some RWHP.

Joseph, thanks for all the info the other day, I'll report on my results as soon as I get it on the dyno.

[99 R/T 10]

Jim,
you may need to check the tune after you install it

[Shelby3]

Jim,
you may need to check the tune after you install it

For sure. It should lean out the tune which might just be the ticket as I'm running a bit rich with the 50/50 water mix I recently started using. Do you have one and if not why not?

[99 R/T 10]

U've got one, but not installed. I already have boost creep up to 11 pounds with my 8 lbs pulley. I'll wait until I do the heads, otherwise I won't see much of a benifit.

[Catwood]

U've got one, but not installed. I already have boost creep up to 11 pounds with my 8 lbs pulley. I'll wait until I do the heads, otherwise I won't see much of a benifit.

If this works like it did in my application it wasn't to get max boost but to get more boost sooner (or lower) in the RPM band.

[Simms]

I bought one today and should have it on by next week. I'm hoping it will blow the pickles out of my Belangers and free up some RWHP.

Joseph, thanks for all the info the other day, I'll report on my results as soon as I get it on the dyno.

Any updates on this Jim?

[Shelby3]

Any updates on this Jim?

I'm putting it on the dyno tomorrow and will post with results by Saturday. Earlier if it blows up.

[Shelby3]

Any updates on this Jim?

Pulley installed. Could not find a 7 ribbed belt that fit the new set up. Threw on a 6 ribbed belt that slips and will tackle again next week.