Questions about pulleys...

[HotsideHamid]

Hey all!
So I have a hotside setup with the TDR IC, Mack BTB, 550cc injectors and the Hydra ecu running my '97. Currently, I'm using one of Tom's 125mm crank pulleys and I assume a 65mm nose pulley that came with the blower from BRP/SOT.
It looks like I'm hitting about 10psi of boost at redline. Does this seem about right for this pulley combo? Do the old BRP pulleys have a bad rap for slipping? I was also curious about the range of pulley sizes. In case I wanted to up the boost further down the road, would it be pointless to move up to a 130mm from a 125mm? The reason I ask is because I can't seem to find how much average power gains you get from going up 5mm on the pulley. Is it only like 10hp? Or is it higher, and therefore worth it?
I know Bill highly recommends staying at 130mm with the stock block, but it seems I have the right setup for upping it a bit. In the end, I want around 250hp and call it a day.... Ish ;).
BTW, I love this setup!

-Hamid

[Tom @ Fast Forward]

Bill will be best to answer your question but he is running 130/65 and makes the 250 WHP you are looking for. I don't remember the boost?

[chuckerants]

When Tom first discovered that the BRP pulleys were causing belt slip, he changed out the supercharger pulley as well on my car.

You may want to do that first.

[HotsideHamid]

Yes, I just read a little bit of that when I did a search. I'm wondering if I could be losing something as well. It could be that I'm a little paranoid though too! Tom, just out of curiousity, if you still have the nose pulleys available, how much are they?

-Hamid

[Tom @ Fast Forward]

They are $75 but I am out of stock at the moment. Should have more in a couple weeks.

[HotsideHamid]

Okay cool. I think I may get one to ease my mind.

-H

[FormerDatsun510Man]

With the 130/65 pulley combo my setup sees 13psi at 7000rpm, 11psi at 6000rpm, etc. It sounds like you might possibly be having some belt slip because the 126 pulley should be only 1psi lower. The real answer though is in the dyno numbers. My setup managed 240rwhp with the 130/65 pulley combo. I would expect something around 210-230rwhp with a 126 pulley, depending on a number of factors (intake manifold, exhaust, etc.). I know I put a pretty big range there, but things add up to make a difference. For example, with the older BRP style supercharger outlet, stock intake manifold and stock exhaust, I would expect a 126 pulley would put you somewhere in the 210-215rwhp range. On the other hand, with the new FFS/Moss outlet, R4 intake, header and catless exhaust you might be closer to 230rwhp. From my experiences though, I wouldn't worry about chasing every last hp, it gets expensive. Rather settle in at a pulley and tune it. The max pulley I would recommend on a stock engine is a 130, even though you can get away with 140.

Bill

[HotsideHamid]

Thanks Bill. I need to watch the boost gage more closely-- things start to happen really fast up at 6000rpm, and I don't want to take my eyes off the road. I think I may end up getting a new nose pulley from Tom just to eliminate any chances of belt slip. It looks like there are plenty of minor upgrades that I can do to get a few hp here and there. In fact, I still have my AFM on my intake hose unplugged, even though with the Hydra I don't need an AFM. I just haven't found a small piece of pipe that will replace the AFM yet. Not sure if that's alot of hp though. I guess I should keep the upper limit at 130mm then. I gotta admit though, when I heard you say that you can loose traction in 3rd gear going around a bend, that just made me drool!
Slightly off topic-- Tom, how in the heck are you able to get 10psi at 2000rpm? I think I'm around 6psi at 2000rpm.

-Hamid

[Tom @ Fast Forward]

Coldside. Coldside. Coldside. :)

The Coldside doesn't have any losses on silly things like intercoolers. We're non-intercoooooled, doncha know? :) Also, the Coldside doesn't have an outlet manifold, no matter how efficient, to reduce boost. Thirdly, with much reduced throttled volume, it makes boost quicker as it doesn't have much space to compress air into. Think of two identical 3HP 100PSI air compressors. One with a 1 gallon tank and one with a 10 gallon tank. Switch them both on simultaneously. Which one hits 10PSI first? I think my 130/65 Coldside runs about +4PSI to Bill's 130/65 Hotside. However, he makes about 25WHP more due to the cold air from the A/A IC. But mine weighs at least 50 pounds less. It is all give and take. I'll take 25 less WHP. :)

Slightly off topic-- Tom, how in the heck are you able to get 10psi at 2000rpm? I think I'm around 6psi at 2000rpm.

-Hamid