Pulley 101 .......info for dummies like me

[G8-4-Speed]

Originally Posted by PQ

So, recently I discovered kinda what I suspected for a while........

My 2.8" pulley on the front of my Maggie ideally should be creating around 11-12 pounds of boost and not 8.

I have had my TVS2300 Magnacharger on my car for a long time now. LOVE it. But it never sat well with me that I am running such a small pulley to only get an 8-8.5 psi average through a dyno pull.

Now to be accurate, I am running a 3.2 inch pulley on it with my daily driving. Keeps me safe as far as boost goes and the 2.8 is not needed for the street anyway imo. I can throw the 2.8 on in 5 minutes if I want to go to the strip or have some fun.

But the 2.8" pulley produced an average of 8 pounds on the dyno and the 3.2 produced an average of 6 pounds. (see bottom two dyno graphs) Before my cam I had dynoed the car with a 3.6" pulley to a 7-8 pound average. I know I lose some adding a cam and I still have to get my cam specs but it's a mild cam and I can't see losing THAT much boost.

So now I'm going to be buying an OD cog drive for the back and getting a boost gauge so I can see what size pulley will net me an 8 pound average.

Now my ultimate question that drove me to create this thread is what the hell is the point of 6 rib 3.2 down to 2.8 pulleys if they can't pull solid and they slip so badly?

I mean that's some seriously shitty belt slippage to lose so much boost. I just don't feel comfortable with my car tuned for a level based on a slipping belt.

What if the belt decides one sticky day that it wants to grab for a minute? BOOM............... right?

Or is that not possible?

I may need a fuel rail or cut my existing fuel rail but I am going to get a rear OD Cog drive so I can take care of this but WTF? Why the hell are they selling these pulleys if they don't work?

I was thinking, instead of chasing belt slip, your problem could be much simpler...CHECK YOUR BY-PASS!

If your bypass blade set-screw is adjusted wrong, your bypass blade could be set open too far and bleeding off several pounds of boost. It is supposed to be just "cracked" open so it doesn't go into boost too soon under light throttle, keep cruising IAT's down, and keeps it from getting stuck closed. If you are curious, just back out the set screw 1 to 1 1/2 turns. If you boost climbs and drivability is still good, BAMB! fixed. Best news, cost nothing.....

[wkdivr]

If you have belt slippage, then there should be belt dust all over the front of the engine.

[PQ]

Originally Posted by G8-4-Speed

I was thinking, instead of chasing belt slip, your problem could be much simpler...CHECK YOUR BY-PASS!

If your bypass blade set-screw is adjusted wrong, your bypass blade could be set open too far and bleeding off several pounds of boost. It is supposed to be just "cracked" open so it doesn't go into boost too soon under light throttle, keep cruising IAT's down, and keeps it from getting stuck closed. If you are curious, just back out the set screw 1 to 1 1/2 turns. If you boost climbs and drivability is still good, BAMB! fixed. Best news, cost nothing.....

Are you talking about he actuator on the side? If so, I did have to replace it when I bought the blower. I assumed it was set the way it was supossed to be. And that Vengeance would have caught it.

Could it also cause the car to surge at all?

[PQ]

Originally Posted by wkdivr

If you have belt slippage, then there should be belt dust all over the front of the engine.

There was at the fest with the new tensioner. Brand new belt though.

[G8-4-Speed]

Originally Posted by PQ

Are you talking about he actuator on the side? If so, I did have to replace it when I bought the blower. I assumed it was set the way it was supossed to be. And that Vengeance would have caught it.

Could it also cause the car to surge at all?

Yes, that is it! I am sure it could cause all kinds of issues if it is opened far enough. The biggest one in your case is no-boost/low-boost. First, make sure the actuator rod isn't holding the linkage off the black set-screw. It is possible that the actuator rod is holding it open which is causing the surge since it in't solid like the set-screw and is flexing causing the big by-pass blade inside the blower to occilate open and close. It is only held on with two hex head screws so it should be an easy fix. It would also expalin why your power doesn't keep climbing like it should with a blower. Let us know what you find. Not saying anything one way or another, but I am sure Vengence doesn't hardly ever change these out so who is to say the guy who changed it just didn't un-bolt one and just throw the other one on. It looks simple enough so how can you screw it up, right???

[TriGun]

How much air is flowing through cylinders is more important than boost. For example if you have a blower with the stock headers and cats, the blower will produce more boost than larger header with no cats. But the the catless exhaust and larger header will allow more air flowing through cylinders and would increase the power.

[PQ]

Originally Posted by G8-4-Speed

Yes, that is it! I am sure it could cause all kinds of issues if it is opened far enough. The biggest one in your case is no-boost/low-boost. First, make sure the actuator rod isn't holding the linkage off the black set-screw. It is possible that the actuator rod is holding it open which is causing the surge since it in't solid like the set-screw and is flexing causing the big by-pass blade inside the blower to occilate open and close. It is only held on with two hex head screws so it should be an easy fix. It would also expalin why your power doesn't keep climbing like it should with a blower. Let us know what you find. Not saying anything one way or another, but I am sure Vengence doesn't hardly ever change these out so who is to say the guy who changed it just didn't un-bolt one and just throw the other one on. It looks simple enough so how can you screw it up, right???

OH. I can screw anything up. lol

But, I actually noticed exactly what you are talking about. That the set screw and metal flat part on the plunger arm will have a small gap from time to time. Next time it surges I'll get right out and look and play with it. As I type this it is touching like it should.

BUT

When the car is idling with not boost that arm is open all the way. It only closes at boost. The manifold vacuum holds that actuator up away from the set screw under vacuum.

Unless I missunderstand you.

Originally Posted by TriGun

How much air is flowing through cylinders is more important than boost. For example if you have a blower with the stock headers and cats, the blower will produce more boost than larger header with no cats. But the the catless exhaust and larger header will allow more air flowing through cylinders and would increase the power.

Ideally I"d create boost WITH bigger headers for even more power at the same boost with a less compression ratio.

But boost is boost. Displacement changes will always effect power.

[Supercharged SS]

Originally Posted by PQ

There was at the fest with the new tensioner. Brand new belt though.

Hey, I meant to say something to you in Indy but I got sidetracked, you're Maggie slide tensioner pulley is WAY to loose. Way, way to loose. Between the Maggie pulley and the JRE tensioner there only needs to be 1/4" of space. You have 3 inches!!!

[PQ]

Originally Posted by Supercharged SS

Hey, I meant to say something to you in Indy but I got sidetracked, you're Maggie slide tensioner pulley is WAY to loose. Way, way to loose. Between the Maggie pulley and the JRE tensioner there only needs to be 1/4" of space. You have 3 inches!!!

Oh shit......

Dammt.

I'll fix it immediately. Crap.

No biggie. I've really only been in boost on the drag strip and a few short jumps since.

[PQ]

Still ran 12.0s but might be why I never got in the 11s. I was within .06 of 11.99 on 3 straight runs. Ugh..........

[Supercharged SS]

Originally Posted by PQ

Oh shit......

Dammt.

I'll fix it immediately. Crap.

No biggie. I've really only been in boost on the drag strip and a few short jumps since.

There is a pic of mine either from Mindz or Russ. My two pulleys are almost touching. That's how they should be.

[PQ]

This?

[Supercharged SS]

Originally Posted by PQ

This?

Yup. I even made it tighter before racing.. Then my converter bolts backed out and made the knock sensors crazy!!

[G8-4-Speed]

Originally Posted by PQ

OH. I can screw anything up. lol

But, I actually noticed exactly what you are talking about. That the set screw and metal flat part on the plunger arm will have a small gap from time to time. Next time it surges I'll get right out and look and play with it. As I type this it is touching like it should.

BUT

When the car is idling with not boost that arm is open all the way. It only closes at boost. The manifold vacuum holds that actuator up away from the set screw under vacuum.

Unless I missunderstand you.

Ideally I"d create boost WITH bigger headers for even more power at the same boost with a less compression ratio.

But boost is boost. Displacement changes will always effect power.

You are correct, my bad. The valve will be OR should be full open at idle unless something isn't right. I have seen tunes with terrible idle that had no vacuum. The tune could be of causing the surge. Check it with the car off too see if it is against the set screw or if the arm is holding it up. IF it is against the set screw, then back it out one full turn. Another thing that can drop boost is lowering compression. Same with adding heading, it lowers boost.