Powerdyne pullies in relation to Boost-Let's get the info. straighten out

[Mighty Thor]

I've gotten several e-mail asking me about this. I thought I go ahead and share it with you guys.

Now the info. is based on my personal experience, experience of others here, what I found out from Vector Perf. and from what I've heard from other PD users not particularly V6.

For those of you thinking of buying a pulley, we know that ASP racing company makes the right one for us. Be sure that it is horizontally grooved and you do the JohnD wrap.

Determining which pulley size to get in order to give the right boost is very tricky. As far I understand, the better the exhaust system, the better the SC will perform. But it also has a tendency of decreasing boost.

For example, I still have my exhaust manifold (I keep it for emission reason)with 3.1 pulley I have gotten 7-8 psi (I've even spike it up to 11 psi one time). A person with headers with the same size pulley will probably make 5-6 psi. Now is this a bad thing? No, not all. It just means that your car breathes better. A person with headers, port and polish heads and cam with the same size pulley will make 3-5 psi. Again, this is not a bad thing.

Depending on what mods you have in your car, you have to determine the right pulley size in order to get the boost you want.

This is what I know about pulley size in relation to boost.

Powerdyne SC for 3800 II w/ headers and full exh.
Pulley Size:- Boost:
3.1- 5-6

2.9- 7-9 (8 ave.)

2.8- 8-9

2.75- 9-11 (10 ave.)

2.70- 10-12

2.65- 12-14

2.6- 13-15

2.5- 15-16

2.5 is as low as I've heard people have gone on the Powerdyne and this wasn't on the V6 3800 II but on a Mustang V8. So I guesstimated on the boost. SSMS5411, Steve, has gone as low as 2.25 and the PD was fine. Since his internals are heavily modified we don't know how much boost it would be for our stock engine.

The smaller you go on the pulley the more immediate the boost comes on. It gets better from the bottom to the top of your RPM. Yes, centrifugal SC is awesome at top end.

If you plan to go any lower than 2.9 pulley, I highly recommend that you upgrade the bearings to 7 ton and internal belt to kevlar.

I hope this information has been helpful.

Feel free to crituque or add to it.

[grayman]

That sounds about right MT.

You have also touched on an important topic: boost psi vs total breathing capacity of engine.
He is right gang. Lack of boost on the boost gauge does not always mean lack of hp from the engine if it is due to the engine breathing better (fat exhaust/headers/cam/rockers/heads) because the extra air from the supercharger is getting used rather than building back pressure and hence a positive reading on the boost gauge.

People should also be careful if they are planning to upgrade to a smaller pulley. In the list above 'averages' are given and this is mainly due to slippage. I wouldn't suggest planning on a real small pulley without taking the precautions to upgrade the fuel system and the fuel tuning in order to handle the possible spikes. It's not likly to be the HP output (mechanical stress) that will kill a 3800 as much as it is a lean condition burning up the engine because the fuel system could not keep up with 12 or 13 or 15 psi of air.

[Mighty Thor]

Originally posted by grayman:
That sounds about right MT.

People should also be careful if they are planning to upgrade to a smaller pulley. In the list above 'averages' are given and this is mainly due to slippage. I wouldn't suggest planning on a real small pulley without taking the precautions to upgrade the fuel system and the fuel tuning in order to handle the possible spikes. It's not likly to be the HP output (mechanical stress) that will kill a 3800 as much as it is a lean condition burning up the engine because the fuel system could not keep up with 12 or 13 or 15 psi of air.

That's good you mention fuel to boost. Maybe we can create some kind of system that everyone can follow, both SC and Turbo. That you need this much fuel for this much boost. And what guide lines to follow.

For example, a stock injector and FMU on a stock 3800 engine is good for 10 psi of boost. Or they wish to ditch the FMU and do injectors then 24 would do nicely for 6-7 psi. If someone wants to do 10-12 then 34 injectors would suit nicely. Something like that. This help to get the guessing out.