As you increase airflow (intake and exhaust), you generally need to lower the pulley diameter to maintain adequate boost levels. My questions is, what is the ideal boost levels for our cars? I'm guessing we want to run some where around the 10 psi level? I've heard of people hitting 14 psi and don't know the facts on boost. Can someone give some guidance?

There is no real ideal level, you run as much boost as you need or are able to.

ie. you open up the exhaust and the intake you Can decrease the pulley size for even more power but you dont Have to.

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Bone Evil

Mods: Tog Headers, cat delete, Al 104's gapped .050, 1.9 rockers, 105 springs,
Intense FWI, DHP Power Programmer PCM, Intense tranny with gen2 lsd,
Aeroforce scan gauge, Clear front and back, N* TB & LQ4 Maf,
Hoosier slicks, ZillaMotorsports P/P GenV & LIM

Pisco_Paul wrote:

Every time you pat my head, you pat a piece of my valve retainers.

How do you know how much boost we are "able" to have? When planning future upgrades, how do you know what pulley size to go with? Is it a trial and error process? If so, that can be very costly considering pulleys are about $70 a piece. I think the general rule of thumb is, for every .1" diameter smaller the pulley, the gain is +1 psi. Can anyone confirm?

Yes .1 drop in pulley size is about 1psi of boost.

And for lack of a better response, 'experience' steers us to what pulley size to use.

I recently went from a gen3 to a gen5 supercharger, I had read from others that I would need to increase my pulley size by .2 due to the gen5 being more efficient.
However because I run a little more advanced timing I had to increase by .3 to eliminate kr. I could have pulled the timing and went with the smaller pulley but wanted the fuel economy of increased timing.

_________________
Bone Evil

Mods: Tog Headers, cat delete, Al 104's gapped .050, 1.9 rockers, 105 springs,
Intense FWI, DHP Power Programmer PCM, Intense tranny with gen2 lsd,
Aeroforce scan gauge, Clear front and back, N* TB & LQ4 Maf,
Hoosier slicks, ZillaMotorsports P/P GenV & LIM

Pisco_Paul wrote:

Every time you pat my head, you pat a piece of my valve retainers.

Your FIRST .1 decrease is 1psi. Each .1 from there is less than .1 as you create more heat, and reduce the density of the air. Cold air is more dense, hot is less.

But that's a very basic comparison, as there are other benficial mods that will REDUCE boost pressure.

PRESSURE does nothing for you. Boost FLOW in CFM is what you're after. Frankly, your boost gauge on a supercharged car is useless other than to tell you the system is working.

_________________

Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

Finding the proper pulley size is a lot of trial and error since each car is different and you may find what works one day will cause KR the next. You may also find that an increase in timing yields more power than that extra .1 smaller pulley. Generally, with the S2 L67 once you start seeing 13-14 psi it's time to think about making the engine breathe better before going any smaller with the pulley.

Also keep in mind that higher boost numbers don't always mean more power, since what's important is how well you can flow the air the blower is pushing through the motor. Take the 2.8 pulley I run on my car for example. On a stock motor that pulley would probably translate into 16-18psi and a few melted pistons; but because my motor has a cam, headers, intercooler etc. I only see 11.8 psi on a good day.

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Aaron

1996 SSEi (year confused and on the road again at last) : swapped 4T65, cammed and intercooled among other things
Best ET: 13.208
Best trap: 104.96mph

This is very educating! I appreciate all the information.
Yesterday, I ordered my scan gauge. I'll finally know how much boost I'm really getting, as well as how much KR (factory gauge always pegs 10 psi at WOT).

That said, and back to my original question, is there a "range" per se that works best? A ratio of some sort? (i.e 10-12 psi w/ 0 KR) Obviously each set up different based on the mods. As I add more mods to my car, I'd like to know where I should be to get the most out of my set up. If it helps, the next major mod I will do next summer will be SLP header exhaust. I know then, I could lower my pulley because I've opened up air flow. How much smaller is the burning question. I'm thinking 3.2, but what if 3.0 yields greater results? Would the "ideal" situation be to run 0 KR at the highest psi possible without overheating? Basically, I'm looking for a general rule of thumb that has proven best.

The scangauge won't tell you boost pressure. Only BCS duty cycle.

There is no IDEAL. As I stated above, boost PRESSURE means nothing. How well your engine flows means everything (cubic feet per minute). The Boost pressure reading is only useful as an indication that related components are functioning.

You're better off increasing timing (PCM or custom tune) than decreasing pulley size.

_________________

Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

All the sites selling the scan gauge says, "If the vehicle is broadcasting the parameter, the Interceptor will recognize this and make it available for display." One of the available parameters is "Manifold Pressure in PSI (Boost pressure for factory turbo/supercharger applications)."

Tell me more about BCS duty cycle. What is that?

I may be mistaken, as both mine (OBD1 for the Zilla and OBD1.5 for the SLEeper) display only BCS (boost control solenoid) duty cycle. 0% for idle, 100% for full throttle (full boost) and anything in between. Not actual pressure value, but my MAP sensor is only for a boost indication, and not used by the PCM like yours.

But it doesn't matter. Your boost PRESSURE means nothing more than mine, which means nothing. It's only an indication that the related components (SC, BCS, BCA, PCM, and drive belt) are operating correctly. Or if it drops from whatever nominal peak value, that there may be a boost/vacuum leak.

FLOW means everything. PRESSURE means you're not flowing it.

For instance, you run 7psi or so stock. You drop to a 3.5 pulley and it goes to 8.5psi. You install 1.9 rockers, and it DROPS to 7.5psi. You GAINED power because you're flowing more of it. The pressure indicated is the STORED pressure that COULDN'T flow through the motor.

Everyone here with a boost gauge and a supercharger should change their way of thinking. Boost pressure is UN-USED power. FLOW and TIMING are where the power is at.

_________________

Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

That definitely helps! Thanks!
A few more questions:
IF boost pressure is UN-USED power, then would the goal be to run 0 psi boost?

Does the scan gauge help us determine the FLOW?

When I bought my PCM from Intense, I ordered it with the timing tables advance 3 degrees at WOT. I heard that's not much.
This may take us way off topic, but what is the relationship for each degree advance on the timing?

0psi is atmosphereic pressure. You NEED some pressure in the manifold to FORCE the air into each cylinder as the intake valves open. The ideal amount is a subjective value based on temperature, atmoshpheric pressure, humidity, individual engine characteristics, and about a dozen other variables.

The idea is to run advanced timing (your PCM will do well there for awhile) and then pulley down to the point where you see 1-2 degrees of KR MAX. That tells you that you pushed it to the limit. This should be done in the WORST (hottest, most humid) conditions on a heat-soaked engine.

If you play with a pulley:

1. You better own a scantool.
2. You will be on top of your KR for the rest of your life. It's a price you pay, because different small variables can change it.

In the long run, you're better off running MAX possible timing (only possible if you have a tuner) and the smallest possible pulley WITHOUT KR after you max your timing advance. That's where the most power is, but it changes throughout the day with temperature, humidity, and all that other crap.

In other words, we can't possibly answer your question with a black or white, right or wrong, or a solid number. It's a dynamic situation that changes based on 12 or more variables throughout the day or your commute. You have to learn it, scan it, and live it to deal with it, understand it, and adapt to it.

There is no taming it or beating it.

_________________

Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

That's exactly what I was looking for! Some good ol' fashion veteran advice!
I should be getting my scan gauge tomorrow and installing it this weekend.
Thank you!!!

Can you post a link to the scan gauge you are referring to?

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Thanks, Rich

The Black Pearl-94 SSEi stock 150,000miles
MODS...Magnaflow Cat, Magnaflow F-body Muffler, 180*F T-stat, 2.5"pulley, Yella Terra 1.8" roller rockers, custom CAI box, 93'SSEi fuel pressure regulator(3.0BAR), Walbro HP fuel pump, reman Jasper trans, new front suspension

Aeroforce:
http://www.aeroforcetech.com/

Intense:
http://intense-racing.com/Merchant2/mer ... ry_Code=IE

3800 Performance:
http://www.3800performance.com/Merchant ... ct_Count=0

PFYC:
http://www.pfyc.com/pc/GN2110/GPGAU/Aer ... odels.html

It does not look like it is compatible with an OBD1 PCM. :(
I wonder if an adapter cable would make it work?
This would be good to track KR for me.(having a smaller pulley)

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Thanks, Rich

The Black Pearl-94 SSEi stock 150,000miles
MODS...Magnaflow Cat, Magnaflow F-body Muffler, 180*F T-stat, 2.5"pulley, Yella Terra 1.8" roller rockers, custom CAI box, 93'SSEi fuel pressure regulator(3.0BAR), Walbro HP fuel pump, reman Jasper trans, new front suspension

Pearl, if you have a 2.5" pulley on that car and no scantool, take the pulley off.

The aeroforce is not advertised to work with the 94/95, but i've long suspected that it might. Our plan is to try a test-fit at WCBF.

_________________

Click here for mod list for both cars
93 SSEi, 95 SLE (supercharged) 97 Buick LeSabre Limited
PontiacDad at WCBF '04: Cruise control? That's like surrendering!
Comprehensive guide to troubleshooting, rebuilding, and modifying Eaton Superchargers

Just to verify the question above, the Aeroforce gauge for my '99 SSEi gives me PSI, NOT duty cycle.

To be honest I have no idea what PSI I'm running right now because I have KR displayed all the time and trans temp on 95% of the time when I'm going WOT.

_________________

2012 Subaru WRX
Previously Owned 1997 40th SLE - Bonneville #1
Previously Owned 1999 SSEi

what version do you have? I have 2.5 and I think it shows duty cycle. (I'll have to confirm later today)

I'm not sure exactly, but I got it new at the end of 2006 right when they started to display MPG and they came with 2 extra analog inputs. The only thing close to duty cycle it displays is injector pulse width in milliseconds.

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2012 Subaru WRX
Previously Owned 1997 40th SLE - Bonneville #1
Previously Owned 1999 SSEi