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Old 04-04-2007, 11:11 AM   #1
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Default What kind of boost to expect?

Crank pulley is 7", supercharger pulley is 4 3/4"

Engine is a 2.5 liter, supercharger is an M62.

Yup.
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Old 04-04-2007, 11:17 AM   #2
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Moved to the Lounge. Your topics are not a typical application for us, and having this information in Forced Induction where a new inexperienced Bonneville owner may find it could prove confusing.

Your posts can be in Forced Induction only as long as they follow the 'norm' for us. Like replacing bearings. Application issues in how they relate to your drivetrain cannot remain there.

Do the math on your drive ratio. Then figure out how fast the SC will be spinning based on the RPM you normally shift at.

Then go to Eaton'* website and look at their data. That will get you in the ballpark, but there are still too many variables to put an accurate number on it.
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Old 04-04-2007, 03:46 PM   #3
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Meh, i'll just keep an eye on my boost gauge the first time i get on it.
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Old 04-07-2007, 12:31 AM   #4
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Aaand i make a whopping 2psi.

Cold start i make 4-5 and it hauls pretty nice, but after it warms up it hits 3 part throttle and 2 full. It'* slower than stock.
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Old 04-07-2007, 12:47 AM   #5
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Are you sure the wastegate fully closes at WOT?
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Old 04-07-2007, 11:30 AM   #6
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Quote:
Originally Posted by J Wikoff
Are you sure the wastegate fully closes at WOT?
It'* not a wastegate really, it'* a recirculating GReddy Type-*. It'* closed when little and no vacuum is applied.
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Old 04-07-2007, 12:38 PM   #7
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Where are you tapping off the boost? Between what and what? What does your manifold look like?
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Old 04-07-2007, 01:01 PM   #8
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That is a huge friggen pulley!!!! An M62 with that size pulley is not going to move much air. Even on a 2.5L.

Do you know what your volumetric efficiency is on that engine? 2 valve per cylinder or 4?

Assuming 100% volumetric efficiency your engine flows 265cfm.

Your pulley ratio is 1.47. So your blower is spinning 1.47 times what the engine is. So at 6krpms your blower is spinning ~8842rpm. Assuming your blower is 100% efficient it pushes 312cfm at 6krpms based on my calculations...which are prolly wrong cause I suck at math. But anyways, looks like you need a much smaller pulley to me. 312cfm = not a whole lot more than 265....

With a 3.5" pulley so your pulley ratio is 2.0 and your blower will be spinning 12k at 6krpms. Thats 423 cfm air at 6krpm. Which looks like ~8.7psi.

These are just rough estimates and I could've easily screwed something up along the way so take these with a grain of salt.
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Old 04-07-2007, 02:43 PM   #9
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Quote:
Originally Posted by dbtk2
That is a huge friggen pulley!!!! An M62 with that size pulley is not going to move much air. Even on a 2.5L.

Do you know what your volumetric efficiency is on that engine? 2 valve per cylinder or 4?

Assuming 100% volumetric efficiency your engine flows 265cfm.

Your pulley ratio is 1.47. So your blower is spinning 1.47 times what the engine is. So at 6krpms your blower is spinning ~8842rpm. Assuming your blower is 100% efficient it pushes 312cfm at 6krpms based on my calculations...which are prolly wrong cause I suck at math. But anyways, looks like you need a much smaller pulley to me. 312cfm = not a whole lot more than 265....

With a 3.5" pulley so your pulley ratio is 2.0 and your blower will be spinning 12k at 6krpms. Thats 423 cfm air at 6krpm. Which looks like ~8.7psi.

These are just rough estimates and I could've easily screwed something up along the way so take these with a grain of salt.
Thanks for those calculations, you sound dead on, that helps with my decision on a pulley size.

I'm tapping the only vacuum line my car has, T'd from the pressure regulator to my FMU, to my BOV, to my boost gauge.

My manifold looks like a stock manifold? I didn't make a custom one, i just routed piping to an adapter plate on the charger.
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Old 04-07-2007, 03:09 PM   #10
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So the wastegate on the SC is always closed and you control boost with a BOV.

My earlier math was based solely on engine displacement ratio, your blower speed at 5k, and stock max Series I boost. It looked like this:

x psi = 10 * (3.8/2.5) * (4.75/7*5000/11000)

...I think, but now that I run it again, I get 4.69 psi. Guess I screwed it up earlier.
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