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How much boost can I run? 

 

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 Post subject: How much boost can I run?
Posted: Thu Jul 26, 2007 10:56 pm 
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Gday all,

I have a stroked, balanced, forged 383 clevo and Im at the stage of decking the block. We have measured it up and I can have anything from 8.6 to 9.9 CR. Im thinking about 8.9 - 9.0.

I have a powerdyne that I have upgraded the belt and bearings to handle 60 000 internal revs instead of the usual 36 000 stock, so it will make about 12+ PSI if I gear it up.

Just after a few opinions on what boost I can expect to run with this kind of set up before detonation sets in. Im looking at 8pound, does this sound about right?

Cheers,

Matt

 

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Posted: Thu Jul 26, 2007 11:18 pm 
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I know I asked nearly the same thing only a little while ago bit the CR has changed since then and the intercooler idea is out the window for now. I wanted a little more CR to up performance lower in the rev range.

 

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Posted: Fri Jul 27, 2007 1:23 am 
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8psi Seems about right.

To be able to get 12psi out of a powerdyne is one thing, but to get it in the volume for the 383 requires is a big ask.

Reliably 8psi on around 9-9.5 compression is ideal. Powerdynes are known to be air heaters when trying to boost em over 10psi. And being a sealed unit too they can wear a fair bit. If you want it to boost up a little earlier a smaller pulley would help, but at the same time if you are revving it out past 5.5-6 then generally the speed that the internals are subjected to will great increase the wear.

I'd be starting between 8 pounds and trying to find a good trade off point.

 

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Posted: Fri Jul 27, 2007 1:05 pm 
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Thanks, I am shimming the impeller and venting the case for a little more cooling. Also using 450 deg grease on the high speed bearings instead of the std 250deg. From what Iv heard it should put out atleast the 8psi I want, all day long with no complaints.

 

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Posted: Sun Jul 29, 2007 12:42 am 
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If you put a 30mm restrictor on inlet you'll be able to reliably run 10 Lb easy....
Imo the blower is alittle small...

 

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Posted: Sun Jul 29, 2007 11:28 pm 
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Thanks. I was thinking of playing with the intake piping a little before getting it welded up. I would have bought a vortech if I had've known this was a BD11a and not the gear driven unit...ebay...pfffft

From what I have heard from the states the mods I am doing will give me 8psi no worries. Thats all Im after for the moment. If I want more in the future I will be getting a vortech and having to lower my CR.

I found this interesting...dont think I will be doing it though.

http://cgi.ebay.com/ebaymotors/Super-Po ... 0134703843

I'll gear it up and see what kind of boost I can get out of it just for interests sake, but I only plan to use 8psi. I'll watch the intake temp to see when it starts to heat up the charge too much.

Wish I could find a main/crank 6 rig/groove pulley that is bigger than 6"...

 

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