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Old 06-06-2002, 11:05 AM   #1
Impreza Rider
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Join Date: Jan 2000
Chapter/Region: MAIC
Location: Ashburn, Va
Vehicle:
2003 Legacy L wagon
2009 Kawasaki C14

Default Boost and valve float?

How much boost are you able to run on stock heads and prevent valve float?

I'm currently running 5 pounds, and will up to 7 when I get my boost controller. The stock injectors will be maxed out at this point most likely (I'm at about 75-80% injector duty cycle @ 6400 rpm with 5 psi according to the Link). When I upgrade injectors, I plan to run 10 pounds of boost. I currently have my rev limit set at 6500rpm, but was wondering if I would have trouble with valve float at those boost levels with the stock heads.

Thanks for any input
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Old 06-06-2002, 11:57 AM   #2
kastle
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Once I get a tranny back in I'll be running the same type of setup.... 10psi, 6500RPM redline... I don't think there will be a problem,.... I was able to run 15psi @ 6250RPM's in the RS-TT setup with no realy problems... Mind you that was not on purpose.
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Old 06-06-2002, 05:03 PM   #3
Graham
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Impeza Rider, I don't mean to cut in to your post, but on the little Legacy turbo don't you think you'll be far beyond the max efficiency at 10 psi?

Also, I am curious if the car even pulls at 6500 RPM?

All I know about our valve springs is that they are good for a pretty high redline, though I don't know how they do against boost.

Graham
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Old 06-06-2002, 06:54 PM   #4
Impreza Rider
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I've seen some legacy guys running about 13 with the stock turbo. But I also will probably upgrade the compressor wheel if I feel like getting dirty. I've never been able to find a compressor map for it either, so we'll find out. There's a local guy running 12 pounds in his RS, but he does have the upgraded wheel.

I know that the stock valvetrain will start to float at about 7k...I just wasn't sure how much of an effect the turbo had pushing on the back of those valves.

oh...and the car pulls decently up to my redline. Not as well as it could with say Cobb cams though The main reason for picking that redline is because of auto-x...I don't like having to shift into third. I've had to either shift, or ride the limiter at a couple events...both ways I lost time. Hopefully having a slighty higher limit will help.
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Old 06-07-2002, 11:46 AM   #5
Graham
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I'm with you on autocross, shifting to third could definetly be avoided with just a slightly higher shift point.

Upgraded compressor wheel? Would you mind sharing where those can be bought? It would sure be a nice alternative to buying a new turbo.


Quote:
I've never been able to find a compressor map for it either, so we'll find out. There's a local guy running 12 pounds in his RS, but he does have the upgraded wheel.
I would love to see some compressor maps as well. 12 psi on the Legacy turbo? Thats quite a bit, though I wonder how much of a difference the upraded wheel makes?


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Old 06-07-2002, 12:01 PM   #6
Impreza Rider
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2009 Kawasaki C14

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Quote:
Originally posted by Graham

Upgraded compressor wheel? Would you mind sharing where those can be bought? It would sure be a nice alternative to buying a new turbo.
The turbo on the 86-89? Thunderbird turbo coupe is an IHI RBH5, but it has a higher compression wheel in it, so it will more more air. I'll probably get one from a junkyard and pull the wheel out of it. Then get some help installing it into my turbo. We'll see...
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