Stock 7m-gte Vaccum in In/Hg

AllStreet

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Feb 3, 2008
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Michigan
What is the stock Vaccum on the 7m-gte '91 supra turbo, does different turbo's effect the vaccum. Thanks.

I am trying to decide what Spring I need for a my tail wastegate
 

Dan_Gyoba

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Aug 9, 2007
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That all depends, now doesn't it?

In the manifold, at idle, mine pulls about 15in Hg vacuum. During decel, 20-21uin Hg according to my autometer boost gauge. Mind you, these are pretty much normal values for about any gasoline engine.

If you want to know about vacuum before the turbo, that'll vary by turbo, air filter (and how clean it is), RPM etc.

If you want to know about vacuum in the IC piping, there's no point. If there's vacuum in the IC piping, then you want the BOV closed, period.
 

starscream5000

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Aug 23, 2006
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The turbo won't affect how much inHg vacuum the motor pulls, but different cams will, along with how tight or how loose the piston rings are, valve seals, etc.

You need to measure how much vacuum your motor pulls, then refer to Tial's website for correct spring selection.

On a freshly redone motor all going to TSRM spec, you would need an 11psi spring, but if you're motor's getting worn down, you may have to move down to a 9psi spring. A lot of people on here have used both and seen some compressor surge with the 11 psi and my guess would be that their motor no longer pulls enough vacuum to warant the use of that spring. When they've switched springs they have, for the most part, reported the compressor surge to have nearly dissapeared. I would guess this is due to the vacuum being pulled by the motor being in spec for the 9psi spring.
 

Dan_Gyoba

Turbo Swapper
Aug 9, 2007
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Just re-checked mine, and according to the gauge, it's closer to 17 lbs at idle, and I'm 2500 ft above sea level, so that's normal according to Supracentral's link.

Decel, it about pegs the lower reading of the gauge.

A vacuum gauge (particularly one that you just connect in the engine bay) is a cheap diagnostic tool anyway.