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Old 08-28-2007, 08:29 PM   #1
system60
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Default Might be a dumb question about Tq curves

Is there any explanation why pretty much every Subaru dyno i've seen there is always a tq peak and it starts dropping down.(I can understand this w/ a small turbo but even the graph on here for TopSpeed w/ a 4094 it does it) While there will eventually be a plateau in the hp curve ?

Just about any other car its the opposite. Its almost like if you flip over a subaru dyno and mark the tq as hp and hp as tq is what most dynos for other cars look like.
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Old 08-28-2007, 11:39 PM   #2
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simply put, volumetric efficiencies start falling off...as boost is a big drive in this department generally peak boost will see the peak VE... VE= volume actual/ volume theoretical...
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Old 08-29-2007, 12:05 AM   #3
BlackEyeII
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Default Cams...

I think cams (VE I know), but the profile design plays a big factor in this. Stock cams generally breath well in the low/mid range it seems.
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Old 08-29-2007, 12:19 AM   #4
gold rush
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The tq curve on my version 8 ej207 is pretty flat, and not the typical subaru peak. It stays pretty much flat from 4900 to 7000 rpm. Must have to do with how the head was designed to flow, JDM ver 8 heads have bigger ports than USDM heads.
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Old 08-29-2007, 01:50 AM   #5
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Quote:
Originally Posted by gold rush View Post
The tq curve on my version 8 ej207 is pretty flat, and not the typical subaru peak. It stays pretty much flat from 4900 to 7000 rpm. Must have to do with how the head was designed to flow, JDM ver 8 heads have bigger ports than USDM heads.
well, that, the rod ratio, equal length manifold and a twinscroll turbo.
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Old 08-29-2007, 05:51 PM   #6
ride5000
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Quote:
Originally Posted by system60 View Post
Is there any explanation why pretty much every Subaru dyno i've seen there is always a tq peak and it starts dropping down.(I can understand this w/ a small turbo but even the graph on here for TopSpeed w/ a 4094 it does it) While there will eventually be a plateau in the hp curve ?

Just about any other car its the opposite. Its almost like if you flip over a subaru dyno and mark the tq as hp and hp as tq is what most dynos for other cars look like.
because of the horizintally opposed layout, the intake and exhaust runner lengths are longer than those seen in any other small displacement, high revving, inline engine.

as a result the VE peak of a subaru engine is relatively low in the RPM range with respect to redline, and that makes the dropoff of torque more noticeable when plotted out all the way up.
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