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Old 01-30-2009, 07:28 PM   #117 (permalink)
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Originally Posted by some_other_dave View Post
My understanding is quite incomplete, but I believe that the two are related, but not identical. BMEP is "Brake Mean Effective Pressure", I think, and is a measurement of the pressures inside the cylinder. More cylinder pressure typically means more torque from a given motor under a given set of operating conditions, but I think there are a bunch of other factors that also have some sort of influence on the one figure or the other.

So a direct scale overlay is probably "close enough" for our purposes, even though it may be technically inaccurate.

Some_other_dave, that's my same basic understanding of BMEP.

When I created the overlay, I figured it was "close enough" to be useful, but felt it was probably well short of "best guess, reasonable approximation." After looking at it a while longer, I decided a Saturn 1.9L would probably have fewer city driving cycle samples in the sweet spot (????), so I scaled vertical down by and additional 10%.

Revised aspect of Generic BSFC map using BMEP = 150.8 x TORQUE (lb-ft) / DISPLACEMENT (ci) as a guide to matching BMEP and Torque scales of the Generic and Saturn maps.

Also made various changes to attempt to improve visual clarity including:
  • Improved contrast.
  • Where applicable changed SFC labels to reflect both SI and US units of measure.
  • SFC labels from the Generic Map are now in italics
  • SFC labels from the Saturn Map are now in bold
  • SFC labels on both maps now appear above and to the left of the lines they reference.

Last edited by TestDrive; 01-31-2009 at 11:19 PM.. Reason: Image is now v2.1
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