Date:         Wed, 31 Oct 2001 16:44:52 -0800
Reply-To:     Warren Chapman <warren8@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Warren Chapman <warren8@EARTHLINK.NET>
Subject:      On Engine Efficiency, Comparing I4s, WBs and Subies
Content-Type: multipart/alternative;


Frank,
 
Your post is very interesting, although  I need to read your explanation of BMEP more carefully as I must admit, my non-engineering type brain doesn't quite comprehend the significance of the single number for BMEP and just what it compares.

Does this mean the most heat derived from a given amount of fuel (the same fuel??.)

I did notice some mistakes, however, in your representations of the various Subaru 2.5L engines that, in the interest of posting accurate information to the list, you might wish to correct.  Not sure if this moves their various placement up or down in your chart ....but regardless... they should be accurate. 
 
According to the info I'm able to find so far,....ONLY  the 96 model year Subaru 2.5L develops its max torque at 2800 rpm.   This engine, a DOHC version requiring premium fuel was replaced in 97 with a SOHC version using regular fuel which develops its peak torque higher in the rev range.
 
According to Subaru, the 97-98 2.5L (SOHC) produced its maximum torque of 162ft.lbs at 4000rpm (rather than at 2800 rpm).
 
In 1999 Subaru introduced their so-called "Phase II" engines (2.2L and 2.5L) which they touted as having much improved torque curves throughout the rpm range over previous years.  The published info on the 1999-2001 2.5L is 166ft.lbs at 4000rpm, which doesn't look much different to me, but I assume the torque curve for these engines is flatter with higher torque kicking in at lower rpms.  I have not been able to find any charts to verify their claims.

Unfortunately, performance graphs are extremely hard to find.  Those of us with Subaru engines are not trying to keep any  secrets, as you suggest.....I just can't find any graphs.   The only one I have been able to find is the following one, which I believe to be for the 97-98 2.5L.  
 
http://www.protekperformance.com/rv7/engine/dyno_graph.htm

The source is unverified.  This graph (if correct) does show a rather attractive flat torgue line however ( for a normally aspirated gasoline engine) with torque at only 1200rpm reaching 140ft.lbs and maxing at 162 at 4000rpm, .......making most of the torque available in everyday driving situations.
 
Attached is the latest version of my best attempts to compile info on Subaru engines from 1990 to the present models.  The file is in Excel spreadsheet format.
 
I don't know what impact these figures have on your BMEP chart but I think the info, to be useful to the members of vanagon.com, should be accurate.  
 
I have no vested interest in pushing Subaru engines over any other choice.  I made my decision based on my own unscientific research using the "seat of my pants".  Which (as you say "nonlinear tail" (scientific instrument??)  had not yet  "desperately sensed the positive improvement stimulated by....a ......stunning infusion of cash "

I continue to suggest that, in addition to charts and data, prospective converters do the same "scientific investigation" and drive one of each of the conversions being considered.....then make a choice.  There are enough converted vans out there now that most should be able to do this.  For me the smoothness of the engine, near silent idle, and easy reving nature sold me and my "nonlinear tail".  Both of us were quite happy with our experience of moving down the road quite briskly (at all speeds) in a brick.
 
Also, regarding your posts to the SubaruVanagon list,........... you were not (as you stated in your post), ......."caught and excised by Warren as an unwelcome alien".........  I made a general post to the list...not to you specifically....that it is the stated policy of the list that the purpose of the list is to discuss the placement of Subaru engines into Vanagons.  All parties receive this notice upon signing up for the list, that..... discussions of other engines or vehicles will be allowed ...for a short while, ....but will eventually be referred to other lists which were created for discussions of those engines and vehicles and where the members will be interested in the info.  

As the moderator of the SubaruVanagon list, it is my goal to keep the list interesting and useful to the majority of the approximately 575 members.
 
Sincerely,
 
Warren Chapman
Moderator
SubaruVanagon Group

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