Date:         Thu, 20 Dec 2001 09:23:48 -0800
Reply-To:     mark drillock <drillock@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         mark drillock <drillock@EARTHLINK.NET>
Subject:      Re: Boston Bobs day at the dyno
Comments: To: Robert Donalds <bostneng@FCL-US.NET>
Content-Type: text/plain; charset=us-ascii

Bob, I don't think the visegrip method of adjusting the fuel pressure
necessarily raised the pressure at all at the high engine loads tested
by the dyno. The fuel pressure regulator is dynamic while the clamping
method is static. At high engine load there is less fuel in the return
line. Making the return line smaller by clamping only affects the
pressure to the degree that the return flow exceeds the new restriction.
If you set it at 35 when the return flow was maximum then the system
pressure was likely lower at the reduced return flows under high engine
load. Did you monitor the fuel pressure during the dyno run? There may
be a fuel supply rate shortfall in the fuel rail rather than a problem
with the injection system. (fuel filter, fuel pump?) This could also
help explain why the seat of the pants said you had more power as the
flow/pressure may have been sufficient at lower engine loads for the
injection system to work normally while driving.

Mark


Robert Donalds wrote:
>
> fellow learkers and so forth mores
>
> I spent the day testing vanagons on a chassis dyno with mixed results. The truth of the matter is that everything I thought I observed by the seat of the pants method was wrong. First on the dyno was the big valve engine in my 84 camper first run to warm the engine up made 50 hp at 3000 and a max reading of 77 hp at 4600 RPM thats a nice start but the air fuel ratio was a little lean second run fully warmed up 3000 RPM 41 hp and max power of 70 hp at 4500 RPM  the fuel air ratio is now off the scale its way to lean. Thats huge loss of power amost 25 % at 3000 RPM from the one thing that nobody seems to check air fuel ratio.  OK the day is young so we can take this in stride and I am sure this engine has the potental to make alot more power because the 20% increase in air flow threwout the valves lift . after checking the fuel pressure we desided temporarily boost the pressure used the adjustment screw on a pair of vise grips clamped to the return line and we got the gauge to read a
> steady 35 pds under load. (dont try this at home) and we did another run no differance in power or the air fuel ratio. OK I now have a problem that is more than I want to sort out on the $100 an hour chassis dyno and its time to move on to the next van. I brought out the family van blue bell with a stock 2.1engine it a stock 1984 7 passenger plan Jane quick as a bunnie and Im sure its not as fast or as powerful as my race camper. First run bang  3000 RPM 55 hp max hp of 74 hp at 4600 RPM air fuel ratio right on the money mid 13s same thing second try. thats not what I exspected but I keep repeting the things I am learning so far #1 fuel air ratio is VERY important #2 the meter is running when you are on the dyno. At this point the cars are stacking up behind me waiting to have a go on the dyno, turbo jettas and new beetles. Home I go to get the next van and when I pull back into the yard where they are testing and they signal me to get the van on the dyno for my next test...........