Date: Thu, 30 Aug 2001 14:01:43 EDT
Reply-To: FrankGRUN@AOL.COM
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Frank Grunthaner <FrankGRUN@AOL.COM>
Subject: Re: full throttle switch boost - HOW TO?
Content-Type: text/plain; charset="US-ASCII"
Gentlemen,
I feel I must comment here. There are no excess, unnecessary frivolous
switches or wires or sensors in any factory electronic fuel management
installation. Includes European, Japanese and American models. The full
throttle switch will trigger the ECU to generate an open loop operation
(bypasses the O2 sensor input) and goes to a preprogrammed fuel injector duty
cycle designed to be on the richer side of cruise.
The effect on the operation of the vehicle will depend on just how much
reserve power is available. If you are already drawing as much power as the
engine can make, you will not get any additional acceleration. By going to a
richer A/F ratio, the actual combustion chamber peak temperatures will be
reduced (minimizing the tendency to detonation, piston evaporation, ring
seizure and valve surface burning.
If you have 5 hp in reserve left to tap and you are already at a significant
velocity, it might take 10 hp to increase your speed by even 5 mph. Your tail
end sensor may not be sensitive enough to tell the difference, but the
thermal benefits still apply.
If the engine rpm is such that you are past the well past the torque maximum,
but still have a modest power reserve, the engine will accelerate slowly at
best. Cooling effects still apply.
If you have inadvertently disabled the oxygen sensor sending the ECU into an
open loop mode, there will also be only a modest effect. This is because the
ECU map gives a fuel injector duty cycle (results in an A/F ratio) that is a
function of the air flow signal, the temperature and the RPM. The full
throttle enrichment is probably only 5 to 12 percent higher than the open
loop map at that RPM.
The key design point for Bosch in all of these ECU systems is to guard
against the full lean condition which will take the engine down. Only
aftermarket tuners are concerned with full throttle tuning for maximum power.
To summarize, you can run a Renault Dauphine on a slurry of vegetable oil and
methanol for a short while, but why? Reconnect the full throttle switch (and
the oxygen sensors) or be prepared to support the fat lady songfest!
Frank Grunthaner
PS: "I did it and nothing bad happened" or "I did it and it worked better"
are anecdotal observations. Not scientific or technical observations.
Engineering and measurements combined with statistics are good! The latter
approach is why Bosch pays substantial salaries to a battery of serious
staffers to maintain market share and enhance their patent position!
