At 08:32 AM 9/6/02 -0400, you wrote:
>I saw this on eBay. I'm not interested but I was wondering
>if anyone had used one? Just curious how they work.
>Bill White
Hi Bill.
I have never used one but I did a bit of research on it a year
or so ago.
The "Venom 400" marketed by Python Injection, Inc. and claims
to alter closed loop fuel and spark response by replacing or
modifying the voltage signals into the powertrain control module
(PCM) from the manifold absolute pressure (MAP) and throttle
position (TPS) sensors. Since the PCM uses input from the MAP
and TPS sensors during closed loop operation to determine an
appropriate fuel response, their logic behind this attempt is to trick
the PCM into thinking that the throttle is open more than it actually
is so that additional fuel will be added to the mixture. And since
a mixture slightly richer than stoichiometric is generally best for
producing peak power, the additional fuel should create some
extra power (albeit far from the 25% increase that they claim.)
However, it is important to remember that MAP and TPS inputs
only affect PCM decisions during partial throttle driving. Once MAP
and TPS signals reach voltage levels that indicate full-throttle,
the PCM begins ignoring these input signals and resorts to open
loop operation – at which point, additional voltage from MAP and TPS
sensors will not affect fuel response. In other words, the Venom 400
claims to function only under partial throttle conditions and the makers
do not deny this.
They even publish dynamometer testing results at their website
(http://www.venom-performance.com/v400/dynos.html) that show
power gains as a function of throttle position. If you look closely,
you will notice that the Venom 400 power curve matches the stock
power curve at 25% and 100% throttle openings. And, of course,
on both curves, the point of maximum power occurs at a 100%
throttle opening. But at all partial throttle openings between these
points, they indicate a substantial increase in power by using the
Venom 400.
Specifically, at 40% throttle opening with the Venom 400, as much
power is indicated as was produced at 60% throttle opening on the
stock curve. And at 80% throttle opening with the Venom 400, as
much power is indicated as at 90% throttle opening on the stock curve.
At full throttle (100% throttle opening,) the venom curve matches
the stock curve – which makes sense, since the Venom only claims
to function during partial throttle operation.
Those of you who have read the previous tech articles on fuel delivery
are probably laughing by now. This is because you know that the block
learn feature of closed loop operation uses input from the exhaust gas
oxygen content sensor to modify the PCM's response to any given set
of input signals from the MAP and TPS sensors. So even if the Venom 400
were successful in altering the MAP and TPS inputs, the resulting
richer-than-stoichiometric mixture would be detected by the oxygen sensor.
And the block learn feature of closed loop operation would force the PCM
to adjust its response to the new MAP and TPS signals until stoichiometric
ratios were restored. Thus, by altering only MAP and TPS signals, the
Venom 400 would have no permanent effect on closed loop fuel mixtures.
You can accomplish the same thing for free by pushing harder on the
accelerator pedal.
I came across this review shortly after receiving a glowing report on the
400 in an email from an IndyRam owner running a SC.
I tend to agree with the above review.
Bob
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