16v has more power when motor is cold?

[treed2@u.washington.edu (T. Reed)]

Allyn,

>     the resistor-in-line thing might backfire on you. o2 sensors make voltage,
> but are incapable of producing any kind of decent current. that is why you have
> to use a digital meter to measure o2 sensor current (analog meter loads the
> sensor output down, and the voltage drops because of it). the cis computer has
> an extremely high input impedance for its o2 sensor input, meaning that the
> current going from the o2 sensor to the cis box is so small that it probably
> wont even register on a digital meter (we're talking micro-amps here). with all
> of this going on, trying to drop the voltage received with series resistance
> would probably be more trouble than its worth.

Probably.. I made some assumptions about the electrical characteristics of
oxygen sensors. I was thinking they would operate on the order of
10 milliamps - probably because thats what I'm used to from setting the
DPR current..

If the current produced by the o2 sensor and the impedence of the ecu were
either constant or predictable, it would be doable.. but I would still
need a very small resistance.

>     what would work would be a simple op-amp circuit between the o2 sensor and
> the cis box. you could make the gain adjustable, letting you dial-in just how
> much % boost in fuel you want. even easier would be to skip that part of the

Definitely the best way to go about it, but I was trying to keep it
simple.. you'd need a voltage regulator and all that crap too to power the
op amp.

> loop and and mess with the  resistance of the coolant temp sensor. This is
> already done in the way of 'power modules' and the like, and should work for
> your application.

Maybe, but I don't know exactly how the ecu responds to temperature
changes. (I could probably buy one of those CIS-E books and find out..
Hmmmm.) I don't know if the mixture varies continuously based on the
resistance of the sensor (in which case it would work), or whether the
ecu has only piecewise ranges of operation (cold/warm/hot), or whether it
is only used to determine when the engine is warmed up enough  to come out
of open loop and for the o2 sensor to be taken in to account.

The first case would be ideal because the type of control I'm looking for
is something like "dump 5% more fuel in" rather than "dump 20-60% more
fuel in depending on what the ambient and engine temperatures are". I
still want to stay as close to stoich as possible, just err a little on
the rich side.

> before doing any of this, i would test the coolant temp sensor, o2 sensor, coil,
> and dpr, as any of those things can cause the same symptoms.

Well the CTS has been checked many times at many different temps and it
has always been within spec. The oxygen sensor seems to be operating fine
- I get fluctuating voltages from .3 to .9 just sitting at idle, IIRC. My
coil primary is a little out of spec - 1 ohm instead of 0.6 to 0.8, but
everything else is fine. The DPR can't really be tested as I understand
it.. but mine seems to be working okay. If I unplug it while the engine
is running it sure has a fit!

> last note: you'd be surprised just how much of a power difference can come from
> warmer intake air. you'd also be surprised about just how good the intake is at
> dumping the cyninder head heat into the intake air stream.

Yeah, I guess so!

I've always thought the 16v intake was a bit stupid for being so big and
having such long runners.. its like blowing air over a giant heat sink.
I've sometimes wondered if this is why people with carbs or seperate
throttle bodies get such big power gains - the simple fact that the air
isn't getting heated up in the intake so much.

And then theres that exhaust manifold "pre heater" thing.. don't even get
me started!!

> HTH
> Al

Thanks for your ideas..

-Toby