Toyota Supra twin turbo and water injection.

[Greg Hermann]

>Provided of course that the exhaust gas temperature remains the same and you
>are correcting to stoich.  If you are biasing toward rich - which under load
>most are - you will find that the output is temperature sensitive and your
>mixture will be off.
>
>A .8 equivalence ratio ( about 12.~ to 1 ) is ~1.0 volts at 500c exhaust but
>only ~.875 volts at 900c.  At 900c the transition from stoic voltage is about
>650 mv but at 500c its all the way up to 850+mv.
>
>Adding water or alcohol will lower the combustion and generally the exhaust
>temperature.  If you are uncompensated for EGT, this will mean for the same
>output of the sensor, the mixture will be leaner.
>
>Reference: Internal Combustion Engine Fundamentals
>John B. Heywood - Director Sloan Automotive Laboratory MIT
>ISBN 0-07-028637-x
>
>Virtually all O2 sensors appear to be uncompensated for temperature with the
>heater bringing them somewhere in the "warm" region.  For the manufacturer
>this is not a problem as they simple use them as a stoic switch.

Bob is absolutely correct here about what will happen to O2 sensor output.
He is also correct about what will happen to EGT's. Sorry--I happen to
think it is less than smart to use a standard HEGO sensor to read anything
BUT stoich, as a switch, so did not cover the point in my first post!
Please excuse me for not stating my assumptions more clearly!!!

ALSO--BEWARE--Bob's cautions as regards sensor output apply just as much to
wide band UEGO sensors as they do to HEGO sensors. If you have a wide band
, UEGO type O2 sensor which has not been properly and completely calibrated
for changes in EGT , as well as for changes in exhaust back-pressure at the
sensor location, you will get BOGUS mixture readings!

Unless you have a fully, properly, accurately calibrated UEGO sensor, plug
readings and high grade dyno flow instrumentation are the ONLY two ways to
reliably determine mixture strength (other than stoich)!!!!

Just to be really clear about it--a HEGO sensor will detect a stoich
mixture, regardless of fuel type or any mixture of fuel types, and
regardless of EGT or pressure. This is true because all a HEGO sensor
really does is detect the presence or absence of oxygen in the exhaust gas
stream. Gas temp and pressure will certainly have an effect on the rate of
sensor response to changes in gas content, though.

Regards,

Greg
>
>>Date: Sat, 3 Apr 1999 16:14:27 -0700
>>From: bearbvd at sni.net (Greg Hermann)
>>Subject: Re: Toyota Supra twin turbo and water injection.
>>
>>>In article <4.1.19990403143820.00951540 at mail.lig.bellsouth.net>, David A.
>>>Cooley apparently wrote:
>>>
>>>> How about substituting Methanol or Ethanol for the water... higher heat of
>>>> vaporization (cools better as it evaporates) Plus it supplies additional
>>>> fuel to the engine *AND* increases effective octane of the cylinder
>>>> charge... Pretty good gains to be seen here if it's metered right!
>>>
>>>That is pretty common over here in the UK.I do not know if such additives
>>>would be "liked" by the Lambda sensor though? Anyone ?
>>
>>No problem there--fact is, the sensor will read the true stoich point,
>>despite the new fuel.
>>
>>Greg
>
>
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