Re: Lambda Testing by SM

["Scott Mo." <scottmo@teleport.com>]

QSHIPQ@aol.com wrote:
> Given a high CO content, high HC and High CO2, I would still question
> where we are getting combustion.  

The graph indicates that "typically" the HC levels go up as the Air/Fuel
Ratio is lowered and as the CO% goes up. I do not know what engine or
fuel system was used but I suspect there are circumstances that can
affect the actual values measured. 

The test results I logged on the modified 20V engines, and on my car,
indicate the unburned Hydrocarbon (HC) in Parts Per Million (PPM) is
very, very low (60-80 PPM) even though the CO% was very high at 7-9.9%.
If the HC was really high at sustained full throttle conditions, like
above 1000 PPM, I would also be concerned as to long term reliability
and the life of the cat converter. 

At idle on my car the "pre-cat" HC is 170-200 PPM, the Carbon dioxide
(CO2) is 14.2 %, the Carbon Monoxide (CO) is 0.6%, the O2 is 1.2%. 

If you short out one of the spark plug wires to ground, the HC reading
pegs the meter at 9999 PPM, the CO2 is at 11.7%, the CO at 1.8%, O2
rises to 3.7% due to the HC and O2 passing through the cylinder
unaffected.

QSHIPQ@aol.com wrote:
>Long term HC content has bad effects, regardless of FI or carbs.

Yes, but in the  case of the three modified Audi Turbo engines I tested,
we are not seeing high HC levels at sustained WOT operation.

QSHIPQ@aol.com wrote:
>  Fuel is either burned or not burned, when it's not we have a
> myriad of potential problems.  Hot turbochargers and exhaust 
>manifolds might be "correcting" that, but how?  By burning the unspent >fuel?  Doesn't sound like good long term news for the O2. 

Well the exhaust readings are coming from the same area the O2 sensor is
mounted, so where-ever the mixture is burning, it is happening before
that point. It certainly could be burning in the combustion chamber
given a good design that promotes an efficient flame front.

QSHIPQ@aol.com wrote:
>  The fact that the tuners are using 11:1 fuel ratios is intriging to >me, cuz the ONLY thing we can surmise is reduced manifold temps. 

There could also be some NOx considerations being handled with the extra
fuel to keep the combustion chamber temps lower and reduce NOx
formulation. Unfortunately, I don't have the newer 5 gas analyzer which
can also read NOx output directly. :-(

The Do It Yourself (DIY) fuel injection list has some interesting
information from a couple of high tech tuners, Jim Conforti (Bonneville
Motor Werks) on BMW's and Todd Knighton of Protomotive for Porsche
vehicles. If you search the archives for either of these names, you can
dig up a lot of great information, IMHO.  Go to

http://efi332.eng.ohio-state.edu/diy_efi/asearch.html

>From this DIY list, Todd Knighton of Protomotive posted the following on
Air/Fuel ratio adjustment:

August 27, 1996
"When we calibrate engines on the engine dyno, we typically use the dyno
for a load device only. We load the engine to a specific load/rpm site
and calibrate the engine for the air/fuel ratio desired, not the one
that makes peak power, but the one that over much pain and aggravation
has produced the best reliability/performance/economy/in other words
compromise over time. Then the timing is adjusted to its optimal value,
again for no knocking nor misfire because of rotor phasing, etc.
Sometimes timing is checked for optimal power, but typically fuel is
not."

 From Sept 26, 1996:

"Try 14.7-15 or even up into the 16's if your engine can handle it, it
depends on combustion chambers and flame propogation. But at light
throttle run as lean as possible with no misfire. Go to 12.8 to 13.3
(pump fuel numbers) for max power and torque normally aspirated. 

Boosted, lower the air/fuel proportionately. We air cooleds have to run
down in the 11.4-11.6 to 1 range at 20psi with very good intercooling to
maintain peak power and reliability. We get slightly better power at
11.8-12.0 to 1 but the combustion chambers get too hot. Water cooled's
would probably be happy at 11.8-12.0 to 1." End quote.

QSHIPQ@aol.com wrote:
>Given that these values you posted are based on the old 'fixed duty
> cycle'  technique of WOT (and so really is the S4) I sure would sure >want to make doubly positive I've properly adjusted my WOT switch.  And >in a early MC car, that's not even close to WOT.

Yes, correct operation of the stock fuel/ECU system components is
critical BEFORE you start playing with ECU/Engine mods. I find this area
is the most often overlooked way to make a car perform. People raise the
boost on a high mileage engine with broken/defective components and
can't figure out why the car runs like crap.

QSHIPQ@aol.com wrote: 
> Interesting to note too, Scott is that the Bosch manuals refer to the
> .85-.90 target for WOT operation for maximum power. 

I suspect that this number is a typical target, but that it does not fit
every engine, every combustion chamber design, every cam shaft profile,
every intake/fuel system. The fact that the Audi 20V engines are capable
of surviving running boost levels of 18-19psi with 9:3 to 1 compression
ratios and using pump Unleaded premium indicates more complex
interactions handled by basic rule of thumb approximations.

> Hmmm, if I insert an EGT temp sensor to do the "vary according to >engine temp"  would I be accomplishing a better rich mixture and >transition response?

I suspect that Audi on the new S4 uses a canned map to set WOT fuel
conditions and then monitors the exhaust temp to "correct" a problem
that may occur running lean as the exhaust temp starts to climb out of
sight or to do long term adaptive corrections. The standard O2 sensor is
used for the same adaptation under cruise conditions. As was indicated
by the tests I did, the old systems running at 6.5% CO at WOT are likely
not producing the exhaust gas CO levels the EPA would like to have on
future vehicles.

> Certainly better than how audi does it now?  Would a better O2 do the >same thing?

Certainly couldn't hurt...

HTH
-- 
Scott Mo.
1989 200TQ
1988 5000TQ
1966 VW Beetle
http://www.teleport.com/~scottmo