Ferrari Mailing List: Re: fuel mixture analysis

[Doug and Terri Anderson (dnt]

Hmmm – Wacko readings Michael

 

To get a good NOx figure – car has to be run under load.  Either driven around on the streets all hooked up to a little machine in the passenger seat OR on a dyne.  Was that done?  It will affect all the emission factors.

 

O2 – 12.27% Way way too much O2 left over.  Looking for 2% maybe.  Could be a vacuum leak somewhere and that includes the exhaust system – a cracked manifold or hole in a muffler which “sucks” raw air into the system.  It wont affect drivability.  O2 is NOT an emissions reading that will fail smog test.  O2 and CO2 are not testable pass fail emissions BUT they do help determing a good running SI (spark ignition) engine.

 

CO2 – 6.5%  A tad low.  13% would be good.  Rule of thumb is to add O2 + CO2 should = about 15.

 

HC at 498 is way high. Should be about 45 and well below 126 @ 15 mph and 50% load or 99 ppm at 25 mph @ 25% load  In short – yer a gross polluter.  HC is usually a product of ignition process.

 

CO - .87%   Should be about.16.  With so much O2 left over and a lot of fuel left over and a high HC – sort of indicative of bad ignition.  Not just plugs points and wires – too much fuel may be quenching flame front.  .87 is almost failure (that would be > 1.00) but a long way away from a GP at 2.42%

 

NOx – at 33 is way way low but I refer back to my original question = run under a load? OK – Lets say that was done.  NOx is a product of pressure (too much compression caused by carbon build up?  Engine design?), and heat (engine cooling is kaput – air in the lines, cyl head hot spots, radiator not ‘burped, etc).

 

The GTSi uses a system (a Bosch Constant Injection System – CSI) which is regulated by CO reading and fuel pressures.

 

Does your car have an O2 sensor and a three way cat or an EGR and an air pump and a little oxidizing cat?  All CO readings MUST be read BEFORE the cat.  Not sure what the CO should be for an 81 GTSi.  Typical CO% is 2.5 +/- 1 or if there is an O2 sensor, disconnect O2 and CO% would be 0.4 – 0.8.

 

Um, how is the drivability?  No hesitation?  Fuel mileage? (Ferrari – ah ah ah)

 

Oh – well – just my 2 Greek drachmas – so you know how much its worth.

 

Onward

 

DOUG

 

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From: Michel Savard [mailto:mysavard [at] videotron.ca]
Sent: Thursday, November 03, 2011 2:18 PM
To: DOUG
Cc: The FerrariList
Subject: [Ferrari] fuel mixture analysis

 

1981 308 GTSi: I had a fuel mixture done on my car and the mechanic even printed a report of it from his little machine. I took it and left without asking him what this was all about. Can anybody explain what this should tell me about my fuel mixture ?

 

02   %   12.27

co2   %   6.5

hc   ppm   498

co   %   0.87

cok   %   1.77

afr       30.20

nox   ppm   33

 

Michael Savard