2nd post, now done right: stochiometric?

[yankeedoodoo]

My zetec final mapping is finally underway. The ecu is pectel and I've had a continuing problem with the motor running too rich: 5 gallons= 50 miles---more or less. The very competent gent now doing it reports that this map is set @ 14 FA mixture, which I believe is about stochiometric. He is changing that # to 12 to see if the over-rich condition will be cured. My question is: If stochiometric is 13.8 or so, what other factors in the operation of the motor/ecu could deceive the ecu into running rich when it appears to be set about right? Or am I deceived and the problem is actually elsewhere? Thanks to any and all who can cure my ignorance or otherwise provide enlightenment/entertainment. Further, I rather hope that all of you are unable to answer before next week because you are @ Le Mans and I'm not. Yet another reason to envy life over there! Which reminds me that one of my inspirations to but a 7 came from driving north from Le Mans to Dieppe on the thursday before the race in 1999. I must have seen 50 or 60 in caravans of 5 or 10 over a couple of hours---including 2 that met with unintended disasters. You guys were having more fun than I was. sad.gif

[AMMO]

Yankeedoodoo

 

What system is being used to monitor the fuelling during mapping? CO meter on the rolling road or UEGO sensor in the exhaust linked to the Pectel's data logging facility?

 

12:1 is actually richer than 14:1. If temperature sensors are faulty or incorrectly calibrated the ECU can be fooled into running rich if it thinks that the engine is cold.

 

AMMO

[julians]

Leaky fuel tank ;-)

[Peter Carmichael]

This is more likely a cr*p advance map giving you the equivalent of a distributer with the vacuum advance disconnected and poor progression. If the fuel map measures up and it doesn't stumble then the problem is that the mixture is being burnt very inefficiently.

 

I would question whether the gent is that competent if he thinks moving to 12:1 will make it less rich.

 

Negotiate now - in case there is any doubt - to get the maps downloaded in readable, auditable form. You need to keep a hawk's eye on this guy because he is struggling and isn't as clued up as he is making out.

 

Peterid=teal>

253 BHP K-seriesteeth.gif, no gearboxbum.gifid=red>

[Alex Wong1697456877]

I once had a mapper tell refuse me the code to unlock my map. The map he did felt crap so I demanded the code and finally got it. When I compared the "new" map to the off the shelf get you started map from QED, about 5 numbers were different. That apparently took several hours of rolling road mapping and cost £180!!!

 

Good DTA mappers in my limited experience include QED (bench dyno) and John Noble (Rolling road).

 

Alex Wong

www.alexwong.net

www.slipstream-trackdays.co.uk

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[Roger King]

Stoichiometric fuel/air ratio is around 14.7:1. This is also known as Lambda 1.

 

A ratio of 12:1 is richer than stoichiometric.

 

Stoichiometric means that there is exactly the right amount of air (oxygen actually) to burn all the fuel present. In practice this never happens due to all sorts of inefficiencies in the process.

 

In reality, an engine usually needs to vary either side of stoichiometric to suit differing conditions. Under light cruise, the engine will run more efficiently with a weaker mixture; how weak depends on engine and fuel system design. For full power, you need nearer to 12:1. Stoichiometric is needed to keep catalytic converters operating efficiently (specifically the reduction catalyst to reduce oxides of nitrogen), so modern cars will run with this fuel/air ratio in the area where emission tests are carried out, even if they could be more efficient running weaker.

 

Mapping an engine will take somewhere between two hours and two months depending on how necessary it is to conform to legislation. Two hours could only be achieved by a very proficient operator mapping an engine of a type he is familiar with and not worrying about emissions.

[yankeedoodoo]

AMMO: The data he referred to was downloaded from the pectel unit and studied @ home the night before the car went onto the dyno, so I must assume that his datapoints certainly came from the program. JULIANS: I beleive the fuel tank does not leak, although the mileage would please all Saudi princes. PC: Your deduction regarding the advance map is probably spot on. He made changes ranging anywhere from 5-15% at various points on the existing map. The 12 figure was applied only @ higher RPM where he managed 166.3 HP @ rear wheels @ 6950 RPM( previously 164 @ 6800 ). He says the torque and HP curves are much flatter from 4000-7000RPM and has advanced 1 cam 4% while retarding the other 2% ( forgot which ). I will receive charts, graphs and a Mr. floppy disc. RK: The answers above now seem to me more reasonable, with clarifications. The car will not be subject to California emissions laws, although i certainly prefer to have it as clean as possible as my personal preference for air pollution is filthy humor---not exhaust gases ( well, flatulence excepted ). The individual I used distributes and installs AEM ecu's and is used by many race teams to get their cars right. He seems to understand the difference between closed and open loop running and offered each as a possibility if I wanted to tune further @ individual tracks. It is my hope that concerns about competence are the result of my ignorance and poor understanding and statement of the facts; rather than the alternative. Am most willing to buy beer and tequila for all respondents and hope we can run some tracks here in Ca. if you can make it here some cold rainy winter.