Any ideas? Trying to decipher Syvecs myself!

[BlueBugEye]

This Pat for the excellent response, I'm going to do as you suggested to recalibrate the Wideband but while the car is at the test station and on their analyser to be sure.

I agree that I need to get the car to an expert but with no MOT or TAX it's hard to get it anywhere! Once it's run in and legal I'll be looking at getting the Map checked and tweaked to suit the refreshed engine.

[stevieturbo]

AM I the only one who thinks trying to recalibrate your ecu/lambda sensor via a gas analyser at a MOT station is a rather bad idea ?

Given the lambda sensor will be affected by any small misfires, air leaks etc etc and have a vastly different response time to the gas analyser.

Surely this isnt a correct approach unless you are 100% sure all other factors are given consideration before doing so ?

[BlueBugEye]

I've looked at the linearisation curve for the lambda sensor and worked out that a subtraction of 0.035 will get my lambda to read the same as the test station - I did bring up the an11v gauge but found that it was reading 0.04 at lambda 1 on the wideband. It's back at the test station now, fingers crossed! Paul I've sent you an email at Zen re getting it remapped once it's road legal!

[pavlo]

Using the gas analyser isn't a bad idea at all Steve. You are trying to jump through the MOT shaped hoop that is defined by the 3 gas, so making changes to get the best result on the test can sometimes give good results, better than just by using a lambda sensor alone.

For example, changing the injection angle can give an improvement in HC and CO, which is often not reflected in a change in Lambda. Your onboard lambda might be slightly different to the 3gas as the 3gas uses an all encompassing formula to determine lambda from all the 3 gasses not just the oxygen. Changing ignition advance and also cam advance on a vvti (or avcs) engine can also make useful gains in getting it through a test. You may also want to target a slightly leaner lambda too, as 1.00 often doesn't give as low a CO reading as 1.02 and if you can remain in the lamdba threshold you are probably going to have an easier time.

All of these is probably in just 4 cells in vacuum at close to lambda, so the risks are minimal and you can always make it a temporary MOT calibration.

Making sure you avoid small misfires and keeping a nice steady lambda are important steps to getting clean emissions too, but the 3 gas can give good feedback to help you make the right choices.

[BlueBugEye]

Lambda passed! But CO and HC well above limits due to an obvious misfire so time to pill the plugs and work out the cause.