5 replies to this topic

[Muncher]

Bit of background first... A couple of weeks ago I got a Scorpion exhaust and race cat, I was their development car. A couple of days later I experienced a blowing/farting noise from it, took it back to them but when I got there it was fine, they couldn't find any problems. It has since been pretty much fine, sound wise. I have had the EWL come on twice, which I presume is due to the second oxygen sensor in the exhaust, I reset the ECU and it has gone. I have ordered a CEL light eliminator from O2sim.com now. Just had the MOT, the readings are as follows: Fast Idle test: CO % Vol 0.016 HC ppm vol 3 CO2 % vol 15.14 O2 % vol 0.58 Lambda 1.026 Natural Idle Test CO % Vol 0.010 HC ppm vol 4 CO2 % vol 14.11 O2 % vol 2.18 Lambda 1.108 The lambda values seen pretty high, would this be cured by the remap at courtenay or is something wrong with the car?

[Thorney]

THey look a little high but frankly don't look at a remap to fix what is essentially a mechanical issue.

[johnaachen]

Bit of background first...

A couple of weeks ago I got a Scorpion exhaust and race cat, I was their development car.

A couple of days later I experienced a blowing/farting noise from it, took it back to them but when I got there it was fine, they couldn't find any problems. It has since been pretty much fine, sound wise.

I have had the EWL come on twice, which I presume is due to the second oxygen sensor in the exhaust, I reset the ECU and it has gone. I have ordered a CEL light eliminator from O2sim.com now.


Just had the MOT, the readings are as follows:


Fast Idle test:
CO % Vol  0.016
HC ppm vol  3
CO2 % vol  15.14
O2 % vol  0.58
Lambda  1.026

Natural Idle Test
CO % Vol  0.010
HC ppm vol  4
CO2 % vol  14.11
O2 % vol  2.18
Lambda  1.108


The lambda values seen pretty high, would this be cured by the remap at courtenay or is something wrong with the car?

looks perfectly normal to me.....at idle the engine deosnt need so much fuel and so the lambda value will go up to a "lean" ratio to save fuel

at higher revs the engine needs more fuel and so the lambda goes down to whats called "stoichmetric" when exactly 14.6kg of air are required for 1kg of fuel to burn....this is lambda=1.

at higher revs still you can expect lambda to be "rich" as much as 0.9 as the ECU chucks more fuel in to cool down the pistons, turbo etc....

So no more sleepness nights............


I am an automotive engineer and the last big project I worked on was concerning lambda....and we calibrated it to run much, much leaner than this....up to 1.4 in fact!

Edited by johnaachen, 29 June 2005 - 01:05 PM.

[Muncher]

That's good It's a bit close to the legal limit though isn't it? 0.970 - 1.030 ? The MOT place said it wouldn't be performing properly like that... The last MOT had a lambda reading of 1.004. Since then I have got the exhaust done and the timbo airbox mod.

[johnaachen]

That's good

It's a bit close to the legal limit though isn't it?

0.970 - 1.030 ?

The MOT place said it wouldn't be performing properly like that... The last MOT had a lambda reading of 1.004. Since then I have got the exhaust done and the timbo airbox mod.

Ummm.....I am not sure about the legal limit but maybe because of your modifications it has confused the ECU a little. If the airbox has change volume....ummmmmm......actually that shouldn't affect it, no.

The exhaust....ummmmm it may be sucking in more air just before the lambda sensor (this could be the blowing noise you mentioned) and therefore making the lamba sensor reading higher i.e. leaner.

This would be the most likely explanation.....especially if the whole exhaust has been off....can you feel any air escaping from where the exhaust manifold (pipes out of engine) come together and meet the exhaust?


What do you mean performing properly? It is a little on the high side of the range but it shouldn't make an awful lot of difference.....only problem is the exhaust gas might be a little hotter....

have a check for the quality of teh seal with the exhaust and then let me know.

[Muncher]

Just called Scorpion, they confirmed it was fine, exactly the same reading as when they tested it. They said they generally found sports cats caused the reading to go up anyway. Bring on the ITG and remap next week