I'm not the best when it comes to the running of the scoob, so can someone please explain what the AFR does and when its an issues to the running og the engine.

Why putting on a set of headers over OE ones causes AFR problems without a remap?

Why does a cai cause running problems without a remap?

Please can someone explain this to me or put me onto a good site that does.

Thanks
S!

 

Hi,

My understanding of AFR is as follows:

In short it is the amount of fuel to air, which is measured by the lambda when it comes out of the turbo. Its measured here because you want to know whether you are putting in too much fuel i.e. high lambda or too little, low lambda.

Too low AFR = detonation/knocking, the higher the amount of fuel the less likely for detonation but also less power when there is unused fuel coming out of the engine.

Hope this helps in some way.
nicky

 

Thanks Nicky for the info, that I sort of knew.

As my cars miles are going up I want to keep it in the best condition anyway and i think that the lamda sensor in the headers is on its way out so would I be better off buying something like this PLX M300 wideband bosch controller or just stick with an OE lamada sensor?

Thanks
S!

 

Hi,

AFAIK, the wideband is only useful for monitoring for det, i.e. the oem ecu wont benefit from it and infact it might not even work. If you have a wideband lamba seperate and means of monitoring it (wideband gauge i assume) you should be able to spot det (thats what i have gathered anyway, dont take my word for it lol).

Looking back now, i would have ordered a wideband set up (getting it into the exhaust would have been hard work) but when i bought it i wasnt actively looking into that sort of thing...

I think the normal lambda only lasts 20-30k generally speaking so if yours has done more is prob worth getting one anyway....

Someone thats more clued up on these will have better advice, i'm just relaying what i have gathered so far...

 

Cheers nick I'm close to 80K on mt 2001 bugeye.

 

if its still on the original lambda i'd prob have it changed. Its fairly easy to do yourself and if you have a soldering iron you can get a generic one and just cut the old plug off and solder it onto the generic one. Thats all i did.

Saying that if its not showing any symptoms then maybe its ok ?? Anyone ??

 

The wideband is for telling you with a degree of accuracy what AFR the engine is running at - It will not tell you if the engine is detonating, only that it is running at a certain AFR which if lean would cause detonation.
A knocklink would be a worthy investment if you want to monitor for detonation.
Headers can give an increase in flow over std so fitting without a remap can put the map in areas what were normally unused as the flow increase will also effect the loading - which could mean you may be running too much ignition advance and also leaner AFR's which could promote DET. You may also find you see overboost as the duty cycle map would need to be adjusted due to the flow change and the flow characteristics of the turbo.

Cheers

 

I thought the newage used a pseudo wideband lambda sensor which is only available as an OEM unit.

I have now had a senior moment.... I thought High AFR's meant more detonation.

Shaun

 

See, i told you someone who knew better would be along soon

 

High AFR's (Lean) will promote the onset of detonation and can also cause the ring's to nip in the bores

 

hmm, even more confused now!

 

Sorry i got the AFR's the wrong way round....

High afr promotes det
Low reduces chances of det and reduces power output

 

the lambda sensor affects closed loop operations more so than open loop. The AFR tables and timing are used to set the defaults (albeit conservatively) for wide throttle usage.

Higher afr is much hotter, but does not always yield highest power, especially in a turbo motor. But for you, if your sensor is out, no use replacing with wideband O2, your ecu can't read it anyway and won't make use of it unless you have a replacement ecu that does, safe your money and buy a similar spec. Your stock lambda does not saturate afaik until your car has gone way out of closed loop so no reason unless you are tuning.