Lambda probe

[prs]

I'm about to change the standard exhaust manifold and system on my 1.6SS and replace it with a 4 into 2 into 1 manifold with a repackable silencer. On the standard manifold the lambda is situated in the collector, however on the 4.2.1 manifold it's sited in the 4th primary, will this make any difference?

[John Howe]

That is where mine is situated.. it seems to work fine, though I have lagged the exhaust too keep the gases from cooling down to quickly.

 

 

[Peter Carmichael]

Sensing off just one primary isn't a problem. On higher tuned engines it is common practice to set up the engine to run open loop with no cat. The lambda is just there to keep the fuelling appropriate for the cat. For mapping it is entirely adequate as an indication-only device, although an unheated sensor (muchas wonga) in the collector is much better - it shows how far you are away from appropriate fuelling.

 

Peterid=teal>

253 BHP K-seriesteeth.gif, gearbox and diff waiting to go inthumbsup.gifid=red>

[robmar]

peter - "The lambda is just there to keep the fuelling appropriate for the cat",

 

so if you had no cat you do not need the lambda? is that a correct assumption, or is that too simple. If that is the case is it ok to just disconnect the lambda and chuck it ont he shelf and the ecu will handle it?

 

rob

[Peter Carmichael]

You have an ECU which expects to see a lambda signal and has an algorithm to exercise the fuelling and maintain lambda. If you disconnect the lambda the fuelling will go AWOL, depending on how gracefully the firmware recognises the absence of a sensible signal.

 

No. On a standard ECU you should not disconnect the lambda.

 

Sorry if my first post was misleading, but it was hiding behind the "on higher tuned engines" caveat and the reason for having that in there was to explain why you sometimes see exhaust gas temperature bosses welded into the collectors outside the bodywork of the car on long primary exhausts - it is not an issue to have wiring outside the car for set up, although it is more awkward to make a tidy job of it for normal running.

 

Sensing on a single primary is not ideal but for it to be significant you have to look at the many causes that might make the situation in a single primary different to the others. With a plenum-based engine, the induction side is fairly consistent - you just have to worry about a knackered injector. The exhaust lengths in the caterham exhausts are not 100% matched, but the effects are not usually material.

 

To all intents it works.

 

 

Peterid=teal>

253 BHP K-seriesteeth.gif, gearbox and diff waiting to go inthumbsup.gifid=red>

[robmar]

oops - better put it back in then wink.gif

 

although it seems to be running ok so far, and fuel consumption is no worse/better than before, but I suspect it is more than fuel economy that may be effected.

 

If aything the engine seems to be running cooler, although not sure if that is to do with the camcoated exhaust rather than no lambda....

 

c u at llandow if you make it

 

rob

[paul.davis]

I undertsand the Lambda essentially otpimises fuel at lower rev cruising, the rev limits of which may be a variable on your ECU (in mine it switches off at 3,000 rpm). When pedal to metal it is overuled by the map, I doesnt have a bearing on performance - more economy at the margin. The Lambda also needs heat to work responsively so, the nearer the engine the better, but on the other hand a single primary is not representative of all cylinders. . . . .

 

Paul

 

Zeeeeeeetec . . .