Welloilbeefhooked

iTrader: (3)

I have been monitoring the AFR via my scoobymonitor and found that I only ever get an AFR of 0.836 max at WOT in 4th through to redline.

I was upon the belief that it should be around 0.9v or a little higher to be in the sweet spot. So this has left me wondering if the lambda sensor is reading correctly, and I am indeed running lean, or if the sensor itself is knackered?
I would imagine a low reading would make the ECU inject more fuel? and run rich?

The knock link is only lighting up the first 2 green so I would imagine that at the moment I am safe ish.

This brings to which sensor I need to buy and where from? I take it the sensor is the one that bolts into the downpipe just after the turbo but before my cat (downpipe is a Zerosports freeflow 3" type with open neck).

The reason I ask about which sensor is that I know nothing about them and have heard about narrowband and wideband stuff but dont know if this is sensor dependant.

If its not the sensor what can I do to rectify. HKS-AFR etc?

Any help would be good.



MY98 WRX btw.

Welloilbeefhooked

iTrader: (3)

Can anyone help/advise?

Jolly Green Monster

iTrader: (4)

if you start the car from cold, let the car warm up so coolant at normal temp off boost and then floor it what is the voltage of the sensor on boost.

They tail off when they get hot and each sensor varies slightly. They are not accurate on boost and hence why the standard ecu switches out of using the sensor (closed loop) about 0.5bar of boost.

As you have no knock I would not worry.. it is possible if the sensor is failing and under reading you will be running richer when it is in closed loop mode, idle, cruise and below 0.5bar etc.. but if you have not noticed a decrease in MPG then it is more likely just the sensor heating up.

As to what sensor, you can get a universal one whcih are cheaper but don't seem to last as long or one from the dealer etc.. there might be a cheaper source but not that I am aware of.

Simon

Welloilbeefhooked

iTrader: (3)

Cheers Simon.

I have read a couple of posts that say to do the 4th gear WOT test after crusing for a while or just after the coolant temp rises to normal.

I did the later to test the readings after the temp got to 86 (normal).

Is one of these Halfords specials the cheap and chearful type?

Cheers,

Wayne.

StickyMicky

mine was 795 when i first fitted mine lol

changed the lambda and it shot up to 895/875 ish
try a £30 universal lambda and see how you get on (will be fine in your model of car, mines been fine for over a year now and im running 1.37bar boost lol

Jolly Green Monster

iTrader: (4)

I don't think Halfords sell them any more.. I think they were part number L300 when they did though.

I expect if you search this site for "universal lambda" you should find a source.

StickyMicky

forgot to add, i also cleaned the maf sensor when i changed the lambda

i used a cotton bud with sum tar and glue remover and gently wiped over the actual sensor part inside, this helped my idle smooth out (it was going a bit potty on the AFC by going +2 +4 -1 -3 instead of moving slowly like it does now +1 +2 +3 +2 +1 -1 -2 etc etc)

worth doing IMO

Welloilbeefhooked

iTrader: (3)

Micky and Simon,

Cheers very much for the info.

Micky, will the new sensor only read to 0.9v? I have read that others have higher readings from other types of lambda.

Cheers,

Wayne.

StickyMicky

depends on your car mate

mine runs a tad leaner then others, could be any number of things, fuel preasure could be slightly down or sumthing?

mine is a slightly oddball ecu anyway due to it letting me run serious boost levels without complaing so take my figures as a guide only!

Welloilbeefhooked

iTrader: (3)

Changed the lambda today and cant believe the difference.

I get 916mv on WOT opposed to the 836mv I was getting. It is now alot smoother on tickover and when accellerating. It comes off boost without the jolt I was used to and the knocklink does not show red when going from cruising to WOT.

It must have been knackered from day one of my ownership last year.

The lambda I have removed also rattles if you shake it!! I would imagine it has broken down inside.

I think I will be changing this every year from now on.

BTW, MAF seems to be fine after cleaning.

Thanks again for the help.

StickyMicky

no probs

i couldnt belive the diffrence when i changed mine as well, it seamed to pull sooooo much better

i actualy tested mine tonight on my way home from work and only saw 875, with no 895 at all (it tends to switch between the 2)

i have a less then perfect maf to turbo inlet tube so i will continue to monitor for a few days and see how it fares


good things these scoobymonitors arnt they

Jolly Green Monster

iTrader: (4)

nice result!

AndrewC

Tone Loc

iTrader: (1)

Obviously the brain child of some nerd . Do you have one Andrew??

Tony.

BoxerFlat4

LOL : wait until I get my Ipaq version working....