ECMlink how bad of an exhuast leak does it take to effect W/B signal !

[v8killer]

hey guys i have been having a problem trying to tune my car. i have black soot on the back bumper and est afr are in the 9's. but my w/b is showing 11's and sometimes 12's. is there any way i can rule out where or not the w/b is correct or not.....

 

[99gst_racer]

I don't think a small exhaust leak will affect WB reading as much as some people think it will - not 2-3 points at least. Rarely is our exhaust systems ever going to pull in atmosphere through a leak, because the 'pull' (vacuum) in the exhaust system is pretty miniscule on our cars anyway.

What wideband are you using?

 

[v8killer]

I don't think a small exhaust leak will affect WB reading as much as some people think it will - not 2-3 points at least. Rarely is our exhaust systems ever going to pull in atmosphere through a leak, because the 'pull' (vacuum) in the exhaust system is pretty miniscule on our cars anyway.

What wideband are you using?

AEM uego that is free air calibrated within .1-.2 in dsmlink ! i just wonder what could make my afr est 9.0 through the run in link but my W/B be so erratic from in the 11's-12's ?

 

[99gst_racer]

The AEM units are know to have issues with accurately displaying on Link. It's recommended to use an Innovate LC1 instead.

Provided that it's calibrated correctly and the sensor is in good working condition, your gauge should be reading correctly though.


EDIT: Wait - are you actually logging the wideband signal through Link? Or are you just viewing the 'AFRatioEst' in Link?

 

[ImportWarrior]

how long have you had the unit? i had to change my sensor after only 8000 miles.
it might have been able to be saved if i cleaned the sensor up. but i just got a new
one.

 

[v8killer]

The AEM units are know to have issues with accurately displaying on Link. It's recommended to use an Innovate LC1 instead.

Provided that it's calibrated correctly and the sensor is in good working condition, your gauge should be reading correctly though.


EDIT: Wait - are you actually logging the wideband signal through Link? Or are you just viewing the 'AFRatioEst' in Link?

i'm watching both !

 

[v8killer]

how long have you had the unit? i had to change my sensor after only 8000 miles.
it might have been able to be saved if i cleaned the sensor up. but i just got a new
one.

couple thousand miles..... how did you know your was bad ? mine reads fine at idle and it free air calibrates fine !

 

[romeen]

I agree with Paul. IMO, I don't think having an exhaust leak will affect the accuracy of the wideband value hardly any if at all. The exhaust is under greater pressure than the atmosphere so a leak will cause exhaust to leak out, not fresh air to get sucked in. I doubt that losing some exhaust before the sensor location should affect accuracy because the relative concentrations of the gases isn't changing.

 

[destrux]

Where is the sensor mounted in the exhaust pipe?

 

[v8killer]

the rear 02 sensor location !

 

[Ceddy]

A leak in your exhaust will definitely throw a WB reading off.

A fast flowing fluid or gas will suck in and pull along a bordering fluid. Look up Venturi Siphon. It isn't necessary for a vacuum to be present for air to be pulled into the exhaust.

If you have a Narrow Band gauge, or can log the Front O2 sensor, you can compare it to your WB reading at idle to see if its accurate. When the gauge is in the middle or O2 volts are around .5, your WB should read 14.7

I'm not that familiar with Link, but think AFRatioEst is greatly effected by any boost leaks.

If your WB sensor is in the Rear O2 spot, check the flex section, that's always the first piece to go on my exhaust.

I'm not sure if the AEM units are the same, but the Innovatives are real picky about your ground hook up. I had to end up running a dedicated hot and ground, to get it to read correctly.

 

[romeen]

That's what I used to think and maybe it's still true. But it conflicts with my own personal observations.

I understand the venturi concept. But every exhaust leak I have seen could be localized by the black soot coming from within the exhaust stream to the outside. Often times you can feel it by putting your hand nearby and feel the exhaust pulses.

 

[matt98eclipse]

I know this is a really old thread but im haveing the same problem. I have a pretty huge exhaust leak comin from my exhuast manifold pre turbo/right were the collectors at and my wideband reads on the lean side pretty bad when est afr are way richer around 10.9's. Ive even done a 3rd gear pull and didnt get any counts of knock running 10.9 af and 15 deg timing running 20psi on my holset. But wideband gauge is reading lean around i believer 13 or 14 afr.

Would my exhaust leak be causeing this issue also??

 

[Calan]

I've never seen a difference anywhere near that large, but it can definitely cause the WB to be off by enough to be noticable if the leak is big enough.

Your exhaust flow is pulsed; not continuous. As a pulse passes a leak point, the pressure will push exhaust gases out (which you can feel and hear, and explains the soot that Romeen described above). As the pressure in the exhaust drops (between pulses), fresh air is drawn in, which confuses the O2 sensor.

The location of the leak should also change this effect, due to the amount of cooling going on with the exhaust pulses at different points along the exhaust path (which would change the pressure)... I think.

 

[matt98eclipse]

I've never seen a difference that big, but it can definitely cause the WB to be off by enough to make a noticable difference in tuning if the leak is big enough.

Your exhaust flow is pulsed; not continuous. As a pulse passes a leak point, the pressure will push exhaust gases out (which you can feel and hear, and explains the soot that Romeen described above). As the pressure in the exhaust drops (between pulses), fresh air is drawn in, which confuses the O2 sensor.

Just what i was thinkin aswell. Gofer has been helping me tune my car and we been trying to figure out how to get my wideband to display same as being logged but been pretty dificult. I put car into open loop mode and tried to get my afr in the 11.1 range and the richest afr i could get the wideband gauge to read was around 12.2.

Im gonna be getting this exhaust leak fixed asap now.

 

[Calan]

J...we been trying to figure out how to get my wideband to display same as being logged but been pretty dificult.

This is probably due to voltage variations between what the WB unit is reading and what Link sees. All kinds of things can affect the voltage felt at the ECU inputs, so it's a likely candidate.

An exhaust leak should affect both the WB and Link, although possibly by different amounts because of what I said in the first sentence. it could still be a contributing factor though.

Corey knows how to get them reading the same by defining a custom non-linear sensor curve in Link. Fix the leak and then tell him to get on it.

 

[matt98eclipse]

OH corey has been so awsome on helping me get my car tuned!!! He told me to get my exhaust leak fixed first then will see what happens. We were all ready workin on trying to get the voltages to match up in link by doing the non-linear sensor curve in Link.

Hes a great guy and has helped me out alot!

 

[Calan]

Hes a great guy and has helped me out alot!

Don't let him see this thread...his head's big enough like it is.

 

[matt98eclipse]

Lmao ha ha nice! wanna see a log calan so u can just take a quick look at it too and see what you think.

 

[Calan]

Not at a Link PC right now, but it wouldn't tell me much if the WB is off.

I'll glance at it in a few minutes though.

BTW - If he's set up a custom sensor curve for your WB, I'll need the ECMLink properties file that he defined for it in order to see the WB as intended.

 

[matt98eclipse]

Oh ok thanks . maybe im wrong then but basically we were changeing the volts in the rawlinWB to get the wb gauge to read same as link was reading.

 

[Calan]

... we were changeing the volts in the rawlinWB to get the wb gauge to read same as link was reading.

Oh ok. That isn't what I was referring to, so forget what I mentioned about the file.

Something is definitely way off with your WB. The transfer function in Link seems to be pretty close; 2.51v raw is displaying as an AFR of 15.0:1, which is pretty normal for most widebands. This leads me to believe that something isn't right with either the sensor or the WB itself. Unless you really are hitting 15.0:1 at WOT, and either you are on E85 (which your global fuel settings don't agree with), or your knock sensor isn't working.

Is your TPS calibrated? It only goes to 95% during that brief pull.