What's going on 'ere then?

Take a look at this log file taken yesterday.

All looks cusety boo untill, bam, just over 6000 rpm the AFR drops from 11.7 ish to 9.3 with no massive increase in injector duty.

Maybe a testament to stock turbo efficiency range? I'm still getting 17 odd psi but maybe the temps are sky-rocketing. I would ignore the air temp on the log as that's not calibrated correctly.

Let me know what you guys think...

Run1.zip

Hi,

Looking at the logs,as soon as the AFR drops your knock voltage goes on the up, I dont think that is knocking tho, as its not gone above what you told the AEM was knock. So, that must just be alot of engine noise as you climb the rpm.

I honestly dont know, are you running a AIT? I would have thought that as you go out of the efficiency range, the less denser air(hotter), would cause a drop in injector pulsewidth and the AFR would stay stable irrespective .. but you dont have 02FB mapping right?

Are you in any way running a boost comp'd mapping,as if you where that would rule out any irregularities ....

Try Aem forum tony, they should know whats up.

Hope you get to find out Tony. Let us know.

Getting to grips with the software myself, its quite neat isnt it?

How about the datalog in a readable format

-Ian

Download it you Lazy ..

Hi,

 

 

 

Looking at the logs,as soon as the AFR drops your knock voltage goes on the up, I dont think that is knocking tho, as its not gone above what you told the AEM was knock. So, that must just be alot of engine noise as you climb the rpm.

 

I honestly dont know, are you running a AIT? I would have thought that as you go out of the efficiency range, the less denser air(hotter), would cause a drop in injector pulsewidth and the AFR would stay stable irrespective .. but you dont have 02FB mapping right?

 

Are you in any way running a boost comp'd mapping,as if you where that would rule out any irregularities ....

 

Try Aem forum tony, they should know whats up.

 

Hope you get to find out Tony. Let us know.

 

 

Getting to grips with the software myself, its quite neat isnt it?

Usmann, no AIT yet I'm afraid. I've got to fit that real soon. Should be good to see what kind of efficiency the stock tubbies have at higher than stock boost level and high rpm.

It's not boost comp'd, just cell by cell and there's no O2FB. Just for some reason AFR takes a nose dive? Very strange. Even if it were knocking AFR I would have thought been heading the other way not rich???

Cheers,

Tony

Download it you Lazy ..

I did download it, but it's in a format for, I assume, the software used to datalog it in the first place. If it was say exported as a CSV I could read it in NOTEPAD

I did download it, but it's in a format for, I assume, the software used to datalog it in the first place. If it was say exported as a CSV I could read it in NOTEPAD

Or Excel..

Ian- I meant the software, pfft you LCD screen tuners(Profec )

Tony, It depends on how the AEM is setup to deal with knock, usually the timing gets retarded and then more fuel gets thrown in to bring cylinder temps down( using Knock%rich/volt table) and then the knock restore rate/knock decrece fuel are used to input the amount of fuel taken away per Revolutions.

You to get a AIT in there dude.

LCD?! How dare you, I datalog and use a laptop I wrote my *own* software so up yours

Anyway, can anyone put that datalog into a csv then hmm?

-Ian

OK I'll put it into excel format for those of you that are particularly technically challanged!

Here you go.

I've extracted only the more relevant data.

Exported from Run1.zip

I assume "engine load" is psi of boost, seeing as you say you get 17psi. Odd though as you are getting 14psi before #2 turbo is online... I'm assuming you are on stock twins due to your initial comment about the efficiency range.

Some of those voltages stay remarkeable consistent over half a second or so, is that the software sample rate or that the accuracy of the sensor isn't really to five decimal places

I'd say that you are correct with the efficiency range of stockers call. The AFRs start richening up at 5000rpm. You have the boost holding strong at 17psi (I think) which is about 1.2bar, and normally they run at 0.8bar. That means by the time you reach 6000rpm the engine demand for air has increased by 20% so the flow of the turbos needs to rise 20%, but as they are going out of efficiency, the air temps rise nonproportionally and so comparatively less oxygen molecules get into each cylinder than at 5000rpm.

Meanwhile, the fuelling is steadily going up, as it should, according to the duty cycles, but there is less O2 to burn so it ends up a richer mix. At about 6300rpm it really starts falling apart, the intake air temps must be going sky high...

Seems to stay uber-rich after you lift off. Maybe this is unburnt fuel that is having a hard time escaping the cylinders because the boost comes off in about 0.2s and then it's vac because the throttle is shut - not much air going through. Although your injector duration seems rather high for a closed throttle, it should be more like 3ms...?

This is theory of course, if you could stick an air temp sensor in (or datalog off the stock one in the plenum already) you could prove this one way or the other...

Hope that helps, I'm not saying it's gospel, feel free to shoot at it

-Ian

Right, what Ian has said I agree with!

my POV was that the ecu logs AIT right, seeing as we are talking about SDS(speed density systems) thus a MAP sensor, and a temp sensor to calculate the rough density of the incoming air into the motor.(O2 content)

Thus if the car had been mapped with a AIT you would not have this irregularity of AFR,as the ECU would compensate for the AIT and sees the drop in O2 content and thus reduces your PW in accordance to get to the target AFR.

Again, Like Mr "I make ma own software" , thats how I understand the simple principle of SDS.

Or if you had O2 FB mapping, then you would not see this.

Now, my mistake was that I thought you were running AIT,sorry!

But, yes your efficiency theory seems to be the ticket ..

LOL at you two. That's what I kind of figured.

I'm hopefully going to fit the AIT probe this weekend. There's no calibration that comes with the AEM for the stocker, but TBH it wouldn't be much of a problem to calibrate it myself with a themometer a pan of hot water and a voltage supply. Bloody yanks and their mass air flow system!

The sample rate is down to my laptop being, errmmm let's say not state of the art, but saying that it should still be 5hz or so, the same as the time sample. I can log internally, and go right up to something like 1000hz probably but as you increase sample rate total sample length is reduced (only 500mb of internal memory!) I think you can set the total number of decimal places. Not sure though.

I'll also look into the rich on lift off. It probably will go rich for a small amount of time, but it then goes into deceleration fuel cut off, and goes massively lean (not a problem as no load).

Cheers chaps

Seems to stay uber-rich after you lift off. Maybe this is unburnt fuel that is having a hard time escaping the cylinders because the boost comes off in about 0.2s and then it's vac because the throttle is shut - not much air going through. Although your injector duration seems rather high for a closed throttle, it should be more like 3ms...?

What would help, once this saga has been truely outruled/resolved.

Looking at the log again,I would wind the ignition timing up after the throttle has been shut, as its at a point of low cylinder filling, thus helping to get the excess mixture out of the motor easier, and then letting the deccel fueling take over, like you say.

Ive seen as much as 60 degrees on supra mappings after WOT runs, and throttle being shut. But not saying you should run that.

All, IMO,HTH