AFR Analysis
Turbo Mini Forums

If you do not like spreadsheets, turn away now.

We logged a short run yesterday, just over 20 minutes of log, but 5MB of data. Imported it into a spreadsheet and had 21,000 lines of data!

Very difficult to analise in a graph format.

So I made a pivot table out of the data, with MAP and RPM as the columns and rows respectively. The data fields are the averages of the AFRs for that MAP/RPM cell. The upper figure is the inner cylinders and the lower figure, the outers.

Then I set the cells to the right to calculate the difference between them so that we know where to adjust the injection timing cells. Red means that the outers are leaner than the inners. Blue means the opposite.

Next log will import in easily and give quick results.

Attachments:

12.67kb

Edited by Paul S on 12th Oct, 2009.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I must say I didn't analyse it in details but the difference doesn't seem to be following a smooth or predictable pattern. I was wondering if that could be corrected by moving the timing bins in the table or if it could be because there is a need for more bins and 6x6 is not enough. Or is it that the VE table and the timing table create different vertices?

Jean

http://www.jbperf.com/

I wouldn't take too much notice of the actual values. So far we have only had time to make it safe (ish) and get it running reasonably well. We have just started looking at the whole operating range in detail.

There are noticeable areas where we need to make some significant changes, like just off idle (hence the tip-in problem), cruise and the intermediate boost areas.

We will try to work with the 6x6 tables and shift the bins to get a good interpolation.

It may be that we will have to accept some compromise with the 6x6 tables.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I managed to get half an hour on this this afternoon.

Used the above results to try and refine the settings. Results attached.

A lot less colour on the chart indicating an improvement. However, i seem to have overshot at the lower MAP values. Shifting the values by 5 degrees at a time is too much for the shorter pulse widths at lower revs.

I'll have another go at it before the weekend RR do.

Attachments:

12.27kb

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

The corresponding log for the usual blast up hill through the gears.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Getting better all the time....

What happenned to TPS in 4th ???

Also, even though the graph on the forum is fairly low res, it does look like pulse width dropped slightly as MAT rose towards the end of 4th (just as I would expect) maybe a slightly bigger intercooler needed ???

Schrödinger's cat - so which one am I ???

Edited by Paul S on 12th Oct, 2009.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Edited by Rod S on 12th Oct, 2009.

Schrödinger's cat - so which one am I ???

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

25 ambient today paul !? blimey , i rode my bike up to santa pod yesterday and it was real feel 8 degrees blimmen cold i got !

ah no i see you mean in the past your calcs for the ic are based on those nos,just saw the log at 13deg odd at the start .

Edited by robert on 12th Oct, 2009.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

i thought 90% was extraordinary !

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Hi Paul,
Any news about AFR ?
I have not followed your research since 2009. Now I see you finally recognized the problem is with the wall wetting and not pulse timing, so I'm interested again.

I made 6000 miles with my MPI and as I'm changing lots of parts I removed the head.
The engine was running with outer cylinders richer by 15%. I found exhaust valves white even if spark plug colors were quite similar. So I failed to balance richness even if I think the balance was quite acceptable.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Injection timing is the key to getting it right. Wall wetting does impact on the results, but you can compensate for it by getting the timing right, particularly if you use a single pulse at inlet valve overlap.

I've not done a lot on this over the winter, but what I have found is that the engine tempearture has a significant impact on the AFR spread. As most of the setup was done in warm weather, when I have taken the car out in the cold, the AFRs have spread a little.

I took it out for a blast yesterday and caught a glimpse of the widebands whilst on full boost at over 5000 rpm and they were both reading 11.3:1.

Obviously it was a bit warmer yesterday but I think the new fuel pressure regulator is working much better. I've now also got two AEM widebands that appear more stable at least if no more accurate.

Only problem is that the brake pedal is suddenly an inch lower so I need to sort that out. It could be due to the fluid reservoir being low .

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Wall wetting is function of the intake pressure and engine (wall) temperature.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm