John Sims

Gentlemen,

I would very much welcome the comments of those of you familiar with the Link AFM regarding the following:-

I attach a graph of the fueling following two runs and a matrix demonstrating the settings relative to the first and second runs. The first run (in red) was after the car had been tuned by a UK Link specialist, the second (in blue) some weeks later, after much road tuning. The Link tuner used a hub dyno; the initial Dyno Dynamics figures were taken a couple of days later and demonstrated a -5 rwh reading over that of the hub dyno. Do note that this is off a 170000 mile 26/6.

The cell values aren't exactly as the Link specialist set them as they had used both master and big zone adjustments in addition to cell adjustments. The figures on the matrix are the resultant combined totals. As I was concerned that using master, big and small cells was impacting on the erratic fueling curve I reset all values to zero and then added the combined results only to the small cells before I started making modifications myself. I am convinced that this has helped to smooth out the fuel curve to some degree.

My question:- Noting what was before, and what is now, what further changes should I be considering?

As an aside, the large negative numbers in the 500 cell region are to try to stop the car stalling when pulling away when it gets hot - it seems to have worked to some degree.

Finally, many thanks to Rick for scanning and hosting the graphs, the full set of which can be viewed here http://www.cannell.co.uk/DD%20E409BKE%20-%202.htm

I apologize that I wasn't in the car to note the track through the cells in the run, but have little doubt that (armed with the boost map off Ricks site) you can make a fair guess which cells are being employed.

I look forward to your comments.

NZ951

Looks like the blue line is getting closer. At least the oscillation has dramatically reduced. Still work to do though!

GPF

Hi John,

Looking at your settings, the first thing that strikes me is that you have a value of 48 in cell 2 (mode). I don't know what 48 means, but mine is set to zero which puts the link box into MAP mode as opposed to TPS mode I think. You need to check that before doing anything else, although it might only affect the accel enrichment operation I suppose.

Secondly, you have 6, 4 and 2 in the first 3 accel enrichment cells (8,9 & 10). My car would run like a pig with massive hesitation issues with anything more than 1 or 2 in those cells.

As for the WOT mapping, are you going back to Weltmeister to make changes? You obviously still need to take a load of fuel out from 5,000 revs onwards, but I know you don't have wideband in the car and you need to monitor your AFR on the next WOT run after you have done it.

I will send you a file with suggestions for new cell values for WOT runs later.

Regards

Graham

'88 Turbo S

NZ951

Just for giggles, take ALL the accel fuel out... I have on my Link LEM V5. It was not really needed.

John Sims

Hi Graham & NZ951

I will check cell 2 - I thought the car was running MAP enrichment as, when I changed to TPS just to see what happened, it ran like a pig. I will also take out the accel fueling out as that is another calculation the Link will not have to contend with, and may assist on the hot stalling issue.

I agree that more fuel could come out at the top end. As you note, I have only narrow band in the car, and wasn't overly sure on its callibration. Now that we have had our first run of adjustments checked I will squeeze a couple of % out of the higher cells.

What I found interesting is, despite relatively small changes having been made to the total cell values above 5500rpm the fuel curve has almost lost its oscillation. This can only be attributed to avoiding the three levels of interpolation cased by master and and big cell adjustment.

GPF

Hi John,

I have just been out to the garage and mine definitely needs cell 2 to be 0 when it's in MAP mode. If I change it to Row Steps - TPS, the value in cell 2 changes.

Check you have "Row Steps - MAP" with your handheld, it's the 4th function ( ie 3 up from Test RPM).

Also, I agree with Andy that you shouldn't need the accel enrichment. I would set it all back to zero until you have sorted the WOT runs - although it will affect the driveability it may be causing the over rich start to your power run.

Oh yes - hey NZ do me a favour and reply to my dumb plug lead/resistor question will you? I know you have the answer....

Regards

Graham

'88 Turbo S

NZ951

The thing with the accel fuel is that if you DONT have a stable MAP signal, i.e. your boost controller kinda flutters a little, (assuming here its the same logic as in the LEM), the accel fuel will get pumped in again. Potentially giving you overly rich and "wavey" AFR lines.

PS I will have a look GPF

John Sims

OK,

Row steps is set to MAP - it runs like a pig on TPS - but enrichment is set to TPS. I swapped it to MAP but again it didn't like it. I have taken the enrichmnet out of the 2nd 3rd & 4th stages but with 0 in the 1st stage transition from idle isn't good, it is much smoother with 4. I haven't had a chance to drive it after playing with the rest.

J Chen

JOHN,
Have you check for vacuum leaks ? I'm installing an AFM soon.
According to info that I've gathered, lots of tuning problems with
the AFM are due to leaks. It seems that the map sensor is very
sensative to this.

John Sims

"Have you checked for vaccumm leaks?"

Not recently. I have a Laust manifold and purasil hoses so I don't anticipate there being too many problems. I did find a leak around #3 injector last time I did a test but haven't checked the system since I installed the #55s.

If anything I would have thought that MAP is more tolerant to leaks than any other system. You can blow off a turbo pipe and the car will carry on happily in normal aspirated mode though down on power obviously. Blow a pipe with the original AFM and you know all about it.

Mike S

The LINK AFM will run with vacuum leaks, but you'll be in the wrong zones at idle. Instaed of being int the 205/305 range you will end up in the 210/310 zones or higher depending upon how bad your leak is.