FredR

Interesting to see your AFR's now creeping upwards at top end- getting more power and leaning out a bit. I use to think that my results with ST2 were very limited by my lack of experience [which they probably still are] and lack of dyno. However, I am starting to think that the anomalies I was seeing were beyond my reasonable control and perhaps more to do with the programming. Pings that seemed illogical, AFR's fluctuationg more than I was happy with etc. I guess the trouble is if you try to tune knocks out there is a danger one is reacting to "scatter" and end up enriching or pulling back timing to no real world availif the repeatability is not there and too many wild swings due to not dampening out/filtering the signals accurately.

It will be interesting to know whether your tune configuration can loaded into the LH via ST2 or whether they are simply not compatible. Preumably if you are modifying bin files maybe ST2 can decode these?

Regards

Fred

AO

Ken,

I was looking at your initial post where we can see the "MAF frequency" plot jumping all about. I presume this data came from the SharkTuner, right?

With this modification, do you have a similar graph (from the same source) showing MAF Frequency where it's smoother?

As to Fred's point on the AFR, it looks pretty steady to me. There are some normal fluctuations, but I would not say it is trending up significantly.

FredR

To be clear, I do not think the problem is in any way related to ST2 or how it works, just soemthing to do with the vagaries of the original system design which was probably "cutting edge" when first introduced in 1986.

As posted earier I wonder how difficult it woud be for someone in the know to gut part of the LH and install faster processing/ memory I/O leaving the unit identical externally as it were.

Rgds

Fred

PorKen

Below is with the plus and minus rate at one.

Note the stubborn peak at 5900. That has always been a problem spot as the way the RPM is read in, the scaling is annoyingly coarse right around the HP peak.
...5500 | 5600 | 5800 | 6000 | 6100 | 6200...


I am having to backfill somewhat to make up for noise which is no longer there, especially after 5800, but I kinda want the AFR to move toward the low 13's after the HP peak. (Less excess fuel = more air.)



The line has become even more rounded since that graph was logged as I have gone fractional, coding separate counters for plus and minus so that the MAF freq has to trend up or down for a number of cycles before adding or subtracting one from the MAF variable. I have not reached a limit, yet. The code is cycled through many many times a second so there appears to be plenty of time to chase the freq.

PorKen

The problem appears to the opposite. LH2.3, with it's trusty 8052 running @ 6 khz is already too fast (for WOT work).
It seems to be far too sensitive to the slightest change in MAF voltage.


Note the MAF reads airflow going through it in both directions.
Harmonic pulses through the intake can make the MAF read richer by pushing back air out, or perhaps even leaner, by restricting air coming in.

FredR

As you say maybe it is reading peaks and troughs in the transients caused by reversion pulses- if it is that quick. You would think Porsche would be capable of dampening out such which presumably is what you are trying to do at the moment.

Regards

Fred

AO

I do have a prototype LH from Volla (Francois). I have yet to get it running, becasue of life, work, or car issues getting in the way. He is also very busy. But it is in process... Maintains stock connector and everything.

Nice... Looks much better. Keep up the AWESOME work.

dr bob

Ken--

Looking at Rob's picture of the sensor element in the bigger tube, I wonder if it's possible to adapt the wiring and software tables to use a more common sensor in perhaps a bigger tube. For those with deeper-breathing engines, it opens the door to less restriction in the MAF itself if the tube is bigger. Plus offers the option of a much lower cost replacement for us stockers, should the need arise.

PorKen

As long as the voltage is pretty much the same around idle, you may be able to plug one in, as-is, and tune it with the base table (and inj size).
(As I understand it so far, the voltage conversion is used for idle and accel pump up ~2.5v, the freq conv is used for everything else.)

I guess there are some MAFs which read in reverse to the 928, but the Fords appear to be pretty close, at least in the shape of the curve?

(EG. from the internet tubes)

hans14914

Ken,

Have you looked at the Abaco MAF? Its scalable, and can be made to match the 928 profile up-to 5v (its a 0-5v device). It has forward and rear facing sensors, and can detect and eliminate most reversion effects. Could be an interesting test if you could tweak the LH to read 0-5v instead of the effective 2-6.5v(ish) range it has now.

PorKen

Haven't looked at anything non-stock, so far. No need (for me), but those look pretty cool.


WRM, (doh!) where I have been saying 2.5V is the max for the voltage conversion, that is what I'm measuring with a Innovate SSI-4 by using one of the (+) channels, leaving the corresponding (-) empty.

This makes for some kind of division (which I don't understand) allowing the 0-5v SSI-4 to read the whole range of the 928 MAF.

(A custom table in Logworks then multiplies the voltage x ~132, which roughly equates to the MAF units used on the table scales.)

hans14914

The low end of the MAF output has a very high shelf to begin with. Breathing on the sensor will get you about 2.5v of output. I never really understood why Bosch shifted the range north like that.

hans14914

Just for fun, I snagged a used DBX-85. If you want to play with it, I can send it your way first.

Its output curve is capable of emulating a SMAF.

PorKen

I can work with this.

The remaining peaks and dips are real, repeatable, IE. they reflect low or high values in the WOT map (64-col for my chip), and can be adjusted out.

PorKen

I have updated the first post with corrected info.

5V max makes much more sense as the limit for the voltage based A/D.

I don't think the whole range is possible in code, because the LH is hardwired for the 2V? Or what are they doing with 0-2V?
Could rescale for max 5V, although you'd lose some resolution.

Would just need a inline amplifier to raise the voltage of a 5V MAF?
(Perhaps in the conversion harness, as there is 12V available there?)