joeytoad83

no they dont trick the ecu into tuning itself. those afrs arent gonne be exact but they should be close to what you end up. you need a wideband before you mess with any of the settings.

Rogue_Ant

You are correct in that changing the AFR numbers does change the amount of fueling. The AFR numbers are simply displayed for the users benefit. The DME does not tune itself; it does not try to self-correct. If you are using the stock AFM, then the AFR numbers will be pretty close, however they are just a guideline.

The Part-Throttle map is RPM vs 'load'. Load is an internal calculation done by the DME, based off of Airflow/RPM.

Partially correct here. Assuming you are not flowing beyond the stock transfer function (~350rwhp), then the DME will adjust its fueling accordingly. However you are limited to the same target AFR, due to the 2-dimensional aspect of the WOT Maps. Additionally, ignition timing will not change. It will follow the curve, set by the WOT Map. It is best to tune to your highest set boost, and deal with slightly non-optimal tune at a lower boost setting.

It is compatible, but keep in mind the AFR numbers are scaled according to the stock AFM transfer function. Your AFR might be a good deal off from the scaled values.

At this time, MS has more capability. However, this setup uses the stock hardware, and I'm working on adding more functionality for the DIY Tuning crowd...


-Rogue

Rogue_Ant

Ok, the main question I seem to be getting is about using a MAF...
The DME will accept any 0-5 volt signal... It does not know if that signal comes from the stock AFM or XYZ MAF. Built into the DME is an Analogue to Digital Converter. This converter takes the 0-5 volt signal and outputs a 0-255 number (total of 256 points)(this is important, I'll explain later).
This said, the DME does expect this signal to match the amount of airflow used. This is defined by the Transfer Function. Here is the stock transfer function graphed:



This graph is AFM volts vs flow (in grams per second). This is volts vs airflow is programmed into the DME. The actual data can be seen in the "AFM Transfer Function Tables" part of the XDF. Unfortunately the DME uses a rather odd method for calculating this table... Instead of using one large table, and interpolating between values, the DME uses three smaller tables as such:

T1 x T3 x 2^T2

The DME uses this function for all of the 256 possible points. It is this function that makes true MAF conversion impossible, without changing the stock code. For example, if we wanted to use a common Ford Lightning MAF without any sort of piggyback, we would need to change the DME's transfer function data to match the Ford piece. Here is the Lightning transfer function graph:



At first glance, these look similar, but under focus they are significantly different. For instance, take a look at the ~3.4 volt range, I've overlayed the two graphs:



Nearly a 100gm/sec difference! At the same output the lightning MAF is flowing significantly more air...
Now couldn't we just simply put the Lightning transfer function data into the DME and then the DME would understand the new sensor. Unfortunately, the built in function (T1 x T3 x 2^T2) prevents us from doing that. This function predetermines the basic curve, so that no matter how we play with the data in the three tables, it is impossible to truly match the Lightning MAF.

Can we get the MAF to 'work'. Yes, using a piggyback we make the the Lightning MAF output a signal similar to the AFM, and then the DME will fuel/time accordingly. But without a piggyback, we have to change the actual programming code in the DME, to eliminate/modify the T1 x T3 x 2^T2 function. This has been done only once before, AFAIK...


-Rogue

Olli Snellman

Sounds like Vitesse product?

joeytoad83

so if useing the ostrich and tunrepro if i wanted to put a maf on. just hook it up correctly and then adjust the fuel tables till i get the correct afr's ?

Rogue_Ant

Yes, they are who I was referring to...

Exactly.


-Rogue

olie05

Rogue,

thanks for the reply. I have a much clearer understanding of what tunerpro actually does now.

Oliver

Rogue_Ant

No problem - glad to help

951_RS

Great thread, I am most definitely going to be looking into getting this.
I want to ask if I'm buying Vitesse MAF if there's any reason to even use this though. If I use the V-flex would I not get the same capabilities?
I'm sure most of the appeal is the DIY aspect and the fact its only $205, but if you use the VR MAF you replace the chipboard this would be modifying so I'm guessing this wouldn't work with it, correct?

Rogue_Ant

Tunerpro will not work with the VR stuff.
I do not own the VR stuff, so I will not comment on its capabilities or limitations.


-Rogue

951_RS

Alright thanks, this helps me sort of decide which path to take I think.

Rogue_Ant

No problem - feel free to ask, if you want some more info.
Or shoot me a PM.


-Rogue

Dare

I assume they used this approach to reduce the total ROM space needed for the calculation. Perhaps this was required when the code was stored in mask ROM on the processor. Is there room in the later DMEs to store a flat table for the AFM/MAF function?

V2Rocket

back to the AFRs that are given in the fuel tables, those are just approximations based on the stock actual fuel values? and if they are modified how does that change the dme code to add or pull fuel?

Rogue_Ant

Possibly... But with only 256 possible points, even a 'full' table would only take 256bytes. Not a lot, even for the 1980's.
There is definitely room to store a flat table, its just a matter of eliminating some of the redundant maps (which I've already done). The main thing is changing the stock function code to understand the new table...


-Rogue