Overboost Fuel Cut Map

Wednesday, August 2, 2017 - 12:30

The donor XDF's identify a map that limits fuelling when overboost occurs, which I've named "Overboost Fuel Cut".
That naming seems to have created a bit of confusion as I've had a few people email asking if they should increase this map to match the torque limiter.

Where the confusion arises comes from common belief that the kangaroo hopping or jerking that occurs when the wastegate fails to operate is a fuel cut caused by an overboost condition. What is actually occurring is quite different.

Back to the ADC

I've posted previously about the signal flow from MAP sensor through the ECU Hardware to the Analog Digital Conversion module.

This is roughly:

  • Sensor converts pressure to voltage
  • Resistor divider drops voltage by approx 10%
  • ADC converts voltage to a value between 0-1023
  • The value is checked against ADC Max and Min

If the value is above ADC Max, a logged high fault is set, and if below ADC Min a logged low fault is set, and the sensor default value is used.

And this is what occurs when the wastegate fails to open. The pressure quickly increases to a value higher than ADC Max, and the sensor default is set.
Limit checking happens at the first stage of processing after AD conversion, and well before any fuelling calculations. While this might appear to be a fuel cut that is simply a side effect of the dramatic drop in calculated airmass.

The real overboost fuel cut

Overboost Fuel Cut Map is used specifically when the current boost exceeds the boost limit value.
The current boost value is calculated as the difference between Manifold Absolute Pressure (MAP) and Ambient Absolute Pressure (AAP). This is obviously influenced by the pressure drop across the air filter and airbox.

Say for example the reading are 240kpa MAP and 100kpa AAP, in this case boost is 140kpa.
However if there is a 3kpa drop caused by the airfilter, that becomes 240kpa MAP and 97kpa AAP which gives 143kpa boost.

The stock ADC Max limit for the MAP is the equivalent of about 242kpa and stock Boost Limit is set at 142kpa. Due to the drop in AAP at high boost you'll generally reach the Boost Limit at least 2-3kpa before the ADC Max limit.

Once boost exceeds the Boost Limit, the ECU limits the amount of fuel injected using the Overboost Fuel Cut map. This limiting remains in place until the current boost drops below the level set by the Boost Limit Recovery parameter.

A few thoughts

My take on this map is that it is used by the ECU to help control boost levels after overboost is detected, and prior to the MAP value exceeding the maximum limit. With stock values this is a small window of perhaps 3kpa // 0.4psi. It is basically a last ditch effort by the ECU to control overboost, and I personally don't' see any legitimate reason to mod this map.

The best approach is to set boost limit and boost limit recovery values at the maximum value you expect to run.
If this is higher than 150kpa/1.5bar boost you will need to replace the MAP sensor with a wider range unit.
Then adjust the ADC Max value to suit - some thing like 250kpa if you have set the boost limit to 150kpa.
Working in this way you will only hit the Overboost Fuel Cut when the boost reading goes above your maximum expected value.

Td5 Datalogger updates

Sunday, June 11, 2017 - 08:00

I've come to something of a Catch 22 where I need detailed logging to properly document and verify the waste gate modulator, and the code that handles torque reduction requests from the auto gear box before I can post details of the maps. On the other hand, if I work on the datalogger nothing much happens on the website.

The combination of changes to the Microchip tool chain which caused issues with my old code, a failed hard drive which lead to the discovery that the Microchip peripheral library installer does not work on current versions of macOS, and the need for a rethink and rewrite has meant the datalogger has been out of action since late December.

When I was playing around with the VAGCOM adapter and Python earlier in the year I had ported//rewritten part of my C code and found that using a publish and subscribe framework solved a few of the issues I'd run into. As a result of that little "ah ha" moment and the hassle of dealing with the Microchip libraries I've been working on writing and unit testing peripheral drivers and a publish & subscribe framework in C.

Over the past few weeks I've been progressively bolting together the code that manages the communications with the Td5 ECU.

The way I've decided to approach this is to look at the ISO14230 docs and build a module that handles the startCommuncations, sendData and stopCommunications commands as the base of the logger/interface. That section is now working quite well and at this stage only requires some additional error handling to deal with cases where the ECU response times out mid-message.

From that base I've been working on adding a command interface and USB interface. The idea is to provide a basic set of ELM-like AT commands to configure the settings from default. The current defaults for "pass through" operation are set to connect to a Td5 ECU in manufacturer specific diagnostic mode - Testbook diagnostics in other words.

In practice this means you can hook up the interface and send requests without worrying about the underlying communications protocols. This is similar to how the ELM327 operates.

This is a short demo of the pass through mode, operating over a serial usb connection. The delay between hitting return on the "21 01" command and the response includes the time taken to connect and authenticate to the ECU.

AAP/AAT sensor swapping

Friday, April 7, 2017 - 12:15

This is a fairly niche modification.

EU2 and EU3 engines are fitted with significantly different airbox sensors.

The EU2 uses a three wire Ambient Air Pressure sensor, while the EU3 uses a four wire Ambient Air Pressure/Ambient Air Temp sensor.

The curve of the AAP portions of the two sensors are different and require different parameters to give the correct reading.

Without adjusting the parameters there is a misread of around 10kPa. You'll get an over-read ( -700 m altitude) with EU2 AAP + EU3 tune, and under read (+700m altitude) with EU3 AAP + EU2 tune.

The problem is not so bad with EU2 AAP + EU3 tune as the engine assumes higher air density in some correction maps and will INCREASE injected fuel and give a 0.1 bar increase in the boost limit. The boost level is MAP - AAP so reducing AAP by 0.1 results in boost levels 0.1 higher than the would be with correct setup. I suspect this is why you often hear the comment that an EU3 tune drives better that the correct EU2 tune.

If you've addressed the issue by installing a 4-wire sensor - replace airbox lid, sensor and run an extra wire back to the ECU - the problem occurs when you want to run an EU2 map on the motor. The under-read means the ECU uses corrections which reduce the fuelling plus the boost limit is reduced by 0.1 bar. It guarantees bad performance.

The fix is in

The way to fix this problem is to use the correct parameters for the AAP you have installed. Search for the values for the base map and replace with values for the sensor you are using.

EU3 - 4 wire sensor
multiplier: 13171 ( 0x3373 )
offset: 267 ( 0x010B )

EU2 - 3 wire sensor
multiplier: 10410 ( 0x28AA )
offset: 1227 ( 0x04CB )

It's not too hard to find these values with a hex editor as I think they are fairly unique. As a rough guide they are somewhere around an offset of 0x6A0 from the start of the fuel map. In a Nanocom .map the fuel map always begins at 0x19010.

The donor-ware XDF's now have a patch that swaps the values. It's a bit rough as it shows a stock EU3 tune as being patched, so installing the EU2 parameters requires "reversing" the patch.

ABS Modulator Option A additional fix

Tuesday, April 4, 2017 - 11:15

I can't say I've had this issue personally, but when my brother owned his D2 he made an interesting find in relation to the Option A fix.

While this information was posted to AULRO at the time it seems to have been ignored and/or forgotten, so I've decided to post the information up here.

One of the potential causes of the Three (or Four) Amigos is an dry or cracked solder joint on the "snout" that the Shuttle Valve Switch plugs into.

Option A (2/3rds the way down this page) provides a way of solving the issue by removing the plastic from behind the snout pins to allow the joint to be resoldered. When my brother went to do this fix he discovered these solder joints were fine. Even after a precautionary resoldering the earth connection was still intermittent.

What Steve noticed was that the "snout" could be moved up and down slightly. After a bit of exploratory digging into the external potting he found a second location with two solder connections where the "snout" joins to the circuit board that holds the external connectors. Apparently these two pins had some kind of corrosion and required a bit of clean up before they could be soldered. After soldering these two joints the play in the "snout" was eliminated and solved the connection remained solid even when the snout was wiggled. So if you are planning on doing the Option A fix it's worthwhile checking that the connection remains solid when moving the "snout".

This photo shows the location of the pins and the kind of excavation required to access. The hole needs to be filled post repair but is hidden behind the mounting so this doesn't need to be especially tidy.

location of snout pins

Td5 NNN ECU "Base" Code

Sunday, March 5, 2017 - 14:15

One of the very early posts one this site shows a diagram of the firmware layout used on the Td5 NNN ECU's.

The portion of memory located between addresses 0x0000 - 0xFFFF was cryptically called "ECU Base Code", with the note that this is not touched during Nanocom .map uploads.

The "Base" code is possibly better described as management or boot loader code. In normal usage the main function it performs is basic setup of the ECU hardware, verifying that certain check points are present in the Variant and Fuel maps, then running the variant map code if everything correct.

The secondary function of the management code is to provide support for factory programming of the ECU. Without a variant or fuel map installed the ECU will boot into a special diagnostic mode that provides access to the functions need to upload .map files, program injector codes, synchronise with the BCU immobiliser, and set the throttle pedal type. I assume this mode would have been used on the production line to program new ECU after installation into a vehicle.

The management code is identical across all the NNN ECU's with two minor differences.

The first difference is the code identifier. Like engine maps each variant management has a unique identifier. The second difference is the ECU hardware code, which reflects the well know NNN numbering. So the thbtp001 ecu code has the indentifer NNN000120, whereas the thbtp005 has the identifier NNN500250.

The complete list is:

NNN000120: thbtp001
NNN000130: thbtp002
NNN500020: thbtp003
NNN500030: thbtp004
NNN500250: thbtp005

If you are simply uploading .map files using a diagnostic tool you don't need to worry about this as the management code is not touched even if you brick the ECU.

Where you can run into problems is if you upload a complete .bin file from a different ECU type.

One of the differences between the NNN000xxx and NNN500xxx ECU's is that the power driver chips used to control the injectors were changed from Intersil HIP0060 to Infineon TLE6220GP parts. While both types of chips use Serial Peripheral Interface bus to communicate with the MCU the format of the messages and the representation of faults differs.

The ECU code uses the identifier from the management code to determine which driver chip is present.

So if you fit a .bin from a NNN000120 to a NNN500020 or NNN500250 for example the Variant code will read the NNN000120 identifier and use the code for the HIP0060 driver chip, rather than the TLE6220GP.

What makes this problematic is that one chip arranges it's fault codes:

A_OverTemp, B_OverTemp, C_OverTemp, D_OverTemp,  A_OpenLoad, B_OpenLoad, C_OpenLoad, D_OpenLoad

with a value of 1 signalling a fault.

The other uses:

A_bit1, A_bit2, B_bit1, B_bit2, C_bit1, C_bit2, D_bit1, B_bit2

If both bit1 and bit2 are set to value of 1 the channel is operating normally, and if both are set to zero there is a "short to ground" fault present.

This means if you send the diagnostic bits from a HIP0600 showing no faults (all zeros) to an ECU configured for a TLE6220GP the best you can hope for is "short to ground" faults on all channels.

The injector fault check is called in the main loop of the ECU code and it's potentially updated every 10 milliseconds or so. I haven't been able to confirm how this impacts general running, but I've been speaking to someone who has had ongoing issues with poor starting who appears to be running NNN000120 management code on an NNN500250 so it seems fairly likely this is related.

Anyway, it's something to be aware of...

Using an XDF with Td5 engine maps...

Thursday, March 2, 2017 - 06:45

There are a couple of little tricks to loading up the Tuner Pro defintions so thought I'd make a quick post on the procedure.
You'll have to excuse the "retro" Win XP look n feel. I'm running a Windows virtual machine under macOS and XP does the job without too much bloat.

1. Open a file to edit.

Use File >> Open Bin to open the file to edit.
For nanocom .map file select "All Files" as the file type.

Open dialog

2. Open the XDF

Use XDF >> Select XDF to open the appropriate XDF file.

Open XDF

3. Add Compare Bin

Use Compare >> Load Compare Bins... to load one or more compare bins.

Load compare bins

With a compare bin loaded you can use the "Show compare difference" and "Show compare bin data".

  • Using a random mod to illustrate, select a range of cells and multiply by 1.05
    Random mod

  • Clicking the "Scales" icon gives "Show compare bin data" - table values from the Compare Bin.
    compare bin data

  • With "Show compare bin data" on, clicking "Show compare difference" shows the difference between the map being edited and the compare bin.
    compare difference

If you find yourself having to load the same base file and xdf every time you start Tuner Pro, go into Tools >> Preferences and under the "Genera"l tab enable the two options to load the last used file at startup.

Footnote

I'm offering what I describe as a "basic" XDF as donor-ware. These have a bit more detail on tables than Td5MapEditor, have some unit converted to more human friendly representations, and allow direct editing on MAP and Boost limits using the GUI.
The "deal" is anyone who makes a donation will receive an XDF of their choice. How much you donate is entirely up to you.

Td5 Tuning - a "Torque Based" approach

Sun, 12/04/2016 - 15:03 -- OffTrack

Introduction

In Feb 2014 I started a small private forum which had as it's main goal the development of DIY Td5 tuning through collaboration and sharing. The forum ran for about 10 months before it was hacked twice and I closed the site.

Shortly after starting the forum, on 11 Feb 2014, I posted a list of key maps and a flow chart of map interactions for the three sets of maps that allow commonly used remapping techniques to be applied to the Td5 engine maps. Subsequent work done with valuable input from mturri, def89, discomad, and russ, included developing and testing the first wide range MAP sensor modification, and discussion of axis extension and rescaling of Smoke Map parameters.

Fast forward to December 2016, and many of the innovations from the Td5Tuning.info forum are now starting to make their way into commercial tunes despite the "strictly for personal use" condition of membership. Rather than leave the information from the Td5Tuning.info forum decay, I've decided to put itinto the public domain so all aspiring Td5 tuners can benefit.

While some have chosen to call this type of remapping "revolutionary", it is more accurate to describe it as the correct way to tune. Rather than working around a lack of information about limiters and map interaction by modifying the injector duration, the aim is to accurately meter airmass and then adjust fuelling parameters to suit. This has major advantages because it allows the ECU to correctly adjust injection quantity and timing.

The method is broadly applicable to both EU2 and EU3 maps. The caveat is that EU3 maps are far more tightly locked to near factory specs and require more work from the tuner to make power. These mods will be covered at a later date.

If your are reading this on the front page, click on "read more". You'll see a list of available "book" chapters , with navigation at the bottom.

Much of the information on the Td5 engine maps posted here has never been publicly available, so if you find it useful, please consider making a donation to the site.

Live data, at last.

Wednesday, April 6, 2016 - 19:45

The logging to sd card is proving to be a bit of a case of one step forward, two steps back.

Most of the the difficulty has resulted from the decision to make the logging "user" configurable.

Rather than the fixed set of logged parameters that Td5 owners are familiar with from the Nanocom, one of the goals is to allow granular parameter logging . Not all data is available as a single request, but for those that are it's possible to log at more than 10 times per second giving very detailed snapshot of sensor performance.

The screen grab below shows some of the data captured on a short 4 minute run around the block. The top graph is Fuel Temp in C and FT sensor voltage. The lower graph is Engine Coolant Temp and ECT sensor voltage. These are being sampled at slightly more than 4 times per second vs the Nanocom sample time of once every 1.25 seconds.

The log viewer app I'm using is MegaLogViewer HD . The big plus of this over the free Nanocom log viewers is that it's very flexible and allows user defined calculations based on the log data.

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