TVR Regeneration
I have 'misplaced' a few parts of the car over the last few years. One of them happens to be it's original VEMS. (It's now doing service in another of my cars...)
I have some parts of an old VEMS where the main board is beyond repair, so my cunning plan is to purchase a new v3.8 main board and build up an ECU using the spare case and other parts. I note that a few changes have happened in the last few years so I will sketch out a plan and include some questions to make sure I've got all the changes covered.
I have found the wiki pages for the EC-10 connector. This is incorporated into my plan, but I will use an EC-12 connector instead to make a bit more room!
Outputs
Flyback considerations
30v flyback rail is the fastest available for highZ injectors so this will be used.
For outputs controlled by injector FET which do not benefit from heightened flyrail, like: IAC, boost control valves etc. mounting a local flyback diode across the solenoid connector is recommended. This isn't a problem for the TVR because it uses all 8 channels for injection.
It is tempting to increase the flyback voltage and use IGBT drivers (instead of FETs) to close the injectors faster, but it would seem that this is not recommended.
P259 Output Resilliance
Q: Has the resilliance of the P259 been improved? I had one or two problems with it in the past (usually my fault!)
A: p259 outputs have been outfitted with additional on board flyback diodes, this does not help against over-current or ground/powerground connection problems but its does make it more resilient against flyback spikes
I will plan to use the 4 additional NFET option from https://shop.vems.hu/catalog/vems-p-48.html extra NFETS to drive relays or coils so as to better protect the P259 from things like excessive inrush current demands.
Q: Are the additional FETs implemented as a daughterboard arrangement? Is there more information for this option - I am assuming the 4 outputs appear on the EC-10 connector.
Fuelling Outputs
- 8 large Siemens injectors driven from the 8 injector outputs. I used to use IGBTs for these because they proved more reliable.
- Additional NFET output #1 to drive the fuel pump relay. (Extra Output 5 - Drive A)
- 2 Wideband lambda sensors, connected with decent shielded cable, apart from the power. They will be LSU4.2 because I have a box of these to use up!
- Evaporative emissions control valve. Driven from Additional NFET output #2 (Extra Output 6 - Drive B). This will use a secondary PWM control. I haven't used this on VEMS yet, because it is relatively new (since 2014) but how hard can it be?
Ignition Outputs
- 8 Coil-near-plug ignition channels driven from the 8 IGBT outputs. I have both crank and cam sensors so can use them as fully sequential ignition. It looks like nothing much has changed here, and this bit always worked well.
Idle control Outputs
- I have retained the standard 4 pin stepper motor. This is driven using the stepper outputs on the EC18 connector. I see no need to change this.
Misc Outputs
- 2 cooling fans on separate outputs so that they can react to different temperatures. Additional NFET outputs #3 and #4 (uses S259 Out1 and S259 Out2?) drive relays for these.
- Tacho output on P259.
- Shift lamp currently on P259, but may be replaced by more intelligent instruments.
- Check engine / Fault lamp
Summary of Outputs
In theory I have some spare P259 outputs if I use the 4 extra NFETs. The use of NFETs should make the implementation considerably more robust.
Inputs
Sensor Inputs
- All the usual sensors from the EC36 connector are unchanged as far as I can see. There are some minor changes in triggering, but nothing more than resistor values.
- For reference the crank trigger is a VR 36-1 tooth wheel and the cam is a hall based single hole wheel mounted on the cam pulley. Both have been shown to work robustly in the past.
- One channel of knock sensing. (Two would be nice, but so far it seems a little unnecessary)
Q: This was always connected as a "green wire". The v3.8 board looks like it has dedicated tracks. However, Knock #1 now conflicts with WBO2 #2 Nernst cell on EC18 pin #1. Is this correct?
My choice would therefore appear to be to use knock #2 as the main sensor input and limit myself to one sensor, or bring the two sensors out on the EC-10 connector. The former keeps the wiring simple, but the latter frees an EC18 pin to be a spare analog input, and these are always useful - see later.
- Fuel temperature. A useful input to detect heat soak! The car had this from new, so it seems only fair to keep using it on an "anytrim" input. It is to be connected to an analog input on EC18 pin #3.
- Wheel speed input. Again I would like to get at least one speed input into the ECU.
Q: This is on EC18 pin#8 and conflicts with the WBO2 #2 pump + signal. Is there an alternative pin (for either function) that doesn't require too much rework? I have spare capacity on the EC-10 where I assume wheelspeed #2 will live.
- Oil pressure input - mainly for complete logging, but has a benefit for engine safety. Can be on EC-18 pin that has tracks from analog in.
- Oil temperature input - mainly for complete logging, but has a benefit for engine safety. Can be on EC-18 pin that has tracks from analog in.
Control Inputs
- Config switch. Currently on EC18 pin #16.
- launch control enable. Currently on EC18 pin #12
- Shift cut cluch switch. Currently on EC18 pin #6
- RS232. I am led to belive I can have two of these now. #1 is now tracked to EC18 pin #14 and #15 and #2 can be connected to the EC-12.
Summary of Inputs
It appears I can fit everything I want in to the ECU connectors assuming my EC-12 wiring is possible. The goal is now to reduce the number of "green wire" customisations to the minimum.
Proposed Pinout
EC36
| EC36 Pin | Signal Name |
| EC36-1 | Throttle Position Sensor signal |
| EC36-2 | Intake Air Temperature signal |
| EC36-3 | Shift Lamp (P259 ch4) |
| EC36-4 | Tacho output (P259 ch0) |
| EC36-5 | High-Power Ground (GND5) |
| EC36-6 | Injector 7 |
| EC36-7 | Injector 1 |
| EC36-8 | Injector 3 |
| EC36-9 | Injector 5 |
| EC36-10 | Coil #7 |
| EC36-11 | Coil #4 |
| EC36-12 | Coil #5 |
| EC36-13 | Secondary Trigger |
| EC36-14 | Coolant Temperature signal |
| EC36-15 | Not currently used (P259 ch5) |
| EC36-16 | Not currently used (P259 ch1) |
| EC36-17 | Injector 8 |
| EC36-18 | Injector 6 |
| EC36-19 | Injector 2 |
| EC36-20 | Injector 4 |
| EC36-21 | High-Power Ground (GND5) |
| EC36-22 | High-Power Ground (GND5) |
| EC36-23 | Flyback - Keep 30V trans suppressor scheme |
| EC36-24 | Coil #6 |
| EC36-25 | Vbatt - Additional conditioning? |
| EC36-26 | Ground (ECU and signal GND, eg. VR-, CLT, IAT) |
| EC36-27 | Primary Trigger |
| EC36-28 | To Hall sensor for cam position |
| EC36-29 | Throttle Position Sensor supply |
| EC36-30 | Not currently used (P259 ch7) |
| EC36-31 | Not currently used (P259 ch6) |
| EC36-32 | High-Power Ground (GND5) |
| EC36-33 | Coil #1 |
| EC36-34 | Coil #2 |
| EC36-35 | Coil #0 |
| EC36-36 | Coil #3 |
EC-18
| EC18 Pin | Signal Name |
| EC18-1 | WBO2 #2 Nernst Cell |
| EC18-2 | Launch switch (analog ch5) |
| EC18-3 | Map switch input (analog ch2) |
| EC18-4 | Stepper A |
| EC18-5 | Stepper C |
| EC18-6 | Fuel Temperature (analog ch6) |
| EC18-7 | WBO2 #1#2 Pump - |
| EC18-8 | WBO2 #2 Pump + |
| EC18-9 | WBO2 #1 Pump + |
| EC18-10 | Stepper B |
| EC18-11 | Stepper D |
| EC18-12 | Oil Temperature (analog ch7) |
| EC18-13 | WBO2 #1 Nernst Cell |
| EC18-14 | RS232 (pin3) |
| EC18-15 | RS232 (pin2) |
| EC18-16 | Oil pressure (Analog ch1) |
| EC18-17 | WBO2 #2 Heater - |
| EC18-18 | WBO2 #1 Heater - |
EC-12
| EC12 Pin | Signal Name |
| EC12-1 | Fuel pump - NFET1 (spareA?) |
| EC12-2 | Purge solenoid - NFET2 (spareB?) |
| EC12-3 | Fan #1 - NFET3 (S259 spare?) |
| EC12-4 | Fan #2 - NFET4 (S259 spare?) |
| EC12-5 | Knock #1 |
| EC12-6 | Knock #2 |
| EC12-7 | Wheelspeed #1 |
| EC12-8 | Wheelspeed #2 |
| EC12-9 | RS232 ch2 TX or analog in [TBD - see EC18-16] |
| EC12-10 | Shift cut (analog in) |
| EC12-11 | Spare (analog in) |
| EC12-12 | Sig GND |