Temp sensor - error solved

Still learning ...

Last time I fiddled with the ECU, I was very satisfied with the settings I found. My disappointment was even greater when the engine didn't start last Saturday. Although the engine was cold, the fan ran immediately. I connected the tablet only to read 80°C coolant temp. Out came the multimeter to check the sensor, but it was ok. What else could it be? *scratching head* ...

The Emerald ECU has some features to prevent engine damage. One is to monitor the coolant sensor and switch the fan on regardless of a short or a loose connector. Therefore you can set the above/below thresholds in the coolant sensor calibration menu. A loose connector gives 5.0V, a short will give 0.0V, the settings should then cover everything in between -30°C and +120°C (see graph). My settings were a touch too optimistic with 0.9 and 3.9. The default settings from Emerald are as above, but you still can enter user defined values.

With the adapted values, the error disappeared and the car started. Happy again!

Cheers.

Map switch

The map switch will be composed of a 2pole 3position rotary switch and a triple LED status display. I am tempted to put it together with the lambda gauge into a bespoke enclosure. My mechanical skills will decide whether I do so or not.
Cheers.

Lambda practical (epilogue)

With the Emerald rolling road being too far away, I had to learn about mapping and read the manuals, surf the web and ask lots of questions. Especially Karl from Emerald was very helpful and his quick replies prevented me from depression more than once. Mapping an engine on the road is not ideal and I think I only exploit maybe 10% of what the software is able to do. But I'm quite happy with the outcome and will keep the map from last week as a base map for further tweaking. It may be smart to use the map switch for further "upgrades". You can upload up to three different maps and add a rotary switch to choose between them. Above pic shows the needed switch and software configuration.
The plan is to have
- one map to drive around peacefully and do a lot of mpg (l/km)
- one map for fast fun on the road
- one map for MoT
... and find a suitable place for that rotary switch on the dash.
Cheers.

Lambda practical (8)

Sunny weather and some days off meant I had time to spend on more mapping. I was happy with the mpg during the last run, but had some issues when accelerating from lower RPM. A dedicated additional map allows to add fuel during acceleration. Since the whole injection map was a little low, I also trimmed it as shown in above pic (keys 2 and/or 3 to add or retrieve fuel, then hit enter) and added some fuel. I'm quite satisfied with the result and will keep this map for the upcoming blats.
Cheers.

Lambda practical (7)

Lousy weather ... still.
The MTX-L lambda controller with integrated gauge now works and is connected to the Emerald ECU. I searched the web for an alternative gauge, but no find. But I found a circuit to build one, so out I went to buy the parts. Compared with the original circuit, I only left out the two supplementary diodes on top. I replaced the individual diodes with arrays to simplify. Now I have to find a suitable enclosure and a place to mount it somewhere in my car.
Cheers.

Lambda practical (6)

Still waiting for the weekend to come, I surf the web and learn how to map. Some people recommend to extend the number of speed sites to get a more accurate and continious control. A right-click on the column cell allows to enter a different value. You have to do this for the whole range i.e. add as much columns as you want to until you reach the system limit. Now comes the great feature: you have to do it only once and all the other tables are updated. The values are interpolated automatically.
In above example I altered the table from 500RPM to 250RPM steps.
Cheers.

Lambda practical (5)

Good weather, cabling all done, timing checked ... here we go !

The AFR target map, as the name suggests, is needed to define which level is expected relative to load (throttle position) and engine speed (RPM). The control mode is set by selecting the cells, the + and - keys are needed to switch between open/closed loop and adaptive. Save this map on your desktop and then transfer it to the ECU.

Requirements to be met are set in the closed loop dialogue. While driving, the live adjustments screen displays all the data on one screen. You see in which mode the ECU operates and can compare the AFR target with the real AFR actually measured by the lambda sensor.
A short drive proved that the ECU now controls the injection timing relative to the AFR target. Next time I want to check whether the fuel consumption is better now.
Cheers.

Lambda (λ)

Lambda (λ) , 11^th letter of the greek alphabet, symbol for many more than one thing… but here we are interested in what is said about exhaust gases, or more precisely the air-fuel ratio. In a few words I will try to explain why it is important to have a certain amount of air mixed with a certain amount of fuel to get it all burned in an engine. If this is the case, exactly enough air is provided to completely burn all of the fuel, then the ratio is known as stoichiometric. Although I tried to have a lot of information in one picture, some explanations may be usefull.

Related to an automobile engine, we can use an oxygen sensor, more commonly known as lambda sensor to measure how much oxygen is left in the exhaust gases. If we return this data to the engine management system, the ECU can adjust the quantity of injected fuel.

The use of the engine determines what is done with that data.

Starting from the middle, this means that 14.7 parts of air will burn together with 1.0 part of fuel. This means lambda = 1 (λ=1). More air means a leaner mixture, less air (or more fuel) means a richer mixture. So next time you’re sitting together with those petrolheads talking about their engine running a little bit too rich or lean, you at least know what they are talking about!
There are advantages to run an engine lean or rich, but extreme values for too much time may damage the engine. Management systems can be run to take in account lambda values more or less. You decide wether you want the best power or the best fuel economy or a compromise of both.

Modern systems use a large band oxygen sensor. They have to be connected to a controller to have a usable signal for the ECU. The pic shows how it is connected to an Emerald ECU only for example. Other ECUs and controllers may have different pin-outs. The showed pin (35) can be configured internally to be used with a lambda sensor.

Cheers.

Electronic Control Unit - ECU

With one post listing the market's throttle bodies, it was obvious to follow with a round-up of ECUs. There is a wild bunch out there and I had to limit myself with some criteria. The two main topics for me are "free programming" and "universal use". You can find ECUs allowing to be tuned only by professionals or freely tunable ones but for specific engines only, as well as motorcycle, ATV, snowmobile or watersports specific ECUs ... those are not in my list. 
Megasquirt is the most popular DIY controller, you can even solder it yourself if you dare. I avoided its derivatives as they are all based on the same board. Nevertheless, the following round-up may not be complete, so if you know of any other brand, feel free to add a comment. Brand names are links (please report dead links).
Cheers.

AEM - Bosch - Canems - DTA - ECUmaster - Emerald - EMS - Haltech - KMS - Magneti-Marelli - MBE - Megasquirt - Motec - Omex - Perfect Power - Sybele - Trijekt - Weber - ...

Water cooling circuit

As assembly progresses (well, sort of), some theory worse to be spread about the plumbing. Let's start with the water cooling circuit. Starting with a layout lent in a german forum, I adapted it to what will be found in my car once completed (ex the water temperature gauge which will be integrated into the digital Stack dash). Quite a basic setup without a heater, hence the missing pipes and valves. Note the two separate temperature sensors, one for the stack gauge and one for the Emerald ECU. There are two ways to switch the fan once a set temperature has been reached:
1) via the temperature switch (mechanical / bi-metal) in the thermostat housing, fixed value
or
2) via the ECU where the switching temperature can be set as wished.
Cheers.

ECU

 

Why is everything so big in a small car? While looking for a good place for the ECU (electronic control unit), I had to check for enough room to fit the main 36pin connector... and still being able to remove it. At the front you can see the serial connectors, one of them to link with the laptop. And yes, this is the first step to my next major upgrade: fuel injection. More and more of the upcoming posts will treat the conversion from carburettor to EFI.

Cheers.