Turbo Lexus IS200 (on the cheap!)

I rcieved my second hand ECU yesterday. I have started matching up the connector pins with the wiring diagram. Helpfully lexus include the connector reference and pin number on their diagram. There are a few inconsistances however. The diagram is probably from a different year. Where possible I will have to trace out the wiring loom. Will upload a pinout of the ECU when complete.

I removed the exhaust headers from the engine last night, after battling with rusty nuts and bolts under the car. Managed to get them apart by drilling a hole at an angle through the seized nut and bolt. After working through various drill sizes I was able to break the bolt with a hammer and chisel.

Once removed I could measure up the flange dimensions and design the exhaust manifold. I will be using hand rail weld in elbows from http://www.dciron.co.uk/welding-elbows/ . These are super cheap, only £1.40 a bend! The 33.7mm outside diameter bends are a good match for the engine exhaust port size.

Obviously messing about with the bolts took ages and I was working by torchlight putting the car back together (with new bolts of course). I live in a flat on a fairly upmarket London street. My neighbours think I am very unusual. Lots of, 'mummy what is that strange man doing to that car?'!!!

The sticking point on this project is engine management. In an ideal world I would replace the factory ECU with a standalone device. These cost £1k plus however so that is out of my price range. There is a device called 'megasuirt', which is a basic ECU kit available from the US for about $280. To make this work with my engine would require some modifications. I wasn’t happy with the quality and connectors supplied with the unit either.

I spent some time reading forums of other peoples upgrades. It seems that a common option is to use a 'piggy back' ecu to modify the fuel maps to accommodate the turbo. The device interrupts sensors (lambda, manifold pressure etc) and modifies the value to trick the ecu into supplying more fuel. Again these seem to be very expensive for what they are. around £800+ from my research. Obviously, you are paying for the software that goes with it but it seems a bit steep for a microcontroller in a box.

The route I am going down is to make my own piggy back ecu. Attempt one is make the factory ecu fuel correctly by interrupting the manifold vacuum sensor. If this does not work, I will monitor the status of the fuel injectors and configure my device to hold them open for a longer period (by grounding them externally of the factory ECU). The timing here will be critical and I have limited experience with micro controllers... Wish me luck!

I spent some time thinking about sizing the turbocharger for the project. I have been reading the turbocharging performance handbook by Jeff Hartman.

https://www.amazon.co.uk/Turbocharging-Performance-Handbook-Motorbooks-Workshop/dp/0760328056/ref=sr_1_1?s=books&ie=UTF8&qid=1489498362&sr=1-1&keywords=turbocharging

Using this i have determined that to get a peak power of 250hp at 7750RPM i will need 7.2 PSI at the engine inlet which equates to around 9PSI across the compressor (including losses in the pipework, air filter etc). This is at a flow rate of 12.47 kg/minute.

I was then able to look at compressor graphs for various turbo chargers. Is seems that turbo charger compressors are optimised for higher boost pressures so there were not many that seemed to suit my application. Did a bit of ebay browsing and Mitsubishi TD04 turbos originally fitted to SAAB 9-3's seemed to be the best match. I put an £85 pound offer on a used example and the seller accepted. Should receive it in the next few days.

Any project goes from being an idea to a real project after the first parts purchase. Today I ordered a scrap factory ECU for the car from Ebay from which to unsolder the connectors to the wiring loom (£15) Looks like this project has started! I often think that my love of making things and tinkering could, if uncontrolled, turn into a full-blown addiction. This is the first pint in a yearlong alcohol binge. Oh Dear...

I have also ordered some PCBs from dirty PCBs to try out this open source wideband lambda controller https://www.14point7.com/products/slc-free.