Turbo Lexus IS200 (on the cheap!)

Improving the performance of an IS200. Goal - Under £1000

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Lexus IS200's are very cheap in the UK. You can easily pick a nice one up for £1000. The reason they are so cheap is that they use allot of fuel and they aren't really very fast. I aim to solve that. I don’t want to spend too much money on the project however, I could just buy a faster car after all... This will be an exercise in sourcing the cheapest parts through ebay and alternative manufactures (hand rail suppliers for exhaust tubing for example) and hopefully a few cheeky engineering solutions.

The aim of the project is to fit a turbo charger to the engine and reliably make the car faster. There are a few main areas of work to consider

Engine management (ECU)

I will be using a microcontroller (Arduino or similar) to supply more fuel to the engine when required. Extra fuel will be calculated by comparing the engine RPM and boost pressure to values in a look up table (the fuel map).

The factory ECU will be responsible for normal running of the engine. I will be adding fuel and adjusting timing where needed. I have a couple of ideas on how to do this which will be discussed in the build logs.

Exhaust Modifications

The exhaust and Inlet manifolds need to be plumbed into the turbo. I will make a new exhaust manifold to the turbo using laser cut flanges. The manifold will be steel to save costs and ease of fabrication. Stainless manifolds require back purging of the inside of the manifold to stop corrosion. This uses allot of argon which is costly. The output of the turbo will connect to the existing exhaust. I intend the turbo exhaust side to be a straight swap with the existing exhaust headers.

Inlet Modifications

The cold side of the turbo will pass through an intercooler mounted inside of the front bumper. There is already a grill of good dimensions available. I don’t want to have to cut any part of the front of the car to keep it looking stock. Plumbing will be aluminium pipework made to accurately fit the engine bay with a minimum of silicone joiners.

Turbo Sizing

I am not going for an enormous increase in power by turbo project standards (+80HP) and I want the car to be driveable. I need to accurately size the turbo to the car to avoid turbo lag. On a whim i brought a second hand turbo from a Saab 9-5, part number TD04-15T, originally from a 2.3L 230HP engine. We will see how this goes...

Turbo oil feed/drain

The oil drain is now fed through a port in the sump originally used by the oil level switch.

Arduino sketch running an LCD display on the dash. This recieves data via UART and also feeds data out of the usb serial port for logging. Also displays text and audiable alarms.

x-zip-compressed - 2.04 kB - 11/20/2017 at 22:05


Current software running on the piggy back controller. Runs the engine well at around 450 mBar of boost. Runs on Infinion Dave

x-zip-compressed - 7.06 MB - 11/20/2017 at 22:02



Current piggy back design. Running well in the car.

Adobe Portable Document Format - 62.83 kB - 11/20/2017 at 21:59


DWG Drawing - 131.26 kB - 04/05/2017 at 10:23


Part004R1 Throttle Body Flange.dwg

not used but did fit

DWG Drawing - 138.54 kB - 04/05/2017 at 10:23


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  • 1 × Ebay aluminium tubing kit. 2.5'' This is theBay kit that contains 2 straight lengths, 2 x 45° bends, 2 x 90° bends, 2 x 180° bends, joiners and clamps
  • 1 × Universal intercooler 550x140x65mm 2.5'' conections welded on
  • 1 × Various sheet steel, aluminium etc
  • 1 × TD04HL-15T Turbocharger Seem to have been suppled with a number of cars. Mine had the round 3 bolt exhaust outlet
  • 5 × Laser cut flanges See files section

View all 11 components

  • Controller working and Turbo Running Well!

    Rory11/20/2017 at 22:32 0 comments

    I sorted the issue with my piggy back controller missing crank pulses. Turned out the UART port was sending using interrupts instead of DMA and messing things up. Now everything works well.

    I installed a stronger spring in the wastegate, now set to just below .5 Bar. The car is much more powerful now and much more fun to drive. No idea what kind of HP the engine is pushing out now but it must be close to 200.

    I took things easily at first as I had added some approximate values into the fuel map. Eventually I was able to get somebody to drive the car with me sitting in the passenger seat logging the boost pressure, RPM and air fuel ratio. Initially at low RPM the air fuel mixture was running a bit too lean for comfort (around 0.95 lambda). I was able to modify the fuel map to get a lambda between 0.8 to 0.85 at all RPMs (12 to 1). This only took a few runs up and down the road.

    The map is set to retard the ignition timing by 1° per PSI starting around 0.15Bar. I could lower this value and potentially get more power for the same boost pressure but i would be risking detonation and destroying the engine.

    I am very happy with how the project has turned out. There were times when I almost gave up with the engine controller and brought one. Bit of an emotional roller-coaster towards the end!

    I have started to upload diagrams and software etc.

    Tasks remaining are to tidy up the engine bay a bit and to sort out the dump valve. At the moment it doesn’t vent the inlet pressure quickly enough causing compressor surge which is noisy and becoming quite annoying.

    I have booked a track day at Brands Hatch race circuit in mid December. We will see how long the engine lasts!

  • Cam sensor issues continue

    Rory11/11/2017 at 15:05 0 comments

    I sorted out the issues with the RC filter on the cam sensor input. Now every pulse is received by the microcontroller. The micro misses the occasional pulse though. Almost certainly due to may bad code… The cam sensor is read via an interrupt, but so are allot of other things. Need to shorten some of the interrupt routines I think.

  • Piggyback Engine Controller

    Rory11/10/2017 at 09:29 0 comments

    I have made many changes to the engine controller. I started the project using an Arduino mega to control the fuel injectors. This did work quite nicely although I decided that I should also be controlling the engine timing, retarding the ignition on boost to avoid the inevitable detonation that would destroy the engine.

    A friend suggested the Infineon line of micro controllers. These have much more processing power, many more hardware timers and a floating point unit for super-fast calcs.

    I rebuilt the controller using an XMC4700_relax kit. The XMC4700 lite kit would have been adequate. The relax kit features an ethernet port, SD card slot and a CAN transceiver. I had dreams of a web server based dashboard for the car at one point. I will spend some time on this when the car is fully working.

    Here is the controller all wired up in its box. The blue PCB is the wide band lambda sensor controller:

    The XMC4700 feeds serial data to an Arduino in the car which presents this on a LCD display. This works quite nicely. I can also connect my laptop to the USB port on the Arduino which feeds CSV data out of the virtual serial port for data logging. I spent ages looking for a program to graph and log the live data. I finally stumbled across telemetry viewer which is very good. The Arduino display also has an alarm buzzer which sounds when 100% injector duty is reached or when the fuel burn goes lean on boost.

    The serial data contains quite allot of information. Currently I am displaying RPM, MP = manifold pressure (gauge, mBar), Af = air fual ratio (lambda), Lt = lambda sensor temperature (°C). The lambda temperature is important because the sensor won't return an accureate reading untill the sensor is 780°C. Initially I installed the sensor too close to the output of the turbo. It wasnt getting too hot but the wide temperature fluctuations made it hard for the lambda controller to maintain the correct temperature.

    I can now control the fuel injectors and add fuel where I want to based on the engine RPM and boost pressure. The pressure sensor input to the car ECU is limited at a certain voltage (to prevent it thinking the sensor has failed out to high output and cutting the fuel) this is called a ‘fuel cut defender’ in the car word and can be purchased for £140 from AEM. I made one using 1 op-amp IC. Will cad up the schematic and post at some point.

    Still outstanding is control of the ignition timing. The engine uses inductive sensors monitoring a toothed wheel on the crank and cam shafts to determine its position. I am monitoring the sensors, detecting the peaks with a comparator and feeding a signal back out to the car ECU. When I want to retard the ignition, I can delay these signals.

    Initially I was picking up interference causing the controller to trigger on false inputs. A RC filter sorted this out. I was getting a nice clean pulse for every high signal from the inductive pickups however the engine still would not run. A friend suggested that perhaps the car ECU is looking for the point in which the inductive sensor swings from positive to negative.

    I made a circuit to add a negative pulse after the positive pulse using a cd14538. I’m temporarily using a 9V battery to get a -5V signal. This is only for testing hence the horrible bodge tape.

    This is the pulse generated. Blue is the output from the cam sensor and yellow is the signal fed to the car ECU:

    I connected this up and the engine started and ran perfectly at tick over. Increasing the revs caused the engine to cough and splutter.

    Using a scope I could see that sometimes the comparator monitoring the inductive pickup would miss pulses. This happens after the missing tooth on the trigger wheel. I can increase the threshold voltage on the comparator to prevent this to a certain extent but then the small peak after the missing tooth gets missed....

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  • Clutch Slip!

    Rory11/10/2017 at 08:57 0 comments

    With the turbo the clutch was slipping very badly even on only 200mbar of boost pressure. I suspected that the clutch was worn out after 125k miles of service. I brought a new one that is supposed to have a better (more grippy) friction material and stronger spring pressure. I changed this myself and it wasn’t easiest thing to do. When I plan major car maintenance it always seems to rain heavily all day. The release bearing was also wrong which needed some modification with the welder to get it to work properly. Here's a picture of my legs having a bad time under the car during a break in the weather:

    After about 12 hours it was done and there is no more sipping. The performance of the car is much better now, even running on only 250mbar. I plan to run at about 500-600mbar when the piggyback engine controller is finished. See next post.

  • Turbo in Car and Almost Working!

    Rory11/09/2017 at 17:49 0 comments

    So, the turbo has been installed in the car for quite some time now. I have been changing and improving things with regards to the electronics and the wastegate actuator over time and the project is almost fully working. The next few posts will detail these.

    Firstly, the wastegate actuator.

    I had originally make a wastegate actuator which was controlled by a hobby servo, this is described in a previous post. This was controlled by an Arduino in my piggy back engine controller using a PID loop to the manifold pressure. The mechanical side of the actuator worked quite well however I could not get the PID settings correct to maintain control of the boost pressure.

    Having a bit of a think I realised my mistake. The engine controller operates to the manifold pressure, this is the pressure after the throttle butterfly which normally operates at a vacuum. Using this pressure to control the wastegate actuator was not going to work. I should have been controlling the wastegate actuator based on the pressure BEFORE the throttle butterfly valve. Otherwise when the throttle is part open, the boost pressure can build up in front of it without the actuator controller knowing. When the throttle is fully opened all of this pressure floods into the inlet manifold causing a large pressure spike. I would have to install another pressure sensor before the butterfly valve.

    At the time I needed the car to work to some extent so I ordered a pressure actuated wastegate with an adjustable spring to set the maximum boost pressure. Search 'kingawa adjustable turbo actuator' on ebay. I had to modify the bracket a bit to fit my turbo but it comes with most of the stuff you need. Heres a picture:

    This works nicely although it is quite hard to change the spring particularly when the exhaust system next to it is red hot.

    I may revisit the electronic actuator at some point in the future.

  • Turbo Oil Drain

    Rory10/12/2017 at 10:31 0 comments

    The turbo charger needs a return line to feed oil back to the sump. I brought a few bits and pieces planning to drill a hole in the sump and fit a tank connector.

    Here we have:

    15mm flanged tank connector
    1/2'' BSP female elbow
    1/2'' BSP to 16mm hose barb
    To fit the tank connector I would have to remove the sump. This turned out not to be possible without removing the front cross member. To remove this I would have to remove most of the front suspension, steering rack etc, a big job to do on my back in the street.

    I spotted the oil level switch. This came to my rescue.

    Above: oil level switch (some bolts removed at this point
    Above: Oil level switch removed

    As luck would have it, the round part of the oil level switch was almost exactly the same size as the flange on the tank connector. I made an aluminium plate to pick up the bolt holes                    

    Some builder's silicone and the gasket from the oil level switch got the oil drain to seal properly. Note that the seal is on the face of the tank connector. Due to the construction of the sump this will not seal if you make a traditional style gasket fitting over the aluminium plate part. Took me 4 attempts to work this out...

  • Hobby Servo Wastegate Actuator

    Rory10/12/2017 at 10:05 0 comments

    I wanted to be able to control the wastegate via a servo driven via my engine controller. Normally the wastegate is operated via a pneumatic diaphragm directly from the inlet pressure. This doesn’t give you much scope to easily change the pressure setpoint however. After market 'boost controllers' are available which use a solenoid valve to bleed off some of the pressure sent to the actuator. This only give you the facility to raise the pressure setpoint over stock. I wanted the ability to lower the pressure setpoint during initial testing/tuning.

    I brought a Turnigy TGY-1501MG servo rated at 15Kg/cm to do some testing. I chopped up a sab 9-3 wastegate actuator for the spring, spring seats and shaft and welded up a new bracket. My old meccano set came to the rescue providing a roller for the top of the spring seat.

    The actuator worked quite well although I think this application is at the limits of the servo's torque capacity. The holding current is quite high which may cause overheating. The servo is controlled via a PWM signal from an arduino in my engine controller. Will test when I have the turbo installed on the car.

  • Intake Tubing Finished

    Rory10/12/2017 at 09:38 0 comments

    Long time since the last update as usual. Much has been happening however.

    I have finished routing and welding up the intercooler tubing. In hindsight it would have been better to use 2'' tubing rather than the 2.5'. Some of the clearances were very tight, particularly around the ancillary belt pulleys around the right-hand side of the engine. the 2.5'' does match the throttle body inlet though which was nice.

    I had heard bad things about these eBay tubing kits on the internet in that the aluminium was poor quality and very hard to weld. Initially I did struggle, however this was due to my welding setup. After a fair bit of messing about I settled on the following settings:

    Current - 45 to 55A depending on how cold the part was, weld position etc.

    Frequency - 180Hz with 40% cleaning

    Electrode - 1.6mm Ceriated. This made a massive difference over the 2.4mm I started with

    Filler - 5356 1.6mm. I tried to use 2.4 mm originally with not much luck

    Gas - Set your shielding gas correctly. There are a few guides on the net about it. This was absolutely critical. A high flow rate introduces turbulence around the shroud introducing oxygen resulting in a horrible weld.

    I had really got the hang of it by the end of the job. Don’t let anyone tell you tigging thin aluminium is impossible without professional tuition or years of experience!

    The tubing kit was good value, I used absolutely all the bends, nothing left!

    Herse a bad photo of the parts prior to fitting

  • Long Time Since Last Update

    Rory08/07/2017 at 17:54 0 comments

    Long time since may last update. Been busy with other things but I have been able to push the project forward in the last few weeks.

    I have finished the exhaust manifold. Here it is fitted to the car. Luckily it didn’t move much whilst welding and the flanges fit well. I may need to get them skimmed to seal properly but I won’t really know until I run the car for the first time

    I have finished the exhaust manifold. Here it is fitted to the car. Luckily it didn’t move much whilst welding and the flanges fit well. I may need to get them skimmed to seal properly but I won’t really know until I run the car for the first time.

    I spent some time messing about with the cold side of the system. I originally brought a Mercedes sprinter intercooler. These are very cheap and have 63mm tube connections. I couldn’t really find any dimensions at the time so just ordered one brand new for £38 delivered. As you can see it was far too big. It could have been squeezed In I suppose but I would have had to cut up the front bumper allot, run the car without the front crash protection bar and the plumbing would have been messy as the tubing would have had to come forward before heading back into the engine bay, as the photo.

    After this I had a good measure up and found a bargain on ebay. I now have an intercooler with dimensions 550x140x65. This fits very nicely. It was cheap because it came pre-damaged. It still holds air though. I added some brackets and it now mounts to the crash protection bar that fits inside the front bumper. I also welded on some 63mm tube connections to match my pipework. This was the first time I have welded anything important in aluminium (after about 2 hours practice) it’s not impossible but my efforts here are very messy. I wont give you any close up photos! It is still air tight though.

    I ordered an ebay special intercooler tubing kit. I was quite impressed with this. You get everything you see in this picture for £80 delivered. I had to buy a couple of silicone elbows purely because the radius of the bends in the kit are quite large, about 100mm.

    I have ordered a custom braded line for the turbo oil feed. I have the bits for the turbo water flow and return as well. For this I am using standard M12x1.5 banjo to hose barb fittings. The flow and return will tee into the throttle body heater lines.

    I ordered an ebay special intercooler tubing kit. I was quite impressed with this. You get everything you see in this picture for £80 delivered. I had to buy a couple of silicone elbows purely because the radius of the bends in the kit are quite large, about 100mm.
    I have mocked up all of the tubing with aluminium tape ready for welding. I had planned to do the welding in a couple of hours last weekend but that was a bit ambitious. I need much more practice before I attempt this. The tube has a 1.5mm wall and is very unforgiving for bad welding technique. I was using 2.4mm tungsten’s and filler. A bit of research suggests the use of 1.6mm filler and perhaps a 1.6mm tungsten. I think my shielding gas flow was much too high as well causing turbulence. Luckily I did not need the two straight sections in the kit so this give me plenty of material to practice with.

    I have ordered a custom braded line for the turbo oil feed. I have the bits for the turbo water flow and return as well. For this I am using standard M12x1.5 banjo to hose barb fittings. The flow and return will tee into the throttle body heater lines.

    The turbo oil drain needs to feed straight back to the sump for which I need to attach a hose fitting. My sump is pressed steel so I can’t drill and tap a fitting into it. I could have welded something on but I didn’t want to risk warping it and cause oil leaks from the sealing surfaces. A bit if ebaying got me the following: A ‘15mm compression tank connector’ will seal into the sump. 15mm copper compression fittings have a ½’’ BSP male thread so I can use a female threaded elbow to join this...

    Read more »

  • Progressing on the turbo exhaust manifold

    Rory04/23/2017 at 15:31 0 comments

    I went down to building bloqs in north London the other day to build the 6 into 1 exhaust manifold. I cracked on hard for about 11 hours but didn’t manage to finish it one day as I had hoped. It’s all tacked together though and about 30% finish welded. I'm quite happy with how it went. There are some gaps up to about 1mm wide which can be filled with weld but will increase the chances of the whole thing warping. I spent about £30 on the tube and bends from DC iron Super cheap which is goal on this project. I treated myself to an air die grinder (£20 from screwfix, part number 5458H) and a decent carbide burr (a tenner from ebay). That definitely saved me a few hours. Cuts through steel like butter. Dont forget you can click to enlarge photos.

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