Thomas 205GTi16


I have been thinking of doing this conversion for some time now. The only thing that actually has kept me is that I have not had the garage that I would need. Even that I have been known to often underestimate time, I understood that it would take more than a Do-it-yourself-Pay-by-the-hour garage this time. I also had to realise that I would not be able to use the car for awhile. So one day, as I was looking for a garage for my other car, I came by a perfect place that was large enough and had all the facilities that I needed

The engine

One thing that had to be sure was that the new engine had to be fresher and newer than my original. It is easy to find a used MI16 engine in Sweden that has gone more than 160000 km but that would be a waste of time and effort, and would probably end up with a car with all the typical problems of the MI16’s of that age (oil leakage etc, etc). I started to look for the newer XU10J4 engine instead, the one that you can find in the newer MI16.

Most people say that this is the wrong engine to use, as it is much heavier than the former XU9J4 (which had an alloy block). But the XU10J4 is a 2 liter and the iron block can stand hi revs for longer periods than the alloy one without melting down.

So there it was, a XU10J4 from a –94 405 Mi16 LeMans, 155 original HP’s, that had gone less than 80000km – perfect !!!

Removing the original engine

This was the easiest part. I decided to lift the car off from the engine instead of the opposite and release the complete package with engine, gearbox, studs, driveshafts wheels etc, all in one piece. It is also much easier to work with the package in this way, as you can move around the parts more conformably. The complete process to remove the package from the car took about 6 hours, most of the time spent on figuring out what had to be kept and what could be wasted.

Engine – clutch – gearbox

Before starting this project I had spent some time examining the engine mounts, exhaust- and inlet manifolds, gearboxes etc. both on the 205 and on the donor car. But I wasn’t sure where the MI16 engine should meet the 205 things. Should I use the MI16 clutch and the 205 gearbox? Or should I take the gearbox also from the 405 and mount the 205 driveshafts on that? Finally after experimenting back and forth I found out that by replacing the flywheel on the MI16 with the 205 original, it would then be possible to fit the 205 clutch, gearbox and driveshafts. The advantage of this is that the 205 flywheel is lighter (at least some grams), which I suspected would let the MI16 engine rev easier. The drawback is that it would have been better to use the MI16 clutch as this is designed to the more power. Anyway, I could keep my original gearbox, the original BE3 box, with lower ratios than the 405. This will give me nice acceleration at low speeds. The top speed is probably lower this way, but the MI16 engine revs approx. 1000 rpm more than the original 8 valve.

Before assembling everything, this was the perfect time to replace things like clutch, time belt etc. I also replaced the studs and spirals to sporty ones and added new drilled brake discs.

The shifting mechanism was also replaced with a modified one - a quick-shift.

I replaced the lower engine mount with the one that came with the MI16 engine. There was not much of a noticeable difference but the MI16 one seemed to have harder rubber, probably only because it was newer.

Exhaust- and inlet manifold

The MI16 engine fits fine in the 205, but it is really tight around the engine. The most critical spots are between the inlet manifold and the radiator and between the exhaust manifold and the bulkhead. Some that have done this conversion before me are using the original MI16 exhaust manifold and are tilting the engine backwards down, probably by making the lower engine mount longer. This is said to give oil starvation problems if the car is driven hard. Some say that the driveshafts are also worn out faster as they are put in a wrong angle. Oil starvation is something that I wanted to avoid, so I decided to mount the engine in its original angle. I had to either make an exhaust manifold myself or have one done by someone. After searching on the net, I found a company in the UK (Racing Solutions) that made manifolds to be used in these conversions. They have both inlet- and exhaust manifolds. The 4-2-1 exhaust manifold seems to be specially designed from scratch, but the inlet manifold is a original one from the XU9J4 that has been shortened. After comparing a XU9J4 inlet manifold with my XU10J4 manifold, I decided to try to use mine without modification. It seemed to fit even without having to move the radiator forwards. But I would need their exhaust manifold.

According to Racing Solutions, this manifold should give me approx. 7-8 more HP’s in the mid-range.


As I had the radiator removed from the car, this was the perfect time to upgrade it with double radiator fans. The 205 is already prepared for this from factory, probably it is an option in some warm countries.

My original engine seemed to have oil cooling by leading the cooling fluid (water) through a channel in the oil filter mount. This is tapped from (and back to) the fat hose that goes between the thermostat house and the radiator.

This special hose was difficult to fit on the new engine. Besides, the MI16 had three connectors coming out from the thermostat house, the big one that goes to the radiator, one smaller with a backwards direction to be connected to the heater radiator inside the car (in the same way as the old engine), but the third…hmmm…where was that supposed to be fitted?? I had no idea. So I lead this to the oil filter cooler (the MI16 engine had the same oil cooler as my original engine).

The output from the oil filter cooler had to be joined somehow back to the fluid system. I found a plastic plug on the right side of the radiator, that seems to be there for a thermal switch (of same type that is fitted on the left side of the radiator) when a second fan is used.

Electrically I connected the fans in parallel with each other. The thermal switch in the radiator has three connectors. This because it has two switches integrated in the same body. You can see on what temperatures it should switch by checking the numbers. Mine switched at 97 and 102 degrees. This was in my opinion too late. I needed to have it replaced with a earlier one.

Why are there two switches then? The one that switches at lowest temperature is connected in serial with a resistor (with same resistant as one fan). Thus only 6V will be given to the fan and the fan will run in half speed. Second switch is directly connected to the fan, thus giving it 12V = full speed. (In my case my parallel fans will run in 2/3 of full speed when first switch goes on and full speed when second goes on.)

The original water expansion tank was now too big to fit in its original place, so after some trials moving it to other places, I decided to try to find a smaller one.

I finally decided for this one from a Volvo 740.

Time belt

Your worst nightmare is probably a broken time belt on the MI16. So I didn’t want to take any risks there. It had to be exchanged before putting the engine into the car. It seemed to be almost impossible to exchange even with the original 1.9, so it will for sure not be better afterwards.

(Here’s how it looks like afterwards, about 2 cm’s of free space)

Changing the time belt was not so tricky. There are three obvious spots that need to be fixed before loosening anything.

The perhaps tricky part is to know how hard to tighten the belt. I had no equipment for measuring the tightness, so I did it by first feeling the tightness on the old belt before loosening it and then trying to remember that feeling (I wonder if Peugeot has any comments on this ;-) ).


The new engine was equipped with an air conditioning pump. Actually there were two different pumps. These I had no use for. They are just extra weight and steal a little bit of power from the engine. So they had to go.

After removing those, and the two helping wheels that also tighten the belt, I only had the alternator left.

When I had figured out how to put the things together, it was quite easy again. I just pushed the package under the car and lowered it. Much easier than I had expected.

The exhaust manifold followed the shut board smoothly and there seemed to be enough space in front of the engine to fit the radiator.

To make some space, I removed the wiring tray (the black plastic thing under the inlet manifold) that was in front of the inlet manifold. I re-routed the wiring a little bit lower.

The engine wiring

This part was the most time consuming part of the conversion. The XU10J4 engine wiring numbers have little in common with the 205's. It would have probably been much easier if I had chosen the XU9J4. The XU10J4 is based on the Motronic 3.2 system which is more advanced than my original. It handles both the injection system and the ignition system in one. So I had to get some wiring diagrams from both the cars. Most of the information can be found in the Haynes manuals, but they are not complete with everything I needed. After some days of comparing diagrams from Peugeot service, diagrams from Haynes, following the wires on the engines I hit the wall. I found out that the engine that I had bought was equipped with a original immobilizer. Some of the MI16’s are equipped with a codebox that unlocks the engine. This was not included with the engine as I had received it. #@%&¤#@£$£@ !!!!!

So, the day after, I called up the company that had sold me the engine, praying that they hadn’t made a small cube yet of the donor 405. Luckily, the guy called me back after some hours and said that he had found the codebox, but not only that, he also had the code for it !!!!!

But still, even with the connected codebox, and with help from all the nice schemes that I had gathered, the engine just wouldn’t start. The starter engine went fine but otherwise it was stone-dead. I fought for almost two weeks without any progress.

I decided that I would need some advice from somebody that had done this before – I contacted Bram. It proved out to be a silly mistake, two cables from the codebox had been switched. Afterwards, I have wondered if I wore hockey or boxer gloves when connected the cables.

The first test drive

The first drive around the block was really bad. The engine had no idle at all. I had to drive it by always having one foot on the gas pedal. When I had to use the brake I had to turn my foot so that both pedals were pressed down together. Otherwise the engine would die. It felt like a constant earth quake inside the car, everything that could vibrate did so. I had to hold one hand on the panel to damp some of the worst sounds. I also had difficulties getting the 1st and 2nd gear in.

The reason for the vibrations was obvious when I took a closer look under the car. It was the exhaust manifold that leaned against the floor and against the gear shift linkage. Obviously, the handmade exhaust manifold was not perfectly suited. I suspect that it is originally made for those that use the XU9J4 engine in these conversions.

What to do then? Either I had to move the floor inwards in the critical spots, or tilt the engine a bit to get the extra cm in between . Modifying the floor (hitting it with a big hammer) would mean that I had to somehow get some working space there, in other words, removing the engine again. Tilting the engine seemed then easier, I only had to lengthen the lower engine mount (the fork-like part) . This is what I think some do when they use the original 405MI16 exhaust manifold instead of a modified one. But the difference is that I only needed just a slight tilt.

The engine mount is easy to remove, without having to remove anything else. You just have to lift off a bit of the engines weight.

I made it approx. 18 – 20 mm longer and that did the job.

Then I had to move the black bar 2 cm’s forwards (the bar that is placed just behind the yellow anti-roll bar)

After that, all vibrations disappeared, and the car went silent, without any sounds

 The problem with the gear shifting was also obvious, it was the lambda that prohibited the linkage arm from moving completely to the left. The lambda had to be turned pointing a bit slightly downwards.

Now I only had the idling problem left. Almost everything is electric on the new MI16 and there are not many points that can be tuned as in the good old days, no idle mixture screw or anything like that. The only thing to check is if all sensors are connected properly and are working as they are supposed to. I spent days going through all books I could find concerning Jetronic, Motronic etc. Then suddenly I remembered the thin pipe that I had ignored, all the time thinking that it could not be important. The funny thing was that I had one question left concerning the ECU.

What is the thin copper pipe beside the connector for? Is it for cooling off the CPU in the ECU?

This is when I got the brilliant idea: I have one long plastic pipe approximately 7-8 mm thick that I do not know where to put, and I have a copper pipe on my ECU that seems to take a pipe from somewhere about the size of 7-8 mm. Hmmm…

But why, why is there a pipe on the ECU? After some research on the Motronic system, I found out that some models have a pressure sensor in the ECU, that measures the pressure in the inlet manifold. Suddenly everything was logical again. As the pipe had just been lying open, it leaked air into the manifold. This air that came in here was ofcource never measured by the air mass sensor, which gave a signal to spray less fuel to the manifold. That’s why the engine didn’t idle.

I finally changed my exhaust system to a 2,5" from the cat and back. The cat was exchanged to a (metallic) racing cat with 3" connectors.

The result

How is it then when it is finished, is there any difference? Well, it behaves as you would expect. Much stronger in the low and mid range. This makes the car easy to drive in city traffic. You almost do not have to bother which gear to use, it moves forwards anyway. It is a great feeling, hitting the pedal and flying away up to approx. 7000 rpm, but you have to watch out for the rev limiter. If you exceed the limit (which is easy to do), the ECU will stop your acceleration in a cruel way. Something that puts allot of pressure on the driveshafts and gearbox.

The car seems to understeer a bit. I have not figured out for sure if it understeers much more now than before the conversion. It might also be because it is much easier to reach hi speeds faster and it is easier to get yourself into situations that you can not master.

Thomas Fafoutis
Stockholm, Sweden