Xu10j2 Conversion

[jengis 0]

This is how I went about doing an XU10J2 conversion using a 306 XSi as a donor. I used the 205’s engine management, dizzy and inlet manifold as I wanted to keep things simple. It was all quite straight forward, as expected, but there are a few things others may like to know if they are interested in this conversion.

 

The non-straight forward bits:

 

The XU10 block I used did not have the casting for the 205 left hand engine mount (not sure if this is common to them all or not). Two bolts attach to the head (fine) and one attaches to the block. I had to machine a steel L bracket and bolt it in place as I would not be happy just hanging the engine from the head alone. I suppose there may be a mix of parts used on other pugs that could solve this problem but I'm not aware of it and my solution was simple enough.

 

The next snag was that the cambelt went very close to the left hand engine mount so I took about 2mm of material off it with the grinder, just to be sure.

 

The well-known problem of the XU10 ports being teardrop shapes and the 205 manifold being square is not a big deal. Using a template (such as a gasket trimmed to the right shape) both the head and the manifold need some material removing, but not much. I managed it with a dremel but an air die grinder with carbide bur is recommended. However, I ran the car for a month without matching the ports without problem. Its not really noticably quicker now they are matched either, but best to spend some time doing it as its far from being ideal. One other point - the injectors sit a lot further down in the head's ports than with the XSi manifold. This means there is an "down-step" in the port profile. Nothing you can do about this and, again not ideal for flow.

 

It will be necessary to use the thermostat housing from the XU5/9 engine to enable the distributor to connect to the camshaft (but it wouldn’t be a great hardship to drill out the centre of the XU10 one if, for some reason, that’s all you had). By using the 205 housing you have the same sensors to connect to the 205 loom. So simple!

 

I used the 306 starter motor as its well known that the 205 one is temperamental and mine was a prime culprit (hammer in the boot for such occasions!) But the 205 one will fit fine also.

 

I had to use the 306 alternator due to differences in the block casting (I’m sorry, I can’t remember exactly what was different) and hang it from the 306 bracket (minus the power steering pump bits). I don’t like to bodge things but I had to use ingenuity to get it secure and tension the belt and it’s not great. This is the only bit that I’m not too proud of so I won’t go into much detail!

 

The exhaust manifold I used was from the XU10 but I would imagine they are the same (don't take my word for it though). The good thing with this conversion is that there are no issues with the down pipe clearing the bulkhead.

 

Cooling system straight forward, can’t remember if I used the 205 water pump or the 306 one (pretty sure I needed to use the 306 one which has a bigger seal) but basically there’s no real issues with piping, its all 205 stuff.

 

The breathers are different between the two engines, the biggest problem being that the XU10 has one “chimney” crankcase breather that connects up to the cam cover without a separate oil drain/filler tube that the XU5/9 has. Whatever you decide you need to do some modifying here. I decided to go with the XU10 cam cover which has two outlets which plumb into the air inlet. I’m not sure if the 306 used a PCV valve or not but I just plumbed them into the available points on the 205 inlet (one before and one after the butterfly). It’s a bit crude and uses a bit of oil but I can always put some wire gauze at the cam cover ends to separate it, if I was too concerned. Ideally I wanted to use the 205 cam cover and keep the 205 filler but the cam cover only has one breather outlet and so does the crankcase. I can’t see how I could make a suitable breather system that would purge without making another crankcase breather opening (unless I have missed one that is plugged?)

 

But the XU10 cam cover fouls the brake master cylinder (and looks ugly). As its plastic I could easily cut out the section of the cumbersome beast to clear the master cylinder, but I cant easily solve the aesthetic issue….

 

Lastly I had to trim the 205's ignition leads to get them to fit down the plug holes. Siply cut the excess rubber insulation with a knife.

 

The two longest, single jobs were connecting the down-pipe to the exhaust manifold and doing up the battery tray mounting bolts (the latter had me cursing for over an hour!) but both these jobs would have been easier if I hadn’t got a nasty gash to my thumb from an electric drill making things worse!

 

Upon starting up the idle was high initially but only because I plumbed the SAD in the wrong way around! It now runs better than the 1.6 ever did. I used the XU10 flywheel as I thought it would settle it down in traffic a bit (or was it because I was too lazy to swap it?!) I have not altered the AFM at all and putting a colourtune in showed things to be a little rich at part throttle, but so did the 1.6 so I’ve no reason to fiddle with it. Its happier running a little bit more advance than the 1.6 too, for whatever reason. My 1.6 was a rare, later model low compression engine at 9.2:1 though.

 

 

That’s about it! I’ve posted my thoughts on how the engine performs in the XU engine section of the forum.

 

Thanks for reading and hope its useful info.