8v to 16v conversion

[assembled]

Greetings everyone!
I did some searching and did not found any data on this topic. I am curious whether it is possible to convert 8v GTi 90kW engine to 16v engine. Are there additional differences than different head? Is it worth the hassle? Maybe it would be more reasonable to simply find a complete 16v engine with all it's surroundings, overhaul it and drop it in?

[Timmo]

Exhaust is different, larger diameter on the 16v, discs are vented too, iirc on the gti they are solid, obviously rev counters different due to higher red line, etc.
Not sure if the block the same or not?? Something tells me the waterways are different?? And pretty sure gearbox ratio's are different too!

If you can then a complete engine and box job would be good! Or find a back ended donor car!

[assembled]

To do it right is seems a lot of things would have to be changed. I did not think about the rev counter and stuff like that. In that case your suggested donor with rear end gone would probably be the best option. There are some projects involving 16v and 4x4 merge, but technical details are quite scarce.

[dougaldog]

With regards to simply fitting a cylinder head to an 8V block I believe Timmo is correct as there are differences between the two engines. I've converted two BXs to the 16V variant, one GTi and one 16TRS. Provided the engine and gearbox come complete with mounts (although gearbox ones are the same) then it is a simple swap. I believe the hydraulic pump is different (although am happy to be corrected) and you'll then need to ensure that the associated 16V fuel and ignition systems are present.

The ECU will need to be changed along with the loom but they are in the same position on moth models. The cooling system is different as are the hoses and the oil system need to be changed over as well.

Downstairs as Timmo has said the discs are different and the calipers will need changing (or at least the yokes). The exhaust will ideally need changing but for now you could get away with the downpipe.

For stability you should also change the suspension spheres and both anti-roll bars.

Internally as the harness connections are the same from the engine bay to the interior (the non-engine management ones) and as long as you have the corrct harnessess they are easily changed over. As Timmo says the rev counter needs changing but you shouldn't need to rewire anything internally.

Helps if you're a little crazy but the job isn't too difficult if you've got all the bits to hand and suitable tools. Don't know what the rules are in Lithuania but over here the GTi would be classed as a modified car unless you own a valid registration document for a 16V model.

If it helps I do have a spare engine, gearbox, ECU and harness that I will be looking to offload soon. The head needs an overhaul but it's in good condition.............

[jayw]

If nothing else, XU9J4 block is alloy, the rest are steel and 16v compression is higher due to different pistons so the EMS won't function correctly and your pistons will hit the valves! So, it can't be done without changing the pistons and then, to be honest, you wouldn't want to!

[assembled]

Which 16v engine is considered to be the best? There are at least few modifications. D6C seems to be the better choice. Is it?

[jayw]

There are only 2 options, the original D6C (160bhp) which has the benefit of no catalytic converter and more power.

Then there's the DFW (153bhp), fitted with the cat (which is a legal requirement in some countries), it also has lower compression and the ML4.1 EMS incorporates a knock sensor, one of the benefits of which is allowing the car to adapt to diferent grades of fuel.

As for which is best? Well, the both have qualities the other doesn't so it depends what you want to do with it! If you're just going to run it then get whichever you can lay your hands on!

[RobC]

Later (post 1991) cars have M1.3, rather than ML4.1 EMS's.

Some have knock sensors and no cats and remain 160bhp (like mine).

[assembled]

Comparing the motronic ML4.1 and motrolic M1.3 what are the differences?
According to Wikipedia, 4.1 controls all injectors at once and 1.3 controls two banks. Furthermore, 1.3 seems to have extended diagnostic capabilities and knock sensor feature. If I would take a catalytic version with lambda sensor and just get rid of the catalytic converter. Is there any benefit of having the sensor? I suppose it would make the fuel supply a closed loop system as opposed to open loop in case of ML4.1. It should result in a better performance and fuel consumption. Any thoughts?

For 1989 BX a catalytic converter is not required so there would not be any anyway.

[Vanny]

Have you looked at an aftermarket ECU such as Megasquirt? It will be more cost, but probably more satisfying, reliable and robust in the long run.

[assembled]

First of all, I am not going to race nor will chip-tune the car. The idea is to merge 4x4 with 16v to get an ultimate BX that Citroen should have made, but did not. 160PS on a car just above 1 ton will be more than enough for me. I am not going to race. As it is a long-term project, I just want to get the background information so when the time to decide will come, I would already know what to do.
Back to your suggestion on aftermarket ECU. I am sceptical about such things unless they fix some critical original design flaws, for example a modified 4x4 transfer box axle is a good mod as as long as it improves reliability of the initial design. Were there any with any of two original ECUs?

[jayw]

Later (post 1991) cars have M1.3, rather than ML4.1 EMS's.

Some have knock sensors and no cats and remain 160bhp (like mine).

Corrected!

[Vanny]

Were there any with any of two original ECUs?

Hundreds and hundreds of limitations and problems. If there where not, BOSCH would no longer develop ECU's. The better question is, do you need the improvements?

I would strongly suggest that you get this book;

BOSCH Bible

It explains in simple terms the differences between Jetronic, Motronic etc and the relative improvements.

The 205 boys used to simply adapt the existing 8v wiring and control to run the MI16. I believe the 8v 4x4 does not have the same controller as the 8v normal saloon. My understanding is that the 8v 4x4 control system is one of the best to use with an Mi16, meaning stick with what you've got! From memory the 8v 4x4 has electronic ignition for a start, meaning no more wasted spark, and no more burning out plugs before they really need to!

[Mike P]

This is the only 16V 4x4 Bx that I know of, that somebody in Finland has built:

http://www.bxclub.co.uk/forum/viewtopic ... sc&start=0

Mike P

[assembled]

The 205 boys used to simply adapt the existing 8v wiring and control to run the MI16. I believe the 8v 4x4 does not have the same controller as the 8v normal saloon. My understanding is that the 8v 4x4 control system is one of the best to use with an Mi16, meaning stick with what you've got! From memory the 8v 4x4 has electronic ignition for a start, meaning no more wasted spark, and no more burning out plugs before they really need to!

Mine is a Bosh LE3 Jetronic. It figures - GTi pre July 1990 has this one (my 4x4 is from 1989). When I first saw the electrical schematic I tried to find the "real" ECU with more than 9 wires going to it. It was not there... LE3 only calculates fuel ammount. Even cold start is mechanical. Ignition timing, as fas as I remember, is controlled by vacuum. Not a very sophisticated system, I suppose...

Thank you for the book. I am trying to find it now.