BX 2.0 CT Turbo, it begins....

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Kitch
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Re: BX 2.0 CT Turbo!

Post by Kitch »

It really doesn't like you've thought about this Tim.

Diesel gearbox.....so you want your car to be doing about 4500rpm @ 70mph? Xantia ECU.....I'm not gonna make a third post on stand-alone ECUs, but you are entering a world of hurt with the Xantia gear.

It's not meant to knock you or anything - the engine might be a bit lame, but in a BX it's still going to be impressive - but there is much more to think about than you're aware of, and worrying about things like radiators kinda shows you don't know where to start.
Like I said, really not mean to be a dig of any form, but if you start spending money on this thing without knowing what you're doing you're going to lose it.

Best of luck though!
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Re: BX 2.0 CT Turbo!

Post by citsncycles »

Whatever you do, you want to try to make sure the shell is not modified. They've tightened up a lot over the last few years, to the point that if you want to go by the book, any changes whatsoever to the shell means putting the car through IVA and reregistration, at a cost of several hundred pounds.

I'm not a big enough expert on the individual components to give specific advice, but as a starting point you want to aim for gearing similar to that in the gearbox originally fitted to that engine. Slightly higher is good for economy, and slightly lower for acceleration, but don't deviate too far - gearing is a compromise and too far to one extreme or another will make for a poorer car overall.

The Megasquirt system mentioned previously is a favorite with the 2CV tuners - there are several 2CV's out there running Electronic ignition and EFi, all of it programmable, some even running biofuel this way and putting out a reliable 20% power increase. Without a complete donor vehicle to rob all the electonics out of, trying to fit the factory system for the engine into the car is going to be tricky at best, and will lead to issues down the road - at least with the aftermarket system a specialist will know what he's looking at when tuning it or tracing a problem.

I've not tried it but have been told that you can graft the Xantia LHM pump and pressure regulator system into a BX, with the result being a system that builds up pressure quicker and is less prone to pressure drop out in use. Cooling should be one of the last things to think about, with plenty of after market competition radiators etc. available off the shelf that can be made to fit. With the extra power compared to most of the original range, I'd go for a minimum of valver brakes.

As for the donor, I'd look for the best shell possible and ignore the rest - with the mechanical modifications you want to make, you may aswell go for your favorite interior, equipment and exterior trim too, and build your ideal car from a bare shell up!
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Re: BX 2.0 CT Turbo!

Post by mat_fenwick »

Kitch wrote:suspension ECU inputs (and outputs to it)
Hmmm, that makes things more complicated - it's one thing trying to fool an ECU with fake fixed signals, but presumably with the suspension it will expect to see some kind of a response when it changes an output.
you can graft the Xantia LHM pump and pressure regulator system into a BX
Vanny would be the one to ask about that, as he did that several years ago IIRC.

Oh and Kitch, when can I start? :)
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Re: BX 2.0 CT Turbo!

Post by Tim Leech »

Kitch wrote:It really doesn't like you've thought about this Tim.

Diesel gearbox.....so you want your car to be doing about 4500rpm @ 70mph? Xantia ECU.....I'm not gonna make a third post on stand-alone ECUs, but you are entering a world of hurt with the Xantia gear.

It's not meant to knock you or anything - the engine might be a bit lame, but in a BX it's still going to be impressive - but there is much more to think about than you're aware of, and worrying about things like radiators kinda shows you don't know where to start.
Like I said, really not mean to be a dig of any form, but if you start spending money on this thing without knowing what you're doing you're going to lose it.

Best of luck though!

I didnt Kitch your right, I was sat on eBay the other day, saw a complete engine and box for sale, starting bid £100, its local and the vendor has good feedback, I put in a cheeky bid of £100 and never thought anymore of it, low and behold I win it, so now I need to decide what to do with it, maybe it will sit in my lock up for years, who knows.

A BX TD gearbox runs at 25mph per 1000rpm which would suit me as I dont want a screamer. Ive looked online, theres been half a dozen 205 GTi transplants without too many tears, and a BX engine bay is bigger, they have used a mix and match of 205/309 parts and have had stunning results. I know it wont be easy or cheap and I will need to involve others and pull on experience, hence why I am here.

Ive had mixed reponses about ecu's etc, some say stick to an early keypad immobiler type xantia and it wont be too hard, others like yourself say junk the lot and start again! Confused.com!
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Re: BX 2.0 CT Turbo!

Post by Vanny »

mat_fenwick wrote:
you can graft the Xantia LHM pump and pressure regulator system into a BX
Vanny would be the one to ask about that, as he did that several years ago IIRC.
Just need to adapt the BX steering rack to take a ~6mm feed. Fortunately most Xantia racks have a pointless adapter on the rack which gives you a starting point. Then just weld a ~3.5mm connector from a standard BX pipe onto the back of it. When i did the first one we just welded the hole lot up (with stick) and drilled a hole back through. You'll need the original Xantia pump to pass pipe, which has several flexible sections (or make up a new pipe from scratch).

You cant (to my knowledge) fit a BX pump onto a CT engine, partly because there is no take off on the cam, and partly because I believe the ML cog box doesn't have the holes for the bolts.


If you use an ML gear box, how will you shift the gears? The linkage arrangement is different, and most are cable operated now, which means you need a different gear lever, cables, gearbox bracket etc


If you've got the money you might have to consider one of the beefed up Pug Sport rally BE3 gearboxes, they might take the strain.
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Re: BX 2.0 CT Turbo!

Post by Tim Leech »

Hi Vanny, the HP pump on my car runs off the bottom pulley.
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Re: BX 2.0 CT Turbo!

Post by Vanny »

which car Tim, you've completely lost me. The TCT will have a twin out pump on the front of the engine, totally different mounts to any bx, you'll struggle to get a bx pump on the front. it wont go on an ml box, no holes, no drive, so you rather need to keep the twin out xantia pump, getting rid of the fdv and needing a little plumbing. Its relatively straight forward on the plumbing side, keeping a xantia twin pump on a xantia engine.
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Re: BX 2.0 CT Turbo!

Post by Tim Leech »

ahh ok, I was assuming I could just bolt the existing pump and alternator arrangement (BX 16 petrol) to the XU10....
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Re: BX 2.0 CT Turbo!

Post by Mothman »

Tim,
if you want to go fast, buy a valver, it will cost you less than you are going to spend on a Xantia/BX transplant in the long run and hold onto the Xantia engine and gearbox you have just bought which you should keep for a while and sell for a profit.

Madness, you should think otherwise unless money is not an option.

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Re: BX 2.0 CT Turbo!

Post by Kitch »

In fairness the way a valver goes fast is different to the way these (would in a BX) go fast.

The valver you have to drive the arse off of. It's designed for getting by the scruff of the neck and abusing hard. The CT is the opposite, it's more like a diesel. No real driver reward like a decent petrol lump, but the upside is effortless speed. Even in something as heavy as an Activa you can make quick progress without even thinking. Not exactly the driver's choice, but in a BX shell some fun would be brought back purely by the in-gear speed I would think :lol:
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Re: BX 2.0 CT Turbo!

Post by Vanny »

Mothman wrote:if you want to go fast, buy a valver
I get the distinct impression Tim isn't doing this to go fast. In fact i'm quite sure if he wanted fast he'd just jump in a golf GTi and punish it. I imagine this is much more about the engineering challenge, and if time isn't an issue, then there is plenty of opportunity to learn about all the pitfalls and get the job done right.

Frankly Tim, i think your mental for even trying it, but then i've done much madder things with considerably less knowledge about cars than I have now! I hope you stick with it, and make a good job of it, as it will seriously tempt me to do the same!
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Re: BX 2.0 CT Turbo!

Post by Tim Leech »

I will stick with it, watch this space guys! Ill be checking in and giving progress updates.

I dont want a 16v, had one, wasnt for me, i want a stock looking sleeper that can cover mileage at speed in relaxed comfort.
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Re: BX 2.0 CT Turbo!

Post by BX Bandit »

My advice Tim, for what it's worth. I've considered heavily the option of a 2.1 conversion in my TD, and given near identical engine blocks I was surprised that there was more to it on investigation than met the eye. I will still do the project, but after I already spent money on what I thought was a suitable engine block, it didn't turn out to be suitable in the end. What I'm trying to say is, that whilst you've clearly given it a lot of thought and researched it on the internet etc, little things may catch you out and you may loose quite a bit of cash if you're not careful.
A 2.1 conversion is not straight forward and you are trying something that's quite a lot more involved.

The ML5T box, like Kitch said is bloody heavy, but also it has a differently splined diff and so you wont find drive shafts to fit (trust me - I've tried).
Some later BE3 boxes or I think early BE4 boxes came with a stronger diff on some models (the 110 hdi models I think but not all of them!) These stronger diff'd boxes take a shorter n/s drive shaft so you need to be diligent in finding the right one.

I would also take the advice given about gear box ratios (i.e. use as close to what was matched to the original engine - allowing for the BXs (probably) smaller wheels) Again, I know 1st hand and the outcome wasn't right.

You are clearly determined to go ahead and do it and fair play to you, but there is some sound advice on your thread here and I get hints of you being blinkered to it somewhat, e.g. your choice of fitting a TD box: it won't suit. Don't forget it's not just gear ratios, but the diff/crown wheel pinion ratio too. That said, you learn more by making mistakes, so if you're in it for the learning process too, then why not fit the TD box just to see.

Good luck
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Re: BX 2.0 CT Turbo!

Post by citsncycles »

I just remembered some of my experiences swapping gearboxes. Many years ago I bought an AZU van that had been modified by the previous owner. Among other things, they'd replaced the original 425 egine and box with a dyane 602 engine and a 2cv4 box. It would beat far bigger vehicles off the lights, but the engine was screaming at 65-70mph and I suspect I would have blown it up if the gearbox main shaft bearing hadn't let go big time after a week, punching its way out the back of the box.

Working on the theory that matching components was the best thing, I found and had rebuilt a Dyane 6 gearbox, which worked well until you hit the slightest headwind, at which point the extra wind resistance of the van body meant you had to drop into 3rd gear at 50mph.
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Re: BX 2.0 CT Turbo!

Post by Tim Leech »

Thanks for the advice, its all appreciated. Regarding the TD gearbox/diff etc I may be being daft but I cant fathom why if its bolted to a petrol instead of diesel it will alter the ratios. As the petrol engine will rev higher I assumed it will give a higher top speed?
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