8v to 16v conversion

All aspects of tuning,modification and repairs to the BX 16valve.
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Kitch
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Post by Kitch »

jayw wrote: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!
All XU9 petrols are alloy blocked. It's the diesels and later 1.8 & 2.0 petrols that are iron.

16v has over 8v:

Different crankshaft
Uprated oil pump
Improved oilways and piston skirt spray bars
Pistons have cut-outs for the valves
Various smaller components use uprated materials

Wouldn't be too hard to do, but the real question I'd raise is why would you do it? Unless the 16v as a car is hard to find where you are.

Personally if I was going to the trouble of transplanting an engine, I'd fit something that was never fitted as standard. Xsara VTS 2.0 16v, Xantia Activa 2.0CT, XM V6? Otherwise it's just alot of work to end up with a car you could already buy.
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Post by assembled »

Kitch wrote:Wouldn't be too hard to do, but the real question I'd raise is why would you do it? Unless the 16v as a car is hard to find where you are.

Personally if I was going to the trouble of transplanting an engine, I'd fit something that was never fitted as standard. Xsara VTS 2.0 16v, Xantia Activa 2.0CT, XM V6? Otherwise it's just alot of work to end up with a car you could already buy.
The engine would go to BX 4x4 from my signature.
Reading descriptions of various ECU I've found following differences:

Jetronic LE3 (8v pre July 1990) - the most simple. Only fuel is controlled by ECU. All injectors controlled simultaneously.

Motronic ML4.1 (16v pre 1991) - integrated amplifier, has self-diagnostics. Electrical ignition with only HV distributor. All injectors controlled simultaneously.

Motronic MP3.1 (8v from July 1990) - has the "wasted spark" - no distributor. Built in MAP sensor, throttle potentiometer (as opposed to switch in other systems), lambda sensor without catalytic converter. All injectors controlled simultaneously.

Motronic 1.3 (16v from 1991) - injectors are in two banks, lambda sensor, knock sensor.

I wonder would MP3.1 from GTi 8v would work well with 16v engine or would it need some tuning?
1989 BX GTi 4x4
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Post by Vanny »

See if you can do a search of the 205GTiDrivers forum, i'm pretty sure this has been done before.
assembled
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Post by assembled »

Thank you! I will do a search there.
1989 BX GTi 4x4
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Kitch
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Post by Kitch »

assembled wrote:
Kitch wrote:Wouldn't be too hard to do, but the real question I'd raise is why would you do it? Unless the 16v as a car is hard to find where you are.
The engine would go to BX 4x4 from my signature.
Reading descriptions of various ECU I've found following differences:
In that case, your bigger headache will be upgrading the transfer box from cheese to metal, otherwise all a more powerful engine will do is make a mess on a road somewhere!

Plus (and just my opinion here) I think the XU9J4 would really lose its edge having to haul a 4x4 platform around. That's not to say a quick 4x4 BX is a bad idea....far from it. But I think you need to be looking at the turbo engines, either 2.0CT or (if you have a deep pockets) a T16 or XU10J4RS with forced induction. Or, strap a blower to the BX 16v lump, because in standard form, it's not exactly a grunty engine. Power in spades for its size, but no real grunt until you get right up at the top of the rev band, so you end up relying on close-ratio gearing to make the standard 16v go as well as it does. Something you won't have using a 4x4 transmission, which is a fair bit taller as the 1.9 8v has a similar amount of grunt to the 16v, but accessible much lower down in the rev range.
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Post by assembled »

kriskarrera wrote:How much for just 1 please?

Here's the graphs for the official figures for the XU9 engines:

Image
Image
XU9J2 (D6A) is 8v and XU9J4 (D6C) is 16v.

Official service manual gives following for XU9J2:
Max torque: 17.8 m. kg @ 4500 rpm
Max power: 90kW/125ph @ 5500 rpm
Graphs above agree on this.
Looking at them it seems that up to 4500 rpm XU9J2 is only slightly ( up to 5 Nm) ahead, but above that things change in favour of XU9J4. Furthermore, later engine has max 6500 RPM as oposed to 5500 RPM of XU9J2.

If that is correct, giving away 3-5% of torque at low-moderate RPM for 18% max. RPM and 30% max. power increase is rather rational. Though thank you for raising this question - I now know that in the region I like most (2500-3500 RPM) my 8v engine is superior :) Though I think this might be a result of different mapping.

Any additional thoughts?
1989 BX GTi 4x4
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Kitch
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Post by Kitch »

At anything less than 4.5k - 5k revs, the XU9J4 lump is pretty much dead! It's almost like it's got VVC or something.

The later 2.0 iron blocked versions in the ZX 16v and Xsara VTS deliver more grunt, but also weigh more. But using the transmission you are, you'll struggle with anything designed to rev. The 1.9 8v isn't designed to rev, along with the turbo 2.0 engines and the diesels, so those are what I'd be looking at personally.
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