xm conversion[ maybe]

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crooser
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xm conversion[ maybe]

Post by crooser »

the intercooler on the 2.5 xm diesel is watercooled.bearing in mind the high water temperature when running i can't see the air being cooled very effectively.does anyone have any thoughts about replacing the intercooler with the aircooled unit from the 2.1 td? would i be right in thinking that it would be more efficient? i should add that i don't proffess to be as clever as citroen designers.
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AndersDK
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Post by AndersDK »

How is the watercooling fed from the cooling system :
Is it a cylinder head tap, like the heater matrix ?
- or is it a tapped from the cooled side of the radiator ?
I suspect it's more to try get a constant air temperature, than precisely effective cooling. The compressed air from the turbo would be rather hot with a warm engine.
Guess this is a topic for our turbo "head" members.
crooser
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Post by crooser »

Anders.as far as i can make out the cooling comes from a half radiator that is mounted in front of the main radiator.the water supply comes from a tapping halfway down the main rad.
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noz
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Post by noz »

crooser,
The manual calls the intercooler an "water to air heat exchanger". To quote the factory manual:
"The Water to Air Heat Exchanger cools the compressed air. The inlet temperature borders on 60 DegC (in normal driving conditions).
Advantages (by comparison with an air to air heat exchanger):-
1) inlet air cooling improved for a broad engine speed range
2) reduced size of exchanger"
The water which feeds the intercooler comes from the outlet of the half sized auxilliary radiator located in front of the larger normal radiator. The water leaves the thermostat housing on the engine block and is conveyed to the top connection on the main radiator. About half way down the inlet tank there is a small connection which is joined to the auxilliary radiator inlet by a short length of hose. The water is further cooled by the air which passes over the auxilliary radiator first. The water leaves the bottom connection of the auxilliary radiator and is piped to the inlet connection of the intercooler. From the intercooler the water is piped back to the common return connection with all the other ancillary hoses.
Interpreting the obviously translated (from french) text in the manual, I suppose what they were trying to say was that in addition to the reduced size of the intercooler (this makes perfect sense consistent with the physics of heat transfer co-efficients etc and the complete and utter lack of space under the bonnet of a 2.5 TD) the water cooled intercooler gives a much more consistent air outlet temperature for varying external ambients and varying engine loads.
Whilst, on the surface, an air to air might seem more sensible, I think the slight reduction in cooling from an air to water is more than compensated by temperatur consistency and space allocation.
Would the 2.1 intercooler fit under the bonnet of a 2.5 anywhere? Could you get a flow of fresh cool air past it?
cheers
noz[8D]
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Post by Stempy »

Perhaps you could plumb it into the aircon, that would really cool the charge.
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Post by crooser »

Noz.i dare say i could getit to fit the same as the 2.1 but whether there would be enough air flow would be debateable as the air would have to pass through the a/c rad first.i know this setup works on the 2.1 but i suspect the 2.5 is less tolerant of high temperatures and it needs every last drop of cooling air.
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Post by neilsxm »

hi all
i also wondered why they had done this and took some tempreture readings of my own and the intercooler only runs at around 60 degC
but what i was thinking of doing is using the waterbottle and pump off the headlight washers and a spare small oilcooler that i have in the garage and piping it up so it only gets cold water pumped round it i'll let you know if there is any improvment
---neil---
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Post by NiSk »

Or you could try injecting water into the turbocharged/intercooled air -as Surbaru do in their high performance (unfortunately petrol) boxer I'm currently translating . .
//NiSk
xm-2.5td
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Post by xm-2.5td »

Guys,
How do you actually check if your car has intercooler or if the intercooler is functional at all?
I have a ’97 exclusive model 2.5 TD XM and I’m having problems with the top speed.
For now I was suspecting that my non-functioning CC maybe got jammed or something …but now….
Also, 20 days ago I took car for maintenance at my local Citroen car dealer and they have downloaded engine codes but no fault was found. For the computer…my engine is working just fine, and my top speed 160 m/h?????
I’m sure police will be pleased…but I’m not.
Anybody with some suggestion?
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noz
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Post by noz »

XM,
The intercooler is fitted just behind the radiator and in front of the header tank. Follow the large plastic or rubber piping to the front of the car and the long plastic container is the intercooler.
To discover if it is working, measure the air temperature before and after. The temperature after should be lower than the temperature before.
Although possible, it is unlikely to be the cause of your problem. Try starting from cold and try exceeding 160km/h when the radiator circuit is still cold. If you exceed 160 then yes you have an intercooler problem but if the problem remains then it is something else.
The ECU has many safety functions built in for engine protection. When I first got my 2.5 the turbo wastegate was stuck closed. This meant the turbo produced full boost all the time. The manifold pressure was 2bar! The engine protected itself because the MAP sensor saw the increase in pressure and told the injection pump to throttle back.
There are too many possibilities to list here but try measuring the resistance of each of the sensors feeding information to the ECU and compare with the readings from the manual. Unfortunately in my experience there can be many faults with the injection system which do not appear as coded in the code reader. The turbo boost problem did not show as a fault code.
When you get to 160 what happens? Does the engine continue to behave but just not produce any more power? Does the engine cough or miss?
Check the throttle cable form the pedal to the potentiometer on the offside (RHD) inner wing. Make sure you are getting full travel distance of the cable.
Injector condition could also be a factor but unlikely if the rest of the car's performance is OK.
What does the fuel consumption computer say. Do you have smoke from the rear of the car? If no smoke and good consumption then the ECU is limiting the power.
I hope this has helped but to make a more accurate diagnosis, more information is required.
cheers
noz[8D]
xm-2.5td
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Post by xm-2.5td »

Noz, thanks for this info.
Regarding performance of the car...car behaves normally all the time, except, sometimes I have a feeling it’s not giving full boost when I’m overtaking other cars. I usually have to put it in third gear to get good wind in my back.
But consumption is so good I can’t believe my eyes when I get to gas station – on the open road – around 6 L /100km, in town driving around 8.5.
No smoke at any time from exhaust…going in first gear or in fifth…up or down the hill…car is not producing any smoke, that’s why I can’t figure it out what is going on.
On the highway, when I reach 150-160km/h…car behaves just fine…normally…no rattle sound or any other sound…you just can’t get over 3300 RPM’s and that’s all.
Now,as I said, my Cruise control is not functional, and it was not working even when I got the car so I have a feeling that ...that one might me also reason for this. What do you think, is it possible?
Thanks !
I.
crooser
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Post by crooser »

mine uas the same symptons sometimes.noz is right when he mentions the inbuilt safety precautions of the ecu. a high water temperature localised around the sensor could also cause the ecu to cut back on fuel.when this happens to me my max speed is 80mph.i take my foot off for a few seconds to let things cool down and then it's back to normal.
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Post by Doc »

I know this is a long shot but when I first got my 1992 XM 2.1 TD it too wouldn't rev over 3200 rpm. The cause of this was a holed pipe that runs from the intercooler to the injector pump. Because vibration and time had worn several small holes, the air in the hose was at insufficient pressure to activate the fuel enrichment device on the pump. As no extra fuel was being injected the turbo couldn't spin up because there was no increase in fuel burnt/exhaust flow. As the 2.5 uses an mechanical pump albeit electronically controlled it may be worth a look for a similar hose. Incidentally my local Citroen garage didn't have a part number for this pipe so I eventually used petrol fuel injection hose. A temporary repair can be effected by using hose repair tape.
Doc
xm-2.5td
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Post by xm-2.5td »

Just to tell you that I finally found reason and solution for my problem :)
Remember my XM couldn't go over 150-160?
Well, reason for that was faulty sensor.
In my local garage they found that one of the sensors is not doing it's job properly and told me that I need to replace it but since they didn't had it on stock I ordered it.
Came back home and I couldn't wait so I went to my friends garage and we decided to take it apart.
Small quadrant peace, which was mounted on top of engine, was disconnected from pipe giving it pressure from turbine. And that was whole problem :))))
Well, the peace that was attaching pipe to sensor was broken but that didn’t stop us.
Twenty minutes after, I was on highway doing test ride at 200 km/h.
Guys, after this, engine feels like totally something else.
Driving it gives me such a pleasure and even consumption, strangely low as it was, went even lower after this.
Well, this was just in case someone has a similar problem.
I.
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noz
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Post by noz »

xm-2.5td,
I'm interested in your problem. From your description I can't understand which sensor you mean. Can you please describe in more detail eg
exact location
shape
size
colour
name?
how many wires
how many tubes
etc etc
I might have a similar problem so your reply would be appreciated.
Thanks
noz[8D]
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