CitroJim's Citroens

The place to show off and tell us all about your XMs (or even other cars). Should it be a big project, or just some general pics, start your thread in here.
Dieselman
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Re: CitroJim's Citroens

Post by Dieselman » Thu Jul 24, 2014 8:26 pm

I can't work out how they work without bleeding off boost in he manifiold. Do they have a regulated jet before the bleed screw?
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Re: CitroJim's Citroens

Post by CitroJim » Thu Jul 24, 2014 8:48 pm

Dieselman wrote:I can't work out how they work without bleeding off boost in he manifiold. Do they have a regulated jet before the bleed screw?
They have a spring-loaded ball on a seat Will and a small vent to the atmosphere. The spring tension is adjustable and that acts to control the maximum boost. the ball and spring acts as a calibrated leak.

Well engineered ones work well enough and minimise, as far as they can, boost spikes. Cheap and crude ones are not so good in this respect. proper electronic ones are a lot better in limiting spikes.

The TCT ECU limits boost to 1 bar and anything over this will cause an over-boost fault and light the EML. The standard TCT electronic boost conrol is 'modulated' in the same way as the old MG Metro Turbo was and acts to smooth and flatten the torque curve across the rev range. Using a manual valve allows a bit more unregulated boost and this a bit more life and pep out of the engine.

A standard TCT is quite flat but very torquey across its rev range which is great for an autobox in an XM. Planting your foot produces no drama, just a steady increase in torque.

Pop a manual boost controller on and nothing much changes until about 3,500 rpm and then it takes off and flies as the boost comes on. It then goes like a rocket right up to the rev limiter 8-)

The trick is to set the boost so that the boost never exceeds 1 bar and thus faults the ECU.

A proper electronic boost controller would do a slightly better job as it's then possible to run nearer the 1 bar limit.

I know and drive another Activa on occasions that has a tweaked ECU with the 1 bar limit increased. That one runs well in excess of a bar and goes like several scalded cats. It's quite laggy but once the boost comes in it's time to hold on tight and enjoy the ride!
Jim

'98 Saxo
'95 AX
Three bikes - Road, Aero and TT

Ex- owner of several XMs and many Xantias!

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Re: CitroJim's Citroens

Post by Dieselman » Thu Jul 24, 2014 9:07 pm

The TCT is badged as it means Turbo Constant Torque.

I don't see why a car with a raised maximum boost should be any more laggy. The only way that should happen is if the turbo is larger, so has greater inertia.
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92 3.0 V6-24.Rp 5713 EXY Black
92 2.1SD M.RP 5685 ENT Blue Sideral
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90 2.1SD M.RP 5049 EJV Mandarin
92 2.1SD A.RP 5698 EJV Mandarin
94 2.1SD A.RP 6218 ERT Triton Green
91 2.0SI M.RP 5187 EWT White

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Re: CitroJim's Citroens

Post by CitroJim » Fri Jul 25, 2014 3:17 am

Dieselman wrote: I don't see why a car with a raised maximum boost should be any more laggy.
The TCT is laggy anyway Will. It's a well-known characteristic and all TCTs I've had (a good few now) demonstrate it. Maybe it does not show up so much on a TCT married to an autobox in an XM but in an Activa it is very noticeable, especially when first driving an Activa after driving around in something that's normally aspirated.

Adding any form of non-standard boost controller makes no difference to the lag one way or another.

It's not a huge problem as long as you're aware, especially at busy roundabouts...
Jim

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Three bikes - Road, Aero and TT

Ex- owner of several XMs and many Xantias!

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Re: CitroJim's Citroens

Post by CitroJim » Fri Jul 25, 2014 1:58 pm

Springer Spaniels are big tarts :)

Kyra has been as good as gold with me but is terrified of my two grandfather clocks. Last evening we sat down to watch a bit of TV and she curled up under my footstool. One of the clocks struck 8 and she flew up, banged her head on the stool, ran to the clock, looked at it menacingly and barked. Then the other clock struck. One very confused and bewildered dog.

This was repeated at 9PM.

Earlier we visited Val and she has a decoy cat screwed to the side of her garden shed. Kyra spotted it, thought it was real and spent a good few minutes wildly jumping at it in a desperate attempt to catch it :lol:

She either loves or hates cats as none are safe from her. She spots a cat and the chase is on!

She's always been trained not to come upstairs and is good at obeying the rule but no way was she going to sleep with those damm clocks last night so she crept upstairs and slept with me. All very quietly and apologetically... She was good despite she snores and has dog's breath!

I'm happy too as unlike cats I find I have no allergy to dogs although she has just been clipped and is distinctly short in the coat department. If a dog can sleep with me I see that as a good test.

She's been out in the Activa today and approves. The boost has been tweaked just a tad higher again :P

Spaniels.. You just have to love 'em 8-)

I'm going to miss her when she goes back to her rightful owners tomorrow. Never thought I'd say that about a dog...
Jim

'98 Saxo
'95 AX
Three bikes - Road, Aero and TT

Ex- owner of several XMs and many Xantias!

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Re: CitroJim's Citroens

Post by captainhaddock » Fri Jul 25, 2014 5:13 pm

Better get a proper hoover later to clean up the Activa:) Get a dog JIm, good idea! :) Try and blow some compressed air in a tyre or whatever and see what the spanie does? Capt'n here goes utterly wild with that. Even worse with a electric fly zapper...that we really need here now in the country side with zillions of flies.. :) Fixed an XM problem today too!

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Re: CitroJim's Citroens

Post by CitroJim » Sun Jul 27, 2014 3:47 am

Yes, I think I will get a dog as soon as the time is right Jaap :D I really enjoyed my bit of dogstitting :D
captainhaddock wrote:Fixed an XM problem today too!
Excellent :D What did you fix?

We did a heck of a job yesterday. We replaced the motor-driven heater flaps in a Pug 407. It is a very common fault on the 407 and entails complete dash removal. They are made of poor plastic and snap.

That was a lot of fun and took us all day but in between we did replace part of my garden fence.
Jim

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'95 AX
Three bikes - Road, Aero and TT

Ex- owner of several XMs and many Xantias!

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Re: CitroJim's Citroens

Post by captainhaddock » Sun Jul 27, 2014 10:21 am

What is it with PSA and certain parts I wonder. Motor driven heater flaps that can't be reached, Xantia heater matrixes hidden like it's not supposed to be ever found, crap really :)

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Re: CitroJim's Citroens

Post by citsncycles » Sun Jul 27, 2014 10:33 am

I think all cars have a bit of that in them though - Bedford CF's where No.3 spark plug is against the bulkhead, Vauxhalls who's valve trains sound like a bag of nails when correctly set up, Montego's and Rover 820's that rot their sills out where the sunroof empties into them because they hold water on whatever side is lower at the time, BMW's where you need to remove the engine to change the water pump....
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Re: CitroJim's Citroens

Post by CitroJim » Sun Jul 27, 2014 10:56 am

Ahh, so it's not only PSA that benefited from the expertise of the XM design team then :lol: :lol: :twisted:

It really makes you wonder why they do what they do. Surely they must realise it's total muppetry or is it all to help with selling new cars?

How many, realistically, are going to fork out £1500 say to fix a six year old 407 with a duff heater? They're more likely to scrap it and buy a replacement car, most possibly another PSA model...

So for the company I guess it makes perfect sense :evil:
Jim

'98 Saxo
'95 AX
Three bikes - Road, Aero and TT

Ex- owner of several XMs and many Xantias!

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