Xantia Activa lack of performance

Post by **CitroJim** » 14 Jun 2008, 21:43

Indeed a dump valve may well help Kev, certainly as you can sometimes hear a bit of flutter when really caning it as you shut the throttle. Interestingly, although no Xantias fitted with the CT engine had a recirc valve, the same engine fitted into the Pug 406 Executive did. The Xantia has the ports there for it, just blanked off. Trouble is, that model of 406 is rare and finding one in a scrappy might be nigh-on impossible.

I'd go for a recirc valve rather than a dump valve personally; you dont want to go round sounding like a Barryboy in your Activa now do you? Destroys the Q car image a bit....

KevMayer · Post by **KevMayer** » 14 Jun 2008, 22:05

The dump valve on my Activa is made by Bosch.

It was fitted with a hose leading the outlet to atmosphere and it made a woosh sound. But, I soon realised it is a recirc valve and I've now modified it's connection to feed the outlet back into the air inlet ducting.

It doesn't make that embarrassing woosh sound any more.

cheers, Kev

XantiaMan · Post by **XantiaMan** » 14 Jun 2008, 22:33

KevMayer wrote:Going back to Activamadness's problem, It sounds like a classic case of turbo stall as the throttle butterfly closes.

You accelerate hard and lift off to change up. As you lift, the throttle closes and trapped boost with nowhere to go can cause the turbo to stall. It then takes a while to pick up when you accelerate again.

A dump valve could help. This will keep the turbo spinning. I have one on my present Activa and it seems to keep up the momentum better than my previous Activa which didn't have one.

Cheers, Kev

Not entirely true, lag can be often be increased with an atomospheric dump valve.

Impellor flutter or compressor stall often incorrectly called wastegate chatter does no harm to a turbo running less than 20psi. In fact i know of people running up to 30psi with no dump valve and no turbo issues.

I've tried all sorts of atmo DV's on my own car and apart from the noise, offers no performance advantage at all. In fact i am going to be removing the DV from my car next week because the difference in lag between the gears is very noticeable.

When the boost is dumped to ATMO, the boost hoses are no longer pressurized, with no dump valve, the still spinning turbo tries to keep some boost in the pipes and in doing so, creates that distinctive noise.

The ideal scenario is a recircluating dump valve, which reduces the pressure on the impellor blades whilst still keeping some boost pressure between gear changes. The downside is, they tend to get the air a bit hot, but its the best type for a road driven turbocharged car.

Dont want anybody thinking a HKS DV will suddenly transform their car by fitting it!

Reading a little further on its interesting to see the Activa did not have a recirc DV as standard. I wouldnt go to the hassle of fitting a atmo DV as you would potentially lose performance.

Does anyone actually know how much boost the Activa runs?

Gareth

Post by **CitroJim** » 14 Jun 2008, 22:54

A very interesting read Gareth

Puts a bit of a new slant on things I'd never considered and not seen written but it makes some good sense when you think about it. On a diesel a DV is questionalbe anyway due to there being no throttle butterfly.

XantiaMan583 wrote: Does anyone actually know how much boost the Activa runs?

Somewhat less than 1 Bar. About .8 tops I think and it'll be modulated by the ECU. If you try to up it above a Bar, the ECU will chop it back and light the Engine Management Light

There's not a lot of point in trying as the Activa turbo has a very small A/ ratio and is a tiny little thing. About a Bar is all it is good for really. As it is, it is running very close to the edge of its comfort zone if you do a few calculations on it.

The turbo on an Activa is purely there to give the engine it's Constant Torque (CT) characteristic and not for outright performance. It does this very well and has more of a characteristic of a diesel engine at low to medium revs and in fact pulls similar gear ratios to my 2.1TD.

As an aside, the CT engine is a bit more economical when being driven with a bit of boost on. I guess it scores from the much improved Volumetric Efficiency with the turbo spinning. Although it has plenty of low-down grunt, it pays to keep it up the rev range a bit. Fuel consumption suffers in my experience if you don't keep the engine spinning freely.

Activamadness · Post by **Activamadness** » 16 Jun 2008, 07:40

Many thanks to all who have suggested possible causes to my activas intermittent performance.
Firstly, the latest on the car, is that it is languishing on the drive, immobile.
This is due to a poor design, and my stupidity, mainly the latter I fear!
It was all going to plan, and I was removing the breather thing that Richard posted the link about drilling a small hole in, to improve engine breathing.
This thing, its name I dont know either, is held on with hose clips designed by satan, (those nasty clip together things) and as I was struggling to unclip them, I leant on the fuel rail, and broke off the plastic fitting, attaching one of the fuel pipes.
Hence the car is now immobile, as where do you get another fuel rail on a sunday evening? (If anyone has one, or knows of one, I will gladly buy it off them!)
Anyway, prior to this happening, I had taken the pipes off the boost actuator, and blown down them with an airline.
Two are completely free, but the one that faces horizontaly, and to the rear of the car, will not let any air through it at all- is this right? I dont know where it goes either, as the bulb went on my lead light just at the critical moment!
Also, when disconnecting the charcoalcannister pipe from the throttle body, I noticed that the pipe that protrudes from the throttle body, that the hose clamps onto, had some movement in it, is this normal? Again thwarted by the lack of light to investigate furthur!
If anyone can help please do, I am having to drive an asthmatic peugeot 106 this week now, for my sins!
Jon

Post by **CitroJim** » 16 Jun 2008, 12:21

Activamadness wrote:I leant on the fuel rail, and broke off the plastic fitting, attaching one of the fuel pipes.
Hence the car is now immobile, as where do you get another fuel rail on a sunday evening? (If anyone has one, or knows of one, I will gladly buy it off them!)

I can supply you one Jon. I've sent you a PM.

Activamadness wrote: Also, when disconnecting the charcoalcannister pipe from the throttle body, I noticed that the pipe that protrudes from the throttle body, that the hose clamps onto, had some movement in it, is this normal?

Absolutely normal. It worried me at first but they're all like that sir... You'll find they tighten up under vacuum when the engine runs.

Post by **CitroJim** » 16 Jun 2008, 21:15

Jon,

If this problem persists, it might be worth changing your fuel filter. There was a case on here recently where a fuel filter was to blame although the symptoms were that the car would not rev. It had broken up inside.

If you wonder where it is (took me a while to spot it

) It's attached to the front side of the fuel tank on the drivers side. Look under the sill and you'll see an alloy cylinder. Connections are via the same sort of connectors as on the fuel rail.

Activamadness · Post by **Activamadness** » 17 Jun 2008, 08:16

Thanks Jim,
I will certainly change it, I hadnt thought of fuel starvation being a possible cause!
Hope to goodness I dont break that too!

Jon

Activamadness · Post by **Activamadness** » 27 Jun 2008, 19:10

Success!
I have managed to fix my asthmatic activa, well 99% fix it anyway
I got it up in the air, and had a look at the turbo, and it became apparent what the matter was.
The circlip that holds the actuator to the wastegate was mangled, and thus allowing the wastegate to become stuck open, effectively giving me no boost.
I took it off, and cleaned up the pin on the wastegate, put a new circlip on, and took it for a spin.
Its like a different car, I can only deduce that I was at best, only getting partial boost, at times!
It still has a slight misfire, am going to fit the new lambda sensor when I am feeling stronger, and see if that does the trick
Many thanks to everyone for their input
Jon

Post by **CitroJim** » 27 Jun 2008, 19:42

Excellent news Jon

andmcit · Post by **andmcit** » 27 Jun 2008, 20:32

Mine has a slight intermittent hesitation that I guess by definition is a misfire.

I must confess all I've done is drive it and it does certainly go well when all
said and done 95% of the time although this issue is always lurking waiting
to show up at low speed sharp accelerations.* <edit - not EVERY time; just
the most embarrassing inopportune moments!!>

I'm led to believe this is a 'quirk' on Activae and something you just have
to get on and live with. Is this correct? I don't fancy the whole financial
chase-round the engine bay!!

I don't have any hesitation issues on either Xm 2.0i CT turbos mind!!

What would be the best fix or at least a course of diagnosis/action?

Andrew

Activamadness · Post by **Activamadness** » 27 Jun 2008, 20:41

Hi Andrew,
I have gone down the plugs, filters, (fuel and air) route, and it was suggested to me by Dickie G, that his misfire was cured by changing the lambda sensor, I cant think of much else it could be, and certainly bow down to his knowledge of Citroens, will post the outcome!
Jon

KevMayer · Post by **KevMayer** » 27 Jun 2008, 22:45

Andrew,

When your Activa hesitates do you see the yellow engine management light come on ?

Kev

XantiaMan · Post by **XantiaMan** » 27 Jun 2008, 22:54

Activamadness wrote:Success!
I have managed to fix my asthmatic activa, well 99% fix it anyway
I got it up in the air, and had a look at the turbo, and it became apparent what the matter was.
The circlip that holds the actuator to the wastegate was mangled, and thus allowing the wastegate to become stuck open, effectively giving me no boost.

If the wastegate was flapping about you would definatly have no boost at all! its possible your misfiring could be related to overfuelling and contamination of the 02 sensor. Personally if it was me i would still get the boost gauge and check its boosting as per original as with age, it will drop.

andmcit · Post by **andmcit** » 28 Jun 2008, 00:50

KevMayer wrote:Andrew,

When your Activa hesitates do you see the yellow engine management light come on ?

Kev

Hi Kev, no, no I don't and have made a point of looking for this to see if
the AEi is having a bit of a mare. There's no harshness or poor running,
just feels like you're accelerating and a gear is missed like it wasn't
engaged but then picks up. I could complain about poor fuel economy
but then isn't this just another Activa characteristic!!

It's bad, but
not THAT bad...

Andrew

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