Xantia ES9 J4 tuning

[svip]

I have a 1998 Xantia Activa V6, that I am very happy with.

This question is about tuning the engine, but it's not because I am disappointed with the engine in anyway, it's mostly because I am curious. I know that some later iterations of the ES9 engine have seen higher break horsepower outputs, German refitting company Carlsson managed to tune a C5 Break engine to 235 bhp at 6k rpm. And Renault's Clio V6 managed a whooping 252 bhp from the same ES9 J4 iteration of the engine.

As such, I am wondering whether the ES9 J4 engine in my Xantia can be tuned? I suppose the obvious answer is yes, but I suppose it's more involved as to how. I get the impression that I cannot fiddle with the ECU to do anything, so it sounds like a mechanical hurdle.

Some brief history about my Xantia in question; I bought it last year when it had 125,000 km on the clock. I've now done about 10,000 since then, because I mostly use it for long trips around Europe and otherwise keep it in a garage. There are still some things to be done (like the classic left rear door rust), but is otherwise in nimble condition. I've done my own slight alteration of its appearance without ruining it (in my view) by giving it OZ Racing rims (R16). I've also replaced its front suspension spheres with XM front suspension spheres for some extra ride comfort without ruining the Activa handling.

[Stickyfinger]

Hello fellow v6 Activa owner....WELCOME

From what I can gather the Carlsson uses only induction and exhaust modifications with the later J engine (vvt), the Clio uses both those but with twin throttle bodies and new heads/valves.
All of which are very hard to achieve due to space in the ACTIVA engine bay.

Images of your car ?

[svip]

This is slightly embarrassing, because I don't actually have that many great pictures of my car. I think it might be my reluctance to take picture of it due to a slightly of patina on it that I intend to fix (in particular its front bumper).

But these two are OK-ish:

[Stempy]

I Have read of ES9's being tuned up to 800bhp but doubt that would last much longer than the quarter mile.

The ECU's can be rechipped but it won't give a huge increase, probably 15bhp max.

http://www.smchiptuning.com/1318/citroe ... 90?lang=en

[svip]

The re-chipping makes me rather sceptical. But even 23 ks as that thingie promises wouldn't be too bad. Although for 350 euros, I'll probably reconsider.

[Stempy]

When I had my V6 Xantia I made a few mods to the airflow and fuelling by polishing the inside of the inlet manifold, fitting a high flow air filter and replacing the flexible hose that feeds the filter box for a more solid open pipe. I also fitted a higher pressure fuel regulator and always used 98RON or above fuel and high spec spark plugs, combined with a freer flowing tail pipe, and it did seem to run very well. I have no idea how much difference it made in reality but the C5 V6 felt slower to me when I traded it in for one, but that could just be down to weight or gearing differences.

[Stickyfinger]

If you read my thread you will see I did some work on the induction side of the car, this has made it a better car to drive being noticeable smoother and responsive on the throttle, I do not know if it added anything however to HP/torque as I changed the plugs/leads at the same time.

Next job is SS Exhaust manifolds and a 3 inch exhaust with a swap out De-Cat section (for MOT days)

[svip]

These suggestions are definitely more interesting. I could see myself doing that. While not asking for a guide (I will look through your thread), I wonder quickly how much it costs for such modifications (ignoring work hours)?

[Stickyfinger]

Only New gaskets, abrasive sheet and Carbide cutters for a Dremel............and TIME !

[svip]

Don't worry, my time is worthless!

[Stickyfinger]

You can see the miss match here as an example on the throttle body before I opened it up

[Stempy]

Can't see it being more that €250 in parts for what I did.

[svip]

I will definitely consider this for later, but for now, I probably won't be doing major changes to my Xantia. My DS is currently undergoing a motor renovation, so I need my money focused on that.

[Mandrake]

When I had my V6 Xantia I made a few mods to the airflow and fuelling by polishing the inside of the inlet manifold, fitting a high flow air filter and replacing the flexible hose that feeds the filter box for a more solid open pipe. I also fitted a higher pressure fuel regulator and always used 98RON or above fuel and high spec spark plugs, combined with a freer flowing tail pipe, and it did seem to run very well. I have no idea how much difference it made in reality but the C5 V6 felt slower to me when I traded it in for one, but that could just be down to weight or gearing differences.

I would second the suggestion of changing the fuel pressure regulator as a quick, easy and relatively cheap (approx £60) modification that will add a noticeable improvement to both foot to the floor acceleration and also improve the throttle responsive under lighter throttle.

The standard fuel pressure regulator is a 3.0 bar return style unit made by Bosch, but by the time they get old and tired (fatigued spring) the actual pressure may be as low as 2.7 bars or so as it was in my previous Xantia V6. (Measure with a fuel pressure gauge connected to the shraeder valve on the right hand end of the rail near the battery, with the vacuum hose disconnected)

Furthermore the tuning of the engine ECU at the factory was done in the days before Ethanol was routinely added to petrol - these days you are running on 5 or 10 % Ethanol, which causes the engine to run leaner than it should. The ECU will compensate in closed loop mode by using the oxygen sensor, thus will run at the correct mixture at idle or during light to moderate throttle cruise, however every time you accelerate hard or even just open the throttle a small amount quickly it drops into open loop mode where the ECU uses pre-set mapping tables to calculate the mixture without use of the oxygen sensor.

It is unaware that it is running too lean due to a difference in the fuel composition so performance suffers. Foot to the floor acceleration suffers and you may notice small hesitations when you suddenly increase the throttle. In the worst case the leaner mixture can cause knocking (which you won't actually hear) which is detected by the knock sensor and causes the ECU to reduce the timing advance which can cause a big loss in power and responsiveness in the mid range. Making the mixture richer again will prevent all these problems.

I talked about this in a bit more detail in my blog:

http://www.frenchcarforum.co.uk/forum/v ... &start=586

A back of the envelope calculation I did a few weeks ago suggested that to compensate for E10 (10% Ethanol) petrol you would need to raise the fuel pressure from 3.0 bars to 3.5 bars, just to get back to the same mixture it should have been on standard Ethanol free petrol! And if you wanted to make it richer than the factory tuning (better performance at the expense of a bit of economy) whilst running on E10 you would need to go as high as 4.0 bars. (I have not heard of anyone running this engine higher than 4 bars so I would not go any further than that)

The only other solution would be an ECU remap which is rather expensive for such an old ECU, whereas raising the fuel pressure is a 30 minute job to swap in a new regulator. (It can be done without removing the intake manifold if you're careful with the vacuum hose and fuel rail link hose)

I replaced the regulator in my previous Xantia V6 with a 3.5 bar regulator and the difference was not massive but it was very noticeable, and I felt it was worthwhile. I used a cheaper after market regulator around the £30 mark but I would not recommend doing this as I had problems with internal leakage in the regulator - this doesn't affect running but prevents the fuel rail holding its pressure when the engine is stopped which can cause problems with vapour lock and difficult starting when hot.

Genuine Bosch regulators that are an exact fit are available in 3.5, 3.8 and 4.0 bars for approx £60. When I can put a little money aside I plan to fit a 3.5 bar bosch regulator to my current Xantia V6 as I notice the same symptoms that the previous car had (although to a lesser degree) until I changed the regulator there...

If you go any higher than 3.5 bars you probably need to replace the in-tank fuel pump as well, they get "tired" when they get old and the volume of fuel the pump can deliver decreases rapidly as you increase the pressure over the design target of 3 bars - it's very unlikely from my own measurements on multiple fuel pumps that an original high mileage pump could provide sufficient volume at 4 bars. (The original pump in my previous V6 could only deliver 60% of the factory spec for litres/hour even at 3.0 bars let alone higher - factory spec was 120 litres per hour at 3 bars, eg 2 litres per minute)

At 3.5 bars you're probably OK with the original pump but I would still verify that it has sufficient delivery - you would put a fuel pressure gauge on the rail, disconnect the vacuum hose to the fuel pressure regulator then floor the accelerator from idle a few times and make sure the pressure stays exactly steady and doesn't sag. If it sags, the pump needs replacing to work at that increased pressure.