Turbo kick

[jipsom]

Hi all. Question -

Just got my 2.5 back with re-welded manifolds, repair to the exhaust and a solid pipe (no BOV, though). It seems to be running a lot smoother, which is nice. However, the turbos now kick in at 4000 rpm rather than 3000, and the power curve seems a lot softer; there's nothing like the kick-in-the-arse I used to get.
Why would that be?

It's hard to say if it really feels any slower. I don't think so - just a more pedestrian delivery of power. I've also noticed I'm changing up around 1000rpms later than before.
I think my familiarity with the speed (had it 6 weeks now) is also a small factor.

[turnbaugh]

I had a turbo lag problem with mine. It took forever to find but it turned out to be improperly installed wastegate actuator rods. I had a small constant leak in one and a big leak in the other. I used to not build positive boost until 4000 RPMs. (It took that much to build enough volume to overcome the leak). Now I get positive boost as early as 2000 under some load and gear combinations.

Could also just have a leak in the turbo piping. A good smoke machine will find this easily. Do you have a new whistling sound or a sucking sound that you didn't have before? Could indicate a leak. Dean

[jipsom]

Cheers Dean. Actually, your problem may explain why my car runs so differently. Before, with the manifold cracked (and leaking, I presume) there was a noticeable surge of thrust at 3000 - 3500 rpms. The garage did explain to me that the emissions from the manifold were confusing the lambda sensors, causing the ECU to run the engine too rich (don't quote me on that) causing a slight lag. Maybe the reduction of the lag has in turn reduced the kick. This would also explain why it's smoother between gearchanges as well.
Ah, it's all making sense...I think.
R

[matt_fp]

Rich,

On a 2.5 litre car without the power upgrade/EBC peak boost pressure should be around 0.75bar, with the power upgrade it should be 0.9bar with a slight overboost condition ontop of this.

Positive pressure should be showing on the gauge before 3000rpm.

If the above isn't the case then I would suspect the actuators may require inspection/adjustment.

Best Regards
Matt

[lucozade]

on the subject of noisy turbos I keep getting a re-occuring problem with one/both of mine.

Basically under hard acceleration I get a rattling/whistling sound which is totally different to the normal sound.

I take it to the dealer it comes back fixed. A few hundred miles later same problem comes back.

[jipsom]

matt_fp said:

Rich, On a 2.5 litre car without the power upgrade/EBC peak boost pressure should be around 0.75bar, with the power upgrade it should be 0.9bar with a slight overboost condition ontop of this. Positive pressure should be showing on the gauge before 3000rpm. If the above isn't the case then I would suspect the actuators may require inspection/adjustment. Best Regards Matt

Cheers Matt. I'll check that out.