HDI Turbo Lag

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bencowell
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HDI Turbo Lag

Post by bencowell »

Do HDI engines get turbo lag?
Dads dealer says they don't, but I guess he really means that they don't get as much compared with XUD's.
Ben
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Post by sooty »

How are you defining 'Turbo lag'. Explain when you think this is happening?, then we can try and help.
Sooty
bencowell
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Post by bencowell »

We have suffered lack of power, black smoking and once even an inability to climb a driveway in 1st gear.
When the engine seems to lack power, say you have entered a roundabout in 2nd or just set off in 1st, the car will sit with the revs (sounding) just over idling, nothing may happen for the longest 2 seconds of your life and then all hell will break loose, with almighty power.
This doesn't happen every time, dealer has checked the computer twice and tightened the turbo pipe.
Also the engine sometimes seems to lose power for a split second after changing gear and releasing the clutch. This is what I meant by turbo lag.
Until the dealer fixes dads Picasso, I can't even contemplate a C5. Just been driving a Xsara HDI 110, nice engine, and I think it would still be superb in the heaver body of its big brother.
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Post by sooty »

whether or not its a Hdi or the older turbo units, depending how low your revs are as you say approaching a roundabout in second gear, you will not have any turbo boost, hence the black smoke. This where you ask for power, get alot of fuel into the engine with a given amount of air(oxygen). But when the revs go up and the turbo starts to pump more air into the engine with the same amount of fuel, it burns alot faster and gives you power and no smoke. This is brief explanation.
The other thing to check is your air filter, it maybe partly blocked in need of changing, not allowing enough air when the turbo is not pumping (at low revs the engine has to suck its air).
As for the turbo lag as you say when changing gear, all turbos petrol or diesel suffer from this, its where you let your throttle off hence the turbo slows down, then you put it down again and the turbo has to build its speed up again to pump.
The only possible fault maybe in one of the sensors for the computer, ie Turbo pressure, Air flow meter etc. These engines use a common fuel rail, ie one pump for all 4 injectors and a soleniod on each injector to fire them when required.
Sooty
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Post by RichardW »

What you're epxerienceing is not 'turbo lag' - it is a fault. Turbo lag is the time it takes to spin up the turbo before the boost pressure rises, and you get some power. This was quite marked on the old XUD 1.7s as they had huge turbos which took an age to spin up! Should be much less marked on HDi, as they use variable geometry which helps the turbo to spin up much faster. Your Dad's Picasso has a glitch in the software or a sensor that is causing it to overfuel / underboost some times. Trouble is, you won't know untill it stops working altogether as the computer won't read a 'fault' as long as it gets some sort of reading! I'd imagine there's a boost pressure sensor on these engines, and I'd plump for that being dicky to start with.
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Post by wheeler »

is there any air leaks when you rev it(can you hear a hissing noise).i assume this is why the pipe was tightened,they have a habbit of popping of all the time,there is now a modified pipe available if it keeps coming off.if not its been known for faulty airflow meters to cause this.
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