should i let TDI cool down

[Muttley]

No, on the LCR that's a continued coolant pump, circulates coolant round the block and turbo.

 

[leon cupra r]

Always leave a car to cool down if its running a turbo, as said, the RPM they run at means they get very hot (and also pressurising air creates heat - feel your DV after a spirited run and it will be quite warm even though all that is going through it is fresh air from the intake that's been through the turbo), and the oil will cook if you turn engine straight off. I always try to leave it 30 seconds before driving, just so the oil gets time to be pumped round all parts of the engine so its lubricated before putting under strain, and always always leave it to cool down, if I've been taking it steady before I stop, I'll leave it 30 seconds, but if I've been giving it some then its at least 1-2 minutes to make sure its had chance to cool down.

 

[Chester]

Yes, the OP asked about letting a TDi cool down. Most people are talking about 20VTs on the thread so I've noticed, and to be frank, never mind feeling if the dump valve is a bit warm, open the bonnet and you'll see the exhaust manifold glowing red if you've been driving it properly!

TDi's just don't get hot. In fact, if I've driven home from work during Winter (9 miles) leave the car idling on the drive whilst I disarm the house alarm and open the garage door, the water temp can drop dramatically. Allowing heat soak is equally not a good idea, so don't let the engine idle for too long either.

I'll see if I can make an audio clip and capture the 'howl' I mentioned. It's quite odd.

 

[leon cupra r]

allowing heat soak to where? and yeah good point obviously the derv heads wont have the DV, but that point aside, the turbo is still going to get red hot.

regardless of what fuel gets mixed into the air before it enters the engine, the turbos are still spinning extremely fast and still pressurising air, so are still going to get very warm indeed. maybe not quite to the extent of a petrol's turbo but I'd still not be happy switching the engine straight off.

And diesels take that long to warm up, it doesnt surprise me it's cold when you've only done 9 miles!

 

[Chester]

Actually, TDi turbos arguably work harder as they tend to be depended upon for more pressure than a petrol engine (standard configurations). But the duty or load on a TDi turbo can be much much higher. Vans for instance can be pretty much sat on a motorway fully ladened on full throttle all day without complaints. Try that in your LCR, you might be having lunch in an AA recovery truck! One of my clients says that he used to design petrol turbo engine's full throttle duty to be about maximum 30% of run time, or duration the engine is started.

Yes, TDi turbos get hot, but you don't get the exhaust temps or increase in inlet air temperature on a TDi that you do with a 20VT, especially in the height of summer. And that's my point, there's no need to get them cool because they never get outrageously hot in the first place. I must admit I don't have figures to substantiate it, but I can get that information if anyone needs it.

So, I stand by what I said about turning off a TDi after 10-20 seconds of idling. Another client I have has vans that get switched off as soon as they get back to the yard with 300K miles on the clock, never hurts them. But I'd never recommend that on a turbo petrol engine.

BTW, you sure the PD150 hasn't got a recirculation DV? I'm sure I can hear something, but I've never looked.

 

[Jonezyfr]

they do have a recirc dv definatly, my standard one is quite loud for a oem recirc

 

[dholdi]

I'm pretty sure none of the PD's have dumpvalves.
Whats the point ? a dumpvalve is supposed to relieve the pressure between the turbo and throttle body when the throttle is closed.
As a tdi doesnt have a throttle body then ................
I agree they do make a sound similar to a dumpvalve though.

 

[Chester]

This is the sound faded in after approximately 1:50 (m:s) of idle time.

Idle howl

Any ideas what's going on here? (Apologies for going off topic slightly, but I think that's all done)

 

[Chester]

hehe, I thought this would keep you guessing! Nope, AC is off, and the rad fans are stationary. Listen very closely and you'll hear a hiss like gases are being redirected before the howl starts.

 

[Shani]

There's no need to go through a 'cool down' process on a TDi. They don't have anything like the amount of thermal problems that a petrol turbo engine has. So no, a 10-20 second spool down is all that's needed as the turbo still spins at 125K RPM, and faster under load.

There's practically no way to drive a TDi off boost either, without coasting, but then even gentle acceleration into a side road or cul-de-sac will make a TDi's turbo spin-up.

All that said, I always give it 10 seconds minimum to let the turbo spin down.

Incidentally, if the car is left idling for over a minute or two, the turbo starts howling again. It's definitely ECU controlled and a quick tiny blip of the throttle stops it. Is the intention to lean out the exhaust gases or something?

What he said. TDi's really don't produce that much heat compared to turbo'd petrol enngines. You ever seen an LCR exhaust manifold after a spirited drive. It literally is glowing red hot. If it's not your not driving it right!

And the VNT mechanisms in the TDi's keep the turbo spinning pretty much all of the time.