Turbo Timer - How do they work?
Discussion
To all you mechanically minded pistonheads!
I have been told that these are fitted to allow the turbos to cool down gradually after hard use. Having seen several video links somewhere on pistonheads to exhaust manifolds glowing redo hot on test beds this is understandable - not sure what your average exhaust temp is (I guess this depends on fuel, engine size, power, state of tune and more) but it must be pretty hot. This in turn is heating up the turbos? (Is this why ceramic ones are used?)
So after a run where both the turbo and engine have been worked hard and oil & water temperatures are high what is the advantage in having a stationary car sat there running trying to cool things down with no airflow? Would it not be better to reverse the 'warming up' process and to drive the last few miles/laps at a more sedate pace to allow everything to cool down? Or are the timers designed to be used in conjunction with a cool down period? From my limited understanding with the engine at idle turbos are not working - it is not until you reach a set level of rpm that the turbos start to work. (Is why boost gauges have 'two' gauges, one for boost the other for negative induction?)
Would someone please explain how it all works?
One last question - what is the difference between a wastegate and a dump valve?
I have been told that these are fitted to allow the turbos to cool down gradually after hard use. Having seen several video links somewhere on pistonheads to exhaust manifolds glowing redo hot on test beds this is understandable - not sure what your average exhaust temp is (I guess this depends on fuel, engine size, power, state of tune and more) but it must be pretty hot. This in turn is heating up the turbos? (Is this why ceramic ones are used?)
So after a run where both the turbo and engine have been worked hard and oil & water temperatures are high what is the advantage in having a stationary car sat there running trying to cool things down with no airflow? Would it not be better to reverse the 'warming up' process and to drive the last few miles/laps at a more sedate pace to allow everything to cool down? Or are the timers designed to be used in conjunction with a cool down period? From my limited understanding with the engine at idle turbos are not working - it is not until you reach a set level of rpm that the turbos start to work. (Is why boost gauges have 'two' gauges, one for boost the other for negative induction?)
Would someone please explain how it all works?
One last question - what is the difference between a wastegate and a dump valve?
Turbo timers are a waste of money IMO, but the ricers love them.
All they do is keep the ignition powered up after you take the key out and let the engine run for a minute or 2 after you turn it off.
It is actually illegal to have a car sitting empty with the engine running as far as I am aware.
As for the other queries, http://auto.howstuffworks.com/ will have the answers for some.
Do a little searching, and you will learn a lot more.
All they do is keep the ignition powered up after you take the key out and let the engine run for a minute or 2 after you turn it off.
It is actually illegal to have a car sitting empty with the engine running as far as I am aware.
As for the other queries, http://auto.howstuffworks.com/ will have the answers for some.
Do a little searching, and you will learn a lot more.
The main point of the turbo timer is to keep oil moving through the turbo and stop it being stationary next to a very hot bit of kit which works as well at idel as when moving. Subaru's have a little notice hidden in a coin holder stating that you should let the engine idle for a minute after 'hard or highway use' before turning off the ignition. You are right that the best thing is to cool things down on a slowing down lap but sometimes they frown on this in Tesco's car park.
GreenV8S said:
I would have thought that an electric pump just to trickle the oil around would be just as good - maybe backed up with a similar pump for the water if you're feeling keen. Are turbo timers the cheap and cheerful way round the problem, then?
Pretty much. They are just a time switch attached to the ignition so no extra moving parts, plumbing etc to worry about / break / install.on trucks they are just a timer relay plumbed into kil side of the ignition, but some systyms are automactic when you turn off, some you have to activate, but for safety reasons the auto ones have an emegency kill switch! turbo timers are very common on coaches! i would guess its much the same idea with cars
Most turbos are water cooled now, which the OEM's introduced to improve the longevity of the bearings.
Yes if you are running at full boost down the bypass and simply stop and turn the engine off, you wont be doing the bearings any favours - but anyone with a modicum a mechanical sympathy will just slow down and drive slowly / off boost before shutting down which is all that is required in my opinion.
Rather than pump the oil round after shutdown, a technically easier approach is to continue pumping the water around, which many OEM's also do - called after-run pumps - my mates audi S4 (amongst many) employs one as standard. And is something I may fit to mine as some point in the future.
Wastegate: Diverts hot exhaust gas from passing through the turbine (the hot side) to control compressor speed and therefore boost pressure.
Dump valve: Dumps boost pressure that builds up in the inlet tract between the turbo compressor and the throttle plate. This happens for example when at full throttle (and therefore full/high boost) and you suddenly close the throttle to change gear, the turbo is still forcing air down the inlet, but it's blocked by the closed throttle - therefore it tries to reverse back down towards the turbo, which can slow or even break the compressor wheel.(Extreeme cases - read very high boost pressures)
My dump valve cost 1p from ebay and works well. (thanks to the chavs who must have the latest billet whooshy dump valve and dont want their OEM dump valve)
Yes if you are running at full boost down the bypass and simply stop and turn the engine off, you wont be doing the bearings any favours - but anyone with a modicum a mechanical sympathy will just slow down and drive slowly / off boost before shutting down which is all that is required in my opinion.
Rather than pump the oil round after shutdown, a technically easier approach is to continue pumping the water around, which many OEM's also do - called after-run pumps - my mates audi S4 (amongst many) employs one as standard. And is something I may fit to mine as some point in the future.
Wastegate: Diverts hot exhaust gas from passing through the turbine (the hot side) to control compressor speed and therefore boost pressure.
Dump valve: Dumps boost pressure that builds up in the inlet tract between the turbo compressor and the throttle plate. This happens for example when at full throttle (and therefore full/high boost) and you suddenly close the throttle to change gear, the turbo is still forcing air down the inlet, but it's blocked by the closed throttle - therefore it tries to reverse back down towards the turbo, which can slow or even break the compressor wheel.(Extreeme cases - read very high boost pressures)
My dump valve cost 1p from ebay and works well. (thanks to the chavs who must have the latest billet whooshy dump valve and dont want their OEM dump valve)
Edited by eliot on Sunday 2nd July 09:51
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