Valkie wrote on Aug 3^rd, 2021 at 3:09pm:



Yep, cool the gas after compression. So cooling the gas will help the decent radiators

John Dillermand wrote on Aug 3^rd, 2021 at 10:56am:


so that is another complexity to 'go wrong'.

When the turbocharger compresses the air from the intake, it heats the air as part of the compression process.

This compressed air is then put through the intercooler, a radiator, which cools the compressed air and in the process making it denser.
This is then directed into the engine with the fuel mix, by one of several processes.

The turbocharger is NOT COOLED by the intercooler.....ever.

In the later turbochargers, oil is circulated around the bearings of the turbocharger to cool the most important parts.
Some underground turbochargers are completely encased in a water jacket to ensure that it does not exceed the maximum allowable temperature for any underground equipment.
But to my knowledge, this is not done in any other application.

Turbo get very hot, especially under heavy load.
The turbo needs to be allowed to cool ( by way of the oil) or it will seize up.
This is accomplished with a turbo timer, which allows the engine to run at idle for a set time, or with a turbo saviour, a sort of oil tank which keeps the bearing immersed in oil even when stopped and which feeds the oil to the bearings as soon as the engine is started.
These are not standard on commercial turbo engines.
You can buy turbo timers and fit them, but remember, the engine will run for between 3 and 5 minutes after you turn it off.

In reality, a modern turbo is quite good.
All you need to remember is that after you push it hard, you need to idle it for a few minutes before you turn it off.
Alternately, slow down and take it easy for the last couple of kilometres before you plan to turn it off.

The biggest killer of modern turbo is the people who start the engine and start thrashing the engine from cold.
The oil needs to reach operating temp and fully circulate through the turbo before it starts to work properly.

There are a few other interesting issues with turbo and their self adjusting vanes, but we shall leave that for now.

Sprintcyclist wrote on Aug 3^rd, 2021 at 5:49pm:


Air to air intercoolers are simple nothing moves not much to go wrong. If you get a hole or hose leak you will lose boost.

Water to air intercoolers have a water pump so if water leaks out or pump fails it doesn't work if air leak happens you lose boost.

Compressing air actually heats it  you might notice pump for push bike gets warm when pumping tyres up my mountain bike has Michelin tyres 60 psi pump gets warm very quick.

With a turbo running about 1 bar boost (14.7 psi) if air going into turbo is around 20 deg C then compressed air coming out of turbo will be around 90-95 deg C before it goes into engine. The intercooler is placed between turbo and engine intake to reduce air temp which increases air density giving more power and makes motor live longer as high inlet air temps can cause detonation.

The intercooler is usually placed in front of radiator which increases air temp going under the bonnet. Water to air intercoolers are usually more efficient so that means another radiator in front of engine cooling radiator. Add air conditioning in then the air getting to water radiator is heated by intercooler then AC before it even gets to water radiator to keep engine cool so a lot more heat going under bonnet.

Turbo rebuilds at required service intervals get expensive you have to change engine oil frequently add in the fact petrol ones need premium 98 fuel it all ads up to more cost. On boost they run richer air fuel ratio compared to non turbos which means they guzzle fuel when driven hard.

I was servicing a twin turbo Maserati for Bob Hawkes lawyer over 20 years ago being a V engine it had separate intercoolers for each bank.

Subaru sell a can of upper engine cleaner for about $20 from spare parts they use it every service with WRX to remove carbon deposits that build up with turbos as they run richer on boost than non turbos. Take the spark plugs out squirt some in each cylinder then put the rest through inlet manifold let it soak in then start engine blow a shitload of smoke for about a minute then all alloy from inlet manifold to top of pistons is bright shiny clean alloy.

Mercedes have done something good with turbos in Formula 1 they split in in half with exhaust driven part at rear of engine and intake part at front. This stops a lot of heat soak from turbo raising air temp allowing them to run slightly leaner which makes a difference with limited fuel load. It also allows an electric motor on shaft to spin up turbo when throttle is closed under braking (no exhaust gas to spin turbo) so no lag and good boost when driver puts foot down. Honda copied Mercedes last year with turbo layout they're the 2 best engine currently in F1.

I would avoid turbos a bigger engine that doesn't need to be revved as hard will last longer. A small engine with a turbo will guzzle just as much fuel to make the same power. If you live at high altitude then a turbo might be ok at 7500 foot a non turbo engine will only have 75% of it's power.

Sprintcyclist wrote on Aug 3^rd, 2021 at 11:42pm:


That temp increase is for 1 bar boost it goes up even more with higher boost levels.

The turbo glows red hot on boost extreme temps fry and break the oil down into something more like varnish so as Valkie said a turbo timer or running it real slow for a few minutes before shutting down to reduce temps helps. At idle it shouldn't have much exhaust gas flow spooling up the turbo keep in mind exhaust gas will still be over 500 deg C, Shutting it down while turbo is glowing red is not a good thing to do. Some engine reconditioners i know think letting an engine idle is also not good as oil pressure will be at it's lowest which helps wear engine out. Oil pressure rises with increasing revs.

Turbos love cold weather not so good on hot days so probably not suited for the hotter parts of our country.

The AC is just like a fridge you will have a cold radiator inside fridge and the coil type radiator at rear of fridge will be warm. Reverse cycle air conditioning in homes just reverses gas flow inside so cold part becomes hot and the hot part gets cold. With cars you have a small radiator in front of engine radiator for AC so while AC makes car cool inside cabin it also adds heat under bonnet. Run the AC for a few minutes every week in winter it keeps rubber seals lubricated so gas doesn't leak out which then requires regassing for AC to work. Car AC differs from home AC as engine vibrates and moves so they need flexible joins so use it for short time even in winter to prevent problems.

If it's a good car it might already have a cooler for auto trans manuals don't need them  they always run cooler. If you're doing stop start in peak hour traffic while towing a trailer then maybe auto will be better than manual.

Water cooling for a turbo might be ok it would add more complexity what happens if it gets a water leak does it stuff the turbo? It also adds cost which most try to reduce.

You have to chew a certain amount of fuel to make whatever power you require so a smaller engine with a turbo will chew just as much if not more fuel as a bigger non turbo engine making the same power.The bigger non turbo engine doesn't work as hard so it will last longer being cheaper in the long run.