Teach me about turbos
 

Okay I know they have been around a looooong time so they must be reliable, right?
I just have a problem wrapping my head around a small fan running at high RPM... attached to an exhaust pipe!

I asked because it seems a lot of cars are going the way of the turbo... I believe Smoky Yunick predicted this.

increased power while utilizing wasted energy.

"reliable" is a relative term. I still tend towards normally aspirated as far as longer service is concerned.

It's a trend because of MPG requirements imposed by politicians. Much better mileage, as long as you stay off the boost.

On the boost? Not so much better mileage, with added strain on the intake & bottom end.

Mechanical idiot here....

Don't turbos work by playing with the air pressure on intake and/or exhaust?

Shouldn't from a fizzix or kemestry standpoint an increase in intake pressure will provide more oxygen to use in combustion, whereas a decrease in exhaust pressure will reduce amount of work needed to move the piston to the top of the cylinder?

I know things like NOS work by altering the kemestry of the "ambient" gas at intake providing more things that go boom and increase NRG ...



yes, my high school physics teacher spelled things like this. best teacher I had in high school.

Turbo: Exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.

little turbos spin up fast and give good mid-range power but run out of breath at hi RPM
my old volvo was like that THAT TYPE CAN GET GOOD GAS MILEAGE

the old 911 turbo used one big honking turbo get top end power
low RPM has no power and power come on quick as boost builds and eats gas on boost
new twin turbo 911's try to balance but are more high end biased then a volvo

they are not hard to rebuild IF done before there is massive shaft ware/wooble
just two bearings to replace unless the shafts go and blades bend then new stuff is needed

turbo's need fake oil [ synthetic ]dead dino oil burns up and cokes the bearings

And in most turbo's engines significant power increase is cheaply gained but at the expense of fuel consumption. Eg forcing in twice as much oxygen means twice as much fuel must be put in to maintain the stochiometric ratio .
My Mitsubishi 1.5 litre motor for example went from 177to 210 BHP and 180 to 225 lbs/ ft of torque with just a different set of headers and a different turbo bend and a remap.

Ironic because on my list is a Mustage ecoboost :D

But everything from Hyundai to VW seems to be going to turbos.

I know how they work, just wondering how long they work.

For all the turbo charged cars on the road, I don't really replace all that many . Every once in a while I get a roached out saab that has not had an oil change in 20,000 miles come in with a cooked turbo. Ive done a few audi's and a couple on diesel trucks, but for the most part, the turbines seem to hold up pretty well .

My volvo turbo had over 200k and very little slop. I rebuilt it because I was in there because a valve burnt, but really could have just left the turbo alone. In retrospect, it was doing fine.

I put a used 944 turbo turbo into my 944 turbo when I got it, and got at least 90k out of it. The 944 turbo's had a neat little feature, which was a water cooled jacket around the oil/bearings, and a secondary electric water pump which keeps water flowing around the turbo for a time after the car is turned off until things cool down.

The nice thing about the 944 turbo was you could turn it off even if the engine was hot. On my volvo, I would always make sure I hadn't really driven it hard for a minute or two before cutting it off. I'm sure in the history of the car I never "lost my temper" and turned it off hot. Never/ not once!

Synthetic oil used in both.

They are also more efficient as in for the environment.

They're basically a compressor of air using a wasted energy source (exhaust gas), and turning it into more efficient burn.

Want to blow your mind? Look up compound turbos. Different idea then just slapping on one turbo per bank of cylinders....

Porsche too? Read an article awhile back that has forced porsche to use turbos in EU to meet the emissions requirements.

I'm still leery of the small engines in new cars with turbos & putting out high amounts of power. In my old mind, all that power adds stress to an engine reducing its longevity.

more air in but the more air now has too go thru the blades and do work
on the way out so more back-pressure not less
but more power due to more air IN [remember more gas burned also]
as just more air is lean and lean turbo cars go BOOM so bias is rich

The oil is guaranteed to cook in the bearings or small misaligned passages and trash everything.

Slow heat up and very slow heat down is the key. Get a cool-down ignition timer when city thrashing.

Needs it's own proprietary directed airflow.

You are reading my mind! However the allure of 30MPG and 300HP is hard to resist.

All I know was I stepped on the pedal and was pushed back in the seat in my 930.

400 RWHP

And 3 MPG at the track 🤪

Every car I own is turbo charged. Duramax Suburban and Saab daily drivers.

https://www.youtube.com/watch?v=lrCwmpjR77U
https://www.youtube.com/watch?v=DqWKNuTppmU

https://www.youtube.com/watch?v=zenMEj0cAC4
https://www.youtube.com/watch?v=Xe7ITt9ZuOQ

I do not think that the turbo is the weak point anymore, the rest of the engine is taking more pressure these days with direct injection they have raised the static compression ratio way up in the 12 to 1 range and then add a turbo to force some more in, I'm thinking the rings and rod bearings are the wear items, the turbo is a fairly inexpensive part anyways. The Honda,s and BMW's have gone to small 4's with direct injection and turbo, from what I have read, so far they have been pretty good, BMW with a timing guide failure but that seems to be it.

Will they hit 200k before needing a rebuild? Long off warranty so most manufactures don't care.

I think that the way in which a motor is stressed is important. A (relatively) slow turning, warmed-up turbo'd diesel (commonly running a forged steel crank and rods) feels and sounds really smooth compared to a faster-turing NA motor of similar displacement and comparable power (but often running much less robust rotating/reciprocating hardware).

There is much hype about an invention that solves the too small turbo problem.
Take a look at e-booster from BorgWarner. The electric turbo comes on for a few seconds and then the big turbo takes over. Mercedes S Class has this already.

Regarding more stress on the engine parts - let's assume the engine designers know this (duh) and change the design to meet the longevity requirements.

Only one moving part.
light weight rotor, precision balanced so very smooth at high rotational speeds.
Typically sleeve bearings lubricated by engine oil, circulated to carry away heat and prevent carbon buildup.
Relatively low pressures.
Some are also liquid cooled.
Some even has ceramic bearings but I'm not a fan.

Heat of exhaust is a concern but stainless alloys handle the heat on the gas turbine side, special elastomer o-rings to stand up to the heat, some have mechanical seals to keep the oil where it belongs and the oil carries away heat as does the air flow on the compressor side.
And as soon as you take your foot off the throttle the EGT drops quickly starting the cool-down process.

The oil is key. Gotta keep it clean, and I consider synthetic almost mandatory.

I've pulled turbos off junk-yard cars with over 100k miles, and repurposed the turbos onto other custom applications with no refurbishment at all and they worked just fine.
Taken care of they should last the life of the engine.
But if abused they turn into bic lighters.

I had a friend who bought an almost new 924 turbo a long time ago, against my advice.
He had a habit of driving fast down the street, putting it in neutral, and pulling the e-brake as he came to a stop and instantly hopped out of the car, looking cool.

I said don't do dat. He scoffed.
After replacing the turbo TWICE in two years he started to listen.

See as he was pulling up, the turbo was still spooled up and spinning really fast. He shut off the motor before it had a chance to slow down or cool off, which shut off the oil flow to the hot turbo and bearing, melting the sleeve bearings. And what oil was left in the turbo bearings cooked as it sat there cooling down, which caused damage when re-started.
Synthetic oil was not commonly used back then.

But he looked cool.


PS you never want the engine to reach stoich under boost, too lean. Hot. melted. ping ping.

Depending on engine and boost levels, 12 to 13.5 to 1 would be a lot safer.

I’m hooked on the turbskis. More power out of a smaller package and usually much more easily modified than an NA motor. That a stock 997 twin turbo Mezger motor, with nothing other than an ECU flash, can make over 200HP/liter while maintaining easy driveability still blows my mind. Not enough power? Beef up the pistons and rods and put some bigger snails on there and the Mezger TTs can easily double that figure again. Impressive (though likely not nearly as driveable or robust).

And with modern electronics, they only seem to get better. Lag is constantly being reduced from one generation to the next, so the new engines feel pretty much like much bigger motors of yore.

Also, many new turbos are also watercooled, so the bearing coking issues are not what they were 30 years ago. That said, I’d still run a quality oil and stay on top of changes...

I’m not sold on the new reverse-flow, valley-mounted turbos (like on BMWs and Mercedes). I get why they do it, but I question what lifespan those are engineered for — that’s a lot of heat in a small area on top of the engine.

But the Porsche stuff seems pretty bulletproof. Especially the 911s. But even on the original Cayenne TTs, many of which are approaching 15 years old and well over 150k miles, there are not many reports of turbo specific issues.

Go with the 5.0. You'll get longer life and still decent MPG with adequate power over a flat torque curve.

If you just stick a turbo on a small engine, you will do exactly this. But today, the engines are beefed up to handle the higher pressure charge. Just do not play with the waste gate settings.

My 6.2l Ford can be "lightly" turbocharged to 600hp, with only 7-8psi of boost. 15 will basically double the output. I have no need....

BTW, you can't turbo a 914.

shouldn't maybe
but a fair number of people have
others sell kits

https://www.google.com/search?q=vw+type+4+turbo+kit&ie=utf-8&oe=utf-8&client=firefox-b-1

there are pictures too

I like the somewhat elegant idea of the economically won force derived from turbo charging. I think, from a reliability standpoint, on modern turbos is that they do run hot and expose all your engine bay bits, sensors, pumps etc to more heat which could shorten lifespan.

Just the latest example of legislation driving engineering. Turbos make it easier to hit mandated fleet emissions and mileage requirements.

The government outlined tests for these parameters are set up to favor small displacement turbo motors running off boost. On boost they are dirtier and thirstier than normally aspirated, larger displacement engines, but that is not how they are currently certified. Part throttle acceleration and part throttle cruising are the current test parameters. They are essentially "fooling" the test with a small displacement engine running off boost.

Modern turbo motors, in run of the mill sedans and such, are actually reliable, long lived, trouble free powerplants that meet most drivers' needs. A lot of us hear "turbo" and immediately think of fire-breathing, hairy chested he-man monsters. Such is not the case anymore. While we can still buy those and have fun with them, turbos are now mainstream minivan, SUV, mommymobile technology. It works, it's reliable, and most importantly, it passes the tests. Legislation driven engineering at its finest.

Very common in the type 1/2, and type 4 for a turbo power adder.
Very common.

As much as I like the high rpm scream of a naturally aspirated engine, it's hard to beat the current generation of the turbo gasoline engines. My son's VW Jetta gets great mileage and pulls pretty well from almost any RPM with its 1.8 turbo. My 930 on the other hand feels like it has no power until about 3,000 rpm and then Katy bar the door!

Sammy is being facetious.

Turbos are the way! Keep the oil fresh (don't scrimp on oil changes), cool them down and they will last forever. The power is addictive.

Somewhat ironic that the 930 couldn't be brought in to the US in the mid80s due to Cali emissions laws... hence the M491 optioned cars.

I've never owned a car with a turbo but have put more than 3 million miles on turbo charged diesel trucks (Cummins and Caterpillar) and have never had to replace a turbo. Never used synthetic oil always Shell Rotella 15/40.
I did replace the turbo on my F-550 (6.0) when i bought it because it had sat for 2 years with a bad transmission and the variable vanes inside it had rusted and pitted.
Always amazed me that something that runs at 800-900 degrees and spins as fast as they do hold up so well.

I installed, operated, designed, etc. Gas turbines. 1 moving part. And the temps were as high as 2450F

This!

Porsche has stopped making V8's (think Cayenne, Panamera 928) but now you can spend the same on a 4-cylinder turbo'd Macan.

Of course the peak output stresses are more focused on blown-4, than a NA-8. Which means longevity will likely take a hit. But life of the vehicle is not a controlled metric in the "green" math.

Not if you design the engine to be turbocharged from the beginning. The 930 engine was designed around being turbo charged. The SC benefited, since the 3.0l engine was basically the same as the turbo engine, without turbos.

I had a Honda with the magical VTEC head on it, 8000+ redline, visited regularly, intoxicating little sedan. It was killed by a minivan...

Got a Miata because I missed the ragtop. They are pretty dinky, unless they are sitting next to a Spitfire, then they look huge. If you are over 6', you maybe won't fit. The turbo one had the strongest of everything thing and the best limited slip they used, so I got that one. I put an intake on it because that was about all you could do to it in California. Woke it up some, and now you hear the bypass valve, which is cool. Will need to replace the cat pretty soon, and there is a street legal high flow one available now, at half the price of the OEM. It won't last as long, but it is significantly lighter, and will put me at right around 200 hp to the rear wheels in a 2350# car with a decent independent suspension and a 50:50 balance. All that, and it has air conditioning that works.