Teach me about turbos

scottmandue · 10-26-2018, 01:59 PM

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.

masraum · 10-26-2018, 02:15 PM

increased power while utilizing wasted energy.

pwd72s · 10-26-2018, 02:15 PM

"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.

id10t · 10-26-2018, 02:21 PM

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.

pksystems · pksystems's Garage

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

nota · 02:48 PM

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

petrolhead611 · 10-26-2018, 02:52 PM

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.

scottmandue · 10-26-2018, 02:55 PM

Quote:

Originally Posted by pwd72s

"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.

Ironic because on my list is a Mustage ecoboost

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

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

fastfredracing · 10-26-2018, 02:59 PM

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 .

LEAKYSEALS951 · 03:07 PM

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.

Arizona_928 · 10-26-2018, 03:28 PM

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....

Arizona_928 · 10-26-2018, 03:29 PM

Quote:

Originally Posted by scottmandue

Ironic because on my list is a Mustage ecoboost

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

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

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

Evans, Marv · 10-26-2018, 03:35 PM

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.

nota · 10-26-2018, 03:37 PM

Quote:

Originally Posted by id10t

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.

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

john70t · 10-26-2018, 03:41 PM

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.

scottmandue · 03:49 PM

Quote:

Originally Posted by Evans, Marv

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.

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

A930Rocket · 10-26-2018, 03:54 PM

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 🤪

crb07 · crb07's Garage

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

sugarwood · sugarwood's Garage

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

908/930 · 908/930's Garage

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.