Questions on how we spend our money and our time - consumer goods and services, home and vehicle, leisure and recreational activities
Posts: 1598
Joined: Sun Mar 10, 2013 3:31 pm

Re: Turbochargers

Post by sambb » Sat Jun 17, 2017 6:16 pm

The porsche 911 turbo, of any vintage, is really great. Love that one. I also like the biturbo mercedes in the S550.

Posts: 150
Joined: Sat Nov 12, 2011 6:02 am

Re: Turbochargers

Post by Pinotage » Sat Jun 17, 2017 8:00 pm

Turbo Volvo here

3.0L Inline T6 w/Polestar tuning

325 hp

354 lb-ft of torque

5.0-ish to 60 mph


32 mpg on the highway


Posts: 426
Joined: Sat Oct 22, 2011 1:57 pm
Location: New York City area

Re: Turbochargers

Post by NHRATA01 » Mon Jun 19, 2017 9:49 am

jharkin wrote:
Wakefield1 wrote:I am skeptical of the idea that turbocharged gasoline engines can now be built with the same high compression ratios as can be used on non-turbocharged/non-supercharged gasoline engines (assuming operation at sea level atmospheric pressure conditions),if the engine in order to preserve reliability with the turbo on it has to be built with a lowered compression ratio,then it would seem to me to negate some of the desired fuel efficiency gain.

But they are dong it. Typical compression ratios for NA gas engines that ran regular unleaded before all the modern electronic tricks to compensate for detonation would be limited to what, around 7-8:1 CR? you could go up to 10, 11 or 12:1 on high test. Now we have cars approaching 11:1 made to run regular gas with creative programming using the knock sensor and ignition maps to compensate.

In the old days the turbo car would start with an even lower CR (say 5-6:1) so that under boost it acted like a 11:1 car and could run premium gas and not detonate. Well now that add turbos to a car that was already 10:1 and run even higher CRs. the challenge is just in managing detonation and knock as handling the high pressures is easy (like we have been saying diesels have managed 18:1, 20:1, 25:1 and higher for almost a century - we have the materials to do it).

Port fuel injection, with individual cylinder metering and coil per plug ignition with a modern ECM allowed N/A engines to run closer to 10:1 on 87. The modern electronics weren't necessarily compensating for detonation, rather they were able to ensure proper fuel dosage to each cylinder with a more finely varied spark advance thanks to the coil per plug, and feedback from the O2 sensor to eliminate detonation beforehand. Versus say, a 2 or 4 bbl downdraft cab at a central point then going into an 8 port intake manifold and a mechanical distributor with only a vacuum spark advance, and no feedback. More crude controls meant you needed to run with a greater factor of safety to avoid detonation. The knock sensor addition was just the icing on the cake of detonation prevention and telling the ECM to back off spark advance once it "hears" some knock.

But you're also missing the adoption of direct injection. Now since you are evaporating the fuel in the cylinder instead of the intake manifold, you are cooling the intake charge and can run even higher CR without detonation. So it is not uncommon to see an N/A engine running 11.5:1 on 87 (such as GM's 3.6 DI V6) or closer to 12:1 on high output/high octane rated engines, whereas back in the day that used to require 104+ race gas.

The other help is having constantly variable valve timing. Someone mentioned the term "static compression", which is basically the numbers we've discussed here. What is more important and requires calculating based upon valve events, is dynamic compression, because that will really determine how high the cylinder pressures get. If you run a camshaft profile with a lot of overlap on a high static compression engine, some of that cylinder pressure is going to be bled off through the open exhaust valve so your dynamic compression may not be as comparably high.

Posts: 426
Joined: Sat Oct 22, 2011 1:57 pm
Location: New York City area

Re: Turbochargers

Post by NHRATA01 » Mon Jun 19, 2017 9:57 am

MnD wrote:We keep our vehicles for 12-18 years so this trend is a concern.
For the kids we bought or passed down older subarus and with careful maintenance you can get 200K or more miles out of them.
Denver is full of 200X model year subaru's with typically over 200K miles HOWEVER you will find almost zero of the older subaru turbo models on the road. The turbo fails and it basically totals the older vehicle - not economic at that point to repair.

There are plenty of turbocharged cars that have lasted 12-18 years and over 200K miles. I see plenty of the 1st gen WRX's still out there and they were popular cars to beat on (I bet a lot of them are on their 2nd or 3rd 5 speed manual trans though ;) )

Frankly as a shadetree guy, more than a turbo I'd be concerned about the long term (200K+ mile) durability of direct injection engines. Without the fuel from a port injector constantly cleaning the intake valve, you are seeing these engines build up significant sludge and coking on the intake valves resulting in poor drive-ability and fuel economy. Often with less than 100K miles. Some such as earlier Audis/BMWs, not even 50K miles. And the only resolution is to pull off the intake manifold and bead blast the valves, chemical cleaning often isn't sufficient. Some makes claim to have reduced the problem compared to early adoption 10 years ago, but others (such as Toyota) have found the only way to eliminate it is to add complexity and go with both port and direct injection to the engine to keep the intake valves clean and still reap the efficiency benefits of DI.

Posts: 297
Joined: Thu May 19, 2016 5:04 pm

Re: Turbochargers

Post by WhiteMaxima » Mon Jun 19, 2017 12:59 pm

As CAFE standard requires, we will see more turbo charged vehicle on the road. New turbo engine is much more durable than old generations. The engine is lighter and produce more horse power and torque per cubic volume. Combined with direct injection, turbo engine also sounds more like diesel engine. Engine lagging is still noticeable. Gas mileage is much better. So there are trade offs.

Posts: 54
Joined: Sun Jul 06, 2008 4:03 pm

Re: Turbochargers

Post by ncbill » Mon Jun 19, 2017 2:37 pm

Sure, in theory with design improvements (better cooling, synthetic oil) the newer turbos should last longer.

In practice, well as another poster mentions the turbos on the EcoBoost engines...haven't.

Given inexpensive gasoline I'll stick with larger, naturally-aspirated engines for the foreseeable future.

User avatar
Posts: 463
Joined: Wed Dec 08, 2010 6:44 pm
Location: Greater Atlanta area

Re: Turbochargers

Post by fandango » Thu Jun 22, 2017 6:03 pm

What about the cost of maintaining the turbo? Surely that is a continuing expense if you own a vehicle with a turbo charger?

Knowing dealerships and garages, I am sure they want to check them out once per year at around $100 a pop to examine functioning, potential deposits, etc.

Posts: 80
Joined: Wed Nov 11, 2015 5:24 pm

Re: Turbochargers

Post by keaton » Thu Jun 22, 2017 7:46 pm

fandango wrote:What about the cost of maintaining the turbo? Surely that is a continuing expense if you own a vehicle with a turbo charger?

Knowing dealerships and garages, I am sure they want to check them out once per year at around $100 a pop to examine functioning, potential deposits, etc.

Nope! There is nothing extra in "maintenance" as it's a very simple design that does not add anything extra in terms of "checks". Sure you could check for shaft play but any dealer you took the car to wouldn't have a clue. Turbo systems are very simple, not a whole lot to worry about on most systems.

Posts: 178
Joined: Sat Aug 23, 2008 9:40 pm

Re: Turbochargers

Post by rallycobra » Thu Jun 22, 2017 8:19 pm

They are a product of legislation. Some countries charge taxes for larger motors. Turbos let you get more power out of a smaller motor. When driven by manufacturers on mileage test loops, they tend to get better mileage than normally aspirated cars. Real world mileage is usually worse. Turbos need to burn more fuel for a given amount of air consumed to keep from exploding than a normally aspirated car. They are fine for a daily driver, but I wouldn't purchase one for a track car.
26% Total Stock Market/20% Total International/13% Small Cap Value/6% Reit/35% Intermediate Bond Fund | 65/35 Stock Bond 2:1 Domestic/International + Reit

User avatar
Posts: 185
Joined: Wed Mar 20, 2013 11:29 pm

Re: Turbochargers

Post by victorb » Thu Jun 22, 2017 8:25 pm

You should drive the vehicle with a non-turbo engine and with the turbo engine. We looked at both the 2.4 4-cylinder non-turbo and 2.0 Turbo 4-cylinder on the Hyundai Santa Fe Sport. The 2.4 was fine, but the Turbo added so much more. The thing that impressed me is the torque curve of the turbo engine. The turbo version has 260 ft.-lbs from 1450-3500 rpm. It also uses a twin-scroll turbo to make it more efficient. I noticed you don't have to be in the upper rpm range to have good driveability. We chose the 2.0T.


Posts: 475
Joined: Wed Apr 17, 2013 12:05 pm

Re: Turbochargers

Post by MindBogler » Thu Jun 22, 2017 8:35 pm

As long as the turbo is water cooled there is little chance of the heat soak problems of the past. In the 80s many turbocharged vehicles were oil cooled only and they had significant problems with oil coking in the bearings leading to premature failure. Yes, adding turbos to a car increases the complexity but it doesn't logically follow that the car will be less reliable. Even a NA engine built today is far more complex than a NA built 30 years ago (variable valve timing, dual cams, twice the valves, coil on plug, numerous electrical sensors). Are these motors more or less reliable on average? Complexity has increased but so have tolerances. Reliability on average is much higher today than a car purchased 30 years ago. Turbochargers increase feel economy under cruising conditions. They also have the unique ability to produce the same power at sea level as they do at high altitude. I've been driving turbo vehicles for 30 years. Long haul trucks all use turbos. If there were reliability concerns under the hardest use, that wouldn't be the case. There is nothing to fear in my opinion.

Post Reply