Turbo vs Naturally Aspirated Engine Debate

[MacGregor]

Calling for your expertise! I have never driven a turbo engine car. IF Sonic is offered with heated seats AND a non-turbo engine, I will buy one. However, my hunch is that GM will market the Turbo on the high-end heated seats Sonics. Typical GM marketing ploy: Appeal to the Ignorant Buyer! Get MORE money out of the buyer, both when he buys the Turbo and when he takes it to the dealer for maintenance!

I can understand a Turbo on a diesel engine; WHY on a gasoline engine?

Cons against Turbo:
Lower fuel mileage (mpg).
Turbo Lag while accelerating. No Low End Grunt entering Freeway. Annoying.
More moving parts = more things to break and expensive to maintain.
Turbochargers can be damaged by dirty or ineffective oiling systems. Manufacturers recommend more frequent oil changes for turbocharged engines.
May burn oil.
Price.

Pros in favor of Turbo:
Added power comes at high RPMs, when engine is putting out enough exhaust to drive the fan quickly enough to supply the extra air (Speeding tickets?).
Better performance at high elevations, such as Colorado Rockies.
You get a little plate on the rear deck that says “Turbo.”
Turbos are “Kewl.”
Owners have “Bragging Rights.”
Girls think turbo drivers are Macho.
Turbos are Desired by Teenboyz.

Turbo Lag
Turbo lag is the time required to change speed. This is noticed as hesitation in response when accelerating from idle, compared to naturally aspirated engine. Throttle lag is noticeable under any driving condition and becomes a significant issue under acceleration. This is because time is needed for the exhaust system working with the turbine to generate enough extra power to accelerate rapidly.

Because the turbocharger heats-up when running, letting the engine idle for three minutes before shutting it off gives the oil time to cool the turbo rotating assembly, and ensures oil is supplied to the turbocharger while the turbine housing and exhaust manifold are still very hot; otherwise lubricating oil can be trapped in the unit and the heat soaks into the bearings, causing rapid bearing wear and failure when the car is restarted. Even small particles of burnt oil will accumulate and lead to choking the oil supply and failure. A turbo timer can keep an engine running for a pre-specified period of time, to automatically assure the cool-down period.

 

[RichieRocket]

MacGregor, you are in luck. There is no conspiracy by GM to link heated seats and the turbo engine. Check out the "Ordering Info"
Model Information - Online Ordering Guide

In the interior section, heated seats (KA1) are standard on the LTZ.

In the Mechanical section, the LTZ comes standard with the 1.8L NA engine(LUW), you can choose from the 5-spd manual(M26) or 6-spd automatic transmission(MH9).

 

[Memphis]

Cons against Turbo:
Lower fuel mileage (mpg).Turbo Lag while accelerating. No Low End Grunt entering Freeway. Annoying.
More moving parts = more things to break and expensive to maintain.Turbochargers can be damaged by dirty or ineffective oiling systems. Manufacturers recommend more frequent oil changes for turbocharged engines.
May burn oil.
Price.

All the things listed in red are completely wrong.

Because the Sonic has a smaller turbo on it it actually gets up and goes right away. It doesnt need to spool for a couple of seconds, hence the torque number 0f 148 hitting at around 1800rpm.

Turbo cars these days actually get great gas mileage. Better than N/A. I dont know where you get your info from

Price? The turbo option for this car is only $700 more. Thats it.

Cost more to repair? Warrantys are there for a reason and means you wont have to pay for a thing. Also, turbos dont break down as fast as your thinking. Friends of mine have turbo cars that have over 150,000 miles on them apiece.

As far as burning oil... N/A cars burn oil too.

So my question to you, why not? Why do you have your head up your ass when it comes to turbos? Do you just want to hate on them?

BTW, thanks for speaking plain English. Much easier to read.

 

[blackphoenix]

yes i agree this post was so much easier to read, although the teenboy thing still has me worried. but your facts about turbos are wrong as memphis has pointed out. by doing a little more research i think you'll find that having a turbo car can be alot of fun and make freeway driving so much easier.

as far as turbo lag, if your turbo is lagging your not driving it right lol.. i rev match in my srt-4 and still only get a little lag. i think in this car your going to get that pull feeling very early on in the rpms then it's gonna fall off quick at high rpms.. my wife has a saab 93 and it's running fine for over 30,000 miles with no problems. just doing general maintinace and keeping up on things and the turbo cars will run just as long as any n/a car.

although with fuel mileage, if i go into full boost with srt-4 i can watch the gauge go down lol.. that won't be the case with the sonic, but i can see where you would think that turbo cars get bad mileage, it's all about the driver and how heavy your foot is.

 

[MacGregor]

Thanx RichieRocket

Aye! That is good news that 2LTZ will be available with Bun Warmers, 6 speed auto tranny and ECOTEC 1.8L!! I was concerned because in Cruze the 1.8L N/A is only available on the low-end (no heated seats) model of Cruze - all other models of Cruze are Turbo-only. Glad to see Sonic is not following in Cruze' tireprints! I was looking at RichieRocket's link and it does not appear to have the Turbo info on it yet (not that I care). I wonder if the first 60 days production from the factory will all be non-Turbo? (Regarding heated seats and N/A engines on higher-end models of Cruze, perhaps they will be offered later in the production run. GM tends to do things that way)(I am a Detroiter).

Hey yins! Whot's wrang wid da auld Scots' gab? USA may be a melting pot, but we ain't melted yet! Ya dig?

 

[Screamer4]

Calling for your expertise! I have never driven a turbo engine car. IF Sonic is offered with heated seats AND a non-turbo engine, I will buy one. However, my hunch is that GM will market the Turbo on the high-end heated seats Sonics. Typical GM marketing ploy: Appeal to the Ignorant Buyer! Get MORE money out of the buyer, both when he buys the Turbo and when he takes it to the dealer for maintenance!

I can understand a Turbo on a diesel engine; WHY on a gasoline engine?

Cons against Turbo:
Lower fuel mileage (mpg).
Turbo Lag while accelerating. No Low End Grunt entering Freeway. Annoying.
More moving parts = more things to break and expensive to maintain.
Turbochargers can be damaged by dirty or ineffective oiling systems. Manufacturers recommend more frequent oil changes for turbocharged engines.
May burn oil.
Price.

Pros in favor of Turbo:
Added power comes at high RPMs, when engine is putting out enough exhaust to drive the fan quickly enough to supply the extra air (Speeding tickets?).
Better performance at high elevations, such as Colorado Rockies.
You get a little plate on the rear deck that says “Turbo.”
Turbos are “Kewl.”
Owners have “Bragging Rights.”
Girls think turbo drivers are Macho.
Turbos are Desired by Teenboyz.

Turbo Lag
Turbo lag is the time required to change speed. This is noticed as hesitation in response when accelerating from idle, compared to naturally aspirated engine. Throttle lag is noticeable under any driving condition and becomes a significant issue under acceleration. This is because time is needed for the exhaust system working with the turbine to generate enough extra power to accelerate rapidly.

Because the turbocharger heats-up when running, letting the engine idle for three minutes before shutting it off gives the oil time to cool the turbo rotating assembly, and ensures oil is supplied to the turbocharger while the turbine housing and exhaust manifold are still very hot; otherwise lubricating oil can be trapped in the unit and the heat soaks into the bearings, causing rapid bearing wear and failure when the car is restarted. Even small particles of burnt oil will accumulate and lead to choking the oil supply and failure. A turbo timer can keep an engine running for a pre-specified period of time, to automatically assure the cool-down period.

I drive a small displacement turbo car every day (2.0L WRX).

Maybe I can shed some light:

Turbo lag: Once you get used to the way your turbo car behaves, lag becomes a non-issue. You just learn to keep the engine on boil a bit more and become more mindful of downshifting to push the engine up into its power band. It's a nuisance for the first couple weeks while you get used to it, then it's actually kind of fun

Maintenance: My turbo car has 150k miles on it. Maintenance has been no different than a non-turbo car, though it does burn a little oil (pretty common on boxers, REALLY common on turbo boxers). My car has been (knock on wood) INCREDIBLY reliable. I have done nothing to it but routine maintenance. Now at 150k one of my wheel bearings is humming and might need replacement- but that's it.

Your concerns about cool-down periods are a thing of the past. Turbo-timers are no longer needed with modern turbos thanks to advancements in construction and the advent of water + oil cooling. You don't need to idle them down for 3 minutes.


I think the added on-boost torque from the turbo engine is well worth the extra money, and if you are planning on doing any modifications the choice is a no-brainer since the turbo engine is just waiting to be uncorked.

If there's one thing I've learned about buying cars it is this: Buy the one that is the most fun to drive that you can afford. Go with your gut after some thorough test drives. The worst feeling is getting bored with a car 1yr into a 4 or 5 year loan and being stuck with it.

 

[RichieRocket]

I was looking at RichieRocket's link and it does not appear to have the Turbo info on it yet (not that I care). I wonder if the first 60 days production from the factory will all be non-Turbo?

MacGregor, you are mistaken about the turbo info not appearing. This is the link directly to Sonic "Mechanical" options. It clearly shows the 1.4T engine (LUV) as optional on the 1LT and 1LZ.
Model Information - Online Ordering Guide

Second, the dealer had no problem ordering the 1.4T for me a couple weeks ago...

Third, edmunds.com has 1.4T listed in their options and pricing info

I realize you don't care, but there is plenty of info on the turbo.

 

[RichieRocket]

I drive a small displacement turbo car every day (2.0L WRX)...
Turbo lag: Once you get used to the way your turbo car behaves, lag becomes a non-issue. You just learn to keep the engine on boil a bit more and become more mindful of downshifting to push the engine up into its power band. It's a nuisance for the first couple weeks while you get used to it, then it's actually kind of fun

Maintenance: My turbo car has 150k miles on it. Maintenance has been no different than a non-turbo car, though it does burn a little oil (pretty common on boxers, REALLY common on turbo boxers). My car has been (knock on wood) INCREDIBLY reliable. I have done nothing to it but routine maintenance. Now at 150k one of my wheel bearings is humming and might need replacement- but that's it.

Your concerns about cool-down periods are a thing of the past. Turbo-timers are no longer needed with modern turbos thanks to advancements in construction and the advent of water + oil cooling. You don't need to idle them down for 3 minutes.


I think the added on-boost torque from the turbo engine is well worth the extra money, and if you are planning on doing any modifications the choice is a no-brainer since the turbo engine is just waiting to be uncorked.

If there's one thing I've learned about buying cars it is this: Buy the one that is the most fun to drive that you can afford. Go with your gut after some thorough test drives. The worst feeling is getting bored with a car 1yr into a 4 or 5 year loan and being stuck with it.

I mentioned in a previous thread that I owned a '89 Probe GT with 2.2L turbo, 12 valve engine. I sold it in 2000 with 188K miles on it, no burning oil and still running strong. If I remember correctly, it had about 150 hp and 190 ft-lbs. It was like the Sonic turbo, sized and tuned for low to mid torque, sacrificing top end all-out power. I believe it had 9 psi boost at low rpm then tapered off to 7 psi at high rpm. I never had any problems waiting for lag...

About cool down idling, I never worried about that, turbos get HOT when you are hard on the gas. I would just plan ahead and take it easy for the last couple miles before my destination. In the days before synthetic oil, I never had an issue!

Turbo lag is much more pronounced in car with big turbos(911 or Supra), tuned for max high-end hp. Big turbos have more rotating inertia to accelerate up to speed. Also, longer and large volume intake and exhaust passages, more flow is required to get the volumes pressurized. Neither of these are significant issues with the 1.4T .

One thing no one mentioned yet...Variable Valve Timing! In the old days, turbo engines had to have low compression ratios, like 8.0 or 8.5 to 1. This allowed boost without pre-ignition and detonation, but it hurt off-boost efficiency, like when highway cruising. Also, the low compression ratio made lag feel worse because the off-boost torque was softer. Now with VVT, they can optimize the opening and closing timing of the intake and exhuast valves at various conditions to optimize the "effective compression ratio". Isn't technology great!?!

Lastly, the thing that convinced me was the highway cruise RPM

1.4T @ 70 mph = 2100 RPM

1.8NA @ 70 mph = 2800 RPM

That shows the effect of the low end torque...

 

[MacGregor]

Turbo on 1LZ, but NOT on 2LZ

Roger on that RichieRocket. I see that you can order the Turbo on the 1LZ, but not on the 2LZ. The 2LZ is the way I will go. Yins Turbo Enthusiasts can have yer Turbo's; not fer me!

 

[Screamer4]

I mentioned in a previous thread that I owned a '89 Probe GT with 2.2L turbo, 12 valve engine. I sold it in 2000 with 188K miles on it, no burning oil and still running strong. If I remember correctly, it had about 150 hp and 190 ft-lbs. It was like the Sonic turbo, sized and tuned for low to mid torque, sacrificing top end all-out power. I believe it had 9 psi boost at low rpm then tapered off to 7 psi at high rpm. I never had any problems waiting for lag...

About cool down idling, I never worried about that, turbos get HOT when you are hard on the gas. I would just plan ahead and take it easy for the last couple miles before my destination. In the days before synthetic oil, I never had an issue!

Turbo lag is much more pronounced in car with big turbos(911 or Supra), tuned for max high-end hp. Big turbos have more rotating inertia to accelerate up to speed. Also, longer and large volume intake and exhaust passages, more flow is required to get the volumes pressurized. Neither of these are significant issues with the 1.4T .

One thing no one mentioned yet...Variable Valve Timing! In the old days, turbo engines had to have low compression ratios, like 8.0 or 8.5 to 1. This allowed boost without pre-ignition and detonation, but it hurt off-boost efficiency, like when highway cruising. Also, the low compression ratio made lag feel worse because the off-boost torque was softer. Now with VVT, they can optimize the opening and closing timing of the intake and exhuast valves at various conditions to optimize the "effective compression ratio". Isn't technology great!?!

Lastly, the thing that convinced me was the highway cruise RPM

1.4T @ 70 mph = 2100 RPM

1.8NA @ 70 mph = 2800 RPM

That shows the effect of the low end torque...

Another huge thing which GM sadly decided against putting into the 1.4T is direct injection. You can run comp ratios much higher with forced induction thanks to the more precise fuel delivery and the cooling effect from spraying directly into the chamber. I bet the 2nd generation of this motor gets it, once GM figures out how to cheaply produce HPFPs and starts using DI across the whole line.

 

[RichieRocket]

Another huge thing which GM sadly decided against putting into the 1.4T is direct injection. You can run comp ratios much higher with forced induction thanks to the more precise fuel delivery and the cooling effect from spraying directly into the chamber. I bet the 2nd generation of this motor gets it, once GM figures out how to cheaply produce HPFPs and starts using DI across the whole line.

Good Point Screamer4, my buddy has a Mazda SPEED3 with the Direct Injection turbo engine. They can boost higher without pre-ignition/detonation problems because of it...

Back in March, I asked the Chevy rep at the NYC auto show why they did not use DI. He explained that a normal FI system operates at ~100 psi and is relatively cheap, a DI system has to operate at ~1000's of psi because the fuel is being sprayed directly into the high pressure cylinder and it has a much narrower time window to get the fuel in. So the DI system is more $$$, like $500 per car, so for a low-priced econo car, it didn't buy it's way in... It would add a couple MPG's.

A draw back to DI is gunk building up on the intake valves. Exhaust and gunk from the EGR and PCV gets sucked into the intake stream and could settle on the intake valve outer surface. Normally, the detergents in the fuel mist would dissolve these deposits, BUT with DI, no fuel goes past the intake valve outer surface. So DI engines need intake valve cleaning at some interval, 30K, 50K, 100K, not sure? So you would spray detergents into the intake air to knock off those deposits...

The Hyundai Accent uses DI and it gets 138 hp, 123 ft-lbs, 40 MPH(hwy) from a 1.6L NA. That's basically the same HP and torque as the Ecotec 1.8L NA...

 

[Screamer4]

Good Point Screamer4, my buddy has a Mazda SPEED3 with the Direct Injection turbo engine. They can boost higher without pre-ignition/detonation problems because of it...

Back in March, I asked the Chevy rep at the NYC auto show why they did not use DI. He explained that a normal FI system operates at ~100 psi and is relatively cheap, a DI system has to operate at ~1000's of psi because the fuel is being sprayed directly into the high pressure cylinder and it has a much narrower time window to get the fuel in. So the DI system is more $$$, like $500 per car, so for a low-priced econo car, it didn't buy it's way in... It would add a couple MPG's.

A draw back to DI is gunk building up on the intake valves. Exhaust and gunk from the EGR and PCV gets sucked into the intake stream and could settle on the intake valve outer surface. Normally, the detergents in the fuel mist would dissolve these deposits, BUT with DI, no fuel goes past the intake valve outer surface. So DI engines need intake valve cleaning at some interval, 30K, 50K, 100K, not sure? So you would spray detergents into the intake air to knock off those deposits...

The Hyundai Accent uses DI and it gets 138 hp, 123 ft-lbs, 40 MPH(hwy) from a 1.6L NA. That's basically the same HP and torque as the Ecotec 1.8L NA...

Yeah the HPFP (high pressure fuel pump) is probably a big part of the reason DI is not in there. Delivering that much fuel pressure reliably is not a cheap proposition. I think they need to find out where Hyundai is getting theirs!

On the flip-side, it's more difficult to tune a DI car because the factory HPFPs are usually running near full capacity on the stock tune, and there aren't yet many options in the way of bigger injectors for DI cars. Adding a big power adder (like a bigger turbo) would probably mean bigger injectors are needed (hard to find) and an even higher flow HPFP (even harder to find)

So for the time being, not having DI at least has that as a benefit. Also, some OEM's have had big problems with HPFPs- BMW for instance on their DI inline-6 turbo and twin-turbo (3 series & 1 series). Maybe its better that GM makes sure they have everything well sorted out before putting it in a car that they absolutely NEED to be a home run.

 

[TravsSonic]

MacGregor, i'm gonna throw in my hat on a few things.

First of all, I own the Eco cruze, so i have the turbo motor and I can tell you there is so little lag that I seriously never feel it. Even before I got the trifecta tune, it drove just like any other car, you step on the gas and it goes. It reminded me more of a naturally aspirated car than a turbo'd car cause all the turbo's i'd ever driven did have lag.

secondly, the cost of an engine replacement without warranty is substantially higher for the 1.8 versus the 1.4. this is the numbers straight from GM's online parts ordering site.

Engine, cruze - 1.4l - 1.4L
2011 $3,611.11

Engine, cruze, - 1.8l - 1.8L
2011 $5,555.56

gmpartsdirect.com: Alternate GM Catalog here's the site, just put in that your looking at a 2011 chevy cruze to verify it.

 

[Memphis]

Still want that 1.8L MacGregor? Cheaper it is not to maintain and or replace.

 

[blackphoenix]

wow.. that 1.8l is more expensive then the lsj and i think the lnf.. thats crazy

 

[buzz wrecker]

Good Point Screamer4, my buddy has a Mazda SPEED3 with the Direct Injection turbo engine. They can boost higher without pre-ignition/detonation problems because of it...

Back in March, I asked the Chevy rep at the NYC auto show why they did not use DI. He explained that a normal FI system operates at ~100 psi and is relatively cheap, a DI system has to operate at ~1000's of psi because the fuel is being sprayed directly into the high pressure cylinder and it has a much narrower time window to get the fuel in. So the DI system is more $$$, like $500 per car, so for a low-priced econo car, it didn't buy it's way in... It would add a couple MPG's.

A draw back to DI is gunk building up on the intake valves. Exhaust and gunk from the EGR and PCV gets sucked into the intake stream and could settle on the intake valve outer surface. Normally, the detergents in the fuel mist would dissolve these deposits, BUT with DI, no fuel goes past the intake valve outer surface. So DI engines need intake valve cleaning at some interval, 30K, 50K, 100K, not sure? So you would spray detergents into the intake air to knock off those deposits...

The Hyundai Accent uses DI and it gets 138 hp, 123 ft-lbs, 40 MPH(hwy) from a 1.6L NA. That's basically the same HP and torque as the Ecotec 1.8L NA...

All the Hyundai cars that have DI recommend using Top Tier fuel (more detergents) to avoid this issue. They also recommend using a fuel system cleaner if you don't use top tier fuels. FWIW, just looked at Sonic owners manual, and they also recommend top tier as well. My $.02...

 

[RichieRocket]

All the Hyundai cars that have DI recommend using Top Tier fuel (more detergents) to avoid this issue. They also recommend using a fuel system cleaner if you don't use top tier fuels. FWIW, just looked at Sonic owners manual, and they also recommend top tier as well. My $.02...

Hi buzz wrecker, not sure if you understand the reason for the carbon/soot/oily gunk build up on the OUTER surface of the intake valve, like where the valve meets the stem. Detergents in the fuel DO NOT avoid this issue.

In most cars you have EGR and PCV outlets into the intake stream. This gunk travels down to the intake to the valves and builds up on the outer surface of the intake valve.

In a regular, old tech, EFI, the injectors are up-stream of the valves, so the fuel (and detergents it carries) can clean the valve stem and valve outer surface.

In DFI, the fuel gets squirted directly into the cylinder, so no fuel (and detergents) touchs the intake vavle outer surface. So in order to clean the intake valve stems and outer surface, you'd have to spray detergent into the intake air-stream...

Having said all that, I saw an article that said as DFI technology progresses, the engineers are redesigning the intake systems:
"There is no simple fix for engines that are prone to carbon build-up, Chick says. What’s needed is a complete redesign of the crankcase ventilation and exhaust-gas recirculation systems to prevent particulates from getting through." quote from article in Edmunds, June 2011
Direct Injection Fouls Some Early Adopters - AutoObserver

So I don't know if Hyundai has designed the problem out yet or not...BUT the detergents in the fuel will not help this problem.

 

[AxelRipper]

Just want to clear this up right now: Current production engines (at least GM) do not have EGR, other than the diesels.

 

[RichieRocket]

Just want to clear this up right now: Current production engines (at least GM) do not have EGR, other than the diesels.

AxelRipper, you are correct, at least for the 1.4T, I found this article:
http://www.media.gm.com/content/med...en/2010/July/0725_cruze/0725_cruze_powertrain
"Cam phasing also eliminates the need for conventional exhaust gas recirculation, by optimizing the amount of exhaust gas in the combustion chamber."

However, there may be some other manufacturers that still do, quote from link in previous post:

"All modern gasoline engines return some crankcase and exhaust gases back through the intake manifold in order to help control emissions, but, according to Chick, some exhaust-gas recirculation designs are “dirtier" than others. Some, he said, are less-effective at preventing the passage of tiny bits of oil, carbon and other particulates that eventually get baked onto the intake ports and valves."


I really wish Chevy choose to offer DI on the Sonic(without the carbon build-up problems), but they didn't...

 

[MacGregor]

Touch My Sonic TURBO!!!

Thanx Buddies,

Yins hae convinced me to buy a Sonic TURBO just as soon as the LTZ is offered in the AUTO TRANNY persuasion. Geeze! EVERYTHING I read about Sonic is Super Positive! It MAY be a VW Golf Ball Buster! Did you see the Sonic fold-out ad in the latest Car and Driver?

MacGregor