Why are Fuel Economy Results Different

[SurfaceUnits]

OK, you aren't going to be in the turbo while testing fuel economy.
Looks to be the same basic engine with a slightly different compression ratio

Mazda3 5-Door
Engine type Type-L3X 2.3L DOHC
16-valve 4-cylinder with VVT and balance shafts (2)

Horsepower 156 @ 6500 rpm (PZEV = 151 @ 6500 rpm)
Torque (lb.-ft.) 150 @ 4500 rpm (PZEV = 149 @ 4500 rpm)

Redline 6500 rpm
Displacement (cubic inches/cc) 137.9/2260
Bore x Stroke (inches/mm) 3.44 x 3.70/87.5 x 94.0
Compression ratio 9.7:1

Fuel system Multi-port electronic fuel injection
Recommended fuel Regular unleaded

Valvetrain 4 valves per cylinder, mechanical lifters, camshaft chain; Variable-Valve Timing

Drivetrain

Type FWD
Transmission (MT) 5-speed manual
Transmission (AT) 5-speed electronically-controlled Sport AT

Fuel Economy

EPA Mileage (city/highway)**
Manual transmission 22/29
Automatic transmission 22/29

Mazda3Speed Turbo
Engine type
Type-L3T 2.3L Direct Injection Spark Ignition
(DISI) Turbocharged 16-valve 4-cylinder
Peak horsepower 263 @ 5500 RPM
Torque (lb.-ft.) 280 @ 3000 RPM
Redline 6500

Displacement (cubic inches/cc) 137.9/2260
Bore x stroke (inches/mm) 3.44 x 3.70/87.5 x 94.0
Compression ratio 9.5:1

Required fuel Premium unleaded (91 octane required)

Valvetrain 4 valves per cylinder, mechanical lifters, camshaft chain, Variable-Valve timing

EPA, city/highway*, Manual Transmission 18/ 26
Required Fuel-Premium Unleaded 91 octane

[chop456]

Because the turbo's pushing more air/fuel through the engine? Maybe I don't understand the question. :gomer:

Every one of those Mazdaspeed gallons costs $.20 more, too.

[cameraman]

You're getting a hundred extra hp out of the same block, that energy has to come from somewhere. Design a turbo from scratch to have the same hp as the na engine and see where the mileage numbers land.

[SurfaceUnits]

So the turbo drag while not engaged is causing a 10-20% decrease in fuel mileage?

[Insomniac]

I thought the purpose of the turbo was to push more air into the cylinders, but the amount of fuel in the cylinder would remain the same, so you would end up with higher HP with the same fuel consumption. Or do you also need more fuel in the chamber to ignite the additional air?

[cameraman]

I thought in reality it was both more fuel and a lot more air.

[Insomniac]

Then you'd have to shrink the engine? And the goal would be same HP as the bigger engine, but with a turbo to get the fuel savings. I think. :)

[SurfaceUnits]

Every one of those Mazdaspeed gallons costs $.20 more, too.and you get alot better gas mileage with that more expensive fuel as well, so say the oil companies

[JLMannin]

and you get alot better gas mileage with that more expensive fuel as well, so say the oil companies

In my minivan, I have found this to be true. On 92 octane, it runs smooth and gets 10% better gas mileage - on 87, it knocks and pings kile hell and burns more gas.

In the modern era of $3 to $4 gallon gas, the 87-89-92 price points are still just 10 cents each. In the $1 gallon era, premium was a well, 20% premium in price and not worth it if your car ram well on 87 octane. At current prices, that 20 cent jump is just 5 to 7% more, so if you get 10% better gas mileage, you spend less money.

Individual results may vary, so check your mileage at each grade and purchase accordingly.

My 98 Saturn now gets the same mileage on both 87 and 92, so I buy 87.

[Methanolandbrats]

Turbo compresses the intake charge and pushes more oxygen into the cylinder. Therefore, to not lean the motor out and burn a hole in a piston there has to be more fuel added. If you want to get good mileage, stay out of the boost. Want to go fast with a little boosted motor, put your foot in it and get out your charge card.

NA motors above 9.5:1 do run better on higher octane gas because if you put rot gut 87 octane in it the knock sensor backs off the timing to prevent detonation.

[opinionated ow]

Direct Injection makes a difference too. I can't remember if it should increase or decrease the economy though, I just know it increases the power.

[Indy]

I will confirm that my turbo four gets excellent mileage if you keep your foot out of it, and lousy mileage when you use the turbo.

All I have to do is keep the RPM's down. And that sounds easier than it is. :cool:

[nrc]

Ultimately to make more power you have to put more fuel in. But a smaller displacement turbo engine can make the same power more efficiently than a larger, normally aspirated engine.

The 3.0 V6 that Mazda puts in the 6 only puts out 212HP and rates 17/25 mpg. Meanwhile, the same direct injection turbo 4 as in the MS3 put out 270HP and was rated at 19/25 in the Mazdaspeed 6 *with 4 wheel drive*. So 20% more power and roughly the same fuel mileage.

Ford plans to offer direct injection turbo engines in a lot of it's cars for just that reason. They're calling them "Ecoboost" engines because they make the HP of a bigger engine with 20% better fuel economy.

[SurfaceUnits]

the NA engine is 9.7:1 and 87 recommended

turbo is 9.5:1 and 91 required

[oddlycalm]

the NA engine is 9.7:1 and 87 recommended

turbo is 9.5:1 and 91 required
Recommended or not, most engines with a 9.7:1 compression ratio are not going to run on 87 octane fuel without the knock sensor significantly retarding the spark. There are a lot of factors such as diameter of the piston face, flame path, etc., but broadly speaking you actually need to run 92 octane to get the most out of a gasoline engine when approachng a CR of 10:1. Direct injection can help because it delays introduction of fuel until the exact right moment, but even then the are practical limits.

Since turbo charging effectively increases the compression ratio 9.5:1 is only the "starting point" and as boost increased the effective compression ratio increases as well. Compression of air creates head and heat contributes to pre-ignition many turbo engines have inter-coolers to cool the charge which mitigates the need for even higher octane fuel.

oc

[grungex]

I will confirm that my turbo four gets excellent mileage if you keep your foot out of it, and lousy mileage when you use the turbo.

Yep. I get 25-29 on the highway, under 8 on the racetrack. Best of both worlds!

[pchall]

VW is going to smaller displacement engines with turbocharging and in some instances supercharging and turbocharging. They now have a 1.4L DOHC four with supercharging for low end grunt and turbocharging for the top end power that gets better mileage and makes more DIN ponies than the 2.0L turbo that used to get stuffed into the New Beetle, Golf, and Jetta.

Of course, the 1.4L TSI engine does come with a pretty stiff price increase.

[NismoZ]

I didn't buy my turbo to "stay out of it." The thing I want to know is if Ford, GM and others are racing headlong to 1.4 litre turbo 4s "in 90% of their fleet bt 2013" WHO makes those turbos? Honeywell? I want in. $$$

[pchall]

I didn't buy my turbo to "stay out of it." The thing I want to know is if Ford, GM and others are racing headlong to 1.4 litre turbo 4s "in 90% of their fleet bt 2013" WHO makes those turbos? Honeywell? I want in. $$$

Knowing Ford and GM, probably these guys:

Chiau Cheng Co., Ltd.

http://www.allproducts.com/metal/chiaucheng/01-turbocharger_assy-l.jpg?serial=1221138316

"We make your turbo plenty cheap. No union. No strikes. No pay for workers. Only six month delay after earthquake."