2008 Mazda CX-9: Fuel Economy Update

The EPA combined estimate for a 2WD CX-7 is 19 mpg. So much for six-cylinder power with four-cylinder fuel economy.

The Enclave's fuel economy is amazing.
The CX-9's is on par.

"The EPA combined estimate for a 2WD CX-7 is 19 mpg. So much for six-cylinder power with four-cylinder fuel economy."
 
Yep, that is a shame. If the CX-7 got better than the CX-9 then it would be a great vehicle. Those numbers aren't bad for the size of the CX-9, but that little 4 cyl turbo just can't push the heavy CX-7 efficiently enough

Couple of days ago Yahoo homepage had a feature of five-most fuel inefficient -- CX-7 was among. (Made top-five? Damn!)
 
"So much for six-cylinder power with four-cylinder fuel economy."
 
-- Got to second that
 
W/ apology of non-CX-9 post --

Acura's RDX suffers from the same issue.

The problem with putting a turbo motor in a heavy vehicle with poor aerodynamics. It's on the boost all the time which defeats the advantage of a 4 cylinder turbo.

Ummm - you guys haven't had a real truck-based SUV in the fleet for some time, but it seems like this ain't appreciably better than what those SUVs managed.

I've said it before, and I'll say it again: small displacement 4-cylinders with turbos are NOT the answer to better fuel economy. In fact, in many cases, they get WORSE fuel economy than a larger displacement pushrod V-6 or V-8 would get in the same vehicle, particularly on the highway.

Mazda did not put a turbo 4 in for fuel economy., then market it that way like Acura.
Of course you would all like to think so

Oh and poor aerodynamics?
 
0.34Cd is really poor right???

The 2.3L MZR is a gas guzzler in naturally aspirated form so adding a turbo and heavy vehicle results in the obvious- low mpg.
 
Small displacement, twin scroll turbo, directly injected I4s will work brilliantly in low mass applications but not in heavy vehicles. Off boost, 2.3L is 2.3L (with air restriction problems) and moving 4000 lbs of SUV is neither efficient nor satisfying. On boost is a different story but the engine still has to work harder pushing that mass around which results in higher rpm operation. A large displacement engine with super tall gearing would yield better fuel economy due to it's excess of torque.
 
The supposedly "technocharged" RDX doesn't even use direct injection which results in increased turbo lag, lazier throttle response (due to lower compression ratio) and worse mileage.

"Oh and poor aerodynamics?
  
0.34Cd is really poor right???"
 
cd is only part of the equation. Frontal area is the big killer. All 0.34cd shows is they did a good job of cleaning up a box. You have to minimize frontal area if you want to minimize drag and you can't do that if you want to stick to the psuedo SUV theme.

Off-topic alert:
 
chavis10, the Acura RDX uses a variable geometry, a.k.a. variable vane, turbocharger that is supposed to make spool-up easier at low RPM as well as provide maximum boost pressure at high RPM.
 
Autoblog's in-depth look at the Acura 2.3L turbo I4 (HTML used due to link length)
 
firstwagon, good call bringing up frontal area in addition to drag coefficient. Having a low Cd isn't good if downforce isn't being generated at high speeds. There's usually a trade-off involved - increased drag is usually an undesired by-product of increasing downforce. The reason prominent F1 chassis designers make the big money is that they're able to find ways to increase downforce without increasing drag. Here's a cool "did you know" - the average street car has a much lower drag coefficient than open wheel race cars such as Formula 1 and Indy Cars. The exposed wheels and front and rear wings create a ton of drag. Those wings, however, also would enable those cars to virtually drive on an inverted road at 150-160 mph due to the amount of downforce being generated (think of the lift airplane wings generate a la Bernoulli's principle).
 
For example, Peter Stevens, designer of the McLaren F1, designed the facelifted 2003 Subaru Impreza (MY20004 for North America) that Petter Solberg drove to the 2003 FIA WRC driver's championship. The street version of that WRX has a drag coefficient of 0.33. It was widely regarded that the Impreza rally cars were the class of the field in terms of aerodynamics in 2003 and 2004.
 
Here's another example - The 2008 Mercedes SLR McLaren Roadster is capable of 206 mph yet has a drag coefficient of 0.376 with its soft top up (0.4078 with its top down). Then again, it does have a mere 617 hp to overcome all of the aerodynamic drag.

A similar displacement modern turbo diesel would do wonders for the CX-7 which I do consider to otherwise be a great SUV in looks and handling. It would have the torque to pull this baby around.

the RDX uses a lot of tech but it still gets bad mileage so in the end Honda might as well have used a V6 and saved some money. The Vue has taken a lot of flak for its weight and mileage but its not much heavier or more thirsty than the CX-7 or RDX. Its just heavy compared to the RAv4 and CR-V.

I think what disappoints me most about the RDX is if it was lower and lighter, it could have been a competitor to the WRX.
 
Now it's just a CRV for people with extra money to spend.

Suby- I'm aware of the variable geometry turbo in the RDX (much like that in the 911 Turbo) but direct injection with a twin scroll blower is the solution it needs. Honda just likes to do their own thing to be unique when proven technology is available and more effective.

The RDX just has a tall roof, the ground clearance is pretty much the same. '
 
Oh and the Varible inlet on the RDX, isn't always in the right position(causing long lag then over compensating), and there have been some serious reports of 4-5 second hesitation.

chavis10, it's not that easy to implement direct injection and a twin-scroll turbo to engines. Otherwise, I and others would be clamoring for Subaru to implement those on all of their global market (read: not Japanese Domestic Market (JDM)) turbocharged powerplants. The new Mitsubishi Lancer Evolution, a.k.a. Evo X, has a twin-scroll turbo but no direct injection. The JDM STI has a 2.0L with a twin-scroll turbo and no direct injection either, but the global STI with the 2.5L has neither the twin-scroll or direct injection.
 
Have you also read some of the things engines with direct injection are doing to engine oil?! If accurate, some pretty scary (for one's engine) stuff is going on!
 
Would you be kind enough to provide a link, cx7lover?
 
Or are you just making that up because...you're a CX-7 lover? j/k =Þ

suby- it's easy if you want to spend the money to develop this superior technology. GM is doing it and the replacement to Audi's 2.0T will likely add a twin scroll turbo. I see Mazda adding a twin scroll turbo in the future to it's DISI engine as well. I don't see why there's an issue outside of cost that would prohibit such a configuration.

PS- Subaru and Mitsu are still using the old school turbo methods which is fine in their narrow focused high performance products (speaking of the Evo and STi, not regular turbo legacies and Forresters). But refining the turbo experience to the next level in mainstream products requires more expensive technologies.

chavis10, remember that Subaru and Mitsubishi don't have the money and resources for R&D that larger players do. :(