[Baldeagle]

https://automobiles.honda.com/accord-sedan#specifications

Can someone help me interpret this? The fuel economy attachment at the bottom is off Honda’s website (above) for the 2018 Accord. I’m not quite sure how to read it.

As a start, we know the CVT is offered only with the 1.5T. Therefore we know the 1.5T-CVT Sport is rated at 29 city, 35 highway, 31 combined.

However the 6MT does not seem to specify which engine it describes (or does it?). It appears to describe the 1.5T-6MT. Surprisingly it seems the 1.5T-6MT and CVT have the same highway fuel economy – 35 mpg. Isn’t that odd given the 1.5T-6MT is geared higher, ≈2,300 rpm at 60 mph versus ≈1,800 rpm at 60 mph for the CVT? (This is for the same 19” wheels. The 17” wheels get 38 mpg highway.)

If you look further, there appears to be no clearly stated fuel economy rating for the 2.0T-6MT. (Could Honda have mistakenly omitted it?) The 10AT-2.0T is rated at 32 mpg highway (19” wheels) and 34 mpg highway (17” wheels). If no specific fuel mileage rating is stated for the 2.0T-6MT, should we assume it is the same as the 10AT? I find that very hard to believe given the 10AT cranks about 1,500 rpm at 60 mph verses about 2,150 rpm at 60 mph for the 2.0T-6MT. You’d think the 10AT would get better highway fuel economy, and maybe it does. But given that the 1.5T-6MT and CVT are the same, it makes me wonder.

I am curious to learn more about turbochargers. With NA engines, lower rpm implies wider throttle opening and lower pumping losses (on the intake side). That is what boosts efficiency and fuel economy. However, if turbos maintain low boost on the highway and that low boost eliminates intake vacuum and therefore pumping losses on the intake side, does that negate the benefit of lower rpm for better highway fuel economy?

If the MT Accords do in fact get the same highway fuel economy as their CVT or 10AT counterparts, that’s great. The last-gen MT fuel economy penalty may no longer apply. Wouldn’t that be nice?

.

 

[UnknownJinX]

Here is the Canadian version, which is much better as it separates the two engine options.

MT is still a bit worse at fuel economy in terms of combined. LX 6MT(available only in Canada, ha!) gets 29.8 MPG combined versus 32.7 MPG of LX CVT. Sport CVT gets 30.9 MPG combined.

But MT does better on highways. Just slightly.

Sport CVT gets 34.6 MPG on highways while Sport 6MT gets 35.1 MPG.

Sport 2 10AT gets 31.8 MPG versus 32.2 MPG of Sport 2 6MT.

To convert, 235.215 / (l/100km number) = (MPG number)

 

[Baldeagle]

Yeah. Better highway fuel economy for the MT despite higher RPM? What’s going on here? I like it, but why?

 

[vinuneuro]

Good news for the 2.0 6MT owners. Fuel economy in turbo cars is a black box.

 

[UnknownJinX]

Seems like American MPG numbers are rounded to whole numbers, which masks the slight advantage 6-speed gets on highways.

Funny how we still mostly use MPG in Canada, yet they use L/100km on their websites. At least it's more precise at 1 decimal place so you can see the slight edge MT has in EPA testing.

Yeah. Better highway fuel economy for the MT despite higher RPM? What’s going on here? I like it, but why?

When you don't have the answer... Welp, we are doomed.

My best guess is that MT doesn't need to run a pump or anything as splash lubrication takes care of it. The RPM difference between the 6th gear of 6MT and 10th gear of 10AT/highest possible of CVT is small enough that the trans loss in the clutchless transmissions become a bigger issue.

(Gonna be honest, I don't understand the details of FI very well. After all, all the cars I have owned are NA...)

 

[Graycar]

If the MT Accords do in fact get the same highway fuel economy as their CVT or 10AT counterparts, that’s great. The last-gen MT fuel economy penalty may no longer apply. Wouldn’t that be nice?

"Nice?"

Wouldn't it be more relevant to ask, Who cares?

 

[UnknownJinX]

"Nice?"

Wouldn't it be more relevant to ask, Who cares?

 

[Baldeagle]

"Nice?"

Wouldn't it be more relevant to ask, Who cares?

You don’t care? I’m shocked.

The 9th gen V6-6AT gets about 5 mpg more on the highway than the V6-6MT. A little of that was VCM but most of it was longer gearing. I accepted that 5 mpg penalty in exchange for the rewards of shifting myself, but I didn’t like it. Who wants to waste fuel for no reason? Now, with turbo charged engines it seems that is no longer a sacrifice we must make. (I didn't see that coming.)

 

[jrock645]

So, wait... I’d thought this shift to these crappy small turbo engines was all a out MPG’s to satisfy CAFE regulations? These numbers look the same as the 9th gen 2.4L to me at first glance. Marginal improvement, if any. Am I missing something?

 

[Baldeagle]

My best guess is that MT doesn't need to run a pump or anything as splash lubrication takes care of it. The RPM difference between the 6th gear of 6MT and 10th gear of 10AT/highest possible of CVT is small enough that the trans loss in the clutchless transmissions become a bigger issue.

(Gonna be honest, I don't understand the details of FI very well. After all, all the cars I have owned are NA...)

I’m learning too. I’ve not had any time for “fun research” but I suspect the answer relates to pumping losses, as in the ease of getting air in and out of the engine.

In some ways an engine is like your lungs, both pump air. We inhale; “stuff happens- respiration” and we exhale. With an engine, it inhales through the throttle plate and intake manifold; “stuff happens- combustion” and it exhales though the exhaust system. Back to our lungs, imagine trying to inhale through a thin straw verses a fat garden hose (same length). The thin straw would require much more effort and energy. That is because you are fighting a vacuum inside the straw. That vacuum resists your lung’s expansion in volume. In an engine, that expansion in volume is the piston going down during the intake stroke.

Anyway, I don’t want to get too detailed in my analogy, but a similar concept applies to an engine. If the throttle plate is nearly closed, not much air can enter the engine and it is like the engine is trying to inhale through a thin straw. It must fight a big vacuum in the intake manifold. Under light load, that is the case because that is when the throttle plate is nearly closed; your foot is barely pressing down on the gas pedal.

With a naturally aspirated engine, the lower the rpm, the more throttle you need to produce a given amount of power. You need to hold the gas pedal down more at lower rpm. More gas pedal means a larger throttle opening. A larger throttle opening is now like trying to breathe through a garden hose verses a thin straw. The engine doesn’t strain as much to inhale. It can pump air easier. That is why NA engines get better fuel economy at lower rpm.

But a turbocharger changes that relationship because it pushes air into the intake manifold, which in turn reduces that dreaded vacuum. Back to the lung analogy, it might be like having an air compressor on the other end of that thin straw forcing air through it. You won't have to strain as hard to inhale. And with enough pressure (boost), the air being forced into that thin straw may even inflate your lungs for you. That would make it very easy to breathe.

Bottom line, I believe a turbo reduces pumping losses, improves efficiency/fuel economy and rpm does not change that relationship by much. If I am close to being right, the questions now are about the degree of change. How much boost does the engine hold on the highway? Is it 1psi or 5 psi? I truly have no idea. How much boost is required to affect pumping losses? What is the actual difference in boost at 1,800 rpm verses 2,600 rpm? Does the lower rpm imply less exhaust velocity and therefore provide less boost? Can extremely low rpm hurt turbo efficiency? And yes, to your point, a MT's greater efficiency over any AT may play a part too. I don’t know enough about this to identify which variables even exist in this equation, let alone to understand how engineers maximize them. But it is a cool concept. At least I think so.

 

[enne]

1.5T-CVT Sport is rated at 29 city, 35 highway, 31 combined

Surprisingly it seems the 1.5T-6MT and CVT have the same highway fuel economy – 35 mpg.

These numbers look the same as the 9th gen 2.4L to me at first glance. Marginal improvement, if any. Am I missing something?

They look the same as the 6th gen 2.3 L also, haha. A little better city (29) but highway and combined are not really better than my 19 year old Accord... On a 17 gallon tank that I only use about 13 gallons of, I can get about 400 miles with just daily driving, city and highway. That's about 30 MPG combined... On a long highway trip I have gotten it up to as high as 40. Mine is a 4 speed automatic.

 

[Kamdog]

The 1.5 gives slightly better fuel economy with about the same performance as the 2.4. I wondered, myself, why they ditched the 2.4, which was a fairly new engine and performed well. Maybe there is more room to grow with the 1.5? If they want, I bet Honda can get 20 more horses out of it pretty easily.

 

[enne]

Maybe that's what I was missing, the new ones have 192 HP, vs 148 and are cranking that out of a smaller engine, with turbo. But they're also hauling about 311 lbs more [curb] weight than a 6th gen.

 

[Kamdog]

Maybe that's what I was missing, the new ones have 192 HP, vs 148 and are cranking that out of a smaller engine, with turbo. But they're also hauling about 311 lbs more [curb] weight than a 6th gen.

So that is 30% more HP with probably 10-15% more weight.

 

[enne]

I can't math, so I don't know if that actually is the reason. People think all programmers are also mathematicians... Nope.

 

[g60_corrado_91]

So, wait... I’d thought this shift to these crappy small turbo engines was all a out MPG’s to satisfy CAFE regulations? These numbers look the same as the 9th gen 2.4L to me at first glance. Marginal improvement, if any. Am I missing something?

Welcome to the world of EPA...when you actually utilize the turbo, which most people DO, you'll realize that a similarly powered, larger displacement N/A engine will achieve the same or better mileage. Ever notice how most people accelerate from lights decently hard and then slam on the brakes instead of using the engine to brake? EPA needs to revise their methodology.

Case in point: Porsche's previous gen Boxster/Cayman with the N/A boxer 6 got the same mileage as the new boxer 4 turbo in the 718. Yes, the 718 has more power and torque, but it loses that magical N/A response and feel, not to mention one of the greatest sounding engines. There are countless examples of this. Ford's "Ecoboost" (what a joke of an engine design IMO) in everything from their Focus/Fiesta ST's to their F-150's gets worse mileage than their competition. Meanwhile, you have 455hp Corvette's out there that'll get almost 30 on the highway, and they're heavier than they used to be in the C5/C6 generations.

Now I'm not saying turbo cars can't get good mileage. My 2006 Mk5 GTI with 233whp at the time use to do 30-33mpg cruising at 70mph. Honda's 1.5T has already proven that it can do over what the EPA says. But I also know a lot of Focus ST guys and they struggle to get more than 24 in mixed driving; my GTI would do 27-28 and that was before mileage was really a huge concern (when 30mpg was a good number). I guess they figure most people want the turbo torque and efficiency. Having driven both (I daily a 2015 Mazda 3 2.0L with half the power of my GTI), they both have their pluses and minuses. Oh well, I guess there's no going back.

 

[UnknownJinX]

Case in point: Porsche's previous gen Boxster/Cayman with the N/A boxer 6 got the same mileage as the new boxer 4 turbo in the 718. Yes, the 718 has more power and torque, but it loses that magical N/A response and feel, not to mention one of the greatest sounding engines. There are countless examples of this. Ford's "Ecoboost" (what a joke of an engine design IMO) in everything from their Focus/Fiesta ST's to their F-150's gets worse mileage than their competition. Meanwhile, you have 455hp Corvette's out there that'll get almost 30 on the highway, and they're heavier than they used to be in the C5/C6 generations.

Now I'm not saying turbo cars can't get good mileage. My 2006 Mk5 GTI with 233whp at the time use to do 30-33mpg cruising at 70mph. Honda's 1.5T has already proven that it can do over what the EPA says. But I also know a lot of Focus ST guys and they struggle to get more than 24 in mixed driving; my GTI would do 27-28 and that was before mileage was really a huge concern (when 30mpg was a good number). I guess they figure most people want the turbo torque and efficiency. Having driven both (I daily a 2015 Mazda 3 2.0L with half the power of my GTI), they both have their pluses and minuses. Oh well, I guess there's no going back.

If I knew the Ecoboost 'stang only has 260 BHP on 87 octane, I would have challenged that idiot I know with his Ecoboost to a dragstrip.

The Corvette's case is interesting, especially from an engineering perspective. It works because the engine is actually so torquey that, even at low RPM, it produces enough torque just to keep the car going at a constant speed. It's pretty much just idling on highways, which is why it can be really good on gas on highways. Very few cars can actually do this.

People with hot hatches don't really drive that conservatively... I can imagine them hypermiling one tank just for s&g, but not the whole time. If they do, they bought the wrong car.

 

[g60_corrado_91]

People with hot hatches don't really drive that conservatively... I can imagine them hypermiling one tank just for s&g, but not the whole time. If they do, they bought the wrong car.

Haha this is true! But sometimes just cruising on the highway in your hot hatch and getting close to 30-35 is nice. Mk5-Mk7 will do that. Focus ST's struggle to get upper 20's on the highway! Hell, my friends old Mk4 R32 was doing 24-25mpg on the same trip to Tail of the Dragon back in 2009 when I was doing 30-33.

 

[Kamdog]

I get 29 MPG on the highway with my 535, doing 65-70. When you use the power only when you need it and the situation calls for it, yeah, you get better fuel economy with a turbo. If you are frequently balls out, your MPGs will suck no matter what.

 

[14v6]

So, wait... I’d thought this shift to these crappy small turbo engines was all a out MPG’s to satisfy CAFE regulations? These numbers look the same as the 9th gen 2.4L to me at first glance. Marginal improvement, if any. Am I missing something?

Also, doesn't the 10th gen weigh less? Need some real world data.