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Discussion Starter #1 (Edited)
Seeing the Mirage, Focus and Fusion cars with 3-cylinder engines (and driving just fine) I wish Honda had put their original 3 cylinder in the G2. It would have scored over 55mpg on the EPA Highway cycle (and Honda could brag about beating prius).

That was a missed opportunity. At the least they could have made it an option: 4 cylinder or 3 cylinder... I of course would have picked the 3, because I love the 3 cylinder in the G1 and the Ford Focus. Small and efficient.
 

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The number of cylinders doesn't mean anything, except maybe packaging. Maybe internal efficiency, but that's way over my head. It's the displacement and tuning that matters. Our engine can barely pull our cars. It wouldn't work in a car that's 900 lbs (about 50%) heavier. Honda increased the displacement from 1.0 to 1.3. For whatever reason they decided to do this with four cylinders instead of three. I've never driven a G2, but I bet it is not overpowered.

The Focus is turbocharged and makes about twice the HP as the G2. It's mileage is lower.

Sam
 

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The original G2 gets 41 mpg on the EPA cycle.
I don't think dropping one cylinder would make it 35% more efficient to get to 55 mpg. It would have less internal friction, but have to work harder for the same power.
Bigger cylinders or a turbo would reduce the gain even further.
A long geared manual gearbox would allow for more control and hypermiling techniques; that should do more than dropping a cylinder.

Four cylinders make for slightly smoother running on low revs. And that's where my revs are pretty much all the time; 1100 rpm in the city, 1600-1800 on the highway.

I do get over 60 mpg per tank in summer weather. My lifetime average (all season) beats 55 mpg. But my driving style does not resemble EPAs.

 

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Although Ford 3 cylinder engine tend to do well in NEDC and EPA tests, sites tracking real world fuel consumption tell a different story.

Check out the RealMPG register on www.honestjohn.co.uk. Where a Ford 1.0 turbo 3 cylinder and a 1.6 NA 4 cylinder are installed in the same car real fuel consumption is usually very close.

It's usually close enough that the difference can be accounted for simply in that the 3 cylinder version has a start-stop system. Or maybe it's just the way we drive in the UK...
 

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While it's generally true that smaller displacement results in higher economy, after a certain point it starts to move the other way. Here's why:

Let's say you need to make 20HP to cruise at 65mph in the G2. If the 3-cylinder delivers 20HP at 3500rpm and the 4 cylinder delivers it at 2500rpm, the 4 cylinder would probably get better fuel economy, because you're having to rev up the smaller engine, getting it outside of its most efficient operating range (which is ~1750-2250rpm btw). The 3 cylinder can probably more efficiently make 15HP, but you'd need to improve aero and/or reduce weight to get the power needs down.

G1 3 cylinder BSFC (efficiency chart):




A larger engine does have some things working against it, such as more friction at the same RPM and, if you don't have tall enough gearing, it will run at lower load and be less efficient. However, there's an ideal engine size for producing a given amount of power most efficiently, and smaller is not always better.

Food for thought: The C7 Corvette has a 6.2L V8 that can deliver 650HP, and PopularMechanic found it delivered close to 40mpg when cruising on the highway at 55mph. It does this because in top gear, it's spinning at 1100rpm at 55mph. My old Civic was running about 3500rpm at that same speed due to the silly-short B16 transmission, and it never delivered more than 35-38mpg at these speeds.

EDIT: I should add that speed is a big variable here too, because power needs vary with speed. A 4 cylinder engine might actually have been more efficient in the G1 for cruising speeds above... let's say 70mph, because you could bring the revs down, but the G1's 3 cylinder would probably be more efficient in the G2 than its own 4 cylinder at lower speeds, I'd guess anything below 45-50mph.
 

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You still have to include the "weight" as a contributing factor also.
 

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Discussion Starter #8 (Edited)
Going from an I4 to I3 engine is 25% less reciprocating mass (pistons, rods, etc), 25% less oil resistance/splash losses, and therefore a measureable savings energy wise. A Ford Fiesta I3 gets 19% over the I4 version (36 highway to 43 highway), and I would expect a similar increase if the Insight G2 had the original I3. So the 2010 Insight scored 43 highway. +19% by switching to I3 option == 51 mpg highway

I think they should have used the I3 in the Civic Hybrid too. IMHO the four-cylinder in my HCH is overpowered & wasting gas.
The original G2 gets 41 mpg on the EPA cycle. I don't think dropping one cylinder would make it 35% more efficient to get to 55 mpg.
Perhaps I was over-optimistic, but you are mixing numbers. You are quoting combined cycle, where in my original post, I was using the HIGHWAY test. (IMHO the city test is fundamentally flawed & inaccurate & should be ignored.)
.
 

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Those savings go away if you need to rev the engine 33% higher. I guarantee the Insight's i3 could not keep an HCH1 going down the highway at 70mph with the gearing it has in the Insight, and if you geared it shorter, you'd be out of its optimal RPM range and BSFC will rise, so you might actually end up with worse economy.
 

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You're putting way too much emphasis on the number of cylinders and skipping way too much stuff in the middle. Don't you think Honda Engineers thought of this stuff and made calculations? You're mainly forgetting the required horsepower to move a certain weight. You're forgetting gearing. You're forgetting tuning. An engine that can barely move a G1 isn't going to be able to pull a heavier G2 or a Civic. The HVH1 is already underpowered worse than the G1, even with a bigger engine.

You're also ignoring the fact that the Fiesta 3 cyl doesn't do nearly as well in real life as it does for the EPA tests. Manufacturers often tune their cars to do well for the EPA and ignore real life so they can post big (fake) numbers to fool people like you. VW even tuned theirs to do well in emission tests.....

My old Ford tractor had 3 cylinders. It got terrible mileage. I wonder what Ford did wrong?

Sam
 

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But it would "pull anything" due to the gearing.
Have you checked your E mails lately?

Willie
 

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For me the 3 cylinder engine is a no go in the G2.

Simply because I have to merge into a fast stream of cars at a busy T junction every day. When I see a gap of 10 car lengths I go for it, as I know it will be up to speed before that space runs out.

Every once in a while I have something slower ahead, waiting to merge while passing on gaps I could have managed easily. I feel their pain.
I once blew the auxiliary fuse, which disables the central locking, door lights and IMA control electronics (!!!). I can't tell you enough how bad I missed the 10kW extra support from the hybrid system.

The G2 is not a race car, but it is not a slug either. It would be with one cylinder less.
 

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Discussion Starter #13
Don't you think Honda Engineers thought of this stuff and made calculations?
Yes I'm sure they did, but I think the Mitsubishi and Ford engineers are better mathematicians, and that's why they decided to put I3s in their cars. ;) Besides Honda engineers also put three-cylinders in various European cars for the same reason as the Ford and Mitsubishi guys (save fuel).
An engine that can barely move a G1 isn't going to be able to pull a heavier G2 or a Civic.
So many people confuse weight with aerodynamics. The weight is irrelevant when cruising down the I-5 at a steady 60mph. It's the air resistance/drag that matters. Yes the G2 does have a little more drag but not that much. Any G2 engine weakness is skillfully disguised by the engineers using CVT (ditto on the original G1).

BTW I drove a Ford Focus with the three-cylinder engine. It was a short trip but it gave me 70mpg on the highway (at 55mph). That's what a downsized engine can do. I suspect on a longer trip to Vegas it would give me 80+ mpg (and it isn't even a hybrid)
 

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So you are going to drive to Vegas at 55 MPH? GOOD LUCK with that..
 

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I guess you could go with larger pistons, more displacement.

You have to have something larger to move that weight and get up hills, mountains, without killing yourself.
 

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A 3 banger develops destructive harmonics above about 1.6 liters. (Assuming we don't have fancy double balancers)

3 cylinders and 5 cylinders are naturally more efficient than even cylinder versions due to their natural harmonics helping to pull and push exhaust and intake cycles.

That efficiency makes them run rougher for the same reason.

Weight to power ratios are important to us producers because Americans have become incompetent in being able to drive an underpowered car.
They have delusional views of safety thinking the power levels of even 15 year old cars is unsafe.
 

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Discussion Starter #17 (Edited)
Don't you think Honda Engineers thought of this stuff and made calculations?
I'm an engineer but I can tell you for a fact: Our decisions often get overruled by the management. I can easily picture a meeting like this one:

Engineers: "In order to save cost we recommend using the same 1.0 engine as the original insight. That will give approximately 55 highway MPG but 0-60 times will be 15 seconds."

Management: "Nope. We cannot sell a car with 15 second acceleration."

Engineers: "So you're overruling our design."

Management: "Yes."

That's how the real-world works. It isn't about making the best product. It is about what management thinks will sell. Of course many of you are not engineers, so you never experienced these kinds of meetings, so you don't understand. You assume "Engineers make all the design decisions" and that's simply not true. In reality engineers have minimal power.

P.S. If I had unlimited money I would transfer a G1 engine into a G2 car (or a HCH).
I'm confident it would work
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It may have also been that they wanted to actually sell these cars. They live or die on Auto press reviews. I doubt making the Insight an even slower more miserable vehicle would have resulted in better reviews. They barely sold them as it was.

ElectricTroy, you do not have your location shown in your profile, perhaps you live somewhere that inadequate acceleration works. Many of Honda's customers (including me) need to be able to keep up with traffic.
 

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ElectricTroy,

As an engineer in the aviation field for the last 25 years, I have to ask - have you been an engineer for long? It doesn't sound like it.

"best" is subjective. A good engineer knows that. Arrogant ones don't get it. I've seen it so many times... engineers think that diploma bestows some divine right, authority or power. They are the absolute worst. When they **** up it's usually epic.

The "best" design is one that satisfies the design criteria. Your example only takes "cost" into consideration. It's the "best" in terms of production cost, but it fails the "market viability" criteria miserably and will ultimately harm the business.

Engineers can make some monumentally bad decisions if left to their own devices because they have intense, narrow focus on whatever is important to them. They frequently deliberately ignore the bigger picture because they can't be arsed with such trivialities as "profitability".

If engineers design something, and it doesn't sell, engineers don't have a job. Period.

Saving cost on an item that won't sell is false economy. Cost is monumentally higher because there is no revenue. The G2 Insight sold poorly as-is. Switching to a 67hp 1.0L gas engine would have cost WAY more due to a much higher number of unsold units. It's even worse than that because now they have to pay to dispose of the unsold product.

Thank goodness for the good managers that consider profit when bad engineers go awry.

Thank goodness for the good engineers that have the sense to compensate for bad managers.

Lastly, please provide evidence that the Ford Fusion has ever had a 1.0L in it.
 

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Lastly, please provide evidence that the Ford Fusion has ever had a 1.0L in it.
The Fusion is marketed in the UK as a Mondeo and comes with an option of a 1.0 turbo 3 cylinder engine.

It's rated at 55 mpg(UK) on NEDC. Real world it looks like it's averaging 32 mpg for UK drivers and they're furious! Ford Mondeo (2015 on) - Real MPG | Honest John

The 1.0 3 cylinder engine is perfect for gaming the NEDC test with its glacial acceleration (0-60 in about 30 seconds), frequent stops (the car has stop-start) and low overall speeds (about half of which is spent gently decelerating). It's not so great for hauling a large car along the motorway at 70mph or driving up hills. Acutally - I'm told it's nice to drive but fuel economy isn't its strong point.

For the record, the previous generation car with a 1.6 NA 4 cylinder engine got marginally better real world fuel economy.

Edit: Interestingly the current gen Mondeo also comes in a 2.0 NA 4 cylinder Hybrid version. It would appear that it's genuinely averaging 55 MPG(UK).
 
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