Wonder why Honda didn’t go with a flat engine in cars

[saz468]

I’m surprised that Honda never went with a horizontal opposed engine in their cars
they were successful when they design the water cooled flat four for the gold wing
motorcycle in 1975 and later the flat six. VW and Subaru were very successful with their flat engines. And since Hondas reputation engineering and building good engines I wonder why they never went with this engine design in their cars
another head scratcher is they never went with a straight six either
yes I understand the motorcycle and car divisions are separate but still?

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[SDAlexander8]

I think they were just really proud of their dual overhead cams design.

 

[NorrinRadd]

Probably harder to cram a flat 4 transaxle in a FWD, its shape is more suited to RWD or rear-biased AWD configs.

 

[xcoreflyup]

Honda also never made a mass production V8.

 

[saz468]

Probably harder to cram a flat 4 transaxle in a FWD, its shape is more suited to RWD or rear-biased AWD configs.

Before Subaru went AWD they where FWD with the flat four the only inline engine they had was in the Justy Subaru had the flat engine for a long time

 

[saz468]

Honda also never made a mass production V8.

True but Honda could get enough power out of their four cylinder and V6 s they don’t need a V8 I just threw the straight six in there because of of the 1978 to 1983 CBX super sport motorcycle with the in-line six air cooled engine My question was since they had great success with the flat four and six in their gold wing motorcycle why didn’t the auto division adapt this design to their cars it’s just a question I threw out there

 

[BABY NSX]

This is a really good question!

Not looking into horsepower figures between the motorcycle flat engines vs an automotive inline engine, the flat engine, at least from a performance standpoint, has the advantage of a lower center of gravity and also height. Take the Toyota/Subaru Brz/frz twins that use a Subie engine. The lower center of gravity is a plus in a perfoemance oriented car but also the lower height allows designers to use a short front end. An extreme example I saw was a youtuber that put an S2000 engine in a Subaru WRX and the engine was clearly taller, so much that the leading edge of the engine cleared the front fenders. Not only taller but longer so it would adversely effect handling since more weight was in front of the front suspension. Also I read flat engines have less vibration?

so with that being said why do manufacturers use the inline engines vs a flat engine? The flat engines are much wider than an inline engine so that may effect suspension geometry design and also it could be a cost thing as now you need 2 cylinder heads to be manufactured and maintained vs one head up on top. This I would guess is a plus to have the cylinder head up top so there’s less of an issue with running into leaking valve cover gaskets since in an inline engine gravity will bring the oil to the pan vs in a flat engine where the oil can pool in those areas and potentially leak more.

Honda I don’t recal ever having an inline 6but they did have an inline 5 cylinder engine used in the 90s Acura Vigor. It was a super smooth engine that reminded me of a smooth electric engine. Not sure why it didn’t catch on with more cars. Being a longitudinally positioned engine it required a long hood and in a world of cars getting smaller or actually enlarging passenger space without lengthening the overall length of the car perhaps they wanted to stick to transverse engines? I dunno, just guessing. Might have to do with just sticking to their bread and butter engines and keeping costs down by using same family of engines for different cars vs having an inline 4, and inline 5 and a V6 engine in the line up.

And those were all in different cars! Some cars you could choose a 4 or 6 cylinder so two choices. Some cars no engine choices. Back in 1970 you had I think 8 engine choices for a Dodge Challenger!

 

[saz468]

I read flat engines have less vibration?

Yes this is true there was a old Honda goldwing ad showing a nickel balancing on the cam cover while running at idle to show how smooth the engine was. In the early nineties I was looking at a 1986 Subaru XT turbo AWD when I test drove it ( don’t remember how many miles on it) I was impressed on how smooth the engine was compared to getting back in to my 1983 mustang the a V8 here’s a few. Pics of the Honda gold wing with the flat four and six
the silver cbx super sport with the in-line six happens to be my favorite motorcycle

 

[ayau]

Why change something when there aren’t any real benefits? Same can be said on why Subaru doesn’t make a traditional I4.

Unless an engine package provides better emissions and or fuel efficiency, then there isn’t an incentive to change an engine design.

 

[charleswrivers]

True but Honda could get enough power out of their four cylinder and V6 s they don’t need a V8 I just threw the straight six in there because of of the 1978 to 1983 CBX super sport motorcycle with the in-line six air cooled engine My question was since they had great success with the flat four and six in their gold wing motorcycle why didn’t the auto division adapt this design to their cars it’s just a question I threw out there

Good question as to the flat 4. As the the lack of the 8... they’ve never pushed either a “proper” truck that was geared around high towing capacities or a “muscle” type car. While turbo 6s have come into their own in trucks in the last decade, Honda’s Ridgeline, while having great utility, still was stuck with a J35, which still only is SOHC. No one looking for a rough and tumble truck capable of towing beyond a meager ~5k lb unibody SUV realm would give it a second look. The Accord coupe was probably the closest thing to a muscle car Honda had recently in my mind and it’s gone. They lack a proper sports car too.... and even when they did... they had their hot little F20/F22 4 cylinder.

They just never had a V8... and their SOHC V6 is kind of a dinosaur, having just got DI in the last few years. It’s been massaged a lot over the years but my god it’s old. Honda does, however... stick with naming conventions for a long time even when an engine get drastically changed... and even when older engine with the same naming really can’t transfer many parts over anymore. Otherwise, you’d be seeing K20C2 guys slapping A2/Z1/Z3 heads on and giving stock L15B7 guys a run for their money.

If they did try another “muscle” car... or a truck, they’d either have to trickle down the turbo-J from Acura or go with an 8 (probably the J these days). Their engine lineups just are too small and narrow these days and a K20C1 wouldn’t cut it in those applications. I’m sure they’ve run mules of things like Odyssey’s with K20C1s... but those engines may really be poorly suited for the job once you’re moving a vehicle 1.5x the weight of what they’re in now... also towing weight equal to the cars they’re currently in. It’s be great to see Honda come out with something more, well, new... rather than tweaking existing designs that have been around for 2 decades.

 

[Phy]

I'd love to see honda make a "traditional" muscle car one off, but that's really not their style.

 

[saz468]

I'd love to see honda make a "traditional" muscle car one off, but that's really not their style.

They do have a super car the Acura NSX

 

[saz468]

Some examples of flat engines
VW ,Subaru , Corvair, and a Ferrari flat 12

 

[Phy]

Some examples of flat engines
VW ,Subaru , Corvair, and a Ferrari flat 12

To me, it looks like a flat engine would cost more to make/maintain

 

[charleswrivers]

They do have a super car the Acura NSX

Love to see Honda make a sports car for the masses. CTR is a great car performance-wise... but a FWD 4-door 2+2 hatch doesn’t quite fit the bill for me. The Acura costs as much has my home.

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