What's the difference b/w flat 4 and inline 4?
 

Sorry if this is a noob question but please clarify for me. Thanks

Inline 4 IIII

flat 4 ==


does that help?

Inline 4 . . . Think every small displacement car on the road.

Flat 4 . . . Think Volkswagen Bug (cylinders are opposed to each other).

Please clarify.

Whoo hoo! Sounds like the Subie versus lots of other companies debate. j/k :)

What type of differences would you like to know about?

Some things I can think about are:

1.) layout
2.) crank differences
3.) power delivery
4.) space
5.) forced induction
6.) wear
7.) modification
8.) reliability
9.) balancing

Thanks,

jcnel.

IIII > cylinders are upwards > Move up and down
== > cylinders are sideway > moves from left to right or right to left

Thanks for the clarification :lol:

it has nothing to do with the turbo..

an inline 4
http://autozine.kyul.net/technical_s...h_2ndforce.jpg


a flat (horizontally opposed)

http://autozine.kyul.net/technical_s...ooth_boxer.jpg

Thanks again for all the fast responses {thumbup}

Clicky for pictures and animations of simple inline, V, and horizontally opposed engines.

You're going to get a lot of info on the flat four from Subie, because its a little 'less known' out there. That's good though, and to you're benefit because you'll get quite a lot of info. Subie does have a few points they like to push about the flat four, for marketing reasons ...

From myself...know that both the inline four and flat four have both a lot of history, and if either design is well made they both are really good motors. They're are tradeoffs between both styles though...anyways...Subie likes to point out that:

1.) The flat design opposes the opposite bank of cylinders and therefore is easier on parts, especially the crank.
2.) The flat design provides better mounting options in the chassy, improving the car's overall balance.

For the inline four the benefits are:

1.) all cylinders are in a row allowing a 'one-piece' design on the head, intake and exhaust manifolds.
2.) Block casting is a little easier allowing for a stronger bottom end with less work to get it cast there.

In the turboed world inline fours have an easier time routing exhaust pulses from the inline head promoting good turbo spool. However, with a really good system built for a boxer four spool is pretty good on them also.

Inline fours run a little hotter overall in the head portion of the block, allowing a more consistent heating and more consistent thermodynamic performance. This translates to a little better emissions. Boxers tend to run a little more erratic in terms of heat flow, and that has to be designed with a little more caution. I think this was one of the reasons of the triple catalatic converters for the USDM WRX emissions system.

Manafold design is also a really intricate thing to nail down in a boxer. You seperate the intake flow trying to run to each cylinder bank. Most companies do a really good job of this now, so its 'almost' a non-issue.

Oh...can't forget the 'sound!' issue. Boxers are little more open and deep rumbling on their note...inlines are kinda whiny. The EVO however (couldn't resist) is one of the best sounding fours because I think it crackles in the higher revs, which sound SO COOL!

Does this help?

jcnel.

Jcnel, thanks for taking the time to do the write up on the differences. I really do appreciate it. I didn't even know that the scooby's were flat 4's until I read an article that compared the Sti and Evo.