Two sides of the same coin...

[aim]

One of the biggest questions in the automotive world of the last 15 years...

http://www.iwsti.com/forums/2-5-liter-litre-factory-motor/147127-sti-evo-engine-question-whats-differences.html

Good read, unbiased opinion. Explains a bit about the dynamics of it all.

[Koom]

Can't be assed reading the whole lot at the mo but do they go into the physical differences in the two engines?

i.e. bore to stroke ratio of the two, rod/stroke ratio etc.

The fact that the Subaru is horribly over square and is like it's designed to have it's power band somewhere way up high, whereas the 4G63 being nearly square (from memory) has better piston velocities/accelerations lower in the rev range to spool bigger turbo's (as well as not having 15 metres of headers pre-turbo).

(I got a bit obsessed with this a while ago and did some comparitive maths between a bunch of common performance motors. The EJ range is way out one end of the scale and the 4G variants at the opposite end of the scale. Only engine that came close to having the same dynamics as an EJ20 is an RB26 which has huge potential but I personally think its helped by being an inline 6, plus more capacity)

[aim]

Not quite the same technicality, more a laymans comparison. It presents reasoning with what you might encounter in the real world. I have never driven and STi OR and Evo, so wouldn't really know what you encounter however. At the very least it sparked further research on my behalf.

[BC5RA]

It's also a comparison between a 4G63 and EJ257.

And the 2.5 still won't make the numbers.

[aim]

 BC5RA said:

It's also a comparison between a 4G63 and EJ257.

And the 2.5 still won't make the numbers.

No it won't make the same numbers, that's all touched on it the post

[Guest]

Evo's and gsr's do make good power on budget mods compared to Ej20/25's. I love my mitsi's but still daily a subaru. They both have there +'s and -'s and if someone Say's otherwise they are ignorant. compairing evo 1 23 to Sti v1 2 3 Imo the evos win hands down, I have seen them do low 11sec pass's on stock long blocks and gearbox's and last seasons of drag racing.

[Koom]

 BC5RA said:

It's also a comparison between a 4G63 and EJ257.

And the 2.5 still won't make the numbers.

I was sort of generalising from an EJ series vs 4G series as they are worlds apart. Pretty much every other engine that I analysed sat somewhere between them. From the physics point of view, the EJ257 has an even more oversquare setup and slightly worse rod/stroke ratio than EJ20. Does have the trumpcard of capacity though but seeing as it is only 100cc short of the RB26, it seems to struggle to keep up.

The other engine that I was surprised to see right down the other end of the scale near a stroked 4G63 is the B18C.

[Old Skool Subbie]

 

Inline motors are more robust than boxers. Due to their design, boxer motors don't dissipate heat as well as an inline.

The boxer motor can dissipate heat very well. Allumium cools quicker.

You have have more surface area to dissipate heat.

Ive noticed Alot of modern cars bearly have any where for air to go into the engine bays.

Some wee inline fours ive opened bonnets on, and they give you a exetreme blast of heat in the face.

Dads flat 4 powered car infact runs too cool. Going to have to cover the grill.

Strength on the block depends on the manifacture.

They can be very strong.

[ODB]

in conclusion: all subbies should run 3.0 twin turbos?

[Guest]

 ODB said:

in conclusion: all subbies should run 3.6 twin turbos?

Fixed

[Old Skool Subbie]

 caged']

[quote name='ODB said:

in conclusion: all subbies should run 3.6 twin turbos?

/quote]

Fixed

I rather 3.0. 3.6 fitted with flexble con rods

[Koom]

The 3.6 just has rotated cap's on the conrods so that they can be accessed through the oilpan area rather than having to take the pistons off before splitting the block. The rods are still straight. Good luck trying to find something aftermarket (i.e. stronger) though.

[newsuba]

That post was a crock of pooz.

If boxers are so bad why have Porsche persisted with them for nearly 50 years ?

I don't buy the better handling argument either.

Same example; Porsche 911's have their engine hanging out way behind the rear axle, albeit with 50 years of German stubbornness they have made the 911 into one of the best handling cars around.

The latest 911 GT3 RS has just won (UK) Autocar's Best Drivers' Car for 2010.

[Guest]

german boxer engine also over square

Subaru needs to poach a few german engineers

[ReubenH]

"Due to their design, boxer motors don't dissipate heat as well as an inline."

I got to this and stopped reading. Porsche will still making air cooled boxers till 1997 FFS. 400hp twin turbo air cooled boxer no less, according to wiki.

[Koom]

 Qwerty said:

german boxer engine also over square

Subaru needs to poach a few german engineers

I noticed that the only EJ variant that was more oversquare than the 3.3L turbo Porsche motor was a destroked 2.35L. But it does have a big capacity advantage so its not going to take it 3 days to reach the boost threshold on a 400hp turbo. I don't know what the Porsche's redline is or where the main part of its powerband is either? I'd guess that you'd want one of those making power up high which the oversquareness will help as long as the rest of the system is setup towards topend power aswell?

[Guest]

GT2 RS 390kw

100.00 mm × 76.40 mm

And it doesn't even have a FMIC...

[BC5RA]

 Qwerty said:

GT2 RS 390kw

100.00 mm × 76.40 mm

And it doesn't even have a FMIC...

GT2 RS has 455kw.

GT2 390kw.

[Guest]

Makes the point even better... there is nothing wrong with a boxer engine.

[Flat4]

The RUF CTR2 came out with a 433kw air cooled boxer (3.6l twin turbo), and was one of the worlds fastest production cars in 1997.

[aim]

GT1 The only mid engine 911 ever produced.

[Old Skool Subbie]

Man that 911 looks pretty dam nice

Just read this quote... :

 

theres a reason they bought the rights to make flat motors from porsche ^^.

Subaru did not buy the rights form Porsche..

Subaru did buy the Rights of a newer flat 4 from the Borgward Group when they closed up in the 1960s.

They got the design rights from a Lloyd 900 arabella engine and improved on the design.