i usually use 1:1 having 86:86
but noticed using cast internals that the reliability is low at 8000rpm
however 1:0.8 using 92:75
using cast internals that i can rev up to 8000rpm and the reliability is 50
shame i always used same bore and stroke as 2jz (86x86) but that seems unreliable with cast
the disadvantage of the 92-75 bore/stroke is size, its bigger and might not fit everywhere
Bore/stroke ratio is meaningless within the confines of the game, really. The best stroke is the longest you can use without impacting the reliability of the connecting rods and pistons. The best bore is the largest you can use without causing excessive valve float or creating an engine which is too large for the application. There is no direct correlation between the two. Using an arbitrary “magic” bore/stoke ratio on every engine only results in a lot of poorly optimized engines. That’s my take, anyway. 
I did some testing about that a while ago and came to the conclusion that generally undersquare engines have superior performance, weight and economy, however as you’d expect they are limited from ultra high-revs by the strain on the rotating assembly. Another thing you have to be aware of is that smaller bore engines have smaller valves and cannot move as much air through the engine as an engine with bigger valves which restricts the engine. Same goes for exhaust manifolds.
On the other hand oversquare engines are more affected by valve float which absolutely kills top end power, meaning that for higher RPMs one must use more agressive cam profiles and quality on the top end and that is bad for economy and price.
@Killrob
what do you think about this
btw how displacement calculated??
86 bore * 86 stroke * 4 cylinders
How displacement is calculated? Google it, seriously, Google it.
As far as I remember killrob has said that within the game, bore and stroke don’t really matter in terms of power and torque, only displacement as @oppositelock said.
But I have done some tests and I came to similar conclusions to @Awildgermanappears.
Yep, note in particular that airflow issue limits forced induction in particular, hence the limiting the size of the conpressor.
i read something about bmw m engines bore and stroke, they use a bigger stroke than bore. not good for high redline but good if you want power earlier delivered
BMW uses slightly undersquare design (nothing crazy as a truck engine) and I seem to recall some engines in the porsche boxer being undersquare as well.
I might be wrong, but I read somewhere that undersquare design is more efficient because the flame(?) generated during the combustion expand more faster in an undersquare design compared to an oversquare design, thus being more efficient.
By the way, don’t be cheap and use nice internals with healthy amounts of quality when designing performance engines. Regular cast internals in the 2000s are a big no-no.
Its simply because the I6 engine BMW used started as a 2.3l , if you try to max out that you NEED to go long stroke.
Because the bore center-center limits the max piston size.
Or you need a totally new engine design.
There is no best stroke and bore to use, it all depends on application and where you want to place your Helmholtz resonances. Before understanding those you can’t really say anything about “what is best”. Currently in Automation those resonances are not modeled, but will be once we have the engine designer revamp done.
i know what cast is a no go in performance engines, but sometimes you want a engine for the masses,
“cheap horsepower”
usually i make engines with the best internals the year has to offer.
you cant run 3 bars of boost on cast 
You wouldn’t run 3 Bar of boost on most things anyway 
