87mm pistons/hp question

[AsleepAltima]

im looking for people that have dyno'd before/after with 87mm pistons.
more specifically, going from stock bore to 87mm. just curious if the power difference was noticeable on the dyno and what effect it had on boost; ie lag time, full boost rpm etc...

[STR8E180]

I run 88mm
I don't think difference is noticeable

[AsleepAltima]

i run the 87mm in my sr, but there was too much time between my engine being torn down and rebuilt to notice any differences. i do want to say that i THINK my turbo spools faster, but who knows. im asking because in a v8, you definitely noticed a difference if you go 1mm larger (.040). of course, thats spread over 8 cylinders, but you get what i mean.

[Hashiriya415]

What happens when you bore a cylinder first you change the size and location of the port openings, some ports just get smaller, transfer ports that are angled up are now positioned higher (change the port timing) ports such as the exhaust are lowered, most porting will include raising the exhaust port, every time you bore the cylinder your lowering it (considerable power loss at higher RPM's, your increasing the trapped volume of the cylinder so bottom end power will be slightly higher). As the cylinder gets thinner it will loose it stability and ability to maintain its shape and is more prone to warping.
By going over bore your adding weight to the piston, on engines equipped with a counter balance you have to re-balance turning parts.
Boring an engine is principally a method of extending the usable service life of an engine block it has a side benefit of allowing for, not creating more air flow. Air flow is the key to power. The smooth uninterrupted flow of air into and out of the combustion chamber and how much volume you can compress into and out of that chamber will dictate how much power your engine will make.

[AsleepAltima]

What happens when you bore a cylinder first you change the size and location of the port openings, some ports just get smaller, transfer ports that are angled up are now positioned higher (change the port timing) ports such as the exhaust are lowered, most porting will include raising the exhaust port, every time you bore the cylinder your lowering it (considerable power loss at higher RPM's, your increasing the trapped volume of the cylinder so bottom end power will be slightly higher). As the cylinder gets thinner it will loose it stability and ability to maintain its shape and is more prone to warping.

huh? theres no material being removed from the deck... the cylinder is being opened more to accommodate a bigger piston. i think youre reading into it way too much...

[codyace]

Nothing worthwhile enough IMO to claim as a gain

[ForeignMuscle]

What happens when you bore a cylinder first you change the size and location of the port openings, some ports just get smaller, transfer ports that are angled up are now positioned higher (change the port timing) ports such as the exhaust are lowered, most porting will include raising the exhaust port, every time you bore the cylinder your lowering it (considerable power loss at higher RPM's, your increasing the trapped volume of the cylinder so bottom end power will be slightly higher). As the cylinder gets thinner it will loose it stability and ability to maintain its shape and is more prone to warping.
By going over bore your adding weight to the piston, on engines equipped with a counter balance you have to re-balance turning parts.
Boring an engine is principally a method of extending the usable service life of an engine block it has a side benefit of allowing for, not creating more air flow. Air flow is the key to power. The smooth uninterrupted flow of air into and out of the combustion chamber and how much volume you can compress into and out of that chamber will dictate how much power your engine will make.

Nice Google search. Too bad this is not a TWO STROKE! Lol

Op, the answer is no. One millimeter is nothing you will notice.

[drscooper]

What happens when you bore a cylinder first you change the size and location of the port openings, some ports just get smaller, transfer ports that are angled up are now positioned higher (change the port timing) ports such as the exhaust are lowered, most porting will include raising the exhaust port, every time you bore the cylinder your lowering it (considerable power loss at higher RPM's, your increasing the trapped volume of the cylinder so bottom end power will be slightly higher). As the cylinder gets thinner it will loose it stability and ability to maintain its shape and is more prone to warping.
By going over bore your adding weight to the piston, on engines equipped with a counter balance you have to re-balance turning parts.
Boring an engine is principally a method of extending the usable service life of an engine block it has a side benefit of allowing for, not creating more air flow. Air flow is the key to power. The smooth uninterrupted flow of air into and out of the combustion chamber and how much volume you can compress into and out of that chamber will dictate how much power your engine will make.


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