1mm bore

[normality78]

Guy's,

currently my piston dia was 81mm and i would like to bore into 82mm piston use. i wonder how much significant different would it make in terms of performance?

 

[Fluffy]

okay.when u bore ur engine 1mm u will increase torque thus increasing hp in theory.based on the calculation

hp = torque(lbs-ft) x engine speed (rpm) / 5250

so,when u bore ur engine,u will increase the displacement.based on this calculations:

.0031414 x stroke(mm) x bore(mm) x bore(mm)

*the value .0031414 is for 4cyl engines.
for 6 cyl it is .0047123 ...this is just for rev.

urs is an inline four rite? :_:

 

[normality78]

Tks for the explanation. Yes, im 4 in-line. actually im aware about the calculation and also more on increasing torque thn hp.

the thing i wanna know is more on how big significant improvement to justify over the cost. i mean something like spending x amount of money but in return only gain back 10hp. worse it does compromise the reliability. so i would need to justify over it. shld the improvement on respond or gain around 30hp or more, thn it do think its justifiable

 

[Fluffy]

how much will the bore cost u actually?

i dont think it would give u 30hp gains..but it would surely improve on response.coz surely a slightly larger displacement would spit out a lil more exhaust gas thus giving a lil more momentum to turn ur turbine.

 

[normality78]

hm... the labour itself i havent check it out but the piston set will cost me around RM1.3k

 

[MitonCT26]

isnt it better if you increase stroke rather than bore as you want to increase torque right?

 

[SkYwAlKeR]

how to increase stroke??... change to larger stroker kit??...

 

[normality78]

isnt it better if you increase stroke rather than bore as you want to increase torque right?

miton bro,

i think i've reached the max stroke laio so the next thing i can do is to bore frm stock 81mm to 82mm max.

 

[Fluffy]

i think for 1.3k its not that worth it. :P

u could be upgrading ur snail rite? IMO.

 

[SkYwAlKeR]

wah, need 1.3k arr??...

drop in 1.5L block la... after that do PNP.... no need rebore la..

or like fluffy said, keep a snail inside.... hehehe...

 

[khoyos]

usually people change piston to alter the compression ratio. 1mm increase in piston bore wont bring such great diffrence, unless u get pistons that has ur desirable compression ratio.

IMHO, rather than increasing the bore (reduce reliability and the painful 1000km running in period), u would do better if u upgrade cams(for NA) or change to bigger turbo if u running turbo engine...

 

[normality78]

wah, need 1.3k arr??...

drop in 1.5L block la... after that do PNP.... no need rebore la..

or like fluffy said, keep a snail inside.... hehehe...

drop in 1.5l? what r u talking?

 

[normality78]

IMHO, rather than increasing the bore (reduce reliability and the painful 1000km running in period), u would do better if u upgrade cams(for NA) or change to bigger turbo if u running turbo engine...

hm... tks for the info bro. will think twice now. hehehehe

 

[alvin24]

Hahaha... if your stoke is long, then you might feel it lar. =Þ

But u also need to think in terms of reliability... 4G9X series engines for instance have poor reliability after a rebore.

 

[SkYwAlKeR]

drop in 1.5l? what r u talking?

err..... this only applicable to 1.3L la...
if u car 1.5L, cannot change block la... jz drop in 1.6L stroker kit....:tongwink: