Post by noday on Sept 1, 2011 17:22:56 GMT -5
some interesting charts of power v rpms for GY6 engines
these were posted on a french scooter board in a thread discussing GY6 heads and cams
www.scooterchinois.fr/modules/newbb/viewtopic.php?start=0&topic_id=3164&viewmode=flat&order=ASC&type=&mode=0
these charts are on page 3
exhaust manifold 23 x 650
I think the colors are
red stock Kymco 125 with stock valves/head
black Kymco 125cc with autotech355 big valve head
green 158cc Kymco with stock valves/head
blue 158cc with autotech355 big valve head
compare red to black and green to blue
this does not absolutely translate to a 50, cc small case GY6 engine, but expect the small case GY6 to behave in a similar manner when comparing a 50 to a 72 or 82
what it appears to show is that porting and polishing plus larger valves increases power by about 20% and shifts the power band to a lower lower rpm range (about 500 rpm) and flattens the peak somewhat.
you also see the power falling significantly from peak to 9000 rpms
9000 rpm is kind of THE magic # for the small case GY6 as with stock gearing, 9000 = 50mph
-----------------------------------------------------------------------------------------------
this is with different cams and carbs
cams are stock, a9, and juani. I do not know what juani is
green black red 125cc, carb 24mm, exhaust 23.4mm x 650mm
tan purple blue 150cc, 30mm carb, 27 x 650 exhaust
a lot more power from larger valves & exhaust plus more aggressive cam
tuning to get higher RPMs to increase speed is unlikely to work very well
comments ?
these were posted on a french scooter board in a thread discussing GY6 heads and cams
www.scooterchinois.fr/modules/newbb/viewtopic.php?start=0&topic_id=3164&viewmode=flat&order=ASC&type=&mode=0
these charts are on page 3
exhaust manifold 23 x 650
I think the colors are
red stock Kymco 125 with stock valves/head
black Kymco 125cc with autotech355 big valve head
green 158cc Kymco with stock valves/head
blue 158cc with autotech355 big valve head
compare red to black and green to blue
this does not absolutely translate to a 50, cc small case GY6 engine, but expect the small case GY6 to behave in a similar manner when comparing a 50 to a 72 or 82
what it appears to show is that porting and polishing plus larger valves increases power by about 20% and shifts the power band to a lower lower rpm range (about 500 rpm) and flattens the peak somewhat.
you also see the power falling significantly from peak to 9000 rpms
9000 rpm is kind of THE magic # for the small case GY6 as with stock gearing, 9000 = 50mph
-----------------------------------------------------------------------------------------------
this is with different cams and carbs
cams are stock, a9, and juani. I do not know what juani is
green black red 125cc, carb 24mm, exhaust 23.4mm x 650mm
tan purple blue 150cc, 30mm carb, 27 x 650 exhaust
a lot more power from larger valves & exhaust plus more aggressive cam
tuning to get higher RPMs to increase speed is unlikely to work very well
comments ?