inlet timing

[lofty]

hi all,

ive been dabbling with the air grinder on an old SR barrel and after studying the various material out there have become a little confused regarding a sensible timing for the inlet port.. webster uses timings around 160-175 in his well respected tuning manual.. but some others (including broady) seem to think 150-160 is extreme..

what is the opinion out there.. i am looking for a sensible road tune using a ts185 piston, clubman, 25mm bored jetex, that will lug an S2 along the highway..

currently i have 170 exhaust, 123 transfer 160 inlet.. too extreme? gonna try it anyway, but interested to hear anyones opinions..

[sean brady scooters]

perhaps in your case your best bet is to cut your piston skirt ....rather than lower the inlet on barrel....................at least ,this way you can do it say 1 or 2mm at a time until you find it suits you best ,and then if you go too far.... back track by getting just a new piston.....


but especially on your scoot and weight/ areodynamics etc i would be first looking to maximise port widths.....before increased timings

[RinB]

Have a look at these threads if you havent already.

http://scooterotica.org/forum/viewtopic.php?f=5&t=26

http://scooterotica.org/forum/viewtopic.php?f=9&t=13

Like Sean has said why not look at area its not just about port degree timing
Its quite a miss conception to just think about Timing degrees, look at port area
Transfer angles into bore.

Plus on the Inlet side the tuned length & Diameter of the manifold also effects power/RPM
similar to the exhaust.

Smiffy

[lofty]

thanks for the input chaps..

i have taken a bit of care to widen the exhaust port as far as reccomended for the piston involved (ts185) and shaped it with radiused corners... ive also taken a bit of time cleaning up the dodgy SR transfers so they now are square and open at the same time rather than looking like holes a woodpecker would make..

will report back when i get it running..