Custom Chamber

[dean_werden]

Ok. So I'm new around here and have some questions about chambers im building for my snowmobile..The sled is a 1990 polaris 400 and getting a newer faster sled isnt an option or the goal of the whole thing..OK, so I did calculations from my 2 stroke tuning book and with 153 degrees duration on the exhaust at a peak power of 7500 rpm the tuned length should be 867mms BUT when i go to calculate everything else I get 304mm for a header, 406mm for a 7 degree diffuser (the length seems like alot to me), then 327mm for an 8.5 degree baffle which gives me a length of 1037?? and thats without a belly at all....so what am I doing wrong? does anyone have any suggestions or a computer program youll type all my specs into and give me some real answers....i didnt have any problems with the other pipe I made and have NO idea what im doing wrong here

[flotek]

how did you get 153 degrees of exhaust duration

[dean_werden]

with a degree wheel, i didnt think it was that much either but another motor i have laying here was about 145 so im guessing that about the norm? its also not a reed valve motor,

[mgty3whlr]

153 degrees for the exhaust doesn't sound right. You must not have the degree wheel set up properly to do your measurements. how do you have it set-up?

[dean_werden]

ok im an idiot..hows 173 sound? seems a little bit more right to me anyhow, at that duration i have a pipe tuned for 7500rpm that has a tuned length of 39 inches, 8 degres for the diffuser(16 inches) the belly is 2.5 inches, the baffle is 16 degrees(8 inches) and i have a stinger thats 12 inches..total length is 53 inches

what do ya'll think

[flotek]

that isnt right either... i think your using the degree wheel incorrectly .... it is probably somewhere around 190 .tell me the crank stroke and the the connecting rod length and the deck clearance ...i will tel l yo u the correct duration

[Mutt]

I would like to know who I can get to roll my cones for me outta 20 gauge sheet steel. Don't need em welded just cut out and rolled. Is there anyone on this board that offers this service?

[gassrx.com]

something isnt right like flowtec said...