OzVMX Forum

Clubroom => Tech Talk => Topic started by: Gippslander on March 18, 2016, 06:01:35 pm

Title: expansion chamber design
Post by: Gippslander on March 18, 2016, 06:01:35 pm

Not that I'm going to try and make a chamber because the skills are well beyond me but I see that
2 STROKE WIZARD TUNED PIPE PRO Version 5  is  $35 for "both programs" so it might be a bit of fun to see what design pipe it throws up because I will  be doing a top end rebuild in the next few weeks and  it will be convenient to put a degree wheel on the end of the crank and work out the port timing

QUESTION   – for a 74 CR 450 Husky any ideas on maximum revs?

Reason I want to know – when I have a look at the software website I can see that there are a lot of variables that I have to put in including port timing, bore X stroke but there is "target RPM" (and "target hp"), and I wouldn't have a clue what a big bore to/revs to  except to say it makes parts of my anatomy go numb – my hands of course  ;D

Title: Re: expansion chamber design
Post by: tony27 on March 19, 2016, 06:06:06 pm

Find the original specs & use where they claim max horsepower is developed as a good starting point, why go to higher revs on a big bore as your peak, look at trying to get it to hold on to power after the max for longer if you really must

Title: Re: expansion chamber design
Post by: Lozza on March 23, 2016, 10:59:19 pm

Quote from: Gippslander on March 18, 2016, 06:01:35 pm

Not that I'm going to try and make a chamber because the skills are well beyond me but I see that
2 STROKE WIZARD TUNED PIPE PRO Version 5  is  $35 for "both programs" so it might be a bit of fun to see what design pipe it throws up because I will  be doing a top end rebuild in the next few weeks and  it will be convenient to put a degree wheel on the end of the crank and work out the port timing

QUESTION   – for a 74 CR 450 Husky any ideas on maximum revs?

Reason I want to know – when I have a look at the software website I can see that there are a lot of variables that I have to put in including port timing, bore X stroke but there is "target RPM" (and "target hp"), and I wouldn't have a clue what a big bore to/revs to  except to say it makes parts of my anatomy go numb – my hands of course  ;D

6500 peak but real world 6000 rpm. If you put 70hp in the target hp I'd like to see what it throws out. As usualy the Blair based programs expand the belly and reduce the stinger size to get to the target.

Title: Re: expansion chamber design
Post by: Gippslander on March 24, 2016, 12:36:41 am

Thanks Lozza, needed somewhere to start.