Anyone know anything about exhaust design?

[timwilky]

Originally Posted by Berlin

Nice piece of kit Tim! Do you have to know the variables for the system (temperature, initial flow rate. etc)? Must these be measured first with a prototype then remodelled with the software or are the automatically generated?


C

Sorry, don't know, I would have thought base operating parameters would be reasonably well established. I have a meeting with our head of computational engineering who is a CFD god next week, (that's why I have his software on my dev systems) to talk through some operational issues. I will ask him for a few driving lessons

Last time I did any gas flow was back in the 1970s way before CFD was more than a pipe dream as the then mainframes were solidly booked for weekend/holiday FI runs

I would however be a little concerned as to how the gas flows flows can be efficiently optimised for scavenging/performance and fuel consumption etc. but the thing of most interest is how the hell do I get it to sound swwwweet.

accordingly, Aprillia spent more time on the sound of the new V4 exhaust than the performance side of things. 150 exhausts just to get the right note.

C

Originally Posted by Berlin

accordingly, Aprillia spent more time on the sound of the new V4 exhaust than the performance side of things. 150 exhausts just to get the right note.

C

They are Italian...


After reading this ive decided that im going to try something similar to the RSV crew and put a jointer underneath from the bend on the back cylinder to just next to the header joint. This might work to slow down/redirect/ make weaker the pressure wave that apparently causes the lul at about 5K rpm.

Wish me luck... Though I think its going to be next month before I can get me a 2nd hand exhaust collector to play with

If it's a development exhaust, why not add butterfly valves into the joiners so you can play with the amount of opening or close them off completely so the differences show up. When you know whats best, weld the butterflies in place (open closed, semi closed).

C

Originally Posted by Berlin

If it's a development exhaust, why not add butterfly valves into the joiners so you can play with the amount of opening or close them off completely so the differences show up. When you know whats best, weld the butterflies in place (open closed, semi closed).

C

Interesting idea... Im not out to lose top end though ha ha.

I think ill try the little pipe first. Ill keep you posted

Cheers for the help!

So it's been a while since this was updated... was any progress ever made?

Has anyone ever been able to lay hands on an M4 system to see what size pipe they use (that seems to be the most popular full system since it gives a solid 7hp gain across the board, when the bike is tuned).

If I can get the piping dimensions, I could probably fabricate one up myself using parts from summit racing (I've built several car exhausts that have turned out pretty nice). I'd just rather reverse engineer their system rather than do the trial and error method to get it tuned in.

I was thinking if I used the factory header pipes, and then upsize from a 1.5" factory pipe to a 1.75" midpipe, into a 2 into 1 collector that was 1.75" to 2"... throw a 1.75" crossover pipe about 6-8" up from the collector, and then flow into a 2"in, 2"out, 12" glass pack mounted about 18" back from the collector... that would give me along enough pipe to keep the bottom end, while the pipe diameter would increase top end and the crossover pipe would keep the "dip" from occurring in the mid-rpm's and widen the "power-hump" a little bit.

I am using "best-guess" engineering methods, rather than an a CFD and acoustic simulation software package. These engines aren't exactly high-tech, so I don't think it'll matter that much if it's not "perfectly tuned".

Honestly, the only reason I'm bothering to try this out is because the exhaust on this bike is wrecked beyond repair and I'm too cheap to buy an M4 or Yosh system for $750+shipping.

Anyway... if anyone has measurements on that piping, please, let me know.

Cheers.

[yorkie_chris]

I've got an M4 system.

BTW I don't think leo has the crossover and that doesn't suffer from the dip in the middle

Would you be willing to take some measurements for the D-I-Y types? If I can get some good measurements to fabricate from (I just need the piping diameters in the various sections), I plan on doing a write up in the DIY section including photos, tech-drawings, and a parts list (probably going to source most of it from summit racing and jegs).

Cheers

[yorkie_chris]

Yeah no bother, might even be tempted to make one or two myself if people are interested. What do you need just the ODs?

Originally Posted by yorkie_chris

I've got an M4 system.

BTW I don't think leo has the crossover and that doesn't suffer from the dip in the middle

The Leo Vince doesnt have the balance pipe...but with one fitted to it the increase in torque is about 2bhp..

Found the M4 works best all round..the worst being the Micron and Hindle - bore size too narrow. Have just got one from the States and took off the Hindle that was fitted...plus 3bhp mid range and 1bhp top end..the lad said the actual on track difference was very noticable how the bike pulled.