Down under, an idiot and a 400F

Pipe diameter after the collector isn't so critical if I remember right. I'll try and look it up later
You don't want more than 2psi at the collector, less is better
 
I know the theory is sound on that one hillsy which is why I am looking for solutions to ensure the dual pipes are not going to be detrimental. Can you confirm for me what the effects of too large a diameter and too free flowing midpipes and mufflers is? Do you have any suggestions on how I can control this if a dual setup is aesthetically what I am after?

Currently I have the solution to run 1.25" inner pipes within the 2" outer pipes from the headers to the mufflers, however not even sure if this can be done.
 
crazypj said:
Pipe diameter after the collector isn't so critical if I remember right. I'll try and look it up later
You don't want more than 2psi at the collector, less is better
Click to expand...

Just read this after my post above. Does this mean I should be less worried about pipe diameter in this case? That would certainly make my life easier if it does. I would of course still focus on total overall length of the system after the merge collector.
 
It does Sonreir. I think you helped me with my initial calculations on the header and muffler system when I setup my spreadsheet. Essentially with a 466 motor, 8,000 RPM ideal I came out at 1.29" header diameter with a total length of 15". The tailpipe diameter came out at 1.43"however for some reason I don't have a total length calculation.

Does that sound about right?

I can share the excel file if that helps as I want to get this right as opposed to just whacking it all together and hoping for the best.
 
Head pipe diameter sounds a little large and length a bit short for 8,000 rpm on a ~117cc cylinder
360 with 378cc conversion was only about 1.25" ID about 26" long (I forget exact numbers)
I have too much information to make finding stuff easy though ::)
What exhaust gas speed were you using?
I think I used 900~1100ft/sec to get length (lots of calculations ;D )
 
OK, now I'm a little more confused than when I started! I have rerun the calculations and come up with the following (I based a lot of the assumptions in your article Sonreir so let me know if anything you mentioned for a 2 cylinder doesn't apply to a 4 cylinder):

CC: 466
Ideal RPM: 8k
Rotations per Period: 2

Ideal Header Diameter: 0.96"
Ideal Header Length: 15.1"

This is a long way off where my current headers are. These are 1.25" OD (I assume closer to 1" ID) with a length of 25". What effect does this have on the bike? I am struggling to see how I could get away with 15" as this would barely reach under the bike for a merge collector.

I have also calculated the current system length to work out how far from ideal I am. 25" header, 16" mid pipe, 16" muffler. Total 54"

I plan on running a 4-1-2 merge system in the middle, so I calculate this to require a system of 60.4"

Have I made any mistakes along the way?

So the questions I have is, what result would a wider diameter but longer header have on the header system
 
I think I have a solution to the ID. I will find some SS tube with the right ID and match the external look by buying thick wall thickness. Would that offer any issues?
 
Couldn't find the info I was looking for.
Realised the 9~1100ft/sec is acoustic tuning, gas speed is generally 250~300ft/sec.

Double the lengths of headers if they are too short to work. (15.1" =30.2")
It will be better than going to 25"
Go up slightly in diameter to compensate for bends in the pipe
you should be working with a single cylinder for headers. Use at least 1" ID pipe, 1.125" would also be OK even though it lowers gas speed
I've always said exhausts are too short ;D (intake as well, probably needs to be around 14"~16" valve head to atmosphere)
 
Sounds good PJ. I will work off 30" of header, then 16" of mid pipe and a final 16" of muffler. 62" total exhaust length. 1" appears to be perfect diameter for headers, however I assume the extra header length will lower the peak torque point, so I will go up to 1.25" to counter that a touch.

I am trying to work out how in hell I get 4-1-2 at the merge collector to exit into the 2 mid pipes however have a few ideas up my sleeve.

I couldn't resist having a test fit of the exhausts today, funnily enough its the first time the motor cases have been back in the bike for a while, but its starting to come together! The mufflers are on the limit of being too big, however I think I can make them work and with more refined fitting (rather than just cable ties and tape) I am sure they will sit a little better and start to become part of the bike a little more. Up close is where I have some slight issues with the look, however from afar they look killer, so maybe it is a fitment issue. I am sure with a human on there they will look even smaller still.

Piccies:















I will work on making some mockups for the muffler mounts in some thick Alu, then get them made on the CNC. Thinking something like this with a welded bracket on the underside of the frame rails:

GSGMufflerMountGSXRBlack.jpg
 
Looking at the angles of the muffler bracket I've decided to remove the mount I welded onto the frame near the back of the seat and instead mount a muffler bracket off the uprights instead. Not only will this clear up the rear of the bike a little more but it will also match the angles off the swing arm brace and look a little tidier. Plan is to paint the frame black and then anodise the muffler bracket black too so it is marginally noticeable. Here is a quick mockup (red x is where I will remove the mount, yellow section is the mount I will weld to the frame rail, green is a mockup of the muffler bracket:

165122c0a0d9f015d27e66e206d47b93_zps41c5673c.jpg
 
Looks damn good.


If it were me, I'd seriously think about shortening the cans about 2.5" or so, but if it's a pain to do that I'd leave it and be happy.
 
Bozz said:
Looks damn good.


If it were me, I'd seriously think about shortening the cans about 2.5" or so, but if it's a pain to do that I'd leave it and be happy.
Click to expand...

Here is that mocked up. I am not sure about it lightening the look, seems pretty similar to me and I am concerned the shorter look makes them look even more bulky (the Danny DeVito effect). What are peoples thoughts?

 
I agree there's not a whole lot of difference. I liked the look of the mufflers when you posted them, but seeing them on the bike they are just way overkill and not matching the rest of the bike. Hate to say it but I would ditch them and go a different route.
 
Yeah, I'm afraid I've come down on the "too big" side as well Ed. Nice looking units for a bigger bike, but just a bit bulky for the little 400 I reckon.


cheers
ian
 
I'm definitely sitting on the fence on this one and might follow it through before getting rid of them (I completely aknowledge peoples suggestions though they are too big). Doesn't affect much as either way I will have twin mufflers with an almost identical hanging solution. The 6 million $ question is which mufflers.

If the bike is built and they still look silly, I will see if I can get my money back out of them and get something smaller. I won't be cutting up the midpipes or the mufflers, so if I come down on the "get rid" side of the fence once I have built the mounts, then they will get boxed back up and sold for something more discreet.

The one thing I do like though is the fact they are a little overkill, they add a beefy look to the bike that I'm hoping will balance out with the front end and someone sitting on the bike. Time will tell though I suppose.
 
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