Team MightyBoy

Yeah the sizes I quoted are pretty standard.

What is the source of these 'magic numbers?'. There seems to be a bit of a turnaround in the thinking of the header sizes of late - just look at the latest exhausts on motorcycles - those engines are moving a lot more gas, but have fairly small header pipes - as opposed to the late 80's where large pipes were the go.

With these late model bikes, most of the aftermarket pipes give no more power unless you want them loud and then you might get a couple of HP if you're lucky.

They're not magic numbers, just the closest to the size of the exhaust ports. I have no idea why you'd want to go any smaller and create a bottleneck before you even get the exhaust out of the head.

The collector needs to allow sufficient space for the three pipes, so around 2" should take care of that. As for the rest of the system, 1¾ is just my seat of the pants best choice as I've seen either side of that give negative results.

With the comparitive short length of motorbike exhaust systems and difference in engines I don't think a fair comparison can be drawn. Of course if anyone has dyno proven theory on the optimum size of an MB exhaust then I'd be more than happy to hear it!

Another question. Is there a size for the length of pipe that runs from the head plate to the collector cone?

Should have my head plate cut out next week and hopefully extractors on by the end of the week!

jono wrote: Should have my head plate cut out next week and hopefully extractors on by the end of the week!

Just curious how you plan on matching the round exhaust pipes to the rectangular exhaust ports? - Seems like it's an area where a fair amount of turbulance could be produced...

sorry to sorta steal the thread but on a stoch exhaust manifold is there meant to be a flange between the pipe and the manifold im having a lot of trouble sealing this off and it is pissing me off lol. and if i have an f5a exhaust manifold on the f8b will that make any difference that would be noticeable??

u need some maniseal lol

fritz wrote:

jono wrote: Should have my head plate cut out next week and hopefully extractors on by the end of the week!

Just curious how you plan on matching the round exhaust pipes to the rectangular exhaust ports? - Seems like it's an area where a fair amount of turbulance could be produced...

Um, well that's what the exhaust guys are for! Others on here have put extractors on so perhaps they can enlighten us?

kidwithahatch wrote:sorry to sorta steal the thread but on a stoch exhaust manifold is there meant to be a flange between the pipe and the manifold im having a lot of trouble sealing this off and it is pissing me off lol. and if i have an f5a exhaust manifold on the f8b will that make any difference that would be noticeable??

tIGHTEN IT HARDER, BUTNOT TOO HARD CAUSE THE BOLT WILL SNAP..

Um, well that's what the exhaust guys are for! Others on here have put extractors on so perhaps they can enlighten us?

I've had a similar experience with getting a quote on an exhaust manifold. - The guy was just going to put round pipes over the rectangular ports. I presume this is because most people dont consider lil' suzies worthy of serious performance (or they're lazy).
Now the tricky part is deciding what to do about this. I'd imagine the only way to match the port would be to fill and grind it. This wouldn't be a cheap option I dont think. But I guess you need to consider how much you're spending vs your gain???

having a round tube welded to a square port wont make that much difference,



these are what i had made, before i went the turbo route, and yes they are square holes where it bolts to the head

If you're really worried about matching the port you can form the pipes to suit - use a big hammer and an appropriately shaped piece of metal and form the pipe to the required shape. Anyway, having a bit of a lip stops backflow into the cylinder which may be beneficial in some instances.

Thanks for your pic. So the length of pipe from the head plate to the collector cone (going from the pic) is about 30cm or so?

This is what i want.



Or maybe one of these.

Oooooh baby!

Those aren't for a suzi are they???
Where'd you find those pics? huh? huh?