Kawasaki Sportsbike Riders Club - Australia - Online Forum

Ripped from another forum where I made the same post:

Well, the more and more I think about it, the more possible it is to do, and the more I want to do it.

Now, as many of you would know, me and repsol built our own cans for our CBR250Rs. Now, its time to do something a little more professional and serious. I want to build a full stainless exhaust system for my ZX7R.

Now, why a full system? From what I hear most of the restriction on the 7R is in the heads, or something along those lines so just gettin a can wont give the dividends you'd hope for. And hell, why not.

Now, at the moment I'm in the information gathering area and assessing the viablility of the project. So I've got some questions, and I'd really appreciate constructive criticism, things I haven't thought of that i'll need to think about and provide for, and possible solutions to problems. So, here's the situation.

Materials:
Going to be fully stainless steel, with a mirror finish. Stainless is pretty dirt cheap anyway.
No problem gaining access too materials, I work in a stainless steel fabrication workshop.
Fibreglass, we got $10 last time, came up a bit short, so this time $20-30 odd should do the trick.

Labor:
Me, and at least 4 fully qualified and experienced trademen (all with minimum 6 years as a qualified trademen [not including apprentice years]).

Tools:
Full workshop, so no problem.

So all in all, it shouldn't be hard to build, hell after all, all it is is a bunch of steel tube bent and stuck together, a good few hours should see it done really. And, best of all, dirt fuggin cheap, considering a full akra system goes for $1200+.

Now, things I need to know. In order for me to order the right grade stainless and all that kinda thing, a few things I need to know so it doesn't burn/melt/blow up.

1) What temperature do the headers need to be able to handle? (12500rpm redline).
2) What temperature does the exhaust need to handle?
3) What pressure will the tubes need to handle?
4) How strong will vibrations be on the steel/welds (they'll be full penetration welds anyway, so stupid quesiton I guess).

Anything else I need to think of?

Now, last time we built cans, we just did a simple straight through. But, now I've learnt a lil bit about back pressure I want to do it a bit more properly. Luckily for me, one of the trademen also works on a drag car team so knows a fair bit about it, moreso his cousin (GSXR-1000 '04 very sweet) has a couple spare yoshi pipes, so we're gonna pull one apart and basically attempt to somewhat replicate it.

Next thing, what style of system?

As it looks, i've got 4 roughly 32mm (guess) round tubes coming from the headers, down into a junction where it connects to a single, roughly 50mm tube. A few questions here.

1) Is it wise to make the tubes bigger? Say 38mm into 75mm?
2) Should I go for a 4-1 or a 4-2-1 system?

I'm guessing I could just basically replicate the existing junction and make it flow better (apparently its very restrictive stock).

Headers, going to get some from a wreckers (NT i'll ask you bout them melbourne lot again in awhile probably!), see exactly whats going on, and if any modding can be done.

Now please, remember this is just in its first inital beginnings. All criticism is welcome, provided its constructive, and you bring new light on the situation, and hopefully some sort of solution.

dunno, what i read from the pommy sportsbike world website was that a full system for the zx7r was an unneccessary expense for little gain because the kwaka stock pipes were already very good. The big benefit would be in getting a decent lighter weight can. What are the legalities of fitting what amounts to a race system
I'm not a mechanic or exhaust specialist but i suspect that increasing the diameter of the exhaust could result in high temp damage to your exhaust valves.
Other performsnce mods to consider
-jetting the carbs
-ignition advancer
-zxr750 crank for stroking (expensive but very effective from what i've read and heard)

Yeah, I will consider the jet kit, K&N air filter and the such in times to come (ie when I can afford it).

The thing with this is, it'll be absolutely dirt cheap, a custom mod I can brag about, and it'll have some benefits.

Weird what you heard bout the stock exhaust system, cos all I hear is that its very restrictive.... Can you link me to where you got this info?

How will increasing the diameter of the pipes effect the temperature? If anything I thought it would actually cool gases as there is more room for them to move?

Not having a go here mate, I just want to make sure I research everything thoroughly before I go and start altering things.

see here and also the link inside it........

http://homepage.ntlworld.com/webzxr/zxr ... bowl.htmly

this is from http://www.sportsbikeworld.co.uk
END CANS AND FULL SYSTEMS:

Ok, as well probably all know, the market is crammed full with aftermarket exhaust systems. Why? Because the standard end cans weigh a ton due to all the padding to keep them quiet and pass emissions tests. Typically, an aftermarket end can (say a Micron Carbon Fibre end can) will weigh 1/3rd of the original Kawasaki item, or around 4kilos.

Standard Japanese downpipes (the 'manifold' in car speak) are so well developed these days, that it is very difficult to improve on them, that's why full systems like Yoshimura or Akrapovic are so expensive (like £900!). It's because they have to spend bucket loads of dosh to better the standard systems!

So for once the Japs have done us a favour, and all we have to do is buy an end can. The end can we bought for our 1st ZX7R was a MICRON Carbon Fibre race can. Bolted straight on, no worries, and with just the Dynojet kit to balance it all out, it gave 122BHP and the most beautiful torque curve you ever saw. This time, because our new ZX7R is a different colour and styled more on an 'endurance' bike (like Suzuka 8 hours, Le Mans), we needed a metal end can. So we've bought the new Titanium (multi coloured - looks like the colours you get dropping oil into water) QUILL. Made in the UK, guaranteed for life.

http://www.sportsbikeworld.co.uk/Bike%2 ... r/zx7r.htm

i hope this might help, in so far as exhaust temp i'm basically going on anecdotal stuff that i have heard particularly in relation to oversized system on cars

i have also read that the K&N is a waste of money for the zx7r and that you are just better off removing the mesh around the stock filter (xtra 2hp)

From some research I've done, and i could be wrong, but for ZX7's Hindle seem to have had alot of great results, so far as racing goes, back in the 90's..

kempy...

mate
there are 2 problems here as I see it
1st...
there is a little problem with what material you wanna use.....
exhaust grade SS isn't shiny...its a dull matt colour
even if polished...
that's the stuff they use for engine pipes
and
it isn't the stuff that is used for exhaust tips....
why????
the shiny stuff discolours with high temps....
like a chromed header pipe does.....goes rainbow colurs....
and also won't stand the heat straight out the port
and
2nd
unless you are copying an existing header, pipe and can design
(from Yoshi or Leo Vince or Akrapovic or whoever)
...that is pipe size, pipe length, collector size, collector length
etc...
you can end losing mega amounts of power....
why
you need to be able to measure exhaust flows,
exhaust pulses, exhaust temps etc...to get the best out of a system.
and
BIGGER is not necessarily better, when it comes to zorsts!
Airflow (exhaust speed) can suffer if the header pipe is too big
and especially if it does not match the port size
I won't go into all the techinical shite here....
but suffice to say...it don't work.

cheers

Skip the exhaust idea and go in for manufacturing s/s front stands.................keep Mina quiet that would

Wouldn't it be more important to pull the engine down and work the heck out of it, rather than just trying to milk an extra couple horses from the exhaust... ie. head, cams, bore/stroke

Or have you already had the engine done???

no don't......
can just see mina flogging on the 'net......
shiny rust free 'made in Oz' bike stands............

Rossi wrote:Skip the exhaust idea and go in for manufacturing s/s front stands.................keep Mina quiet that would

Keep Mina quiet? Now there's the Pepsi Challenge!

Did I say that? No it wasn't me! Come on Mina old buddy ol pal, you know I'm kidding ..

[ducks swinging arm from Mina]

As mentioned the zx7r headers are pretty good and you don't get that much out of a full system. You will get 5 hp from a good end can though.
Forget the K&N and just remove the mesh under the std air filter. Also mod your air ducts to be straight thru and toss all the resonators from underneath them.

The main advantage in changing the exhaust system will be it will last longer. The one on my zx7r started rusting at the junctions....

Smitty1955 wrote:exhaust grade SS isn't shiny...its a dull matt colour
even if polished...the shiny stuff discolours with high temps....
like a chromed header pipe does.....goes rainbow colurs....
and also won't stand the heat straight out the port

Hey Kempy, I've stayed out of this untill now, but I've given it some thought. I'm currently moding the system on my 7 at the moment. The stock primaries (down tubes) are a GOOD. I am looking into changing the balance tubes though. I will make the junctions between them smoother, allowing better cross flow. Still investigating which primaries to link and in what order ie 1-2, 3-4, then 2-3, or 1-3 and 2-4?
The primary length from stock is ideal as they have been measured and designed to match the cames in the bike. They're right from stock.
However my headers, as did Madkaw's, have rusted at the welds at the collector. I've purchased a new collector from Megacycle to replace the stock one. From here the system will be stainless, via a slip on arrangement.
The first half of the system will be wrapped in a glass tape from the head to the collector to maintain head are therefore gas velocity. My ideas here is to just make the most out of the system that has already had a shit load of R&D done on it by the big 'K'.
As for the stainless. I cant expain this as it's contrary to Ian's thoughts. We've run stainless headers and zoomies on boats before and they haven't discoloured much at all. I cant explain this but these engines make in excess of 1500 bhp. The brand we use is 'Bassett Racing'.
http://www.bassettracing.com
Maybe e-mail these guys and see what material they use.
Just some food for thought.

Matt
I was talking about the really shiny stainless that gets used in exhaust tips
Don't know the grade but if it is used in headers and engine pipes,
it goes funny, gets weird colours thru it and looks like chromed pipes when it gets hot..rainbow coloured...apparently due to the high levels of nickel and chrome in the stainless..

I have used stainless on (car) extractors and headers and the stuff that was used, was sorta shiny but just did not polish or linish up...
But most importantly does not discolour..again I don't know the grade of Stainless that I used....
just bought it from Lukey, went in and asked for the pipe

just thought I might clarify my previous post

cheers

It's Ok Ian, I wasn't having a dig. Just explaining my experiances. As I said, I don't undersatnd the hows and whys. We just buy 'Bassetts' of the shelf and run 'em coz they make massive power. About 4k for a pair of 2 1/4" into 4" straight throughs though