IVA Friendly silencer

[Bonzo]

Thank's Dave

Just out of interest, what are the basic dimensions of the GSXR can ?
Oh & what size pipe enters the can ?

It'll not be too long before I make my exhaust manifold up & still havn't decided on: 4 - 2 - 1 or just 4 into 1 I guess knowing the manifold to silencer pipe size will de the decider

Andy

Thank's mate

May I enquire as to the origin of your bike can ?

Lost track of bikes a long time ago !!?? .... In fact the last bike I rode was very early Yamaha RD 125 twin .... Was race tuned though & was s**t your pants scary at the time

[davidimurray]

Ronnie

I will check out the dimensions next time I'm down the garage - from meory the inlet pipe is 2 5/8" OD and connected by a 4 bolt flange. There are some more pics here - http://www.haynes.co.uk/forums/showthread.php?t=4119 The can itself came from good old Ebay.

With regard to exhaust configuration it really depends on what you want. The different arrangements do not give you any more power - they just move the power and torque up and down the curves. Generally the longer the pipes, the lower down the curve the peaks will be. If your not familiar with the theory, it is basically that wherever you have a change in volume you will get a wave reflected. If you time this wave to be in sync with the exhaust port open you will create a negative pressure and actually suck exhaust gas out of the cylinder (giving you more space for fresh charge on the next intake cycle). If you look up helmholtz or organ pipe theory, you should be able to calculate for your engine for a certain RPM how long your exhaust runners should be. If you need any help let me know and I could probably dig the calcs out - good excuse for a spreadsheet!

For my own car, which will be mainly for the road, I plan to use a 4-1 and the longest primary runners I can package tidily as I would prefer a good low/mid range power than the max HP somewhere up the top of the rev range.

Out of interest Ronnie are you planning to weld up your own exhaust? I'm going to have a go at doing my own from scratch in stainless. Seems like a good challenge and one of those jobs that will probably be a complete pain in the a** but a satisfying one. Most bits seems reasonably easy to get hold of - the only thing that amazes me is the price of weld on merge collectors - yet to find any below about £55

[spud69]

It is one of these Ronnie:

http://cgi.ebay.co.uk/Honda-Fireblad...item2ea9a41ecc

Obviously not for that price either.....

It also had the extended outlet with rolled edge, although it has come a bit loose now. It has the same 3 bolt flange with a 50mm inlet, had to move the bracket for the roadster but the can itself works fine.

For the Zetec, same for CVH, i used a Focus ST170 4-2-1 and modified to fit. Is a high flow exhaust and works a treat, also a bit quieter with the less restrictive manifold.

AndyH

[Bonzo]

Dave

Many thanks for the superb reply

As ever mate .... A very full detailed piece of technical information

Yes, i'll be fabricating my own manifiold.

I had wanted to fabricate a full, mut's nut's mirror polished stainless but circumstances have dictated otherwise for the time being.

Earlier this year, I decided that time on my build was becoming more important than saving money by doing things the hard way !! .... I really do want to complete the build this year.

So spending a fair bit more than I planned but keeping a lid on things by not buying too much Bling ( That can come later )

This is what I have bought to fabricate the manifold

4 - 2 - 1 Manifold kit

Mild steel but decent quality & price for the amount of parts

Fortunately for me .... The one sent out to me was the wrong one, it was the 4 into 1 kit .... So the seller sent me a new set of pipes to make the 4-2-1 manifold & didn't want the other pipes retuned .... So both options open to me

Andy

Thanks for the info mate .... I'll keep my eyes peeled fro a suitable bike can.

I am sure one wil turn up by the time I am ready .

[davidimurray]

Cheers Ronnie

I should really add that with a 4-1 you will get a bigger 'lump' in your power/torque curve down low - compared to two smaller lumps higher up with a 4-2-1. Some people will say that a 4-2-1 provides better mid-range. To be honest with you the only way to get a good exhaust system is to build a few and try them. We built an adjustable setup on a dyno once which was interesting to play with - but to be honest the difference was only a few hp moved around. It never yielded massive changes in performance. Th same theory also applies to your intake system - if you have a negative pressure wave you also have a positive one. Hence you should try and tune your intake runner lengths. The big question is does it really matter? You see a lot of cars around that produce great hp numbers - but are undriveable - stuttery throttle, poor mid range. Fine if your a flat out circuit racer but no good on roads or twisty circuits. I've seen cars that have 10 or 20 hp down on the rest obliterate much quicker cars on paper because they ar so driveable. Anyway enough of a rant.

Those kits look good - I did consider them but thought I should really go the whole hog and go stainless. Not got all the bits yet, but guessing it will cost me somewhere about the £160 mark for the bits. Try having a look at various bike cans from any of the big 1000cc bikes - GSXR, R1, SV1000, CBR/Fireblade, Bandit 1200 - those should get you started. Search for the standard cans as so many people swap them you shouldn't struggle to find one. The only issue can be the end pipe and whether it has enough radius on it not to melt your rear arches.

Cheers

Dave

[Bonzo]

Thanks again for your help Dave

I have managed to snaffle a standard Bandit one on flea bay for £15 .... Got a couple of broken mounting studs but got to be worth a punt at that price

Never found a stud that I havn't been able to remove yet .... Sod's law says this'll be the first time

[davidimurray]

Ronnie

Good deal on the exhaust. Will give you spare money to spend on all the other bits i've reminded you about

If you can drop me your email address I've got some good bedtime reading for you on the subject of exhausts I can forward over.

As I feel - I've been looking at the numbers for my 1800 Pinto. Assuming that the exhaust valve opens around 55 degress before bottom dead centre (that's a guess, anyone got an exact figure?) and that I want to tune for around 4500RPM, then using a 4-1 configuration I need runners around 41" (1041mm) long - less the 55mm inside the cylinder head so runners about 1m long to the collector. If you then calculate the pipe diameter for each runner, that comes to 1.34", I was planning to use 1.5" pipe to match the ports so that bit is good. Doing the same for the pipe to the silencer gives a diameter of 2.68" and my silencer takes a 2.5" pipe so should be close enough again