4-2-1 exhaust... which to pair up?

I'm trying to figure out which two tubes to pair up when making a 4-2-1 exhaust system... I have a '82 kz1000p which has a 1-2-4-3 firing order I believe... I was thinking of matching them up 1-2 and 4-3 or 1-4 and 2-3.... any input? thanks.

Interesting question. I would think that what's critical is to get all the tubes to be effectively equal length and the length correct to get the flow resonance where you want it.... which is affected by gas velocity and pipe diameter. I wonder if there is a reference somewhere on how to tune exhaust systems?

My silly guess would be to pair up the sets that fire 180 out (1 with 4, and 2 with 3). That's so the exhaust pulse is entering as long as possible in time after the previous one.

IMHO - Pair 1 with 4, and 2 with 3. That keeps each exhaust pulse spaced evenly. The tube length should also be as even as possible.

I understand the concept but can't offer advice, but maybe the Kawasaki engineers know about it?

I've never seen a kawasaki exhaust shaped like that

understand the concept but can't offer advice, but maybe the Kawasaki engineers know about it?

I've been searching for along time for exhaust fabrication and several derivatives there of and come up with very little...

bluemeanie is the firing order on your bike 1-2-4-3? all the exhaust I've seen for kz1000's have either been 4 to 1 or they were paired off at 1-2 and 3-4... thank you.

you would want to pair up 1-4 and 2-3. think you will run into probs with the length of the secondry pipes, as the bike wont be long enough to have them the right length. lots of very good online caculators for getting the primery and secondery dimensions and also the diameter of tube.
spend quite a bit of time building headers for aircooled racing vw's and the sience is very involved.
cheers rob

Mekial82kzp wrote:

I've never seen a kawasaki exhaust shaped like that

understand the concept but can't offer advice, but maybe the Kawasaki engineers know about it?

I've been searching for along time for exhaust fabrication and several derivatives there of and come up with very little...

bluemeanie is the firing order on your bike 1-2-4-3? all the exhaust I've seen for kz1000's have either been 4 to 1 or they were paired off at 1-2 and 3-4... thank you.

Yes, I believe the firing order on a 650 is 1-2-4-3. The 650 SR (CSR?) and I believe LTD were the only ones to use this configuration. The engineers designed the 360 degree crossover pipes for better exhaust extraction but then used stylish shorty mufflers which kind of cancelled out the power increase of the head pipes. They paired up 1-4 and 2-3. A good 4/1 uses the same concept.

I found a 4-2-1 collector on ebay that I plan on using. the inlet and outlet are pretty close if not right on the numbers I got from some online calculators... but without my cam profile I can't fill in all the fields on most online calculators. my next question would be headpipe length. one calculator said 18" is a constant length, I measured my stock ones for a 4 into 2 with crossover to be 22" or 24"... thank you. by chance do you remember a site for that vw calculator? thanks.

I was doing some research last night to verify which ones to pair up and found that the latest ZX-10R has the same firing order and displacement as a kz1000p, and I was able to find 4-2-1 systems for the ZX that way I was able to see which ones they had paired... strangly they had 1-2 and 3-4 paired up... dispite having a 1-2-4-3 firing order... than I started thinking that they did that even with racing systems because of clearance issues behind the body work of a sport bike like that.... so I researched tuner cars and found a 4-2-1 system for one and than I found that cars firing order... sents some cars had more room than a bike for exhaust I figured it would be a good comparison... I found that the car had them paired every other "firing" in the fire order. so to simplify my findings the bike used 1-2 and 3-4 pairing and the car used 1-4 and 2-3... Now I don't know... although the car had long secondary pipes and short head pipes, the bike had longer head pipes and short secondary ones... I dought it's going to matter much on a chopper but it's something I still would like to know more about... thank you.