GS450 2 into 1 Exhaust Lengths?

[SVSooke]

I think Pete's experience proves it can work OK with a 2>1 but in theory the exhaust pulses are to far apart or to close together for the perfect scavenging to work.In theory the 4>2 on most GS's aren't ideal either, the way they "should" be is like this:

With 1&4 and 2&3 paired up.Funny that most bikes run just fine with1&2 and 3&4 paired up:-s

 

[Guest]

With 1&4 and 2&3 paired up.Funny that most bikes run just fine with1&2 and 3&4 paired up:-s

Isn't All twins 1&2 or 3&4, I wonder what the theory is to that ?

Also interesting: All gs500's are 2 into 1, And all aftermarket gs450 exhaust's are 2 into 1.

Mac

MAC

 

[Guest]

Interesting... now I'm wondering if my uneven headers are actually a good thing?

 

[koolaid_kid]

You might be losing 2-3% of your power. Since you might see a 5% increase with headers, that means you may only be gaining 2-3% (once you tune the carbs, of course).
Trust me, on a 450, you won't notice the difference. All aftermarket systems are 2 into 1, if for nothing else than the weight savings.

 

[lake_harley]

A thought occurred to me about headers and exhaust pulse timing. I have a background in circle-track racing, stock cars and modifieds. A small block Chevy has an uneven firing order if headers are matched up 4 into 1 based on the left and right sides of the engine. There are headers that pair up the even-firing-order cylinders, where each of the collectors has a mix of right and left bank cylinders, to evenly space the exhaust pulses. Cars with these 180 degree headers can easily be picked out of a pack of cars on a straight, just by the distinctive sound. In years at the races, I have yet to see that a car with 180 degree headers ever did any better or worse than any others. Lots of factors in play on a dirt oval track, no doubt, but I don't think I ever saw one of the 180 degree header cars win, but then the % of those cars was always very low. I think too, that dyno results would have made them more popular if the HP results were there, or if there seemed to be more advantage on the track.

I'm not saying I'm right, but the direction I'll probably go is to not worry about theory and build the 2 into 1. My bike will probably never see a dyno anyway. I do appreciate the topic coming up though. It's always good to think a bit.

Lynn