Lets talk crossover pipes

So, here is my question to all the guru's on the board. I basically built a new exhaust for my kz900, and was having a conversation with one of my buds last evening. I basically took a 4 into 1, cut the headers and made a 4 into 2 exhaust with no crossover pipe. Bike works good, jetted acordingly but still a little boggy feeling. It has pods and 17.5 pilots and 122.5 mains, carb synced and timing spot on. He said I should ad a crossover pipe to even the flow out and it'll probably smooth it out.
Anyone have any sugestions on if this mod may help.
Thanks in advance
BD

They must of known what they were doing when they built the stock exhaust.It has a crossover and if left alone seemed to do just fine.

Really I wasn't aware of that......... Yes the stock bikes have x-over pipes, but this isn't a stock bike dude. It's been chopped, dropped and rebuilt. Working the bugs out of it now. Thanks for the reply tho' :kiss:

My understanding is that having the crossover will improve scavenging of the cylinders on the exhaust stroke as there is a slight vacuum from other cylinders.

However, the 4 into 2 header system on my KZ650 did not have a crossover built in. I didn't use the bike enough with the header on it to know how it worked and I put a stock system on it before I really started using it.

I have experimented quite a bit with my exhaust, and have found that a 4 - 1 system runs better than a 4 - 2 system. I believe it has to do with the scavenging for all 4 cylinders working together in the collector. The pulse for each cylinder pulls eshaust from the other 3 pipes. The spacing on the firing is exactly even.

With a 4 - 2 system, and if 1 & 2 go to the left and 3 & 4 to the right, and with the 1-2-4-3 firing order, each side fires twice, then rests, while the other side fires twice. Not as efficient for scavenging.

WITH a crossover, my bike runs and sounds slightly better than without. But the difference is very subtle. The low and intermediate torque is just slightly better, but almost undetectable. The sound is more even from each pipe, whereas without the crossover, there is more of a popping from each pipe. I cannot see that any harm would be done to NOT have the crossover, but it is a slight improvement as mentioned above.

In the Auto world Experts designed Tuned Headers. Doesn't mean they threw abunch of pipes together and wallah sounds cool. Equil length pipes collected evenly draws exhaust out with a minimal amount of back pressure. Still sounds cool.

Thanks guys for the input. I'll probably ad one for shits and giggles, just wanted to ask incase it was a waste of time to do. I had a 4-1 system on it before and it ran great, just didn't like the look and it got trashed last year in a crash, so did the 4-2 setup. Bike still runs strong just still a little boggy at times.
Thanks again for the input.

mzandmz wrote:

In the Auto world Experts designed Tuned Headers. Doesn't mean they threw abunch of pipes together and wallah sounds cool. Equil length pipes collected evenly draws exhaust out with a minimal amount of back pressure. Still sounds cool.

So you understand better, My exhaust isn't a bunch of pipes thrown together. All headers are equal lenght into a collector and into slipons. Same as a stock exhaust would be without slipons. I designed it off my 750 with the 4-2 exhaust. Same without xover pipe. It doesn't sound "cool", since I'm not going for the HD sound, but it looks a hell of alot better than a stock pipe. And I built it not bought it which is how I do things.
So I was inquiring to other "builders" for advise.
Thanks anyway for your input.

Thats cool you built it instead of buying. Thats what I do as well. I hope we all can get this figured out. Our Bikes are very important to us and a Happy Bike has a Happy Rider.Take Care

Yes that is true what you said. But my bike is a little upset which makes me pissy... So forgive me if I'm alittle harsh. Thanks again for your input dude, I'm happy to hear that you wrench your own bikes too.

Just a side note,All headers dont have equil lenght pipes. Tuned headers do.. Cheap cool headers looked cool and sounded cool But tuned ones Cost alot more and sounded better. But then that was a Car and where talking Bikes.

You have to remember Cylinders 1 and 4 are opposed in timing, and 2 and 3 are opposed in timing (by 360 degrees). Those are the pairs that should be combined into a pipe. 1 with 4 and 2 with 3.

If you combine 1 with 2 and 3 with 4, the pulses are unevenly timed, so one cylinder's pulse will affect the breathing in the other cylinder in an unequal way. You may even have to alter the jetting like the way they are in uneven twins (like the Honda 350 or various v twins).

(KZ 400 and 750 twins are 360 twins so they are evenly timed.)

To get around that problem, you install a crossover pipe to even things out, or combine all four into one at the same point.