Quote:
Originally Posted by Cole_Robbie
I'm a little confused as to how restricting exhaust flow can increase performance. I thought it would do the opposite.
|
Well it does in a way but it is complicated.
And the internet is full of so called young experts on line that simply dont know what they are talking about.
I will get to that in a bit.
Here is what I did I took the race pipes off and ran right off the headers.
The bike lost all up hill power until I could get the rpm's to around 4000.
Then from 4000 to 7500 it screamed.
I would roll back on the throttle and it just got loud and and very slowly gained speed.
That is with the 120 jets in.
What happened is by removing the restriction I leaned out the fuel mixture.
This can and will burn valves.
So I put the racing pipes back on and got my low end torque back.
The other day when I pulled the air box off it wouldn't even run.
I had so much air coming in there wasn't enough fuel in the mix to burn.
This was very lean and to prove it I pulled the plugs and they were white.
So I bumped the main jet needles up 1mm and put in the 140 jets.
Now there was a wee bit of black smoke coming out when I hit the throttle.
Running a wee bit rich.
Put on the open fish tails and the black went away this is because it leaned out the mixture again but not much just about right.
Plus even with open exhaust I had a ton of low end torque and horsepower due to the 140 jets giving me more fuel.
So here is the deal my filters will be here tomorrow they were supposed to be here today but tomorrow it is.
I have to have a muffler on my bike by law.
The law doesn't say how loud it just has to be there.
With a wild guess with the filters on and the baffle in I should be just about right.
So this is how you lose power with open exhaust.
That hole in the resrictor plate is like 5 times bigger than the stock exhaust I took off.
The bike sounded like a car from the Jetsons cartoon with them on.
When I bought the bike I made them give me the race mufflers for free.
Plus I wanted the stock mufflers.
What I have is a set of factory stock mufflers a set of factory race mufflers a set of drag pipes I made myself and the fishtails.
I dont know where my books are I loaned them out and never got them back.
here is link.
https://www.google.com/url?sa=t&rct=...uZXfCBVI68YL1A
Now lets get to some other things people have misconceptions about.
They will say drag racers have open exhaust.
Well they also have forced induction AKA blowers and they run at full throttle.
The shorter you exhaust pipe the less torqu you will have without that blower.
Cam profiles.
There are three main things lift. duration and overlap.
the lift is how far open the valve wil go.
The duration is how long it will stay open.
And overlap is the one that gets people.
This is the degree or length of time the both the exhaust and intake valve are open at the same time.
This is why the race engine sounds rough at low RPM it isn't running right.
But once you get into higher rpm the exhaust gas will help suck fuel into the engine if you have them going into a collector.
Again this isn't as big a deal with forced induction.
The show cars with the exhaust stacks and carburetors are all show and no go on the street.
All hat and no cattle so to speak.
If I have made any mistakes here feel free to correct me.
But one last thing.
Unlike a car I have two separate intakes and two separate exhaust.
You have to take this into consideration too.
They are basically two separate engines connected to each other when it come to intake and exhaust.
Quote:
Originally Posted by AlittleSalt
I'm confused for the same reason Cole wrote above ^^^
I never thought about it this way but,
(Quote) "I don't really care if it annoys people.
It is debatable but I feel that if at least one person can hear me and keep me from getting ran over it is worth it."
I'll look at noisy bikes differently now. When I used to drive, I always gave more space for motorcycle riders.
Separate but sort of related:
MY Opinion only - I like very quiet exhausts - Loud diesel engines bug the heck out of me - I can't stand the ones that people make louder and smoke more. And Glasspacks for cars and little trucks...why?
|
Salt I know what you are talking about the rich RUB's on the Harley's.
Most of those people wont give me the time of day much less wave at me.
The reason is I am a so called Dirt Ball.
They will pull up next to me and rev their loud motors and look cool and turn their noses up at me.
Then when the light changes they take off like in a drag race and dont even look for cars running lights.
I wait until the coast is clear and then take off.
They are still hammering it.
I will come up on them at around 4000 RPM and they give it more gas to stay ahead.
I will just toy with them.
The only bikers that are friendly to me are the other old school guys p0eople on sport bikes and the Bandidos.
The loud smoking trucks is just plain silly.
They sell an aftermarket kit just to make them blow smoke.
Worth