Originally Posted by
ralphierace13
internet line goes goes in the trash!! y I said go out and test for yourself!! its funny all u guys disagree and not one person has said I have tested it on the lap counter ? do u guys practice with a lap counter? or u just go out and say ok long manifold I'm slow and short I'm still slow lol!! geez I love people that talk theory, except roeolf I'm confident he has tested pretty much everything on earth.. but really u guys mean to tell me all your years of racing u just accepted long mean top end !! lol
another thing you keep saying which is totally wrong u keep saying long manifold lower peak power !! dude no manifold increases or decreases peak power period!! get that out of your head only roll of a manifold is to speed up of delay the time it takes for the pulse wave to send back the unused portion of the fuel called scavenging and reach peak power, but u will always hit peak power no matter which one your using.. I'm talking about when u have a pipe and manifold set on just changing the length does not loose or gain power, if u said I had a 2015 set on and I changed to a 2069 then that's different one set up can give u less power but not just changing the length.
so roeolf explain the logic that if the pulse wave is sent out and on return forces the unspent fuel back in and causes the extra charge right, so what logic is it that if a longer manifold is used and takes the pulse wave longer to return that it would make sense that the power comes on faster? as apposed to a short manifold sending the pulse wave out and returning faster causing the power to ignite quicker? maybe my brain works backwards ...
I'm going to be honest and tell you that the reason why I haven't tested with lap counter, it is that I'm not racing competitive and usually run offroad when I'm at a track. I'm in this hobby pretty much only for the technical part, to develop things, it was the same when I raced full scale. But with that being said, I'm therefor interested in how we have a different opinion in this matter, what's missing to understand each other.
As a complete package: engine, manifold, pipe, clutch, gearing etc etc, I couldn't tell you what's fastest for everyone every time.
But as far as the engine alone, how that respond, I do know pretty well what happens.
I have read a substantial amount of technical papers, talked to people or read what they have tested in many places on this earth. There is no question about what happens when you change the manifold length in regards to where the power peaks appear.
But that's just the engine, and further, it doesn't tell you what happens to things like over all power and width of the power band. Part of that is that the length isn't a design parameter.
For instance, if you increase the rpm where the peak power occurs, it is likely that the power increases due to the fact that hp is a function of torque/rpm. But if you're out of the range where the engine likes it, the peak torque might go down or even the rpm spread between the two might get more narrow, so you'll end up with less Over All power even if peak power has increased slightly.
Further, the engine will not ignite the mixture any earlier only because the puls is returning any faster, the piston moves according to rpm, and the puls according to temperature. So in a fixed scenario with the temperature, the piston will be further up when the high pressure puls returns at high rpm and further down at lower rpm.
If it's too early it will push the mixture back down the transfers (which happens at low rpm), or if it's to late the puls wont have time to push in what ever fuel mixture there is in the manifold (which happens at high rpm).
But, that is only the high pressure (positiv) puls, the low pressure puls (negative) will also have an impact on how it turns out. A bad scenario at the bottom end could possibly be tuned out by the clutch for instance.
So I don't question that your lap times are better, I'm just not sure why.