atta boy u got it!! long as u buy on road set up it will always be a match up.. thank good we don't have to worry about that!!

billy I see u billy

I will accept your apology!! :blus h:

your slipping pops!!!!

If you stay inside the normal range of onroad manifolds, the difference will not be as pronounced, but try a 020 manifold on a onroad engine and you will se more clearly what I mean by the rpm dropping off.
An approximation is 9mm per 1000rpm (crudely), that means if you want to increase the rpm where the engine makes peak hp say from 36.000 to 37.000, then you need to shorten the manifold by 9mm. (Again this is just a theoretical approximation derived from tests).
You can read any of the common books that people start out with written by Gordon Blair, Graham Bell and Gordon Jennings. Follow up with any of hundreds of papers, look at forums dedicated to this, and you will see lab tests and math to prove it time and again.

But, again, that the engines rpm where it makes peak hp changes doesn't mean it will be faster or slower, that's why people change manifolds depending on tracks.
If the engine will reach the same peak rpm or not when making small changes can be debated to death, it's easier to just go out and test it if you feel it's important to see how much it will over rev.

Coming from a guy who is using onroad manifolds on off-road engines - I can tell you that a super long off-road manifold on an engine with higher timing will make the engine run hot and fall flat on top. A shorter manifold made the engine happier all around. I basically have an off-road engine with onroad timing using an off-road pipe and onroad header in the most unlikely of places - and it works significantly better than the super long off-road header and 053 type pipe get could. The short exhaust gave a 14% increase in top speed. I think that says something about how the pipe changes the powerband and that it can and will boost power if the timings are correct for it.

Let’s derail things a bit - pipe to port or port to pipe?

This was pulled from Novarossi site.
EDIT: I noticed that I was way late. Bunch of replies LOL.

They either changed some part numbers or have different PNs for different refions.. I use the 41016 and 41017 headers which are the “medium” and “long” versions respectively which appears to correlate to the 41616 and 41617.

Not sure the book exists if I'm honest

u miss the post I said its not a book but was on line, u been very quiet after u said basically I was out of my mind...then u see things r possible and now u don't say much???

y would anyone run an off road motor for on road ?
y would anyone run use an off road pipe for on road?

there would never be any reason even in gt class ....

don't know y u would even have any reason to worry about motor timings there are plenty of onroad pipe/manifolds to suit anyones needs.

I have used onroad engines for offroad, works great with a bit of work.
The pipes that are used in onroad and offroad is often the same, or there is very little difference. It's not like say old MotoGP pipes vs MX pipes that would be very different.

I don't think anyone is usually worried about engine timing, they run what is recommended and go on with their merry life. But that's not what we are talking about here.

Why would Anyone use proper spelling, punctuation, and grammar? I mean, you do want people to take what you say seriously, right? I don’t, but some still may..

When it comes to pipes - there isn’t much magic behind it. As I said before - the differences are going to be either/or/or a combination of different volumes, shapes, and sizes/lengths of the tuned section. Nothing mystical here - one pipe to the next is just a little bit different. In all honesty - where I have seen the most change is within the manifold. You get a much more dramatic change with the engine when you change manifolds than you ever will changing pipes. Neal has a dynongraph here somewhere I’ll try to find.

Alright guys, enough bashing for the guy lol. Change of subject.
Could someone direct me to a proper page online or explain the kinetics or dynamics of airflow (gasflow maybe??) of the exhaust and manifold? What makes one brand's pipe not recommended for another brand's engine?
And I remember somebody talked about widening the hole inside the pipe to make the car go faster at the expense of making louder noise. Could somebody explain it why? Thanks.

Gordon Jenning's Archivek

Well, i m not an engine guru by fahr lol, but there is some things that is kind of missleading or not quite related to what you compare things to :-)

Like:
Boats, their high RPM is abaout 23-25000rpms for 3,5ccm and thats a little higher than an onroad clutch engages, so you can not really compare.

onroad enignes use conical manifolds, and that also offsets things a bit.

I have very little knowledge abaout this but i have been explaind by some books and a coupple of well educated people.

When it comes to two strokes +exhaust systems and tunedpies/manifolds, alot of the buisness is abaout time - like in milliseconds.

F eks: at 30.000 rpm, exhaustport is open at y time in ms. If the charge of fresh gasses need 2.5 ms to reach back into the combustionchamber and the pipe/manifold is set up to use 5 ms then you will need a shorter manifold to achive the desired power or torque output. If you exhaust is set up to only use 1.5 ms, then you will need a longer manifold.


Ofcourse, there are alot more things like shape, flow, returncone placement and so on :-)