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+--- Thread: Equal Length Manifold Project (/showthread.php?tid=4512)
Equal Length Manifold Project - fcp - 04-21-2013
I started work on the OM606 manifold design for my 300GD>OM606 racing G Wagon project (see my profile for the back-story)
Next on my list are exhaust headers.
Layout of RHD G Wagon engine bay + new bigger turbo means this is essential (KKD and others won't fit) and since HX35 is split housing I thought I'd take advantage of the opportunity to use the parametric and flow modeling capabilities of SolidWorks to design something that was optimal for length and volume/ efficiency.
I've spent a bit of time reading around different theories of design including:
http://www.ehow.com/info-tip_8428151_exhaust-header-length-calculation.html
But many are (I think) written with gas engines in mind and in any case what works in the real world based on people's experience is often a better start.
Anyway, I thought I'd open it up to folks here. Once I'm done, I'll publish the project as open-source with SW design files for others to use as they wish.
A final couple of points - I'm new to SW (infact to parametric modelling generally, until now I have used Rhino exclusively). I'm sure I will make some mistakes with it .. please point them out if you know how it could be done better.
Secondly - the starting design I have in mind owes much to EDH_Performance's design (http://www.superturbodiesel.com/std/thread-3199-page-2.html ) which I have chosen because 1. It should be most flexible for changing lengths/ layout and 2. It is compact and will likely fit for my purpose and 3. It just looks nice
EDH - I hope this is OK
A bit later on, I'll post up some initial files including the spreadsheet I started working on based on the article above and an initial sketch in SW.
RE: Equal Length Manifold Project - EDH_Performance - 04-21-2013
(04-21-2013, 02:16 PM)fcp I started work on the OM606 manifold design for my 300GD>OM606 racing G Wagon project
Secondly - the starting design I have in mind owes much to EDH_Performance's design (http://www.superturbodiesel.com/std/thread-3199-page-2.html ) which I have chosen because 1. It should be most flexible for changing lengths/ layout and 2. It is compact and will likely fit for my purpose and 3. It just looks nice
Oh yes, good to see that other can use what i have made
Post many pictures along the way
Good luck!
RE: Equal Length Manifold Project - Mark_M - 04-21-2013
Exhaust manifolds are always a compromise between optimum and what fits/packaging so don't get hung up on too many technicalities. a lot of the principles don't apply either with a turbo being in line, things like diameter needs to be smaller than a non turbo but obviously not too small. Primary length cannot be optimal either because the turbo will be too far away, probably wouldn't fit either. Length doesn't matter anyway because it would have to be a hell of a reverse pulse to hold the boost pressure back. Equal length is good though and as smooth and large a radius bends as you can fit in.
There is a guy down south, Mike the pipe who I was lucky to meet once. He built headers for F1 cars that were a work of art. His opinion though was that technically they weren't so good. They were full of compromises because of what they had to fit. Aerodynamics were worth more than what the exhaust could deliver so the pipes had to fit where they could and that was that. Moral, do what you can with what you have because even in the top levels of motorsport they do the same.
RE: Equal Length Manifold Project - fcp - 04-22-2013
"do what you can with what you have"
That sounds like pretty good advice for life generally :-)
I won't get too hung up on it. As you say its got to fit first and foremost. The advantage of a parametric modeler like Solidworks though is that you can set the parameters for all the stuff that matters (length, bend radii, dimensions between pipes, materials etc) and then pull and push the model around to find the optimum combination of layout. It will then export a cut list with all of the parameters that the fabricator can use to construct it.
There's a pretty good how-to video that shows it on YouTube here http://www.youtube.com/watch?v=mWcKGWQfAos
RE: Equal Length Manifold Project - raysorenson - 04-22-2013
From the linked article:
"Look at your camshaft specs and find out how long the exhaust valve opens in degrees at 0.50-inch lift. Subtract this number from 360, then multiply that by 850 (we'll call this Figure A)."
Surely they mean .050" lift, which is a number favored for pushrod 2 valve motors. The 606 will have significantly more flow below .050" lift.
Another thing to keep an eye out for is that in the formula "((850 x (360-EVO))/rpm -- 3", there would have to be an assumption made about the speed of sound in the header, which would include an assumption about pressure and temperature. Since this article seems to be SBC-centric, an adjustment might have to be made to the formula to account for pressures and temps encountered with the 606.
RE: Equal Length Manifold Project - fcp - 04-22-2013
(04-22-2013, 08:50 AM)raysorenson From the linked article:
"Look at your camshaft specs and find out how long the exhaust valve opens in degrees at 0.50-inch lift. Subtract this number from 360, then multiply that by 850 (we'll call this Figure A)."
Surely they mean .050" lift, which is a number favored for pushrod 2 valve motors. The 606 will have significantly more flow below .050" lift.
Another thing to keep an eye out for is that in the formula "((850 x (360-EVO))/rpm -- 3", there would have to be an assumption made about the speed of sound in the header, which would include an assumption about pressure and temperature. Since this article seems to be SBC-centric, an adjustment might have to be made to the formula to account for pressures and temps encountered with the 606.
Thanks for the observation. I'll need to try to digest that and think about the differences between V8 and this application. I have been looking for information about 606A cams lift, but not found much so far.
KM Cams on the other hand have quoted a racing cam at:
264-270` Duration. And 10.5-11mm lift
TDC aprox 1.5mm. Lobesep, 114`
I need to make sense of this, or factory cam specs though.
I have begun working on design in SW. 1st pass tonight which I am happy with as a start.
Selected tube is ISO 42.4 OD x 38.4 ID, 321 Stainless.
I'm working on just 1 side which I will mirror across.
Lengths so far are quite close @ around 10-30mm variation. With some more tweaking I think I can get them equal.
Flow path can also be improved I think. I notice that EDH, you have set the T3 manifold off horizontal by maybe 15 or 20 degrees? I might try this tomorrow to see if path curve is smoother.
RE: Equal Length Manifold Project - Simpler=Better - 04-22-2013
I like it
My only concern would be an unequal number of bends leading to in equal restriction. Can you run that puppy through cosmosflow (assuming they still call it that)?
RE: Equal Length Manifold Project - EDH_Performance - 04-23-2013
When i make my manifolds i always start with the sylinder that has the longest way to go, and make this as short and free flowing as possible, then i make all of the other one the same lenght and use same amount of bends
On the 190d manifold, i started with nr 6, because it was the hardest to make, then i just made all the other one as close to nr 6 as possible regarda lenght, number og bens etc...
RE: Equal Length Manifold Project - raysorenson - 04-23-2013
As I recall from reading Gordon Jennings' 2 stroke gas dynamics stuff, the number of bends have little effect on the strength of the sonic gas pulses but the smoothness of the interior walls does. There is, however, a difference between the strength of the sonic pulses and back pressure.