Turbocharger manifold design

[Ibrahim M]

What effect the angle of the merge collector have on turbo manifold design ?

Will a acute angled merge provide better spool because less K.E is lost (due to the pipes being almost inline with turbine inlet )?

Or will a obtuse angle merge works better at that due to lower volume ?

Also when designing a twinnscroll manifold, is it okay to add a small ( about 10/15cm ) length of pipe after the collectors leading to the turbine entries ?

I am after the best spool possible, so i belive i have to keep volume small, minimize pipe length for not wasting energy, no sharp bends, keep thermal dispersion as small as possible, low thermal inertia of the manifold.


One last thing how do i calculate the gas energy from heat ? (Im a bit rusty )

Thanks

 

[gruntguru]

Thermodynamic properties of exhaust gas.
Only covers stoichiometric and leaner ratios but you can probably extrapolate without too much error.

 

[BrianPetersen]

Original-equipment manifolds place little priority on the details of merge collectors other than "aim the flow in the right general direction and not against the flow from adjacent cylinders" and much priority on having as little contained volume as possible (for keeping pressure-pulse energy high) and as little surface area as possible (for keeping heat energy in the exhaust stream and out of the engine compartment).

Don't forget the firing sequence. Try not to have overlapping exhaust pulses (using a twin-scroll, avoid overlapping exhaust strokes into each side of the scroll). Thus (disregarding second-order effects, pulsations and so forth) if you achieve this, you're only dealing with flow from one cylinder at a time, and you only need the flow area from one cylinder at a time. This is not a problem on an inline-four. It is not a problem on an inline-six if the front three are grouped and the rear three are grouped. It is a nuisance on a traditional cross-plane-crankshaft V8, which has overlapping exhaust strokes within each bank.

As for aftermarket applications, I know a guy ... https://www.instagram.com/kz_scott_davis/reel/DEUzkxFpUIM/

Even there ... it's still clear that this design aims the flow in the general direction and calls it good enough, and has as little contained volume and surface area as possible.

Thermal expansion is a big consideration with these. Designing and building them so that they don't crack, is beyond my pay grade.

 

[EdStainless]

With twin scroll the goal is bottom end, they usually max out well before redline.
This greatly improves launch and driveability.
Do you follow Might Car Mods out of AU?
The smoother the flow lines the better, but packaging often dictates the routing.
If we are talking about a smaller engine, then look at what is done with motorcycle exhaust manifolds.
The mounting flange needs to robust, but the tubes can be very thin.
With thermal cycling you either have to accept distortion of thin tubes or high stresses and cracking of thick ones.
Adding insulation helps as it reduces heat loss, size changes, keeps the engine compartment cooler.

 

[Lou Scannon]

Excellent guidance from BP. To that I will add, it is desirable to have a constant cross-sectional area from the valve pocket to the scroll inlet.