Turbo Manifold - Size

[oldcorollas]

The attributes i have seen work are things done to retain heat and velocity in the exhaust gas....eg ceramic coating, exhaust wrapping and generally shorter, smaller diameter runners. No change in max power, but gains in response were made for sure.

Theories are a great place to start thinking about your application and/or look for why something isn't working but real world results are where it's at and a heap of experience here that should be considered.

LOL, thats what i was tryign to say with all that typing.. while you were posting

[abently]

Remember there's a pressure differential between the manifold and dump pipe so a larger dump pipe volume does increase the gas velocity.

And EMP > IMP when the Wastegate opens to limit Boost, which is why Intake Boost control is beneficial along with the fact that Cylinder Pressures are reduced as a by product of less air going in to only go out the wastegate.

Buttt, that's a whole new subject anyway.

[oldcorollas]

i cannot see how a larger dump pipe volume, for a given turbine outlet, will increase velocity in the dump pipe?? the velocity in the larger dump pipe will be slower OR the pressure will be lower. the two things are related.. as is temperature.

but, on the face of it, a velocity differential, with faster gas in manifold and slower gas in dump, is bad news (because it means the gas is higher pressure than it could be).

although temperature, pressure and velocity are absolutely linked (by PV=nRT)
you need to think about them seperately when talking about differentials.
however in reality they are linked, and calcuation is difficult without many assumptions (which the guy got wrong in his thesis )

And EMP > IMP when the Wastegate opens to limit Boost, which is why Intake Boost control is beneficial along with the fact that Cylinder Pressures are reduced as a by product of less air going in to only go out the wastegate.

what do you mean?
cylinder pressure = torque = power?
EMP usually is higher than IMP. the wastegate opens to reduce mass flow though the turbine, to reduce the turbines speed below the compressor surge line, and to prevent overspeeding of the turbine and compressor unit?

the exhaust manifold pressure can be, and often is, always greater than intake manifold pressure, even when the wastegate is open.
in limited situations, ie limited operating range, it is possible to have the exhaust pressure lower than the intake pressure (this requires high turbine speed, and carefully selected turbine and compressor wheels), but for transient operation, it is not common (i am not even sure if it is possible, i haven't checked )

[actionDAN]

its all good mate, dont get worked up about it.
These forums are an awesome tool because you get to dicsuss so many options/ideas and generally get quality feedback on the matter. However, some times there are people who also post info which is bulls*&t and not proven.
Thats why there are a few 'moderators' (like oldcorollas, the real roadrunner, etc... who have been playing with cars for years and have a very good handle on whats right and wrong) as such who do like to ensure what is written as factual info is indeed based on real life testing/experience.
This needs to happen otherwise alot of newbies could come on and be lead down the garden path following someones info which is completely wrong. As already mentioned in this thread, show us some pics of your manifolds and results gained vs a control manifold. If your results prove a theory wrong, awesome, everyone gets to learn something new

oh i wasnt worked up. i posted that msg with a smile on my face. you gotta admit...this debate will never end. i used to post in threads like this one all the time when i was a little girl...woops i mean boy.

[JustenGT8]

ideal manifold (from the turbos point of view) =
small diameter to reduce expansion and maintain velocity, but not so small to introoduce too much wall friction or reduce total flow.
low heat capacity material for the manifold or ceramic insulating layer on the INSIDE to maintain higher temperature to the turbine
shorter length to reduce heat loss (but mostly negated by the use of proper materials/coatings), but long manifold is not really bad, and could be good from a pulse reflection point of view and aid in scavenging. long manifold can also help to maintain a more constant pressure at the turbine entry which increases efficiency..


but hey, thats just my musings.... based on many papers and the experience of good manifold builders

Yup agreed. Hence race cars where they have the room to use a long runner manifold that will maintain heat energy as it's always on boost and at the upper end of the thermal range will be used to milk every last hp possible. Not worth the effort for most and usually won't work anyways....better off with your 'ideal' version as described.

Speaking of ceramic coating,, when i have had it done they did do the inside as well. Competition Coatings in Syd, used by race teams so a coating that works rather than blings