Log VS Tubular exhaust, which one is more efficient ?

[Richard]

Forgive my ignorance ..... It's often easier to design things the way they always have been designed even though the criteria that made the established design the preferred option are no longer valid. Bear in mind "optimal" also includes packaging considerations. This reminds me of Newey deciding that KERS was an optional item and RB still won a lot of races against cars with KERS.

Perhaps the question could be turned around, why did the other teams think the exhaust configuration that was optimal for NA engine was still optimal for the new engines? The answer should be "We investigated both options and the tubular design gives a marginal gain that outweighs the complexity." I suspect some people actually thought "We've always done it this way" .

Oh, and who's to say Merc have the right answer? Perhaps they got it wrong, or perhaps this is an area where the difference is negligible so packaging rules the decision?

[Pieoter]

http://www.full-race.com/articles/Bseri ... riteup.pdf

All this shows is that a well designed equal length manifold is better than a poorly designed log manifold.

From reading the paper it says that the log manifold spooled the turbo sooner but became a restriction. Well what about if you work on increasing the flow of the log manifold (Massive wastegate?)? It might be possible to design a log manifold that spools sooner but doesn't have the restriction.

[Frank_]

you get a nice burble with unequal length primaries tho

[gruntguru]

though MHPE could have some internal structure, eg a restrictor or other, to kill pulses
this can be done so the turbine operates on a higher mean (rather constant) exhaust pressure ie pressure turbine working
for a given turbine power this would give a smaller and otherwise more responsive turbine

A restrictor would be lunacy. A smaller turbine nozzle if you want to increase turbine power (along with mean exhasut pressure as an undesirable side effect).

[gruntguru]

Assuming identical boost and optimisation of all tuning parameters, the linked B series Honda dyno comparison is a very clear case of either:
- A large reduction in back pressure due to free flowing design and utilisation of blowdown energy (which the 4 cyl log manifold cannot do) or
- A small reduction in back pressure (due to the same factors) resulting in BP lower than boost.

Small changes in BP could not otherwise account for the large improvement shown.

[lsimon]

Probably a bad educated guess... will it be possible with current regulations to inject more fuel in one cylinder in detriment of the rest while maintaining the fuel flow limits?
If I am not completely wrong (which indeed is very plausible) the advantage of tubular exhaust is that their length can be adjusted to resonate at the right number of rpm to increase power, but in a log exhaust this is not possible since the effective length of the exhaust is different for each pair of cylinders. However, could it be possible to use more fuel on the cylinder with a better tuned exhaust at the current rpm of the engine to compensate at least partially for the disadvantages of the log exhaust? (while keeping its advantages, I mean)

[Richard]

Current discussion is here http://www.f1technical.net/forum/viewto ... =4&t=21149