Log VS Tubular exhaust, which one is more efficient ?

[FW17]

Any reason why there is a sudden jump in the tuned exhaust and not in the log?

[wuzak]

http://i1267.photobucket.com/albums/jj5 ... 19548a.jpg

Any reason why there is a sudden jump in the tuned exhaust and not in the log?

guess that's where the tuned exhaust is tuned for.

[marcush.]

no question the combustion engine is limited mainly by the maximum fuel flow so in the complete car context all is hinting in the direction you might not even be interested to get that extra filling potential a tuned exhaust system might be able to offer.

so in the context of complete package efficiency it is the better packaging allowing cleaner aero that beats all out commbustion engine power -especially when you can make massive use of the electric motors in terms of torque fill .

Could it be there is always more power available than needed and you are restricted either by grip available or fuel flow limits?

[emaren]

t is not all about peak power.

I posted this in the V10 firing order thread

https://www.gtisoft.com/upload/Renault-FiringOrder.pdf

As you can see, peak power did not equate to lowest lap time.

I had a lot of experience back in the previous Turbo era, on the electronics side, not the exhaust manifold side, but I know that back then, many different approaches were taken, from sticking the turbo's as far away as possible to hugger style manifolds. Because I was not close enough to that side of the development process, I cannot remember any details, except that many things that worked seemed to be counter-intuitive and that packing for aero reasons was limited to Brabhams low-line cars which looked and sounded awesome, but........

[Tommy Cookers]

........ no question the combustion engine is limited mainly by the maximum fuel flow so in the complete car context all is hinting in the direction you might not even be interested to get that extra filling potential a tuned exhaust system might be able to offer. .......

here the argument for so-called tuned exhaust is that the same filling is done for less cost in supercharger power (and intercooling)
so allowing increased recovered power or crankshaft power

anyway the log exhaust is somewhat tuned ......
ie the system overall length is still broadly optimised for so-called 'negative' pulses to arrive around tdc
though the slight difference in path lengths back to the different cylinders causes phase dispersion

[marcush.]

Well we haven´t seen the "log manifold" naked and even if it looks like a 3-2- 1 configuration the primariies could still merge in one place so the difference only the length of the primary tubes.
I think the penalty for a real smooth "log"appearance manifold is not big compared to an elaborate 3 into 1

[hecti]

http://i1267.photobucket.com/albums/jj5 ... 19548a.jpg

Any reason why there is a sudden jump in the tuned exhaust and not in the log?

I'm curious if this dyno graph is from a turbocharged engine or a naturally aspirated. I have a feeling that you could be comparing apples to bananas

[gruntguru]

relative to a given induction pressure this raised exhaust pressure has cost crankshaft power
what matters is whether or not this factor is dominant (over the benefits of raising mean exhaust pressure)
presumably Renault and Ferrari think it is and maybe Mercedes thinks it is not

since raising exhaust pressure and raising massflow ie leaning are somewhat antagonistic ie tending to be mutually exclusive
one wonders which is being used when rpm is significantly over 10500

There is no nett "benefit" in raising mean exhaust pressure. A small reduction in the duration of choked conditions at the exhasut valve will be offset by reduced flow during the remainder of blowdown and increased exhaust stroke pumping work. F1 engine designers are aiming for the lowest mean exhaust pressure consistent with their turbine power goal. In any case the mean exhaust pressure needs to be lower than intake pressure (for reasons mentioned elsewhere) and intake pressure will be chosen based on AFR and (yes circular logic) turbomachinery power targets.

[gruntguru]

http://i1267.photobucket.com/albums/jj5 ... 19548a.jpg

Any reason why there is a sudden jump in the tuned exhaust and not in the log?

I'm curious if this dyno graph is from a turbocharged engine or a naturally aspirated. I have a feeling that you could be comparing apples to bananas

From the shape almost certainly "non turbo".

[J.A.W.]

Does that dyno chart comparison purport to show the exhaust system as the sole parameter change?

Or is the tilt in power delivery shown - actually related to other significant breathing changes ( such as cams) too?

[FW17]

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

[xpensive]

Snap out of it guys, until the MHPE PU, conventional wisdom for a turbo was to carry every xhaust pulse individually to the turbine.

Like this;



So what happened that made MHPE revert to a Jurassic park design, think about it?

[J.A.W.]

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

Thanks for that W-F1, that reminds me of when I earned a quid assisting in a family business 'uncorking'
Nippon grey-import turbo-cars.. ..exhaust/intake/injectors/chip.. ..to let 'em breathe & run proper sporty..

[Tommy Cookers]

.... Snap out of it guys, until the MHPE PU, conventional wisdom for a turbo was to carry every xhaust pulse individually to the turbine. So what happened that made MHPE revert to a Jurassic park design, think about it?

their log exhaust, like most such made in the last 50 years, appears to carry the pulses to the turbine rather well
this is in principle unrelated to the benefits of using reflected pulses (though the log exhaust can do this anyway)

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

imo MHPE have kept the pulses, but somewhat raised the mean exhaust pressure (by increasing the mgu-h load on the turbine)
as pulses alone (pure blowdown working) will not use the full scope of the F1 rules
not even if the cylinder CR is lowered to increase blowdown turbine power

[xpensive]

Yada, yada, yada, in that case, what was ever the purpose of the complicated and space-consuming tubular xhaust?

Snap out of it, something has obviously happened here, MHPE has picked up a solution we haven't seen for 30 years?