Mercedes Power Unit Hardware & Software

[Jolle]

. . . . The pressure waves in the intake port / manifold does not occur due to the air column "slamming into the back of the valve"... the origins for that, that I can find are in Superflow's manual and repeated adnaseum by magazines. If the air slams into the back of the valve, you closed it too soon .

It originates at valve open due to the shock of the pressure differential, between the port and cylinder as the piston starts to descend and creates a depression. . . .

There is also the phenomenon of exhaust tuning (pulses are much stronger in the exhaust runners due to the high cylinder pressure at EVO). Race engine manifolds are tuned so that a strong negative pressure wave arrives at the exhaust valve just before it closes. This pulls the last bit of exhaust out of the cylinder at TDC and sends a negative wave out the intake valve (which is also open at TDC). This is the main driver of waves in the intake manifold.

Not just racing engines, but that’s a very well known design item. Lots of people were surprised when Mercedes showed up with a log exhaust for 2014.
Exhaust tuning is also the main reason why for performance V8’s, a flat plane is preferred over a (in the US more common) cross plane. BMW has a form of variable exhausts on their production superbike since 2010, with valves in the balance pipes.

[Tommy Cookers]

.... Lots of people were surprised when Mercedes showed up with a log exhaust for 2014. .....

what Mercedes 'showed up with' wasn't a log exhaust ....

you people don't know what a log exhaust is

afaik of course

[Jolle]

.... Lots of people were surprised when Mercedes showed up with a log exhaust for 2014. .....

what Mercedes 'showed up with' wasn't a log exhaust ....

you people don't know what a log exhaust is

afaik of course

Well, a thing that resembled a log exhaust then. At least not the usual tuned spaghetti system.

[henry]

.... Lots of people were surprised when Mercedes showed up with a log exhaust for 2014. .....

what Mercedes 'showed up with' wasn't a log exhaust ....

you people don't know what a log exhaust is

afaik of course

It would be Interesting, at least to me, if you explained the difference between a log exhaust and what Mercedes “showed up with”.

[Tommy Cookers]

It would be Interesting, at least to me, if you explained the difference between a log exhaust and what Mercedes “showed up with”.

a log exhaust looks like a log clamped along the length of the head
ie it is literally or in essence one straight common pipe clamped directly onto all the exhaust port faces
literally on the new 1950s/60s UK Ford Consul&Zephyr and in essence by cast equivalents on most 1920s-50s cars
(though the USA had more lavish cast manifolds quite early eg even on 1940s side valve ('flathead') engines)
unless valve timing is conservative a 4 cyl 'log' gives some blow down into the neighbouring freshly-scavenged cylinder
though often a 6 cyl had 2x 3cyl logs - the 240 deg separation preventing such adverse blowdown
(some more recent engines eg British with ports merged in the head needed scatter cams to avoid adverse blowdown)

at best we can see the log as a 'zero length' system ie any 'negative' pulse would arrive far too early

what Mercedes had (visible if stripped of insulating wadding) can be called an old-style race system
wherein the headers don't meet at a common point
this was still normal eg Ferrari in F1 as late as 1960 and until c.1988 at Indy etc
if only by accident of lengths etc the OSS surely has some (weaker but broader-band) tuned effect
and it can be more compact

[sosic2121]

Exhaust tuning is also the main reason why for performance V8’s, a flat plane is preferred over a (in the US more common) cross plane.

I thought main advantage is that flat plane crank is much lighter than cross plane.

[Jolle]

Exhaust tuning is also the main reason why for performance V8’s, a flat plane is preferred over a (in the US more common) cross plane.

I thought main advantage is that flat plane crank is much lighter than cross plane.

It’s almost all exhaust tuning and a bit of intake tuning. Weight doesn’t really come into play, a cross plane crank case would even have to be a bit heavier because of the vibrations the imbalance of a flat vs cross plane.

[Hoffman900]

. . . . The pressure waves in the intake port / manifold does not occur due to the air column "slamming into the back of the valve"... the origins for that, that I can find are in Superflow's manual and repeated adnaseum by magazines. If the air slams into the back of the valve, you closed it too soon .

It originates at valve open due to the shock of the pressure differential, between the port and cylinder as the piston starts to descend and creates a depression. . . .

There is also the phenomenon of exhaust tuning (pulses are much stronger in the exhaust runners due to the high cylinder pressure at EVO). Race engine manifolds are tuned so that a strong negative pressure wave arrives at the exhaust valve just before it closes. This pulls the last bit of exhaust out of the cylinder at TDC and sends a negative wave out the intake valve (which is also open at TDC). This is the main driver of waves in the intake manifold.

I didn’t forget that, but I didn’t want to write an essay, so I simplified and omitted that.

Re: crankshafts
For crankshafts, what Jolle said. The advantage is exhaust pulse and intake tuning (more of a thing in a shared plenum design). Traditional American V8’s would shake themselves apart if they had flat plane crankshafts. Pro Stock and other builders have tried and the vibrations are untenable. Ford and GM did, but they had to do A LOT of work to mitigate those vibrations and it’s honestly probably not really worth it. Those engines are also pretty small by American V8 displacement standards.

It was worth it for GM in the C8R program as a flat plane crankshaft pulls on the restrictor more evenly than a cross plane crankshaft, so they realized power there. Not sure if that matters either as the BOP rules aren’t set in stone and restrictor size can be changed up or down depending.

[Jolle]

. . . . The pressure waves in the intake port / manifold does not occur due to the air column "slamming into the back of the valve"... the origins for that, that I can find are in Superflow's manual and repeated adnaseum by magazines. If the air slams into the back of the valve, you closed it too soon .

It originates at valve open due to the shock of the pressure differential, between the port and cylinder as the piston starts to descend and creates a depression. . . .

There is also the phenomenon of exhaust tuning (pulses are much stronger in the exhaust runners due to the high cylinder pressure at EVO). Race engine manifolds are tuned so that a strong negative pressure wave arrives at the exhaust valve just before it closes. This pulls the last bit of exhaust out of the cylinder at TDC and sends a negative wave out the intake valve (which is also open at TDC). This is the main driver of waves in the intake manifold.

I didn’t forget that, but I didn’t want to write an essay, so I simplified and omitted that.

Re: crankshafts
For crankshafts, what Jolle said. The advantage is exhaust pulse and intake tuning (more of a thing in a shared plenum design). Traditional American V8’s would shake themselves apart if they had flat plane crankshafts. Pro Stock and other builders have tried and the vibrations are untenable. Ford and GM did, but they had to do A LOT of work to mitigate those vibrations and it’s honestly probably not really worth it. Those engines are also pretty small by American V8 displacement standards.

It was worth it for GM in the C8R program as a flat plane crankshaft pulls on the restrictor more evenly than a cross plane crankshaft, so they realized power there. Not sure if that matters either as the BOP rules aren’t set in stone and restrictor size can be changed up or down depending.

Also, in racing engines, proper flow of air and subsequent revs are the highest priority, much more then weight or size (and especially with NA engines). Even visible now at Alpine and Mercedes, where Honda-McLaren bit themselves a bit with going the other way.

[pursue_one's]

According to AMuS: The investigation launched by Red Bull against the Mercedes engine is ongoing. It should be completed by Monza. It concerns the intercooler, the plenum and the position of the sensors.

[BassVirolla]

Exhaust tuning is also the main reason why for performance V8’s, a flat plane is preferred over a (in the US more common) cross plane.

I thought main advantage is that flat plane crank is much lighter than cross plane.

It’s almost all exhaust tuning and a bit of intake tuning. Weight doesn’t really come into play, a cross plane crank case would even have to be a bit heavier because of the vibrations the imbalance of a flat vs cross plane.

In a cross plane, you have two consecutive power strokes in each bank, while in a flat plane the power strokes always alternate between banks, giving an even spacing of the exhaust pulsing.

Nevertheless, in a cross plane with four (or eight!) final exhaust pipes, you can do a decent impulse tuning job, even though tuned for a half or quarter the rpms. Obviously, not ideal for a racing NA engine.

We are going quite off topic in fact... Mods, feel free to delete if necessary.

[SiLo]

According to AMuS: The investigation launched by Red Bull against the Mercedes engine is ongoing. It should be completed by Monza. It concerns the intercooler, the plenum and the position of the sensors.

Hopefully nothing comes of it otherwise I can't see past Max and RB taking the title. WCC should be close though.

[subcritical71]

According to AMuS: The investigation launched by Red Bull against the Mercedes engine is ongoing. It should be completed by Monza. It concerns the intercooler, the plenum and the position of the sensors.

I'm interested in what the actual complaint may be(?). It seems from what I've read that it is because they may be going under the temperature limit. The sensor positions are designated by the FIA. The rules allow going under the 10C above ambient limit during a lap as long as the average is above. Its not a case of, for instance, a flexible wing which is designed to pass a compliance test while circumventing the no flexible bodywork rule (I wish I could remember another rule that didn't involve Red Bull as I don't want that to be the point - just the idea). There is no other rule pertaining to inlet air temps so teams should be free to do what they wish as long as the average is above. If the FIA wanted it to be more stringent they would have said at any time (instantaneous), or every sector, or mini-sector (average). Its interesting that the rules also exclude the first lap of the race from the temperature monitoring (I'm thinking Ferrari 'camera' cooler).

5.6.8 Engine plenum (as defined in line 4 of Appendix 2 to these regulations) air temperature must be more than ten degrees centigrade above ambient temperature. When assessing compliance, the temperature of the air will be the lap average recorded by an FIA approved and sealed sensor located in an FIA approved location situated in the engine plenum, during every lap of the qualifying practice session, Sprint Qualifying Session, and the race. The first lap of the race or Sprint Qualifying Session, laps carried out whilst the safety car is deployed, laps with a time at least 20% greater than the fastest lap of the session, pit in and out laps and any laps that are obvious anomalies (as judged by the technical delegate) will not be used to assess the average temperature. The ambient temperature will be that recorded by the FIA appointed weather service provider. This information will also be displayed on the timing monitors.

[JordanMugen]

Nevertheless, in a cross plane with four (or eight!) final exhaust pipes, you can do a decent impulse tuning job, even though tuned for a half or quarter the rpms. Obviously, not ideal for a racing NA engine.

We are going quite off topic in fact... Mods, feel free to delete if necessary.

It's very interesting. Why does Yamaha prefer a crossplane crankshaft for their Yamaha R1?

(...and I on think their Yamaha MotoGP bike too? Are Yamaha the only MotoGP team not using a V4 engine? How about Suzuki? Edit -- it seems Suzuki also uses an inline-four on their MotoGP but with a crossplane crankshaft and not the flatplane one like their road-going GSXR1000.)

[Big Tea]

Nevertheless, in a cross plane with four (or eight!) final exhaust pipes, you can do a decent impulse tuning job, even though tuned for a half or quarter the rpms. Obviously, not ideal for a racing NA engine.

We are going quite off topic in fact... Mods, feel free to delete if necessary.

It's very interesting. Why does Yamaha prefer a crossplane crankshaft for their Yamaha R1?

(...and I on think their Yamaha MotoGP bike too? Are Yamaha the only MotoGP team not using a V4 engine? How about Suzuki? Edit -- it seems Suzuki also uses an inline-four on their MotoGP but with a crossplane crankshaft and not the flatplane one like their road-going GSXR1000.)

A good vid on it here
(

Also 2 good links below vid