Mercedes Power Unit Hardware & Software

[Tommy Cookers]

the window of benefit of hotter charge ex-compressor/charge cooling ?
(if giving a higher temperature during ignition) is burning a leaner mixture than otherwise possible

though presumably raising fuel temperature without raised charge temperature can make the same claim
with fewer disbenefits

[ringo]

Would be funny if the engine was a 3 valve engine, with the freed up room in the cylinder head going to a central direct injection system.
Mercedes have been doing 3 valve engines for some time, would they be bold enough to use it in a race engine?

[63l8qrrfy6]

Would be funny if the engine was a 3 valve engine, with the freed up room in the cylinder head going to a central direct injection system.
Mercedes have been doing 3 valve engines for some time, would they be bold enough to use it in a race engine?

They have exhaust side injectors, you can see the fuel rail under the exhaust manifold in some of the pictures.

[roon]

Would be funny if the engine was a 3 valve engine, with the freed up room in the cylinder head going to a central direct injection system.
Mercedes have been doing 3 valve engines for some time, would they be bold enough to use it in a race engine?

5.1.8 Engines must have two inlet and two exhaust valves per cylinder.
Only reciprocating poppet valves with axial displacement are permitted.
The sealing interface between the moving valve component and the stationary engine
component must be circular.

Interesting to note that injector and combustion chamber design is almost unregulated. One could imagine a mechanical, cam-driven component having an interplay with the supposed pre-chamber systems. Such a 'fifth-valve' would still constitute a component of the fuel injector.

It could open and close the pre-chamber. This would provide discrete volumes for fuel injection moments without modifying the the solenoid driven components of the fuel injector.

For example:

1. three injector puffs during the first part of the intake stroke while the prechamber valve is open.
2. prechamber valve closes during mid/latter part of the intake stroke, and two more injector puffs while the prechamber is closed
   
   leading to...
3. spark ignition within the prechamber
4. prechamber valve forced open releasing flame front into the homogenously mixed main combustion chamber at/near TDC.
   
   ...or the prechamber valve could simply reopen again just prior to ignition.

There is a limited number of injection events permitted per stroke. I'm not sure what that number is--I believe less than ten.

Its small size and inertia could allow unusual cam lobe profiles. Downside to what I proposed is exposure of the prechamber valve guide to combustion.

But all this is byzantine and dubiously useful. There could be other ways to achieve a variable geometry prechamber toward benefit, without violating the rules of what constitutes a fuel injector, intake & exhaust valves, and maintaining a fixed combustion chamber volume (although, swept volume is how engine displacement is defined in the regs, so even a variable volume combustion chamber should still be legal).

A while back I proposed to have a pin/plug/dowel that could impose or recede within the combustion chamber to alter final compression ratios and help control knock. Depending on its position, it could alter compression/decompression slopes independent of piston travel. Compression ignition could be turned on/off, if they're right on the limit of such modes. Supplemental to spark and TJI: insertion of a sufficiently voluminous body into the combustion chamber could be another method of initiating combustion via increasing the compression-ratio at the right moment. Or maybe there would simply be benefit to being able to slight alter CR at will.

[roon]

Would be funny if the engine was a 3 valve engine, with the freed up room in the cylinder head going to a central direct injection system.
Mercedes have been doing 3 valve engines for some time, would they be bold enough to use it in a race engine?

They have exhaust side injectors, you can see the fuel rail under the exhaust manifold in some of the pictures.

Can you post them?

[63l8qrrfy6]

Would be funny if the engine was a 3 valve engine, with the freed up room in the cylinder head going to a central direct injection system.
Mercedes have been doing 3 valve engines for some time, would they be bold enough to use it in a race engine?

They have exhaust side injectors, you can see the fuel rail under the exhaust manifold in some of the pictures.

Can you post them?

https://www.youtube.com/watch?v=rGDJqTDXgtg

0:03

[roon]

They have exhaust side injectors, you can see the fuel rail under the exhaust manifold in some of the pictures.

Can you post them?

https://www.youtube.com/watch?v=rGDJqTDXgtg

0:03

Thanks. Image cap:



Any chance that those are oil and not fuel?

[63l8qrrfy6]

No - you can follow the outlet from the fuel pump into that central gallery which presumably splits the flow between the 2 banks and then coming down into the rail.

[roon]

Seems likely, at 1:53 there are junctions pointing down off the fuel rail. The entry angle and location of the injector between the exhaust ports--would this preclude TJI and prechambers on this PU? The spark plugs seemingly still in their usual central location, distanced one cylinder-radius away (~40mm).

[PlatinumZealot]

If the injector assembly is angled to one side it doesn't matter i guess. The spark plug bit is very likely going down the axis of the cylinder which is sorta normal. Bummer that it still doesn't reveal much.

[63l8qrrfy6]

Correct, it's the angle of the spray holes that matter, not the angle of the injector itself.

I'm sure there is s better picture though, this was just the first one I could find.

[gruntguru]

There is still a great advantage from running cooler air into th engine. More oxygen and easier compression. No reason to run hot air when you have direct injection. Besides, the better your intercooler is, the smaller you can make it. The teams always struggle with cooling on the edge to get the best aerodynamics.

They can just run more boost if they need more oxygen. Easier compression sure - but less pressure through the power stroke offsets that.

the window of benefit of hotter charge ex-compressor/charge cooling ?
(if giving a higher temperature during ignition) is burning a leaner mixture than otherwise possible though presumably raising fuel temperature without raised charge temperature can make the same claim with fewer disbenefits.

The benefit is higher thermodynamic cycle efficiency. Adding heat (burning fuel) at higher working fluid temperature raises the cycle efficiency.

The downsides are thermal stress limits of combustion chamber materials and possibly detonation.

[wuzak]

There is still a great advantage from running cooler air into th engine. More oxygen and easier compression. No reason to run hot air when you have direct injection. Besides, the better your intercooler is, the smaller you can make it. The teams always struggle with cooling on the edge to get the best aerodynamics.

They can just run more boost if they need more oxygen. Easier compression sure - but less pressure through the power stroke offsets that.

the window of benefit of hotter charge ex-compressor/charge cooling ?
(if giving a higher temperature during ignition) is burning a leaner mixture than otherwise possible though presumably raising fuel temperature without raised charge temperature can make the same claim with fewer disbenefits.

The benefit is higher thermodynamic cycle efficiency. Adding heat (burning fuel) at higher working fluid temperature raises the cycle efficiency.

The downsides are thermal stress limits of combustion chamber materials and possibly detonation.

Aren't the two main reasons that cooling the compressed air works in piston engines to get more power is that detonation is avoided, or reduced, and more fuel can be used.

But it doesn't mean that the engine is running more efficiently.

And when there is a fuel flow limit you can't add any more fuel, so making the charge air denser doesn't increase power.

[ringo]

Can you post them?

https://www.youtube.com/watch?v=rGDJqTDXgtg

0:03

Thanks. Image cap:

https://i.imgur.com/axoymYK.jpg

Any chance that those are oil and not fuel?

Ok i See,
Somewhat explains why the camshaft spacing is so close.
Fuel injection from the side. Though.. this doesn't really reveal where the injector is located in the cylinders.
Is it still possible that fuel is still injected in the centre?
Is there enough meat in the cylinder head between the valves for routing to the centre chamber, or is it plainly in the at the side as illustrated in the honda engine article?

[hurril]

https://www.youtube.com/watch?v=rGDJqTDXgtg

0:03

Thanks. Image cap:

https://i.imgur.com/axoymYK.jpg

Any chance that those are oil and not fuel?

Ok i See,
Somewhat explains why the camshaft spacing is so close.
Fuel injection from the side. Though.. this doesn't really reveal where the injector is located in the cylinders.
Is it still possible that fuel is still injected in the centre?
Is there enough meat in the cylinder head between the valves for routing to the centre chamber, or is it plainly in the at the side as illustrated in the honda engine article?

Do we think that they've done this from the start? Has any of you eagle-eyed folks seen the fuel lines on the older engines?