2021 Engine thread

[J.A.W.]

On the subject of V-configuration engines with split angle big-end crank pins..

Honda has racing experience with their RS 750 twin, which did in fact beat the legendary H-D XR 750
for the No 1 plate in AMA flat-track racing...
...but when the same engine was tried in road racing..
. the crankshaft repeatedly failed, when asked hack the more extreme forces required...

[godlameroso]

AFAIK, it is the MGU-H that will be removed, while the MGU-K is here to stay.

Yes i mean MGU-H gone and replaced by two conventional turbo's and even smaller, they will lag if 4 bar is the working boost level.

Not sure about that.

If they allow variable geometry turbos, or anti-lag, or the manufacturers use a sequential system lag may be minimal.

The current configuration turbos are way ovesized in both the compressor and, especially the turbine.

I wondered if they could also use a single turbine/twin compressor concept, with the compressors mounted on the same shaft back to back. I believe such a solution was proposed in the V6 engine thread.

Why not turbo + supercharged engines? That's almost road relevant as Audi is getting ready to introduce E-charger + conventional turbo engines, Volvo's new S60 has something along those lines.

[Tommy Cookers]

[quote=J.A.W.]On the subject of V-configuration engines with split angle big-end crank pins..
Honda has racing experience with their RS 750 twin, which did in fact beat the legendary H-D XR 750
for the No 1 plate in AMA flat-track racing...
...but when the same engine was tried in road racing..the crankshaft repeatedly failed, when asked hack the more extreme forces required...[/quote]

surely not what we mean by split ?
the above and the many other similar engines are not 'split crankpin' as we mean here (you'd not get even firing on a V twin)
pins seperation by eg 76 deg (for a 52 deg V) was for balance, made firing less even, and anyway needed 2 throws axially seperated by a full web
ie constructed as what in a V6 we could only call a 6 throw crank (as 65 deg Ferrari Dinos and 60 deg V6s had) making a bulkier engine
eg https://www.manualslib.com/manual/83009 ... l?page=339
and better https://books.google.co.uk/books?id=MvO ... et&f=false

262 in 'split pin' fully even firing 90 deg V6 engines have been made by GM since 1985 and seem to be still produced for vans etc
crankpin dia increase to 2.25" allowed this 30 deg offset (previously the common 2.1" pin allowed only 18 deg offset and 132/108 intervals)
http://www.perfectengine.com/Chevrolet_ ... 262dcs.htm
(select the 2nd picture and enlarge it)

crankshaft design can be dictated by the engine rules fixing certain dimensions
eg pin overlap available in the current engines should be simple to check as the dimensions are in the rulebook

[J.A.W.]

On the subject of V-configuration engines with split angle big-end crank pins..
Honda has racing experience with their RS 750 twin, which did in fact beat the legendary H-D XR 750
for the No 1 plate in AMA flat-track racing...
...but when the same engine was tried in road racing..the crankshaft repeatedly failed, when asked hack the more extreme forces required...

surely not what we mean by split ?
the above and the many other similar engines are not 'split crankpin' as we mean here (that would never give even firing to a V twin)
to get pins seperated by the necessary eg 90 deg (for a 45 deg V) they had 2 throws axially seperated by a full web
ie constructed as what in a V6 we could only call a 6 throw crank (as 65 deg Ferrari Dinos and 60 deg V6s had) making a bulkier engine
eg https://www.manualslib.com/manual/83009 ... l?page=339

at one time a 'split pin' fully even firing 90 deg V6 design was made by GM
but now everything like this has some thin web between pins
crankshaft design can be dictated by the engine rules fixing certain dimensions
eg pin overlap available in the current engines should be simple to check as the dimensions are in the rulebook

Well, T-C, notwithstanding F1 regs, & how Subaru attempted a 'boxer' 12 - with 12 discreet big-end pins..
..this is how Kevin Cameron put the Honda RS 750 crankshaft issue..

"...when the RS 750 dirt -tracker engine of the 1980s was run in Commonwealth Racing's
twins roadracer, its crankshaft had to be changed every 150 miles to prevent breakage of its
vibration quelling staggered crankpins...
Why did the RS crank succeeed in flat track & fail in 200 miles on pavement? "

Any guesses?

[godlameroso]

NVH?

[63l8qrrfy6]

If they would allow rpm up to 18000 completely new engines has to be made.
This is due to the 53mm stroke and 80 mm bore
You just cannot rev more than 15000 rpm with that long stoke due to piston speed.

how did you work that out ?

simple comparison with the rpm and stroke of the frozen NA engines shows that .....
the square root of the ratio of the 53 mm stroke to the NA stroke c.39 mm is 1.16
so the 53 stroke engine rpm should be 1.16x lower ie 86% of the NA rpm (for engine life as currently demanded)
for the same acceleration of the reciprocating parts and so about the same stresses
also current pistons are apparently steel or partly steel so relatively heavier

toraabe is spot on

What is to say that the NA engines were limited by piston accelerations ?

A steel piston will be about the same weight as an Al piston because:
1. It has 3 times the density but 3 times the stiffness.
2. Typical Al pistons have an endurance strength of just under 50 MPa at operating temperature. Steel pistons can have up to 4 times that but they will run hotter as the thermal conductivity is 2-3 times lower (crown thickness is smaller so that almost makes up for the conductivity deficit).

Assuming 300 bar PCP, 80 mm bore, 0.5 kg reciprocating mass, 53 mm stroke, 132.5 mm rod length (2.5 rod/stroke ratio) it works out that inertial loads are about half the gas loads at 15000 rpm (150 kN vs 78 kN) - so you can run up to 21000 rpm until the inertial loads equal the gas loads. I concede that piston pin bores are weaker under inertial loads at TDC than they are under gas loads but surely they can be made to work.

This is the second time I'm posting as I've messed up the maths the first time - please do check !

[Tommy Cookers]

you seem to be saying that those NA F1 people were wrong in their piston material ?

and the mass-specific stiffness of steel being equal to that of Al alloy is not a dog in this fight
the piston being substantially loaded in bending, alloy wins as if 3x the thickness has greater strength for the same weight etc
or less weight for the same strength
the reason why planes are alloy not steel

ok the temperature is the crucial factor here (as with some planes or parts thereof)
but it's hard to believe a steel piston is better rpm wise than would an alloy piston be even within its safe working temperature

[wuzak]

Aluminium and steel have similar strength to weight ratios, but I believe that geometry is what, in part, determines the stiffness of a part.

That is the advantage of aluminium - for the same weight you can use more material and achieve better stiffness.

[63l8qrrfy6]

you seem to be saying that those NA F1 people were wrong in their piston material ?

and the mass-specific stiffness of steel being equal to that of Al alloy is not a dog in this fight
the piston being substantially loaded in bending, alloy wins as if 3x the thickness has greater strength for the same weight etc
or less weight for the same strength
the reason why planes are alloy not steel

ok the temperature is the crucial factor here (as with some planes or parts thereof)
but it's hard to believe a steel piston is better rpm wise than would an alloy piston be even within its safe working temperature

While 3x thickness gives you lower stresses, the endurance strength is still lower - by about 4 times (at 10 million cycles, after than Al keeps dropping even further behind). Overall the factor of safety will favor steel pistons if only by a small margin.

Endurance strength is a material property, it is not geometry dependent.

And I disagree that specific stiffness is not important.
Stiffness drives the skirt-liner contact which in turn influences the friction characteristics. Keep in mind that the liner-skirt is a complex elasto-hydrodynamic joint.
Another example is the piston pin bore - which in highly loaded pistons has complex radial and axial profiles to avoid edge loading. The disadvantage of profiling pin bores is that contact stresses/ bearing specific pressures are increased due to the reduction in area. However, as stiffness increases the amount of profiling can be reduced.

All in all I have not claimed that a steel piston is structurally better. I claim that it can match the same durability for the same weight as an aluminium piston.

It's biggest advantage is that the top land height can be reduced, shifting the pin bore up, effectively increasing the rod length. As the top land height reduces, so does the crevice volume which helps combustion. Ring groove wear is significantly better too. Other claims are that a hotter piston also helps combustion and that the reduced heat transfer improves TE - I have not seen concrete evidence of these.

[Sasha]

2.0L V6 ,Twin Turbo,KERS both Axle(output only rear axle),15,000 rpm redline,no fuel flow or max fuel allowed
No HERS

[wuzak]

2.0L V6 ,Twin Turbo,KERS both Axle(output only rear axle),15,000 rpm redline,no fuel flow or max fuel allowed
No HERS

Going to have a boost limit with that?

[Selvariabell]

2.0L V6 ,Twin Turbo,KERS both Axle(output only rear axle),15,000 rpm redline,no fuel flow or max fuel allowed
No HERS

Looks good. I prefer if they add a change to the degree of the V configuration, preferably either 60° or 125°.

[Sasha]

2.0L V6 ,Twin Turbo,KERS both Axle(output only rear axle),15,000 rpm redline,no fuel flow or max fuel allowed
No HERS

Going to have a boost limit with that?

Most likely.

[Sasha]

2.0L V6 ,Twin Turbo,KERS both Axle(output only rear axle),15,000 rpm redline,no fuel flow or max fuel allowed
No HERS

Qual 1200hp, Race 1000hp

So late 80's engine sound and power(more down low torque) but with heavier cars.

[Selvariabell]

2.0L V6 ,Twin Turbo,KERS both Axle(output only rear axle),15,000 rpm redline,no fuel flow or max fuel allowed
No HERS

Qual 1200hp, Race 1000hp

So late 80's engine sound and power(more down low torque) but with heavier cars.

Why the larger displacement? They could have a V8 with that.