[WEC] Toyota LMP1 Discussion

[dbagtbag]

Originally Posted by cokata

Why would you have to make a V6 4l engine with ~5000rpm redline oversquare, or am i missing something

Most likely the high chamber pressures of the diesels require a more robust connecting rod. The longer the stroke the longer the connecting rod needs to be and that makes beefing it up to take the force from the piston difficult without adding unwanted mass. As long as good combustion quality and aspiration can be ensured it benefits to run oversquare since you have higher rpm potential.

[chernaudi]

Also, more and more road diesel engines are going oversquare. Peugeot's 908 V12 was claimed to have a 84mm bore and a 82mm stroke.

It has to do with revs and possibly compression ratio.

[CyberMotor]

Originally Posted by chernaudi

...more road diesel engines are going oversquare.

It has to do with revs and possibly compression ratio.

How is over square related to flat plane?

[chernaudi]

Again, probably revs (namely acceleration of a rotating mass).

Audi's 4.2 liter V8 used in the RS 4, RS 5 and R8 has pistons that at 8000 RPM or so travel at near F1 speeds, but that's over a huge stroke length and half the RPM of a V10 or V8 F1 engine of the past 20 years of so (in specific 2004-06 when the Audi RS V8 was developed).

And even it had a crossplane crank. The issue with the flatplane crank isn't RPM itself, but speeding up/slowing down. Flatplane cranks don't have the counterweights like crossplane cranks have. Lighter crank equals faster spin up. Flatplane cranks, though, do have a disadvantage in terms of high RPM vibrations, usually above like 8000 RPM and it gets worse the higher the RPM without good crank balancing.

Over-square cylinder dimensions allow for more RPM due to a shorter stroke distance (less distance for the piston to travel). A flatplane crank in a V8 will allow (in theory) faster spin up/slow down times.

Of course, this does matter for Toyota, who have a flat crank V8. For the Audi and Peugeot V12s, and Audi V10 and V6 diesels, they have their own crank designs that have no major variations from that would be expected from such engines.

[dbagtbag]

Originally Posted by chernaudi

Again, probably revs (namely acceleration of a rotating mass).

Audi's 4.2 liter V8 used in the RS 4, RS 5 and R8 has pistons that at 8000 RPM or so travel at near F1 speeds, but that's over a huge stroke length and half the RPM of a V10 or V8 F1 engine of the past 20 years of so (in specific 2004-06 when the Audi RS V8 was developed).

And even it had a crossplane crank. The issue with the flatplane crank isn't RPM itself, but speeding up/slowing down. Flatplane cranks don't have the counterweights like crossplane cranks have. Lighter crank equals faster spin up. Flatplane cranks, though, do have a disadvantage in terms of high RPM vibrations, usually above like 8000 RPM and it gets worse the higher the RPM without good crank balancing.

Over-square cylinder dimensions allow for more RPM due to a shorter stroke distance (less distance for the piston to travel). A flatplane crank in a V8 will allow (in theory) faster spin up/slow down times.

Of course, this does matter for Toyota, who have a flat crank V8. For the Audi and Peugeot V12s, and Audi V10 and V6 diesels, they have their own crank designs that have no major variations from that would be expected from such engines.

And to make it easier to understand why an oversquare engine tends to yield higher power than an undersquare engine of the same displacement, you can think of the oversquare engine rotating faster than its undersquare counterpart.

This means more fuel and air is ingested in a given amount of time for the undersquare engine, leading to more power. Simplistic explanation but its true for the most part, all else being equal.

[CyberMotor]

Originally Posted by chernaudi

Over-square cylinder dimensions allow for more RPM due to a shorter stroke distance (less distance for the piston to travel). A flatplane crank in a V8 will allow (in theory) faster spin up/slow down times.

I think I am understanding you. I'll provide an example which I think exemplifies what you are saying...

I grew up in the late 60s during the times of the American 'Muscle Cars'. There was an explosion of cylinder dimensions. I mainly followed Chevy back then and we had 283, 327, 396, 409 and then 454 cubic inches. Bigger seemed to be better and the way of the future. Then one night, this little plain looking Camaro Z-28 with a 302 cubic inch engine came loping through our hangout. We laughed but for those that thought bigger was better, this little short stroke engine proved them wrong.

Is this similar to what you are saying with the mass and piston distance?

[dbagtbag]

Originally Posted by CyberMotor

I think I am understanding you. I'll provide an example which I think exemplifies what you are saying...

I grew up in the late 60s during the times of the American 'Muscle Cars'. There was an explosion of cylinder dimensions. I mainly followed Chevy back then and we had 283, 327, 396, 409 and then 454 cubic inches. Bigger seemed to be better and the way of the future. Then one night, this little plain looking Camaro Z-28 with a 302 cubic inch engine came loping through our hangout. We laughed but for those that thought bigger was better, this little short stroke engine proved them wrong.

Is this similar to what you are saying with the mass and piston distance?

Likely. The 1999 Mustang GT made 260hp from 4.6L. The same year the Honda S2000 was making 250hp from 2.0L. The Ford's square engine redlines at something like 5800. The S2000's over square engine redlines at 9000.

Extreme examples but I think the point is there.

When you rev high the limiting component is typically your connecting rod because the piston wants to rip it apart as it changes direction near the top of the cylinder. The shorter the stroke, the less intense the acceleration of the piston is near the top (and bottom) of the cylinder.

With that you can do two things if you were to use the same connecting rod. Rev it higher, or beef up the piston for a forced induction application

[knighty]

Originally Posted by cokata

Why would you have to make a V6 4l engine with ~5000rpm redline oversquare, or am i missing something

ooohh..... juicy engine talk.....I do engines........the main reason the likes of F1 in the normally aspirated V10 & V8 era went massively over square was to reduce friction in the piston to cylinder interface, with a big bore which I think was around 98mm, and a small stroke, I think around 30mm or so, the side load emitted from the con-rod was minimal, friction is reduced with load (not area) and the rpm shot up as a result......the same applies to modern high performance and race diesels, hence they are now slightly over square, but only by a few mm.

the low compression ratio diesels (circa 14:1) are now preferred also because of a significant efficiency increase whereby the engine is not fighting the gas loads on the compression phase, all road car disels are now going this route for this very reason.

Regarding flat plane cranks, for the past 10 years or so the NASCAR teams have been running very light-weight cross-plane cranks with heavy-metal tungsten inserts, that are comparable in weight to that of a flat plane crank, so recently the weight issue is not such a big deal, but certainly a light weight crankshaft makes a race engine very very snappy and responsive.......the main and primary reason that people use flat-plane crankshafts is to get the exhaust pulsing correctly and evenly for power.......the cross plane cranks have a burble, due to the un-even firing, and the flat plane cranks basically sound like 4 cylinder engines, because thats exactly what they are!

But again even the NASCAR boys have figured the exhaust pulsing problem out, whereby they now run tri-Y manifolds that are coupled in such a fashion that the exhaust pulses are equal.......honsetly if I was designing a V8 LMP1 engine I would seriously consider using a cross-plane crankshaft, as the reliability issues and virbarions from a flat plane crank shaft are nothing but a nightmare for the chassis and general reliability.......I suspect Toyota know this and have probably very very carefully designed their engine in order that this is not a problem with a crankshaft that has critical resonant frequencies well away from the operating region, or a viscous damper on the crank-nose, or twin counter-rotating balance shafts........time will tell

somewhat off topic now!......regarding the R18 engine, well what can I say, the Audi design team have designed an engine that is 50kg too heavy and its hugely compromised their KERS choice......aww bless........ and thats just hard cheese as far as i'm concerned, I hope they get humiliated at LeMans.....amen.

[dbagtbag]

Originally Posted by knighty

ooohh..... juicy engine talk.....I do engines........the main reason the likes of F1 in the normally aspirated V10 & V8 era went massively over square was to reduce friction in the piston to cylinder interface, with a big bore which I think was around 98mm, and a small stroke, I think around 30mm or so, the side load emitted from the con-rod was minimal, friction is reduced with load (not area) and the rpm shot up as a result......the same applies to modern high performance and race diesels, hence they are now slightly over square, but only by a few mm.

the low compression ratio diesels (circa 14:1) are now preferred also because of a significant efficiency increase whereby the engine is not fighting the gas loads on the compression phase, all road car disels are now going this route for this very reason.

Regarding flat plane cranks, for the past 10 years or so the NASCAR teams have been running very light-weight cross-plane cranks with heavy-metal tungsten inserts, that are comparable in weight to that of a flat plane crank, so recently the weight issue is not such a big deal, but certainly a light weight crankshaft makes a race engine very very snappy and responsive.......the main and primary reason that people use flat-plane crankshafts is to get the exhaust pulsing correctly and evenly for power.......the cross plane cranks have a burble, due to the un-even firing, and the flat plane cranks basically sound like 4 cylinder engines, because thats exactly what they are!

But again even the NASCAR boys have figured the exhaust pulsing problem out, whereby they now run tri-Y manifolds that are coupled in such a fashion that the exhaust pulses are equal.......honsetly if I was designing a V8 LMP1 engine I would seriously consider using a cross-plane crankshaft, as the reliability issues and virbarions from a flat plane crank shaft are nothing but a nightmare for the chassis and general reliability.......I suspect Toyota know this and have probably very very carefully designed their engine in order that this is not a problem with a crankshaft that has critical resonant frequencies well away from the operating region, or a viscous damper on the crank-nose, or twin counter-rotating balance shafts........time will tell

somewhat off topic now!......regarding the R18 engine, well what can I say, the Audi design team have designed an engine that is 50kg too heavy and its hugely compromised their KERS choice......aww bless........ and thats just hard cheese as far as i'm concerned, I hope they get humiliated at LeMans.....amen.

The sidewall friction is dependent on the connecting rod/stroke ratio too. So conceivably you could have low friction even with a very long stroke if you have a super long connecting rod =D

I really hope Toyota wins this year. I've been rooting for a second Japanese win and they have come close before!

[knighty]

but then the engine would be so tall the engines high centre of gravity would make any car handle like a boat!.......Toyota said their new LMP1 engine has a crank centre height something like 16mm lower than the customer version that they provide to Rebellion, so the short stroke engine theory also has a significant impact upon chassis dynamics and general handling

[cokata]

Originally Posted by knighty

ooohh..... juicy engine talk.....I do engines........the main reason the likes of F1 in the normally aspirated V10 & V8 era went massively over square was to reduce friction in the piston to cylinder interface, with a big bore which I think was around 98mm, and a small stroke, I think around 30mm or so, the side load emitted from the con-rod was minimal, friction is reduced with load (not area) and the rpm shot up as a result......the same applies to modern high performance and race diesels, hence they are now slightly over square, but only by a few mm.

I am pretty sure that all high revving engines are oversquare because the bottleneck is piston speed, and because you can fit bigger valves, and at high rpm that makes a big diffrence

[TF110]

I found it interesting Kinoshita San said if they were to do a brand new engine, it would be 4.0L V8. I hope this is realized and they decide to go this route in the near future. Also interesting is that the electric power is limited by the supercap and its size/weight. They have definitely made gains from it to push out over 480hp while keeping the same size. Toyota also have a few new tricks that aren't currently applied to their car.

One is this- http://newsroom.toyota.co.jp/en/detail/2656842/ a silicon carbide power semiconductor. Reducing power loss from regenerative braking and electric power sent to the electric motor. This could add 5% to fuel economy on road cars and it reduces the PCU size by 80%. Theres definitely plenty to come from Toyota if they choose to do so.

[GasperG]

I doubt that supercap is limiting factor, he said input/output to supercap, he could have meant the inverter (PCU).

Current PCU adds weight, silicon carbide could shave off some of that weight and also improve charge/discharge efficiency. The question is if this technology is mature enough to be used, it very well could be because the article states testing on a public roads within a year. Maybe they already have it?

[dbagtbag]

Originally Posted by cokata

I am pretty sure that all high revving engines are oversquare because the bottleneck is piston speed, and because you can fit bigger valves, and at high rpm that makes a big diffrence

The bottle neck is piston acceleration not piston speed. High piston speed is not necessarily bad, but is often so because it typically entails high piston acceleration.

What he said is correct, shorter strokes tend to lead to lower piston friction. First off when running at the same engine speed the piston speed is lower if the stroke is short. Secondly, if the connecting rod is a similar length to that of a longer stroke engine, the max connecting rod angle is smaller. This means the component of the force transmitted through the connecting rod that is pressing the piston into the cylinder wall is smaller.

Power used to overcome friction = friction coeff * force pushing piston into cylinder wall * piston speed

These two things lead to lower friction in a shorter stroke engine.

[knighty]

Originally Posted by cokata

I am pretty sure that all high revving engines are oversquare because the bottleneck is piston speed, and because you can fit bigger valves, and at high rpm that makes a big diffrence

I would also agree with that, but as above its acelleration and therefore low mass, not speed.....really there are many reasons......all of them totally un-related to road car technology for the mass market!

[CyberMotor]

I must say you folks are pretty darn smart and probably more than a handful of you are geniuses. This type of discussion is why I love prototypes and why people like you will solve big problems and make cars more efficient while still being powerful, responsive and extremely entertaining to watch and drive.

Good talk. A big tip of the hat to you for conducting such informative discussions in a civil manner. That's greatly missed on this side of the pond.

[dbagtbag]

It might be time to get this thread back on topic lol =p

[CyberMotor]

Originally Posted by TF110

I found it interesting Kinoshita San said if they were to do a brand new engine, it would be 4.0L V8.

The V-12 in the Ferrari 333 SP was just below 4.0L. It was a short stroke engine but had a lot of cylinders making wonderful sounds.

I think of a V-12 as long and low. It had 12 cylinders but they were wide and had a short stroke but could reach high RPMs in a moment.

Was it over or under square?

I am honored to have heard this engine in its unbridled state running at Road Atlanta just after they were taking some of them out of the crates and putting them together for the first time. That experience is what got me to here.

The BOP then was to reduce the revs to equalize the 333 with the other engines. How do you reduce revs on this engine with the electronics available at that time?

[deltawing]

Originally Posted by CyberMotor

.....Was it over or under square?...

Bore = Stroke - you have Square.

Bore bigger than stroke - Oversquare.

Bore smaller than stroke - Undersquare.

.

[TF110]

Originally Posted by GasperG

I doubt that supercap is limiting factor, he said input/output to supercap, he could have meant the inverter (PCU).

Current PCU adds weight, silicon carbide could shave off some of that weight and also improve charge/discharge efficiency. The question is if this technology is mature enough to be used, it very well could be because the article states testing on a public roads within a year. Maybe they already have it?

He said that the weight of the capacitor is the limiting factor in 6mj vs. 8mj. But if they arent using the silicon carbide in the pcu, perhaps that could allow them to save enough weight on the inverter that itd offset a heavier capacitor. If not the updated pcu being able to cut power losses enough with the current capacitor dimensions? Now looking back, I think this may be a reason why Toyota didn't want to drop much off that much weight for the new cars.

[gwyllion]

I agree. With the heavy supercapacitor Toyota has probably gained the most with the weight increase compared to the initial draft: 870 kg instead of 850 kg minimum weight.

[TF110]

I think they will make gains with tech like this silicon carbide pcu. It may help them to step up to 8mj. Obviously thats an objective on Kinoshita's list judging by him saying its a shame they couldnt go there. I would say that another area they can improve on is the capacitor. If they choose to go down the battery route they already have some good tech going on with the solid-state batteries and lithium air http://www.autonews.com/article/2014...teries-for-20s. Hopefully theyre still racing in the hybrid lmp1 class and we can look forward to these technologies. If not maybe Super GT will open up to this or WRC allows hybrids.

[Japanese Samurai]

According to Toyota WEC website,TS040 engine weight is 105kg.
http://ms.toyota.co.jp/jp/wec/specia...vation-04.html

[GasperG]

Toyota showed first prototype of solid state battery in 2010, those things can go really slow or even never see a production. And from the article 2 kW/liter rated power would take a 176 l of volume only for the cells and it would have a capacity of 70 kWh, a total no-go.

They could improve supercap, since there are many different types with different energy and power rating, but I think we will never see the batteries that can take >350 kW and have only ~1 kWh of storage. Maybe some hybrid Li-Ion capacitors.

Porsche example is on the edge of battery use, but they only charge and discharge it with 180 kW because only ERS-K needs storage. ERS-H energy is probably directly routed to the electric motor and even if it's not, both ERS-H and ERS-K can not generate at the same time. Toyota would need twice the power rating of Porsche storage or twice the size.

[dbagtbag]

Originally Posted by GasperG

Toyota showed first prototype of solid state battery in 2010, those things can go really slow or even never see a production. And from the article 2 kW/liter rated power would take a 176 l of volume only for the cells and it would have a capacity of 70 kWh, a total no-go.

They could improve supercap, since there are many different types with different energy and power rating, but I think we will never see the batteries that can take >350 kW and have only ~1 kWh of storage. Maybe some hybrid Li-Ion capacitors.

Porsche example is on the edge of battery use, but they only charge and discharge it with 180 kW because only ERS-K needs storage. ERS-H energy is probably directly routed to the electric motor and even if it's not, both ERS-H and ERS-K can not generate at the same time. Toyota would need twice the power rating of Porsche storage or twice the size.

Yeah you're right when I first heard Porsche were using batteries I struggled to understand their reasoning. It seems to work so thats awesome but batteries are definitely more suited to the everyday car for the public.

A race car needs high charge/discharge rates since its most effective to use the hybrid power early in the acceleration out of a corner rather than stretch its use out longer.

But then again Porsche is only powering the front motors so who knows a battery might be completely fine for them.

both ERS-H and ERS-K can not generate at the same time.

Not if you stomp on the brakes full throttle =D