2025/2026 Hybrid Powerunit speculation

[Tommy Cookers]

so maybe it's not so Miller cycle ?

[venkyhere]

Will we be seeing silicon carbide batteries in F1 power pack?

It is sad F1 has restricted battery packs to placed within the monocoque, could have been better if they were left free to teams.

https://www.youtube.com/watch?v=cwJpkfWWcsc&t=38s

Thing about the F1 batteries is that they're charged/discharged more times in a race weekend that most cell phones would be in a year. Not sure that thing is up to snuff.

Placing them in the monocoque is certainly for the protection of the batteries in an accident. We don't want a fire.

But we also want batteries that dont catch fire. Teams should be allowed to choose chemistry that are safe, does not need protective cases and can be placed anywhere or unsafe chemistry that is confined to a protective case within the monocoque.

Even for arguments sake, lets say this is allowed. Where do you think a team is going to place the battery (which stores enough energy to generate 500bhp worth for X seconds duration) ? Atleast we can assume that it's going to be bigger than the 2025 battery that generated 200bhp worth for Y seconds in a much bigger car, can't we ? Now what ?

[johnny vee]

For the new power units that are coming, the regulations dictate that the compression ratio in a cylinder can be no higher than 16:0.

This is a drop from the 18:0 level that was a part of the previous ruleset.

With teams well aware of gains that can be had if they can increase the compression ratio, it is suggested that some clever designs are being used to achieve this higher limit – and still stay within the rules.

This is being achieved because, under the wording of the regulations, the compression ratio is only measured when the engine is not at full running temperature out on track.

It is suggested that complex parts are being used in the engines that deliberately expand when the engine is running hot – helping push the piston closer to the top of the cylinder during its cycle than when it is cold.

[johnny vee]

From technical regulations p.61

C5.1 Engine specification
C5.1.1 Only 4-stroke engines with reciprocating pistons are permitted.
C5.1.2 Engine cubic capacity must be 1600cc (+0/−10cc).
C5.1.3 All engines must have six cylinders arranged in a 90° “V” configuration and the normal section of
each cylinder must be circular.
All six cylinders must be of equal capacity.

They do not specify a bore or stroke, just engine capacity.
I'm just trying to think how the alleged teams (Merc, Redbull) would increase compression. Expanding piston, but not in width just height? Is that possible?

[johnny vee]

Not my maths, asked AI
If we work with a hypothetical bore 80mm and stroke 53mm, how much would the top of the piston have to be closer at TDC to increase compression ration from 16:1 to 18:1 and it spat out an answer if 7.07mm which I think is impossible. Also, the ai maths could be wrong.

Step 1: Determine the initial swept volume and clearance volume The initial swept volume (\(V_{d1}\)) is calculated using the bore (\(b=80\text{\ mm}\)) and initial stroke (\(s_{1}=53\text{\ mm}\)):\(V_{d1}=\frac{\pi \cdot b^{2}\cdot s_{1}}{4}=\frac{\pi \cdot (80\text{\ mm})^{2}\cdot (53\text{\ mm})}{4}\approx 266495.55\text{\ mm}^{3}\)The compression ratio (\(CR\)) formula is \(CR=\frac{V_{d}+V_{c}}{V_{c}}\). Given the initial \(CR_{1}=16\), we can find the clearance volume (\(V_{c}\)):\(16=\frac{V_{d1}+V_{c}}{V_{c}}=\frac{266495.55+V_{c}}{V_{c}}\)\(16\cdot V_{c}=266495.55+V_{c}\)\(15\cdot V_{c}=266495.55\text{\ mm}^{3}\)\(V_{c}\approx 17766.37\text{\ mm}^{3}\)Step 2: Calculate the new swept volume and stroke For the target compression ratio (\(CR_{2}=18\)), and keeping \(V_{c}\) constant, the new total volume is:\(18=\frac{V_{d2}+V_{c}}{V_{c}}\)\(18\cdot V_{c}=V_{d2}+V_{c}\)\(V_{d2}=17\cdot V_{c}=17\cdot 17766.37\text{\ mm}^{3}\approx 301028.29\text{\ mm}^{3}\)Now, find the new stroke (\(s_{2}\)) using the new swept volume \(V_{d2}\) and the same bore \(b\):\(V_{d2}=\frac{\pi \cdot b^{2}\cdot s_{2}}{4}\)\(s_{2}=\frac{4\cdot V_{d2}}{\pi \cdot b^{2}}=\frac{4\cdot 301028.29\text{\ mm}^{3}}{\pi \cdot (80\text{\ mm})^{2}}\approx 60.07\text{\ mm}\)Step 3: Determine the increase in stroke The increase in stroke is the difference between the new stroke and the initial stroke:\(\text{Increase}=s_{2}-s_{1}=60.07\text{\ mm}-53\text{\ mm}\approx 7.07\text{\ mm}\)Answer: The required increase in stroke is approximately 7.07 mm

[BassVirolla]

Not my maths, asked AI
If we work with a hypothetical bore 80mm and stroke 53mm, how much would the top of the piston have to be closer at TDC to increase compression ration from 16:1 to 18:1 and it spat out an answer if 7.07mm which I think is impossible. Also, the ai maths could be wrong.

Step 1: Determine the initial swept volume and clearance volume The initial swept volume (\(V_{d1}\)) is calculated using the bore (\(b=80\text{\ mm}\)) and initial stroke (\(s_{1}=53\text{\ mm}\)):\(V_{d1}=\frac{\pi \cdot b^{2}\cdot s_{1}}{4}=\frac{\pi \cdot (80\text{\ mm})^{2}\cdot (53\text{\ mm})}{4}\approx 266495.55\text{\ mm}^{3}\)The compression ratio (\(CR\)) formula is \(CR=\frac{V_{d}+V_{c}}{V_{c}}\). Given the initial \(CR_{1}=16\), we can find the clearance volume (\(V_{c}\)):\(16=\frac{V_{d1}+V_{c}}{V_{c}}=\frac{266495.55+V_{c}}{V_{c}}\)\(16\cdot V_{c}=266495.55+V_{c}\)\(15\cdot V_{c}=266495.55\text{\ mm}^{3}\)\(V_{c}\approx 17766.37\text{\ mm}^{3}\)Step 2: Calculate the new swept volume and stroke For the target compression ratio (\(CR_{2}=18\)), and keeping \(V_{c}\) constant, the new total volume is:\(18=\frac{V_{d2}+V_{c}}{V_{c}}\)\(18\cdot V_{c}=V_{d2}+V_{c}\)\(V_{d2}=17\cdot V_{c}=17\cdot 17766.37\text{\ mm}^{3}\approx 301028.29\text{\ mm}^{3}\)Now, find the new stroke (\(s_{2}\)) using the new swept volume \(V_{d2}\) and the same bore \(b\):\(V_{d2}=\frac{\pi \cdot b^{2}\cdot s_{2}}{4}\)\(s_{2}=\frac{4\cdot V_{d2}}{\pi \cdot b^{2}}=\frac{4\cdot 301028.29\text{\ mm}^{3}}{\pi \cdot (80\text{\ mm})^{2}}\approx 60.07\text{\ mm}\)Step 3: Determine the increase in stroke The increase in stroke is the difference between the new stroke and the initial stroke:\(\text{Increase}=s_{2}-s_{1}=60.07\text{\ mm}-53\text{\ mm}\approx 7.07\text{\ mm}\)Answer: The required increase in stroke is approximately 7.07 mm

Even without doing any numbers, a difference in stroke achieves an increase in displacement, and from the top of my head, after having assembled some engines, 7mm is HUGE. No way this is the number.

But talking about making a real engine, would make much more sense to calculate an increase in rod ratio or piston crown height to increase CR without increasing displacement.

Nevertheless, my numbers tell me:

(400cc + Combustion Chamber cc)/Comb. Ch. cc = CR

This gives me a combustion chamber of 26cc for CR = 16 and 23,5cc for CR = 18.

With the piston surface area, assuming a cylindrical combustion chamber, 4,7mm in height for CR = 18 and 5,2mm in height for CR = 16

0,5mm of difference with a long rod in some aluminum alloys is not too far fetched (even while thinking in an aluminum rod is quite a stretch).

Disclaimer: I can be wrong. Numbers quickly put in my kitchen whiteboard.

[wuzak]

From technical regulations p.61

C5.1 Engine specification
C5.1.1 Only 4-stroke engines with reciprocating pistons are permitted.
C5.1.2 Engine cubic capacity must be 1600cc (+0/−10cc).
C5.1.3 All engines must have six cylinders arranged in a 90° “V” configuration and the normal section of
each cylinder must be circular.
All six cylinders must be of equal capacity.

They do not specify a bore or stroke, just engine capacity.
I'm just trying to think how the alleged teams (Merc, Redbull) would increase compression. Expanding piston, but not in width just height? Is that possible?

C5.4 Power unit geometrical constraints and dimensions
C5.4.1 The cylinder bore diameter must be 80mm (±0.1mm).
C5.4.2 The cylinder bore spacing must be 101.0 ±2mm.

[Tommy Cookers]

Even without doing any numbers, a difference in stroke achieves an increase in displacement, and from the top of my head, after having assembled some engines, 7mm is HUGE. No way this is the number.
But talking about making a real engine, would make much more sense to calculate an increase in rod ratio or piston crown height to increase CR without increasing displacement.
Nevertheless, my numbers tell me:
(400cc + Combustion Chamber cc)/Comb. Ch. cc = CR
This gives me a combustion chamber of 26cc for CR = 16 and 23,5cc for CR = 18.
With the piston surface area, assuming a cylindrical combustion chamber, 4,7mm in height for CR = 18 and 5,2mm in height for CR = 16
0,5mm of difference with a long rod in some aluminum alloys is not too far fetched (even while thinking in an aluminum rod is quite a stretch).
Disclaimer: I can be wrong. Numbers quickly put in my kitchen whiteboard. :lol:

this seems about right
(but the swept volume is 266cc not 400cc)

Al alloy has 13 ppm/deg F expansion (maraging steel and titanium both about 8 ppm Al/titanium about 10 ppm)
ie 200 deg F on a rod 200mm overall gives 0.52 mm thermal expansion

NO MYSTERY !!

EDIT
we must also consider the dimensional changes with temperature of the engine 'block'
this is presumably a low-expansion Al alloy in compression by a lot of high-tensile through-studs
the coolant temperature is rather low (lower than in road cars)

[venkyhere]

Why is it such a surprise to see engine manufacturers using material science tricks to utilie different geometries when engine is hot v/s cold ? (forget exotic materia laden F1 engines, even regular engines experience this to a tiny extent) - designing the shapes and choosing materials of course will be aimed to extract every last ounce of the performance juice. I am sure this was in play right from 2014 itself by all teams even Renault

[Holm86]

[johnny vee]

Not my maths, asked AI
If we work with a hypothetical bore 80mm and stroke 53mm, how much would the top of the piston have to be closer at TDC to increase compression ration from 16:1 to 18:1 and it spat out an answer if 7.07mm which I think is impossible. Also, the ai maths could be wrong.

Step 1: Determine the initial swept volume and clearance volume The initial swept volume (\(V_{d1}\)) is calculated using the bore (\(b=80\text{\ mm}\)) and initial stroke (\(s_{1}=53\text{\ mm}\)):\(V_{d1}=\frac{\pi \cdot b^{2}\cdot s_{1}}{4}=\frac{\pi \cdot (80\text{\ mm})^{2}\cdot (53\text{\ mm})}{4}\approx 266495.55\text{\ mm}^{3}\)The compression ratio (\(CR\)) formula is \(CR=\frac{V_{d}+V_{c}}{V_{c}}\). Given the initial \(CR_{1}=16\), we can find the clearance volume (\(V_{c}\)):\(16=\frac{V_{d1}+V_{c}}{V_{c}}=\frac{266495.55+V_{c}}{V_{c}}\)\(16\cdot V_{c}=266495.55+V_{c}\)\(15\cdot V_{c}=266495.55\text{\ mm}^{3}\)\(V_{c}\approx 17766.37\text{\ mm}^{3}\)Step 2: Calculate the new swept volume and stroke For the target compression ratio (\(CR_{2}=18\)), and keeping \(V_{c}\) constant, the new total volume is:\(18=\frac{V_{d2}+V_{c}}{V_{c}}\)\(18\cdot V_{c}=V_{d2}+V_{c}\)\(V_{d2}=17\cdot V_{c}=17\cdot 17766.37\text{\ mm}^{3}\approx 301028.29\text{\ mm}^{3}\)Now, find the new stroke (\(s_{2}\)) using the new swept volume \(V_{d2}\) and the same bore \(b\):\(V_{d2}=\frac{\pi \cdot b^{2}\cdot s_{2}}{4}\)\(s_{2}=\frac{4\cdot V_{d2}}{\pi \cdot b^{2}}=\frac{4\cdot 301028.29\text{\ mm}^{3}}{\pi \cdot (80\text{\ mm})^{2}}\approx 60.07\text{\ mm}\)Step 3: Determine the increase in stroke The increase in stroke is the difference between the new stroke and the initial stroke:\(\text{Increase}=s_{2}-s_{1}=60.07\text{\ mm}-53\text{\ mm}\approx 7.07\text{\ mm}\)Answer: The required increase in stroke is approximately 7.07 mm

Even without doing any numbers, a difference in stroke achieves an increase in displacement, and from the top of my head, after having assembled some engines, 7mm is HUGE. No way this is the number.

But talking about making a real engine, would make much more sense to calculate an increase in rod ratio or piston crown height to increase CR without increasing displacement.

Nevertheless, my numbers tell me:

(400cc + Combustion Chamber cc)/Comb. Ch. cc = CR

This gives me a combustion chamber of 26cc for CR = 16 and 23,5cc for CR = 18.

With the piston surface area, assuming a cylindrical combustion chamber, 4,7mm in height for CR = 18 and 5,2mm in height for CR = 16

0,5mm of difference with a long rod in some aluminum alloys is not too far fetched (even while thinking in an aluminum rod is quite a stretch).

Disclaimer: I can be wrong. Numbers quickly put in my kitchen whiteboard.

Ahh, thank you. Makes much better sense than my rambling.
Thank you

[BassVirolla]

Even without doing any numbers, a difference in stroke achieves an increase in displacement, and from the top of my head, after having assembled some engines, 7mm is HUGE. No way this is the number.
But talking about making a real engine, would make much more sense to calculate an increase in rod ratio or piston crown height to increase CR without increasing displacement.
Nevertheless, my numbers tell me:
(400cc + Combustion Chamber cc)/Comb. Ch. cc = CR
This gives me a combustion chamber of 26cc for CR = 16 and 23,5cc for CR = 18.
With the piston surface area, assuming a cylindrical combustion chamber, 4,7mm in height for CR = 18 and 5,2mm in height for CR = 16
0,5mm of difference with a long rod in some aluminum alloys is not too far fetched (even while thinking in an aluminum rod is quite a stretch).
Disclaimer: I can be wrong. Numbers quickly put in my kitchen whiteboard.

this seems about right
(but the swept volume is 266cc not 400cc)

Al alloy has 13 ppm/deg F expansion (maraging steel and titanium both about 8 ppm Al/titanium about 10 ppm)
ie 200 deg F on a rod 200mm overall gives 0.52 mm thermal expansion
plus eg 3000 microstrain due to load swing gives another 0.05 mm
plus a crankcase etc strain due to load swing say another 0.03 mm
TOTAL 0.6 mm

MYSTERY SOLVED !!

400cc...

Very used to four cylinders!!!