F1technical.net

Lower compression ratio is more stable for engines. Less prone to knock.

I think he is alluding to the shape of the piston surface when he says that.

The manufacturers relied on a pre-chamber ignition however it is suspected thar the crown of the piston helps to shroud the pre-chamber when fuel is injected. It's easier with a higher piston crown. That is my theory.

PlatinumZealot wrote: ↑

22 Jan 2026, 04:11

Lower compression ratio is more stable for engines. Less prone to knock.

I think he is alluding to the shape of the piston surface when he says that.

The manufacturers relied on a pre-chamber ignition however it is suspected thar the crown of the piston helps to shroud the pre-chamber when fuel is injected. It's easier with a higher piston crown. That is my theory.

''The manufacturers relied on a pre-chamber ignition, however it is suspected that the crown of the piston helps shroud the pre-chamber when fuel is injected. it's easier with a higher piston crown, That is my theory''. I am totally taken by surprise with this statement, more so coming from 'PZ'. The rules mandate only one injector per cylinder and the fuel injected must be 'direct injection', Apart from the 'only one injector per cylinder is allowed', direct injection means injector must inject fuel inside cylinder/combustion chamber. Now, making use of ignition by a pre-chamber, mean that ignition is initiated inside the pre-chamber with flames spreading out into combustion chamber, for ignition to be initiated inside the pre-chamber, some of the injected fuel inside the cylinder/combustion chamber, must get inside the pre-chamber. A high piston crown shrouding the pre-chamber, will certainly not help the injected fuel get into the pre-chamber. In my opinion an 'omega' type of piston crown is the type to use in a pre-chamber system formula 1 ICE.

GhostF1 wrote: ↑

21 Jan 2026, 10:22

Badger wrote: ↑

21 Jan 2026, 10:20

GhostF1 wrote: ↑

21 Jan 2026, 10:05

It was a well known fact, across the paddock, the Honda had a distinct advantage in it's deployment and regen abilities. It had been mentioned several times by Merc personnel as well. While their battery had a significant lifespan advantage over the season.

I prefer to go by what I can actually see in the telemetry, and there Merc clearly had more deployment on energy limited tracks. Whether that was down to the battery, or the MGU-H, or something else, I don’t know.

I appreciate that and that's all well and good. It just goes against what a majority are seeing.

Having 'less clipping'/ more deployment on energy limited tracks can only be down to the MGU-H capability of supplying MGU-K directly.

PlatinumZealot wrote: ↑

22 Jan 2026, 04:11

Lower compression ratio is more stable for engines. Less prone to knock.

I think he is alluding to the shape of the piston surface when he says that.

The manufacturers relied on a pre-chamber ignition however it is suspected thar the crown of the piston helps to shroud the pre-chamber when fuel is injected. It's easier with a higher piston crown. That is my theory.

Yeah absolutely fair, and a good interpretation of what he's saying. To me, it sort of centres around the idea that their entire "Rapid combustion" technique they developed was based on pressure shockwaves, from the prechamber jets lighting off, causing auto-ignition at the pistons circumference. If the absolute pressure within the chamber during the compression stroke, regardless of piston shape, is not within threshold before ignition, the chances of those shockwaves, upon ignition, having the ability to auto-ignite the mixture at the cylinder extremities will be significantly decreased and as such, won't be a reliable combustion method. I suppose prechamber jet orifice size/shape development could help in some aspects? Not sure.

We don't have all the parameters to go into exactly the type of pressures they are seeing, but rudimentary calcs with what we do know would suggest, if everything remained as it were with a 2025 spec engine, reducing the compression ratio from 18:1 to 16:1 would show a roughly 14% reduction in chamber pressures (before ignition). This is pretty significant, and then there's the new fuels. Some rumours suggesting they're lower octane, so other parameters might be reduced to get the best out of them which could further reduce the likelihood of an ideal environment for rapid combustion.

All hearsay of course!

Badger wrote: ↑

21 Jan 2026, 14:19

Bill wrote: ↑

21 Jan 2026, 13:05

Most team are having problems with the news fuels apparently because the got components in them that combust at different temperatures so i doubt that having a pu with high compression ratio is a good idea .it could easily lead to engine knocking.

That conflicts with the comments we've heard from the people who ought to know.

Ben Hodgkinson

From a purely technical point of view the compression ratio limit is too low. We have the technology to make the combustion fast enough, so the compression ratio is way too low. We could make 18:1 work with the speed of combustion that we've managed to get, which means there's performance in every tenth of a ratio that you can get. Every manufacturer should really be aiming at 15.999 as far as they dare when it's measured.

Ben is probably thumping his chest ,he is the guy who came with that info that they are having problems with fuels i think after hearing about merc alleged trick of course he will say they are capable of those tricks too .the truth of matter as it has already being discussed some teams have asked fia to use petrol during testing instead of new fuels because they are having problems

FIA probably lowered compression ratio anticipating the new fuels to be difficult (and inconsistent), and essentially they were reducing the difficulty level for new entrants like Audi, RB-Ford, and Cadillac, but we hearing from an engine makers "hey why you'd lower it for?!" which could be a bluff as well!

Bill wrote: ↑

22 Jan 2026, 09:08

Badger wrote: ↑

21 Jan 2026, 14:19

Bill wrote: ↑

21 Jan 2026, 13:05

Most team are having problems with the news fuels apparently because the got components in them that combust at different temperatures so i doubt that having a pu with high compression ratio is a good idea .it could easily lead to engine knocking.

That conflicts with the comments we've heard from the people who ought to know.

Ben Hodgkinson

From a purely technical point of view the compression ratio limit is too low. We have the technology to make the combustion fast enough, so the compression ratio is way too low. We could make 18:1 work with the speed of combustion that we've managed to get, which means there's performance in every tenth of a ratio that you can get. Every manufacturer should really be aiming at 15.999 as far as they dare when it's measured.

Ben is probably thumping his chest ,he is the guy who came with that info that they are having problems with fuels i think after hearing about merc alleged trick of course he will say they are capable of those tricks too .the truth of matter as it has already being discussed some teams have asked fia to use petrol during testing instead of new fuels because they are having problems

Where did he say that? Give us the quote and source.

It doesn't make sense to "thump your chest" about something when you are actually struggling with it. He's a real paddock source saying the exact opposite of what you are saying That doesn't eliminate the possibility that someone is struggling with their fuel, but not everyone.

Badger wrote: ↑

22 Jan 2026, 12:29

Bill wrote: ↑

22 Jan 2026, 09:08

Badger wrote: ↑

21 Jan 2026, 14:19

That conflicts with the comments we've heard from the people who ought to know.

Ben Hodgkinson

Ben is probably thumping his chest ,he is the guy who came with that info that they are having problems with fuels i think after hearing about merc alleged trick of course he will say they are capable of those tricks too .the truth of matter as it has already being discussed some teams have asked fia to use petrol during testing instead of new fuels because they are having problems

Where did he say that? Give us the quote and source.

It doesn't make sense to "thump your chest" about something when you are actually struggling with it. He's a real paddock source saying the exact opposite of what you are saying That doesn't eliminate the possibility that someone is struggling with their fuel, but not everyone.

Maybe problems is not the right word but technically challenges are the are his real words "They are more complex, because they are composed of elements with different evaporation points.”
“With sustainable fuels, some components evaporate later than others, and this makes combustion more complex. We are working with hotter combustion chambers, a condition that opens up.

Bill wrote: ↑

22 Jan 2026, 12:40

Badger wrote: ↑

22 Jan 2026, 12:29

Where did he say that? Give us the quote and source.

It doesn't make sense to "thump your chest" about something when you are actually struggling with it. He's a real paddock source saying the exact opposite of what you are saying That doesn't eliminate the possibility that someone is struggling with their fuel, but not everyone.

Maybe problems is not the right word but technically challenges are the are his real words "They are more complex, because they are composed of elements with different evaporation points.”
“With sustainable fuels, some components evaporate later than others, and this makes combustion more complex. We are working with hotter combustion chambers, a condition that opens up.

In other words he didn't say what you attributed to him. But he very clearly said that they could do higher compression, and that the 16:1 CR was "too low".

This is a known issue with “sustainable” / synthetic fuels. In endurance racing, they run into oil dilution issues because the fuel has chains that aren’t easily combusted and won’t evaporate out of the oil. This has been a well documented problem at 24hrs of LeMans and Daytona and has led to car retirements.

Bill wrote: ↑

22 Jan 2026, 12:40

Maybe problems is not the right word but technically challenges are the are his real words "They are more complex, because they are composed of elements with different evaporation points.”
“With sustainable fuels, some components evaporate later than others, and this makes combustion more complex. We are working with hotter combustion chambers, a condition that opens up.

Does it have to be a blend of different components, that evaporate at different temperatures?

AR3-GP wrote: ↑

21 Jan 2026, 02:40

Andi76 wrote: ↑

20 Jan 2026, 17:37

michl420 wrote: ↑

20 Jan 2026, 16:23

Is the MGUK there (in front) mainly for weight distribution reasons or must it be in the surviving cell?

I actually think that with narrower cars, greater attention is being paid to keeping the CoG low at all costs. This wasn't a top priority for the tanks of recent years, but now it's becoming much more important again. What I'm missing is the oil reservoir and the compressor...could Honda have placed the oil reservoir at the rear like Ferrari did in 2014? In general, it looks like a split turbo design with no compressor and no oil reservoir.

It can't be split turbo. The compressor and turbine can only be separated by 175mm.

Thanks for the clarification, i actually did not study these details of the new engine regulations.

So whiled you had not even read the new engine regulations you came on this technical forum firing from the hips.

Andi76 wrote: ↑

23 Jan 2026, 06:33

AR3-GP wrote: ↑

21 Jan 2026, 02:40

Andi76 wrote: ↑

20 Jan 2026, 17:37

I actually think that with narrower cars, greater attention is being paid to keeping the CoG low at all costs. This wasn't a top priority for the tanks of recent years, but now it's becoming much more important again. What I'm missing is the oil reservoir and the compressor...could Honda have placed the oil reservoir at the rear like Ferrari did in 2014? In general, it looks like a split turbo design with no compressor and no oil reservoir.

It can't be split turbo. The compressor and turbine can only be separated by 175mm.

Thanks for the clarification, i actually did not study these details of the new engine regulations.

Just to clarify the clarification...For 2026 PU regs, the split turbo has a maximum distance between the compressor and turbine of 175mm. That distance prevents having a 2025 year type spit turbo, where the Compressor was on the front of the ICE and the turbine at the back. Note that just the bore of the 3 cylinders combined, of a v6, is 240mm.

Note - It doesn't mean that some PU manufacture isn't gonna put the compressor in the heart of the V of the block with the turbine split out on the back of the ICE.

If Memory serves me, the 2014 Honda PU started out with the compressor in the V. It later ran into sizing issues because of that. I believe the lack of MGU-H means the turbos will likely be smaller now in 2026? Regardless, Honda has lots of experience with size limitation.

diffuser wrote: ↑

23 Jan 2026, 19:40

Andi76 wrote: ↑

23 Jan 2026, 06:33

AR3-GP wrote: ↑

21 Jan 2026, 02:40

It can't be split turbo. The compressor and turbine can only be separated by 175mm.

Thanks for the clarification, i actually did not study these details of the new engine regulations.

Just to clarify the clarification...For 2026 PU regs, the split turbo has a maximum distance between the compressor and turbine of 175mm. That distance prevents having a 2025 year type spit turbo, where the Compressor was on the front of the ICE and the compressor at the back. Note that just the bore of the 3 cylinders combined, of a v6, is 240mm.

Note - It doesn't mean that some PU manufacture isn't gonna put the compressor in the heart of the V of the block with the turbine split out on the back of the ICE.

If Memory serves me, the 2014 Honda PU started out with the compressor in the V. It later ran into sizing issues because of that. I believe the lack of MGU-H means the turbos will likely be smaller now in 2026? Regardless, Honda has lots of experience with size limitation.

Then they probably have it in the V again, as the compressor was not visible.