v12 or v10

[Hoffman900]

So. Simply raising the compression ratio through piston crown volume couldn't be used?

Aren't current engines like 18:1 already? I figured that was more down to fuel chemistry than anything else...

Already tight as can be in the squish areas.

NASCAR runs them tight enough that the piston jusssttt starts to kiss the head with carbon build up. Obviously you need to take rod stretch into account.

Raising the dome hurts combustion efficiency. Everyone is all about high static compression, but there is a trade off and more isn’t always better. Domes / raised crowns always hurt that, just a matter how much juice is worth the squeeze. Valve reliefs as well.

NASCAR engines can’t have the aggressive cam profiles from DOHC engines, especially on closing. This limits the space available and/or the time the valve is fully open.

Are you sure? Elaborate on your thoughts and I’ll answer from there.

They run those things very tight and they are at the limit of the metallurgy of the springs. So yes on the lobe profile at the cam, but after it is multiplied by the rocker, it’s every bit as aggressive.

[Jolle]

Already tight as can be in the squish areas.

NASCAR runs them tight enough that the piston jusssttt starts to kiss the head with carbon build up. Obviously you need to take rod stretch into account.

Raising the dome hurts combustion efficiency. Everyone is all about high static compression, but there is a trade off and more isn’t always better. Domes / raised crowns always hurt that, just a matter how much juice is worth the squeeze. Valve reliefs as well.

NASCAR engines can’t have the aggressive cam profiles from DOHC engines, especially on closing. This limits the space available and/or the time the valve is fully open.

Are you sure? Elaborate on your thoughts and I’ll answer from there.

They run those things very tight and they are at the limit of the metallurgy of the springs.

Very sure. Because it the extra weight of the push rods (and the bigger valves), timing has to be less aggressive then engines without this excess (moving) weight. Simply: the more moving parts and weight you have, the slower the acceleration must be.
It’s very well known that aggressive cam profiles, especially at higher RPM is one of the main advantages of dohc engines.

[Hoffman900]

NASCAR engines can’t have the aggressive cam profiles from DOHC engines, especially on closing. This limits the space available and/or the time the valve is fully open.

Are you sure? Elaborate on your thoughts and I’ll answer from there.

They run those things very tight and they are at the limit of the metallurgy of the springs.

Very sure. Because it the extra weight of the push rods (and the bigger valves), timing has to be less aggressive then engines without this excess (moving) weight. Simply: the more moving parts and weight you have, the slower the acceleration must be.
It’s very well known that aggressive cam profiles, especially at higher RPM is one of the main advantages of dohc engines.

To a point, yes, but with rocker multiplication, the NASCAR engines are at the limit of what a valve spring can handle. They didn't gain anything going from flat tappet (velocity limited) to rollers (acceleration limited at the lobe) from being able to open the valve any differently, just friction (source is from someone I casually know at Hendricks). With the way these NASCAR engines are engineered, they are held back by the spring itself, not the system stiffness. Pnuematic buckets would allow them to do different things, but rules.

NASCAR engines typically run 290-288* @ .5mm on the intake and over 25.4mm of lift at the valve. Remember, what is happening at the valve is all that matters.

If you look at the lobe profile from Honda's Third Generation Formula 1 engine, you saw maximum intake valve velocity of 15mm/rad (.0103"in/deg) and acceleration of around 55mm/rad^2 (.03779in/deg^2). This doesn't account for multiplication through the finger follower, but it likely isn't much at that point in the curve (peaks around max lift). An older NASCAR application when multiplied through a 2.37:1 ratio rocker arm, might only be .01778in/deg (velocity) and .00209in/deg^2 (acceleration). Pneumatic "springs" are nice.

I will say DOHC can spin higher, easier, and be more compact overall.

[Jolle]

Are you sure? Elaborate on your thoughts and I’ll answer from there.

They run those things very tight and they are at the limit of the metallurgy of the springs.

Very sure. Because it the extra weight of the push rods (and the bigger valves), timing has to be less aggressive then engines without this excess (moving) weight. Simply: the more moving parts and weight you have, the slower the acceleration must be.
It’s very well known that aggressive cam profiles, especially at higher RPM is one of the main advantages of dohc engines.

To a point, yes, but with rocker multiplication, the NASCAR engines are at the limit of what a valve spring can handle. They didn't gain anything going from flat tappet (velocity limited) to rollers (acceleration limited at the lobe) from being able to open the valve any differently, just friction (source is from someone I casually know at Hendricks). With the way these NASCAR engines are engineered, they are held back by the spring itself, not the system stiffness. Pnuematic buckets would allow them to do different things, but rules.

NASCAR engines typically run 290-288* @ .5mm on the intake and over 25.4mm of lift at the valve. Remember, what is happening at the valve is all that matters.

I will say DOHC can spin higher, easier, and be more compact overall.

The springs are limited because they have to move more weight by default (because of the push rods). Take be pushrods and rockers out of the loop, and the springs can handle a lot more and therefore a more aggressive profile.

Let's assume, the rods and rockers have about the same weight as the valve. Let's put them on 100g for each. So a pushrod engine has to move 200g, a DOHC only 100g. And in practice even less, because of the four small valves vs two big ones.

With the simple equation F = M x A (F=spring, M, weight and A acceleration) you can see that with the same spring, lower weight of the valve, rod and rocker you can achieve higher acceleration, which means more aggressive cam timing.

[Hoffman900]

Very sure. Because it the extra weight of the push rods (and the bigger valves), timing has to be less aggressive then engines without this excess (moving) weight. Simply: the more moving parts and weight you have, the slower the acceleration must be.
It’s very well known that aggressive cam profiles, especially at higher RPM is one of the main advantages of dohc engines.

To a point, yes, but with rocker multiplication, the NASCAR engines are at the limit of what a valve spring can handle. They didn't gain anything going from flat tappet (velocity limited) to rollers (acceleration limited at the lobe) from being able to open the valve any differently, just friction (source is from someone I casually know at Hendricks). With the way these NASCAR engines are engineered, they are held back by the spring itself, not the system stiffness. Pnuematic buckets would allow them to do different things, but rules.

NASCAR engines typically run 290-288* @ .5mm on the intake and over 25.4mm of lift at the valve. Remember, what is happening at the valve is all that matters.

I will say DOHC can spin higher, easier, and be more compact overall.

The springs are limited because they have to move more weight by default (because of the push rods). Take be pushrods and rockers out of the loop, and the springs can handle a lot more and therefore a more aggressive profile.

Let's assume, the rods and rockers have about the same weight as the valve. Let's put them on 100g for each. So a pushrod engine has to move 200g, a DOHC only 100g. And in practice even less, because of the four small valves vs two big ones.

With the simple equation F = M x A (F=spring, M, weight and A acceleration) you can see that with the same spring, lower weight of the valve, rod and rocker you can achieve higher acceleration, which means more aggressive cam timing.

Fair, this is true. I am told you can open a very efficient 4 valve port too fast, and it sees the cam as "overcammed". I don't have enough experience in those applications to know for sure.

However, relating back to NASCAR that doesn't change how tight P-V can be and its effects on compression, which is what the conversation was about.

[Jolle]

To a point, yes, but with rocker multiplication, the NASCAR engines are at the limit of what a valve spring can handle. They didn't gain anything going from flat tappet (velocity limited) to rollers (acceleration limited at the lobe) from being able to open the valve any differently, just friction (source is from someone I casually know at Hendricks). With the way these NASCAR engines are engineered, they are held back by the spring itself, not the system stiffness. Pnuematic buckets would allow them to do different things, but rules.

NASCAR engines typically run 290-288* @ .5mm on the intake and over 25.4mm of lift at the valve. Remember, what is happening at the valve is all that matters.

I will say DOHC can spin higher, easier, and be more compact overall.

The springs are limited because they have to move more weight by default (because of the push rods). Take be pushrods and rockers out of the loop, and the springs can handle a lot more and therefore a more aggressive profile.

Let's assume, the rods and rockers have about the same weight as the valve. Let's put them on 100g for each. So a pushrod engine has to move 200g, a DOHC only 100g. And in practice even less, because of the four small valves vs two big ones.

With the simple equation F = M x A (F=spring, M, weight and A acceleration) you can see that with the same spring, lower weight of the valve, rod and rocker you can achieve higher acceleration, which means more aggressive cam timing.

Fair, this is true. I am told you can open a very efficient 4 valve port too fast, and it sees the cam as "overcammed". I don't have enough experience in those applications to know for sure.

However, relating back to NASCAR that doesn't change how tight P-V can be and its effects on compression, which is what the conversation was about.

You can always open a valve too fast... physics has it's limits.

But the limitations for a DOHC 4 valve, especially for smaller capacities like motorbike or racing engines, "a place for the valves" as a limit how far you can go up with the compression ratio's isn't really an issue compared to pushrod engines, where to have enough opening to flush the cylinder, they will interfere with the piston. Not just because of the limits in acceleration but also they need a bigger lift because of four vs two valves.

[saviour stivala]

I’d like to see it on a naturally aspirated application as well, assuming it can work that fast.

The recent 'auto ignit' combustion developments by formula 1 engine manufacturers is all about the combustion being superfast, as such a like system will be beneficial to high reveing engines with their big bore and shorter time for combustion, But. It will be very near impossible development on past high reving F1 V10'S and V8'S, for the simple reason that those engines would never be able to obtain the necessaey high compression ratio needed, one of the requisits to impliment the 'auto-ignit/super fast' combustion recently developed in F1.

Fast ignition doesn't mean the hardware can cycle at the speed needed for 20k rpm operation. Compression ratio would be an issue as well.

Some might prefer calling 'combustion' in engines as ''an explossion'', it is not. it is smooth progressive burning at low speed of 50 to 150 feet per second. by contrast explosives like dynamite rects at 8800 fps. The latest developed combustion process some call it ''fast ignition/fast ignite'' some call it ''self ignite'' while others call it ''superfast''. All three names results in a combustion which happens in less 'time' than the best of normal combustions. Achieving a combustion that takes less time will result in a more effecient combustion and a more powerful combustion. Because of the less time it takes to combust, the combusting is taking place from start to finish at at higher compression pressure (pressure on piston), this because less 'time' means less piston movement during the combustion process (combustion is taking place at higher compression pressure on the moving piston). The three major requisites that contribute to faster combustion are high compression ratio, high injection pressure and turbulance/tumble swirl of the charge air. The highest known compression ratios the prevoius V10'S and V8'S ever achieved was never greater than 13:1. in fact detonation was never a problem back than.

[Hoffman900]

The recent 'auto ignit' combustion developments by formula 1 engine manufacturers is all about the combustion being superfast, as such a like system will be beneficial to high reveing engines with their big bore and shorter time for combustion, But. It will be very near impossible development on past high reving F1 V10'S and V8'S, for the simple reason that those engines would never be able to obtain the necessaey high compression ratio needed, one of the requisits to impliment the 'auto-ignit/super fast' combustion recently developed in F1.

Fast ignition doesn't mean the hardware can cycle at the speed needed for 20k rpm operation. Compression ratio would be an issue as well.

Some might prefer calling 'combustion' in engines as ''an explossion'', it is not. it is smooth progressive burning at low speed of 50 to 150 feet per second. by contrast explosives like dynamite rects at 8800 fps. The latest developed combustion process some call it ''fast ignition/fast ignite'' some call it ''self ignite'' while others call it ''superfast''. All three names results in a combustion which happens in less 'time' than the best of normal combustions. Achieving a combustion that takes less time will result in a more effecient combustion and a more powerful combustion. Because of the less time it takes to combust, the combusting is taking place from start to finish at at higher compression pressure (pressure on piston), this because less 'time' means less piston movement during the combustion process (combustion is taking place at higher compression pressure on the moving piston). The three major requisites that contribute to faster combustion are high compression ratio, high injection pressure and turbulance/tumble swirl of the charge air. The highest known compression ratios the prevoius V10'S and V8'S ever achieved was never greater than 13:1. in fact detonation was never a problem back than.

The issue is whether the injector and a TJI set up can cycle fast enough. The process is fantastic for reducing time losses. With the HCCI + TJI, you can see how close to TDC it fires. That's the issue.

It actually was a problem. See this paper with photos:
Study on Combustion Monitoring System for Formula One Engines Using Ionic Current Measurement
https://www.hondarandd.jp/point.php?pid=365&lang=en

A combustion monitoring system has been developed by applying ionic current measurement for malfunction diagnosis and combustion management of Formula One engines. In this system the spark plug’s center electrode acts as an ion probe for ionic current measurement, which eliminates the need for additional sensors. The system allows the onboard monitoring of each of the cylinders for their combustion status under all operational conditions. The accuracy and reliability has ensured that the technology can be effectively used for the management of Formula One engines with car-to-pit communication carried out via telemetering. It is capable of various types of controls including detection of misfire, hesitation, detonation and the lean-burn condition. In addition to these points, this paper reports on the relationship between the spark plug center electrode configuration and the absolute quantity of ionic current.

'

Granted at high rpm's, the speed of the piston is out running the ability for detonation to have detrimental effects. Honda did report on the 2008 engine that they did experiment with higher tumble designs to no change. Likely the high rpm reduced time for the tumble vortex to stay intact as well turbulence in the chamber caused by squish action.

[Hoffman900]

You can always open a valve too fast... physics has it's limits.

But the limitations for a DOHC 4 valve, especially for smaller capacities like motorbike or racing engines, "a place for the valves" as a limit how far you can go up with the compression ratio's isn't really an issue compared to pushrod engines, where to have enough opening to flush the cylinder, they will interfere with the piston. Not just because of the limits in acceleration but also they need a bigger lift because of four vs two valves.

Absolutely. Most cam designs start off slow at IVO and then chase the piston from TDC down the bore, being closes around 10* ATDC. This is done mostly for dynamic reasons, especially in pushrod applications, but it also allows one to extend the overlap period some. You would find most REAL racing pushrod systems have asymmetric valve lift profiles.

[echedey]

I have been looking at the specs of the 2006 honda v8 engine and have found some helpful information as I understand this engine is capable of 20000 rpm. in/Exin 5.8 diameter 37g/ex33g I could copy this data for the development of my engine.


https://www.racecar-engineering.com/wp- ... uphv8u.jpg

[CMSMJ1]

The recent 'auto ignit' combustion developments by formula 1 engine manufacturers is all about the combustion being superfast, as such a like system will be beneficial to high reveing engines with their big bore and shorter time for combustion, But. It will be very near impossible development on past high reving F1 V10'S and V8'S, for the simple reason that those engines would never be able to obtain the necessaey high compression ratio needed, one of the requisits to impliment the 'auto-ignit/super fast' combustion recently developed in F1.

Fast ignition doesn't mean the hardware can cycle at the speed needed for 20k rpm operation. Compression ratio would be an issue as well.

Some might prefer calling 'combustion' in engines as ''an explossion'', it is not. it is smooth progressive burning at low speed of 50 to 150 feet per second. by contrast explosives like dynamite rects at 8800 fps. The latest developed combustion process some call it ''fast ignition/fast ignite'' some call it ''self ignite'' while others call it ''superfast''. All three names results in a combustion which happens in less 'time' than the best of normal combustions. Achieving a combustion that takes less time will result in a more effecient combustion and a more powerful combustion. Because of the less time it takes to combust, the combusting is taking place from start to finish at at higher compression pressure (pressure on piston), this because less 'time' means less piston movement during the combustion process (combustion is taking place at higher compression pressure on the moving piston). The three major requisites that contribute to faster combustion are high compression ratio, high injection pressure and turbulance/tumble swirl of the charge air. The highest known compression ratios the prevoius V10'S and V8'S ever achieved was never greater than 13:1. in fact detonation was never a problem back than.

Can you comment on the fuel options too- as that does have a large impact on the speed of burn and the risks of preignition?

[PlatinumZealot]

I've checked some data of the engines the company I work for makes. We have relative new one with V engines in a brought range, all have Quad sequential turbo's except for the V8 which has 2 (sequential)

Although they are a little bigger and run on diesel or HFO it might give some data? The specific fuel consumption does not differ between V8, V10, V12, V14 or V16 of the same engine type. That would imply there no difference in losses between the configs.

Wartsilla?

I think those engine is parallel turbo. The other turbine might be an electric generator, or if you see a second compressor it is an electric blower... depending on engine size.. but I doubt sequential because these engines run within a very small rpm band most of the time. If I recall correctly...

[Ringleheim]

I believe that RPM is a bit optimistic.

Maybe 17-18k is more reasonable.

IIRC. 20k wasnt seen until the Cosworth V8 of 2006.

They were comfortably at 18,500 RPM many years ago with V10s. A V12 for a given displacement would have even smaller pistons so higher engine speeds seem reasonable.

The problem with a 12 vs. 10 (which was resolved in the mid '90s) is that the V-12 has more of everything--more fuel consumption, more heat loads, more size, more weight, bigger radiator need, more aerodynamic drag.

The V10 was the "Middle ground" compromise between a V8 (just not enough grunt) and the V12 (with all the problems I just mentioned).

It's why the sport gradually evolved to everyone running a V10.

Personally, I'd love to see someone bring out a V16 !!! I always wanted Honda to try that back when they ruled F1.

It's a tragedy that F1 teams can't choose engine cylinders.

I pray/hope some day F1 returns to actually being F1.

[echedey]

ok more things I need to know, ferrari put it at 75º degrees the last v12, but as everyone knows the optimum angle is 60º I could put it at 90º and it would work fine without any problems?
'

[Tommy Cookers]

ok more things I need to know, ferrari put it at 75º degrees the last v12, but as everyone knows the optimum angle is 60º I could put it at 90º and it would work fine without any problems?

no
the crankshaft torsional vibrations etc would be worse - so needing a thicker/better crankshaft etc than otherwise
eg the Liberty aero V12 of WW1 was 45 deg and needed this sort of beefing up before going into production
60 deg is best in this regard

'external' vibration would be negligible for any V angle (because it's effectively 2 inline sixes)