Honda Power Unit Hardware & Software

[saviour stivala]

Godlamerosso. Grazzi hafna.

[gruntguru]

but as is the case with any ignition these numbers are floating in accordance with among others, engine speed and engine load so move the PPP point to as near as could be to 14 degrees ATDC.

I should point out here that 14 deg ATDC is not a magic number. It happens that optimal ignition timing for many engines results in peak cylinder pressure occurring at close to 14* ATDC however for very rapid combustion the angle will be less than 14* and for slow combustion it will be greater than 14*.

[Bandit1216]

Because with port injection, you can spray fuel independent of valvetrain or piston motion because the injectors are not inside the CC. With DI you are forced to inject inside the CC, and are limited by piston and valvetrain motion.

Ah, yes limited. But that's different from "lost freedom". I know most simple injection systems spray 4 pulses per 720 deg, better systems use semi sequential injection. 1 pulse per 720 deg, mostly between 120 and 60 deg BTDC but without camsinc you never know wat top. This doesn't bother much, because at idle you will always spray on a closed inlet valve and with wide open throttle you do, but then it doesn't really matter that much. And with camsinc you can inject between 120 and 60 deg BTDC on ignition top, which can give you slightly better idle, especially for high flow injectors for turbo engines.

But I guess with tji you have the freedom from whenever the exhaust valve shut's (I guess about 30 deg ATDC scavenging, up and untill about 40 degrees BTDC ignition. And you can pulse unlimited times in that window, right?

I see no reason why they should not use this entire window. Do they use some kind of miller timing? I work for a Finnish company who makes engines and this kinda looks like lean burn gas engines.

[saviour stivala]

Because with port injection, you can spray fuel independent of valvetrain or piston motion because the injectors are not inside the CC. With DI you are forced to inject inside the CC, and are limited by piston and valvetrain motion.

Ah, yes limited. But that's different from "lost freedom". I know most simple injection systems spray 4 pulses per 720 deg, better systems use semi sequential injection. 1 pulse per 720 deg, mostly between 120 and 60 deg BTDC but without camsinc you never know wat top. This doesn't bother much, because at idle you will always spray on a closed inlet valve and with wide open throttle you do, but then it doesn't really matter that much. And with camsinc you can inject between 120 and 60 deg BTDC on ignition top, which can give you slightly better idle, especially for high flow injectors for turbo engines.

But I guess with tji you have the freedom from whenever the exhaust valve shut's (I guess about 30 deg ATDC scavenging, up and untill about 40 degrees BTDC ignition. And you can pulse unlimited times in that window, right?

I see no reason why they should not use this entire window. Do they use some kind of miller timing? I work for a Finnish company who makes engines and this kinda looks like lean burn gas engines.

5.10.2 up to end of 2013 that mandated an MPFI injection system which in turn lead to a chose of injector on top of each intake port and a shower type injector use to inject for virtually the full four engine cycles (720 crankshaft degrees). That freedom of injection period and that type of shower injection plus also the ability to pre-mix was lost with the 5.10.2 mandated DI-GDI from 2014.

[Bandit1216]

Because with port injection, you can spray fuel independent of valvetrain or piston motion because the injectors are not inside the CC. With DI you are forced to inject inside the CC, and are limited by piston and valvetrain motion.

Ah, yes limited. But that's different from "lost freedom". I know most simple injection systems spray 4 pulses per 720 deg, better systems use semi sequential injection. 1 pulse per 720 deg, mostly between 120 and 60 deg BTDC but without camsinc you never know wat top. This doesn't bother much, because at idle you will always spray on a closed inlet valve and with wide open throttle you do, but then it doesn't really matter that much. And with camsinc you can inject between 120 and 60 deg BTDC on ignition top, which can give you slightly better idle, especially for high flow injectors for turbo engines.

But I guess with tji you have the freedom from whenever the exhaust valve shut's (I guess about 30 deg ATDC scavenging, up and untill about 40 degrees BTDC ignition. And you can pulse unlimited times in that window, right?

I see no reason why they should not use this entire window. Do they use some kind of miller timing? I work for a Finnish company who makes engines and this kinda looks like lean burn gas engines.

5.10.2 up to end of 2013 that mandated an MPFI injection system which in turn lead to a chose of injector on top of each intake port and a shower type injector use to inject for virtually the full four engine cycles (720 crankshaft degrees). That freedom of injection period and that type of shower injection plus also the ability to pre-mix was lost with the 5.10.2 mandated DI-GDI from 2014.

Yes, I understand. But that doesn't mean my theory is impossible.

[saviour stivala]

Ah, yes limited. But that's different from "lost freedom". I know most simple injection systems spray 4 pulses per 720 deg, better systems use semi sequential injection. 1 pulse per 720 deg, mostly between 120 and 60 deg BTDC but without camsinc you never know wat top. This doesn't bother much, because at idle you will always spray on a closed inlet valve and with wide open throttle you do, but then it doesn't really matter that much. And with camsinc you can inject between 120 and 60 deg BTDC on ignition top, which can give you slightly better idle, especially for high flow injectors for turbo engines.

But I guess with tji you have the freedom from whenever the exhaust valve shut's (I guess about 30 deg ATDC scavenging, up and untill about 40 degrees BTDC ignition. And you can pulse unlimited times in that window, right?

I see no reason why they should not use this entire window. Do they use some kind of miller timing? I work for a Finnish company who makes engines and this kinda looks like lean burn gas engines.

5.10.2 up to end of 2013 that mandated an MPFI injection system which in turn lead to a chose of injector on top of each intake port and a shower type injector use to inject for virtually the full four engine cycles (720 crankshaft degrees). That freedom of injection period and that type of shower injection plus also the ability to pre-mix was lost with the 5.10.2 mandated DI-GDI from 2014.

Yes, I understand. But that doesn't mean my theory is impossible.

I do not know what your theory is so cannot comment on it's possibilities. BUT, It is obvious that a DI-GDI fueling system having the injector position fixed to inject fuel directly inside the cylinder cannot start injecting before the exhaust valve is closed.

[henry]

Ah, yes limited. But that's different from "lost freedom". I know most simple injection systems spray 4 pulses per 720 deg, better systems use semi sequential injection. 1 pulse per 720 deg, mostly between 120 and 60 deg BTDC but without camsinc you never know wat top. This doesn't bother much, because at idle you will always spray on a closed inlet valve and with wide open throttle you do, but then it doesn't really matter that much. And with camsinc you can inject between 120 and 60 deg BTDC on ignition top, which can give you slightly better idle, especially for high flow injectors for turbo engines.

But I guess with tji you have the freedom from whenever the exhaust valve shut's (I guess about 30 deg ATDC scavenging, up and untill about 40 degrees BTDC ignition. And you can pulse unlimited times in that window, right?

I see no reason why they should not use this entire window. Do they use some kind of miller timing? I work for a Finnish company who makes engines and this kinda looks like lean burn gas engines.

5.10.2 up to end of 2013 that mandated an MPFI injection system which in turn lead to a chose of injector on top of each intake port and a shower type injector use to inject for virtually the full four engine cycles (720 crankshaft degrees). That freedom of injection period and that type of shower injection plus also the ability to pre-mix was lost with the 5.10.2 mandated DI-GDI from 2014.

Yes, I understand. But that doesn't mean my theory is impossible.

I too wonder if they use late inlet closing, Miller, the imposition of a maximum geometric compression ratio, 18:1, suggests that there mat have been a trend upwards even though compression ratios of 14 or 15:1 seem a more likely value. LIVC with mixture returning to individual inlet runners for premix might be a possibility b

[saviour stivala]

but as is the case with any ignition these numbers are floating in accordance with among others, engine speed and engine load so move the PPP point to as near as could be to 14 degrees ATDC.

I should point out here that 14 deg ATDC is not a magic number. It happens that optimal ignition timing for many engines results in peak cylinder pressure occurring at close to 14* ATDC however for very rapid combustion the angle will be less than 14* and for slow combustion it will be greater than 14*.

In my opinion rapid or slow combustion does not change the need for ATDC optimum (PCP - PPP) point (greatest possible burn pressure force on crankshaft angle and for maximum possible power stroke duration). what will need change will be the ignition point (ignition point advance). when the engine achieves (PCP - PPP) at 14 degrees ATDC then maximum brake torque (MBT) is produced, shift the (PCP -PPP) position and less (MBT) is produced. the faster the engine is rotating, the shorter the time for crankshaft angle to reach (PCPN - PPP).

[gruntguru]

but as is the case with any ignition these numbers are floating in accordance with among others, engine speed and engine load so move the PPP point to as near as could be to 14 degrees ATDC.

I should point out here that 14 deg ATDC is not a magic number. It happens that optimal ignition timing for many engines results in peak cylinder pressure occurring at close to 14* ATDC however for very rapid combustion the angle will be less than 14* and for slow combustion it will be greater than 14*.

In my opinion rapid or slow combustion does not change the need for ATDC optimum (PCP - PPP) point (greatest possible burn pressure force on crankshaft angle and for maximum possible power stroke duration). what will need change will be the ignition point (ignition point advance). when the engine achieves (PCP - PPP) at 14 degrees ATDC then maximum brake torque (MBT) is produced, shift the (PCP -PPP) position and less (MBT) is produced. the faster the engine is rotating, the shorter the time for crankshaft angle to reach (PCPN - PPP).

You might have missed the point. 14* is not a magic number. Different engine designs will result in a different value for the optimum value for PCP.

With the rapid combustion obtained with TJI it is likely that PCP for the F1 engines occurs at less than 14*.

[godlameroso]

~14 degrees after TDC is where the rod and piston assembly can transfer maximum mechanical leverage to the crank, thus it is the ideal point to have highest cylinder pressure.

This will vary slightly with deck height and rod ratio.

[Bandit1216]

[quote=
This will vary slightly with deck height and rod ratio.
[/quote]

Haha, was just about to add that!

[Bandit1216]

5.10.2 up to end of 2013 that mandated an MPFI injection system which in turn lead to a chose of injector on top of each intake port and a shower type injector use to inject for virtually the full four engine cycles (720 crankshaft degrees). That freedom of injection period and that type of shower injection plus also the ability to pre-mix was lost with the 5.10.2 mandated DI-GDI from 2014.

Yes, I understand. But that doesn't mean my theory is impossible.

I do not know what your theory is so cannot comment on it's possibilities. BUT, It is obvious that a DI-GDI fueling system having the injector position fixed to inject fuel directly inside the cylinder cannot start injecting before the exhaust valve is closed.

My theory is that they might be injecting fuel from right after the exhaust closes, up and untill about 40 deg BTDC, probably in multiple stages. Still a window of aprox. 300 to 250 crank degrees.

[saviour stivala]

Yes, I understand. But that doesn't mean my theory is impossible.

I do not know what your theory is so cannot comment on it's possibilities. BUT, It is obvious that a DI-GDI fueling system having the injector position fixed to inject fuel directly inside the cylinder cannot start injecting before the exhaust valve is closed.

My theory is that they might be injecting fuel from right after the exhaust closes, up and untill about 40 deg BTDC, probably in multiple stages. Still a window of aprox. 300 to 250 crank degrees.

Thanks for making your theory clear. So going by your theory and re-calling you asking “Why they lost their freedom?” of injection duration. (1) Having a window of 250 crankshaft degrees would have lost them freedom of the rest to the 720 degrees (470). (2) Having a window of 300 crankshaft degrees would have lost them freedom to the rest to the 720 (420). And that is besides the pre-mixing ability which is not easy to match.

[saviour stivala]

I should point out here that 14 deg ATDC is not a magic number. It happens that optimal ignition timing for many engines results in peak cylinder pressure occurring at close to 14* ATDC however for very rapid combustion the angle will be less than 14* and for slow combustion it will be greater than 14*.

In my opinion rapid or slow combustion does not change the need for ATDC optimum (PCP - PPP) point (greatest possible burn pressure force on crankshaft angle and for maximum possible power stroke duration). what will need change will be the ignition point (ignition point advance). when the engine achieves (PCP - PPP) at 14 degrees ATDC then maximum brake torque (MBT) is produced, shift the (PCP -PPP) position and less (MBT) is produced. the faster the engine is rotating, the shorter the time for crankshaft angle to reach (PCPN - PPP).

You might have missed the point. 14* is not a magic number. Different engine designs will result in a different value for the optimum value for PCP.

With the rapid combustion obtained with TJI it is likely that PCP for the F1 engines occurs at less than 14*.

I did not miss your point and I did not call the 14 degree ATDC a magic number. Agree that different engine designs could result in a different value for the optimum PCP/PPP + MBT, but any number above that will come at the cost of a shorter power stroke duration. But I do not agree that a rapid or slower burn will move or effect the moving of the 14 degree ATDC optimum point. The engine designs items that can move that optimum point is as Godlameroso has explained (con-rod center to center length to crank radius ratio). The 14 degree ATDC number seems to me to be the number vastly agreed upon by most people that matter, some people also that matter, sometimes adds (+) 1 to 2 degrees to the number 14 for some con-rod length/crank radius ratios but admits that will result in a shorter power stroke duration. Also I never read anybody deducting (-) any degrees from the number 14.

[Bandit1216]

Yes. I thought you meant they lost all freedom, but I was clearly mistaken.

At least the direct injection pressure is much higher, which I guess helps mixing a lot.