Honda Power Unit Hardware & Software

[63l8qrrfy6]

Forgot to mention - misfire is when the very lean mixture fails to ignite.
It is damaging because it will eventually ignite on subsequent cycles after additional fuel has been added leading to a very strong and abnormal combustion event which can cause high mechanical loads.

[saviour stivala]

How can a direct injection system lean mixture that have failed to combust (misfire) will be/can be re-ignited on the next firing stroke? In a direct injection system any fuel injected that have failed or not to ignite/combust will be expelled with the exhaust gases (exhaust stroke) in between firing strokes.

[63l8qrrfy6]

That makes sence. But when there is no spark, there is no combustion, right. Unless actual detonation occurs.

So that's why turbo's in the old days used to flood fuel to avoid detonation.

So when one advances ignition to avoid detonation one only makes things less bad? I mean, ignite too early, before perfect, to avoid detonation is always worse then ignite at the right time, right?

So this is the big advantage of TJI. No risk of detonation because the mix is too lean in the main chamber, but nevertheless perfect control of ignition timing and relative high flame speed.

The risk of detonation is ever present. F1 engines can and do operate with some degree of it.
Spark is normally retarded rather than advanced to avoid knock but this carries a performance penalty since for any engine speed and load combination there is an optimum spark timing which produces the maximum torque.

The idea behind retarding the spark is that heat is released later in the engine cycle when the piston is further away from TDC and the volume is larger which causes the pressures and temperature to be lower but the work done on the piston also reduces, decreasing the output.

[Bandit1216]

That makes sence. But when there is no spark, there is no combustion, right. Unless actual detonation occurs.

So that's why turbo's in the old days used to flood fuel to avoid detonation.

So when one advances ignition to avoid detonation one only makes things less bad? I mean, ignite too early, before perfect, to avoid detonation is always worse then ignite at the right time, right?

So this is the big advantage of TJI. No risk of detonation because the mix is too lean in the main chamber, but nevertheless perfect control of ignition timing and relative high flame speed.

The risk of detonation is ever present. F1 engines can and do operate with some degree of it.
Spark is normally retarded rather than advanced to avoid knock but this carries a performance penalty since for any engine speed and load combination there is an optimum spark timing which produces the maximum torque.

The idea behind retarding the spark is that heat is released later in the engine cycle when the piston is further away from TDC and the volume is larger which causes the pressures and temperature to be lower but the work done on the piston also reduces, decreasing the output.

Well, that's the part I don't grasp. If detonation occurs at say 30 deg BTDC, why then bother ignition to be retarded to say 20 Deg BTDC. The damages is already done, right.

[63l8qrrfy6]

Detonation is always after the spark.
Any combustion before the spark is pre-ignition.

[Bandit1216]

Detonation is always after the spark.
Any combustion before the spark is pre-ignition.

Aha. Well, I think they are mixed often, even by guys who give tuning tutorials. Or maybe it's even a translation thing. Just like we Dutch call peppers paprika and vice versa.

So pre-ignition is the one that gives a supersonic piston devouring event, and knock is not that bad compared. Sorry to go off topic again in this Honda topic.

It makes a lot more sense now to think of it. This is why a high boost turbo engine with relative high compression and too high inlet temp after IC, is far more subjectable to eat up it's own pistons ones in a while. Compared to a high rpm, natural aspirated, fuel flooded screamer of an engine.

[PlatinumZealot]

Regarding how the fuel enters the pre-chamber. The air fuel mixture is roughly evenly distributed and for the purpose of discussion can essentially be though of as much. There is an equal amount of air and fuel vapor molecules distributed through the chamber volume.

Nope. This is not correct. Look up stratified charge. The name implies this is not so.

[godlameroso]

That makes sence. But when there is no spark, there is no combustion, right. Unless actual detonation occurs.

So that's why turbo's in the old days used to flood fuel to avoid detonation.

So when one advances ignition to avoid detonation one only makes things less bad? I mean, ignite too early, before perfect, to avoid detonation is always worse then ignite at the right time, right?

So this is the big advantage of TJI. No risk of detonation because the mix is too lean in the main chamber, but nevertheless perfect control of ignition timing and relative high flame speed.

These engines detonate a fair bit, and usually when that happens it's after the spark, and usually not that big of a deal. Your road car also detonates at high RPM at full load. What you don't want happening is detonation when the piston is on its upstroke before the sparky goes off.

[PlatinumZealot]

Not quite perfectly applicable - that graph is a function of many parameters and will vary even between different F1 PU engine makes. But yes the shapes of the detonation and misfire zones will be comparable while the numbers on the axes can be quite different (for example the peak power BMEP is around 40 bar)

But generally speaking the F1 engines will operate in the tiny sliver between detonation and misfire, ocasionally crossing over in either zone. We can only speculate on the extent of their operating window in terms of lambda but it might not be too dissimilar to your graph.

All else being equal detonation dissapears either side of lambda 1 because the temperature of combustion decreases the more the mixture deviates from stoichiometric. This is because of the additional heat capacity of excess fuel for rich mixtures or the additional heat capacity of excess air at lean mixtures. Since the heat capacity of fuel is greater that that of air the detonations zone dissapears quicker as the mixture gets richer.

Industrial gas engines normally use one of two types of pre-chambers - either fully "passive" (gas is mixed with air, often ahead of the compressor stage) and as such the mixture is homogenous or "active" (fuel-fed) pre-chamber which allows it to run richer than the rest of the cylinder which is still fed by pre-mixed air/fuel. F1 engines must use some form of hybrid since the injector cannot be physically placed within the pre-chamber yet its spray pattern can be used to enrich it.

Good analysis of the graph. Upvote the man, people.

[godlameroso]

Regarding how the fuel enters the pre-chamber. The air fuel mixture is roughly evenly distributed and for the purpose of discussion can essentially be though of as much. There is an equal amount of air and fuel vapor molecules distributed through the chamber volume.

Nope. This is not correct. Look up stratified charge. The name implies this is not so.

Typically a stratified charge requires the "pent" roof style combustion chambers, or features a bowl on the piston crown. Injection pulse stratification seems very tricky to do. Not impossible however. Still even if we have a homogeneous charge, the prechamber will be a richer fuel mixture than the rest of the chamber.

[Bandit1216]

That makes sence. But when there is no spark, there is no combustion, right. Unless actual detonation occurs.

So that's why turbo's in the old days used to flood fuel to avoid detonation.

So when one advances ignition to avoid detonation one only makes things less bad? I mean, ignite too early, before perfect, to avoid detonation is always worse then ignite at the right time, right?

So this is the big advantage of TJI. No risk of detonation because the mix is too lean in the main chamber, but nevertheless perfect control of ignition timing and relative high flame speed.

These engines detonate a fair bit, and usually when that happens it's after the spark, and usually not that big of a deal. Your road car also detonates at high RPM at full load. What you don't want happening is detonation when the piston is on its upstroke before the sparky goes off.

Yes, correct. Or as Mudflap says "pre-ignition"

While off topic now. And since you guys know more then my youtube tuners;

Or should I ask this in engineering thread? I'm perfectly fine to move (or be moved) to another topic, but;

Does the moment of injection matter in this respect? My (hobby) (simple 4 cyl inline wasted spark) road car does have fully sequential injection at this time, but no cam sinc. So at this moment I've set it to (port) inject it at 90 deg BTDC. I just don't know what stroke it is. 1 could be in compression and 4 in outlet or vice versa. I can change this, as long as I stay later then the first trigger, which is at 138 deg, but earlier then 60 deg BTDC. Al I know the inlet valve is closed on injection when the pulsewidth is low. On wide open throttle, high RPM, the duty cycle of the injectors is 70%, so then it pisses all over, but that doesn't really matter then anymore. Or does it?

At lambda 0.85 at those conditions, does this mean I kinda flood the engine and do not have to worry the mixture pr-igniting too much?

I could go to a dyno, but at this moment I get the feeling everyone who knows more then me has a tuning company and always tend to advise to come and tune there. I am willing to do that, but not 10 times over.

[PlatinumZealot]

Yes, correct. Or as Mudflap says "pre-ignition"

While off topic now. And since you guys know more then my youtube tuners;

Or should I ask this in engineering thread? I'm perfectly fine to move (or be moved) to another topic, but;

Does the moment of injection matter in this respect? My (hobby) (simple 4 cyl inline wasted spark) road car does have fully sequential injection at this time, but no cam sinc. So at this moment I've set it to (port) inject it at 90 deg BTDC. I just don't know what stroke it is. 1 could be in compression and 4 in outlet or vice versa. I can change this, as long as I stay later then the first trigger, which is at 138 deg, but earlier then 60 deg BTDC. Al I know the inlet valve is closed on injection when the pulsewidth is low. On wide open throttle, high RPM, the duty cycle of the injectors is 70%, so then it pisses all over, but that doesn't really matter then anymore. Or does it?

At lambda 0.85 at those conditions, does this mean I kinda flood the engine and do not have to worry the mixture pr-igniting too much?

I could go to a dyno, but at this moment I get the feeling everyone who knows more then me has a tuning company and always tend to advise to come and tune there. I am willing to do that, but not 10 times over.

Sequential injection makes the most difference at low rpm. Saves fuel there. I actually was trying to set this up on Megasquirt. But anyway that project fell by the wayside. To my understanding as long as you spray so that it goes in when the intake vales open that's it. You still some fuel on the valves to keep them clean... With that said at higher rpm things are happening so fast while more injector pulse-width is required it basically turns back into batch firing.

[godlameroso]

That makes sence. But when there is no spark, there is no combustion, right. Unless actual detonation occurs.

So that's why turbo's in the old days used to flood fuel to avoid detonation.

So when one advances ignition to avoid detonation one only makes things less bad? I mean, ignite too early, before perfect, to avoid detonation is always worse then ignite at the right time, right?

So this is the big advantage of TJI. No risk of detonation because the mix is too lean in the main chamber, but nevertheless perfect control of ignition timing and relative high flame speed.

These engines detonate a fair bit, and usually when that happens it's after the spark, and usually not that big of a deal. Your road car also detonates at high RPM at full load. What you don't want happening is detonation when the piston is on its upstroke before the sparky goes off.

Yes, correct. Or as Mudflap says "pre-ignition"

While off topic now. And since you guys know more then my youtube tuners;

Or should I ask this in engineering thread? I'm perfectly fine to move (or be moved) to another topic, but;

Does the moment of injection matter in this respect? My (hobby) (simple 4 cyl inline wasted spark) road car does have fully sequential injection at this time, but no cam sinc. So at this moment I've set it to (port) inject it at 90 deg BTDC. I just don't know what stroke it is. 1 could be in compression and 4 in outlet or vice versa. I can change this, as long as I stay later then the first trigger, which is at 138 deg, but earlier then 60 deg BTDC. Al I know the inlet valve is closed on injection when the pulsewidth is low. On wide open throttle, high RPM, the duty cycle of the injectors is 70%, so then it pisses all over, but that doesn't really matter then anymore. Or does it?

At lambda 0.85 at those conditions, does this mean I kinda flood the engine and do not have to worry the mixture pr-igniting too much?

I could go to a dyno, but at this moment I get the feeling everyone who knows more then me has a tuning company and always tend to advise to come and tune there. I am willing to do that, but not 10 times over.

Tuning without timing an engine?! What black magic wizardry are you hoping to accomplish? Is this a 2 stroke or 4 stroke?

Ideally you want to time the injection pulse around the airflow characteristics as air enters the cylinder. The intake valves typically open on the downstroke, fully open ASAP, then cylinder vacuum is highest(being totally unscientific this) at around 70% of the way to BDC. As this air is entering the chamber, that is the ideal time for fuel delivery, as the rush of air will help disperse the fuel and aid vaporization.

Remember the old snake game on your Nokia? Air entering the cylinder kind of behaves like that, but in more dimensions. You want to "trap the snake" of air and fuel in the CC, then squish it.

[Bandit1216]

These engines detonate a fair bit, and usually when that happens it's after the spark, and usually not that big of a deal. Your road car also detonates at high RPM at full load. What you don't want happening is detonation when the piston is on its upstroke before the sparky goes off.

Yes, correct. Or as Mudflap says "pre-ignition"

While off topic now. And since you guys know more then my youtube tuners;

Or should I ask this in engineering thread? I'm perfectly fine to move (or be moved) to another topic, but;

Does the moment of injection matter in this respect? My (hobby) (simple 4 cyl inline wasted spark) road car does have fully sequential injection at this time, but no cam sinc. So at this moment I've set it to (port) inject it at 90 deg BTDC. I just don't know what stroke it is. 1 could be in compression and 4 in outlet or vice versa. I can change this, as long as I stay later then the first trigger, which is at 138 deg, but earlier then 60 deg BTDC. Al I know the inlet valve is closed on injection when the pulsewidth is low. On wide open throttle, high RPM, the duty cycle of the injectors is 70%, so then it pisses all over, but that doesn't really matter then anymore. Or does it?

At lambda 0.85 at those conditions, does this mean I kinda flood the engine and do not have to worry the mixture pr-igniting too much?

I could go to a dyno, but at this moment I get the feeling everyone who knows more then me has a tuning company and always tend to advise to come and tune there. I am willing to do that, but not 10 times over.

Tuning without timing an engine?! What black magic wizardry are you hoping to accomplish? Is this a 2 stroke or 4 stroke?

Ideally you want to time the injection pulse around the airflow characteristics as air enters the cylinder. The intake valves typically open on the downstroke, fully open ASAP, then cylinder vacuum is highest(being totally unscientific this) at around 70% of the way to BDC. As this air is entering the chamber, that is the ideal time for fuel delivery, as the rush of air will help disperse the fuel and aid vaporization.

Remember the old snake game on your Nokia? Air entering the cylinder kind of behaves like that, but in more dimensions. You want to "trap the snake" of air and fuel in the CC, then squish it.

It's a 4 stoke.

I'm not talking about the timing of the scavenging affect, just the timing when the injector starts injecting. 1st trigger tooth (zero) is 138 deg BTDC and at 90 deg BTDC the injector starts injecting (tooth 7(8) (6deg per tooth)), as I've set it now. At idle (1200) it's open about 4 ms and at full throttle 20 ms. But of course at 7200 rpm, the time you have time is 5 times shorter, and when pulse width is 5 times longer, the duty cycle is 25 times more. So at idle you inject on a closed valve to give it time to evaporate. The 90 deg is more then enough time, the injector is only open 3% of the time. But at WOT the injector is 75% of the time open (of 720 deg) so you inject over a very full range of open and closed inlet valve. (values changed a bit for easy calculus) this is how 95% does it. Bigger injectors to make possible what you say, give you too small bandwidth to get a stable idle.

[Bandit1216]

Just did a run and my duty cycle is even higher. I need to switch to bigger injectors because they don't close anymore at 6600 and lambda leans out. Puls width is 18,1ms and lambda is below target. Dutycycly must be less then 85% or you burn the coils of the injector and I have 1000 rpm to go to the rev limiter. I'm sure F1 have better control than this cheap toy computer of mine. They must have 100 times more resolution on injector pulse width.

At 12000 rpm, and when someone ones to direct-inject multiple times, the window is far less, correct? Let's say they have 120 deg to inject from inlet valve closing to ignition, with some valve overlap and spark advance together being 60 deg. At 12000 rpm this gives them 1,66 ms to inject 2 or perhaps even 3 times, right? (200 Hz so 360 is 5 ms, makes 120 - 1,66 ms) Effectively their max duty cycle is 14%. (120 deg x 85%)

So the injector flowrate must be huge to get 100 kg/h into that engine though 6 injectors.

A picture says more then a 1000 words they say?