Special Requirements For Timing/Output Event Scheduling

[BenFenner]

Do we care about cars running nitromethane (drag cars) or anything of that sort?

Maybe, tell us about them?

Nitromethane (and some other fuels) burn quite slowly. 65 degrees BTDC is not unheard of at idle.

Do we care about compound turbo setups running 40-60 psi?

Not if they're running on pump gas with high compression, no. No code in the system will ever pander the needs of people who are stupid and setup their shit in fucked up ways.

What if they are running pump gas + water/meth or some type of race fuel? And lowish compression? Do we care about them? I guess my real question is, do we care about people making over 300 WHP/L on gasoline and upwards of 500 WHP/L? The amount of fuel and air packed into a cylinder to make that kind of power produces a flame front speed requiring 5-15 degrees ATDC timing to make use of the energy in a productive way.

Are we concerned with injecting for diesel engines?

No.

Got it. The fuel injection timing resolution would have to be quite more precise if you were going to support them.

[Fred]

Do we care about cars running nitromethane (drag cars) or anything of that sort?

Maybe, tell us about them?

Nitromethane (and some other fuels) burn quite slowly. 65 degrees BTDC is not unheard of at idle.

If they burn slowly, then they'll not require any ATDC timing, in any region, right?

Do we care about compound turbo setups running 40-60 psi?

Not if they're running on pump gas with high compression, no. No code in the system will ever pander the needs of people who are stupid and setup their shit in fucked up ways.

What if they are running pump gas + water/meth or some type of race fuel? And lowish compression? Do we care about them?

Such setups won't require obscenely retarded timing.

I guess my real question is, do we care about people making over 300 WHP/L on gasoline and upwards of 500 WHP/L?

Sure we do.

The amount of fuel and air packed into a cylinder to make that kind of power produces a flame front speed requiring 5-15 degrees ATDC timing to make use of the energy in a productive way.

Says who? The same guy claiming to need ATDC timing on 16psi with "high flow"? :-p Seriously, the flame front speed is going to depend on compression, chamber shape, fuel type, and many other things. If done well, I strongly doubt that such figures are required or desired. Seriously, you should try some *good* fuel some time, it makes a world of difference...

Are we concerned with injecting for diesel engines?

No.

Got it. The fuel injection timing resolution would have to be quite more precise if you were going to support them.

It looks like you don't got it...

Resolution is easy to attain if it makes sense, there are other operational concerns for diesels which do not fit with the architecture required for spark ignition engines. Resolution is NOT the reason that diesels are not in the game plan.

Fred.

[BenFenner]

If they burn slowly, then they'll not require any ATDC timing, in any region, right?

I couldn't say for sure, but that is probably a semi-safe assumption.

The amount of fuel and air packed into a cylinder to make that kind of power produces a flame front speed requiring 5-15 degrees ATDC timing to make use of the energy in a productive way.

Says who? The same guy claiming to need ATDC timing on 16psi with "high flow"? :-p

Yes. I guess so.

Seriously, the flame front speed is going to depend on compression,

Yes.

chamber shape,

Not really, no.

fuel type,

All gasoline can be lumped into the same boat basically for speed of combustion, even leaded.

and many other things.

No, not really. Assuming a burnable air/fuel mixture, combustion speed is basically related to how dense the mixture is and nothing else. (Fuel type held constant.)

If done well, I strongly doubt that such figures are required or desired.

All I can say is that you should speak to 2010 Redline Pro Time Attack Super Mod FWD Champion Dez Ballard. He campaigns a 650 HP BMW Mini. I believe it is 1.6 liters displacement. It could be slightly more. Find out if he's running ATDC timing anywhere. If he's not, then I'll drop it.

Seriously, you should try some *good* fuel some time, it makes a world of difference...

I've said this before, but I guess I'll have to repeat it. The timing I'm referring to is to make best torque, not avoid detonation. Mean best torque will require very late timing in instances of very high density cylinder charges.

Are we concerned with injecting for diesel engines?

No.

Got it. The fuel injection timing resolution would have to be quite more precise if you were going to support them.

It looks like you don't got it...

Resolution is easy to attain if it makes sense, there are other operational concerns for diesels which do not fit with the architecture required for spark ignition engines. Resolution is NOT the reason that diesels are not in the game plan.

I wasn't meaning to say that the diesels are out because of resolution. I was explaining the reason for my question. If diesel's are not in the main picture, then we can forget about them. I brought it up because we're talking about ignition and fuel timing/resolution in this thread. Diesels would obviously need quite a bit of fuel timing resolution. If we're not concerned with them, then we can avoid bringing them up again.




I wanted to ask this to clarify. Say for example we get a resolution of 0.50 crank degrees for timing. Would the interpolation math still give better resolution? Even if we're limited to 0.05 degree increments on the tuning "maps", could we expect greater resolution when interpolating between cell values?

[lumpensack2003]

>> Fred wrote:
>> chamber shape,
Not really, no.

Of course!
The shape of the combustion chamber affects the charge's velocity vector field.
Google for "squish" ...

>> Fred wrote:
>> and many other things.
No, not really. Assuming a burnable air/fuel mixture, combustion speed is basically related to how dense the mixture is and nothing else. (Fuel type held constant.)

You make a mistake here:
burning speed of combustibles is measured in a dedicated test assembly - not an engine.
If you retain the test assembly an repeat the experiment with different comustibles you can compare the burning speed.
In an engine, you don't ignite a static charge. At the moment of ignition the charge moves with a 3-dimensional velocity vector field. The velocity of the flame front moving through the combustion chamber is generally affected by this vector field.
This vector field again is determined by parameters like:
- engine speed
- engine load
- number, size and position of inlet valves
- cam timing
- diameter, length and angled position of inlet
- ...

And finally:
your assumption, that - as long as it is burnable - the air/fuel mixture doesn't affect the speed of the flame front is plain wrong.

GJ

[BenFenner]

Then we can agree there are plenty of poorly designed, "perfect storm" bad engines that could need very retarded timing?

I know that basically everything affects combustion speed, but I'm talking about the main factor(s). Everything else is orders of magnitude less important.

[BenFenner]

Of course!
The shape of the combustion chamber affects the charge's velocity vector field.
Google for "squish" ...

You mean quench?

I'm very familiar.

For me, while it does a few things, it basically increases the density of the charge (around the ignition source). We already covered density of charge.

your assumption, that - as long as it is burnable - the air/fuel mixture doesn't affect the speed of the flame front is plain wrong.

Compared to the density of the charge, this factor is almost insignificant (which was my point). We can split hairs all day long, but the overwhelming reason for any change in timing in any engine is due to a change in charge density. Next comes a bore diameter change I believe at a distant second. It probably has the second most important role in combustion propagation speed down the cylinder.

[Fred]

Ben, your post(s) is(are) full of shit, pull your head in!

Lumpensack, thanks.

Ben, I don't have the time to type a full blooded reply to your post, but I'm happy to speak to you on the phone about it. I have a VOIP account with free Nth American calls, let me know if you wanna chat.

Fred.

[Fred]

Furthermore, Ben, you're clearly NOT a pyromaniac! Set fire to some different fuels some time and tell me that burn rate is the same for all gasoline like fuels... wrong, so so so so SO wrong.

[lumpensack2003]

You mean quench?

I'm very familiar.

For me, while it does a few things, it basically increases the density of the charge (around the ignition source). We already covered density of charge.

Don't want to be a pettifogger, but this is absolutely wrong.
- in engines with external carburation and homogenous charge, you squish to increase charge velocity
- in engines with internal carburation (i.e. VW FSI) in addition to it you squish to keep charge of higher quality (not density) together and around the spark plug electrodes.

Simply imagine where your piston is and what effect the squish has when you ignite i.e. 30° before TDC.

GJ

[BenFenner]

Since we have so much knowledge here, maybe I can take this opportunity to learn. Can someone give me a few answers to a couple questions?

Holding everything else constant including charge density, swirl vectors, combustion size and shape, AFR, engine rpm, engine load, etc.; how much timing difference can someone expect to see by going from the slowest burning gasoline to the fastest burning gasoline?

Holding everything else constant including charge density, swirl vectors, combustion size and shape, AFR, octane, engine rpm, engine load, etc.; how much timing difference can someone expect to see by going from the least homogeneous burnable charge mixture to the most homogeneous burnable charge mixture?

Holding everything else constant including charge density, swirl vectors, combustion size and shape, octane, engine rpm, engine load, etc.; how much timing difference can someone expect to see by going from the leanest burnable charge mixture to the richest burnable charge mixture?


And for comparison...

Holding everything else constant including swirl vectors, combustion size and shape, AFR, octane, engine rpm, etc.; how much timing difference can someone expect to see by going from the least dense burnable charge mixture to the most dense burnable charge mixture?



Fred, I have a chart from a trusted source that shows the exact tested burn rates of almost all gasoline fuel types in an IC engine environment. I'm having a hard time finding it, but when I do, you'll see that it shows no matter the gasoline fuel type, burn rate doesn't change much in the greater scheme of things.

(You're talking to pyromaniac #1 in my village here.)