Spark table question

[Boost]

In the High Octane and Low Octance tables under Spark, what does "grams per cylinder" represent? Fuel amount? Also, the higher positive number (timing degrees) is advancing more? Thank you.

[Biggsy]

In the High Octane and Low Octance tables under Spark, what does "grams per cylinder" represent? Fuel amount? Also, the higher positive number (timing degrees) is advancing more? Thank you.

Grams/cylinder is air flow

and

Yes, higher the number, more advanced is the timing.

Dave.

[Boost]

Thanks!

Roland

[Biggsy]

No problem!

[redhardsupra]

Grams/cylinder is air flow

and

Yes, higher the number, more advanced is the timing.

Dave.

wrong on both accounts, sorry.

grams/cyl is a unit of airmass. per cylinder airmass multiplied by number of cylinders, divided by 120 and multiplied again by RPM gives you airflow (unit of grams per sec or pounds per minute are common).

airmass is directly related to compression, compression is directly related to torque. the more the torque, the faster the flamefront, thus less advance is needed for the complete burn.

[Ira]

airmass is directly related to compression, compression is directly related to torque. the more the torque, the faster the flamefront, thus less advance is needed for the complete burn.

While you might be able to argue that statement, there are so many things wrong with it it's hard to know where to start.

Airmass is not directly related to compression and as far as I can tell, it's not related at all.
Compression is not directly related to torque, though in general, raising compression causes torque to increase. Doesn't work in 426 Hemi's though because the head has too much surface area.
And while I can't prove it, I'm not sure that flame front speed always follows torque.

And while you're correct when you say grams/cyl is not airflow, in the simplified world of tuning with EFILive, it represents airflow so it's probably OK to call it airflow.

Ira

[joecar]

The distinction is between airflow (rate of mass flowing in) and airmass (mass in the cylinder).

RHS is saying the higher the airmass number, the less timing advance that is needed.
Ira is saying that that this may not always be the case.

I jumped in too late...

Boost, is this what you were asking:
In the Hi Octane table, the vertical axis is timing advance degrees, the higher this number the higher the advance.

[redhardsupra]

While you might be able to argue that statement, there are so many things wrong with it it's hard to know where to start.

Airmass is not directly related to compression and as far as I can tell, it's not related at all.
Compression is not directly related to torque, though in general, raising compression causes torque to increase. Doesn't work in 426 Hemi's though because the head has too much surface area.
And while I can't prove it, I'm not sure that flame front speed always follows torque.

And while you're correct when you say grams/cyl is not airflow, in the simplified world of tuning with EFILive, it represents airflow so it's probably OK to call it airflow.

Ira

ok then, let's hear your take on it. i developed all these dependencies from physics, so i'm not sure how you'd approach dismantling it, but i'm always up for a good discussion. and i'm not being snarky or sarcastic here, i've always wanted to hear some discussion on it, just there aren't any takers.

i'm not talking about static compression, but the actual airmass that later gets squished and exploded. if you have managed to push less air (smaller airmass) into cylinder, no matter what your static/dynamic compression is, you're not gonna make as much power comparing to when you had more airmass.

the speed of the flamefront depends on compression, temperature and AFR. the more pressure you have (compression) the less time it's going to take for the mixture to burn completely. that's just basic chemistry, i dont think you can challange that, if you can, i will nominate you for a Nobel prize in chemistry myself

and no, it's not ok to call airmass airflow, for the same reason it's not ok to call torque horsepower. they're different entities, and if you wanna do science, we gotta adhere to laws, principles and nomencladure of the scientists before us.

[Biggsy]

Sorry guys I accept I was wrong about the grams/cylinder (I knew what I ment, just wrote it wrong )

As for the second bit, I was assuming he was asking about timing degrees, ie. the higher the number in timing the more advanced the timing is.

eg 20deg of timing is more advanced than 15deg of timing

If I miss understood your question boost, I apologise

Dave.

[Big Kahuna]

Sorry guys I accept I was wrong about the grams/cylinder (I knew what I ment, just wrote it wrong )

As for the second bit, I was assuming he was asking about timing degrees, ie. the higher the number in timing the more advanced the timing is.

eg 20deg of timing is more advanced than 15deg of timing

If I miss understood your question boost, I apologise

Dave.

Dave I kinda like your explanation better. The others are starting to get beyond my level of knowledge.

Your example is how I follow things. Its called the KISS principle.
Keep It Simple Stupid!