Megasquirt Support Forum (MSEXTRA)

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QldRobbo wrote:
I must be missing something....

I'm assuming that 20kpa at 800rpm would be able idle, using the formulas above I get 31 degrees of advance at idle.... shouldn't this be more like 10 degrees?
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Try more like 60-80kpa at idle.
The formulas are intended as a good starting point and will never be perfect.
Use whatever advance works on your engine, like you say 10-15 deg is more reasonable for idle.

James
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Does there exist a spark table estimator that works better (10-15 deg at idle w/ ~20kpa @ ~800rpm). I don't think that most people have 60-80 kpa at idle. I also don't think that 30+ degrees is close for advance at idle. Am I missing something?

SSDD wrote:Hi all can someone tell me what the equivalent of your US:
is in Europe, we have here:

Unleaded 98
Unleaded 95
super

It goes by octane rating from lowest to highest. In the US, regular is generally 87 octane, mid-grade is 89, and premium is 91. So yours is probably in order of 95, 98, super. That is assuming those numbers represent octane rating. Octane is the measurement of resistance to knock.

Octane is actually a carbon chain, 8 units long. Gasoline is made up of these carbon chains, but most of what's in gasoline is more along the lines of pentane (5 carbon units long). Octane is a very stable carbon chain and is more resistant to detonation. So having a higher octane concentration in gasoline makes it less likely to pre-ignite.

There are two octane rating methods the "motor" method (producing the "motor octane number" or MON) and the "research" method ("research octane number" == RON). The MON is a more realistic number for performance application, as it is a harsher test and gives lower numbers. In the US our octane numbers are (MON+RON)/2, in the rest of the world, they are typically RON. Your 98 is nearly our 93, but maybe not, as the RON testing method doesn't really focus on the thing that is important to hot rodders.

Google "ron mon octane" and you will find about 75000 hits, all of which give better information that I do.

Eric

What I don't understand from the original post is if I am running an estimated timing max of 37 (chevy 355 w/ vortec heads, no boost), shouldn't I enter that at 20kpa/6000rpm, and subtract down to the 100kpa line?

Even stranger is this stock LT1 ignition table I planned on using. It's not linear at all:

Have a look at this ignition map. It comes from the Jeff Hartman book, Fuel Injection installation, performance tuning, modifications. I modeled this map for my car.

Note the valley at 800rpm for some level of idle adjustment. As the idle drops, the ignition advances and will increase the idle. The advance at idle is very low, but as the rpm increases (ie when first touching the throttle) the idle is advanced for a quick boost in power.

Thanks woh. That graph makes me feel better. Mine looks very similar when you consider my torque peak is higher (around 4100), and I haven't added extra advance at the idle end. Maybe I should add some.

Please read through my numbers and give me some advice:

Engine: Volkswagen Golf II 1600 cc. Carburator Pierberg 2E2 (engine code RF).
Now it's turbocharged (up to 150 kPa). Garret T25 with intercooler. Carburator changed to Weber 34DMTR.
1) at 1000 rpm (idle speed) i've got 40 kPa and 18° timing
2) at 1000 rpm and 100 kPa must be 6° (as by manual)
(these 2 points taken from volkswagen manual).

With 0.3° per 1 kPa at stated in your manual I can't get these points, that's why I try 0.2° per 1 kPa.
After trying these calculations I get 4° at 1000 rpm and more then 100 kPa which is not good for the engine ang manually changed it to 6°.

Why is maximum advance for further timing calculations (for boosted or NA engines) is assumed to be reached at 3000 rpm and not at higher rpm?

What do you think about my calculations (shown in xls file)?

QldRobbo wrote:I must be missing something....

I'm assuming that 20kpa at 800rpm would be able idle, using the formulas above I get 31 degrees of advance at idle.... shouldn't this be more like 10 degrees?

I was always told that the correct spark timing @ idle is the value that produces the lowest MAP.

When I megasquirted my Rover V8, the best idle was achieved @ about 35 deg BTDC on 98 RON fuel. I also got the idle MAP down to 30 kPa. The timing was taken care of the old fashioned way with a distributor and so with that timing, although I didn't get any detonation, the power was noticably lower and dropped 15-20 RWKW on the dyno. So I had to settle for less advance, a rougher idle but more power and better economy.

Of course, keeping in mind that that engine had an 8.13:1 CR.

Is it just me or does the "you can update this with your RPM values" table not work? mark

ahhh because all advance above 3000rpm is the same for the same MAP , gotcha

DJ Kill wrote:
Why is maximum advance for further timing calculations (for boosted or NA engines) is assumed to be reached at 3000 rpm and not at higher rpm?

same question :why 3000 rmp? on a suzuki swift i have set the redline to 8300 rpm and i dont understend why a flat map from 3000 rpm to 8300 rpm

And i tried the XLS spreadsheet "just for the fun of it" and thought the advance figures at low rpms, especially around idle became VERY weird...

The idle advance figure ended up at the 100kpa bin, now that can´t be right ?

if i put in 8 degrees idle advance i get 29degrees advance at 30kpa/800rpm , that´s a bit rough on a standard engine i think

Although it follows the general "guideline" of advancing the timing at lower loads i don´t think that way of doing it would work to well every time, you need to scale it up so the lower left corner on the "MT" screen becomes low for the idle to work nicely. On most cars anyhow.

What about lumpy cams (i have rally cam) and what table i must use to run correctly ?

woh wrote:...Have a look at this ignition map. It comes from the Jeff Hartman book, Fuel Injection installation, performance tuning, modifications. I modeled this map for my car...

Werner, the statement at the bottom of the pic says the greatest advance at highest load, but unless I'm reading it wrong (lowest pressure and rpm 'idle' at top left and highest pressure about 100kpa at bottom center), it shows the greatest advance at light load where cruise would be. The map in general appears okay but the statement appears wrong - no?
David

Yes, I can see how you might see it that way.

What he is trying to point out is that at maximum load (front of graph at 1024millibar) the maximum advance is at the maximum torque range.

Either that or the comment is wrong.

OpenOffice.org

can open excell sheets and is free for download.

snillet wrote:And i tried the XLS spreadsheet "just for the fun of it" and thought the advance figures at low rpms, especially around idle became VERY weird...

The idle advance figure ended up at the 100kpa bin, now that can´t be right ?

if i put in 8 degrees idle advance i get 29degrees advance at 30kpa/800rpm , that´s a bit rough on a standard engine i think

Although it follows the general "guideline" of advancing the timing at lower loads i don´t think that way of doing it would work to well every time, you need to scale it up so the lower left corner on the "MT" screen becomes low for the idle to work nicely. On most cars anyhow.

Can anyone comment on this, I couldn't agree more with what's said above. I'd really like to use this generated map as it is very close to what a friend tuned his car to (at no small expense) on a rolling road (within 1 degree at nearly all points!). Except around idle.

The best approach I can see to this is to create a flat little island in the map where the engine idles, say a 4x4 grid with an advance of 10,10,10,10 and all around it, the timing will leap back up to the generated values...

Cheers
Dave

do you all think this map will work on my 3TC?

CHB wrote:do you all think this map will work on my 3TC?

That looks like a ton of spark advance under boost - does this motor make boost? I really hope not!

Excellent guidelines for setting up a starting point ignition map Lance!

After uppgrading to headers and dual 2,5" exhaust and goint to squirt'n spark extra, I really wanted to use the "standard" ignition timing for my car, but that was sort of lost as i locked up the distributor and threq the vacuum unit away..

I had some of the key figures for thew stock setting, but didn't quite know how to turn that in to an ignition map "emulating" the stock distributor advance.

Figure it wouild make sense to tune fuel first using a known working ignition timing, and start tweaking once the fuleing was sorted!