Setting up an initial ignition timing table

[rabiddeity]

What's with the magical 3000 RPM number? Wouldn't that change between engines that redline at 5000 and those that redline at 8500 (small inline 4 engines) or even 14000 and up (like motorcycles)? Is that supposed to be RPM for peak torque?

Also, changing the bins in any of the xls files doesn't seem to alter the advance in any of the cells. What am I doing wrong?

[automat]

the files got removed?

error 404

[Darrow]

Why does Toyota say to set the timing at 10deg at idle. (~750rpm). That doesn't seem to be what this thread is saying.

This is for a 1986 Supra 5MGE

[wrenchdad]

That would be for the base timing without any electronic advance from the ECU.

wd

[woh]

There are two schools of thought on setting the advance during idle.

For older cars, before Emission control, the idle was often set to an ignition advance like 10deg. This required the throttle to be open a bit more than with a higher advance giving higher air flow for the same engine rpm. The vacuum advance was connected to the carburettor just upstream of the throttle. During idle there was no vacuum advance. When the throttle was cracked open the advance immediately jumped to ~25deg giving instant increase in power. From my perspective, this is the preferred setting on older cars if you can tolerate the slightly higher hydrocarbon emissions and lower fuel economy during idle. It will give a slightly better take-off from a standing start and better Acceleration enrichment from a start. This generally is also accompanied with a slightly rich (<14.7:1) mixture.

With the advent of emission requirements and fuel economy the vacuum advance was moved to the manifold and high vacuum was applied during idle. This gives the same idle speed with the throttle a bit more closed and often the mixture is very close to stoichiometric. My '74 MG is less stable with these settings than with a richer mixture.

On current cars and electronic control any combination of the above is possible. Which you choose is your choice. Best you find out what the original mfg of the engine did and use those settings as a starting point.

[Azeton]

I couldt open xlm files.

but anyways. i have an m50b25 and found on bmw world these numbers

Valve Timing (IO/IC) 19°btdc/41°abdc
(EO/EC) 35°bbdc/13°atdc


What do the guys that have been doings this for a time get out of this?

[automat]

could someone please repost the xml file that was on the first page?

[robiniddon]

On the subject of why 3,000RPM is seen as the limit of advance:

Denser mixtures burn quicker than sparse mixtures.

Ignoring forced induction for a moment, when running wide open throttle (MAP ~100kpa) you'll have a dense mixture; when running closed throttle (MAP 20-50kpa) you'll have a sparse mixture.

For a given engine and a given mixture density it takes nearly a fixed amount of time to burn that mixture and thus reach peak pressure in the cylinder - this time is independent of RPM. So at low RPM you need to ignite near TDC (low RPM = less advance) and at high RPM you need to ignite further away from TDC (high RPM = more advance). The goal is to get peak pressure ~20 ATDC (as far as I understand it, anyway!).

In the old days, vacuum advance was there to advance timing for sparse mixture (low MAP = more advance) but return to mechanical timing for dense mixture (high MAP = less advance). Today we use the MAF or MAP sensor to infer density.

Old distributor based engines had all timing in by 3,500 RPM or sooner. I cannot say why that is - I have never seen it adequately explained.

I suspect it is as much an artifact of the limits of the mechanical advance systems as it is tuned to the needs of the engine. I suspect that a mechanism that would give all the advance required for peak power at 7,000RPM would have too much in mid range (say 3,000-4,000) and so would knock; rather than have a two-tiered mechanical advance, the designers settled for all in before peak torque. Remember that most mechanical distributor systems probably were push rod engines running no more than 5,500 RPM (barring the real racing stuff).

All the ignition maps that I have seen for electronic ignition on normally aspirated engines that do not have knock control continue to feed in more advance all the way to the red line, though typically the map has an anomaly on the way where timing is retarded compared to neighbouring sites. This probably corresponds to where the mechanical advance limit would have been set for that engine, had it been distributor based.

So, I think that you should aim to make your ignition map taper up from idle to max load/max rpm, rather than flat above 3,000RPM.

I hope that makes some sense!

Cheers,
Robin

[q4_fre]

I have not tried this, but it looks to be a reasonable good guide for turbocharged engines on ignition tuning..

Any comments? What do you think about it?

http://powerpage.dk/tuning_ignition-fil ... p_v106.xls

[offtrack]

q4-fre may God bless you always, for posting that !

hear is one for old fashion dizzys with weighs and vacuum advance on a
MGB.


if found it in the either , out in google spider land.....

[woh]

Here is an update of the MGB Excel file that lets you save the table as a .vex file so you can load it directly into MegaTune.
http://home.comcast.net/~whaussmann/MS_ ... on_map.xls

[kritip]

I'm going to link up my knock sensor to my pc tomo, to record, but i think i'm getting pinking, even though my maximum advance is about 20 degrees


What does pinking/pinging sound like. Sounds like a rattly bearing to me, is that right?

Kristian

[milesinfront]

What does pinking/pinging sound like. Sounds like a rattly bearing to me, is that right?

It varies from engine 2 engine, but yes, it's usually like small metallic rattly sounds.

Here's the XLS files that disappeared:- http://amiles.com.au/IgnitionTimingEstimator_Modded.xls

I'm not the author, so don't take any credit/liability...

[automat]

ah finally the file is back

thank you very much!!!

[reamon308]

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:

Hi I have just been reading this thread and it is just what I have been wondering why all the Ign maps I have seen so far and I am a newby to MS I have had 30 years experience building and servicing engines including Ferrari and what I have come to realise with Ign timing is it is not so much what revs you are at as how good your cycl mix is so forget linear timing curves as yes they do look very nice and orderly, but if you could analisze the mixture for every powerstroke then I am certain it would be all over the place which is what the advance curve should be, and yes I was trained as a mechanic to never let any engine see more than 34 degrees TOTAL advance, but you live and learn that nothing is set in stone and start to question, so now I am not surprised if an engine can and needs over 50 degrees for several hundred revs before dropping back to more normal and of course this can happen several hundred times between idle and max revs so your lovely linear curve from idle to max revs is like some kid has scribbled all over your Graph, so it is all down to how good you can fill your cycls and how fast your fill can burn, so how can we achieve this with MS or is it possible, please someone let me know as I am sure we will not be able to get the max from our engines till we do ??, Regards Reamon

[haddixracing]

I found factory testing documentation on my Mercedes M120 V12 engine and it gives the following timing points. Just in case these are helpful to anyone out there.

Idle
Idle Speed 600-750 rpm
Idle Timing 5-15* BTDC
Idle Injector PW 2.8-3.2ms
Idle Map 58-63 kpa

Peak Torque
WOT at 3800 / 4000 rpm
WOT Timing 18-22* BTDC
Injector PW 12-17 ms
WOT Map 100kpa

[milesinfront]

5-15 @ idle? That doesn't really narrow it down much... Perhaps it uses variable timing to help control idle speed???

[haddixracing]

Yeah, I imagine it bumps the idle timing up when the idle drops below a certain rpm to keep it in range. It doesn't use an IAC valve to control idle so that would make sense.

[joeyg1973]

I read this whole thing and my brain is smoking. I am a newbie and that xls sheet, no matter how much I read posts on this makes no sense. I have a toyota 2f motor that stock has a redline of 4000 and is supposed to have a timing of 7 degrees at 650 rpm. I have had the whole thing balanced as the bottom end of these engines are often out by GRAMS and mine was. I should be able to redline up to 5000 with max torque around 1800 and hp around 3600. I have no clue why this xls wants to give me ~26 degrees at idle.

Please, someone explain this to me.

Joe

ignesttable.jpg

[teslo]

Hi guys, any update on Excel file( or OpenOffice)? Especially for rover v8 ;)