matt_gsxr
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| posted on 9/12/09 at 11:57 PM |
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Simple ignition advance question
Hi there,
I have just got my MS1 (running extra) driving my gsxr1100 engine. It already had TBI's and I had set the fueling up with an LC-1. It ran very
nicely.
So, now I am driving the sparks too, and I have it idling and it revs up a bit. I haven't been out in it, as it is all to horrid out at the
moment.
I couldn't find an advance table for this engine, and most spreadsheets and books are based on car engines. So, I have built a table from
various tidbits that I could find, and I am looking forward to testing it all out.
So, here's my questions:
1) What are the clues to good timing? apart from detonation!
2) How is the AFR affected when the timing is out?
3) any other top-tips.
I am intending to wire up a "fake NOS" switch, that will allow me to add/remove 3degs of timing at the press of a button, which might help
me "feel" for the power.
thanks,
Matt
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woolly
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| posted on 10/12/09 at 12:24 AM |
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best ignition just before detonation (can be corrected on that )
afr will alter as not complete combustion
3: still learning myself
woolly
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britishtrident
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| posted on 10/12/09 at 08:32 AM |
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If you get to the stage of detonation you are way over advanced.
(1) Make sure the ignition is not so advanced at cranking speed that it causes problems cold starting --- ie no more than about 5 degrees BTDC
below 500 rpm
(2) Listen for pinking at low and medium crankshaft speeds when pulling hard in high gears -- if you get pinking retard timing 2 degrees at a time
until it stops.
(3) Maximum ignition total advance an engine will take varies it can be as littles as 28 crank degrees or as much as 38.
The most I have ever seen used was 43 degrees specified by a well known Imp engine builder but it gave no more power than when set to 38btdc.
Even without detonation using too much advance at high speed can put excess stress on the pistons and bearings.
[Edited on 10/12/09 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 10/12/09 at 08:38 AM |
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The relationship between AFR and timing is weak mixtures burn slower so an engine running weak will run better if given more advanced ignition
timing.
However a weak mixture can also cause pinking or detonation.
If the AFR is near correct or over rich it has no effect on timing.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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matt_gsxr
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| posted on 10/12/09 at 02:56 PM |
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great tips, thanks.
I guess I need to wire-up my advance/retard switch and go for a drive and see if I can feel any power differences.
I have already run into the starting problem. Fortunately the MegaSquirt stuff allows different cranking timing so I played with that.
I have seen 39deg as the recommended maximum advance for a 1D ignition table for the GSXR1100. So I will aim just below that for WOT. For smaller
throttle openings I should be able to go a bit higher.
Is there any effect on the measured lambda from early/late timing that is worth looking out for? I know optimal timing is affected by mixture
strength and quantity, but I was wondering if I could use my lamba probe to advantage (the fueling is already good as I set it up with the stock
ignition unit).
Thanks again,
Matt
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fatbaldbloke
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| posted on 10/12/09 at 06:27 PM |
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quote:
1D ignition table
Do you mean that, just revs alone, no throttle position (or vice versa)?
With megasquirt you really should be running a 2d table to take advantage. You can have 15 degrees difference between light load and full load at the
same engine speed, as well as the 30 degree or so difference between idle and max revs.
If you really are runninng 1d you could well be 10-15 degrees away from optimum under certain load/speed combinations.
Can you post your ignition table in this thread?
[Edited on 10/12/09 by fatbaldbloke]
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dhutch
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| posted on 10/12/09 at 09:35 PM |
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Presumably by that he means without load sensing (tps or map) as you cannot have a ignition system without crank possition which in itself gives
engine speed. Although that would be a 2d map. (1d is single value)
As i understand he is running a 3D map however, but has been able to find a copy of a suitable 2D map for the correct engine and is hence able to make
some use of that.
Daniel
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matt_gsxr
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| posted on 10/12/09 at 11:56 PM |
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Sorry for the confusion.
Mr dhutch has guessed correctly.
The stock gsxr1100 has RPM input only. I am using MS to get the benefits of TPS and RPM input (plus the other odds and sods) my only reason for
bringing up stock GSXR1100 is that it provides a guide to the values I will need at WOT. Agreed, at lower throttle opening I can put more advance,
also I should be able to have a bit more at high RPM above peak torque.
I need to write my own table from scratch, which I have done. My question really was how do I improve this table without a rolling road.
Matt
p.s. Finally a rant about 1d, 2d, 3d.
1d 2d 3d. Its all a bit bogus. Fundamentally what they call 3d mapping is a 2 dimensional array of values. A grayscale picture is a 2 dimensional
(2d) array of pixel intensities, we don't call that 3d do we! I know its just marketing but it is annoying that they use this terminology.
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matt_gsxr
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| posted on 10/12/09 at 11:58 PM |
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And my present draft map.
Stock idle is ~1100rpm. Rev limit is 11k rpm.
Matt
 
Rescued attachment draft_table.JPG
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matt_gsxr
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| posted on 14/12/09 at 10:48 AM |
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DON'T USE THE TABLE ABOVE IF YOU ARE RUNNING A GSXR1100W
It isn't right (yet). I will post a table when it is working properly.
Matt
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