I know we have talked about this before, and I could search for previous reponses. And, if you have a thread to link here, please do. However, I am starting to look at the timing map, and would like the most recent thoughts of those who have opinions, if you have time to contribute.

I looked at the default timing map in my ECU now, it seemed pretty random. It looked almost like a chicken pecked out number on a keyboard. George, take a look at the file I sent, and you may see what I am talking about.

I ended up setting all the cells around idle at 16 BTDC and it idled better right away. Then I put those cells in the cruise range at 35 or so, and filled in a smooth curve with things that seemed to make sense. As KPA goes up above that, the timing drops out. I have it back down to 16 at 170 KPA which is around ten lbs boost.

Thoughts on how you transition? Are there ways to make the tip in smoother? Can the bottom row at engine braking be higher yet? How much? I seem to recall some saying they had the cruise range set at 45 or 50. Am I remembering that right?

How can one go about playing with timing without a dyno? I know a dyno tune is the ideal way. And, that may eventually happen. But for now, what can one do from the driver's seat with a laptop. How do you know if you are headed in the right direction? What are the signs, besides detonation that the timing has been pushed too far?

Sam

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Ed, Where is the thread you started some time back where you went about elaborately figuring a curve for your distributor. I had it book marked, and then my computer died. All my book marks are gone. I did a search, but was apparently using the wrong key words.

Sam

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http://www.slantsix.org/forum/viewtopic ... ght=costco


keyword = costco

author = emsvitil


(if you're wondering about 'costco', it's because that was the gas I was using.......)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

That's it. Thanks. That is worth making a sticky of. Excellent basic research and reporting. Looks like I can put more total in at the low load, high rpm ranges of the map, if you figure initial, plus centrifugal plus vacuum advance. I have to go to work now, but I know what I am doing when I get home tonight.

Sam

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Here is Sam's current ignition map, for reference:

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It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

Thanks for posting it. That is how the map looked 2 days ago. I changed the idle section last night. Does anybody see anything logical about the numbers in there? In that map I had already reduced the boost range numbers to eliminate ping. So, those numbers are a little more logical. But the 24.3 right next to the 16.5 in idle mode made no sense. George, I will send you a current one tonight.

In the smog control world, they usually reduce the idle advance to enable low RPM's without closing the throttle down too far. Having the throttle blades further open reduces one important component of emissions. But I cannot remember which one. Maybe CO monoxide. It would be interesting to see the timing numbers on an OEM turbo motor such as a Saab, or GM 3.8 v-6.

Ed, in the thread linked above, what vacuum were you pulling for those numbers in your Ideal curve. It seems like for them to be useful, you would have to have had vacuum numbers above where your vacuum advance would be coming in. Did you hold a steady vacuum and accelerate though the RPM. If I know what vacuum you were holding, these numbers would tell me something about how to shape a curve in a timing map.

The way centrifugal and vacuum interact is a very complex thing, as has been stated many times on this forum. Clearly, a dyno would tell all here.

Is there a reason to have a 400 rpm column?

(Lunch break)

Sam

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No idea what the vacuum was.

I got the centrifugal set up using WOT, then adjusted the vacuum pod to avoid any part throttle pinging.


I think that thread is listed in the engine faqs sticky

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Ed, I sent a spread sheet to George which I put together from your information. It represents what a timing map would look like with your findings. Of course there are big holes in it now. I am hoping he will post it and thus generate a little discussion of how to fill it in. If you wish, PM me with your e-mail and I will send it.

If you were running your tests at WOT then the vacuum reading was likely at or near 0 for all of your centrifugal figures. I put those numbers at 85 KPA since that is when the vacuum advance is fully out of the picture. And then at 65 KPA which is when the vacuum is fully in, I used those figures plus 19 degrees. The chart is pretty self explanatory. These could be idealized in a timing controlled ECU, which is what I am hoping to do. But I would like the thoughts of others.

I think for the boost part of the map, I will take tons of timing out, so as to limit the pre ignition, and then start with less fuel and sneak up on the fuel, since it misses and wants to die when there is too much fuel. It seems like running lean would not hurt it if the timing is not advanced to its ideal. Then once I get the fuel functional, I could then add timing back in. That is the plan for now. But first, I will start in the NA section of the map with your numbers, and build from there.

Sam

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I drove my Scion to work today and realized that I do have access to an OEM timing map. I have a scan gauge, which will display map readings as well as timing, if selected. I will try to get some numbers down from that. So far I have noticed that it hits a high of 37 BTDC and a low of 5 at idle. The idle number changes from 5-10 as it idles. I have not identified what parameters effect the idle timing. It jumps up right away to 25 or so coming off idle. This little in line 4 is likely very similar to the /6 in many ways. It certainly is a mild, small engine designed for economy and not power.

Sam

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Here is Sam's Spreadsheet:

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It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

Here is my spark map I ran at Kearney. Note: it is not optimized for cruising or mileage - just WOT in the 1/4. Still, it ran well with no pinging.



Edit: --------------------------------------------------------------------------

The thing to keep in mind is that MS interpolates the settings between the cells. So say we are at WOT, approx 100 KPA. You see between the 1500 RPM and 2000 RPM column the timing goes from 25 to 32 degrees. It does not instantly jump from one to the other. Since there is 500 RPM to go, there are (theoretically) 500 increments between 25 and 32 degrees advance. I say theoretically because I don't know without researching, how granular MS's interpolation is. I know it's at least a tenth of a degree, which ought to be fine enough. It works both ways, interpolating between RPM, and also between MAP.

Something to keep in mind, especially when setting things for boost.
Also to keep in mind, each row in the table above is it's own timing curve and could be plotted as such.

Also, I don't know what that that stray 30 is doing at 80/2000. Likely a typo by me looking at the screen in the sun or not wearing my glasses.

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It's a Slant thing. Even I don't understand.

1974 Duster, EFI /6 soon to be turbo...

Get that Monkay! Get that nasty thing!!

This is an excellent thread! I am following very closely.......

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Yeah....Im the one who destroyed this rare, vintage automobile.....

George, in trying to edit my earlier post, I accidentally deleted it. So, I will say what I was going to put into the edit,:

You row 85 looks similar to Ed's except it jumps up much faster. I wonder if your fueling allows more low rpm advance without detonation than Ed's carb does.

Sam

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I tried to plot some numbers last night on the scion timing while watching the scan gauge as my wife drove on the way to choir practice. This is hard, as it jumps around quite a bit. But I was able to get enough info to make some generalizations.

For the most part, the Scion I4 is timed very much like Ed's timing numbers except:

1. Timing is used to control idle speed. This goes beyond the capabilities of our ECU's but it moved from 10 on down as low as 0 at times. It hung out mostly at 7 or so.

2. Timing did not advance anywhere near as far as our slants do with the OEM vacuum pots. I never saw any numbers over 37. But then, we were not driving very fast. Maybe out on the road they would. I have watched this on my Miata as well, and the Miata advance never gets out of the 20's. I was really scratching my head over this one.

3. The 20 KPA row has numbers about 10 degrees few than KPA row 30. So I am wondering why this is so. Without overun fuel cut off, it was a rule of thumb that high number at very low vacuum were good for mileage. Maybe that has all changed now that fuel is cut clean off in coast down.

So here is the current big question? Is there any performance, or mileage advantage in high idle advance numbers? Our rule of thumb of 15 or 16 does not really seem to yield any drivability advantage. The idle on the slant is tamer with less. When I moved it from 16 to 14, the idle got smoother, and dropped down to 850 from 1000. AFter watching the Scion idle, I am going to try 10 and see if I can improve the idle further. I think the idle quality deteriorates when you have to close down the TB blade too far. Maybe it is harder to regulate the injectors smoothly the closer the duty time gets to its open and close time.

Also for now, I am going to build a timing map around Ed's numbers, and fill in above and below with something that looks reasonable. As to fine tuning those, I could use the knock gauge to monitor if and when it gets too far advanced.

I think in the end, you can likely get where you need to be with Ed's approach using spring changes and vacuum pot adjustment and a lot of trial and error. One of the huge advantages of timing control with an ECU is it is so easy to change and that the timing map can be customized for your particular kind of driving and engine.

George, thanks for posting your timing map. Others out there with MSII or higher are encouraged to post your maps as well. It would be interesting to take a look at other's solution to the timing puzzle.

Sam

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I have to take back the comment about the Scion being like Ed's numbers. The patterns are similar, but for the most part the numbers are higher across the board. I plotted these in quantities enough to make a chart today. It became clear as the chart got full, it is pretty much useless to try and learn something about slants from the Scion's numbers. That was an education in itself. It was interesting to see how the transition from idle to cruise took place though. I will let that project drop.

Sam

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