Ignition map for 1600 engine with Megajolt

[tzepesh]

I am trying to optimize the engine on my car, so I would like some opinions on the ignition map I have.
Background info: 1584cc engine, W100 cam, 4-in-1 exhaust, Megajolt ignition based on TPS, Dellorto DRLA36.
The map that I have now is:

I can't remember how I got to this timing map, but I started from bosch distributors map and reading on autosportlabs.

That was a few years ago, I never got back to reading more. I've got input that this is a bit too aggressive for the engine, so please send me any opinions on how to change it. Maps from your engines are welcome.

Input from Modok on another topic (thank you!, I will start from this to improve the map): Set timing to 7 degrees 1400 rpm and lower at 0 and 10 load and turn up the idle speed screws, if your load is TPS, then at 20% load+ jump timing to 10 or 11 degrees to improve off idle response.
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'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[tzepesh]

I started the engine yesterday with the laptop connected to see throttle position for 3000rpm. I got a big surprize, the TPS is not working, the load remains at 10% all the time. The advance works only depending on RPM. I took off the connector from the sensor and the load is now 100%, as expected.
I will develop the new ignition map considering 50% load at 3000rpm in order to get the initial map.
Instead of using the TPS, of which I was not happy at all from the beginning, I would use MAP, as I have some sensors laying around from Megasquirt. Now, how shall I take the vacuum for MAP? Shall I drill and tap in all intake ports and then go to a vacuum canister with 4 inputs and one output? Where can I get such a canister, or how can I make it (I prefer the diy method)?
Now if I think well, I understand all the things that I considered odd while tuning the carbs: too advanced meant I had to close the throttles more to get a low idle (800rpm) and I had 3-3.5 kg/h reading on the snail synch. Also the engine was running a little hot, also too advanced?

I will start from these distributor curves:

_________________
'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[Boolean]

If it's aggressive or not depends on how well the engine can breath, your squish and your dynamic compression. And a few other things.
It is definitely not the worst universal map I've seen, but there are some things I would change right away.
For example, part load timing can be much higher. Say you went with 28-30 degrees at WOT, and then increase it with 2 degrees for every loadsite below WOT - at all rpm's over 3000.
Blend down to no extra advance at idle.
That would mean 46-48 deg at 10(%?) load. This will increase part load efficiency dramatically.
I like the timing bump at 600 rpm, that will stabilize idle a fair bit. I don't think it's necessary at higher loads though.
Also remember that distributors are really crude timing devices. Copying those will make for an expensive digital 50 year old curve.
To really benefit from your fine system, you need to tune it well on a rolling road.
Also, your engine may not like what I suggested. You must listen to your engine.
They are all different, and my input is only very broadly applicable to air cooled engines.
YMMV, and so on.
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I strive for perfection. Excellence will not be tolerated!
Build thread here:
http://www.thesamba.com/vw/forum/viewtopic.php?t=529379

[tzepesh]

Thank you for the input Boolean. My engine is not breathing better, it has the stock heads for 1600 engine. Therefore I hesitate to run very high numbers for the ignition. I made a starting line copying the advance curve of a 010, from 10% load to 50% load and from 800 rpm to 3000 rpm. Then I increased the advance for lower load and decreased it for higher load. I kept the 600rpm column for idle stabilization and the 100% load for disconnecting the TPS sensor. When I will install the MAP sensor, I will also edit the last row for 100% load. I will also edit the map some more after I drive a bit and see the normal points where the ignition stays (load/rpm) and consider that the basis of the tune. I have come up with this map, milder than the first one.

The Megajolt was not expensive at all, I think I paid around 50 bucks for the whole system, so from my point of view it is not a very expensive electronic distributor, but a real upgrade. All of my old ditributors (including electronic ones) did not work properly. All of them were SVDAs and I could not get a proper vacuum from the single vacuum port on one barrel of the carbs.

I read about vacuum canisters so I will make one out of a copper tube ~1" in diameter and 4" long, onto which I will solder 5mm copper pipes, 4 inputs and one output. I will drill and tap the intake manifolds to install quick-release pressure couplers. Hope this will work.
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'74 1303S, L98B Viperngrun (extra glitter), German Look
'64 1200, Sea Blue, under restoration

[clonebug]

You need to use your map sensor to measure load.
Doesn't megajolt come with a map sensor???
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[ps2375]

Piping vacuum from the 4 intake runners into a single vacuum log does not make a viable vacuum signal for the megajolt. It just makes a vacuum log that may or may not indicate actual load. You would be better off tapping into one half of the intake manifold at the base of the carb.

[Juanito84]

Here's what I suggest:

Get some paper and a pencil and draw out a spark table.

First figure out your no-load timing curve.
At idle advance the timing until you just reach your highest RPM and lowest MAP. Note the RPM and MAP and find that on your spark table and write in there your ignition advance. Open up the throttle a bit and leave it there somehow (vicegrips?) and play around with your timing to see where it just reaches the highest RPM and lowest MAP again, then write that down. Keep doing that until you have your lowest MAP curve figured out.

Next figure our your high load timing curve.
This only works with a naturally aspirated engine, and you need either a dyno or a good seat-o-pants meter. Set up a general spark table that only advances with RPM. Maybe start out a little retarded, maybe 25° max advance by about 3,500RPM, curving up from idle to there. Take your vehicle out on the road and floor it. Note how it feels. Also maybe make several signs and clock the car between the them with a lap style stop watch and note what general RPMs you have between which signs. Pull over and try a different spark curve, advancing it a little bit at a time, and try again. Listen carefully for any pinging. Keep going at it until you note any pinging or wherever it doesn't have any more acceleration than the previous try. Note the RPM where the pinging was noticed or you didn't feel any more acceleration and write that timing in your map, keeping it a few degrees less than where you noticed the pinging, if any, for safety. Keep fiddling with the other RPMs until you found the limits of the whole high load curve.

Figure out your middle load curves.
Take and do the same as with the high load curve, making a spark map that shows only advance with RPM, based off of your high load map, only that when you make changes to it, leave your high load (100kPa) curve alone.
with a vacuum gauge or other try a load just below floored (for an example, 90kPa). Do the same as you did with it floored only trying to keep your pedal closed just enough to produce the lower manifold pressure. Do this again and again, each time at a lower manifold pressure, until you have nearly all of your spark map filled. Note that at lower manifold pressures and loads it will be less likely to ping, but more likely to simply stop increasing in power. Whenever you can't notice any acceleration/power increase after increasing the timing at X RPM and X MAP then that's the timing you want there.

Of course all this would be easier on a dyno, because the dyno will tell you the precise amount of torque at any given RPM and MAP combination. With a dyno you'd mess with the timing at each RPM and MAP combination to see what timing gives you the best torque.

Figure out your idle.
Down in the low MAP low RPM area you can do it three ways, depending on how you want to do it. One way would be to just make all your numbers in that area flow down to your idle timing, so that it's the same at that RPM regardless of MAP. The other way would be to go off of what gives you your best torque, but have another way to switch to a fixed idle timing anytime you let off of the throttle completely. The advantage to that is that you'll get instant torque when you touch the pedal and yet better engine braking since you'll be running idle timing when engine braking. The third way would be to keep the best torque spark table, but adjust back the throttle in order to keep RPMs down. This will make it idle much cooler, but can make it hard to start, and idle in the cold.

Remember this is best to do after figuring out your AFR's. If you change your
AFR's you'll need to figure out your spark table all over again.
_________________
If a water cooled engine cools its water with air, isn't it just an overcomplicated air cooled engine?

[ps2375]

[Juanito84]

[clonebug]

If you have a single center mounted dual carb just drill the manifolds right under the throttle plate and tee them together.
Run a single line to the map sensor.
It should work that way.
If not then build a vacuum tank.

An engine will run on almost any ignition map.
It's up to you to feel how it runs and adjust fuel and advance accordingly to make it run the way you like it to.
You can feel it in the throttle pedal and also how much vacuum it pulls which will indicate you are getting it right.
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[Boolean]

[Boolean]

1. Your engine can probably breath much better than stock due to longer cam, better exhaust and better carburetion.
2. Better breathing would be a reason for going mild, not the inverse.
3. Going that mild on part load will emulate a 009'ish behaviour. If you want that just use a 009.
4. Do not emulate a distributor curve, your engine will not thank you.
5. Measure head temps, listen for detonation and clock accelleration between lighting posts at different loads.
I guess I should add that "He who measures, knows".
_________________
I strive for perfection. Excellence will not be tolerated!
Build thread here:
http://www.thesamba.com/vw/forum/viewtopic.php?t=529379

[tzepesh]

Thank you again for your feedback.
To clarify some points:

[jonboylaw]

I run a MJ with Vac signal take off from each manifold port just below the carb (M5 pipe connectors that are angled down into the manifold to avoid fuel mixture blowing into the vac tubes), these then go to a plenum chamber which feeds the MAP sensor in the MJ board via a single tube. This works relatively well so long as the plenum chamber is reasonable size (too small and you get the pulsing, too large and you get signal lag). I use some 1.25 in plastic pipe about 3 inches long with end cups to seal.

The Map you are running does not need to go all the way out to 5000RPM as the MJ will hold last settings, far better to get the 1500 - 3000 RPM curve better defined for a smoother (read more torque) up take and run the map up to say 3500 RPM.

You can also push the advance way up on the over run (high vacuum high revs) as this will be a lean condition (slow flame front).

Also put a soft limit in at 5200 RPM unless you are planning to rag it.

My map:

[ps2375]

[Juanito84]

[Boolean]

Cosworth is a small european firm that made a few race engines for a local series.
They attached a copper pipe, flattened in the end and secured with a bolt to the engine.
I guess the head close to the CC would be a good place on a VW.
The other end went through the dyno wall and ended with a stainless funnel of the kitchen variety. They measured torque only, and listened for detonation. Good enough for winning in F1 for several decades.
This is a cheap detonation speaker of sorts.
Could be attached to a moving car too, just remember to use one on each head.
_________________
I strive for perfection. Excellence will not be tolerated!
Build thread here:
http://www.thesamba.com/vw/forum/viewtopic.php?t=529379

[Juanito84]

[Juanito84]

[jonboylaw]

It really depends upon the application. For a racer then yes, mapping for max torque, pre-detonation is fine, however for a street car or bus I would dial it back a bit for a couple of reasons:
1) poor quality fuel, if mapped on decent fuel and you put a tank of lower quality fuel then you may get detonation and not be listening out for it
2) running on max advance will tend to make the engine run hot. Not what you want for a reliable street/bus engine.

The map I provided above is for a bus motor. Originally I had some higher mid range advance numbers but found that although not pinking, it was running hot.