As some of you know I am tuning my MS2/Extra computer to run with my 2F. I need to program the computer with an advance that is somewhat accurate. I know that it is supposed to be at 7 degrees at 650 RPM. After that I have no clue where to go. Anybody know what that curve should look like? 3 or 4 points would allow me to get a curve.
Ignition Advance Curve?
- Thread starter joeyg1973
- Start date
This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.
not really sure what kind of module the ms2 is. I assume you've put in an electronic distributor or a kit, but what kind of dizzy is it? Sounds like you've got the install worked out, just need to program some points for a typical curve into the module. So you need 3 points including idle or past idle. If some one w/ an advance light and a stock engine/ ignition were to just get some advance points and referenced rpms for each point, would that help?
- Thread starter
- #4
The MS2/extra (MegaSquirt2/Extra) is a complete fuel and ignition computer. MegaSquirt - Wikipedia, the free encyclopedia. I am directly firing a 6 pack wasted spark ignition module from the MS2/Extra using the feedback from a 3fe for telling the computer where the crank and cam are. Follow the link to my build up and skip to the end where there are youtube videos where I at least try to explain the whole thing.
I got a bead on a getting the curve and it is exactly what you suggested. I am going to take my digital timing light to a friends 2f and figure out what the advance is at various RPMs. Granted it isn't stock ignition as he has some aftermarket module on it, but it should be close enough of a base for me to tune off of. Still I wouldn't be adverse to someone else doing this as well for a comparison.
I would say you could safely run up to about 36 degrees max, more if you were real careful...
the issue is making it a 3D curve with the map sensor.
so, lets say 7 degrees at idle
full advance by 2500?
the issue is making it a 3D curve with the map sensor.
so, lets say 7 degrees at idle
full advance by 2500?
More:
I think a great place to start reading on EFI timing control is the '7747 timing only white paper that is floating around. I know, megasquirt isnt the GM ECM, but it should give a good albeit somehwat too comprehensive look into timing.
My guess is that you are using this as the max allowed timing curve? If so, you are falling short of what EFI can offer by setting it at a carb distributors timing parameters, but as a start this will be a good guideline.
I think a great place to start reading on EFI timing control is the '7747 timing only white paper that is floating around. I know, megasquirt isnt the GM ECM, but it should give a good albeit somehwat too comprehensive look into timing.
My guess is that you are using this as the max allowed timing curve? If so, you are falling short of what EFI can offer by setting it at a carb distributors timing parameters, but as a start this will be a good guideline.
I run my 2f at around 4 or 5 degrees initial timing, going to about 39-40 max. My curve is very aggressive..I would imagine I am at 40 degrees around 3000 rpm and on up. I run an HEI distributor with the weakest springs available and the fly-weights were cut for more total available advance. The low initial timing makes for easy starting makes the engine very hard to stall, and the rapid advance gives great throttle response. I can take some actual reading on Sunday if you need them.
- Thread starter
- #8
36 degrees is what I thought as well but didn't think that I would need to be at full advance at 2500. That's an interesting point.
As far as creating the 3D curve with the map sensor, it is difficult to do as I don't have a way to put a load on the engine while it is on my engine test stand. Not knowing what the curve should be under load is the reason I made sure to get a knock sensor. So I can be a bit aggressive on my timing under load when I get it in the truck and the computer will automagically turn back the timing as it senses a knock. If I notice a lot of knocking, it will be recorded and I will know the kpa and rpm I need to reduce the timing at.
This is the reason I started a thread on giant heavy flywheels on the cheap. I wanted to be able to put a load on the engine to see all this data and tune everything on the test stand.
Last edited:
- Thread starter
- #9
The more readings I get the more insight it will give me on the curve. I will take you up on your offer to get them Sunday.
- Thread starter
- #10
I will look around for that white paper.
I am going to use the 2D timing curve as a starting point. Basically I am going to start by putting those values into the 3D map at the appropriate point in RPM and kpa at no load. Then estamaguess things out from there.
What I was really surprised at is how much vacuum a 2f creates at idle of 650. I have between 39 and 40 kpa at idle.
- Thread starter
- #11
Brett, you really think full advance by 2500? Why is that? I am lacking experience in this area and brief explanation would be nice.
I need to get the numbers off my friends truck tomorrow... The dist hold down clamp was rusted solid so we needed to cut it off. I am just going to give him my old dist after I dig it up and head back up there.
- Thread starter
- #12
Well here is what I got from a 2f with the distributor that has the adjustable advance and retard dial on it. The dial was set to neutral.
650 @ 7.0
1000 @ 15.8
1500 @ 26.7
2000 @ 33.8
2500 @ 37.3
3000 @ 42.7
3500 @ 47.9
Yeah I know... surprised me too. Showed someone that is an engineer at Toyota who is on our local club and he told me that there is no way it would be that high. He said that it had to be my gun. Somehow I doubt that. He also said that the springs must be worn out then... but over 3000 with that high an advance, there was no pinging at all.
All readings were taken from the BB so whatever number I got on the gun, I added 7. I couldn't see the TDC mark on his flywheel.
I really want to see what others have for numbers now.
650 @ 7.0
1000 @ 15.8
1500 @ 26.7
2000 @ 33.8
2500 @ 37.3
3000 @ 42.7
3500 @ 47.9
Yeah I know... surprised me too. Showed someone that is an engineer at Toyota who is on our local club and he told me that there is no way it would be that high. He said that it had to be my gun. Somehow I doubt that. He also said that the springs must be worn out then... but over 3000 with that high an advance, there was no pinging at all.
All readings were taken from the BB so whatever number I got on the gun, I added 7. I couldn't see the TDC mark on his flywheel.
I really want to see what others have for numbers now.
- Thread starter
- #13
This is what I wound up with for now as my ign table based off of the numbers that I got. When I get more on Sunday from Killerpea or from anybody else I will incorporate it. I can't adjust for load yet because I don't have any. I did try to use the 3000 @ 42.7 and 3500 @ 47.9. and even though I didn't hear a knock, the knock sensor went off steady solid around 3700. I took it back to what you currently see and at the same rpm the knock sensor didn't go off. What's interesting is that according to my log, at 3167 rpm you can run 44.4 degrees advance on 87 octane with no load (MAP at 36.9 kpa) but after that the knock sensor goes off. Granted at that RPM it could be just engine noise setting off the knock sensor, but I would rather be safe than sorry and not have advance go that high with no load.
I really need to figure out a way to put a load on this thing on the test stand so I can research this more.
I really need to figure out a way to put a load on this thing on the test stand so I can research this more.
- Joined
- Sep 26, 2003
- Threads
- 117
- Messages
- 11,199
- Location
- Lancaster, Ohio, USA
- Website
- www.tlcperformance.com
Random recommendations:
Start w/ base timing of 10*.
Do not use timing for idle speed stabilization. It does not work well on a trail rig. Use an IAC for that.
Do not bring on too much timing too soon. The engine makes peak torque @2000, so cylinder pressure is highest, so flame speed is highest. Mild advance until past 2000, then a little more, but not too much because there is a second tork peak @2600, then bring on the advance after 3000.
Above 3000, piston speed is getting high, and the engine is starving for air, so cylinder pressure falls way off, so much more advance can be used all the way thru 4000.
HTH
Start w/ base timing of 10*.
Do not use timing for idle speed stabilization. It does not work well on a trail rig. Use an IAC for that.
Do not bring on too much timing too soon. The engine makes peak torque @2000, so cylinder pressure is highest, so flame speed is highest. Mild advance until past 2000, then a little more, but not too much because there is a second tork peak @2600, then bring on the advance after 3000.
Above 3000, piston speed is getting high, and the engine is starving for air, so cylinder pressure falls way off, so much more advance can be used all the way thru 4000.
HTH
- Thread starter
- #15
Good advice. I am not just using spark for idle control. I am using the IAC for idle control based on closed loop feedback from the WBO2 and MAP. Looking at my current map in my last post Jim, what would you change/adjust on it? Bring the advance down to say 20 at 2000 and then 25 at 2600 and then all in at 3000?
Joeyg:
I have timing advance numbers for two distributors I have used in my '75 2F.
With the stock distributor I get:
10 deg @ 620 rpm
15 deg @ 1600 rpm
20 deg @ 1900 rpm
25 deg @ 2100 rpm
27 deg @ 2400 rpm
I replaced that distributor with an HEI unit and I get:
10 @ 660
13 @ 900
18 @ 1200
23 @ 1500
28 @ 1700
33 @ 2100
38 @ 2900
Like you I measured this with a timing light and tach - no load. Runs much better with the HEI distributor. However I think the HEI advance curve is somewhat arbitrary and I consider it a starting point. Let's get some more timing light and tach tests posted.
Mark
I have timing advance numbers for two distributors I have used in my '75 2F.
With the stock distributor I get:
10 deg @ 620 rpm
15 deg @ 1600 rpm
20 deg @ 1900 rpm
25 deg @ 2100 rpm
27 deg @ 2400 rpm
I replaced that distributor with an HEI unit and I get:
10 @ 660
13 @ 900
18 @ 1200
23 @ 1500
28 @ 1700
33 @ 2100
38 @ 2900
Like you I measured this with a timing light and tach - no load. Runs much better with the HEI distributor. However I think the HEI advance curve is somewhat arbitrary and I consider it a starting point. Let's get some more timing light and tach tests posted.
Mark
- Thread starter
- #18
On the stock one, it doesn't go further than 27 degrees at higher RPMS?
I have those numbers in a different file - when I checked them there I see I made a mistake somewhere. Please disregard the previous values for the stock distributor and use the following instead. It does continue to advance but not as far as your friends.
11 @ 580
15 @ 1000
20 @ 1500
25 @ 2000
30 @ 4100
35 @ 5750
11 @ 580
15 @ 1000
20 @ 1500
25 @ 2000
30 @ 4100
35 @ 5750
- Joined
- Sep 26, 2003
- Threads
- 117
- Messages
- 11,199
- Location
- Lancaster, Ohio, USA
- Website
- www.tlcperformance.com
It looks like idle timing is being used for idle stabilization.
Timing value should be steady state below 750RPM, w/ target idle of ~600.
Advance should continue out through 3500-4000.
What is SCR?
What is DCR?
What is head casting number?