Can the settings be wrong, but the timing sync?

ochizon · Post by **ochizon** » Wed Aug 16, 2006 9:22 pm

I just got my truck's ignition running under MSNS-E control (yay!), and snyced up the timing. On a 36 - 2 wheel, running a dizzy, I came up with

trigger 1- tooth 7

trigger 2- tooth 25

trigger angle - 70 degrees

With these settings, the timing synced up, but when driving the car, something is off, and I dont think its the timing map so much as an error of mine in the above setup.

To simplify, what I want to know is can you have more than one trigger/trigger angle combo that will seem to give properly synced timing, but only one that is actually correct? Or is there only one setting that will sync up?

Post by **jsmcortina** » Thu Aug 17, 2006 2:23 am

All the wheel needs is the missing tooth to get sync and correctly spaced trigger numbers to get stable rpm. However the timing can be TOTALLY WRONG !

It is very important to confirm timing with a strobe.

James

ochizon · Post by **ochizon** » Thu Aug 17, 2006 4:44 am

jsmcortina wrote:All the wheel needs is the missing tooth to get sync and correctly spaced trigger numbers to get stable rpm. However the timing can be TOTALLY WRONG !

It is very important to confirm timing with a strobe.

James

In my previous post when I wrote that I got it to sync, I meant with a timing strobe. I just wonder if there are settings that will sync up with a strobe, and yet not be the right settings, since I got it to sync with a strobe but feel that its not right. I ask so that if there is ONLY ONE way to get it to sync, then I know I have this part done correctly, and need to look elsewhere to solve my issues.

Honestly, I am failing to understand clearly the relationship between the trigger points, and the trigger angle. I can see that they are integrally related, but I am not sure what the relation needs to be.

ares650 · Post by **ares650** » Thu Aug 17, 2006 4:45 am

Well with a timing light, the base time is right. But the car feels lazy.

Post by **jsmcortina** » Thu Aug 17, 2006 5:47 am

Sync means the software has read the wheel and is giving rpm.

If you mean that you verified the indicated timing in Megatune matches the actual timing at the crank then that is good. Check over various rpms and advances and make sure it always matches. Once you have that sorted it is a case of tuning.
The base spark table provided is intended to be "lame" and fairly safe.

With your trigger A at tooth no. 7 you are saying to the code "when you reach tooth no. 7 you are at 70 BTDC for (that) cylinder"
Likewise with your trigger A at tooth no. 25 you are saying to the code "when you reach tooth no. 25 you are at 70 BTDC for (that) cylinder"

James

ochizon · Post by **ochizon** » Thu Aug 17, 2006 7:41 am

jsmcortina wrote: With your trigger A at tooth no. 7 you are saying to the code "when you reach tooth no. 7 you are at 70 BTDC for (that) cylinder"
Likewise with your trigger A at tooth no. 25 you are saying to the code "when you reach tooth no. 25 you are at 70 BTDC for (that) cylinder"

James

ok, you may be helping me get somewhere here.

you say when I set trigger A to tooth 7, I am telling the code "70 BTDC?"

I thought I was telling the code "you are at TDC now"

in real terms, so that you know, my tooth seven is what is sitting in front of the VR sensor when the engine is at TDC.

CAn you tell that I am a bit lost? hahaha

Post by **jsmcortina** » Thu Aug 17, 2006 8:19 am

ochizon wrote:you say when I set trigger A to tooth 7, I am telling the code "70 BTDC?"

Yes, it uses 70BTDC because that is the number you entered in Trigger Angle.

What happens is the code counts the teeth until the tooth number matches the numbers you entered. Then it goes to the normal ignition code (as if it got a signal from a dizzy) it uses the number you enter into the trigger angle as the current position and works out the delay to the spark.

Is this really a 36-2? If it is the common 36-1 then try using trigger A = 1, trigger B = 19 and trigger angle = 60.

IF it is a 36-2 then try using trigger A = 2, trigger B = 20 and trigger angle = 50.

James

ochizon · Post by **ochizon** » Thu Aug 17, 2006 9:21 am

so its trigger point + trigger angle = actual spark event????

and yes, its a 36-2

and THANK YOU, I think I am understanding now

Post by **jsmcortina** » Thu Aug 17, 2006 9:36 am

When the code receives a trigger it calculates a delay. The delay calculation doesn't know anything about trigger teeth, it just knows that it got a trigger.

If the commanded advance was say 14 deg and you had a 60 deg trigger angle it will work out that the delay needs to be 60-14 = 46 degrees.
It then works out how long in microseconds 46 degrees is and sets the delay timer for the spark.

If you set a 50 deg trigger angle it would wait 36 degrees.

James

ochizon · Post by **ochizon** » Thu Aug 17, 2006 11:38 am

OMG I FINALLY GET IT!!!!! ITS SIMPLE!!!!!!!

the trigger angle is the headreoom for max advance AFTER the trigger signals!!!

So with a trigger angle of 50 degrees, I can run advance upto 49 degrees, one degree after the trigger.

If I were to sete the triggers at 1 and 19, I could set the trigger angle to 60 degrees. At 3 and 21, 40 degrees...

minor adjments are made to the trigger angle to get proper timing with the strobe.

I was noticing a wierd timing because I was probably severely out of phase with my settings....

I CANT WAIT TO GET TO MY TRUCK!!!!!

Post by **jsmcortina** » Thu Aug 17, 2006 12:55 pm

Yes, that's it. However a few points. With a -2 wheel you cannot use teeth 0 or 1. You need to allow about 10 degrees after the trigger angle to max advance. So 50deg trigger would give 40deg max advance (not enough for most people.)

You might want to use tooth no.35 as trigger A with an 80deg trigger angle.

James

ares650 · Post by **ares650** » Fri Aug 18, 2006 8:17 am

http://www.msefi.com/viewtopic.php?t=21665

the weird part is that it won't start with 2-20 trig 50.

ochizon · Post by **ochizon** » Fri Aug 18, 2006 8:19 am

ares650 wrote:http://www.msefi.com/viewtopic.php?t=21665

the weird part is that it won't start with 2-20 trig 50.

I am conviced that we have our initial measurement wrong. James gave his suggestion based on my comment that the tooth 7 is under the VR @tdc. That must be incorrect.