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Discussion Starter #1 (Edited)


So I'm going through various settings in Crome trying to build a tune and not blow up another engine. I'm at work and don't have access to my previous tune to post pictures but I felt it was a relatively conservative tune to start with. I didn't have a knock sensor at the time and of course I experienced detonation and blew the ring lands on all the pistons. Huh...

So I come across the Base Ignition Table settings under Advanced Settings and I feel extremely stupid for overlooking it. Is this real? Is the entire ignition map being advanced based on RPM? Why in the hell would I want to do that? I spent time retarding timing under various boost pressures and IAT only to have this be a variable? Also, why would I want to advance timing based solely on RPM? I need some insight on this table because from my perspective, this seems completely stupid to simply advance timing wildly like this based solely on RPM. Any advice would be greatly appreciated.
 

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Discussion Starter #3
from what i remember it should be that you add more timing as the rpms go up to give the fuel time to burn.

i.e the faster the pistons are moving the faster the fuel needs to burn. So adding timing will help in even burn.
Yeah... but that should be built into your timing table, correct? To me it doesn't make sense to set a static timing table, tune your compensating variables, and then add an arbitrary ignition advance based solely on RPM. Again, your advance should be predetermined in the table and offset for boost, IAT, and ECT. What am I missing here that makes this ignition table useful?
 

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From what I've read it's a dwell correction table.

Messing with it does more harm then good.

Just adjust timing tables to mean brake torque without knock and be done.
 

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Discussion Starter #5
I had a friend put it to me this way:

This is due to the flame front propagation speed not changing throughout the rpm range while the speed of the piston does.

That makes more sense.
 

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()*#$(*$
93 Legend L Coupe.
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I eliminate all the advance in that table. It works on stock engines with stock parts and stock timing belts. (The leading conjecture is this is compensating for timing belt stretch at higher RPMs.)

If you move away from a stock engine, this table is worse than useless. I set all values to zero and tune the table, so there is nothing going on outside of the table aside from any other corrections (like your temperature corrections).
 

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the artist formerly known as drexelstudent11
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I eliminate all the advance in that table. It works on stock engines with stock parts and stock timing belts. (The leading conjecture is this is compensating for timing belt stretch at higher RPMs.)

If you move away from a stock engine, this table is worse than useless. I set all values to zero and tune the table, so there is nothing going on outside of the table aside from any other corrections (like your temperature corrections).
I always thought it was for keeping coil charge time constant while time between sparks decreased
 

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It's because the ecu sees the tic mark of the dizzy after much time has passed from it's event, even more as rpm increases, plus the icm and coil delay from ignition signal ending
 

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If you lock timing and point a timing light at the crank you will see that it will move at higher RPM. You use this table to offset that and keep it bang on. It's a two man operation.

Zero out the table first. Start the car and let it warm up. Lock timing at, say, 16 degrees. Have a buddy with a timing light verify that it matches the marks. Then bring it to 2000 rpm, 3000 rpm, and so on right to redline. Have your buddy signal if you need to increase or decrease timing to make it match up again.

It's called "crank trigger offset" and other things depending on what EMS you use.

It's ok to leave it zeroed and tune around it but I prefer to have the EMS do what it says it's doing.
 

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Discussion Starter #10
I set all values to zero and tune the table, so there is nothing going on outside of the table aside from any other corrections (like your temperature corrections).
Thanks. That sort of validates what I plan on doing.
 

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Discussion Starter #12
I see what you mean through reading that thread. My question is, if it's modifying ignition dwell, why not actually give the user a table to modify the dwell? I mean according to this graph I would be changing global spark over a given RPM range, not necessarily changing dwell time. I suppose what is said to happen and what is actually happening do not appear to be the same thing according to this tool in Crome.

Zero out the table first. Start the car and let it warm up. Lock timing at, say, 16 degrees. Have a buddy with a timing light verify that it matches the marks. Then bring it to 2000 rpm, 3000 rpm, and so on right to redline. Have your buddy signal if you need to increase or decrease timing to make it match up again.

It's called "crank trigger offset" and other things depending on what EMS you use.

It's ok to leave it zeroed and tune around it but I prefer to have the EMS do what it says it's doing.
I suppose this would be a good way to verify and modify that table to do EXACTLY what it says it's doing, rather than leaving it alone or zeroing it out.
 
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