the theory if ingnition mapping ?

[germanz]

Hello,

 

is there any information about the theory of ignition advance map ?

 

 

Here is my project.

 

L24 wit 10:1 compression + valve job

290 degree cam

Triple weber (45)

Megajolt with Edis 6 (with MAP)

 

 

Question are:

- total advance ?

- influence of fuel mixture

- influence of load ?

- what is ideal for idle ?

- what is ideal starting the engine ?

 

 

Probably I can convert a megasquirt map. I've found a lot of information here http://forums.hybridz.org/showthread.php?t=113165

 

Many Thanks in advance

 

Rainer from Germany

[RTz]

is there any information about the theory of ignition advance map ?

 

There is plenty of opinion and theory on the topic. Volumes have been written.

 

Here's a starting guide...

 

Bottom line, give the engine what it likes.

 

On a dyno, most modern unmodified engines will reach mean best torque (MBT) before they begin detonating. At that point, adding more advance is useless (and more stressful), and power will begin to fall. Eventually detonation will set in. However, some engines are detonation limited and some timing value below that threshold will typically produce MBT. If you find more torque beyond detonation, its an indication that only a portion of the cylinders are detonating, but its still 'unsafe'. Give the engine what it likes.

 

At idle, good timing will generate good vacuum. Give it what it likes.

 

Fuel mixture effects the rate of burn, so it can have an influence on 'optimal' timing. Dyno will show MBT. Give it what it likes.

 

Lighter loads decrease the dynamic comp. ratio, causing a slower burn rate. More advance will prove 'better' with light loads. Fuel economy, response, and a dyno will help guide you with this. Give it what it likes.

 

Many engines will start anywhere between 0 and 20 degrees. Again, give it what it likes... you'll know.

 

You will usually find that there is a 'window' of MBT over several degrees of timing. Choose the lesser advance. In fact, slightly 'under' the window, with a slightly richer mixture often produces very similar MBT, with less stress.

 

Never run more advance than required to get you to MBT or knock threshold.

 

Tune. Tune. Tune... and don't forget to give it what it likes.

[germanz]

Many Thanks for your advise Ron,

 

O.k the dyno will give clearness. Unfortunately my weber have to be tuned in the same time.

 

But I'm still interested in maps from other non turbo project.

 

Cheers

Rainer

[Chemicalblue]

There is plenty of opinion and theory on the topic. Volumes have been written.

 

Here's a starting guide...

 

Bottom line, give the engine what it likes.

 

On a dyno, most modern unmodified engines will reach mean best torque (MBT) before they begin detonating. At that point, adding more advance is useless (and more stressful), and power will begin to fall. Eventually detonation will set in. However, some engines are detonation limited and some timing value below that threshold will typically produce MBT. If you find more torque beyond detonation, its an indication that only a portion of the cylinders are detonating, but its still 'unsafe'. Give the engine what it likes.

 

At idle, good timing will generate good vacuum. Give it what it likes.

 

Fuel mixture effects the rate of burn, so it can have an influence on 'optimal' timing. Dyno will show MBT. Give it what it likes.

 

Lighter loads decrease the dynamic comp. ratio, causing a slower burn rate. More advance will prove 'better' with light loads. Fuel economy, response, and a dyno will help guide you with this. Give it what it likes.

 

Many engines will start anywhere between 0 and 20 degrees. Again, give it what it likes... you'll know.

 

You will usually find that there is a 'window' of MBT over several degrees of timing. Choose the lesser advance. In fact, slightly 'under' the window, with a slightly richer mixture often produces very similar MBT, with less stress.

 

Never run more advance than required to get you to MBT or knock threshold.

 

Tune. Tune. Tune... and don't forget to give it what it likes.

 

 

 

I should get T-shirts made that say "Give it what it likes":lmao:

[MONZTER]

Maybe this thread will help. Some of us posted our Tec 3 tables. My car is also a L-24, but my head is pretty modified so my timing might seem a little less than most. http://forums.hybridz.org/showthread.php?t=122406

 

Best Regards

 

Jeff

[germanz]

Hello Jeff,

 

 

Many thanks, my haed looks not that differen't.

 

Does it mean that I have to add 15 degree to each value in that table ?

 

45 degree advance sounds quite high.

 

http://album.hybridz.org/showphoto.php?photo=14997

 

 

Cheers

Rainer

[MONZTER]

Hi Rainer,

Those are my actual timing numbers per RPM and MAP points. The head has small 36cc chambers so the burn is very fast. A few degrees is probably need to be added for a stock N-42 head

[RTz]

Rainer,

 

A general rule of thumb... better chambers require less advance to reach MBT.

 

The factory (L-series) chambers are not terribly impressive... so they respond well to more advance than a modern engine. On the other hand, Monzters chambers are a thing of beauty. That is largely, if not entirely, why his timing numbers are modest.

 

On a bone stock 8.3:1 L-series, total timing will probably be in the 38-40 degree range (on premium US fuel). You have more compression and different gas... you will likely find different results.

 

Any map you use/copy should be thought of only as a start point. You must test & tune.

[germanz]

Thanks for all your help,

 

I have no experience with megaquirt. But how to read Jeff's Map ?

Do I have to add the 15 degree initial advance ?Or what does it mean.

 

Cheers

Rainer

 

[MONZTER]

Rainer,

Ignore the initial advance number, that is for start-up only. Just look at the numbers on the chart. Also, please remember what Ron said, every configuration and every car will be different. Please use the chart as a reference only.

 

Best regards

 

Jeff