Engine Mapping

[erny]

Please could someone with experience of ignition mapping answer the following questions.

1. Are knocking sensors needed? It seems logical that a power loss will be visible as knocking begins. Are there particular areas knocking is a problem?

2. I have looked at the PE ignition map and am a little confused with the numbers, it seems as the load increases the advance is increased. Should it not be the opposite? Does anyone know what the idle advance should be? The PE is as low as 5 degrees.

3. Does the restictor have any strange effect on timing?

Any help much appreciated

[C.Casper]

If you are looking at the "stock" map from the PE site, remember it is very conservative. It is intended to get the car to fire, this is my understanding. You can retard the timing some as the rpm/load rises but just be carefull as to how much you do it, at some point you run the risk of firing the engine too close to TDC that it will reach full combustion when the piston is already on its way down. Been running on 4hrs or so sleep a night, so this advice may be a little off. But i'm sure you'll get some response from a few more experianced FSAE engine guys than myself. good luck

[erny]

The map im looking at is the cbr 600 with restrictor map.

[EfiOz]

1. You don't need knock sensors or det cans. Just a good dyno and a bit of time.If you've got to the point of knock, then you're way past MBT on most engines.

2. Timing is usually at a minimum at max. torque. Timing at idle should be just enough for the engine to idle and run it's ancillaries, usually in the 5-15 deg range.

3.Yes. You will find they will take a lot more as rpm rises and VE drops like a stone.

[B Lewis @ PE Engine Management]

Originally posted by erny:
Please could someone with experience of ignition mapping answer the following questions.

1. Are knocking sensors needed? It seems logical that a power loss will be visible as knocking begins. Are there particular areas knocking is a problem?

2. I have looked at the PE ignition map and am a little confused with the numbers, it seems as the load increases the advance is increased. Should it not be the opposite? Does anyone know what the idle advance should be? The PE is as low as 5 degrees.

3. Does the restictor have any strange effect on timing?

Any help much appreciated


Hi erny,

Knock sensors are not needed. With the restriction in place and the amount of overlap in the cam timing, these engines are virtually impossible to get to knock when running N/A. If you run too much advance, torque will just fall off.

As someone already posted, the maps that we have on the website are just conservative examples to get you going. You should plan on tuning the engine for maximum torque by varying the ignition timing at steady state load sites within the table. This is best done after the fuel table is pretty close to final form.

Good luck!!

[EfiOz]

I'll apologise now as I feel the need to post this, but that must be the worst tuning advice I have ever heard.

[Bill Kunst]

Excellent EfiOz,

Since you think this is bad advice, please give your advice. I imagine that you must know something that I don't, or maybe that PE doesn't. Otherwise, keep replies like this to a minimum. It is a directed insult with no material to back it up.

Waiting for the right way to tune,
Bill Kunst

[BeaverGuy]

There was a post between Brian's and EfiOz's that I believe he was referring too. However, it seems to have gone missing.

[Bill Kunst]

well then,
Sorry if this is the case-
Bill

[57JoeFoMoPar]

Idle advance for our map is a little high, around 20 degrees, but idle speed is set to 3500-4000 to keep the motor closer to it's intended power band. 10 degrees at a normal (stock) idle would be between 10-15 degrees.

As mentioned, a knock sensor is not necessary, and in many cases, may not even work at all.

It is impossible to tell off the cuff what the advance should be. Best way to tune is to get the car on the dyno and make pull after pull. It took us about 40 pulls after initial rough (seat of the pants)tuning to be happy with the results. The way we tuned was to first get a rough ignition table, then make adjustments to the AFRs to keep them constant. We shot for 12.5:1. Once the AFR was fairly constant, then we started messing with ignition advance. If I'm not mistaken, we made our best power with 40-46 degrees at the top end.

Other factors will greatly affect your ignition table. Fuel octane, compression ratio...all need to be considered,

When you dyno tune, be sure to tune or adjust for elevation changes

[EfiOz]

What happened to that post?