Optimising ignition timing.
Turbo Mini Forums

I'm a hardware engineer and should be able to record and dump the inter-tooth timing for each tooth on a 36-1 crank sensor as the engine is accelerated WOT in neutral (with a hard rev limit set).

Looking at the timing you can then work out relative torque.

If the ignition timing was optimised using these measurements would this also be the optimal
timing for on the road WOT operation?



Nial.

No as the engine isn't loaded when stationary

NO!

WOT under no load is about as different as you can get as WOT under load.

The only real way to optimise ignition is to measure torque at a point and then alter ignition timing dynamically to achieve the max power. This means either an engine dyno or rolling road.

> The only real way to optimise ignition is to measure torque at a point and then alter ignition timing dynamically

If you treat the engine rotational mass as the load then the rate of change of speed is proportional to the torque.

I can easily measure the inter tooth timing to 10ns resolution, so can work out inter tooth acceleration, though this would need smoothed.


Or is it just the case that this doesn't work?

Nial.

Good luck is all I have to add.

As said you need it underload,

No, load as in driving the car normally or WOT depending on what you are doing.

What you are proposing, in theory at least, could work. After all that is what is done on a rolling road. The difference being that the load you are using is the engine not the rolling road.

In practice I can't see it being very effective. You will never get enough load to make boost. Plus you will be going through the rev range so quickly I doubt that you will be able to get any sensible data.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

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Edited by Nial on 10th Sep, 2013.

As Ben says, the theory sort of makes sense, assuming that you can properly calculate the rotational mass.

I think the problem you'll have is more practical. If I try and get WOT from idle on my car, it'll be half way up the rev range before I reach it. so at best you'll have WOT for a few thousand rpm.

I don't know the maths off hand, but such a low load and short measurement time will definately scew the results.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

im with the other chaps you need to place a constant load on the engine to keep it at WOT at a given rpm then you can walk the ignition timing back n forth until the peak power is reached at that rpm then you move on to the next rpm and repeat until you have a curve

The maths is sound but, as already said, totally impractical because the inertia of the engine by itself is so low.

If you are really, really brave, jack the front of the car off the ground, support it on something VERY solid under the lower suspension arms or ball joints (so the driveshafts are at the normal angle), fit the heaviest (and best balanced) wheels you have and run the engine up to speed in 4th gear.

The inertia will be a lot higher.

Obviously no-one and nothing in front of the car just in case....

The maths based on inertia alone will be complex and, if you add a bit of left foot brake (not too long or they overheat) you have the Old Skool home dyno. The maths is even harder then....


(EDIT - spelling)

Edited by Rod S on 11th Sep, 2013.

Schrödinger's cat - so which one am I ???

At best you can optimise timing for a car with the wheels off the ground or revving with WOT standing at the traffic lights (i.e. being a div) .

if you add load it will be all different.if you change from WOT to anything else it will be different.
don't forget that it is chemistry that drives the whole lot and heat/load will change everything.
The amount of timing you dial in (using any inertial method or inertial dyno if you just go for max power.. that is measured by acceleration.. i.e. dynojet), will probably kill the engine if you use it in anger for any sensible duration.

Edited by Sir Yun on 11th Sep, 2013.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

Thanks for the feedback guys.

I need to design/build an interface board to condition the output of the sensor to something and FPGA (programmable chip) can handle. I'm half way through that, when that's built it shouldn't take too long to see what sort of results I'm getting.

I suppose I can also try the same test with the car in 3rd or 4th on a flat bit of road, but with a bit more variability between runs.


I'll report back.

Nial.

If you do it on the road you will need to factor in air resistance. Should be quite easy to so on a calm day.

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.