Timing Explain???

[GST4g63T]

Ok, I'm one of those guys who likes to know just about every detail of any component, don't get mad it just helps me understand. My question is, how EXACTLY does the ecu control timing? I'm pretty sure on the 1st g's it has something to do with the cas? I have read on how to set basic timing but still ... I'm kinda lost. I would like an explanation on both generations, if it is at all different, which I assume it is.

I don't post much cause I pretty much just read and try to gain all the knowledge I can. I have searched and I can't quite find what I'm looking for, if I did miss a thread just link me up and ill be happy. Thx in advance.

 

[tenn-gsx]

Ok simple version is this. The cas has notches on a disk inside it. These notches are seen by the sensor inside the cas body. One notch is bigger than the rest and represents #1 cyl top dead center. The amount of time between notches tells the ecu how fast the engine is rotating and what cylinder is on the compression stroke. Based off of rpm boost and engine load (Engine load and boost are figured by the engine speed and several other sensors) the ecu advances or retards the timing pulse to the cylinders.


This is the basic generic explanation. The DSM cas may be more advanced im not sure. I just want to make it simple.

 

[thector1]

Yea, I'm sub. to this one. I also want to know

 

[GST4g63T]

Ok simple version is this. The cas has notches on a disk inside it. These notches are seen by the sensor inside the cas body. One notch is bigger than the rest and represents #1 cyl top dead center. The amount of time between notches tells the ecu how fast the engine is rotating and what cylinder is on the compression stroke. Based off of rpm boost and engine load (Engine load and boost are figured by the engine speed and several other sensors) the ecu advances or retards the timing pulse to the cylinders.


This is the basic generic explanation. The DSM cas may be more advanced im not sure. I just want to make it simple.

Now when u say timing pulse, this is what I don't understand, what's ecu actually doing to make u lose/gain HP? I have a good understanding about cams and how adjusting those to advance timing, but I'm just lost at how the ecu does it. Like when someone says " 30psi with 14* degrees of timing" I know what there talkin about but I have no clue what's actually going on inside the motor, if that makes any sense.

 

[MrBoxx]

When people talk about how much timing they're running, especially in regards to our cars, they're referring to ignition timing, the point in the combustion cycle at which the spark plug fires. There is an optimal time for the spark plug to fire. Too early and there's not enough compression. Too late and the piston is already moving in the wrong direction. Generally, the more advanced the timing is (to a certain point) the more power the car will make.

 

[bsbllfit7]

its delaying or advancing the time that it actually takes on that stroke for the ignition to spark and ignite. More advanced timing yields higher horsepower and torque but lower timing spools the turbo quicker. Ideally you want as high of timing as possible but limitations in your build as well as your fuel bring those numbers down. Mechanical gear timing is just changing when certain valves are open compared to the stroke, engine timing which the ECU controls controls the ignition and when it releases the spark. Does that help at all?

boxx got to it right before i did!

 

[tenn-gsx]

Ahh haa. You understand what top dead center is dont you? Well if not Ill explain. TDC 0* is the top of the piston stroke.(the highest point the piston reaches before it heads back down) So 14* timing is having the spark ignite the fuel when the crank is 14* before that piston gets to the top of the cylinder. Make sense now?

Way to take my thunder BOXX

 

[MrBoxx]

Team effort, Tennessee (who's really from Kentucky, apparently.)

 

[GST4g63T]

When people talk about how much timing they're running, especially in regards to our cars, they're referring to ignition timing, the point in the combustion cycle at which the spark plug fires. There is an optimal time for the spark plug to fire. Too early and there's not enough compression. Too late and the piston is already moving in the wrong direction. Generally, the more advanced the timing is (to a certain point) the more power the car will make.

This makes a lot of sense. So basically when the engine retards timing, its just slowing the spark to a less optimal time to fire, which I would assume is when the piston is already traveling down.

O wow, I'm on my phone sorry for my delayed responses.

 

[tenn-gsx]

^^^^ Yes and no. Optimum timing is variable. Boost, type of fuel, air charge temp, and rpm all affect what the optimal timing will be at any time. So what the ECU attempts to do is find a balance between optimal for power and optimal for safe.

Team effort, Tennessee (who's really from Kentucky, apparently.)

I was living in tenn when I made my account.

 

[fwbt]

By controlling the timing I believe he's referring to the timing tables that are built directly into the ECU itself. For a 1G, they are programmed directly into the ECU. Hence why DSMlink allows you to control these via Direct Access. How that works is the ECU determines load off several feedback sensors from the engine (ie TPS) and then determines RPM. There's a table that correlates the data from these inputs and then determines the amount of time the spark is adavanced. Other factors that affect it would be knock in which case the ECU retards the timing a preset amount until knock is gone.

 

[GST4g63T]

Ahh haa. You understand what top dead center is dont you? Well if not Ill explain. TDC 0* is the top of the piston stroke.(the highest point the piston reaches before it heads back down) So 14* timing is having the spark ignite the fuel when the crank is 14* before that piston gets to the top of the cylinder. Make sense now?

Way to take my thunder BOXX

That puts the nail in the coffin, I get it. Thank you all.

 

[MrBoxx]

Yes, pretty much.

We think of the combustion process as a pretty instant thing, but if you put it in slow-motion, you see the piston rising, then the spark. But the piston doesn't stop moving; it keeps going up, compressing the air/fuel mixture. The spark turns into a flame front, which is moving down. At some point they meet and the force of the flame front (the combustion) starts to push the piston down. If it happens too early, the flame front expends a lot of energy fighting the inertia of the upcoming piston. Too late, and the energy is wasted on an already-moving-down piston. But the rate of travel that the flame front experiences changes with density of the air/fuel mixture (boost) and the amount of fuel and air combustible mixture (A/F ratio). So these things change the timing curve of the engine as it goes through the rpm range.

Things like DSMLink and other ECU tuners allow you to change the timing curve manually, which is why they usually come with warnings that making changes when you don't know what you're doing can cause your engine to blow up.

 

[DSM1G90]

Dang, miss ol' vacuum advanced disributors and setting points .. and no computers to be in charge of it all...

With a dwell meter and vacuum gauge, one can really fine tune your timing settings down to exactly was you wanted and needed for maximum performance.

Nowdays, with the ECU being in charge of the whole smeer - communicating with sensors to get the A/F ratios just right to get the spark out at the right moment (why of the waste spark system - rather simple process you'd might say due to no moving parts, with two plugs firing at the same time, just the one plug is firing positive and the other is firing negative and each pair is firing 180* apart).

But, getting your base timing down to the degree really helps to start out where you want to go.

 

[bsbllfit7]

those certain reasons are also why we are able to get ridiculous amounts of power out of such small engines. Ever seen a 500 horsepower muscle car get 27 mph? The sensors help us to fine tune everything so well that we maximize fuel economy performance and sometimes reliability.

Sent from my PG86100 using Tapatalk

 

[Calan]

Ever seen a 500 horsepower muscle car get 27 mph?

Once or twice.

 

[bsbllfit7]

haha whoops! MPG! Nice call out