Ignition Timing

[johnl]

I asked my tuner and he said the diagnostic port is jumped in order to tell the ECU to always fire at the specified degrees. In the case of the F22A, that's 15*.

Thinking on this:

If the diagnostic port is "jumped", then at idle the ECU will fire at 15° BTDC, if the base timing is set at 15° (or at X° if the base timing is X&#176. If the port isn't jumped then the ECU will time the spark at some other Y°, which implies the ECU is in fact changing the timing (which must be in response to other inputs to the ECU). If this were not the case then it wouldn't be necessary to jump the port to get a correct base timing, you could just do it regardless...

The ECU has no way of 'knowing' what the base timing actually is, it's always going to 'assume' that it's 15°, and will adjust the timing at any given time according to other parameters with the assumed 15° (idle timing) as it's base line starting point (rightly or wrongly). If base timing is in fact X°, then the timing will be off at all times by the difference between 15° and X°, possibly slightly adjusted according to other inputs. This may conflict slightly with one of my earlier statements, but I think it must be correct.

The way it works is not really by the sensors but set to be a bit retard at low RPM and increasingly gain advancement as RPM's increase by default. With a knock sensor its slightly different as gathering data to configure the ignition timing is the sole purpose of a knock sensor.

Without a knock sensor then the stock spark timing may well be at least a bit retarded across the whole map than it really needs to be. Far safer that way if there is no knock sensor to catch a problem before it gets serious.

I doubt knock sensors are really one of the sensors used to set normal timing in any case, most modern engines aren't spark timing knock limited, unlike most older engines. Modern engines (and the f22 is still fundamentally a 'modern' design, despite it's age now) tend to start losing power at spark advance before knock starts to occur, so there is no real point in the ECU 'tuning to knock', as this won't be the most efficient timing.

This isn't the case with older engines that typically have less well designed combustion chambers that tend to be more knock inducing, these will typically make more power the more you advance the timing, up until knock sets in. This is why in the good old days, for highest torque, you could advance spark timing until you had audible knock, then back it off a tad for safety (but not these days with engines that aren't knock torque limited).

My understanding is that the knock sensor is there to step in and retard timing when knock does occur, which is an unusual condition, i.e. it shouldn't be occurring. The knock sensor is just a fail safe mechanism, not a sensor that is used to set normal operating parameters...

At least that's my understanding...

[H311RA151N]

Dynamometer tuning. Uses a knock sensor to set ignition timing. After advancing or retarding the timing, a corresponding change in power output will usually occur. A load type dynamometer is the best way to accomplish this as the engine can be held at a steady speed and load while the timing is adjusted for maximum output.

Mechanical timing advance. Operates off inertia. Weights and springs inside the distributor spin and affect the timing advance according to engine speed by altering the angular position of the timing sensor shaft with respect to the actual engine position.

Vacuum timing advance. Normally used in conjunction with mechanical advance. Vacuum advance works by using a manifold vacuum source to advance the timing at low to mid engine load conditions by rotating the position sensor (contact points, hall effect or optical sensor, reluctor stator, etc.) mounting plate in the distributor with respect to the distributor shaft. Vacuum advance is diminished at wide open throttle (WOT), causing the timing advance to return to the base advance in addition to the mechanical advance.

Computer-controlled ignition systems. The computer has a timing map with spark advance values for all combinations of engine speed and engine load. The computer will send a signal to the ignition coil at the indicated time in the timing map in order to fire the spark plug. Most computers from original equipment manufacturers (OEM) cannot be modified so changing the timing advance curve is not possible. Overall timing changes are still possible, depending on the engine design. Aftermarket engine control units allow the tuner to make changes to the timing map. This allows the timing to be advanced or retarded based on various engine applications.



I see what you are saying about it being necessary to "jump" or what ever the hell you want to call it, the "diagnostic port."

But none of this applies to this thread. The OP wanted to know if his timing belt was a tooth off and it isn't. It is a necessity to set the ignition timing with a timing light no matter if or how much or how little the ignition timing is corrected by the ECU.

Kev1990, if you read all this don't get confused by it. Just get a timing light and set it. None of this other stuff matters to you and will likely only confuse you more.

[Kev1990]

ROFL dw man I'm not confused by all of that I know how the ECU and everything works lol. Thank you very much for all of your help I love how you always keep updating the posts . I like to use these forums for help or like confirmation you know? It really does help having a few people helping you on here lol.

[H311RA151N]

ROFL dw man I'm not confused by all of that I know how the ECU and everything works lol. Thank you very much for all of your help I love how you always keep updating the posts . I like to use these forums for help or like confirmation you know? It really does help having a few people helping you on here lol.

No problem bud, and you are quite the intelligent fellow! I enjoy helping you and I will be around if you need anything.

This forum is simply amazing. A great bunch of guys and gals and I think we will all be here for a long long time.

[Kev1990]

LOL thanks again man you reply soo quick too witch is EPIC there's not many members that will post at all. Depends on the subject I guess though. Where are you from anyways if you don't mind me asking? Also this was my first time EVER messing with timing but I am progressively learning more and more doing harder projects as I go. The next thing ill do hopefully soon is a valve adjustment for the first time lol. Just realized your from Missouri I'm from NJ and dam! Your a gold member I won't lie I'm actually kevinhughes13 too because once I reached so many posts it wouldn't let me post in the beginner's thread so I guess ill have to move on to the pro thread eventually though lol and last night I had someone on the street tell me I'm gonna blow my engine Bahahahhabahahaha it's always possible though.

[H311RA151N]

LOL thanks again man you reply soo quick too witch is EPIC there's not many members that will post at all. Depends on the subject I guess though. Where are you from anyways if you don't mind me asking? Also this was my first time EVER messing with timing but I am progressively learning more and more doing harder projects as I go. The next thing ill do hopefully soon is a valve adjustment for the first time lol.

I sit in the office of my shop all day where I work. I run an ebay store and I'm entrepreneuring into other things as well. So I'm right here by my computer all day! Right now I'm making cannon barrels for a guy who creates Civil war reproduction cannons. I live between Springfield and Branson Missouri.

This forum has every thing you will need and some real smart people too. The valve adjustment is a breeze with the DIY.

[Kev1990]

Hmm that's kl . True hopefully the valve adjustment will go well lol I wish I had a none labor intensive job ROFL but even in the office it's work. What do you sell on eBay?

[H311RA151N]

The valve adjustment will go fine I'm sure. Just take your time and it will turn out all good man.


I was involved in a car accident March 2012 which has left me lacking physically. Currently I can do everything I done before except walk very well so I have had to find other avenues of work. Soon I will be released to return to regular work which I may do. This damn screen hurts my eyes to look at all day.

It's a long story how I got into it actually but I sell nitro powered R/C parts and kits primarily. Helicopters, planes, cars and trucks and everything to go with them. That's my meal ticket. My job. Everything else is extra and for fun/experience.

[Kev1990]

Ah dam man I'm sorry to hear that. But I like what you sell yeah a computer screen can hurt your eyes being on it all day but sometimes I wish I had a desk job but I do like to work on cars in general keep them running in top shape lol the only thing that EVER really pissed me off when fixing a car was when I had to change my alternator 6! Times! Like W.T.F they were testing bad as they were pulling them off the shelf I found out LOL! First one the bearing failed rest of them voltage regulator failed in less then a couple hours of use one even coulda fried my electrical shit because it started charging 16-17 volts then I had one that just flat out wouldn't work then I'd smack it with something and it'd start charging L.M.F.A.O I must add that NEVER WILL I EVER buy a Autozone alternator again lol it was just the closest store when my original one went bad.

[johnl]

Dynamometer tuning. Uses a knock sensor to set ignition timing. After advancing or retarding the timing, a corresponding change in power output will usually occur. A load type dynamometer is the best way to accomplish this as the engine can be held at a steady speed and load while the timing is adjusted for maximum output.

Dynamometers measure torque and power, that's all they do. They are used to set ignition timing and a lot more. A knock sensor is something else that may be used to help prevent accidental damage during a dyno run. It's not used as the arbiter of highest output.

As I said earlier the onset of knock (as the ignition timing is advanced) is only the timing that will give the greatest torque with some engines, it isn't for many many others. So, why would we want to use a dynamometer to find the ignition timing knock point when it's likely this isn't where the engines optimum output will be found?

With a dyno all we are interested in is the torque / power numbers, a knock sensor is only to alert us that we are entering a dangerous level of advance (or whatever else may be responsible for the knock), which can occur with some engines as we tweak the timing further and further advanced looking for the highest output, but not with many others. The power numbers would tell us because power drops away with knock, but it may be too late then...

Next two paragraphs deleted due to (archaic) mechanical and vacuum advance being irrelevant to this discussion.

Computer-controlled ignition systems. The computer has a timing map with spark advance values for all combinations of engine speed and engine load. The computer will send a signal to the ignition coil at the indicated time in the timing map in order to fire the spark plug. Most computers from original equipment manufacturers (OEM) cannot be modified so changing the timing advance curve is not possible. Overall timing changes are still possible, depending on the engine design. Aftermarket engine control units allow the tuner to make changes to the timing map. This allows the timing to be advanced or retarded based on various engine applications.

Which supports my comments.

I see what you are saying about it being necessary to "jump" or what ever the hell you want to call it, the "diagnostic port."

You sound annoyed? Why? It's just a discussion...

But none of this applies to this thread. The OP wanted to know if his timing belt was a tooth off and it isn't. It is a necessity to set the ignition timing with a timing light no matter if or how much or how little the ignition timing is corrected by the ECU.

That's what I said, the rest is just 'matters arising' from the discussion. I've often found that 'matters arising' from a question, even if not strictly pertinent to the specific limitation of the question, can be as useful / interesting as the direct simple answer, and sometimes more so.

At any rate, the take home for the OP is do use a timing light, and do 'jump' the diagnostic port when setting the base timing, the other stuff is just of interest, well maybe to some people...

[H311RA151N]

Johnl, All that info was cut and pasted from a website specifically for ignition timing. It was not in my own words. So if you disagree with it I don't know what to tell you. That is the info made available by professionals who specialize in the matter.

There is a method of ignition timing based off dynamometer tuning that uses a knock sensor to set ignition timing. It is valid information and it is fact no matter who likes it or not. I'm sorry, I simply do not know what to tell you.

I was incorrect about the sensitivity of a knock sensor and when it is actually used to change anything. But ignition timing does work off a map or parameters (which ever you prefer to call it). Just as I said. That map never changes. Unless someone get's in there and changes it.

I read it for what it says. The computer has a timing map with spark advance values for all combinations of engine speed and engine load. Key word, timing map. It doesn't do what it feels best, it does what it's map tells it to do under that particular scenario. It is gathering the data to do so from the sensors but it is not figuring it out on it's own as the ignition timing is in the map. So the ignition timing is a fixed setting and by fixed the data in the map never changes. It does pick and choose which part of the map is best but it doesn't make up the map. The map is pre-existing. That's what I'm getting at. Maybe we are talking about the same thing but describing it different.

I'm not annoyed at all. I just used quotations because you did. I took the hint that you didn't like the term "jump". Maybe I should use "cross" or "connect"? Honestly I just try to get the point across as simply as I can to provide the help being requested.

Matters arising from discussion is fine and dandy. And it can be productive. But when it's questioning and testing someones credibility in a thread where they are trying to help someone it's frustrating. I could understand if I was giving false info but I'm not. But it's all good, no harm no foul.

[H311RA151N]

Ah dam man I'm sorry to hear that. But I like what you sell yeah a computer screen can hurt your eyes being on it all day but sometimes I wish I had a desk job but I do like to work on cars in general keep them running in top shape lol the only thing that EVER really pissed me off when fixing a car was when I had to change my alternator 6! Times! Like W.T.F they were testing bad as they were pulling them off the shelf I found out LOL! First one the bearing failed rest of them voltage regulator failed in less then a couple hours of use one even coulda fried my electrical shit because it started charging 16-17 volts then I had one that just flat out wouldn't work then I'd smack it with something and it'd start charging L.M.F.A.O I must add that NEVER WILL I EVER buy a Autozone alternator again lol it was just the closest store when my original one went bad.

That how life is man! But yeah, I see what you are saying. Real physical labor sucks. Like construction which I done for a few years.

I hate remanufactured parts for that very reason. No one can ever seem to get them right. And 16-17 volts?

I have had them not produce proper voltage under a certain RPM. Past 3000 RPM they would kick the batter light on.

[johnl]

Johnl, All that info was cut and pasted from a website specifically for ignition timing. It was not in my own words. So if you disagree with it I don't know what to tell you. That is the info made available by professionals who specialize in the matter.

I suspect a level of 'dumbing down' from the author you were quoting, or at least over-simplifying...

There is a method of ignition timing based off dynamometer tuning that uses a knock sensor to set ignition timing. It is valid information and it is fact no matter who likes it or not. I'm sorry, I simply do not know what to tell you.

Yes I agree, it is valid to use a knock sensor as a safety measure when tuning on a dyno. I also agree that with some engines it is possible to 'tune to knock' (i.e. detonation) and thus achieve the highest torque output from that motor, but it is motor specific (usually motors with older combustion chamber designs). However, modern 'pent-roof' designs are far less likely to suffer from detonation (at least it will take more 'aggressive' ignition timing, among other things, to produce it), and thus are less likely to create their highest output just prior to knock occurring, but at some point significantly less advanced than that (even if knock doesn't occur, but the timing is too advanced, then the rising piston must rise against the pressure caused by combustion being somewhat premature, which 'wastes' power, i.e. it is an unnecessary pumping loss). So, what may work for one engine (i.e. tuning to knock), won't work for other engines, it's not a blanket practice that can be universally applied.

I was incorrect about the sensitivity of a knock sensor and when it is actually used to change anything. But ignition timing does work off a map or parameters (which ever you prefer to call it). Just as I said. That map never changes. Unless someone get's in there and changes it.

Agreed.

I read it for what it says. The computer has a timing map with spark advance values for all combinations of engine speed and engine load. Key word, timing map. It doesn't do what it feels best, it does what it's map tells it to do under that particular scenario. It is gathering the data to do so from the sensors but it is not figuring it out on it's own as the ignition timing is in the map. So the ignition timing is a fixed setting and by fixed the data in the map never changes. It does pick and choose which part of the map is best but it doesn't make up the map. The map is pre-existing. That's what I'm getting at. Maybe we are talking about the same thing but describing it different.

I think there is a degree of each of us describing a similar thing in differing ways (or perhaps me explaining my meaning less than clearly enough). Yes, the ECU can only do what it's programmed maps tell it to do. It accesses different parts of the mapping dependant on various signal inputs. If the base timing is not correct then it will be operating from a false 'assumption' as to where the timing actually is at any given point, resulting in a less than optimum timing for the actual in cylinder conditions.

As an example, if the ECU is not 'jumped' then at idle it will be attempting to set both the timing and the idle speed to meet what it want's to see according to various inputs. To do this it will be 'fiddling' with the IACV and the as mapped ignition timing (neither of which are an 'input'), at least trying to find a point on the map where it is getting both idle speed and timing as close as it can to being correct (i.e. what it 'thinks' is correct, according to it's programme and the inputs it's getting). I don't know how it does this, or which (idle speed vs ignition timing) might be given priority if such a point doesn't perfectly exist in the programming, though I suspect ignition timing would be given highest priority.

I'm not annoyed at all. I just used quotations because you did. I took the hint that you didn't like the term "jump". Maybe I should use "cross" or "connect"? Honestly I just try to get the point across as simply as I can to provide the help being requested.

I'm glad I haven't caused you any annoyance. I tend to use quotes ("x") when I'm quoting someone elses word usage, and 'x' quotes when I'm either not certain of the correct term, or if there are several terms that might be used, or if I'm using a term that is convenient but perhaps not exact.

Matters arising from discussion is fine and dandy. And it can be productive. But when it's questioning and testing someones credibility in a thread where they are trying to help someone it's frustrating. I could understand if I was giving false info but I'm not. But it's all good, no harm no foul.

I didn't mean to question your credibility, I agree with most of what you've said. My understandings are as debatable as anyone else's, and more so than many. If I recall correctly this extension of the discussion didn't start off with me questioning one of your statements, but me questioning your questioning of one of my statements. That's fine, I have no problem with that. It's good to be able to have a discussion where it doesn't degenerate into something less productive, and less pleasant...