Stock Ignition Timing Map

[Lizzord30]

Didnt want to take over the other post so made a new one here.

I want to try to make an gustimation map of the stock timing curve.

 

For discussion sake lets say 15psi

 

Modifiers:

 

Vacume advance -7 degree per 1psi

How much total advance with vac?

 

Distributor Weights with 2 springs strenths

 

Ignitor/Knock Upto -12 when detects knock?

With knock sensor dissconnected -8

 

Colant temp/altude below 95f or high alt advance 5

 

Ignition Timing adjusting terminal

+12v will advance 5 low alt

Ground Retard 5 high alt But maybe always will do that??? anyone know

 

Base Timing BTDC 10

 

Somewhere in the manual before i seen something giveing a roughf idea of what the distributor advance was but cant find it now anyone know????

 

Thanks! Any corrections or ideas or more info would be great!

[Lizzord30]

Ok found where it says!

No advance from the Governor(weights) till 1,200rpm

goes from 0 to 10 degrees at 2,000

from 10 advance at 2,000 to 33 advance at 6,000rpm Working on makeing a Map now! Will post once finished

[Lizzord30]

Lets say low altitude and engine is over 95f Running 15psi And knocks starts at 13psi with spooling to 13psi starting at 4088 rpms probly a big high rpm but o well.

 

Ok tried to past from exel but total failor impossible to read lol

 

Link to Excel spread sheet

 

Kinda wish they had a Vac advance that went more like 15psi! that would be great too bad...

Edited April 29, 2013 by Lizzord30

[Lizzord30]

Ok seams Like I figured out About the right setup for Stock system running 15psi Ground out the Knock sensor so it doesnt do anything, then to Set the max Timing at 30 with a good working Vac Advance and a base timing of 10. This should give you a Max timing of 23 at 3740 rpm Just one max timing more then with stock setup and the Knock box kicking in, but should be much more smooth and more conservative in the area that are not having knock. I added a second Map on the file I linked in the last post.

[Shelby]

only problem is that seting will kill mpg at cruise and mid range performance

[Lizzord30]

only problem is that seting will kill mpg at cruise and mid range performance

 

Good point Maybe if you could delay the start of the Vacume advance? Like if it started to retard at 7psi and retard 7psi from 7psi to 14.

[Shelby]

as I mentioned earlier find out exactly how much the vacuum advance unit retards the timeing @ 10 lbs and at 18 lbs pressure then decide how to control the retard

[Lizzord30]

Would think after over 30yrs someone would have this information I know some may not be quite as good as others but i have like 5 diff vac advances and they all look pretty simuler and probly have about the same function. That said the vac advance has very little advancing capablity id be suprised if its over 4 vac(2timing) If you just go by how much it moves in the other direction probly would be only 1 timing (2 vac).

[StarquestRescue]

With a mighty vac, compressed air and a timing light you can test the units on the car to see the results and consistency between the units. Guessing does not cut it.

[StarquestRescue]

Some timing tables in here.

 

http://www.starquestclub.com/forum/index.php?showtopic=108396&pid=1052913&st=0entry1052913

 

Not sure who posted this. Factor in your -7 from from the vac/boost retard actuator. And if you factor in the 12* that the knock sensor can pull, you end up about where the successful mpi's run.

 

Timing mechanical + base

 

500/10°

1000/10°

1500/17°

2000/21°

2500/23°

3000/25°

3500/29°

4000/31°

4500/38°

5000/42°

5500/44°

 

Pasted from <http://www.starquestclub.com/forum/index.php?showtopic=125059&pid=1217382&st=0entry1217382>

Edited May 2, 2013 by StarquestRescue

[StarquestRescue]

Most never check there knock sensor, here's a way to do it. The symptoms of the guys car that i posted that for was that the engine had developed a little bit of a hesitation/ stutter. The problem was found to be a broken knock sensor wire. Broken wire = 8* retard, which was just enough to induce a little bit of a misfire on the guys (typical rich as hell sq with no tuning system)car.

 

Knock sensor

 

Another way to check it.

 

Disconnect the vacuum advance. Put a timing light on the crank pull and watch how the timing advance as you rev the engine a little. Say to about 2500 should be enough. Than disconnect the knock sensor plug and repeat. It should act different, the timing will start to advance and than be pulled back some. If there is no difference ( the timing pulls back a little after it starts to advance) with and with out the knock sensor plugged in that is an indication of a problem. Reconnect the vacuum advance when done.

 

Pasted from <http://www.starquestclub.com/forum/index.php?showtopic=127048&pid=1240473&st=0entry1240473>

 

 

I just did the tests on my 87 non intercooled car. This car had a new Mitsu sensor about 5 years ago. The timing at idle was not effected by disconnection the knock sensor. The manual says the knock sensor is not enabled at idle. Step two of the test procedure is to disconnect the air flow sensor. My car will not idle with the airflow sensor disconnected.

Next i drove the car, there may have some times been a slight decrease in power when the data logger showed pin 61 enabling the knock sensor. Basically drove like nothing was wrong. When i reconnected the sensor. (quite a trick on a hot engine) it did perk up a little.

Edit, do this test with the vacume advace hose disconnected. It will show the 8* retard clearly.

So i tried blipping the throttle with a timing light on it. And i could see a difference in how the timing advanced or failed to, with or with out the sensor connected, consistent with a 8 degree retard.

My logger shows it does not take much airflow load or throttle blip to activate pin 61, which goes to the igniter box.

Edited by StarquestRescue, 30 June 2011 - 12:26 PM.

 

Pasted from <http://www.starquestclub.com/forum/index.php?showtopic=121497&st=80>

 

Ok, i disconnected pin 61 from the ecu, which i figured would enable the knock sensor. No change in idle timing.

Than took the butt end of a 1/2 inch breaker bar and tapped on the block. There is a spot above the sensor and right behind the timing cover that was easy to tap. A couple of taps does nothing, but 6 or 8 quick taps and the timing starts to retard. It is a gradual change and when i stopped tapping the timing gradually returned to normal 10* before tdc. Maybe 5 seconds to return to normal.

Reconnected pin 61 and tapped on the block in the same manner. Timing stays at 10*.

 

Pasted from <http://www.starquestclub.com/forum/index.php?showtopic=121497&st=80>

 

[Funky Phil]

I dont understand why you would want to disable the knock sensor??

 

Now what are you doing this for? A street car? If so, why not order an MSD recurve kit and mess with that? I have wanted to do that for a while, but would like to use a distributor recurve bench if I could ever gain access to one.

[Funky Phil]

btw john, you need to update the numbers in your sig

[Shelby]

I dont understand why you would want to disable the knock sensor??

 

Now what are you doing this for? A street car? If so, why not order an MSD recurve kit and mess with that? I have wanted to do that for a while, but would like to use a distributor recurve bench if I could ever gain access to one.

 

funny we had one of those old dist machines at work and in all the years I was there (over 30 ) never had a mechanic that knew what it was used for lol

[Lizzord30]

Great info.

 

I am not planning this for any one car I am merely trying to get the information on what the stock curve is and thinking of ways to improve it for a car running 15psi.

 

BTW that timing curve you gave is pretty much exactly what I calculated from what the service manual says. But I Agree about no guessing, I put marks on my crank to see the the change. So it seams like the ECU and the knock box work separatly by what you said, but yet use the same wire. Like the ecu would prevent accidental retard of timing. But its interesting to see that the knock box will gradualy change and not suddenly, I wonder when the ecu connected does it adjust the timing in a less gradual manner?

 

I dont necessarily want to disconnect the knock sensor I would rather that the ignition curve is in a way that we dont have any knock in the first place with it still connected as a safty net, I dont like relying on the safty net. And still not really answer the question of is the knock sensor saying their is detonation when actually its just engine vibration.

 

Based on what the picture Indian posted about the1983 vacuame advance wonder if its the same as the newer ones?) it will retard degrees 7 for 8.7psi and advance 15 degrees from 10.8vac. Of course need to be tested. I am just saying what the service manual says. We need some people to test/or post their test results. Once I get the engine in the car and running I will be testing but would be good to have several to see how consistant it is.

 

On a side note about the recurve kit, I noticed one things weird that one of my distributors has different size springs then the other. One has a small one and a big one, but my other has 2 big springs. Anyone else notice this maybe its from a different year or something.Maybe the cars running lower boost had smaller springs but they upgraded the spring for the 88-89?

[scott87star]

There are two different curves, one for intercooled cars and one without, that is the difference in springs.

[Lizzord30]

There are two different curves, one for intercooled cars and one without, that is the difference in springs.

 

Hmm which one is the IC and which one is the non ic? Anyone know? Stronger springs for the IC or the non IC?

 

Also Never heard anyone mention the adjustablity of the stock vacume advance for boost retard! Going to measure to see the adjustablity and see the approximate change in timing it will allow. I know you can make it so it will almost do no retard if you move the hex on the end all the way in. But seeing if will give you more boost retard the other way, all the way out.

Edited May 2, 2013 by Lizzord30

[Shelby]

Luke also keep in mind your going to be ruing an auto trans truck,, timeing curve for an auto car and 5 spd car are diff

also remember this at no time does the vacuum adv work with WOT , it only funtions at mid range and cruise to retard,, other wise it's only function is to retard the timeing under boost

 

when testing the timeing in neutral it does work because you have no load on the engine but on the road under load it does not work

[Lizzord30]

Well the vacume advance really should be called boost retard unit. Your right it wont effect WOT only boot reterd, but the adjusting screw will adjust the amount of boost restart. I measured and will calculate later to see about how much it should adjust. I have 3 different vacume advances, ill test and compare them. see what I come up with.

[Shelby]

on my MPi truck I ran a boost only reference hose , never had any sign I had a vacuum advance system missing

also almost every vac adv unit I have saw had numbers stamped on the connection arm,, showing amount of change , like 10.5 or 12

 

as to that adj screw changing boost degrees I doubt it , normaly it's just a stop limit screw for the vac side of the unit

[Lizzord30]

on my MPi truck I ran a boost only reference hose , never had any sign I had a vacuum advance system missing

also almost every vac adv unit I have saw had numbers stamped on the connection arm,, showing amount of change , like 10.5 or 12

 

as to that adj screw changing boost degrees I doubt it , normaly it's just a stop limit screw for the vac side of the unit

 

I have 3 different vac advance units for the 2.6 2 carb ones and the conquest one, all the conquest I have seam to be the same. The set screw only adjust retard doesnt effect vacume advance (too bad I wish it had more vacume advance under vacume). The 2 carb units like you said have a number stamped on them 10 for the stander 2.6 carb, and 20 for the California spec 2.6 carb, But none of the turbo vacume advances I have has a Number on them. you can try adjust the screw in and it will give almost 0 boost retard adjust it all the way out (and it feels kinda loose not really sure it should be that far out) and it will give a little more boost retard. I would guess that it will give 2 to 5 more vac retard but not more range like max is 7psi will just reduce retard more not go per psi. Of course you could get by this by like a bleeder or something. Just an idea.

[Shelby]

dist degrees is 1/2 that of crank degrees so 7 at the vac adv unit would be 14 at the crank

[StarquestRescue]

 

 

I have 3 different vac advance units for the 2.6 2 carb ones and the conquest one, all the conquest I have seam to be the same. The set screw only adjust retard doesnt effect vacume advance (too bad I wish it had more vacume advance under vacume). The 2 carb units like you said have a number stamped on them 10 for the stander 2.6 carb, and 20 for the California spec 2.6 carb, But none of the turbo vacume advances I have has a Number on them. you can try adjust the screw in and it will give almost 0 boost retard adjust it all the way out (and it feels kinda loose not really sure it should be that far out) and it will give a little more boost retard. I would guess that it will give 2 to 5 more vac retard but not more range like max is 7psi will just reduce retard more not go per psi. Of course you could get by this by like a bleeder or something. Just an idea.

THe carb units do not belong on a starquest. They have no retard capability.

 

You are still guessing. Tell us what the timing light shows you. That is the only # that maters.

 

A bleeder will give you less advanced or retard. I thought you wanted more retard?

[Lizzord30]

THe carb units do not belong on a starquest. They have no retard capability.

 

You are still guessing. Tell us what the timing light shows you. That is the only # that maters.

 

A bleeder will give you less advanced or retard. I thought you wanted more retard?

 

Its more about finding options, and finding what you want, and the way to get it to work. My truck isnt running yet waiting for parts, so I cant really test it first hand.

 

I know the carb units don't below on the conquest just comparing them.

 

About the bleeder your wrong it would not reduce the overall retard (put perhaps the vacume advance) It would only delay its activation and reduce its speed to activate. from my experiences the T bleed (with the same size) usually effects the boost about 2psi so after 2 psi over max it would max out the boost retard.

 

Of course if your fine with stock everything go ahead dont need to try to improve.

 

Ideally would have more advance off boost, more retard on boost (equal to boost or so) and the knock sensor would kick in as a safety net only. But their is several ways to do any of these to make the right combo.

 

My thinking is

step 1 find out what stock was meant to be (service manual)

step 2 find out what the cars actually do (best for multiple examples)

step 3 Find out what you want (this depends on desires and setup fuel psi engine setup...)

step 4 find ways to adjust and get step 2 closest to step 3 (With keeping the stock TBI of course can do whatever you want with a EMS)

[StarquestRescue]

There are quite a verity of parts that could be on a given car. What with stuff being swapped around over the years. Plus the after market actuators which probably do not match factors spec's. And who knows how many cars that some one inadvertently put a carb actuator on.

 

This is a list Indiana posted. I think there were actually 2 actuator for 88-89, one for 5 speed one for auto.

 

The other "test" about the air flow sensor being unplugged, at least for 88s I've seen some do run with it unplugged and some do not. The ignitor after 87 is different so don't expect it to react in the exact same way and the ignitors as well as the distributors and governor sets (weights) changed many times over the years

There are 4 plastic ignitors and 3 metal ones (83 is metal)

1984

Ignitor

MD071942

1985/86

Ignitor

MD071942

MD093767 "P" series

1987

Ignitor

MD109942

1988/89

Ignitor

MD125748

Mechanical or vacuum advance shouldn't be active at idle speeds so which year dist. you are using is not supposed to matter but a change in timing from a knock signal will effect rpms so that COULD also effect the change you see if you have the rpms higher than idle when you test to see if it works.

1984

Distributor

MD061593

Governor set

MD607784

Vac Adv Unit

MD607785

1985/86

Distributor

MD061593

MD093766 after 12-84

Governor set

MD607784

MD611368 for 3766

Vac Adv unit

MD607785

MD611360 for 3766

1987

Distbibutor

MD109937

MD109938 w/intercooler

Governor set

MD607784 for 9937

MD611368 for 9938

Vac Adv Unit

MD611360

1988/89

Distributor

MD119754

Governor set

MD611368

Vac Adv Unit

MD611769

 

Pasted from <http://www.starquestclub.com/forum/index.php?showtopic=121497&pid=1184846&st=90entry1184846>

Edited May 6, 2013 by StarquestRescue