Ignition timing help (scan gauge)
 

Hey Guys,

Im working on tuning a project car of mine, It runs a standalone engine management system that requires you to edit all the variables about the engine.

I'm struggling to find some reliable data about Ignition Timing at 1500RPM under light load (-24 to -16 in-Hg). I know each engine is diffident and will run various numbers but any input will help, Ive seen people who programmed values as low as 16 Deg timing, and some as high as 38 deg.

I think scan gauge lets you monitor spark advance so if anyone can recall what their car runs at 1500 rpm + light loads it would really help out. Logically it would make sense that too much timing will reduce efficiency as it builds excess pressure during compression, even if not at the point of audible pining

Who says you cant have power and an efficent engine, 1973 datsun 240z w/ Toyota 2.5L 1jz-gte, really tall gears :D 300hp, 30 MPG goal

http://carphotos.cardomain.com/ride_...0095_large.jpg

I'm running between 38-40 normally on flat to slightly hilly roads. Our motors are different though...
If you have a wideband, why not try leaning it out on the light load cruise, then you may get better mpg. I'm running mine around 17.5:1 and seeing some nice improvements.

"Light load" is the big DEPENDS in your question.
During normal driving it is often hard to actually hold a solid "steady" cruise at one load level. If you could, then as you said the optimum SA would depend on the engine combination and the conditions. The available torque of the engine in relation to the vehicle weight, drag, and final drive ratio will be major factors in determining the right timing for a given measured load or vacuum.
In general, a torquey engine coupled with a light vehicle and a lot of gear (more torque multiplication), will be able to effectively use more spark advance.
There are many other factors that weigh in on this requirement, such as: coolant temp, air temp, AFR, charge contamination (EGR), static and dynamic compression, camshaft timing, fuel octane, sparkplug type and heat range, etc...

Ultimately you will have to experiment. You should datalog and watch the output from your knock sensor. You can also watch a vacuum gauge and listen for audible spark-knock.

To give you a ballpark for a relatively low compression I6 with highway gearing your spark advance numbers would look something like this at around 1500 RPM:

Vac -- SA
05" -- 16* (heavy accel or PE mode)
10" -- 18* (heavy accel or PE mode)
12" -- 22*
14" -- 28* (light accel)
16" -- 34* (steady cruise @60 MPH ~1500 RPM I'm guessing)
18" -- 36* (light decel)
20" -- 38*
22" -- 40* (heavy decel or DFCO)
24" -- 40* (heavy decel or DFCO)

There is normally a pretty steep shift in SA between a steady cruise and light acceleration. If you're filling out cells in a spark advance table or map, then keep this in mind. The steep shift will show diagonally across your spark table as RPM increases.

If you are running with the turbo boost, then naturally you're going to see an even steeper drop in SA as manifold pressure is increased.

This steep shift throws off a lot of people calibrating their spark maps because it isn't a very smooth transition that they may be wanting to see.

Are you running a mechanical+vacuum advance distributor or a fully ECM controlled advance?

As an example of SA at a steady 60MPH cruise in my Ford Focus, the scangauge says 41*. Keep in mind this is assuming a heavy EGR operation that accounts for around 30% of the total VE value at that point in the calibration (30% dead air to slow the burn).

Without EGR the burn speed is higher, and the optimum SA is usually 5* to 10* lower for many engines.

On most engines, you can be well into the 35 - 45 degree range for SA before you start to lose efficiency.

I have some limited experience with stand alone units . The factory changes spark advance a lot in most cars some goes to 40 deg at low speed/ part throttle vacuums .
On after market though on many units if you try to do same things you can run into transit knock advance issues , its like the stand alone is not as fast ECU or not enough break points . Either way many don't go high on part throttle advance so transition to load is smoother. another way to think of it is pre ECU control , think of the vacuum advance unit on distributor and running with it off , thats another way to look at it .

See if you can add a knock sensor to the management system it would just go into one of the freeze plug locations. That way you will be able to see the knock and adjust from there.

My 03 GrandPrix I will see 50degrees in low loads cruising that is the ECU max but during that time EGR is running adding timing also I think that the spark table calls for a max of 42ish I would have to look at my tune.

Thats for all the input!!

My ECU dosn't have any knock sensor capability so I only have my eyes and eyes to detect any knock. Ive run as high as 32 deg before I started to question my luck and pulled it back to 30 for now (29 in my picture). The rest of my timing map is fine, its generally backed up by a lot of others out there for the 1jz, just the 1500 range is always all over the place, and as I spend a lot of time cursing at 1500 id like to get it right.

The 8:5 compression and 91 oct will slow down he burn, so I can few a couple more degrees on for that. My 1500 rpm is around 70 km/h if I recall correctly, maybe closer to 80, its not running 1500 at highway speeds but my county cruising range is right at 1500-2000. While not extremely tall, 2000 on the highway is a lot lower than then 3200 my last did.


http://img10.imageshack.us/img10/8954/74792739.jpg

I do have a wide band set up that lets me adjust the target A/F, right now I've set it for 15.3:1, and tuned my maps to around 14.7:1 and let the closed loop correct for it, are noticeable improvements found by leaning it out much more? 17.5:1 always seemed like a lean burn condition to me, will a stock engine take this kinda tune?

When you say you can be into the 35 to 45 range before losing efficiency are you talking specifically at 1500? At 1500 everything moving slower than usual so I know the timing wont be as far forward as 2000+

If anyone has some thoughts on my map, please let me know, and if it would be helpful to post the entire map Id definitely like to if someone can give me their input

How much timing are you running at idle and 1k rpm . How many maps are there between 1k and 2k (map ever 100, 200, 500 etc) rpm ?
Does This turbo engine have a EGR working , that will be a factor .
I think 35 deg at 1500-2000 "probably" be ok even without EGR operating but needs testing .

With out factory knock sensor you could use external knock sensor or microphone listening devise and ride around an test. Just make sure you pick warm day with engine warmed up good . Another way if your careful (no boost or loads) is to use 87 fuel and see when timing induces a lit ping at 1500. then back off a bit and use 91 .
Thats only if you really know what light ping sounds like and your exhaust/engine is quiet so you can hear good .

If you could please verify the units along your X-axis there.
PSI and inches of Hg are not the same thing.

edit: If you don't completely trust converting the figures, then just put a vacuum gauge on your manifold that reads in inches Hg, then compare to what your datalogging values are.

no EGR, JDM engine. I have a vac/boost gauge int he car and the values between my MAP sensor and boost gauge are comparable. The X axis is all in PSI, the conversion is somewhere around 2.03, I can talk in -psi or in-Hg, but not many people use -psi.

the incitements are in 500 rpm between maps with the ecu averaging the values in between. Someone is running 38 degrees apparently, so 35 seems reasonable, Ive run 32 before. Im not really experienced with detecting ping, ill ramp up slowly, eeping a keen ear open, I've installed multiple mufflers ont he car to reduce noise, its still loudn with a lot of road noise but i think I can still pick it out.

Thanks a lot for participating in the discussion everyone, ive posted the question on 4 different forums without a responce at all till now :D

2 inch of mercury = approx 1 PSI

Well, from what I'm seeing on your graph, your 7.74 PSI x 2.03 = 15.75 inches Hg seems about right for a steady cruise speed.
Without EGR and with your low compression the numbers I gave as an example should be pretty close. You said that you're going a bit slower than 60 MPH though, so unless your car has a lot of drag somewhere then you may be able to get away with a little more than what I have in my example for your cruise speed.

If you really want to tune to the edge and are worried you won't hear the knock, then there are aftermarket stand-alone kits that allow you to use a knock sensor and display the feedback for you. More sophisticated ones can also adjust the SA automatically, but they are more pricey.

As for a lean AFR: I have tuned a 1998 C5 Corvette that was very steeply geared at 3.15:1 with 29" diameter rear tires (the owner/driver weighed around 370 lbs) - it was a drag racer.

I set up an open-loop tune (no O2 feedback) with:
DECEL AFR of 16.5:1 or DFCO with less load (aggressive DFCO setting)
steady cruise AFR of 15.5:1
very light ACCEL AFR 14.5:1
moderate (but normal) ACCEL AFR 13.8
heavier (but not PE mode) ACCEL AFR 12.8:1

I never hypermiled it to test, but the car had a factory MPG gauge that averaged around 25 MPG with his normal driving.
The SA numbers for that engine wouldn't be comparable to yours so I won't even mention them. I just wanted to offer an example of AFR varying with engine load.
If you try to run 17.5:1 across the board, then you will definitely experience some lean misfire when you load the engine in your upper gears.
Very lean mixtures like that require excessive SA, and that will reach a point of being counterproductive in the search for efficiency. It will also be hard to keep the engine from surging when transitioning from cruise to light ACCEL.

thanks again, i'll give everything we've talked about a shot. with my o2 settings I can controll the max throttle point, so I can set it to about 4-5% and pull the a/f ration back, say 15.5 to 16, and when i get into the pedal at all, it will revert back to my base map of about 14.5:1. Im still playing with the boost a/f, pulling it back slowly, still in the 9:1 to 10.5:1 range, once I get it leaned out to about 11.5-12 I think ill notice a bit of an improvement in power aswell, not that its slow by any means right now :D

I have dec fuel cut till 1400 rpm, i may increase that down to 1000 and see how ti works out.

Is my most efficient SA going to be right before audible pining starts to occur? Tomorrow ill bump the timing to 32 again and see how she does.

The only thing you might want to check is head/EGT temps .
With running ignition timing high with no EGR and lean A/F (17:1 ) .
You might get a condition were head temps raise during cruising , then when you go to boost your starting with elevated temps . not saying it will be problem but something to keep in mind . monitor water/oil and EGT if you have gauge . run baseline A/F and timing your running now (like 30-35deg) . then make your A/F and any timing changes (best to do each separate ) then compare if temps go any higher .

How much boost are you running ?

Ive got an EGT probe but no gauge, I guess in the future its something Ill have to consider installing. Im only running 9-10 psi right now from a fairly large holset turbo. I have a 2 bar MAP sensor so I cant go over 14.7 psi anmyways, my final pressure will probably be around 12 psi. Ill hopefully try out some new settings today, thanks for all the input

With 8+ psi of boost, even with the low compression (although it depends on the cam somewhat), you'll probably start pinging before you overshoot the optimum timing.

thanks ill keep it in mind, but my a/f and SA in boost is more more conservative but ill do some tuning and testing as soon as i can

Yes, for a lot of engines like yours it is for most of your driving.
It also depends on loading.
The more the cylinder is loaded, then the less it is true.
A loaded cylinder has more leeway between efficiency and knock.
That means you can get away with less SA than maximum and not lose a significant amount of vehicle fuel efficiency.
At low loads there is a greater % loss in vehicle fuel efficiency the further away from maximum allowable SA you get, though it often goes unnoticed.

thanks, Im taking the car on tis first long trip tomorrow, about 100km one way, should be interesting since I built the car from the frame up in a garage :D 600miles so far without major incident, hopefully it will take it.

I had some issues the last few days with A/F ratios, it ended up being a disconnected signal wire causing the ECU to lean out, its sorted now and 15.35:1 has been programmed for the drive. Driving great once more

Ive got my Maps adjusted, gonna play with them till I start to dial in the optimum setting. I also did a couple Aero mods, grill block shown to reduce the Cd from .45 to .4 in wind tunnel tests and a front belly pan. Oddly enough the rear spoiler was shown to reduce drag vs a flat hatch, seems wrong but it was backed up by windtunnel tests as well.

What ECU controller are you using ?

So this is basically first real running with it on .

Maybe you could post a higher rpm map, like 4k rpm so we can see how timing is for a rpm were light load to full boost would enter in (assuming 4k rpm is able to get max load ) .

Im running an e6x haltech, not the best but work with what you got, next chance i get I can post a full table. The cars been gradually worked up tot he paint its at now where i feel confident to take it out of my general area and on trips. its got about 900 kms on it, lot of test and tune and its all boiled down to where it is now. fingers crossed for tomorrow :D

Currently at my friends place with the datsun, made it the 100km trip down so thats good right? Didnt guzzle an insain amount of fuel, not sure how much but I think im on the right track. I think I need to work on my 2000 and 2500 timing maps next. I played with them a bit on the drive down but not for long as i was driving. If at 1500 my crusing rpm is 34 deg and light accell or incline is 28, what about 2k and 2.5k? I know theres a substantial jump when u start to rev up a bit, would 39 deg at cruse and 32 light accell/incline @2k be too far foward?

the timing sugested on page one, 34 deg and 28 degrees works nicely, based on that what would you think 2 and 2.5k should be based around?


Thanks!

Meph

This post IRT the picture of your spark table:


I almost always make the columns the same between 0 RPM and 1000 RPM (your first three sections) to cover the idle - usually reduces fluctuations, corrections, and smooths the idle.

If your X axis is actually in inches of HG, then
cranking will start out at Zero vacuum and "pump down" (towards the left of your table) from there to about 12-ish. So if you can imagine the load cell moving from the zero-RPM row and zero-vacuum column down to the 500-RPM row and to the left, jumping in steps of vacuum as the manifold pressure goes through it's pump-down while cranking.

Your first two rows (0-RPM and 500-RPM) should indicate your desired cranking spark from the 13.5"-vacuum column and to the right. That is unless your ECM uses a separate table for just cranking spark, and/or another cranking spark modifier constant or table. There is usually at least a crank modifier table based on coolant temp, so that must be taken into consideration when determining your cranking spark values on your main spark table. A good warm cranking spark value is usually between 6* and 10*.

The 0-RPM through 1000-RPM rows, from 13.5"-vacuum and to the left should represent your desired idle spark. I usually start out by making all of those cells 20* and start from there - experimenting to see what the engine likes best.

The lower left quadrant of your table looks fine. That's all heavy DECEL and/or DFCO area.

Your load cells in the range between 17.44"-vacuum, 7.6"-vacuum, AND 1000-RPM, 2500-RPM (inclusive) is where the meat of your driving will be and will require the most work to get right.

Generally speaking, it looks to me that this area does not drop off quick enough as you move to heavier load cells (towards the right) starting from about the 13.5"-vacuum column. As I said in another post, there should be a fairly steep slope somewhere in there as the load increases from light-cruise, to light-ACCEL, to heavier-ACCEL during most of your normal driving. The lower the RPM, the more sensitive to loading the engine is, and the steeper the slope between one load cell and the next load cell beside it (left-to-right).

Your SA values are only changing one or two degrees as you move left-to-right across load changes in this area of normal driving. That's the biggest problem I see. Without driving your car and watching test equipment I can't tell you for sure where the big changes need to start, but:
If your steady light-cruise is around 13.5"-vacuum, then you will need to reduce your SA numbers in larger steps in the columns to the right of 13.5".
I can imagine a progression from your 30* SA at 13.5"-vacuum down to 18* or 20* by 7.6"-vacuum.
That's my best remote guess to give you an idea the basic shape to shoot for.

A knock sensor will be helpful, but you can do it by ear if you're careful. If you find that your ACCEL isn't causing knock even though your SA values are high, then suspect you have an AFR that's too rich.
The richer the AFR, the less sensitive it is to spark advance changes. I'm guessing that any loads higher than 7.6"-vacuum will be covered by your Power-Enrichment (PE mode). Generally an AFR between 12.2:1 and 12.8:1 will cover PE up to around the zero vacuum point.

The rest of the table should be fine, assuming your PE mode covers 3000-RPM and up.

Best I can do from a distance.
HTH.

What does SA mean ?

Spark Advance