tuning programmable engine management systems
 

OK well I thought I would start an independant thread that has no attachement to anyone person or system to discuss programming engine management systems. There are several users doing this currently with either electromotive systems, stock systems, Haltec or probably even some megasquirt.
Some of the basic issues that have been discussed in other threads are
[EDIT] to prevent the need to read entire thread I will try to update this first post with accepted numbers. These may change as a general consensus is reached. There will always be differences.

idle A/F ITB 13.5-13.8
idle stock 14.2-14.6
cruise 13.5-14.7
cruise A/F ITB 16-17:1 said to be possible. May require 30+* advanced timing. (not confirmed as of 01-24-09)
WOT 12.5 - 13.1

timing idle 0 to 12 btdc (hot-rod would not start at 0 required 12)
cruise 30* to 40*
WOT 30* btdc at peak torque ramping up from 20*. Some say 24* max for twin plug dyno shows even with twin 30* if engine knocks back off timing and recheck. Power loss past 30*

basic a/f ratios
ignition curves
idle
various fuel enrichments, start, warmup, acceleration, air temp, blend

So to kick this off I will start with the A/F ratios. In searching threads back as far as they go the one thing that appears to fairly consistent is the WOT mixture. It appears that the target is 12.5:1 to make power. Some have strayed from this to as high as 13:1 but the majority still put it at 12.5:1 Now that leaves the entire rest of the fuel curve up for debate. I have seen anywhere from 17:1 at cruise to 13.5:1 . The stock system is going to try and get close to 14.7:1 as this is where the most efficient burning takes place. I have found that I get 14.7:1 and it will idle OK but I get a terrible stumble coming off idle. Now that is with individual throttle bodies. The stock system may handle the transistion much better. You will certainly get better mileage and have less emmissions if you can get the ratio up there. The general concensus I have come to is that for throttle bodies anyhow 13.5:1 appears to be about what is needed for a stable idle with no off idle stall. So now the question becomes where do you transition from 13.5 to 12.5. Well I can tell you don't do it right where you cruise or your system will be hunting all over the place. Right now I have 13.5 as a target from 3500rpm 90 kpa down to the minimum rpm and 25kpa. I also have 13.5 for all rpm ranges below 70 kpa. I then transition directy to 12.5 to fill in the upper rpm/ higher kpa area. I don't think the sudden transistion is the way I want it so will be working to smooth that just a bit. I do have wide band with mixture control turned on so if I happen to hit a spot where I have to hold it and that spot is on a transistion then the system really hunts. Anyhow have to go now.

signing-up!

I have recently spent a few hours tuning my new 3.2SS. Build spec is 98mm mahle on SC crank (70.4mm), 10:1 CR, Twin plug, DC40 cams on 108 deg lobe, 46mm TWM ITBs with 30#/hr injectors. . I am using Megasquirt II, V2.2 with 2.888 code. My interface is an Asus EEE 901 with TunerStudio MS software. Data analysis is done with Megalog Viewer.

I found that my car idles best with approximately 13.1:1. I have found that the car does not like anything leaner than 14.5:1 at cruise. Otherwise it will have a lean surge and pop through the intake occasionally. I have WOT bins set at 13.0:1 at 95kPa and 12.8:1 at 100 kPa. I have really crisp throttle response and found that going slightly richer might feel a tad stronger but felt sluggish on throttle transition.

Here is my target AFR.
http://forums.pelicanparts.com/uploa...1232720028.gif


I am completely sold on tunable EFI. Being able to set target values and then achieve these through proper manipulation of fuel levels is very fun and educational. Everyone talks about the improvement going from CIS to carbs. I did that transition and it was impressive. The switch from carbs to EFI was equally enlightening.

There are a few things to look out for when tuning that might cause problems for some. For example, too large of a throttle body in an ITB setup will cause the system to go very lean off-idle due to large amounts of air that dump into the system with small throttle inputs. Swept area is very important here. The cure is abnormally high acceleration enrichment values that cause the system to bog down at higher rpm. My method was to make the low rpm, high MAP values very high in the base map. This acts like enrichment and allows fine-tuning of accel events at higher RPMs.

I updated the first post to include some sort of consensus on settings to avoid having to read the entire post. I will try to update this as things progress.

This is an interesting thread; currently I'm aiming towards building in an "expert" mode on my VFM to MAF system.
The idea being that the user would be able to record areas of low or high A/F ratios and then using my spreadsheets they would re-program the microcontroller in my system with some new curve values, this would tune the A/F ratio in some more. It would just require a PC and a USB cable.

However I am unsure if this would really work at WOT? as far as I know the motronic system goes into "dumb" mode and simply reads in rpms and little else, resorting to its lookup table for values and basically ignores the VFM air volume input, even if it did at 5200rpm the VFM pegs and its flying blind.

:confused:

Dfink wrote,

The stock system is going to try and get close to 14.7:1 as this is where the most efficient burning takes place.


Hello Dfink,

OEM's target stoich for dithering the engine management system to preserve the life of the catalytic converter and maintain the best balance for lowering the three designated "evil" pollutants. 14.7:1 is not the most efficient burn, it is simply the perfect ratio of reactants (14.64:1 by weight), and has little to do with power or economy in a running engine. When tuning a programmable EFI system without a cat, 14.7:1 is really irrelevent. In test engines, max efficiency is around 1.2 lambda (over 16) with 50 degrees ignition advance. I have been tuning EFI for over 10 years (mostly Haltech) and on single throttle applications, there is usually no problem running over 15:1 at part throttle cruise. You just keep lowering the target voltage for the closed loop control until drivability deteriorates. Sloppy idle control and bucking at lean part throttle cruise may be an ITB trait, but you did not go there for idle or cruise performance. With the Haltech ECU's, you have an acceleration enrichment amount and a sustain (time) and it is usually no problem to fix a transition by adding fuel or extending the time. The fuel cut off on closed throttle makes a big mpg difference, but it takes a while to find the best compromise on settings. If you want OEM drivability and not spilling fuel like a drunken sailor, it takes a lot of effort to get it right under all conditions. Hemi head engines (like 911's) with large chambers do not like idling at 14.7:1 and if you are not running a cat, it is an unrealistic goal. On cold starts, you only get one a day and everyday and every engine seems to be different to me.

I have a feeling this thread is gonna be gold!
I'm mapping my engine in a few weeks...

psalt - You are certainly not the first to mention 16-17:1 ratios for cruise so it may be an acceptable range. I found other entries suggesting this is possible. Would like to get some more input before changing the table. I think mine would have trouble at 16:1 any trouble with temps under those conditions or if you just get too lean it doesn't run correctly.
What does a lean condition cause under load. Does it just get hot or does it cause detonation why is it bad to run lean? Why will it kill the engine?

dfink,

You have to separate what happens at light load, part throttle cruise and what happens at WOT under load because they are very different states. One of the hardest thing for a first time tuner to understand is that idle conditions, where most of us started messing with engines, setting timing and twiddling idle screws, is a very small part of the picture and almost meaningless. All you want from an idle is the minimum rpm to prevent stalling. A road engine spends 85% of it's time under 30% load, most of the time is spent accelerating, decelerating and at a steady cruise. AFR's are not static and even the most sophisticated system can only dither the mixture around a target. Detonation only occurs at under high load, usually WOT around peak VE and is meaningless at idle or part throttle cruise. It is a pressure spike from spontaneous combustion of the fuel and cylinder pressure is a function of filling and throttle angle. You are not worried about detonation at 15% throttle. If you are looking for max efficiency, you want to run leaner than 14.7 : 1 with much more timing than 30BTDC under light load. Are you running a cat and do you have closed loop control ?

Well I was hoping to keep this to a general tuning thread. I know every engine combination is going to behave differently. For the sake of arguement let take two engine combinations.

First one stock 9.5:1 with motronic fuel injection. Perhaps first hand information can be provided by scarceller as I know he can proprgam his own stock system.

Second senerio hot-rod 3.4 with DC21 cams 10.5:1 headers full flow exhaust 46mm PMO ITBs, twin plug and full aftermarket engine management

This should about cover anything except turbos as most will fall somewhere in between or both are common.

Mine happens to be in the later category. It has been found by most that in senerio 2 of the hot-rod that an idle mixture leaner than 13.5 tends to cause a stumble coming off idle. There is alot of throttle plate opening at once. It has also been suggested that in the stock system you can go leaner and still have adequate acceleration characteristics. I am open to running leaner at cruise but attempts at idle don't work even when using acceleration enrichments. It just stalls then goes really rich. Cruise is still a mystery to me and is generally not discussed much. Lots of info on idle and WOT.

I have read that not having enough timing advance at idle will cause headers to get really hot. The initial programming of my unit had an idle advance of 12* btdc and I have read where others use that setting. I have also read the stock setting of 0* +- 5* so again conflicting information. Is one good for stock and one good for headers. I agree no knock at idle but in theory you could probably get knock at cruise on single plug when pulling a hill. The twin plug pretty much takes knock out of the equation and it becomes about how the engine runs.

If knock is not the problem with running an engine lean then what is the lean killer everyone talks about. I will assume super high head temps. What does 16 or 17:1 do to head temps during cruise. I don't have a true head temp (spark plug ring) I only have the factory cylinder temp and it does not appear on my system to work well under high load conditions.

Dfink wrote,

If knock is not the problem with running an engine lean then what is the lean killer everyone talks about



I don't know who you are talking to, but if they don't separate cruise from WOT, they are talking nonsense. More lean only means more heat rich of stoich, then temps drop as the AFR goes up. Running lean under high load is a problem and running stoich under load creates the highest temperature. The only issue running lean of stoich during cruise is emissions. If you want to run leaner at cruise, you also have to run more ignition advance or you can get bucking, making you think your too lean.

If you have full control over spark tables, idle timing should be close to TDC. 12 BTDC and 5 BTDC are the result of distributor limitations and the need to meet a curb idle emission test. My advice is to forget AFR and timing at idle, establish a stable idle and work on your tip in stumble. A combination of timing and fuel adjustments should make it disappear.

Only thing I can use for real information myself is an airplane. With an adjustable A/F and cylinder head temps you can really see the head temps go up when running to lean. Of course in an airplane you are under pretty much full load constantly. We then richen the mixture to bring head temps into range. I am not agreeing or disagreeing with the lean cruise just don't know what is safe. Could certainly use a few more opinions. I wish I had a head temp sensor would certainly help the situation. But that leads to another question. If you have spark plug ring head temp sensors or some other type. What is the maximum safe head temp.

Dfink wrote,

Of course in an airplane you are under pretty much full load constantly

Yes, and a 65 mph cruise at 15% throttle in a car is a much lower load. If you are a pilot and understand LOP ( lean of peak) fueling, it should be easy to understand that a road car under lower load can run a lean of stoich mixture.

There are some good articles on fueling on this site:

http://www.avweb.com/news/pelican/pelicans_perch_84_mixture_cht_194816-1.html

which recommends against using CHT valvues for fueling.

There are also good threads on the LM-1 Innovate site about lean cruise fueling using +15 AFR's

Well it has been awhile since I flew but I don't remember it quite like the article. In the plane I was taught in we didn't have head temp or a/f guages only the throttle and a mixture adjustement. We took off full rich at cruise leaned to peak the backed off to the rich side. Certainly didn't go lean of peak. Then went full rich again for landing. Problem is I have no idea what a/f mixture was peak as we didn't have a gauge only the tach. The article you posted suggests going way past lean of peak and eventually the cylinder would cool down. Sorry don't have enough balls to lean out an aircraft engine that far. The first step out is a *****.

Anyhow tried a couple of things last night.
First I set my initial timing to 5 degrees (car would not start cold it was very unhappy even knocking during tring to turn over) didn't try that one long. Went back to 12* and it popped right off.

Second tried leaning out the idle. I currently run around 13.5:1 I tried going to 14.5:1 and the idle speed of the car dropped significantly idle was no longer smooth and stalled on acceleration. I was able to take out some of the stuble with acceleration enrichment but not all and mostly the enrichment just made it go rich after the stall. Went back to 13.5:1 and idle speed picked right up also tried going richer mostly due to other enrichments car would run down to even 10:1 but not very well however better than lean. At least for my car and confirmed by several others the target for at least the ITB setup is 13.4-13.7:1 at idle.
This is also the setting I use for cruise at this point. I need an assistant to slowly lean out the cruise and see where the best is. Certainly don't want to go richer at cruise. Even going to 12.5:1 at cruise will show a significant reduction in speed.

Still pretty convinced that 12.5-13:1 is the number for WOT would really like to have more opinions that just psalt and myself don't know psalt but I am not very authoritative. Untill confirmed by some others I will edit the first post to include the lean values but with a disclaimer to not confirmed.

Dfink wrote,

Problem is I have no idea what a/f mixture was peak

14.7:1 is peak. Lean= higher temp is only true when you are rich of stoich.

Some of your comments do not make sense to me. Are you adjusting injector pulsewidth or a closed loop AFR target ? No system can hold an AFR under cruise, only dither back and forth over a target. You usually have to look at the correction table and dial in the pulsewidth to get the correction factor below 5%. Have you verified with a timing light that what the computer knows as TDC actually is TDC ? The best AFR for WOT under load can only be determined by max output on a dyno or with a stopwatch. Low 13's is usually LBT, anything in the 12's is a safety factor for cooling, nothing below 14.1 actually burns. You seem to be searching for a set of "ideal" specific numbers and it just doesn't work that way in my experience. If you are tuning a road car exempt from emissions, you want a steady idle, good throttle response, a lean cruise with a lot of load based ignition timing (like vacuum advance) and a safe AFR under WOT. The reason full load AFR is discussed more, it that it is really the only time it matters.

dfink,

As you know I've spent a lot of time tunning stock Motronic 3.2L system. I have solid understanding of how the stock system works and it's maps. I think you can learn a lot by understanding the stock motronic system before you start tuning an aftermarket EFI.

I will tell you first hand that the real trick to power and throttle response is in the timing maps and not so much the fuel maps. Of course the fuel maps also matter but they are 2nd to the timing. You should first decide on your timing map(s) before you touch fuel. A flat timing map will not get the most out of these motors.

The 89 chip is the most aggressive chip Porsche produced for the stock 3.2L and if you inspect the maps you'll learn a lot from it. So here's the 89 timing maps, the stock chip has 3 of these: 1 for idle, 1 for PartThrottle and the last for WOT:

http://forums.pelicanparts.com/uploa...1232814957.jpg

Idle ignition, not really that interesting just note that they set idle at 3deg BTDC or so. The thing to know is you can get idle speed control by simply advancing idle ignition if the RPMs drop below the target (like if AC comes on). You can do the inverse to bring idle down if it goes above target. In my car I have idle at 920RPMs with ign at 5BTDC if idle drops below 850rpm I start to crank timing up to as much as 10BTDC. you get the idea.

Then the WOT ign map: this map is very important and you should start by matching these 89 settings more or less. For starters simply set the WOT ign to about 25BTDC from 1000RPMs all the way to red line, this will give you decent power at WOT. Now once you have your AFR set at WOT to around 12.8AFR then start cranking the WOT ign map closer to 30BTDC, I would not go over 30! these cars have NO knock sensors. But at 30BTDC you should be using 93 octane fuel. For street driving and easy on the engine I'd use 27 or 28BTDC.

Now for the PT ign map: this is the hidden gem of tuning and many tuners simply get this worng! A flat PT ign map will have poor throttle response. Look closely at what the Porsche engineers did here, you will learn a lot. The load on the left 8% to 58% is kind of not right. Really think of the 3% as low-load and the 58% max load but not WOT, so just before the WOT ign map kicks in. So if you look at the last 58% row you find it matches very well with the WOT ign map and this is good to help with transition from PT to WOT. Same holds true for the 8% load row and the idle ign map (not exact but close enough). So the PT ign map starts like the idle map and ends like the WOT map and this makes sense. But look at the middle of the PT ign map, WOW! not linear at all. You can even see it in 3D graph form on the right. So the idea here is that at low load first 3 rows they sort of stay conservative. But in the center rows (16-21%) they really crank the ign timing into the 40BTDC range. Why do they do this? Simple, Throttle Response. This is so when you jab on the gas the engine delivers results. I'll tell you that this part of the map and these ideas is where throttle response comes from, but it's also coupled with Fuel Maps (topic for a future post). In my car this center area has timing in the low 50BTDC range, I don't suggest you do that for starters but I do suggest you try to match what you see in the stock 89 chip graph above.

Looking at the factory fuel and spark maps is a good starting point. It also helps to understand the emission control strategies and not copy them. All the OEM's target the EPA emission and mileage test for obvious reasons and sometimes they get pretty sneaky retarding timing at certain points, even using different maps when the A/C is on. The reason they are using 40 BTDC at 15-20% load is fuel economy at cruise. An engine under low load can handle a leaner mixture, this requires much more ignition advance because of the burn time, and it is not a problem at low load. This was the concept behind vaccum advance, add 5-10 degrees of additional timing under high vaccum, low load cruise and take it away as soon as the throttle is opened. You can also learn a lot by looking at the distributor spec on pre EFI motors, but with Porsche after 1968, timing was determined by emissions more than optimum performance. The idea of setting idle timing to 12 BTDC came from having to live with a 20 degree mechanical advance and wanting 32 BTDC at full advance. The later 5 BTDC setting was all about getting to TDC with vaccum retard to lower HC emissions for the curb idle test. With a programmable system these are not issues.

The AVWeb "Pelicans Perch" series of articles has some real gems. Alot of the information is applicable to the auto world..

The articles describe in lay terms a/f ratio, egt BSFC etc..

This one is good!

http://www.avweb.com/news/pelican/182084-1.html

Paul,

I also have Factory Euro Chip maps, do you think these where tuned for Emissions? Maybe it's a better idea to look at the Euro chip? I have inspect the USA and Euro and yes they are somewhat different but not by much. Even the Euro seems to dig deep for fuel and Ignition when you increase load demand for sharp acceleration. In the end it's just a good idea to understand the stock setup.

Thanks for the feedback.

Sal,

I don't know the Euro Carrera chip map, but if they didn't have a cat and the IM240 test, it would be closer to optimum. I think it had higher compression and a different fuel spec. Many of the US 911 road cars were detuned for low octane fuel after the 60's because it is such a knock sensitive design. Copying the factory timing from these models may not be so good if you have a modified engine, twin plugs or good fuel.

Is that 8%-58% load map, total timing or an offset from idle (static) ? I don't understand a $1336 offset, sounds like it belongs on Martha's tax return. Does it say that timing goes negative (-1.4 and -4.2), ATDC, when suddenly accelerating of idle ? I wonder if this is a "burst Knock" or throttle response issue ? I agree that timing changes can do a lot for drivability. Idle timing should be close to TDC, there is really no need for advance at idle on a properly fueled engine and it is bad for cranking. OEM's are now retarding the idle timing after start up to intentionally overheat the exhaust, in an attempt to get the cat up to temperature to meet the hardest part of the emissions test. Not something to copy. For part throttle cruise on a road car, you are just wasting fuel if you do not lean above 14.7 and have a load based advance above the 40's BTDC. There have been some interesting articles about the choices we have made about emissions and how they have increased overall fuel consumption. With a different emission strategy, fuel consumption could be much lower. I am not familar with ECU's with maps that target AFR's. It has to be irrelevent at cold start and during transitions.

That offset is simply the hex location in the chip where the map is located, ignore it. The numbers you see in the tables are real ign advance numbers, if you see a -1.4 for example that's a retard of 1.4ATDC, they really are that simple to read. Now in the real map on the chip they are keep in a digital format that is converted to real value via a formula. Not going into the formula here, but those are the real timing numbers already converted by the formula.

The Euro cars had no cat and where most likely not detuned in anyway, I'll dig a map up and show you soon.

As for going negative timing when accel of idle, yup that's what is says. But keep in mind the 89 cars where 880RPM idle so that says they do backoff some on timing off idle under sudden accel but they would only go -1.4 if the RPMs dropped as low as 800RPM. But you have the right idea they backoff timing under sudden accel at low idle, correct. In the end this area of the map really is not that interesting because how often do you gun the throttle below 1500RPMs?

The real interesting area is that big hump you see in the graph above 2500RPMs, I have played in this area a lot and will tell you it completely changes the car. The throttle response goes flat if you lower that hump and it really comes alive if you make it steeper. I'm simply giving you some ideas to play with in your EFI setup, try them.

The real interesting area is that big hump you see in the graph above 2500RPMs, I have played in this area a lot and will tell you it completely changes the car. The throttle response goes flat if you lower that hump and it really comes alive if you make it steeper.

Sal,

OK, you are interested in the "big hump" (like everyone else). The way I read this map is the steepness of the "big hump" is the rate at which you pull out timing when the throttle opens. I know you said the 8%-58% is not correct, but if it relates to manifold pressure (load) or throttle angle, the timing increase only occurs under 21%, which is light load. I doubt you ever get to 5000 rpm under 20% throttle, unless you are coasting, certainly not under acceleration or top speed. What kind of % are you seeing at 65 mph cruise ? I am used to seeing a 15-20% throttle angle at part throttle cruise, where timing needs to be advanced above the WOT curve. As soon as you step on the pedal (throttle response) the extra timing goes away. Most systems use a 30% throttle position to go open loop, when does the Carrera TPS go open loop ?

OK well now we are getting into some good discussions. Have not seen timing suggestions posted that high they may be out there just never found them.

I don't see why there can't be some sort of suggested range for the new tuner to shoot for. If you have been doing this for a long time you will ignore anything posted here anyhow. This really meant for the new guy with no idea to give some idea of what to shoot for and what is safe. Along with some discussion as to why.

For a couple of earlier questions. The electromotive system can do pretty much anything you want it to do. I can go open loop, closed loop, I can use the ignition to get the idle about anything discussed can be done.

My car has had the wide band checked against two different dyno setups and the ignition has been checked with a timing light. Perhaps I had an entry wrong and I will recheck but the car would not start at 5* I had to go back to 12* and popped right off. I will revisit my idle settings.

The PT advance issue is interesting indeed but needs to be mixed with the A/F ratios under those conditions. I could easily put those advances in my table. Car has been dyno tested and for me a WOT ramp up to 30* works the best. Higher numbers at the lower RPM range resulted in a loss of power and anything over 30 resulted in a loss of power. The twin plug never did ping.

dfink,

I simply think starting with the 89 maps just makes a lot of sense. I'll post the fuel maps soon. But not that much magic in those, simply the set the low load area (first 3 or 4 rows) to about 14.2AFR then the high load last row to 13.0AFR then the area that matches the 40deg ign advance simple gets about 13.2AFR.

The way to think of the rows in that table is the 8% is when you first transition from closed throttle (very low load) the last row 58% is just before you transition to WOT, my WOT switch kicks in at about 80% open throttle.

I know a little about open-loop in the motronic but my car is a Euro Car and I never run in closed-loop (no O2 feedback). But here is how the motronic gets out of closed-loop:
1) These cars do not have a TPS they simply have 2 simple switches (open or closed) one for idle which closes when the throttle plate returns to idle this switch tells the DME to use the idle maps. The other switch is the WOT switch and it closes when the throttle plate is about 80% open but you can adjust it's close point by rotating it. If this switch closes then we are using the WOT maps. If both switches are open we are using the PT maps, very simple.
2) Then if the WOT switch closes the motronic comes out of closed-loop and stops monitoring O2.
3) If idle switch is closed we are at idle and using idle tables the Motronic always goes into closed-loop here if CHT is in normal range, I won't talk about cold start for time being.
4) Then in PT maps (both switches open) the motronic has some advanced algorithms to determine if closed-loop is appropriate. First under normal cruise and light to moderate loads it's in closed-loop shooting for 14.7AFR. But if the motronic detects accel conditions (like jab on the gas) the code will take you out of closed-loop and really start looking at the PT fuel map which in many cases will drop AFR into the 13s, this is how it achieves accel enrichment. I don't fully understand all the workings of these algorithms because they never interested me since I'm always in open-loop in the Euro engine. But a common misconception is that in PT you are always in closed-loop this is not true! The DME evaluates the AirFlow via the signal from the AirFlowMeter compares this to the given RPMs and comes up with a load factor and if the load is very high and changing rapidly (jab on the gas) it comes out of closed-loop.

With all this said, I would always suggest tuning without monitoring the O2 sensor (open-loop mode). You only bring the O2 back in for fuel economy and really don't do this till you are happy with what you have.

Here's the other misconception: can I run my USA car in open-loop all the time? answer is sort of yes but only if you don't have a CAT. Basically the DME is designed to run either way just fine but in Open Loop your mixture most likely will be to rich and you will damage the CAT other than this issue no harm done running a USA car in open loop mode.

dfink wrote,

My car has had the wide band checked against two different dyno setups and the ignition has been checked with a timing light. Perhaps I had an entry wrong and I will recheck but the car would not start at 5* I had to go back to 12* and popped right off. I will revisit my idle settings.The PT advance issue is interesting indeed but needs to be mixed with the A/F ratios under those conditions. I could easily put those advances in my table. Car has been dyno tested and for me a WOT ramp up to 30* works the best. Higher numbers at the lower RPM range resulted in a loss of power and anything over 30 resulted in a loss of power. The twin plug never did ping.

dfink,

Sounds like you have the WOT maps set up properly. On a road car this is less than 10% of the time and cold start, cold running, warm up, acceleration enrichment, and cruise take a lot of time and trial and error. Cold start can take a long time if your climate changes, but once you learn what changes work and why, it is easier. The Carrera spark map is for a single plug engine and a twin plug map may need to be different. One thing is certain, if 30 BTDC is your best torque WOT timing, your cruise timing will be higher if you are looking for mpg.

Sal,

I was thinking about the big hump and your throttle response comments. I am always interested in the "why" certain adjustments have the results they do. Throttle response is a perception and I have experienced large changes with different manifolds on the same engine with small changes in output, so I understand it is very subjective. It could be that what your are noticing is that without the extra advance of the hump, more of the fuel is burning in the exhaust, doing less work and causing more throttle angle for a given cruise load. When you bring the advance up, more fuel is burnt in the cylinder, more work is done, less throttle angle is needed and when you step on the throttle response is improved. You would need datalogging to see if this was the case.

If you are tuning an ECU with a target AFR table, doesn't it have to be closed loop to make the corrections ? My experience is changing the injector pulsewidth tables open loop, then using closed loop to datalog the correction factors.

On my system anyhow and I think most work this way. I can run either open loop or closed loop. Closes loop simply allows the EGO to control the a/f mixture within a set of guidelines I can prescribe. If I stay open loop the computer takes the fuel table, then addes and or subtracts the various other tables to come up with a pulse width for whatever the current point on the map is.
My map is based on RPM for the X factor and Manifold air pressure for the Y factor. The table is 16X16 but the numbers are interpolated at I believe 256 points between each of the 16X16 squares. So rarely will you see the exact target that you have set on a square. In open loop you get whatever output you get, based on how the engine reacts to your specific inputs. In closed loop the EGO table is brought into play. In my case I have given the EGO authority to make corrections to 15% max. In this case the output should be somewhere around the a/f setting you have in the EGO table because the system is making correction to what is happening.
This can be used as a tuning tool especially for the new tuner because the engine will try to stay close to where it should be on a/f and you can use the correction factor to try and get within 5% +- on the correction values this is done by adjusting generally the V/E table.
To avoid having the computer take the engine lean at WOT you can set a cutoff point for the EGO and open loop at either a set rpm or a set MAP actually you set the MAP where the RPM cutoff is allowed. The system then goes open loop and runs just off the fuel maps. In either case the system is ultimately controlled by the fuel map which is the pulse width for anygiven point. The A/F table is only the target for the EGO correction in closed loop.
The stock system has a point at which it also goes open loop for WOT but also has a switch that tells the system the throttle is fully closed and goes to an idle mode. On my other car this switch makes a big difference in how the car idles. I am sure that scarceller could enlighten us more on exactly what this switch does. My electromotive system does not have this feature.

I would be really interested in the euro ignition map!

Paul the tuning I do is with the stock motronic and burning new chips, it's very crude. I do have a full WBO2 setup that logs the following:
- AFR
- RPM
- AirFlow via AFM 0-5v signal
- CHT in deg F
- MPH speed

The data logger has matrix analysis ability that lets me then see what's going on in the PT tables, it simply figures out what he AFR is for a given load (cell location) after I look at these results from a run I simply fine tune the AFR map. WOT tuning is much simpler to do by just logging the AFR in a 2nd gear run from 1000RPMs to 6800RPM (my rev limit is also bumped up to 6800). I could never have tuned the PT tables without the matrix analysis mode.

I understand some of the new EFI systems have this real cool ability to monitor the WBO2 AFR and auto tune the map for the target AFR. Way cool, but I just can't do this with the stock motronic.

So here are the fuel and ign maps for the 86 Euro, the 86 car was not as aggressive in WOT ign as the 89 but at least this is a 86 Euro not detuned for the US market and CATs.

I risk someone getting upset at me for posting these maps but here goes. I simply only wish to share what I know about the stock chips and setup in the hopes of helping others struggling with custom EFI systems. Please do not ask about any custom chips.

Ignition map:
http://forums.pelicanparts.com/uploa...1232913938.jpg

Fuel map:
http://forums.pelicanparts.com/uploa...1232913955.jpg

dfink,

If the idle switch does not make contact when the throttle closes the car idles like crap for 2 reasons: It's not running off the idle maps and is simply running off the PT lowest load row (8% row). The second and most important reason is that if the switch does not close the IdleControlValve does not function to maintain idle. That idle microswitch must close for the cars to idle properly.

Paul,

At 65MPH in 3rd gear I run in the 3000-3500RPM range and I can tell from my AFR that I'm generally running in the lo-load first 3 rows (8, 10, 13%) so long as I'm not going up any steep hill.

If I hit a 10deg or more hill it starts to dig into the center load part of the map and my AFR drops into the 13.7 range.

Also if just cruising along in lo-load 14.2 AFR, I suddenly tip-in on the gas for quick acceleration (but not WOT) I can very quickly tell I'm in the upper half of the map because my AFR snaps quickly to the 13.2 range. I have my fuel map setup so that the first 3 rows (lo-load) keep me at 14.2AFR then the last 2 rows (hi-load) are down in the 13.0 to 13.2AFR and the rest of the rows simply transition me from 14.2 to 13.0 smoothly, slowly getting richer and then riching quickly after center of the load table. So I combine fuel enrichment with more timing on tip-in and this really helps throttle response. I know it's seat of the pants but I also have created maps that don't do this and are simply flat and you really can tell the difference. Not only that I can see the effects via my data logger by simply looking at my 2nd gear 30-60MPH times (Cruising at 30 then tip in to 75% throttle) with each map on the same stretch of road.

Great thread!http://forums.pelicanparts.com/support/smileys/clap.gif

Sal,

Trying to absorb the Carrera timing maps.... the Euro vs US difference is, +0.8 compression, no cat and 2 or 3 RON higher fuel spec ? The fuel specs in the owners manual and spec book don't seem to agree, was there a different fuel spec ? They both wind up with 26 BTDC max which is knock limited or detuned to me, based on dyno tests of water cooled, hemi headed engines with similar VIA's. I'm sure these engines would continue to make higher output on higher octane or alcohol based fuels out into the mid 30's BTDC.

My point was that at a 65 mph cruise in 5th, that map (big hump) is pulling timing out when you open the throttle to accelerate.

Paul,

If you look at WOT ign maps over the 84-89 years you see them getting slightly more aggressive over the years which to me indicates the engineers where being very conservative with ign maps at first and then improved them slightly over the years. But even in 89 they still never went much above 26BTDC for WOT.

But you are very correct that power was left on the table and these cars certainly can push WOT ign in the low 30s but you MUST use 93 octane once over 29BTDC or so. I have seen some WOT tuned cars push 32BTDC at WOT but I think you are in detonation danger here especially if your car leans out for some reason. I personally would not push past 30BTDC in a street car. You have to trade off power with engine life and these motors cost $$$.

Now be very careful of your AFRs at WOT and in a up coming post I'll explain something else the Motronic does with AFRs and how the WOT AFR is designed to change based on intake air temp. The same exact chip will produce different AFRs on a 90 deg F humid day vs a 40 deg F dry day. Just think about what you think should happen to AFRs under these conditions? I'll post on this soon as folks have made big mistakes here by assuming the AFR is always the same on all days.

Sal,

The Haltech ECU's use a GM intake air temperature sensor and a correction map to alter the pulsewidth for air temperature correction. I don't think it knows about humidity.

I was thinking more of 105-110 octane ethanol fuel. It seems that cylinder head temp with the air cooled motor is the limitation, as DOHC water cooled hemis make best power out around the 36-40 BTDC range. Some of the early Euro 911's had 38 BTDC for max advance before the unleaded fuel spec came in.

Really great thread! One of the things we've not touched on very much is the difference dual plugging makes on the timing map. I've heard you should pull a couple of degrees of timing over single plugged maps because of the speed of flame propagation. Any rules of thumbs here?

A couple of things from the last couple of posts.

It is correct that the pulse width is a basically an absolute value. The injector is on for a specific period of time based on what point in the table is active. It is then effected by the various other tables for a total on time for any given point on the map. Air density will effect the final A/F mixture. Most systems I would think have manifold air temperature, some including stock have an altitude sensor, I don't know of a humidity sensor. In practice at least during closed loop operation the EGO correction should compensate for any humidity differences as it measures the output not the input. You would still be subject to the effects once the system went open loop. This is one reason I would like to put a readout on the dash. With the electromotive system you can set an input up with a resostat and dial in up 5% +- correction with the turn of a knob. You can also adjust timing in the same mannor.

Now for the twin plug question. Several posts through out my searches found that 24-25* was the max for a twin plug system. I and others have not found this to be the case. There was about a 6hp loss going from 30* to 24* at WOT 7000rpm. I found that under WOT I got the best results from a rather linear ramp up peeking at around 5000-5500 rpm. Jumping up too soon also caused a loss in the lower to mid ranges. So for my setup 30* appears to be the best. I tried to go to 32* and also experienced a loss of power. I never did get any hint of knocking. This was with a 12.5:1 A/F ratio and 10.5:1 compression ratio.

First, I don't have much experience with dual plug. But I have looked at the 993 ign maps and they do seem to reflect what you are suggesting.