I noticed a lack of information in the tuning forum and decided to post my notes. I hope this creates some more in depth discussion. Thanks to Demon and Warmonger as almost all my notes are taken from their posts. Please post any corrections/additions.
-SCT xcal2 Pro Racer Package (PRP)
-wideband 02 (2 most popular described below)
Innovate Gauge is really nice and ties right up to the LC1.
The LC1 has more outputs than AEM. You can plug right into the jack if you want to datalog with their software or an xcal2 even while you have it running the gauge.
AEM works and costs a bit less but I think the innovate offers more features.
You just buy a 1/8" phono jack and wire it to the analog#1 or #2 inputs on the xcal2 cable. The xcal2 should come with the cable you can cut the end off or buy a male/female adapter for the cable. The cable is a 9pin DIN input
LC-1/LM-1 Integration into SCT’s Xcal 2
SCT Pro Racer Edition Manual - The Basics of Tuning
CarTech/S-A design will be publishing "Engine Management: Advanced Tuning"
SCT has a PRP forum with all the value files and info you could hope for. You just need to have your PRP serial number (whatever the number is that you unlock the software, that is) and PM the Mod for that forum and it will become unlocked for you to use. The additional manual is well worth the added $ and is a must have IMHO
xcal2 prp video cd
alex pepper OBDII
stoichometric - The ratio at which all available fuel is combined with oxygen during the combustion process. This theoretically ideal ratio produces minimum emissions, however maximum power is achieved at an AFR 10-15% richer than stoichiometric, while maximum efficiency is achieved at an AFR 3-5% leaner than stoichiometric
Air-fuel ratio (AFR) - the mass ratio of air to fuel present during combustion. When all the fuel is combined with all the free oxygen, typically within a vehicle's a combustion chamber, the mixture is chemically balanced and this AFR is called the stoichiometric mixture (often abbreviated to stoich). AFR is an important measure for anti-pollution and performance tuning reasons. Lambda is an alternative way to represent AFR
Lambda – the ratio between actual air/fuel ratio and stoichiometric ratio. Lambda of less than 1 is rich, and greater than 1 is lean.
wideband o2- will give a linear output for the entire range of A/F ratios that you can possibly see coming out of the engine
closed loop - refers to those times when an EFI computer is using the feedback on the mixture provided by the oxygen sensor to effectively control the injected amounts.
Duty Cycle (DC)– A number indicating the amount of time that some signal is at full power. In the context of an ECU, duty cycle is used to describe the amount of time that the injectors are on, and to describe the “hold” part of the peak and hold injector drivers
This is probably the basic list and covers most requests
-throttle position absolute
-maf AD counts
-airflow in #/min
-open loop flag
-imrc state (if imrc involved)
-Long term fuel trim bank 1
-long term fuel trim bank 2
-Short term fuel trim bank 1
-short term fuel trim bank 2
-O2 sensor bank 1 forward (or upstream)
-O2 sensor bank 2 upstream
-intake charge temp
-knock sensor retard
You need to do both (steady throttle and WOT). At idle, at light cruise in 3rd gear, and then a 3rd gear pull from a lower rpm.
During your light cruise datalog runs, pick rpms that are easy, such as 2000, 2500, 3000, 4000 rpm so that you have several runs that represent different airflows and throttle positions.
Then the full throttle run from say 1500 all the way to redline in 3rd gear will show how the fuel system is metering in WOT mode.
The cruise runs will show how your O2 sensors are working along with your MAF and of course the fuel trims will help determine how closely the tune is matched.
Find an out of the way street. Sit in neutral turn on the datalogger and rev the engine up in about 750 rpm increments. Should be about 6 reference points. This will show how to tune your idle and cruise. Then do a quick run through 1st and 2nd up to about 5k. If you have room get third. Turn off datalogger. You will be stunned how fast it will ramp up to 5k.
For the full throttle runs, data log the following:
injector duty cycle/pulsewidth, load, tps, rpm, IAT, o2 sensor voltage just in case on both banks, fuel pressure, maf flow (#/min would be nice), maf volts, degrees advance on timing
60% positive TPS movement from base.
Base is set when the PCM powers up. (Normally around 18-20% but it's all calculated from TPS voltage)
Now that DOES NOT mean 60% movement of the accelerator pedal.
Base is 18-20%
Max is 92-94%
So the range is ~74%
Therefore that would be about 81% depression of the accelerator pedal to engage WOT
Intake Manifold Runner Control:
The IMRC adds 10-14 degrees above the base timing curve.
Without it you can probably add at least 5% top the base timing below IMRC and smoothly transitioning to upwards of 15% increase as you go above 4000rpm. That would be my guess for a car with no secondaries, NA on 10:1 compression. You of course have to adjust that based on your own compression ratio and/or boost/nitrous if applicable.
There is NO IMRC adder when not at WOT.
The IMRC adder does not apply if the IMRC is closed.
The IMRC is closed below 4100rpm unless at WOT. Above 4100rpm then the IMRC adder still only is added when the IMRC is open.
You will not get any Timing or Fuel bump before the IMRC point programming in the PCM. (SVT is 3400rpm & stock is 3800rpm at WOT - other times both vary but by 4100rpm they are always open)
Stock setting is, when above 4100rpm no IMRC unless +45% from neutral throttle position. It does not scale the timing!
The IMRC adder is a set number (dependant on other variables) as set in the IMRC_spark_add_base_spark table.
The adder however is always 100% of what is set in that table.
You can datalog this all day long. As soon as that IMRC opens you get a "set" spike in timing. There is no "partial" IMRC opening or timing scaling for partial IMRC opening.
So in conclusion, Timing advance is scaled slightly per RPM, jumps up +10 degrees at 3400 to +11 around 3900 and stays there.
IMRC opening is scaled from 3400 rpm with activation at WOT at 3400 to down to open at any throttle position by 4100 rpm.
So at half throttle they won't open until 3600rpm at 1/4 throttle probably won't open until 3700. ETC
Your statement that if the RPM and TP reach the levels set in the code the timing adder will be added is correct. However they are added because the IMRC actuates. If the IMRC trigger switch does not tell the PCM the IMRC plates are open then the spark advance never happens. Also the timing advance is delayed by the actual opening time. Once it receives that signal then it adds the 11 degrees or 10 degrees of timing. I usually just skip the 11 degrees part because it only applies from 3400-4100rpm.
Either way it's an all or nothing timing boost. Nothing is scaled. That was my point of contention with what you seemed to be stating
With the correct tuning you can completely remove the IMRC.
However "correct tuning" means the tuner has to know how to do it.
The PCM goes into limp mode otherwise.
Also it's not just telling the PCM to work without the IMRC connected but also knowing how to tune the low rpm range without the IMRC adder. The PCM has a timing limiter in it when it doesn't see the IMRC.
Don't worry so much about the knock sensor. Leave all the settings on it stock until you get the tuning close to done. If you find that you are loosing too much power during the dyno tune due to the knock sensor retarding the timing, THEN would be the time to adjust sensitivity. you will want it to work at the level that the OEM tuners felt was safe.
The sensor has nothing to due with the amount on timing that is removed. That is preset into the PCM programming, it's more like 3-5 degrees off the top and gets worse from there "knock" dependant
A properly functioning oxygen sensor in a properly running engine should be rapidly switching from .1 volts to .9 volts.
Also, the sensors should bounce from rich to lean and back and if you graph the signal it will look like a sine wave.
If your O2 sensor voltage is .2v and staying close to it, it would be signifying a lean condition.
Also use as diagnostic tools to compare upstream/downstream performance and bank to bank performance
Intake Air Temp sensor:
The IAT has to read over ~150d before it pulls 40% timing. (and it sure better for the engine's sake)
The 4 points are: 0, 76, 140, 160
76 degrees (default) and the PCM call for a +20% timing increase (based on the base spark tables - figure a 2-4 degree increase (which is miniscule really) for the SVT program - less for your's since your base tables are likely half of a stock SVT
IAT does not affect fuel trim. Only spark advance
Engine Coolant Temp sensor:
in the typical driving operation range the ECT affects timing more than the IAT (hot air) does.
ECT timing pull is
-10 at 200
-20 at 220
-40 at 230
-60 at 254
-80 (i.e. default for bad sensor or maxed reading)
The primary fans don't kick on until 216d
The secondary fans come on at 224d
or -18% timing & - 22% timing respectively.
That's just the straight timing pull. There are many multipliers based on temp via load & rpm as well.
That's probably 10 to maybe 20 HP & TQ lost. Hard to quantify since I've never dyno'd the power loss from losing the majority of your spark advance
The PCM clears OL at 120 degrees ECT.
The PCM enters adaptive fuel control at 140 degrees ECT
When your throttle position goes less than full throttle the PCM will attempt to advance the timing to clean up the fuel after a full throttle run.
Timing will always spike when the pcm sees a deceleration. Spiking the timing under decel is emissions programming to clear the cylinders.
So you get spikes like that if you press the thottle and let off.
When you go full throttle your timing will drop down and then slowly climb as rpm climbs. If you mash the throttle and then let off a little bit, you will get a quick drop and then a spike before the timing will drop again and level out.
lean spikes at shifts are normal for a manual trans. When you're coming out of the throttle, your fuel and spark are effectively shut off so all you'll have will be inlet air moving through. as the engine will go rich then lean after the throttle snaps shut
A MAF voltage of 4.26 volts on a duratec means you're pulling in close to maximum airflow
The main concern for tuning on your OBD-II car is wide open throttle, the computer will compensate for most other adjustments below WOT that you make.
Fuel trim tables:
The PCM has a set of tables and modifiers that uses to determine fuel delivery for any given situation as a baseline. But, the PCM also monitors the air/fuel ratio using the oxygen sensors in the exhaust to verify that the fuel delivery is what it expects. Due to build variation in every component in the engine, and changes in wear and buildup that occur over the life of the engine, the actual fuel requirements for a particular engine are determined by taking the base tables, and then taking what the oxygen sensor says and using it to modify the fuel delivery slightly to optimize emissions. The resulting modifier value is stored as short term fuel trim. Over time, the PCM records trends in the short term fuel trim, and adjusts the long term fuel trim value to accomodate it.
Fuel trims are basically what the PCM uses to adapt fuel delivery to the small differences between engines, and the changes that occur over an engine's lifespan.
A lean code gets tripped when the PCM goes beyond 30% fuel enrichment for 3 straight driving cycles.
The PCM only uses the O2 as an indication of unburnt fuel to alter it's adaptive fuel trim. It does not use it as a individual catalyst to trigger a lean code. they are not accurate enough to work that way. Especially away from stoichometric.
However they are accurate enough to tell the PCM if it is running around stoich (the O2's peak albeit small efficiency range) and therefore is an integral piece in how the PCM's adaptive fuel trim works.
On a properly running engine (I.E. no leaks) both bank's long term fuel trim will be nearly identical.
Notice I stated Long Term fuel trim not Short Term fuel trim. There is a big difference here.
The injector pulsewidth refers to how long each injector is open for each time it delivers fuel. You can take this number and the size of the injector and the number of injectors and determine the total amount of fuel flow for a given number of engine revolutions. injector duty cycle refers to the relative difference between the injector pulsewidth and the amount of time the engine takes to complete its cycle (the full 4-stroke cycle). Exceeding 80% duty cycle is not generally a good idea
Also it is a good thing I could easily change the high & low slope in the PCM when I changed to the 24lb injectors. (Using a MAF to change injector size by "fooling" the PCM is not the proper way to do it at all!)
I increased the low slope setting in comparison to the high slope setting to help shorten the low rpm, light load, and idle pulse width and keep excellent drivability.
Though if I needed to I could just have shortened the minimum pulse width limit in the PCM calibration too I suppose.
However the way I did it actually improved my fuel mileage in cruising and light load situations.
Air fuel ratio:
Whenever your car goes into closed-loop your AF should bounce between richer/leaner. In open loop the computer relies on the narrow band O2 and it will try to maintain a certain AF
Also, just because it runs leaner that stoich under cruise is not necessarily a problem. It is fine to see 14-16:1 under light cruise.
expect to see 14-15 at idle. When you go full throttle you should see it settle down and stop bouncing. Expect anywhere from 11:1 to 13:1 under full throttle
The A/F ratio is in a constant state of change. That's why it's called adaptive fuel control.
The target number for normal load (40-60%) is stoich. 14.7
No load/engine braking has no fuel trim. You can see 20.9% oxygen (open air)
Low load is leaner then stoich. (15-16)
Moderate load is slightly richer. (13.5-14.5)
WOT is richer still. (12.8-13.3)
Boosted WOT is even richer. (12-12.5)
Wide open throttle:
The PCM at WOT runs more timing and fuel, any trickery to de done here in terms of telling the PCM to run at WOT before the approx 81% movement of the accelerator pedal? Say at about 55-65% accelerator pedal movement.
Yes and no. Mainly NO.
Timing is based on engine load.
Fuel is based on engine load.
WOT multipliers for both are set at 1 so that really does nothing.
That means without the load above a specific limit you are not using the maximum tables anyway. (actually load is broken down into 8 levels even)
Even if you do get a small fuel increase for passing the WOT point. (think of it like an accelerator pump on a carburetor - it's not sustained)
So there is no bonus to getting to WOT faster without actually having the load tables on the maximum level which of course is only achieved with "more" airflow across the MAF.