So, in this post I’m going to reveal what power secrets your car has for you, how you can actually listen to it, What it’s saying to you and easily understand what it’s saying, all to harness the incredible power potential that’s been hiding there all along!
After the release of our video explaining how to create dyno charts from Datalogs, we were asked to go further in depth on the rest of the terms you see within them. So, let’s go through the common terms we use for performance tuning your car so you can understand and even interpret what’s going on yourself.
There are many tools you can use to “listen to” or datalog your car, but most of them only support generic OBD2 values. In some cases that’s perfect, however, for tuning we prefer to have a more in depth view of what’s going on. This requires special protocols the manufacturers use that open up a plethora of values for us to get an amazing picture of what’s happening and adjust accordingly.
For the purposes of this video, we’ll use Durametric in these examples since it mimics the factory PIWIS protocols and layout. The Cobb Accessport also does an excellent job with the logging, and even provides additional parameters by modifying the values your ecu typically outputs. And although they’re purely OBD2, Hptuners and ScanXL are a few other logging tools that fit nicely in any tuners toolbox.
So, let’s get started!
If you’re running a 997.1 Turbo and have followed the directions for datalogging your car from our website FAQ section at protomotive.com you’ll end up with a spreadsheet with a header looking something like this.
And from that we can generate meaningful charts and graphs to visually demonstrate what’s going on with your car. Here’s a few charts created from this exact datalog. This particular log was sent to us to assess the performance of another tuners kit installed on a car and advise them what to do next. If you’re already an expert on these, take a quick look at these and let me know in the comments what you’d do if it were your car. If not, that’s why you’re here right? We’ll go through these in detail below to interpret these and help make it easy to understand what it is your car is saying. This log and these charts are from a 997 dot 1 turbo with a basic bolt on kit running 93 octane, upgraded Vgts exhaust, intercoolers and Y-pipe, so nothing crazy, but there’s a few problems hidden in here.
What is RPM? What does RPM Mean?
Let’s Start with the first column, Engine Speed, otherwise known as RPMs.
We all know and love watching our tachometers race towards redline in every gear, but what is it actually telling us? Well, RPM’s of course. But having heard that millions of times throughout our life, what is it?
RPM’s are Revolutions Per Minute. Meaning in one minute’s time, the engine revolves or rotates x times. That x is the number you see on your tach. In the above datalog, the 732.75, 742 and so on in the first column are the engine speed or RPMs, which is telling us the engine is sitting at idle, but even at idle is already whirling around over 700 times in one minute! And by redline, you’ll be seeing 10x that number or 7000+ revolutions in one minute. Why is this important? Well the combustion process produces pressure on your pistons, pushing them down in the cylinder. This in turn pushes on the connecting rod which is connected to your crankshaft. This action produces torque, not power. But how fast this action occurs is where your power comes from, or RPMs! So while producing the same pressure in the cylinder, which creates the same torque, you will make 10 times the horsepower at 7000 rpms than you would at 700 rpms. That’s also why F1 cars scream to over 20,000 rpms with those tiny engines but make tremendous power! Or why the massive diesel engines make massive torque at lower rpms while not making much power in comparison.
What is Engine Load?
Ok, next up is Engine Load. This is a calculated value that’s representative of the torque your engine produces. The higher the Load the more torque your engine will be producing as long as all the other parameters are in check. In general, approximately 100% load is about wide open throttle on a naturally aspirated engine, but not always. The little boxster engines will show barely 85% load at wide open throttle while a full out gt3 engine may be showing almost 130%. This has a lot to do with the volumetric efficiency of the engine and how much torque or load it can produce without the assistance of turbos. So if 100% load is wide open throttle on a naturally aspirated engine, then 200% load is close to 1 bar of boost on a turbo engine. But some dataloggers get stuck at 191% load, and that’s due to the value they’re looking at in the ecu. There are 8, 16 and even 32 bit values flying around in there. And the ones stuck at 191% are going to be your 8 bit values. They’re stuck because 8 bits can only represent 0 to FF hex or 0 to 255 decimal. And the 8 bit also limits the resolution, kind of like an old Vcr tape compared to an awesome 4 or 8k display. So be wary of that, and the fact that you may be running a lot more load, but simply unable to see it due to the limitation of your logger. Durametric has no issue with this load value and it’ll keep going up till your MAP sensor gets pegged since that’s primarily where it’s getting its basis from. On Mass flow cars it’ll instead take the mass flow, divide it by the rpms and come up with a load value. Hmm, that kind of sounds like the horsepower vs. torque calculation. It’s amazing how all these little puzzle pieces start to fit together.
So why is Load important? Well… It’s the basis for most of the axis in tuning where we have rpm vs. load vs. timing tables or rpm vs. load vs fueling tables. Aftermarket ecus may use rpm vs map vs timing instead, but they’re very closely related to each other. Also the load is where the injection timing is calculated from along with a few corrections. So, knowing what your load means in relation to boost and torque can help you understand if things are coming along well in your tuning.
What is Intake air temperature?
Intake-air temperature is next up. Well sure, even the weatherman talks about this one all the time, but in a turbo car it can mean the life or death of your engine! Intake air temps out of control can be oversped turbochargers, massive boost leaks, poor intercooling, terrible heat soak or maybe it’s just really hot out…. In the 997.1 Turbo and 996 turbo the intake air temperature sensor is part of the map sensor and located right in front of the throttle plate, so it’s not measuring ambient air temp, but instead it’s measuring the actual intake air temperature going into the engine after the turbos have done their work, the intercoolers have cooled the air to the best of their ability and maybe your meth system is working hard to cool everything back down as well. And the intake air temp sensor will tell you how efficiently that’s all working. Inside the ecu is even a value called intake air temp HOT. And when the temps pass that threshold the ecu goes into a protection mode. So the cooler the better! In many cases for each degree of air temp we can reduce the temps you can make a hp. The cooler it is the less prone the engine is to detonation. The cooler temps even lower your exhaust temps which help out your vgts by keeping them out of danger from seizing the vanes when overheated. So be sure to monitor your intake air temps closely. Not only sitting still, but through the course of a dyno pull, road log or even on the race track and using that information to improve your cooling the best you can because lowering your intake air temps is vital to performance, power and reliability!
What is ignition timing or ignition angle?
Oof, Ignition Angle or Ignition timing is next…. It sounds simple but boy is that a loaded one, maybe not as bad as your wife asking if these pants make her butt look big, but there’s sure a lot to this one!
Basically put, ignition advance is the angle relative to TDC or Top Dead Center where the spark plug will spark and start the combustion process. Too early and you get knock. Too late and you have poor performance and high exhaust gas temps or EGTs. Finding that ideal timing is like getting the ingredients to the special sauce at your favorite restaurant. There’s a lot of science to it, but so much it can seem like black magic instead! And on a turbo car, finding that perfect balance between boost and timing can be quite heavenly, but getting it wrong and you have terrible knock causing blown head gaskets, holes in your pistons, bent rods and other things not so fun….
Luckily, these ecus have very nice knock sensing and cylinder specific knock adaption to help out. So without damaging the engine you can experiment a bit without so much worry. And tuning the timing can be a process of moving the whole curve up or down, logging and monitoring the results, then adjusting again. Then as you find the ideal timing for a specific range, you keep narrowing down the range you’re adjusting.
Amazingly, on 997 and 996 turbo engines a single degree of timing can be worth 20-25hp! So we really want to be in that ideal range when adjusting the timing.
You’ll want to look for sharp decreases in the timing during a run. That’s typically the ecu adjusting for knock and sharply dropping the timing to protect the engine. It will ramp it back in over a couple combustion cycles then drop again if it senses knock again. Even though the ecu is protecting your engine, the knock adaption tends to over correct to immediately stop the knock event and potential chaos. So, you’ll more want to adjust the timing till there’s very little to no adaption going on.
Now, timing does have ideal ranges. I had read a while back in the 4 stroke performance handbook by “author here” that the ideal timing was somewhere in the 18-21deg before tdc. Now that will change according to compression ratio, octane of fuel, temps, combustion design and boost but there is still an ideal. So just reducing the timing way down so you can ramp the boost up without knocking doesn’t necessarily make more power. And since timing and boost both directly relate to the torque being produced, you will find optimal boost vs. timing settings. Many times an engine is far happier with lower boost allowing the timing to be in a more ideal range giving you better overall performance, lower intake air temps, lower stress on the engine and what we refer to as a “Happy” engine!
Well, discussing timing alone could be an entire book or thesis paper and most certainly has been! And since this is more on What these values mean vs. a total tuning video let’s move on!
What is Injection time? What does Injector ms. mean?
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Injection time: This one’s not so bad. The injection time or Injector ms. which stands for milliseconds is the amount of time your fuel injectors are open in two complete revolutions of the engine for sequential injection engines and one complete revolution of the engine on batch fire engines. DFI engines are a whole new batch of crazy when it comes to injection time since they’ll go through many different modes of operation that utilize very different firing patterns than our port injected cars.
So, the injection time should relate very closely to your Load. If it’s too far off you’ll typically also notice your fuel trims are whacky trying to keep up with the deviation. And your load relates very closely to your torque, thus the dyno video we did where you can back calculate your hp based on your injection time knowing other factors such as injector size, brake specific fuel consumption or BSFC, fuel pressure, fuel type like pump vs E85 and number of fuel injectors. You’ll also want to monitor your injection time to be sure you’re not running out of injector! The ecu will continue to try to put more fuel in by driving the trims sky high even to the point where the duty cycle is well above 100%. But you can’t produce more than you have, and when that’s the case you either need to lower the boost, get bigger fuel injectors, check and/or raise the fuel pressure, or make sure the fuel pump or lines aren’t causing the restriction.
Too large of an injector can also be an issue on low speed and idle performance since fuel injectors maintain a linear flow rate relative to injection time only down into the 1.0 ms range or so. Below that they become very unstable and give you unpredictable results. We see this all the time with customers installing ID1300 and ID1700 injectors on their 997.1TT’s and wanting to run pump fuel. At idle, you’ll see the injection time all the way down in the 0.4ms range. And with the non-linearity of these injectors in that range, the o2’s go bonkers chasing the trims around causing the engine to stall when the trims shut off on fuel catch after fuel cut on decel. We talked about this at length in our video Engineering Explained: Fuel Injectors, pumps and more! (Tech Talk), so be sure to check it out!
What is Camshaft Deviation bank 1 and bank 2?
Camshaft deviation bank 1 and bank 2: Ha, we get to cover two in one shot and these are pretty straight forward. Well, as straight forward as something this technical may be able to get… Anyhow, these two values are describing what the computer is expecting to see from a perfectly timed camshaft to the actual camshaft timing. On a 996 and 997.1 Turbo these are for the intake cams only. Where a 2010 Gt3rs has sensors and adjustment on the exhaust cams as well. Unfortunately, the 996 and 997.1 turbo don’t even have sensors on the exhaust side, so if those are out of time you have to figure out the hard way if they’re timed wrong.
These values are only allowed plus or minus 10 degrees. Beyond that they’ll flag codes P0016, P0018 or P0020 for cam to crank synchronization errors. And anything beyond a few degrees difference between these two will cause your engine to run poorly since the cam timing directly affects the volumetric efficiency, torque, load then fuel trims. And if they’re off too much side to side one side of your engine is performing very differently from the other side. The cams in the earlier example are -1.48 degrees and -4.44 degrees. So even though both are slightly retarded the difference between them is about 3 deg. Where if one were +1.48 and the other -4.44 you’d be out nearly 6 degrees and the engine would suffer.
So if you’re having a hard time setting your cam timing by the shop manual procedure and a dial indicator to find tdc, head over to our web store and grab a crank lock down tool. Your engine will be happy you did since you’ll be able to nail the cam timing every time!
What is Actual and Nominal Camshaft angle bank 1 and 2?
Actual camshaft angle bank 1 and 2 along with Nominal camshaft angle bank 1 and 2 are the next values we see in this log. While bank 1 refers to cylinders 1, 2 and 3, bank 2 is referring to cylinders 4, 5 and 6 on the Porsche 911 flat 6 engine. The Actual camshaft angle is telling us how far it’s being adjusted from its base value, and not the actual angle in the housing as that’d be moving so fast it’d make my eyes go wonky! The Nominal camshaft angle is referring to a setpoint by the ecu or a target camshaft angle. Ideally you’d want the actual angle to be dead on top of the nominal camshaft angle values. But given that they’re flying around in the engine and being controlled by hydraulic solenoids and actuators, they’re doing a pretty good job just trying to keep up! However, if they deviate a bit too far for a bit too long you will get a cam error code like a P0011 or a P0021 depending on if it’s Bank 1 or Bank 2.
While these target values are tunable, on a stock engine you aren’t going to find much there. With some upgraded cams, port work, altered intake manifold or other mods, you can rework the cam target tables to have a more ideal torque curve.
However, these are generally being logged to look for slipped cams on the 997.1TT, or even bad rings on the ends of the cams causing leakage between the hydraulic passages. And by monitoring or graphing these values you can see if you have a lazy camshaft that may not be flagging an error just yet.
A value of 0 corresponds to a fully retarded cam, where a higher value will be the camshaft advancing. 996 turbos, 997.1 turbos and even gt3’s all have differing amounts of total cam movement, so you’ll need to be familiar with your own vehicle to know exactly what to look for here.
The next two columns have an odd looking value called multip. correction of mixture adaptation and (B). these are what you’d see in a standard obd2 scan tool as Long term fuel trim values. A value very close to 1.00 here is where the ecu is most happy. And that value would be telling you that the ecu isn’t having to do any correction, or something is broken and your o2 trims are turned off. When they’re off, they’re simply stuck at 1.00. So, as long as they’re a non-zero number you can be pretty confident they’re functioning. A lower value means the system is pulling fuel where a higher value means it’s adding fuel to the base mapping. It’s doing this in response to the target lambda or air/fuel value. And the long terms are slowly absorbing the short terms trying to keep them happier around 1.00 as well.
If you see one bank pretty far off from the other. Far off being more than 3 or 4%, you’ll want to go looking for problems. Bank to bank deviations in the fuel trims like that can come from many things. Dirty fuel injectors, intake manifold leaks, exhaust manifold leaks, improper cam timing or simply a bad o2 sensor.
What is Retardation Cylinder 1? What is Knock? What is Knock adaption?
Retardation cylinder 1 is the next column over and is referring to the knock adaption value the ecu is applying to cylinder 1. Normally you’d want to log Retardation cylinder 1, Retardation cylinder 2, Retardation cylinder 3 and so on up through 6 to get individual cylinder retard for each cylinder. The Cobb Accessport does this well. As does the Factory PIWIS. However the durametric seems to be simply duplicating cylinder 1 6 times… oops. Pretty annoying and it’s been reported so many times I’ve lost count. However, even the single value gives you an overall picture of the knock retard going on in the engine. Although having all the values does allow you to do individual cylinder knock threshold tuning and a few other fancy things…
Generally you’ll want this to be 0, since knock is not our friend. But you’ll tend to see a lot of knock in the sub 2500 rpm range and typically when you’re rolling into and out of the throttle. This is mostly drivetrain noise it’s hearing vs. actual engine knock, so don’t get too scared from that. However, in the higher load and wide open throttle conditions, when you see a bunch of knock like in the example I showed earlier, you’re certainly going to want to lower the boost, decrease the timing, enrichen the mixture, or get a better fuel with higher octane in there or you’ll be asking for damage!
What is “Actual Throttle Plate angle” in a datalog?
Actual throttle plate angle is the next column over and is pretty much exactly what it’s telling you it is. No hidden agenda here! On some cars, 100% is 100% while on others 100% or max throttle angle may be limited to 85. What we’re typically looking for here is throttle closure since we’re dealing with e-throttle cars and the ecu is controlling them based on many, many conditions and not simply where your foot is on the throttle pedal. So, if you’re at wide open throttle and you suddenly see the Actual throttle plate angle closing down, then maybe reopening a few rpms later, that’s usually caused by the ecu sensing something isn’t right and putting the engine into a protective mode.
What do Fuel Trim mean value bank 1 and 2 mean? What are Actual lambda value bank 1 and 2?
Next over are some more fueling values: Fuel trim mean value bank 1 and 2 and Actual lambda value bank 1 and 2. The fuel trim mean value bank 1 and 2 are what you’d normally see called short term fuel trims in an obd2 scan tool. A value of 1.00 is telling you that the ecu is not having to trim the fuel from the base mapped values in the tune to maintain the target lambda. Even though we’re not logging the target lambda, it is another variable you can look at. The short terms vs. long terms we explained earlier are kind of like short term and long term memory. Although I certainly hope that my ecu as it’s aging doesn’t start losing it’s short term memory! Jokes aside, the short terms are an immediate value and are taking care of the trims to maintain the actual lambda according to the target. And if these are consistently high, the long terms will absorb those values every few seconds to try to keep the short terms closer to 1.0. So the short terms move fast and the long terms move slow. The Actual lambda values bank 1 and 2 are just that. They’re the air/fuel ratio or lambda value directly from your wide band o2 sensors. They’re telling you the aftermath of all the work the ecu did preparing the fuel calculation for your engine. And now that it’s burnt, the o2’s are telling you what happened. In the idle and light throttle you’re generally looking for a 1.0 lambda value which is 14.7/1 on pump fuel. While at heavier throttle positions or wide open throttle you’ll see it moving downwards which is a richer condition. A 20% rich condition or 0.8 lambda is a nice target for most turbo engines. Where naturally aspirated generally target a leaner lambda value since they don’t need so much extra fuel for keeping things cool down there.
What is Pressure ah. of thr. plate fr. press sensor? What is a MAP sensor? How do ecu’s read Boost?
And in the last column in our example is another odd looking value: Pressure ah. of thr. plate fr. press. Sensor or simply put BOOST! In the 996 and 997.1 Turbo there’s only the single map sensor and they’re in front of the throttle plate and not actually in the manifold. Where the 997.2 Turbo and 991 Turbos got 2 sensors. One in front of the throttle body and another in the intake manifold. These are absolute pressure transducers that read a zero value at absolute vacuum. So at sea level you’ll see 1000 in this column while just turning the key on , or sitting at idle. While up in the mountains it’ll only be maybe 800 to 850 since the air pressure is much lower up there. Then if you’re running 1 bar of boost, you’ll see a 2000 in this column at sea level, or only 1800-1850 up in the mountains of Colorado. So even though you’re running 1 bar, you can see that the absolute pressure is much lower and will have a huge effect on your power up there. You’d actually have to run 1.2 to 1.25 bar up there to get close to the 2000 at sea level, and even then your power still would be down due to everything having to work so much harder to get there! Now the PIWIS and Cobb Accessport also have a Setpoint or Nominal Boost value you can log. That combined with the actual boost will show if you’re achieving the setpoints or sometimes exceeding. These values combined with wastegate duty cycle on 996tt and actuator position on 997 turbo can help dial in your boost control very nicely.
Well, that’s all the values we had in this particular datalog. Even though there are tons more, these are some of the primary ones used for monitoring the overall running condition of your engine and also used to assess your current tune or make adjustments accordingly based on them. Now, be careful since these logs can lie sometimes! That can be rough to distinguish between a bad sensor, intake manifold leak, poorly timed cam or some hardware issue vs a tuning. And sometimes we will even make revisions while remotely tuning to help diagnose hardware issues.. But either way, the data really helps dial your tune in and make sure everything is running perfectly!
Be sure to check out the youtube videos. So far Part 1 and Part 2 are posted.
Part 1 is here: 
https://www.youtube.com/watch?v=5yMerAv4JTI
Part 2 is here: 
https://www.youtube.com/watch?v=ZwNytcitOh4
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