Man! Your knowledge on this subject is incredible! Subscribed!

This fella is super/freaky smart in thermoneodynamics/physics and the Laws off..... Any, selectively, who really wants to go the rabbit hole, to learn when, where, why and what should watch/study this video at minimum: 100 times. I'm on my 99th and still learning. Do not be afraid or embarrassed to rewind/repeat every second of this magnificent explanation and application of theory in computing VE. If one understands and capable to apply such computations, his time and investment is paid for. Many Y-tubers seek entertainment, some quest for knowledge, you know which you are when you click to watch. It is also a reflection of society: entertainment is less moles of intellect; high level intellect= more moles of brain activity. I wish Y-tube would allow repeat viewers to "thumbs up" every time this is viewed, not just then first time. the guy deserves at minimum a masters degree in this study and application. Dr. Victor Zane /Cardiac Physiologist

@ChopperDoc181

3 жыл бұрын

Best comment ever. As they say, knowledge is power, and in this case literally since we’re talking horsepower. I appreciate the feedback and I’m glad other folks can learn something here from my research on this subject. I’m very happy to be able to help others understand what they are actually playing with. It’s really quite interesting if you ask me.

Great video! Very helpful in understanding what's going on behind the scenes.

Thanks for this explanation. I've often wondered why GM uses g/cyl airmass rather than manifold pressure. But its clearly much more precise measurement of intake air volume.

@ChopperDoc181

5 жыл бұрын

Yes it seems to work pretty well because it accounts for heat, which as we know has the biggest effect on airmass. I'm glad you liked this. The bias I have discovered has a factor of 1/2 I learned while experimenting with this in excel and trying to work out a bias formula for use in the scanner. So the half value of the bias multiplied in instead of the actual number actually yielded far more accurate results, almost always matching what the PCM was actually reading in the scanner. Naturally there is some delay in the software, sensors, and PCM itself, so the numbers don't always match perfectly. But pretty damn close if you plug the formula in and play around. In many places, it was to the second decimal for a number of frames in the scan. I will work on this soon, provided I can find some time and see if this idea still has some merit. It seems to work in excel, just have to get some new scans to play with, which I should have opportunity to do so soon.

I just ordered HP tuners and I've been tuning megasquirt for a long time in VE and I was looking at this grams... like what is this? Anyway great explanation I totally get it. I kind of skipped around to the math in the middle of the video anyway thank you so much for making the video

enjoyed the approach of the video. thanks for the info!

@ChopperDoc181

4 жыл бұрын

I'm glad you liked it. It's not enough for some of us I guess just to be told to do one thing or another, I have a problem with needing to know everything on how it reaches it's numbers and what I'm playing with when tuning. I worked on many different aspects of these PCM's trying to decode a lot of the calculations, like idle, transients, and even the bias. I actually found the limits of the scanner in this case, because the math just got too complicated in one formula and started having to reference another. Unfortunately, you can't reference a user math with a user math... lol. But I spent weeks trying anyway.. lol. Maybe I'll get back to that at some point haha.

@cryanconnor

4 жыл бұрын

Very cool. I'm new to tuning, but I'm an engineer, so really enjoyed getting into understanding more of the math. Turns out as I watched this video and some of your others and I realized the tune I paid for 3 years ago was a MAF only in my off road buggy. I'm now trying to understand the implications of that and I'm wanting to go back to tuning my VE table then MAF then timing to effectively get away from MAF only. I'm having lower RPM running and idle hanging issues as well as some other not great behavior. Anyways, I'm spending a huge amount of time on youtube and forums before I touch a thing. Watched most of your videos as well as many others.

@ChopperDoc181

4 жыл бұрын

@@cryanconnor Sorry for the late reply, but it’s very cool to have someone with engineering experience on the thread here. The math is complicated, for sure, as it starts getting into thermodynamics and so forth because of evap rates of the fuel, and of course this behavior changes with vacuum and heat. The tuning methods themselves aren’t difficult, but the understanding, is. Idle uses it’s own calculation and as of yet, I haven’t figured that out. It goes off of “area” in square millimeters, so this throws another dynamic in and I haven’t been able to crack it as of yet, but this is the reason the PID “Idle Desired Airflow” is different than “Dynamic Airflow” in the scanner. The Idle Desired is the result of the IAC Effective Area table in the tune, and this starting point or reference is the Base Running Airflow table. So basically, the BRAF table determines what value “x” is at step “x” in the IAC table. I have a video on how to map the curve using dynamic airflow, which is also why using dynamic airflow for the BRAF is seemingly more accurate. The actual value of the step “x” in g/s is what is difficult to ascertain, as again, it’s in “area” whatever that means when it comes to a specific value. Obviously this will change a lot when you have a different sized throttle body, and going from say a 90mm to a 102mm changes the “effective area” of the air getting past the blade, in addition to the air being allowed past by the IAC itself. So what this all means, is that the fueling calculations are either biased, or completely different when the car is in what we call the “idle routine” which is easily noted by the spark behavior after the delays are applied from the tab “Idle > RPM” under proportional, integral, and derivative (aka PID... boom, epiphany right?) as the spark will begin its “sawtooth” pattern under idle conditions. So that’s the big question. Is it using a different fueling calculation for idle? Or is it using dynamic? Or is it using both? Hard to say. Without knowing the delta airmass of the “area”, it gets rather beyond simple math and should be on a bell curve and not a linear axis, mixed in obviously with heat, and all the other variables discussed in the video here. Without seeing the actual coding, it’s pretty tough to know which is true from the questions. As once the curve is set using dynamic, you will be able to note that the PID idle desired changes thereafter. It doesn’t really matter that the number is different so long as the numbers actually work. Call me crazy, but not knowing why it changes after matching them up to set the IAC curve still bothers me lol. One of these days I’ll get back in excel and the scanner and experiment some more. As for your tune being off, what I’ve learned over the years is just go with what works. If the AFR is right, no sweat. If not, then it will require some tweaking. As for hanging, 99% of the time it’s caused by spark, not air or fuel. Spark increases or decreases actual torque being produced. So less spark is less torque. Over fueling can contribute to it, but anything richer than stoich cannot burn anyway, so what this tends to do is simply foul plugs and hurt horsepower. I know that’s backwards from conventional thinking, as many seem to think more fuel = more power. That’s incorrect. Leaner mixes will net more power because essentially engines convert chemical energy to thermal energy, aka, expansion of hot gasses are what make power in the first place. That means the closer you ride the line of max cylinder temps, the more power is produced. The term “lean is mean” is the best way to remember that. The reason we run them richer under stress, aka, Power Enrichment is simply to cool off the cylinder surfaces to prevent them from getting TOO hot. Too hot leads to detonation and possibly preignitions. Fuel is literally the best way to cool off the cylinder between strokes. Any ratio beyond the stoich of the fuel type is literally “wasted” because it simply cannot completely burn off at that ratio. So there’s your reason for it being richer. Fuel is used as coolant. I have an idle tuning guide as well, and essentially what works best is adjusting the blade to get the IAC counts in a 40-60 hot range, and plugging in the numbers for dynamic on the BRAF table, then matching the curve to the IAC using my video explaining that. Idle air doesn’t have as much of an effect as spark does for return to idle behavior as it gets kicked out of the idle routine as soon as it hits the TPS threshold for that as determined by the spark table select %, which is only like 3 or 4% or so. So this puts you on your main and idle spark tables to correct hanging. Getting the fuel right also helps, but not as much as spark will. You can also play with spark in the scanner to see what correction will work best.

You are the man!! Very helpful! just gotta say you sound just like big chief!! Haha

Doc, I'm not following how your getting a temp bias factor of 0.2197. I'm running the factory 98 LS1 pcm. Under the air flow tab, I have a table cylinder charge temperature bias vs airflow. 0 to 150 g/sec. The bias factor numbers are 0.1714 at 10 g/sec to 0.0430 at 150 g/sec. What am I missing?

@ChopperDoc181

3 жыл бұрын

I'm using a stock tune file for a 2002 PCM (0411). The LS1 is indeed different. Don't sweat it if you are seeing different numbers. It's just an example of how it works. Funny thing is, after more tinkering I actually found the bias is double, so there is a slight error with the formula in the video. When calculating, it ends up being half of the table bias in the actual calc. That's probably why the bias goes up to 2.0, and if set at 2.0 the total value would end up being 1. So in reality there's a 1/2 before the bias math. Hopefully that makes sense.

Thanks for the explanation. Do you know how base fuel is calculated from dynamic air mass?

@ChopperDoc181

4 жыл бұрын

I've been working on that off and on. I tried to work out some formulas to determine actual commanded spray using injector data, pulse width, and flow rate (pressure). Limited success so far, and it's been a while since I've looked at it. All the numbers needed are there, it's just a matter of putting the right numbers in the right places to figure out how the fueling is done. I do know that there is a cylinder aimass model that uses injector information to determine the airmass. It's actually built into the scanner under the predefined math parameters if you are curious about it. The formula is: (IAT(K) * IFR (g/s) / 1000) * IPW(ms) * AFR Commanded / MAP (kPa)

THANK YOU😅

Change cylinder volume in the PCM, by a lot, then look at the VE again. If it looks the same while displaying in percentage, your tuning software is accounting for that, not the ECU.

@ChopperDoc181

3 ай бұрын

There are many formulas and tables in the PCM we don’t see at all. This is just showing the simplified version of what the PCM is accounting for, what I would call “theory” because there are a lot of things that do not translate directly from the mathematical theory. The ideal gas law is the law it is referencing. Whether or not this is actually what the PCM is using is another story. Also, when you adjust the volume, HPT automatically changes the VE iirc. So yes, it does compensate for this.

@Marc_Wolfe

3 ай бұрын

@@ChopperDoc181 It being HPTuners, compensates, not the ECU. I'm over hear not paying that extorsion price, trying to use a P59 with Universal Patcher as a super cheap Microsquirt alternative. Already got it running a CB450, with a very hamfisted approach. I thought "oh boy, it says GM Gen III, I'll get specific info instead of theory" then I realized I thought wrong...

@Marc_Wolfe

3 ай бұрын

I said the hell with it and backwards mathed the percentage close to stock 222 is 37 of 600. Multiplied entire table by .37. Which changed hardcoded numbers by the same. That's probably fine, but I was hoping to validate that. Oh well. Now I'll see if my IAT reading is close to accurate while it runs happily. I have a potentiometer in place of IAT to make it easy to see what direction I need to go with tune, since i don't own a wideband.

@ChopperDoc181

3 ай бұрын

The Gen III’s supposedly do in fact use PV=nRT, but, there are adders, and other factors like you said the software makes up for. It would be a wise assumption that changing the VE in HPT is probably changing more than that in the PCM. I don’t know that for certain, but I do know we don’t see all the tables the PCM uses. This is especially true on Gen IV’s. The editor definitely changes many, many tables with a keystroke. So you’re right, this is not that in depth down to the code used for each input and calculation. My apologies for that. Sorry it’s not helpful to your project.

@Marc_Wolfe

3 ай бұрын

@@ChopperDoc181 Looks like some of your others are, at least as a sanity check.