HPTuners Tuning Basics

[bluegoat06]

I wish i had something like it when i started tuning 4 years ago, this thread is not about "let me copy your tune" or "do you have a MAF transfer table for xxx CAI ?", you have the tool to modify what the car needs. If you're interested in answering yes/no type of questions in front of a little screen, then this thread is not for you.

Like i always said in the other forum, Buy the Pro version or you're going to regret it when you've realized adjusting fueling for example wasn't as tough as some people want you to believe. the STD version would allow you to feed in an input to the HPT device so you could technically have fuel readings throgh the AC line 5.0v input for instance, but you'll have to dig in other forums how to do that, little bit of welding required, i'm lazy and like to go straight to the point. i don't care how is done with the STD version. Price wise goes like this
Std Version Price: $499
Pro Version Price: $649

For $150 more, the main differences between versions are: The Pro gives you the ability to log output signals from a WB, Fuel pressure, Trans pressure or any other 0-5Volts output sensor, right out of the box, just plug the output from the sensor, directly to your VCM, configure the input using VCM scanner, and forget about it forever.

Plus, you can data log using the VCM box itself without a laptop.
If you have STD already, and want to upgrade to Pro, it would cost you $289 extra plus shipping.

Before getting into the main points
Once you get the WB of your choice, dig in HPT forums how to adjust the WB offset in the HPT scanner so what the WB is displaying is also matching what you see in the HPT Scanner. There are plenty of threads that'll show you how to do it. it's not difficult.

Get familiar with the VCM Scanner and VCM Editor first, learn how their menus operate. read the file from your car, save it with a name, and make another copy of it (just do a save as from the editor and give it a different name) so you can play around with it. later on, it would be easier to browse around the menus, use compare function, copy functions, copy differences, etc, etc.

Disclaimer: I will NOT be held responsible for, nor claim responsibility for damage to a vehicle or loss of any warranty coverage from members or guests that use this GUIDE. Use this How To as a guide and reference ONLY. Do not directly copy numbers or values into your tune from this write up without knowing what you are changing first! That being said, every vehicle is different. As such, every driver is also different. Expectations of driveability or performance will VARY so once again, use this write up as a GUIDE and adjust your tables and tune to suit YOU and your goals/expectations.

E38 PCM, G8GT/GXP Basic MAF tuning Guide

Note: as always, make sure you are familiar with how the VCM Scanner/Editor works. You’re responsible with what you do with the PCM/ECM. Research what you don’t understand, read, read and keep reading. There is a ton of things that can be changed to improve performance, this guide is only a very basic extract of the things we can do with HPT to change fueling using the MAF when a CAI, or exhaust, or headers, or everything combined etc,etc have been added to the car. Even stockish cars can benefit from the changes. As always, the operator assumes complete responsibility for the changes that she/he are about to perform.

This a very basic guide where you’ll learn how to adjust your idle/part throttle fueling using the readings you get out of your 02 sensors translated to fuel trims, and how to adjust your WOT fueling using a WB.

Fuel trims are composed by LTFT’s and STFT’s. I’m not going to go in great explain about them, but I personally don’t use LTFT’s for anything in my tunes.

LTFT’s are just an average of an already average value (STFT’s), STFT’s are instantaneous, and since we can manipulate the MAF to bring this values down and make them 0 or a slight negative value, there is no need to have their feedback. For me it’s a matter of opinion, feel free to use LTFT’s if you wish.

Something else you should know is that GM employs 2 different systems to derive fuel calculations. Speed Density (up to 4000rpm, Non WOT) and MAF. Again, you should probably research about them, but in summary, SD assumes airflow based on variables like engine RPM, MAP KPA, intake temp, engine volumetric efficiency values and what not, while the MAF use a sensor that directly measures the amount of air inducted into the engine.

They both have their benefits and cons, they both have applications when one would be better than other. They both get tuned independently from each other in the GM approach, and combined together at the end to improve part throttle driveability/mpg, etc.

Different manufacturers have their own implementations as well, Ford uses MAF only in all their cars, Chrysler uses SD only. GM had to be wiser as always and they decided to combine both models together.

For the purposes of this guide, we’ll be separating the SD portion and tuning the MAF independently from SD.

SD uses VE lookups to derive fuel calculations at part throttle conditions. Disabling VE lookups would not affect how your car runs. Fueling transitions won’t get affected like they did in the LS1’s, more likely due to their slower PCM.

Tuning the VE though can improve driveability, especially on cammed cars, improve mpg, etc, etc, and would be better suited for FI applications where the MAF limits are getting reached/exceeded either by airflow or frequency. I’ve been running my car since day 1 in MAF only.

And I ran my cammed Goat in MAF only mode for a year, SD only for about 6 months, and another 6 months using the GM SD-MAF factory approach. We don’t have a VE Table like E40 vehicles have, but there is virtual VE calculator available at HPT for you guys to use.

http://www.hptuners.com/forum/showthread.php?t=26884

In Summary, do not tune your MAF with VE lookups enabled, both systems are designed to arrive at the same airflow values. If the MAF for example is reporting 25 g/sec airflow at say 1500rpm, VE would be reporting the same or at least one of them would be within 1 g/sec from each other when the car is stock, and it's still running the factory tune.

Both models have to be corrected depending on the engine mods, this gets more accentuated in throttle response in cammed vehicles. Since we’re modifying what the MAF is actually measuring, airflow calculations would be more accurate in the MAF model, but still stock in the SD model. So unless you can tune your SD model, so SD would be reporting the same airflow as the MAF, leave it disabled. The car would run as expected, and in fact would run better at part throttle having at least the MAF model tuned out, than when the Stock SD settings are estimating airflow to be a different value than the MAF reading values are reporting, which would translate in poor throttle response.

You can tune the MAF first since it’s easier and quicker, then move on with SD tuning,or run her in MAF only for a while until you get familiar with SD tuning, or keep her running MAF only forever.

I would take a general approach here based on my own experience, and say you can run MAF only in anything from a stock G8 to a cammed one. Because of our heads, cam choices cannot be really that radical compared to what you can run in a Goat/Vette with an LS2 and massaged 243 heads, or AFR 205/225’s , TFS 225’s etc, and it turn, the MAF only approach can still be used since there isn’t a lot of exhaust reversion to deal with.

To start, make a copy of your stock/current tune, and give it another name, since you’ll be modifying this file out, You don’t want to override your stock/current tune and then don’t have that file to revert back.

How to disable VE Lookup:
Simply set dynamic airflow High RPM disable and RE-enable to 100rpm and 0rpm like this:



How to disable LTFT’s: (fuel trims would be dictated by STFT’s only)

To disable LTFT’s , set the min ECT to 493°F & the max ECT to -40°F



To Disable DFCO,CFCO (M6 Trans),DOD,COT(depends if cats are present).

Under Fuel Cutoff/DFCO set DFCO enable temp to 493°F & disable temp to 493°F. Then set the enable & disable RPM to 8192. This is so deceleration fueling wont effect the tuning process. Under normal conditions the computer leans out the a/f mixture when you let off the gas which can skew the numbers you gather for tuning your MAF table at part throttle. I don’t do this when tuning WOT fueling.
For M6 Trans, Under CFCO, set enable VSS, Enable RPM and Enable ECT to maximum values to disabled CFCO, 318mph, 8192RPM and 493F

DOD (important to disable DOD while tuning MAF or SD as DOD airflow would screw your V8 mode readings. At the end, you can put DOD back if you wish, and 02’s should cover for the difference in airflow). Simply disable the DOD master under COT/Displacement on demand general. I didn’t disable COT as I still have the stock cats, if you don’t have cats, you can disable COT, if you have cats, just change the COT multiplier to something less aggressive. I used 1.06 as the new afr modifier. (COT Max enrichment).





Flash the PCM with this settings.

[bluegoat06]

Logging MAF Data
Use the vcm scanner for this, use the space bar on your laptop to start logging once the vcm scanner is open, press the space bar again to stop the logging. there is a config file Here, Post#31, http://www.hptuners.com/forum/showth...245#post224245
, download it, and copy that .cfg file to your custom config files, so you can use it with the scanner to to log data.

Use Histogram#8 from the config file you downloaded. This histogram logs MAF frequency vs STFT’s, Histogram#9 does the same using LTFT’s (for those who like to se LTFT’s)

Start the engine and let it come up to full operating temperature. While the engine is warming up, start the HPT Scanner, connect to the vehicle and start monitoring your data (you don’t need/have to log at this time). Once the engine is warm (170-180 °F or higher),start your drive, and start data logging. Your driving style should be calm. Avoid sudden throttle changes. The engine should idle around 2700-2800hz, your part throttle go to around 7200hz.

You want to hit as many cells as you can, as many times as you can. Try to get a cell count of 20-25+ per cell. This should give a decent error% that would applied in the MAF transfer table. Avoid doing this with a heatsoaked IAT, the factory did this at 86F IAT and while the PCM have compensation to different temps, you’ll get more accurate data with IAT readings closer to what the factory used to come up with the calculations.

Once you’re finish with the logging, you’ll be ready to modify the MAF. You should get something like this:



You want the STFT’s to be less than 1%, 2% tops. The closer to 0, the best, slightly negative values are ok. (like -5%). In this example, we’ll take all the cells starting from 3900hz and above (because as you can see in the histogram, the error is 3% or more, 1% is fine, later you can modify those if you want), and either paste (half multiply) to the MAF, or you can highlight those values directly in the MAF using the editor, and remove 2% from the MAF table, for the same cells. Keep in mind the MAF is a 3rd order polynomial, and the curve is there for a reason.

So for example, to remove 2% from a cell(s), you have to multiply the cell(s) by 0.98, in contrast, when you want to add 2%, you have to multiply the cell(s) by 1.02, you want to remove 0.5% airflow, you multiply the cell by 0.995, if you want to add 0.5% you multiply by 1.005. This is done in the editor itself, highlight the cell or cells that you want to modify, type the number in the g/sec field, and then hit the multiply buttom.

Do not use the + sign in the editor to modify MAF airflow. you're adding/removing an error%, not an absolute value. you would use the + for instance when you want to add/remove timing.

You can also copy using the scanner, simply highlight the cells that contain the values you'll copy, (it has to be one block of contiguous cells), right click in the cells with the mouse and click copy, or once the cells have been highlighted press Ctrl-C, open the editor, go your MAF table, and start in the same cell where you took the values from with the scanner, right click with the mouse, and select paste special/multiply by half. the same cells you had selected in the scanner should be modified in the editor. make sure the same cells are highlighted. you don't want to change cells that doesn't have to be modified. This is why it's important to get familiar with both tools, scanner and editor. Make a copy of your tune file, and play with the copy using the editor, get familiar how the functions + and X work in the editor, how things change in color when they're modified, how to undo changes, etc,etc.





Try to keep that curve shape as much as possible. You can use the edit compare function to compare your new modified MAF transfer values against the stock one to look at the curve shape at path throttle.

You can model the shape of that curve using your mouse, position the mouse over any portion of the curve, press the left click button, then move the mouse to make the shape.

This how my MAF looks like compared to stock, avoid peaky valleys, remember the MAF is measuring airflow, so airflow won’t look < or > on the graph. it should follow the curve, plus the curve should be rounded where it needs to. This would make fuel delivery more accurate.



Once you’ve applied the error% to your MAF cells, and smoothed out the MAF curve, flash the file. And repeat the driving/logging process.

The idea is to get as close to 0 as possible. Again, watch those IAT’s, if the car is already heatsoaked, stop logging cause youre readings would change when the IAT is cold again. Heatsoak=lean, meaning the 02’s would indicate you need to add more fuel, meaning when the engine is cold, the trims might indicate pig rich readings. Negative values are ok, but you don’t want to have big negative values either. 1% to -2% is great.

At the end, you stft’s should look like this:



Now you’re done with you idle and part throttle fuel, if you had a CAI, headers, etc, etc. just repeat the process and bring those trims where they should be.

Once you’re done, put the DFCO/CFCO, and DOD(if you want DOD) values back to stock.

VE lookups should be disabled until you learn how to tune VE. Again, the car would run fine without it, but could run even better with it. Personally, i run mine without it based on the experience I have with LS2 and now L76/LS3 engines. Mpg difference was pretty much nothing, and I haven’t notice any major problems with fueling transitions to warrant running the VE calculator to tune the VE. If I had FI with big horsepower, I’ll be tunning SD though.


Tuning WOT with a WB: remember to configure the right offset for the WB you’re using. The config file I posted is assuming an AEM WB, and even still, the offset could be different depending how the WB gets wired.

This post should have more info, http://www.hptuners.com/forum/showthread.php?t=17525

Open you VCM editor, Under Power Enrichment set the EQ ratio vs. RPM to your desired a/f across the board.

This will keep your engine safe, the numbers shown will aim for a 12.5 afr in PE mode, basically 14.7afr/12.5afr=1.176



Flash your new tune file.

To tune the WOT areas of the MAF, simply follow the same procedure you did to log trims error%, except that you’ll be using histogram#11, which would show WB error%, (difference between actual fuel as measured by WB against commanded fuel, better known as PE).

The range of cells in the MAF that you should concentrate would be from around 7350hz and up while at WOT. One run is enough, normally I’ll do this in 3rd gear, from 1500rpm all the way to redline.

Apply the wb error% in the same way to your MAF, flash and repeat. Again, try to keep a nice MAF curve, avoid peaky valleys.

There is no need to disable DFCO,CFCO or DOD for WOT tuning. Half multiply when pasting the values from the scanner works good, but using the chart view, with the histogram combined can give you a better understanding on how much of that error% to apply, and where at the MAF frequency to make the fuel more stable. you'll see when you get to that point


Enjoy.

[bluegoat06]

Making your G8GT/GXP more fun to drive
Some people think the car feels heavier when driving around town, well, our cars are actually on the heavy side of the scales, but besides our sloppy stock trans tune, there are things in the engine side that should be changed to actually make the car feels like a true V8 Sport sedan.

I'll start with a change that has to be done in the GXP's and 2009.5 G8GT's since the stock calibration doesn't allow the throttle to be opened as it should before 5000rpm, 08 and 09 G8GT's doesn't have this issue.

This is how your stock throttle opening rate table looks like for the GXP/2009.5 G8GT, just change everything in there to 100 and enjoy.



Power Enrichment, when does it actually kick in?
The beauty of driving at stoich, in close loop operation, protected by those fuel trims that are now super close to zero (if they're not, time to be less scared, and start doing what you should, since you have the tool in your hands ) then all sudden, the rush to put the pedal to the metal, engine operating mode change to Open loop, MAF gets referenced, fuel calculations are done, and fuel is rushing in to meet what you have established in your PE table. WB readings change from stoich to 12.5, assuming you have done the homework already, with a little bit of delay on that inital punch... couple of things you should do to lower that time.

There are 3 conditions that have to be met so PE can be enabled.
MAP Kpa, TPS% and Delay RPM, order doesn't matter as long as all 3 are met. in stock trim, you have to exceed 15 kpa, 48kpa up to 3000rpm, and delay rpm=5000. This last settings doesn't do anything in our cars, some trucks though would actually have and use the delay. that leave us with MAP and TPS conditions that have to met to enter PE.
still, you can change the delay rpm/enable rpm to zero, doesn't hurt anything, and massage the PE Enable TPS Hot table to enter PE just a tad sooner. I'm using the LS2 GTO approach which is almost the same as what we have except that at 3500rpm, the TPS% required to enter PE is a little bit lower. with my trans settings, i have no problem with this approach since i've modified the shift points for the gears 1 through 4, so i don't have to punch the throttle a lot to make her go in the right gear at the right time. you can still leave the HOT TPS table alone if your trans shift points are still stock.

couple of changes here:
Delay RPM/Enable RPM both to 0
and enrichment rate from 0.001 to 1, this one is the one that'll speed up the enrichment rate process, so going from stoich to PE would be quicker.



There is more to add Here

[bluegoat06]

AFM Tuning
Aight, keep in mind i'm tuning my car to my likes, and i've found this way to keep DOD engaged to my likes, i could go more aggresive lowering the enable vacuum by about -5kpa more, and -2kpa lower in the disable vacuum for every forward gear, but i like the factory settings except for 6th, and this way, i'm forcing myself to be gently with the gas, pretty easy to engage DOD now, i go and put her at around 70mph, lift off the gas, then go back at it, gently, and DOD would engage almost right away. i keep my TPS% around 29-30%,(TPS% is not the same throttle percent you see in the engineering mode, in engineering mode throttle percent is the same as ETC% in HPT), and that's enough to keep the car around 68-70mph in 6th, you can gently press the throttle and go up to 33% TPS, and that should take you to about 73-74mph in 6th which is still under the speed limit for most freeways unless otherwise stated, and still be in DOD, and if the conditions are met, you could do close to 80mph, and still be in DOD


This are the TPS limits (in Green)


enable vacuum (just remove 5kpa from the 1400-2000rpm cells in 6th, you can go more aggresive if you want removing 5kpa more) Note: the highlighted values you see in the graph already have -5kpa from stock settings on those cells



disable vacuum (just remove 4kpa from the 1400-2000rpm cells in 6th, you can go more aggresive removing 1-2kpa more), Note: the highlighted values you see in the graph already have -4kpa from stock settings on those cells



You can also step it up even more removing around 4 from the entire table in enable vacuum, then about 2 from the disable vaccum, but like i said i don't want to lug the engine around in V4 around the city, and i'm mostly interested in freeway miles since i spend a lot of time in there, but it's just about experimentation from here if you want to try a little bit more aggresive settings.
You can also disable DOD for any particular Gear, for instance, it's disabled for 1 and 2 gear, you could disable it for 3-4 and leave 5 and 6th as the only gears where DOD would engaged.

Just keep in mind, The idea of DOD is to raise engine efficiency at low TPS%, notice when DOD enables you'll go from say 45 kpa to 60-70kpa at the same or less TPS%, and the engine would stay at such load for as long as DOD is enabled. there is a point where keeping DOD active won't give you better mpg, in fact it can be detrimental when you have to lug the engine in 4 cyl to move 4000lbs.

DOD timing has to be modified on 91 Octane, watch your scanner while in DOD, and you'll observe 4-6* KR when DOD is engaged. to tune DOD timing, i just followed the same approach i'll follow to tune V8 timing.

Copy your DOD Hi timing table into the DOD Lo timing table, and flash the fiile. this way, you'll be able to see what cells would exhibit the most timing, and how much KR are you getting. you can use Histogram#3, but this is when it gets tricky, as we can't filter DOD timing using a PID.
So i just used the status bit: DOD-Requested, and whenever i'm tuning DOD, i just need to pull Hist#3, chart view, and status bit view. all 3 windows open, and you'll see how you can spot DOD timing this way. just hover the mouse over the graph view, and whenever DOD is active, the status bit would display yes, then you can use the Hist# 3 to see how much KR was present. move the graph view, and observe your data changes.

Pull timing from the rpm - g/cyl cells where it needs to, so KR is no longer present. you can do this in half of the KR increments, to see if the KR can be killed before it starts. example, if you get 2* KR, pull 1* from that area to see if KR goes away.

Again, if you haven't altered your fuel trims to be 0 or at least super close to it, then it's time to do homework before messing with timing. get your fueling done first, then modify timing.

Enjoy.

[bluegoat06]

More HPT stuff...

[bluegoat06]

and in case is needed, another page...

[Slizzo]

Oh man, thanks for this goat! I'm going to recommend this for a sticky!


Makes me want to buy an HP Tuners suite.

[travis gore]

very nice

[GeoffA]

I really need the tuningschool books to study...

Looking at your HPT screens and mine, they are different are you running beta? I have version 2.23.3931.25301 beta.

And keep up the grrrr8 work! I've looked at a lot of your posts on hpt.

[bluegoat06]

Yeah, the screenshots were taking with an old Beta, i'm running the same version as yours. we don't have the the throttle area increase rate anymore for example, but GXP's and 2009.5 models would see it.