Gen 4 (2008-2010) Viper Issues/Requests

[MeentSS02]

This thread is intended to document issues I've come across while tuning my 2008 Viper with HPTuners. I'll keep the first post in this thread updated as I work through things - the subsequent posts will document each issue with logs/configs/files as necessary.

Below is a running list of issues and/or requests, split by the VCM Editor and Scanner:

VCM Editor Issues/Requests

1. Need work around for driver demand torque and calculated actual torque 120 N-m limitation (causes limp mode if you try modifying Pedal Percent Torque Request table for better throttle response)
2. Need way to disable torque spark calculations when main spark table is referenced, but leave the calculations in place when idle spark table is referenced (torque management related issue)
3. Request additional knock retard parameters to adjust KR aggressiveness and decay rate (can currently only dictate how much timing is pulled, not when or for how long)
4. Request access to idle spark table
5. Request ability to be able to modify exhaust cam angle at idle and under deceleration (current table supported does not respond to changes made during either condition)
6. Request ability to alter tachometer update rate (Mopar PCM does this)
7. Request ability to alter shift light set point

VCM Scanner Issues/Requests

1. Request throttle relearn through VCM controls (would eliminate the need to go to a dealer on the first flash of HPTuners) - ***Available in 3.1 beta***
2. Ignition Timing Advance (non-SAE) PID logs incorrect values (need to add 128 degrees to what is reported)
3. Exhaust Cam Angle PID logs negative values (should only be positive)
4. Exhaust Cam Desired Angle PID logs negative values (should only be positive)

[MeentSS02]

Throttle Response Tuning

I made a separate thread about this issue quite a while back, located here:

http://www.hptuners.com/forum/showth...ottle+response

In summary, I'm trying to adjust how fast the throttle bodies open when providing a pedal input. If you try to adjust the Pedal Percent Torque Request table seen here:



...it is almost certain that you'll trigger limp mode, which in this case causes the car to spit, sputter, and stumble, so much so that the car is undriveable until you shut the car off and do a reflash. Disabling the DTCs does not prevent the car from going into limp mode.

Chris@HPTuners is aware of the issue, and posted this in another thread:

yes we are working on this one, unfortunately its in a protected section that we are trying to find a workaround for. The issue is the driver demand torque and the calculated actual torque must be within about 120Nm of each other or this code will occur and REP mode. If you can tweak the tables so the torques stay close to each other that would work. We know exactly what the issue is (we support these tables for NGC and GPEC controllers) so hopefully the answer will come soon.

Finding a work-around for this 120 N-m set value would be the ideal solution, but any insight into the values that are associated with the driver demand torque would also help. I can log the calculated actual torque...if I know what the driver demand torque is (or at least is based on), I can try to work within the 120 N-m confines.

This issue is the #1 reason people left HPTuners when the Arrow PCM was offered for the Gen 5 (and eventually 4) Vipers - they have the source code, so they can get around this pretty easily, and they did with the Gen 4 offering.

Edit - here's a good video of what kinda throttle lag I'm talking about. The car below is a 2014, which supposedly addressed the issue...watch the gentleman's foot as he presses on the gas pedal, and note how long it takes for the engine to respond:

[MeentSS02]

Torque Management

The Viper PCM's torque management algorithm probably has the biggest impact on WOT performance of any setting that we can currently adjust. It is currently set up to be enabled/disabled, seen here:



Note the description: "[ECM] 51221 - Torque Spark: Enables or disables torque spark in the main spark calculation."

This statement is accurate, but not entirely true...disabling the torque spark calculation also disables torque spark in the idle spark calculations. Unfortunately, this has an undesirable effect on idle...since this is a torque-based PCM (read more about those here: https://www.hptuners.com/help/vcm_ed...vanced_e78.htm), you essentially end up taking away the main tool the PCM uses to control idle over/underspeed: spark advance. This is actually pretty easy to see if you log timing advance, and watch it at idle:

Torque Spark Disabled - commands flat 12 degrees of timing advance at idle (middle of chart display):


Torque Spark Enabled - idle timing advance bounces around from about 5-20 degrees to keep over/underspeed in check:


If you log the spark state, you can easily see that it bounces back and forth between idle:



...and main:



...hence my request: It would be ideal to leave the torque spark calculations enabled when the idle spark advance table is being referenced, but disable the calculations when the main spark advance table is being referenced. If you disable the torque spark calculations as it is currently set up, idle quality suffers greatly...it surges and has a hard time finding and maintaining the set idle speed. Basically, the throttle bodies can't adjust the airflow fast enough for it to be a viable idle control tool. Here's a video I found that shows the idle surge pretty well, granted this is a turbo build:



Now, here's why this is important...the graph below is set of logged timing advance for two WOT runs, one with the torque spark calculations enabled (blue line), and one with them disabled (red line):



The red line follows exactly what I'm commanding in my main spark table - the blue line is what you actually get when you leave the torque spark calculations (torque management) enabled. At lower RPMs, it pulls about 10 degrees of timing, and that makes a huge difference in WOT performance. This has nothing to do with KR at all - it is repeatable, and by that I mean it pulls the same amount of timing every single time. Actually, for the graph above, I disabled KR entirely to make sure I was getting what I was commanding without the overly sensitive knock sensors stepping in (that's a topic for another post in this thread that I'll cover later).

I've attached the log files and scanning config that were used to generate some of the pictures above for your viewing pleasure.

[MeentSS02]

KR - Sensitivity and Decay Rate Request

For the Gen 4 (2008-2010) and Gen 5 (2013-2015) Vipers, we have the following table to deal with knock retard:



While you can effectively limit the amount of knock that can be pulled by cylinder airmass vs. RPMs, you have no ability to adjust the sensitivity of the sensors or how long KR continues to pull timing after the sensors no longer detect pinging. Based on the logging I've done, there's always some random amount of KR present, but there's evidence that this is false knock rather than something real. Here's a good example of a car where this appears to be the case:



And then there's the Arrow press release when they released their Gen 4 calibration upgrade program for the Mopar PCM:

NEW Arrow Viper Gen IV Race Engine Controller Flash available
April 28, 2015 - Arrow Racing Engines announce a new Engine Control Unit flash now available for the 2008-2010 Gen IV Viper - PN ARR-031215AA. The new flash will be available for customers who currently have a Gen IV Mopar Viper race control module (PN P5155255AA and P5155255AB) and will be more robust to allow owners to run most typical racing modifications without limp-outs or MIL?s. This flash is intended for off-road use only and will have the following changes/improvements compared to the previous Mopar off-road controller:
- Improved throttle response and feel and a more aggressive pedal map
- Misfire monitor disabled which will allow use of other engine and driveline changes without false misfire detection
- Airflow rationality monitor disabled which will allow changes to air cleaners, ducts and filters, hood scoop and other inlet side modifications without limp-out
- Knock detection disabled to prevent false retard and enrichment due to solid engine mounts and/or other driveline changes
- Temperature rationality disabled to prevent MIL?s due to changes to the cooling system, oil cooler or oiling system
- Leak detection system disabled to allow use of fuel cells without LDP MIL?s
- Rev limit increased to 6600 rpm for track use
- More aggressive exhaust note on deceleration (i.e. popping)
The re-flash of the existing controller means no further action by the owner would be required such as VIN programming, mileage or re-learns. Several fault codes will be set due to the re-flash and will require the owner to clear the faults (although the faults will clear after a number of trips on their own) at an authorized dealer or service center. Cost of the re-flash is $295 which includes shipping and handling.
Owners who wish to purchase the new flash can contact their performance dealer or Arrow Racing Engines. More information is available at www.arrowracingengines.com

Mark Jorgensen later shared some additional information that he either got from Dick Winkles or someone else that was involved in the Arrow calibration:

...I have been on the phone with "the man" and he assured me that there is a small level of knock retard left in both the G5 and the G4 PCM's. Arrow will revise the release although they say the knock will have to be significant before retard happens because there is so much false knock they needed to dial it back to get any power.

So they apparently put some amount of sensitivity back into the sensors, but how much is unknown. I can provide data logs and tune files if anyone wants to check out the kind of KR I'm seeing.

A little birdie told me that this is something that is already in the works, so if that's the case, carry on

[MeentSS02]

Right now, the Gen 4 and 5 Vipers have full access to the main spark table:



...as well as a whole bunch of tables that are used to pull/add timing as required for different conditions (IAT/MAT/ECT/etc.). This main spark table, however, does not control how much timing is requested at idle.

This is actually pretty easy to see by just logging the spark state:

Idle Spark Table being referenced:


Main Spark Table being referenced (throttle blip):


Whether or not the idle table is referenced appears to be related to pedal position...if your foot is off the gas (e.g. sitting still or under decel), it uses this table to command the amount of timing I end up seeing. With torque spark calculations disabled, it commands a flat 12 degrees of timing:



...and with torque spark calculations enabled, it appears to hover around 12 degrees of timing, but goes from about 5 degrees all the way up to about 20 degrees of timing depending on how high/low the over/underspeed condition is.

If I had to guess, I'd bet this table looks a whole lot like the cranking spark advance table, shown here:



Access to this table would be a "nice to have" kinda thing, but probably not a necessity for us guys running the stock VVT cam. Still, it'd be nice to have

[MeentSS02]

Currently, we can enable/disable the A/C compressor by pedal position only:



While it is certainly effective, I'm sure there's also an enable/disable by RPM somewhere in the code...it wouldn't make sense to have the compressor engaged at high RPM under decel (where you'd be under the 100% pedal condition from the stock calibration).

If I get a chance, I'll see if I can figure out what this RPM is by just driving around with the A/C on, and see if I can note where it shuts off as the RPMs climb. I'll update this post if I get more info.

Edit - just got done going on a drive, and tried to see if there was indeed an RPM enable/disable point for the A/C compressor. I got it up to about 5,000 RPMs in second gear, and the A/C was still blowing ice cold, so there may not be an RPM disable. I was pretty surprised by this since I'd think spinning the compressor that fast may not be the best for longevity, but I've not looked at the pulley size to see how fast it spins in relation to the motor. Unless I find evidence to the contrary at some point in the future, disabling the A/C may only be by pedal position.

[MeentSS02]

For those that don't know, the Gen 4 (2008-2010) and Gen 5 (2013-2015) Vipers use a Mechadyne cam-in-cam variable valve timing system that allows the exhaust cam lobes to be moved in relation to the intake centerline, effectively changing the lobe separation angle. This may not seem like a big deal, but the Gen 4/5 Vipers are cam-in-block, pushrod motors...VVT is certainly nothing new for this engine layout, but most others (like GM) advance and retard the entire camshaft, not just the intake or exhaust lobes. More info here:

http://www.mechadyne-int.com/vva-pro...tric-camshafts

It's a pretty nifty system, and works well on the street. It really comes alive over 4,000 RPMs, and was one of the first things I noticed about the car when I put the hammer down. In this application, only the exhaust lobes can be moved, not the intake. From what I've read, the exhaust cam lobes can be physically moved between 0-45 degrees.

As of a beta release earlier this year, we were given access to the table that controls the cam. Here it is:



You can log both the desired and actual exhaust cam angles using PIDs in the VCM Scanner. Here's a screen cap of logged Desired Exhaust Cam Angle:



You'll see there's a pretty big mismatch between what's commanded in the table vs. what's desired by the PCM. It seems like the cam references another table (or perhaps a single value) for both deceleration and idle (I tried adjusting it to increase the overlap at idle to no avail).

At the end of the day, it isn't important as my motivation is purely to increase the overlap at both idle (for a little lope) and under deceleration (to pull more unburned fuel into the exhaust for more popping)...just curious to see what else is going on behind the scenes. I wouldn't expect to get much out of idle since oil pressure is pretty low compared to cruising, but under decel there should be enough pressure to command whatever you like. The cam does as commanded everywhere else, including WOT.

Anecdotal evidence from people that have used the Arrow PCM indicates that idle sounds meaner and there is also a lot more exhaust popping under decel, suggesting that Arrow likely changed the exhaust cam angle at both idle and under decel. While neither of these things would enhance the performance of the vehicle, it certainly does add to the "cool factor" that a lot of people really seem to like. Personally, I'd like to see what I can do at both idle and under decel to try to mimic the behavior of the Arrow PCM, if only to say that I can. I'm wondering if the commanded values are somehow affected by whether or not the idle or main spark advance tables are being referenced (see one of my other posts above)...it could also be a function of pedal position.

[MeentSS02]

The Viper's drive-by-wire throttle body system is very finicky...if it is even the slightest bit out of line, the car will go into limp mode and be a general PITA.

For the Gen 4/5 Vipers, HPTuners had to work some serious magic to make things work correctly. The Venom PCM is a one-off system that is used only on Vipers. For some reason, Dodge disabled the ability for you to read out the PCM using HPT or any other third party tool (likely to protect their proprietary source code). In order for the software to work, HPT had to develop a custom operating system...this enables a few things, including:

1. The ability to read out the PCM
2. The ability to log enhanced PIDs with the scanner. Without it, you wouldn't be able to monitor KR, or a whole bunch of other things.

Unfortunately, it also means that you have to do the throttle relearn procedure the first time you write your car. At this point, this can only be done with the factory WiTech scan tool...here's the procedure for the first write to a Viper from another thread I started on the Viper forum:

1. Open HPTuners VCM Editor (Beta)
2. Open your stock calibration file (generated by HPT, not actually read out from the car)
3. Make sure your interface is plugged into the car and the computer
4. Put your key in the ignition and turn it to the Run position (but do NOT start your car) - wait a minute for everything to go through its initial checks (if you try to write before this, you'll get a "write failed" message)
5. Click on the computer chip with the red down arrow - this will bring up the vehicle writer window that looks something like this:



You should see your VIN (I blacked mine out), the operating system (it will end in H0, indicating that it is the HPTuners custom OS for Gen 4 Vipers), and a drop down menu that has Write Entire selected. Write Entire is the only option for our vehicles.
6. Click the Write button - the writing process will take about 60 seconds. You'll hear some chimes and see various lights on the dash light up as it writes. This is normal.
7. After the software is done writing, it will prompt you to cycle the ignition. Turn the key off and then back on (again, don't actually start the car).
8. Unplug your HPTuners interface from the vehicle's OBD2 port
9. Have your Viper tech hook up the wiTECH to your OBD2 port (your key will still be in the RUN position).
10. Have the Viper tech do the throttle relearn (at some point he will tell you to hold the gas pedal to the floor and hold it there for about 10 seconds, and then release it). If everything worked properly (your tech will tell you if it did or not), you can remove the wiTECH, cycle the ignition, and...
11. Start the car - it should start and idle just like it always does.
12. At this point, you'll want to take the car on a short test drive to make sure everything works properly.
13. If everything checks out on your test drive, you are done! You can now write to the car as many times as you want without having to worry about doing the throttle relearn procedure. HPTuners will eventually work it into the scanner, but for now, the dealership is your only option.

I've seen multiple posts on the Viper forum with people asking about the ability to do the throttle relearn procedure without needing to go to a dealership. For some, they don't have access to a dealership with a certified Viper tech, and for those that do, many don't trust them. It would be awesome if the throttle relearn functionality could be added to the VCM controls...I know some Gen 4/5 Viper owners that use HPTuners have been able to get away without doing it, but it really should be done, at least according to the engineers at Dodge. This functionality would allow anyone anywhere to do the throttle relearn procedure...I ended up having to drive two hours each way (to Indy) to find a Viper tech that could do this for me for my first write. Thankfully, he didn't charge me...others haven't been so lucky, and have been quoted upwards of $200 to do this simple, 10 minute procedure.

[MeentSS02]

Added some additional info to the A/C enable/disable by RPM request post...that functionality might not exist in the Venom PCM.

[MeentSS02]

This one is pretty straightforward - when you select the Ignition Timing Advance (non-SAE) PID to log in the VCM Scanner, the values are hugely negative. See this screen cap:



That was on a cold start, so the timing should have been 0 degrees instead of the -128 degrees I was seeing. The log I've attached is a short one...if you need it, I can get a longer log to see if this is a simple scaling error (as in, you just need to add 128 degrees to what is being reported).

Note: this was with the 2.24 scanner...I've not moved over to 2.25 yet. The SAE Timing Advance PID works just fine.

[MeentSS02]

So I got some additional information on the Ignition Timing Advance (non-SAE) PID problem I was having...it does appear to be a scaling issue. I logged both the SAE and non-SAE Ignition Timing Advance PIDs, and watched them...the non-SAE PID was indeed exactly 128 degree less than the SAE PID. I confirmed this by setting up a custom PID:



Proof that it worked:



Now, that said, this may have been a moot point - upon further inspection, I realized that both require 1 bit to log...I was hoping the non-SAE version was higher resolution. If you look at this chart display (SAE parameter in orange, non-SAE parameter in light blue):



...the non-SAE PID (light blue) actually has a fair amount of lag compared to the SAE PID (orange), and is pretty low-resolution.

Still...a bug is a bug.

[MeentSS02]

This was an issue I discovered a while back related to the following PIDs:

1. PID.2176 (Exhaust Cam Des Angle)
2. PID.2178 (Exhaust Cam Angle)

Both log fairly normal, expected values, but at seemingly random times, both show negative numbers, as seen here:



I haven't really been able to figure out what's going on with this one...the negative values do have an impact on the average if you are logging the values in a histogram, but this is something that is relatively easy to get rid of with a custom filter for each PID.

This may or may not be an easy fix, but it is at least easy to work around.

[viper004]

MeentSS02
Nice info, hope some of this get looked at.

[ringram]

Yeah thanks for all that effort. Id be keen on the changes too.

[MeentSS02]

In the process of dusting off some brain cells, I remembered reading about the tachometer update rate in reference to the Mopar PCM (the canned-tune off-road controller available from Mopar). Here's a list of what was altered for that particular controller:

* Power adders can be used without turning on dash warning lights. Catalysts and O2 sensors can be removed without tripping warning lights or causing limp mode to activate
* Chassis dyno results showed a slight HP gain (approx 10 hp) on a stock ACR but the intent of this controller is to work with power adders to maximize performance
* The revised fuel/spark tables are intended for power levels below 700 hp. This controller is not intended for use with nitrous, superchargers, or packages that go above 700 hp. It might work depending on your setup, but it wasn't designed to function in that range
* The 1-4 skip shift feature in the production calibration has been eliminated
* Requires the use of 93 octane fuel only
* The rev limit has been increased from 6400 rpm to 6500 rpm
* Tachometer settings have been adjusted for updates every 25 RPM (vs. every
100 RPM)
* Increases engine idle speed from 700 rpm to 750 rpm
* The ETC pedal / throttle MAP has been refined which improves pedal feel
* Tested using rear axle ratios between 3.07:1 to 4.10:1

The part I'm most interested in is the ability to alter the tachometer update rate for the stock PCM with HPTuners...I've noticed the tach is a little laggy during WOT runs, so I'm wondering if this is why that particular feature was implemented for the Mopar PCM.

It'd just be another nice-to-have feature.

[MeentSS02]

This one would hopefully be easy to find/implement, assuming the engine controller has authority over this particular feature...

The stock tachometer has a two-function arrow - it lights up orange/yellow to signify the activation of the skip-shift (1st to 4th) function, and it also lights up red at around 6,000-6,200 RPMs to act as a shift light.

Simple request: I'd like to be able to alter the RPM set point for the shift light. I've bumped up my rev limit 200 RPMs, so I'd like to be able to bump the shift light up the same amount if possible.

[UR50SLO]

Well... Our little RoadRunner Viper powered is up and idles... but I'm pretty sure the MAF scale needs to be learned/changed.

I don't have the stock air box... I currently have both of them placed in 3" pipe. The stock MAF scale is VERY rich... Reads big numbers quickly...

I'm not sure how to properly scale the MAF to what it needs.... The friend of mine that helped with throttle re-learn said the MAF/MAP are in relationship with each other and

if the calculation is off too much it'll go limp mode?

Is there a way to disable the MAF's all together?

Thanks for any help,
Scott
ViperRR.jpg

[MeentSS02]

Let me know if you guys have anything you need tested to verify functionality...I've got 1 month left (maybe 2) of decent driving weather before it has to go to sleep for the winter.

[MeentSS02]

So after downloading one of the more recent beta builds, I noticed a "Throttle Relearn" button under the Vehicle Controls & Special Functions pop up menu of the scanner. I will say this: it certainly does something (I was honestly expecting the "two weeks" pop up), because after doing the relearn incorrectly, my car threw a couple codes and wouldn't respond to any pedal inputs. I tried it again, and it seemed to take that time, so it appears to have been successful.

That function might need some polishing, but it appears to work. I sent Keith an email with some detailed feedback along with the procedure I used that caused it to fail. I can post it up here if you'd like as well.

[SultanHassanMasTuning]

has anyone used an aftermarket camshaft with these engines yet, since we have control over cam timing we can minimize the "lag" of a bigger camshaft. I have a full bolt on and looking to get more power out of it NA.