Tuning cammed and supercharged Gen V Viper

[Pekka_Perkeles]

So here are the mods:

- A&C Performance D3 F1X kit
- heads & nasty cam
- headers & straight pipes
- dual Walbro 485's
- stock PCM tuned with HPTuners

And attached is a log file from the first and only WOT run I made.

22 flatout run unknown tune.hpl

Obviously as I didn't do the tuning and didn't reach the original tuner, I had to start from the scratch. There were some issues new owner wanted to be fixed with the car.

01 stock read.hpt

Oh well, always nice to start something very new to be with a supercharged car... :-0

Will continue soon in this thread.

[Pekka_Perkeles]

Now, there were few hardware modifications I wanted the new owner to do.

First one was to move front O2 sensors to a better location. They were pretty close of a collector but still at one of the primary tubes on the headers. I wondered maybe that was the reason car was at open loop all the time.

Then injectors. I didn't know what they were so owner took them to a facility were there were tested. They found out that 800 cc modified EV14 injectors were used.

I made some changes to my first tune and it did start pretty nicely. However, pretty soon I noticed that the car goes to a limp mode. Did some reading and guessed I have to use stock injector size and scale the rest of the tune accordingly.

Other thing I noticed that the engine didn't like closed loop even if the O2 sensors were further back in the collector. While the engine was warming up, as soon as closed loop corrections activated, STFT/LTFT rise doubled the injector duty cycle and as I wasn't near the car, at least one plug fouled when the engine stopped because of mixture being so rich.

Ok, ordered and installed new plugs and forced the car to be open loop all the time.

Then it was time to do a first street ride. It is still winter here in Finland and there was some ice and snow here and there, so I was quite nervous, since the car had street racing tires....

Otherwise the driving was nice, but there was something going on at exactly 2000 rpm. With steady throttle, I noticed a loss of power. For some reason - possible related to ETC and torque management - ignition advance was dropping from 37 degrees or so to single digits and sometimes even -5 degrees. But with more TPS, it just went away:

120 first street drive.hpl

I did some changes to the tune file and next log seemed to be better:

200 cruising.hpl

Here's another street log, as well as the latest tune file:

201 just cruising.hpl

201 for street driving.hpt

What I didn't like with the car was the location of MAF, or one of the two. It was in the intecooler. Another MAF was in the charge pipe but was not used for MAF signal. That wiring is now reversed.

Tomorrow, hopefully, new logging with new MAF position. I also need to define a proper histogram and perhaps Excel sheet, as there's no MAF voltage logging available. But I think I will manage logging AFR error with static vs. measured MAF grams and changing those between runs.

On Friday it's dyno time for WOT runs! Wish me a good luck...

[Pekka_Perkeles]

Ok, made some progress today.

As the MAF is now in charge pipe, it was running fat again. I had to lower MAF grams/sec so that now when it is as it should be, it is just 38% of the stock settings.

Of course, this is mostly because of big injectors with stock flow values.

As I was testing normal driving, it went to a limp mode, which I was expecting to be happening sooner or later. See the end of the log here:

223 meni vikatilaan.hpl

The Driver Demand torque (250 Nm) was exceeding Actual Torque (140 Nm) about 110 Nm and that's why it went to a limp mode.

I removed a bit from the Peak Torque table so that the difference would be smaller. That did the trick, I think.

217 muokataan maksimiv??nt??? pienemm?ksi.hpt

Here is the log of successful normal driving:

240 nyt pelas.hpl

As MAF values are so low now, I'm going to have pegging MAF with current settings. With the WOT log from an unknown tune, I can see that max airflow value needs to be at least 250 grams/sec (combined 500 g/sec).

Luckily MAF voltage axis can be modified. I need to scale it tomorrow for bigger values.

I also made custom PID for following Throttle Body Torque error. Remember, it needs to be less than 120 Nm.

TBError.png

I don't know why, but I cannot get it showing right in the Histogram. Any advices?

Histo.png

[Ben Charles]

Best thing to do is scale the MAF curve (have too otherwise you run out of G/Sec limit) and have to play with Tq and DD

[Pekka_Perkeles]

Today I scaled the MAF voltage from the stock settings (0.06 ... 0.59 volts) to more suitable 0.20 ... 1.00 volts.

I do not need below 0.20 volt readings, so that gives a bit more resolution, but doesn't really matter.

The idea with the MAF is to follow the curve like stock as that's how the MAF sensor always works. This is the stock curve, that ends up to bit over 300 g/sec:

MAF-origina.png

I tried to use MS Excel to calculate "climbing" numbers but for some reason I just couldn't get it working. And my Matlab skills have long gone. So I did it with just by hand using HPTuners graphical way to edit MAF curve.

This is the one car has now.

MAF-scaled_2.png

MAf-scaled_1.png

I think it's not ideal, but good enough for the dyno.

Here's the latest tune. I'm probably too conservative with timing table scaling, but better to be safe than sorry...

222 laihennetaan.hpt

[Pekka_Perkeles]

Best thing to do is scale the MAF curve (have too otherwise you run out of G/Sec limit) and have to play with Tq and DD

Thanks Ben for your kind advice!

I guess I'll never tune this kind of Viper again as I'm from a rather small country. But it has been an interesting journey to start from the scratch and just think and think and try to understand how to tune this kind of animal.

It somehow reminds me of a "before Internet" era where Google didn't exist and you had to use libraries, magazines and your own brains. And perhaps a little help from your friends.

[Pekka_Perkeles]

Spent 4.5 hours at dyno.

What an interesting beast!

Or should I say a f----g nightmare.

Again and again it went to a limp mode. Playing with torque (driver) demand tables seemed to be hopeless. So I trashed my idea to use stock injector values. I went up to 40% bigger injector values and did the same for MAF values.

Again it went to a limp mode. But the actual and demanded torque was much closer. I removed 8% or so from the values and that did the trick!

The next and final thing for that day was two WOT runs. Didn't end well, but at least nothing broke, as both runs were stopped soon after 4000 rpm's.

Well, scaling MAF voltage from 0.59 volts to 1.00 volts doesn't work. There is some kind of hard limit, as you can see from this log...:

16 t?yskaasua meni vitun laihalle.hpl

And here is the tune I used for that run:

240 sytk?? ja seosta.hpt

For the final run I tweaked PE table to add fueling after MAF maxing, but it didn't do anything.

The good thing is that I now know that the MAF signal needs to come from the one located in the intercooler. And I won't be using MAF voltage scaling.

I think I now know how to tune this thing. Only unknown issue seems to be why ignition advance is so low at WOT. There isn't much to tune, maybe changing IAT source from MAT could do something?

[SultanHassanMasTuning]

looking at your last tune, your peak torque is factory. i would raise for sure

since map sensor is not changed, map related limits needs to be changed

exhaust cam timing table zero'd?

[Pekka_Perkeles]

looking at your last tune, your peak torque is factory. i would raise for sure

since map sensor is not changed, map related limits needs to be changed

exhaust cam timing table zero'd?

This has custom cam so not a stock cam. I think it is not adjustable.

MAP (values) is stock. Thanks for that, I will rise that.

Yes, peak torque is still stock. Probably need to raise when back at dyno.

Thank you very much for these recommendations!

[MeentSS02]

First, good on ya for trying to sort through someone else's mess.

Also, welcome to the wonderful world of tuning Vipers, or lack thereof.

You will end up having to band-aid everything together to make it work on the stock PCM. For a setup like that, I would never recommend it. Too many limitations. Motec or something equivalent would be my first choice, but I have no experience tuning anything outside of HPT/stock PCMs.

Now, on to the relevant part:

I think I now know how to tune this thing. Only unknown issue seems to be why ignition advance is so low at WOT. There isn't much to tune, maybe changing IAT source from MAT could do something?

I don't think there is an MAT sensor, unless it is somehow incorporated with the MAP sensor on the intake manifold (highly doubtful). I'm pretty sure it is calculated, but I'm not sure how it is calculated. To make things easier, I have the source on mine set to IAT, as it is something I can log, and makes intuitive sense.

For timing, you have to make sure you aren't running into some sort of torque management issue. I haven't downloaded any of your tunes, so if I get a chance, maybe I'll take a look.

Either way, you may need to look at the mean best torque tables. My light bolt on Gen 4 wouldn't give me full timing advance unless I altered the MBT 2 table. I had to add some timing to the WOT region.

When I was figuring out how it worked, I initially added timing to the MBT 1 table (MBT 2 untouched), and it pulled even more timing, so there is some sort of relationship between the two when it comes to the final amount of timing allowed.

Definitely don't be afraid to pull from the driver demand (torque % request) table, especially if it is going into limp mode under part throttle conditions. I know someone with a V-10 swap that had this issue until he reduced the numbers in that table.

[MeentSS02]

Looking at this tune: 240 sytk?? ja seosta.hpt

Set the catalyst protect 5,400F for both...I can't imagine anyone cares about emissions for this setup. I don't understand how they are calculated by the PCM, but it will pull timing and dump fuel in a hurry if you go over those thresholds.

Make sure you are logging knock...you've made them more sensitive, so you need to see how much knock is being registered. Not a bad thing, but just know what it is doing. That said, I had to desensitize mine quite a bit to keep the false knock at bay on my Gen 4.

Given how low your main spark table is, the mean best torque tables shouldn't be a player...disregard what I wrote above.

I also don't see any reason to leave any part of misfire detection enabled unless it is helping you diagnose something.

Under Engine Diag > Misfire

Set the Min IAT to 400F
Set RPM Min to 7,000
Set Disable RPM 500
Set Enable RPM to 400

With the way you have it set, it won't pull any power though, so not that important.

[Pekka_Perkeles]

since map sensor is not changed, map related limits needs to be changed

Today I noticed that the car has some kind of MAP-sensor related small controller/limiter that is definitely not stock Viper stuff.

I think it's purpose is to make PCM happy during boost, i.e. limit MAP max value so that it would be naturally aspirated and not boosted.

Step by step going forward! :-)

[Pekka_Perkeles]

I will post final report tomorrow.

While the original reason to tune this animal was not WOT - as it already made plenty of power - I was able to increase hp roughly 50 or so and torque about 200 Nm (equals about 150 ft-lbs).

[Pekka_Perkeles]

It seems that I've been too busy lately.

Here's the final update (at least for now).

I think I left knock sensors a bit too sensitive. That can be seen from the final log and as the hardware was not changed between original tune (which I of course couldn't read) and my final tune I think there really was not real knock happening. I changed some knock-related values at cylinder 10, though.

MAF was still pegging from 5800 rpm, but I was able to fix that with PE changes.

So that was that, unless there are some problems with normal street driving.

270 osakaasun ilmamassa.hpt

272 seos nyt ookoo.hpl