I picked up a DHP PowrTuner in Dec '05, one of the first units programmed for the Riviera. I wanted to post my tuning notes so that others with the PT can follow along; if you have anything to add, please post!

April 1, 2006:

I finally got the PowrTuner up and running. Let me start off by saying that this wasn't the easiest project to get rolling.

When you order, you get a couple of cables and a black box sent to you. There's a sheet of paper with some instructions, but no install disk (batteries not included, lol).

You then have to sign up at DHP's online support forum, where you can search to find the beginner's how-to thread. Here is where you download the actual software + all of the support software if you need it. A PDF manual is also available.

Next you wait for DHP to email you a BIN file (a copy of the DHP PCM for the Riviera). This file is to be the starting point for your new PCM.

When I first used the program, it wanted me to connect up to the car. I tried to do this and realized I had no serial port, only USB. So needed to go out and buy an adaptor because it wasn't included that I recall ($25).

So I install the driver for the adaptor, start the program and connect to the car. Now I have to select a COM port and make sure it's settings are correct, and finally I get the software registered. I'm in!

Now I try to read my stock PCM and find that it isn't supported by the PowrTuner (yet), so I have to email it to DHP and see what they can do. It reads the PCM, and saves it, but I can't open it up to change anything. In order to edit, it seems I need to flash my PCM with the new BIN file that was emailed to me. Obviously, I don't want to do that until I know for sure that I have a working copy of my OEM set-up backed up just in case.

However, I've been looking at the new DHP BIN (which includes both DHP and OEM settings) and have found some really cool stuff. Of interest are fan turn-on/off, DTC enable/disable (bye bye rear o2 sensor), shift points, fuel/MAF settings, TCC control, shift pressure, timing, KR activation, and speed governor (makes Riv the faster!).

So, I won't be flashing my PCM just yet, but in the meantime I'm learning the map of my car's brain and comparing DHP's settings to stock. And there's a lot to take in - stay tuned...

April 6, 2006:

I flashed the PCM tonight. Did a full write, so old PCM code is gone, new 1.5 DHP is in. I was a little concerned that something might go wrong, but it didn't. The car started right up and I took a drive to let the car learn a little.

On my first drive I just took it easy. After about 20 miles, I opened it up a little. Everything seemed to work, so did a few WOT runs.

The car seems a bit more responsive. I can tell something has changed with the TCC settings. The TC seems to not engage as easily when I ease into the pedal, which is good. Other than that, I wasn't super-impressed by the difference. If this is what you get with a DHP 1.0 PCM, I'd definately be wanting my money back.

Interesting LTFT and O2 numbers after the reprogram. LTFT used to lock in around +8 or 10 (lean) at WOT. Now they lock at 0 every time. O2 is between 915-930 during WOT, which is perfect. The bad thing is that I've got even more KR now than I did before. With LTFT and O2 looking so good, I don't know what to do about this. I am getting 3-5º KR on every WOT run. I don't get it. Maybe the numbers will change over time as the PCM learns more.

I plan to test the speed limiter soon. Muha-ha-ha!!!

April 10, 2006:

Speed limiter tested - to near 120 mph while showing some teens in a Dodge NEON what the Riv could do on the open road. She was rock solid the whole way (I knew when I bought the Firehawks that the W-rating would be put to good use one day).

I got a "peace sign" a minute later as they finally caught up and drove by me, ha-ha.

April 12, 2006 - Tune #1:

Did my first tune today (not much, but a start):

- lowered KR activation further to -40F
- programmed fan #2 to turn on above 185F and off below 180F
- programmed fan #1 to turn on above 190F and off below 185F
- programmed fan #1 to turn on for 2 min at engine shut off if coolant temp >180F.

June 29, 2006 - Tune #2:

Set desired idle RPM to 750 (engine warm with trans engaged) today. I've noticed at the stock setting of 630 RPM the engine can sometimes vibrate the interior to the point of mild rattling. Should be smoother from now on.

July 20, 2006 - Tune #3:

Today I reset the TCC release curve. Honestly, this is so far one of the best mods I've done. It makes driving the car MUCH more enjoyable, IMO.

If you've ever been driving on the freeway at 60-65 mph and come to a slight grade, you'll notice the engine RPMs may go down a little if you try to accelerate. This is because the TCC is engaged - locked up - and the increased load on the engine is demanding more torque that isn't there. If you were climbing such a hill and needed to pass someone, you'd find that your foot would sink quite a ways into the throttle before the TCC was released, at which time you feel the power return as the RPMs climbed. IMO, this feels weak. It isn't good performance, and I've read some who say it puts added stress on the crank bearings. More importantly, if I want to go now, I want to go now - not after waiting 2 seconds.

So after checking the TCC release map with the PowrTuner, I found that the throttle % required to unlock the TCC were way too high. At 60 mph for example, you'd need about 50% throttle to unlock - that's half pedal to escape OD - and that's just stupid. Fuel economy is good and all, but when you're giving 50% throttle, efficiency shouldn't matter at that point.

What I did was bump the required throttle % down, so that it requires less pedal to release OD. You still get to enjoy OD when applying steady throttle, but when you want to go, the TCC now releases much sooner. I did this at every speed, from about 40 - 90 mph. It now takes less throttle % to escape OD at any of these speeds. The settings do not apply while in cruise mode. If I hit the cruise button, I get back the same old lazy TCC settings.

I also didn't like that the stock tables have the TCC engaging in 3rd gear (but it happens quite often), so I just did away with any possibility of that happening, Now, OD will not engage in 3rd, period.

What I've found so far is that the car feels much more responsive than it did before the tune. When I'm on the freeway, OD hangs on just fine with cruise control on, but as soon as I press the pedal to accelerate, it kicks into normal 4th. NO MORE OF THAT 'LETTING OFF THE GAS' TRICK TO RELEASE THE TCC!

In town, I used to shift into 3rd gear to keep the TCC from locking up, but now I don't need to. Sure, I loose a little fuel economy in town, but I'm driving a more responsive car now, so I really don't care! And who expects good economy in town anyway?

Nov 26, 2006 - Tune #4:

Just learned that the emissions code P420, which triggers the SES light when the O2 sensor sensor figures out the cat is gone, can be totally deactivated. Before it let me block the SES from coming on, but now the code is nonexistant. Cool.

Also improved my TCC settings even more. Last time I set these so that I didn't have to press the gas to near halfway at 65 mph to escape OD. Now, I've got it set so that even less pedal is required to go back to regular drive.

Dec 6, 2006 - Tune #5:

I'd been reading a few posts at RegalGS.org where some of the GS owners were saying they leave perf shift on all the time. So I got to thinking, do I even need a button? If it's as good as it's supposed to be, I might just leave it on all the time, so I decided to find out.

Perf shift does a few things. First, it lessons torque management. Torque management is the way the PCM "softens" torque delivery to the wheels during shifts. By commanding less TM, more power is delivered during the shifting process.

Another thing perf shift does is lowers the shift time. The stock value was .45 secs for a "smooth" shift. Now it's .01 secs... of course the tranny doesn't really shift that fast, but it tries to!

Trans fluid pressure is increased with perf shift on. For wot and harder shifts, the PCM will command the max value of 96 PSI much more often than with perf shift off. This results in very firm shifts.

Finally, perf shift sets the shift points raised slightly from stock. This lets the engine make power for a longer time, and then puts you higher in the power band in the next gear. This is a definate plus for my car (power band starts at 4krpm and up); the engine seems to pull harder now. Even when just cruising around, I notice it's more responsive.

So, in order to get perf shift without wiring a button, I decided to simply copy all of the data from the "performance" tables to the "normal" tables. Now, my perf shift values are always on. No, I don't have the option of turning it off, but if you try this, I guarantee you won't want to either.

Shifts are firm. It just feels good. The car is more fun to drive this way, and I never thought about how sluggish the trans was, but wow did I ever notice! I'm sure the perf shift data and my shift kit are combining forces here, but I think it's the tune doing most of the work.

If you're thinking this could be bad for the trans, you may be right, but imo it's not so bad. The shifting is so much crisper now, I'd never go back, partly because I believe the trans is happier shifting faster, especially at wot. The clutches in particular have to appreciate what's going on here.

I really like the perf shift mod. The TCC mod is still my favorite, but this would be a close #2. As much as I like raw power, it's the delivery of that power and the drivability improvements that impress me most. And the ability to tinker and tune and see instant results is too cool. I'm starting to get the hang of this PowrTuner thing. More soon to come...

Tune #7:

After driving with Perf Shift for a month, I decided to change the values near the 2-3 shift, as it seemed too jerky during everyday driving. I tried substituting the OEM Perf Shift values in place of DHP's. The OEM Perf Shift values make for firmer and quicker shifts, but the fluid pressures and TM decreases aren't as extreme. In short, better than normal OEM, not as jerky. So far, this seems to be a nice balance between all-out performance and practical daily driving.

Tune #8:

Well, I've decided to race at the end of this month, so wanted to try tuning for the 3.2". SC pulley. The first thing I did was throw out my MAF tables that came with the DHP 1.5 BIN. I used the stock MAF values as a default. Starting fresh...

Over the weekend I slapped on the 3.2" and I did a 15 min scan for idle and easy cruising from 0-85mph. Afterwards, I got into a little heavy throttle from cruising speeds... as expected, saw some KR. At 65% throttle I was getting 3-4 deg KR sustained, not too bad, but I'm not used to those numbers. I feel I definately have my work cut out for this tune.

Last night I examined the data and rewrote the IFR (injector flow rate) values using a technique found in Webracin's chapter of the PowrTuner manual. Basically I used LTFT values to offset the flow rates for idle and cruise. I will rewrite today; expect to see LTFT values closer to zero now.

Tune #9:

After adjusting the IFRs, I rescanned and tuned once more. The results are pretty impressive. I haven't even touched MAFF values yet, and my LTFT values are vastly improved in the idle and cruise ranges. Here's what my LTFT looked like 3 days ago:



You can see how the red line (old LTFT) is all over the place, never at zero. This means the PCM was adding fuel when above the line, trimming fuel when below. These are pretty extreme considering I hardly went over 3k RPM.

Below is a scan after the tune. The green line (new LTFT) is almost always at or near zero, even though I was having a lot more fun with the throttle:



The graph shows that trims are much more stable, meaning the PCM is more in control of the fuel delivery. Now I just have to figure out how to tune for WOT and get rid of that KR. More to come, stay tuned...

so what was KR like after the LTFT tune? i thought LTFT didn't really matter at idle, and like 02 readings they were most important at WOT lock.
whats you 1/4 mile goal with the 3.2"?

Same... 3-5º KR is still there at WOT, but there's none during these scans. You have to tune idle and cruise before you can do the WOT stuff. It's like making a solid foundation for the more critical adjustments. I intend to start working on eliminating the KR soon. I just hope I can.

For idle and cruise (not a whole lot of difference between them) LTFT is the parameter that tells you how well the PCM is delivering the fuel. If it's near zero or slightly neg, you're in the money.

You're right that O2s are used for tuning at WOT. Mine are looking a bit lean right now.

If all goes well, I should be able to pull a 13.7. Not a huge improvement, but I haven't invested anything in the car since last year, so... not too bad.