I'm confused.

After reading several threads here there are posts suggesting that the so-called piggy-back tunes don't stay at the levels they had when first installed. That the car's CPU "learns" and reverts to the original stock tune over time.

I've asked a couple vendors who supply PB tunes and they say this is not true, yet there are vendors who say that this does happen.

What's the concensus regarding this? Any proof in either direction?

 

I will give you the engineering answer, NO. There is a thread on piggy back tunes vs flash tunes here. I designed control systems, my advanced degree is in systems and signals. The piggyback will continuously compensate for whatever the ECU does in the forward loop beyond it based on the operating parameters decided on by the piggyback software designers. These piggybacks aren't a resistor and a transistor, they are complicated software packages that implement a complex sampled data control algorithm that will maintain it's control targets.

 

And as far as I understand OBD 2 flash type programming like the GIAC tune, it becomes the programming for the ECU.

So, in other words, Porsche has turbo boost limits in the original ECU programing. The GIAC tune replaces those with GIAC specified limits, so the GIAC boost limits becomes what the ECU tries to maintain. It is not competing against the original programing, it replaces it.

Anyone feel free to correct me if I am wrong. I do not wish to spread misinformation.

 

That is 100% incorrect. There is no sensor output that you can modify to alter the torque requests in the DME. You can either change them from inside, or they will continue to adjust down until the request is met. Limp mode is common with piggybacks after a certain amount of time because the DME runs out of items to turn down.

 

100% incorrect? I didn't say anything about a torque request in the DME so how is what I wrote 100% incorrect? Nothing I wrote is incorrect. The piggyback causes the ECU response to be changed WITHIN IT'S OPERATIONAL PROFILE such that more horsepower and torque are output under different load conditions based on the software program in the piggyback.

This is what is wrong, it's just gibberish. My car has never gone into limp mode with the piggyback and it produced a substantial increase in performance as documented, which is repeatable and just as good as the results posted by people with your tune. I have actually posted Vbox results here which provide substantially more info than drag slips do. They also ensure that we don't have to rely on bogus speed measurements from rinky dink dragstrips that don't have good equipment.

I can make a torque request to the car from the outside with my paddle shifter. It's called downshifting to increase rpm and torque. I don't know what a torque request amounts to in the DME are you sure you know what you are talking about?

 

I believe this is correct which is why Porsche would be in their right to deny a warranty request on a blown engine as a result.

 

I don't really want to get into a technical argument here, but I will say this. Not only are we a tuner but we are also obviously very "close" with a dealership....and if anyone tells you that a piggyback is more "undetectable" then a normal OBDII tune, they're lying to you. We can ALWAYS tell if a car is tuned, or has ever been tuned. There are ways.

 

I don't know where I said that anywhere in my post nor did I make any gratuitous comparison between piggyback and flash tune.

However, if you want to get into a legitimate technical discussion, feel free but so far, that hasn't been the case when it has come to piggyback and flash. I chose piggyback based on my best engineering judgment and I have previous experience with both on my BMWs.

 

I wasn't referring to your car specifically, just piggybacks in general, and there have been many reports of this happening on various Porsche models. It is also a common issue on the platform you came from (BMW owners also call it "coding" or "coding out").

You're correct that changing the boost input in the computer does change it to a different operational profile. The problem is that, the profile that you switch to is when the car is under lower stress parameters. On low boost, the factory operational profile is to run leaner Air Fuel Ratios, on higher boost, it's the opposite. Knock correction works in a similar fashion, as do things like PDK clutch pack clamping pressure.

I am glad that you're happy with your car. When it comes to personalizing and modifying, that is what truly matters.

 

I don't know ANYTHING about the engineering aspect of piggy back vs. flash. I have the Evoms piggy back on the 2011 Cayenne Turbo that was installed before I took delivery of it new in 2011. I've since given it to my son. We also have a 2011 Turbo also delivered new in 2011 that my wife drove. It did not have a tune. I've driven a 2012 Cayenne Turbo with the GIAC flash. It has a MUCH smoother "delivery" of power than the Evoms. The other day our 2015 Cayenne Turbo arrived and we still have our other 2011 Cayenne Turbo. The plan was for me to drive the 2015 and my wife to continue to drive the 2011. Unfortunately I think she has commandeered the 2015. Once this settles out (and I already know how it will) the one I drive will be tuned & have secondary cat bypass pipes installed. It WILL be the GIAC. Just much smoother. The reason the one she will drive will not be tuned is she was so turned off by the lack of smoothness of mine with the Evoms when she dove it. That being said I can't say I noticed any reduction of power with the piggy back - just not as smooth. Also I can't remember seeing a representative from Evolution Motorsports on this forum supporting their product or trying to educate us about it. GIAC is constantly here filling us in about theirs. And no, I'm not a stockholder in GIAC or my 2011 Cayenne would not have the Evoms product installed. BTW this IS a gratuitous comparison but also honest IMHO. My Cayenne was one of the first so it is possible the Evoms has been refined since then.

 

There has been an ongoing debate over BMS vs Dinan on the M5 and M6 forums and you can see how choppy the BMS piggyback is in the acceleration profile taken using Vbox. The Dinan is very linear. My wife commented after I got the Dinan piggyback how much smoother the car was to drive. It depends on the quality and complexity of the piggyback. The FVD piggyback seems to me as high quality as the Dinan. I don't know anything about other piggybacks on Porsche. As I had said on other threads, I had planned on doing the GIAC but FVD released their piggyback and they have a very good reputation so I gave them a try because my bolt ons are FVD and am not at all dissatisfied with the performance of their piggyback.

ETA:
The Dinan piggyback is around $3500 with a warranty against any issues as a result of using it and the BMS is $450 with no warranty. The FVD was $2450 with no warranty.

 

If you follow the chain of replies above, you pretty clearly suggested that Porsche would deny a warranty claim on GIAC software but not with a piggyback. I was simply saying that they'll find out either way, piggyback or traditional tune.

 

No, that is your inference. I simply commented on one way Porsche could deny a warranty claim based on something another poster brought up. With a piggyback they could find that the engine was running too hot because of an overly lean mix and that the pistons and rings had been overstressed as a result. Alternatively, they could find that a piggyback caused the car to enter limp mode frequently under aggressive driving conditions and deny the warranty.

What I think is that the piggyback when properly done has no way to cause the car to operate outside it's design parameters whereas the flash can actually change design parameters. The key here is that design parameters have room to allow for better power and torque to be made under different loading conditions than what is provided stock from the factory.

Consider a plenum where the air flow is increased due to a better design, what is the ECU going to do with that? There is nothing it can do but add fuel and adjust ignition timing in order to maintain engine temperatures within operating limits. How does an ECU adapt to increased airflow over which it has no control? Same thing with headers, how does the ECU adapt to lower back pressure?

If I can run better times repeatably after the addition of the piggyback, I would have to conclude the ECU doesn't de-tune it and for sure the ECU can't de-tune flash changes if it uses them directly.

 

Implication....inference....who's keeping track

I don't disagree with anything you've said (well, almost) but I will say this. There are many factors besides the ECU which determine how much power is delivered to the wheels of your car. If you can't also control those factors, then the ability to control power from the ECU is somewhat limited. The PDK torque limit Austin briefly mentioned is one of those specific cases where this relationship effects the performance of the 991 turbo cars. Without getting into too much detail, the PDK constantly monitors tq levels and WILL cause a reduction in power if it senses a tq level beyond it's pre-set parameters. If you can't control those tq limits in the PDK, you are limited in how much power the ECU will produce, no matter how aggressive your programming is. That is where the GIAC software excels in comparison. We have the ability to control those limits and communications between multiple sources. I understand that you have a very clear technical knowledge of HOW the piggyback unit functions in a general sense, but it's the very Porsche-specific programming that makes them a bit crippled in this case (and really...only the newer Porsche models).

All in all, I'm glad you're happy with your setup. If it's working well for you and you're happy with the performance you're getting out of it, then don't change a thing! That's what really matters. Unfortunately it doesn't seem like everyone who has tried it is as happy with the piggyback solution as you.

 

With GIAC offering a solution why anyone would choose piggy back is beyond me. I've never heard of any issues with Flashes. But issues (whether drivability or otherwise) with Piggy backs seems to be somewhat common....