BLiu

Hi All,

First a little background on myself. I have a BS in Electrical Engineering and a PhD in System Integration. However, I have the equivalent of a 1st Grader when it comes to automotive tuning. I would think, though, that some basic fundemental theories should apply to all backgrounds and specialties.

I have been reading and searching on the topic of ECU reflash vs. ECU piggyback for a while now. From the excerpts it has been my impression that the ECU piggyback seems like the way to go for higher HP cars because a car can be tuned better with the piggyback versus a reflash.

Here is my question:

Removing the variability of a given tuner's expertise or the quality of the product, how does the piggyback ECU provide a better tune than a reflash?

Things I do know:
1) I can understand that the piggyback allows for multiple maps and curves so you can quickly go from one config for one environment and a second config for a second environment. The ECU reflash probably only gives you one set of maps and curves. But that one set should be the same as in a piggyback and if that one set is the best tuned set for the given ennvironment, then, technically, the tuning is equal. The piggyback just gives you greater flexibility to run different sets of config parameters.

2) I don't see how a piggyback makes tuning better than a reflash since the ECU is still the Master. The master will always collect the same input sensor data regardless of whether you have a piggyback or not. The piggyback is always dependent on the input data from the master. So, technically, you are working with the same dataset whether you do a reflash versus a piggyback.

3) I know that piggybacks were an alternate (and expensive) solution to reflashing the ECU and was the ONLY solution if the manufacturer refuses to release the codes. For example, Lexus to this day will not allow domestic aftermarket tuners to break the ECU codes. One aftermarket Lexus domestic tuner has offered a piggyback ECU solution by splicing into the electrical wiring going to the ECU to tap signals and sensor data and change specific parameters. If anything, the ECU reflash would have BETTER performance albeit, in nanoseconds, since it does not have go to a piggyback to do the processing.

So, to me, the bottom line is that comparing product to product an ECU reflash can give you the same single set config parameters as a piggyback ECU but without the flexibility of having multiple sets of configs and parameters for different environments, maybe an average of all the multiple sets (would that be even useful?). If that's the extent for "better" tuning then I understand and thus the tuner's skill will play the all important factor of "better" tuning (and I definitely DO NOT want to go there ). However, I would like to know if there is something I am missing. I appreciate and thank anyone for additional information and things that I most definitely have overlooked. Remember, I am a first grade equivalent automotive tuner...

Brent

bishiboy

iTrader: (10)

The main benefit of piggy-back over re-flash is your ability to tune it yourself when you add mods.
Unless you spend the thousands of dollars for a reflasher, and know the code, the piggy-back provides the flexability to adjust when you want.
Unless you live near one the the re-flashers, piggy-backs and stand-alones are the way to go if you plan on adding mods.
The other benefits are what you already said: different maps, datalogging, bla bla.

BLiu

I agree flexibiility is the key component feature for the piggyback. BUT, the bottom line is that the tune would be no better than a reflash given the same tuner...correct?

I just want to get it in my head (of course confirmed by others) that the piggyback is not a better tune but just greater flexibility. Right?

Brent

bishiboy

iTrader: (10)

Correct..to a point. If you start getting into the extreme HP numbers, the standalone is the recommended route. Not really sure why, but I've read it from at least 3 tuners, even Big Al says so.

95GSXtoEVO8

iTrader: (3)

They both [flash and piggyback] do the same thing, which is to say they allow for tuning of the fuel curves and/or timing. Both are only as good as the person doing the tuning. Piggy-backs of course have more flexibility and flashes have cool features like increasing the redline value, removing fuel cut, etc. I plan to have both done.

BTW recently a tuner made 444awhp on a reflash, so it is possible to make good power with them.

Eric Lyublinsky

iTrader: (5)

Brent,

Why is a piggy back better then reflashing the stock ECU?
I'm a Xede user and everything I will be posting why the Xede makes more power then a stock ECU is only to be understood as it's based on the Xede from Vishnu and no other piggy back on the market.

Smoother?
More load points then the stock ECU 20x20 fuel spark and boost.

Makes more power then the stock ECU?
Yes because you can control 1/10th of a degree instead of whole degrees of ignition advance. That means you can run the car closer to knock threshold with out detonation. Example you get a knock count at 4000RPM at 60% load. Stock ECU tuning pull 1 degree of timing and no knock. Now with Xede you can pull 2/10ths of a degree and not get a knock count witch would means that you did not have to sacrifice power for safety.

Yes a piggy back sit does not have full control of the ECU but if the piggy back is tuned correctly it can make almost as much power as a standalone. Almost because in standalones you can set the knock sensors sensitivity or just turn it off. The factory’s computer is very knock sensitive.

If you have any direct questions please post them.

Eric

BLiu

Hi Eric,

First of all thanks good info!

More questions:
Regarding the Smoother subject above:
Please define load points. To me, it sounds like smoother would be due to a greater representation of discrete points for a curve. Why would the stock ECU have less of an ability to increase its sampling rate either in representation OR data collection? The only limitation would be RAM size since the more discrete points you carry, the larger the memory will be used.

Regarding Timing control:

Again, if both the stock ECU and the piggyback are computers, then each can control timing in the same manner UNLESS, the stock ECU has hardcoded timing control to integers for degrees rather than decimal points - is this the case?. And even that case, how will a tenth of degree effect overall HP?

Thanks guys! Sorry for so many questions but I want to learn.

Brent

Eric Lyublinsky

iTrader: (5)

I aswered under your ?

MalibuJack

iTrader: (5)

Let me add that the features of the UTEC are also similar.. The UTEC (Newest firmware) removes the limitations that piggybacks typically suffered from, which were fuel cut and rev limits that could not be bypassed, the new UTEC Firmware allows you to set your rev limit, and eliminates fuel cut. It also directly drives the Fuel injectors and the Coils which gives more control similar to a standalone, the only disadvantage I can see is that its even more important you understand what your doing when your tuning.. But that goes for any type of engine management solution. the UTEC is also capable of sub-degree timing control...

Some of the piggybacks (the XEDE and UTEC that I know of offhand) are capable of boost control. The UTEC (with new firmware) is also capable of injector scaling, and also adjustment for upped fuel pressure (which will effectively appear to raise the capacity of an injector) which can be also adjusted for.

If anyone is interested I'll be posting some info about the new UTEC features in the UTEC forum now that I've had 2 weeks or so to play with them.

Eric Lyublinsky

iTrader: (5)

Yes but the UTEC controls the timing it self it does not do it in a "piggy back" form.

So you have full stand alone fuel control now?

Also the stock ECU does not control timing with the utec control full timing. The UTEC takes control of knock retard.

Eric

jmore

I believe the ECU is doing lookups in tables of predefined size, hence the better potential resolution in the piggyback. I assume the ECU extrapolates values between cell entries, but you can see the problem if you want to change values between cells to NOT match the extrapolation. If you could allocate a bit more memory and change the table sizes and indexing in the ECU, you'd be all set. I don't believe any of the reflashes can do that though, they just change cell values.

BLiu

Thanks Eric and Thank jmore,

The LUT (Lookup Table) explains a lot for me...I deal with these in image processing so it is very familiar to me. See! Basic concepts do cross over! I understand better now. Thanks!

Something for the Reflash vendors to think about! But, this may be a limitation of the stock ECU.

Brent

MalibuJack

iTrader: (5)

You'll find most ECU's, Piggybacks, and Standalones will interpolate between entries.. The matrix for tuning on the XEDE and the UTEC are larger than the matrix in the factory ECU..

Also, Eric pointed out another good point, the UTEC does take control of timing directly, however it has very good knock detection algorithms and will retard timing when knock is detected.. These parameters are configurable. This actually has been a feature that the UTEC for the evo always had.

Each method of controling timing has its advantages and disadvantages. Some piggybacks will offset timing from stock, its main disadvantage is your timing may be different depending on several different circumstances. Its advantage is the OE Knock control in the ECU is still active (Though that can also have its downsides). However this and full control of the injectors does make the UTEC a closer sibling to a full standalone than a piggyback.

ez76

iTrader: (5)

As far as timing, the XEDE is able to effect more fine grained control of ignition timing because it can phase shift the crank angle sensor in micro-increments, effectively advancing or retarding spark events by fractions of a degree.

ez76

iTrader: (5)

As MalibuJack mentioned, this fine grained control is relative to stock timing, but strictly speaking it's as effective for tuning purposes (although it may be harder to compute actual degrees of net timing in effect unless the ECU maps and correction behaviors are known).