Start: Debate
Well its been a while since i added something here and been meaning to write this up.
So hear goes:
Definition:
Piggybacks "black box's" are units that work along side the stock ecu rather then eliminate it all together. They intercept/modify signals from your engine sensors that go to the ecu (or vice versa) and modify them to suit your needs. Some piggybacks can replace certain functions of the stock ecu as well. For example the SMT7 able to take control of the stock ecu's O2 sensor trim so you can tune to a user set AFR.
What can you do with a piggyback?
Piggybacks are more commonly used to help the stock ecu cope with larger then stock injectors as well as control timing to prevent detonation caused by to much timing advance (will explain later).
Depending on the piggyback unit you can also use it to control extra injectors for water/alcy injection; launch control; open & closed loop control...to name a few.
Piggyback Pros:
-Cost: Piggybacks can do allot for the price you pay for the unit. Instead of getting a EMS just to tune in 550cc injectors, you can easily get away with a piggyback and in the end save 700+!
-Stock ECU retained: In some cases you cannot remove the stock ecu because of local laws and what not, you can get away with using a piggyback as it can be hidden an allow the stock ecu to remain present for inspection. (also some places test your DIAG port to see if the stock ECU is still there and working, which really sucks to be them)
Piggyback Cons:
-REMOVE FUEL, ADD TIMING:
This is by far the LARGEST concern on SELECTED piggybacks. When you use the piggyback to control larger then stock injectors you typically interface the MAF/AFM/MAP sensor and modify the signal going to the ECU. So say you have to pull fuel because your larger injectors are dumping to much fuel what happens is the ecu thinks there is LESS air entering the engine thus thinking there is less LOAD, well less load means that its safe to advance the timing to help with combustion. While this is fine for when you really are not putting a large load on the engine (IE off boost), this can be DEVASTATING to your engine in that since the timing has been advanced in a high load area the chances of detonation is greatly increased!
This is why I DO NOT recommend the S-AFC unit to anyone because of the fact it cannot control timing (or at least have the ability to retard it).
-ECU Battles:
Most ecu's work by FUEL TRIM, in which the ecu injectors fuel from a set map then takes a reading from the O2 sensor. If the Air Fuel Ratio is not where it is supposed to be (IE idle/light load at 14.7:1) the ecu will either remove or add fuel, now depending on how much it had to the ecu will apply that as a %.
"wheres the problem?"
Well say if you are at 50% throttle and getting into boost, and you want to add some fuel to keep away from any threat of detonation, the ECU will notice that it is getting way to rich and try to lean things out even more. Eventually the ecu will hit its limit of 20% lean max trim and fire off a check engine light. ANNOYING!
There are piggybacks that can modify the O2 sensor signal to get rid of this problem such as the SMT6 (woot).
OBD-II systems suffer from this battle the worst! (5vz & post 1mz guys using the stock ecu).
How much am I going to pay for these things?
Generally the price range on piggybacks are from a modest 450 (SMT6 at times) to a stupid 750+. However units like the SMT7 and the new Emanage ultimate both have a lot of features that offset the high prices and are still cheaper then some EMS's.
What is out there and what do you...Weasy2k....think? (Rated by
1 being the worst 5 being the best)
S-AFC:
Features:
Ease of Use:
Price:
Summary: Well the fact that it can only do fuel trim and some other minor shiz....that kinda sucks....but you don't need a laptop to tune! thats pretty cool.....at a price of around 250-400 its fairly cheap...but for what you get...bah...
Greddy Emanage Ultimate:
Features:
Ease of Use:
Price:
(if i could go HALF a eye roll i would!)
Summary: Controls fuel AND timing as well as Air fuel ratio map control with several correction maps (even one for A/T) pretty good, but at what cost...600? no thats just for the unit...add 75-100 for the harness...YES the HARNESS....want to use the AFR target function? add 18 bucks...want to use the temp compensation maps? add 25 bucks....how about the map switching ability....yeaaaaa....28 bucks...
So for a total 770 bucks you get the greddy e-manage......
"The Greddy e-manage Ultimate does what no other piggyback ECU can, "
SEE: SMT6 and to beat it SMT7
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