What does an Access Port do exactly?

If you have been reading about Cobb’s Access Port, or engine management for that matter, you have probably come across the term “Re-Flash”.

There is a computer in your car that is in control of all of the engine’s running parameters, and it is constantly monitoring information from a number of different sensors to make sure that your engine is operating at its peak performance.  The term “Re-Flash” refers to going in and changing some of the parameters that your cars’ computer is using with the goal of improving your engines’ performance.

Simply put, the Access Port plugs into your OBDII Port (which your car all ready has), and is able to communicate with your cars’ computer and give it a new set of parameters.  The Access Port can change things like Ignition Timing, Fueling Curves, Boost Curves, etc., and by doing do, it will allow your motor to produce more power.  Once it up-loads these new parameters to the cars computer of ECU, they are saved so they will remain there until you choose to change them. 

This process of up-loading new parameters is called “Re-Flashing” your ECU.

One interesting thing about Cobb’s Access Port, which is unique, is that it can do two different kinds of “Re-Flashes”.

The first is called installing a “Base Map”.  If you think of your cars’ ECU in terms of your home computer, it is actually similar in that it has something equivalent to hard-drive memory, and RAM memory.  When you install a “Base Map” (as you will have to when you install your Access Port for the first time), all of the new parameters will be saved to the ECU’s hard-drive.  That means that they will remain there until you choose to change them, or remove them, even if you re-set the ECU, or the system loses power, etc.

The other type of Re-Flash is called a “Real-Time Map”.  This Re-Flash is not saved to your ECU’s hard-drive, but is rather saved to your ECU’s RAM.  This kind of Re-Flash goes much quicker than a Base Map, but it is not as permanent.  Because it is only saved in the RAM, if you re-set your ECU, or the system loses power, the Re-Flash will be lost.  For this reason, it is better to use this for a Re-Flash that you won’t need permanently such as a “Valet Mode” Map.

So if all you are doing is changing the running parameters of your engine, how much power can this really make?

Well, the answer to this is a lot. 

Cobb has posted Dyno Charts of their Stage 1 maps, and in virtually every case, a car can gain a substantial amount of power just from a re-flash of the ECU.  For instance, here is their Dyno-Chart of a Stock 2.0 Liter WRX compared to the same car with thier Stage 1 Map on it:

   

The other thing to keep in mind though is that the Access Port will also give you the ability to load a MAP that goes with other parts you put on your car, such as a Turbo-Back Exhaust.  If you compare the Dyno-Charts of Cobb’s stage 1 to their Stage 2 (which includes the addition of a full Turbo-Back exhaust with a corresponding Re-Flash), you can see that there is a definite difference in power.  However, if you were just to put on the Exhaust alone, you wouldn’t realize nearly as much of an increase because you haven’t changed your engine’s running parameters to go along with your new exhaust.

Jon Cooley

Comments

[Adam]

Can the Cobb Access Port re-flash the ECU back to stock parameters?

[Jake Ryan]

will an access port put stress on the stock turbo or any other parts for that matter? mess with any warrenty?

[Moises Ramirez]

I will be buying a cobb access port in the future for my 06 sti, and would like to know if I can install that myself. I am a new subaru owner so I dont know what are the steps to take. Also will I need anything else other than the access port for it to work?

[J. Cooley]

Yes, you should be able to install the Access Port yourself. I would recommend reading Cobb's manual, and see what you think after that. Here is a link to that on Cobb's site:
http://www.cobbforums.com/forums/images/ap_2.0_manual_Subaru_2.5L.pdf

Also, the Access Port comes with everything you would need to install it, and has maps for both a Stage 1 and Stage 2 car.

[prasun]

Is there an Access Port for the 2008 Impreza 2.5i

[Craig]

Will the Access Port provide maps for turbo upgrades?