Hi all,
I feel I need to create this thread so that those with the tools to remap ECUs don't keep asking clueless questions. Those of us who do have a measure of sense of what we're doing get frustrated by questions like these, we spend time researching and conferring with other tuners to learn. We don't just ask for pre-tuned ROMs unless we already know how to implement close to if not an identical tune.
Here are some frequently asked questions and why, when asked, you're likely to not receive a straight answer;
There are 2 reasons this isn't a good type of question;
- As our cars don't have a MAP sensor, engine performance calculations are done based on a perceived Load, this is a calculation the ECU does based on a number of factors such as how much air is passing by the MAF sensor, what temperature etc. It is not directly related to manifold pressure (aka "boost" and "vacuum").
- Every car differs, even before it's left the factory they could differ slightly due to tolerances in manufacturing process, and once it's left the factory it's a free-for-all on how the car changes, factors such as servicing, how the car is treated etc all cause differences.
In short, it's impossible to tune a car to run at a specific amount of boost, and close to impossible to get it to run close to that figure without mapping it in person.
There is a similar question that often comes in that has both the above answered factored into it and some more;
Asking for pre-tuned images for use on your (or anothers) car is a no-go. It's unreliable, often dangerous, and always downright lazy. Asking for a previously-tuned image
so you can learn from it isn't so widely frowned upon, but it's still encroaching on something that someone else has invested time in preparing.
Also, there's no such thing as a ROM that gives you an extra ??? HP, as stated earlier, every car is different and requires it's own unique map to make the most of it and handle it's subtle differences that can often result in vast differences.
An example is this; 3 identical cars all leave the factory supposedly tuned to 260 HP could meet up 5 years later and put on a dyno;
- Car 1 makes 230 HP because it's been serviced poorly
- Car 2 makes 250 HP due to natural wear/tear/age
- Car 3 makes 265 HP because its fuel pump is failing causing the car to run leaner than intended
If I was to create a generic ROM image that ups the target load (ie. loosely how much extra boost to apply) by an additional 15%, it could have the following effects on the above cars;
- Car 1 makes 240 HP because gains were harder to achieve
- Car 2 makes a respectable 280 HP
- Car 3 briefly makes 290 HP before excessive knock causes the engine to die
In addition to this, asking for gains such as +40 HP is a pipe dream unless you have sufficient backing in your wallet for supporting mods. Lets say you're tuning a manual or a facelift auto, you're already starting with 280 HP (well, 276 HP for the pedantic), if you want +40 HP on top of that (320 HP) you've already exceeded what the fuel pump can deliver, and you're also close to the usable limit of our TD03 turbos.
If you're gonna ask for 320 HP out of a VR-4, you're gonna need good supporting mods; Fuel pump, fuel pressure regulator, intercooler, exhaust system and performance air filter. You also need to start thinking about cooling if you plan on running 320 HP for extended periods (such as on track days). Once and only when you've done that, you will definitely need the ECU tuning to suit the modifications.
Here's a nice example of that last point, using the stock fuelling table after installing my fuelling modifications (Walbro GSS342 255 LPH fuel pump and a Sytec Fuel Pressure Regulator) I actually LOST power because the car was running significantly richer (AFRs of around 7-8 under WOT). I've had to set those matching entries in the fuelling table to around 12.5-13 just to bring the fuelling up to a safe 10.5-11.0 (and still I feel there's still power to be had by leaning it out to 11.5). I feel my "tune" is circa 320 HP, an upcoming dyno day will confirm that, however if my ROM was to be flashed onto a car without those fuelling mods, I'd be very surprised if it didn't go bang.
As of March 2012, not by a reflash, the ECU is set to match 0.5V from the lambda sensor but as of yet the location of this value in the ROM is undetermined. And if / when it does become possible the benefits won't be safely usable.
Stock narrowband oxygen / lambda sensors output a voltage signal between 0-1V with the
stoichiometric air-fuel mixture of 14.7:1 being around 0.5V, there is very little room to change this because the change can often be very sharp (
here is a
very optimistic narrowband graph), if you were to aim for 14.9:1 the voltage would be around 0.2V, not leaving much room between potentially running much leaner.
It's
fairly well adopted that a cruise AFR of around 15.2:1 is beneficial to fuel economy on 8G VR-4s, the only safe way to achieve this is to use either a wideband kit (such as the Innovate LC-1 or MTX-L), or a fuelling computer, that has a programmable narrowband emulation.
That said, economy benefits can be had by advancing timing a few degrees (no more) around the cruise areas.