S13 Silvia Tuning

The basic theory behind retuning the factory ecu is to alter the fuel and ignition maps amongst other things like the rev limiter and speed limiter. These maps are the only thing altered, so the excellent factory controlling of idling and air conditioning remains intact. The main advantage of using the factory computer is the low cost, as very little hardware is required. Compared to the price of purchasing and installing a complete replacement aftermarket ecu, the savings are immense. The modifications are reversible too, as the wiring loom will remain untouched. This gives an advantage over more the budget orientated approach of fitting a 'piggyback' computer, which still requires wiring loom changes. The cheapest plug-in replacement aftermarket computer is the Apexi Power FC. There is no doubt over the quality of this product, but at around $2000 it is out of reach for many enthusiasts.

Eligible Nissan Vehicles

Below is a list of Nissan vehicles that can have the factory ecu retuned. Please note that this list may not be fully accurate and may not list all posible cars. The information is taken from www.925style.com/editor_direct.html

ROM TYPE	kbit	Corresponding Car	Engine
S13	128	S13/RS13 Silvia/180sx	CA18DET
PS13	256	PS13/RPS13 Silvia/180sx - U13 Bluebird	SR20DE (T)
S14	512	S14 Silvia	SR20DE (T)
BNR32	256	BNR32 Skyline	RB26DETT
BCNR33	256	BCNR33 Skyline - WGNC34 Stagea	RB26DETT
C33	128	C33 Laurel	RB20DET
Z32	256	GCZ32 Fairlady Z	VG30DETT
Z32	512	GCZ32 Fairlady Z	VG30DETT
ECR33	256	ECR33 Skyline	RB25DET
HCR32	256	HCR32 Skyline - A31 Cefiro	RB20DET
RNN14	256	RNN14 Pulsar SSS (?) - RNN14 Pulsar GTIR	SR20DE (T)

For most of these cars, such as the CA18DET powered S13s and the R32 Skylines and Cefiros, the chip in which the factory mapping is held is fully accessible by the user. That is, the chip can simply be removed, reburnt with the new maps, and put back in to the ecu. The ecu will then read the new maps as if they were factory, and never know the difference. To return to standard, just reburn the chip or replace it with one with factory programming.

For the SR20 engines, the fuel and ignition maps are inside the ecu. That is, the maps are not found in an accessible chip that can be changed by the user. Therefore, an expansion or daughterboard is required that connects to the factory ecu. This daughterboard introduce the same type of factory chips which hold the fuel and ignition maps, except they are in the daughterboard and not the ecu. The board is basically a device that tells the ecu to take the maps from itself instead of the internal memory of the ecu. Therefore, the ecu can be returned to standard simply by removing the daughterboard, and the ecu will return to reading from its factory programming.

Commercial Factory ECU Retuning

Daughterboards are not really commercially available. Companies such as Chip Torque in Australia perform a similar process by fitting an expansion board and then storing additional tuning information that the ecu will read and use. There is nothing to stop anyone from using such a company to retune their stock ecu, but it will cost much more. Of course, you are paying for their extensive experience and expertise, which is no doubt of very high quality. Dyno tuning is also involved, with before and after dyno graphs. The process is payed for as a package, with the parts and labour included. One advantage is that the car will have is the potential to be retuned to cope with future modifications.

Do It Yourself

The enthusiastic DIYer has the opportunity to attempt this process themselves at very little comparitive cost, providing they can get their hands on a daughterboard. Enter Western Australian S13 owner, 'BadBiki'. His knowledge of electronics was great enough that he was able to design and manufacture his own daughterboards. One of these units is be the basis for this project, with a individual cost of around $100 for the daughterboard. The units are of immaculate quality, and feel solid to hold. Approximatey 55mm x 65mm in size, when installed they will fit entirely inside the original ecu casing. Pictured below is a BadBiki daughterboad, on the left without chips, on the right with chips.

Multiple Maps

A huge advantage with a daughterboard equipped ecu is that multiple maps can be stored. Seen on the board are two switches, used to switch between different sets of maps. One idea is to always keep a factory set of maps as well as the retuned set. This way if the car undergoes any testing for emissions, etc, it will produce results as close to factory as any other modifications will allow. Also handy is the ability to switch to a factory or even detuned map if the car is to be driven by someone you have little confidence in. Another idea is to have high and low boost maps for turbocharged applications, to ensure best tuning for each. Perhaps a conservative map for hot days could be added, along with the no compromise hard tuned map.

The amount of maps that can be stored is defined by the type of chip used. The default chips that come with the Badbiki daughterboard can hold up to four but come with two maps. Surely four potential maps are enough for most people. This would allow with the approprate chips a stock map; a low boost map; a high boost no compromise map; and a extremely cautious map for maximum safety.

Types of Chips

There are three main type of chips available to suit the daughterboard. These are EPROM, EEPROM and Flash. All chips must be 8 bit because of the configuration of the daughterboard. The factory ecu uses a 16 bit chip, but due to the expense of these chips compared to 8 bit chips, it is logical to design the daughterboard in an 'odd and even' configuration. This means that two 8 bit chips are used to make a virtual 16 bit chip. To do this, the maps are burnt onto the chips split in half between them, with odd data on one chip and even data on the other. The daughterboard is engineered to read automatically between the two chips and merge the data electronically for the ecu to read. This is no great hassle, as the software for tuning and also that for burning the chips has functions built in to automatically to deal with the odd and even system. The SR20 ecu is 256 kbits, so the minimum size chips to be used would be twin 128 kbit chips, and these would hold only 1 map. Two 256 kbit chips will give a total of 512 kbit, and therefore will hold two maps. Two 512 kbit chips will collectively give 1024 kbit and hold 4 maps. Remember that this will vary from car to car, as the size of the factory ecu is different from model to model.

EPROM Chips

These are the cheapest and most simple of the available chips, and are those which come with the BadBiki daughterboard. The default chips are two 256 kbit units, so they hold two maps as stated above. The major downfall of EPROM chips are the way they are erased. To delete the content of the chip it must be exposed to UV light. One way to do this is to leave them in the sun for a few days. To be any more more efficient, an investment must be made in a UV eraser. These can be quite expensive but offer faultless chip erasure in only a few minutes. EPROMs are suitable for the user that will not be altering the tuning very often, or one who has access to a UV eraser. There is no reason with these other facilities available that EPROM chips can give years of faithful and reliable service.

EEPROM Chips

The next step up is the EEPROM chip. The trump card of the EEPROM is that certain types can be electronically erased with the same hardware that burns them. Beware though, as some are single use only, and will be specified so. The lesson is to double check before buying to save disappointment. Prices of EEPROM chips are about double that of EPROMs, but the cost of a UV eraser can easily make the difference. You must decide which cost will work out best in the long term. I personally invested in a set of 256kbit EEPROMs, fully electronically erasible and a direct fit. The chips were ordered from www.batronix.com under the part number of AT28C256. A document describing the chip is much detail is available here. Remember that two are required.

Flash Chips

Flash chips are similar but work on different principles. They are similar to Compact Flash memory cars used in products such as digital cameras. The technology is newer and therefore more expensive. The price pays for a greater level of sophistication, with the entire process being a little slicker than the other forms of chip. Please note that most Flash chips will not directly plug in to the BadBiki daughterboard, with an adaptor required. The main reason for someone to use Flash chips on this type of application would be because they already have some of the chips or have access to them at a discounted rate.

Ordering a BadBiki Daughterboard

If you wish to order a daughterboard identical to the one described here, please email Badbiki with the link below. Please note that this daughterboard is only suitable for the SR20DE (T) powered S13 Silvia and 180sx, N14 Pulsar GTIR, N14 and N15 Pulsar SSS and the U13 Bluebird SSS. BadBiki plans to produce daughterboards to suit the S14 Silvia and RPS13 180sx, so check back for future updates.

ORDERING DETAILS HERE

BadBiki may accept CASH ON DELIVERY for orders in Australia, but this depends on whether people abuse the privilege or not. This systems means you don't pay until you have it in your hands, and you don't get it until you pay. Therefore neither party can be ripped off.

Please note that BadBiki has other maps with alterations such as basic mapping for Z32 airflow meters and non standard injectors. These maps are a suitable base for further modification, but as no two cars arer the same, they should be tuned for each individual vehicle they are fitted to. Simply enquire with your needs and further information can be given.

Chip Burning hardware

To burn any chips you will need a chip burner. This is moderately complex piece of electronic hardware that connects to a PC by means of the parallel port or perhaps USB. Many kit forms are available on the internet where you either build the entire thing from scratch after buying the components, or purchase the components and PCB as a kit to assemble. Any person with competent electronics skill should be able build such a kit. If this is you than you are lucky because this will cost you very little. If you feel you are able then simply search the internet for "eprom programmer" or similar.

Unfortunately this is not me. I have built a few kits in the past with varying success, but I am definately not coinfident enough to build an programmer. I would either have to ask someone better build one for me, borrow, or buy a pre-assembled programmer. As I like the idea of owning it myself and few people have the time to building electronics for other people, I purchased a programmer from www.batronix.com.

The unit is the second from top called the Batronix EEPROM Programmer 3.3. The main reason I chose this product was because it supports EPROM, EEPROM and Flash chips! It will program the chips that come with the BadBiki daughterboard, as well as the AT28C256 EEPROMs I purchased at the same time. The price seemed very reasonable too, with myself ordering the already built item with ZIF socket, which along with the two chips, came to approximately $170 including shipping. Without the ZIF socket the the order would have been at least $20 cheaper, and for just the burner the order would have been around $120. Remember that the site is German and therefore exchange rates will vary the sum from time to time. Below the programmer is pictured, with ZIF socket in place.

The Batronix E(e)prom Programmer needs software to interface the computer with the burner. This software is fairly straight forward to use and will perform odd/even burner with ease.

This is the exciting part, as anyone can download the software for free and have a play. The entire credit for this software goes to Takuma Matsumoto, who provides it for download absolutely free. That's right, not shareware, but freeware. I ask that you download the software from his site, all he requires is a couple of questions for his own survey. A small price to pay for what you are getting.

The website is: http://www.925style.com, with the download page being http://www.925style.com/editor_direct.html.The pages are in Japanese, but there is just enough english to locate the download link. Be sure to click the authorisation link first, as this gives the password to downolad. Relax, this is not a scam to make you sign up to some website, but only his short survey. Also make sure that you dowload the english version, designated by the filename having a E on the end. Install and open the software.

Next you need to download an address file. This is simply a guide for the software to files with the mapping. It tells the software where the location of the main fuel map is at, and all of the other changeable aspects.

Once again in a true display of champion, the author of the software has given the address files for all of the cars listed in the table found at the top of this page. The file for both the SR20DE and SR20DET engined S13 is also available for download here:

In the software go to the setup menu and select the option vaguely describing the address file. Simply select the file from where ever you have it on your computer.

Now the last thing required is the actual files with the tuning maps on them. These files are called ROMs and are what is burnt into the chips and placed into the daughterboard. Below are links to download several ROMs for the PS13 ecu.

PS13 SR20DE ROM (fuel and ignition maps standard but global setting unfortunately changed)

Modified PS13 SR20DET ROM (apparently k value and vqmap altered to suit a Z32 air flow meter and 550cc injectors)

If anyone has some other ROMs they wish to submit then feel fee to contact me. I would personally love to see a stock S14 or S15 SR20DET set of maps.

To load a ROM into the program just go to File>Load>Load(ROM) and select the file you wish to edit or view. Up will come an ugly set of numbers under each window listed at the top. To begin exploring go to Global. This is the screen which controls the fuel, rev and speed limiters. They can be changed at will simply by typing in the number you want. Shown below is a screen shot showing the SR20DE rom altered to have its rev and speed cuts removed.

The business end of the software comes in the Hi octane fuel and ignition windows. Ignore the Lo Octane windows as these are for when the ecu senses a fault and switches to the secondary maps for safety. Right about now you might be thinking that you will never be able to tune th damn thing because you don't understand all of the strange numbers on the screen. The answer is to press Control+G, which will bring up a three dimensional map for the window you have open. This is just like those seen in expensive laptop tuned aftermarket engine management computers, and this software is free. Click on the graph area and use the arrow keys to navigate the maps point by point. Pressing the + and - keys will raise or lower the value, simple as that! If you load the same ROM from the File menu as a comparison, then the second graph will show in red to contrast any changes you might make. This is pictured below.

Have a play and have fun, but don't save unless you want to download the ROMs files again. Compare the fueling for the SR20DE and SR20DET engines to see the increased fueling requirements for a turbocharger. This is shown below with the DE in green and the DET in red. I will cover how to use the software in more detail in the tuning section.

An emulator is a electronic device that plugs inbetween the factory ecu and a laptop computer. It allows the car to run off a ROM stored on the computer, and changes to be made in realtime. This would make the factory ecu tuneable with as much speed and efficiency as most laptop programmable aftermarket computers. The catch is the cost. Badbiki is currently developing an Emulator that is compatible with all the Nissan ecu listed in the table at the top of the page. Badbiki tells that due to the intense development and complexity involved that the cost for such hardware would be around $1000. However, Badbiki in a state of sumpeme generosity hinted at lending an emulator a trusted group of people for a dyno tuning day. Lets keep on praying...

Badbiki has an emulator available to suit his daughterboard, although I unfortunately know nothing about it. For information please contact badbiki@bigpond.net.au.