joandy

This was copied from my original thread. This is something I've noticed from Chesbosto's updates with the TechnoSquare ECU threads. This might be some interesting info for you guys.

4-29-03

We have a good idea on how to tune the 350Z, but we need to do a 'heavy' mod so that it triggers the ECU to do something major to the numbers so we can find those key values, and base the tuning off what changes...... Its stock right now, we believe we can knock about 5-7rwhp more in stock form on premium pump gas...91 octane. You know how everyone is slapping on intakes and the car first gains power but then the hp goes away? Its due to a feedback control loop the ECU has for Fuel and Ignition timing... this is a new system Nissan has in all its New (2003+) cars... this number is a preset value which will tell the car to go back to its original state when it senses changes... well we just, prevent that from happening by altering this feedback number to a lower value so that the ECU cant adjust as much back.. we're testing the waters with slightly lower values and will keep on doing so until we reach a safe limit of where it dont adversely affect any safety measures pre-programmed into the ECU to prevent knocking.. but so far the preliminary results are pretty good... Ingition mapping is complete, the fuel curveis also nearly mapped out..

and

4-21-03

Dyno of the car resulted at 278 at the crank. It's from a Bosch dyno so it's not a regular dyno jet or dyno pack. It's an older dyno style that gives results in k/w... used for tuning purposes most of the time... Anyways, the ECU was re-flash with the stock program and went back and re-dyno and it was the same 278. Interesting note, if you disconnect the battery after a mod for example... you gain a few HP [3-5], but then then the computer re-learns and it brings the curve down a bit.

Sorry for the copy and paste. But the ECU isn't new to the New Nissans that Chezbosto's wrote in his thread. It's actually old. The 350z uses an OBDII (On Board Diagnostic) type II ecu. As well as every car made after 1996. (Which was the last year of the 300zx. interesting) Car's prior to that year used the OBDI type ecu.

The purpose of the EPA-mandated OBD standard was to provide a means for which factory engine controls could diagnose engine control malfunctions and identify to the driver (and subsequently the repair shop) that there was a problem. The OBD2 standard, mandated for all 1996 and up vehicles, required that the OBD interface be standardized across all makes and models, as well as monitoring emissions components performance and proper operation. This means that for 1996 and newer vehicles with OBD2 that if you remove the catalytic converter or EGR valve that the ECU will eventually identify that these components are no longer working and flag a check engine light (CEL) and OBD2 code.

What is known to the tuning world from dyno plots and tuning is that the ECU on OBD2- equipped vehicles will eventually "detune" modifications that alter cam timing, ignition timing, and air/fuel delivery. This includes common breathing modifications (intake/header/exhaust and port work). What this means for the average tuner is that when you bolt on i/h/e, do manifold or head (port) work, change injectors or fuel pressure, or just about any other engine-related mod, the ECU will detect the change in emissions and alter the timing and fuel maps to compensate. This has been dyno proven on multiple occasions with multiple different performance mods. It also happens that this is especially true for air/fuel controllers (AFCs).

The Fix
There are several ways to fix this problem. The first would be to do an OBD1 "conversion" where you replace the stock ECU with an older Nissan. This has its own drawbacks, requiring you to find/buy an ECU, a conversion harness (or making your own), etc. Even more expensive and time consuming would be to switch to a standalone system from Motech, AEM/GEMS, Haltech, etc.

While any of these would certainly be desireable and provide you with other options (such as programmability), there is a much cheaper and easier solution. Knowing that the OBD2 ECU will eventually learn and "detune" what you are working to achieve, the real objective here is to insure that your computer doesn't learn, or more accurately, "forgets" what it learns. What we will cover here is interrupting the backup power to the ECU to make sure that it does not retain it's memory while the car is off. It will "detune" while you are driving but go back to a clean slate every time you shut the engine off. Also, since the EGR and catalytic converter malfunctions are stored and only "flagged" as a problem after multiple driving cycles, these will be reset each time you start the car. This means you can install a test pipe (provided the second O2 sensor is still installed) or block off the EGR valve (or remove it) and not have to worry about a CEL. Not a perfect method, but a LOT cheaper, easier, and almost as effective as any other option.

I, personally don't have a 350z to do this. I'm just an avid 350z fan. I plan to get one by this winter. But if one of you guys wanna try to find the backup power to the ECU and put a toggle switch (On/Off) This method should work.

This mod is effectively the same as pulling the 7.5A CLOCK/RADIO fuse from the under-hood fuse panel, or removing the battery cable (all of which reset the ECU). The beauty of this mod is that you don't have to pull a fuse each time you shut the car down, If you are VERY worried about tearing into the stock wiring, you may want to just pull the fuse weekly, which is about as "fast" as the ECU learns (a few hundred miles).

Pretty much any switch will work, provided you know how to wire it as SPST. For most switches whichever end the toggle is flipped towards, those contacts are OPEN. The other contacts (facing away) will be shorted (ON). Flipping the switch alters the on/off state of each of the sets of contacts. Pick two contacts and wire them to the ECU- just be sure you know when they are shorted and when they are not, based on the position of the toggle!

This will setup will allow you to keep the switch OFF (open the backup power circuit) to keep the ECU from "remembering" anything. If you get a CEL, throw the switch back to the ON position and then it will remember the code. Just be sure you mark or know what's ON and OFF for your particular switch and wiring. By hiding the switch, this should also allow you to return the car to the dealer "acting normal." Most dealers don't like it when they can't retrieve diagnostics info!

Also the downside of this is that it voids the factory warranty (that's if the dealership can find the switch. hehe.)

This is called the OBDII workaround. Very familiar in Honda Tuning. Probably some of you people heard of this mod. This method should effectively work with the 350z as well since they use the OBDII ecu, just a different harness.

For as long as I've seen this done. I've heard of no reported problems on different forums. and so far there have been no reported issues with fuel economy or other problems. (if work-around is done on stock ecu with no modification of course.) There is no need to let your car idle for any period of time or anything else- just get in your car and drive off. It will act like normal and drive like normal, you will never know the switch is there or on or off.

Anyways. I thought this might be helpful for you 350z tuners out there. If not. Sorry for the long long post.

S12 driver

Nice! This could works as a theft prevention too. I don't think putting a swatch on a wire will be too hard.

joandy

Maybe? I dunno if that'll work for it or not. I figure it's like a car stereo with the radio stations that you preset. The memory line for the radio is used to keep power to the radio even when the car is off so it doesn't forget the preset stations. But if don't connect the memory line, the radio will still start up fine but all the preset stations are lost. This will probably be the same with the OBDII workaround.