daedream

Hey everyone, new to the scene. Been reading a lot of good stuff on the forum but my first post... hehe. The forum is really awesome btw.

I have a couple of questions I wanted to ask you guys since I've been reading stuff on here. The first is, is the search function limited to only like administrative people? or is the whole thing down? I have some particular thing I would like to look up but haven't been able to use the search for the past month that I've been here. I've tried google search on the site but it doesn't really turn up many results. So i've been chugging through all the pages. So far i'm only up to page 15.. *sigh* but it's ok... been coming up on good info that i wasn't looking up while going through them. =D But having a search function would be nice so if someone could clear that up for me. Thanks.

The second question is regarding the ECU. I've read lil bits on what it is and what it does, but just to be clear, it would be great if someone could give a good definition of what it is and does. And the whole thing about resetting the ECU. The procedure to reset it and what the benefits are and that business. I've read two methods on the forum, 1) a whole list of procedures with stepping on the gas a x number of times in 10 seconds and some other stuff and 2) disconnecting the battery completely overnight. If the second method really works, then what's the point of doing the whole complicated first method? And after you reset the ECU, is it like breaking in a car from scratch? Something similar to when you break in a new car when you first buy it? And as a side question while I'm at the topic, can you guys share the proper way of breaking in a new car? to get the best performance from your car. I think people have different theories on it, like some say you shouldn't go beyond 60 for the first x miles and some say like not to go beyond 3000 rpm for x miles. And then should you push the car to the limit afterwards? I'm a newbie both to the maxima scene and also as a car owner so I'm really curious as to how to teach the car good "habits" when you first buy it. My car's not new though. Just curious, and also just for know how when I buy a new car later on in life.

Thanks again everyone.

housecor

iTrader: (2)

Search is only for contributing members.

For instructions on resetting the ECU, check the FAQ and How-to's stickies. Think of the ECU as the computer that helps run your cars electronic functions.

Your owners manual should detail how to break in the vehicle.

Oh, and welcome to the org!

daedream

I couldn't find the ECU resetting instructions in the How-to section. Can someone tell me where I can find it? And what good does it exactly do your car when you reset the ECU?

crispykid717

iTrader: (7)

From Studman's website...

http://maxima.theowensfamily.com/ecu.asp

I might be wrong but resetting the ECU is good when you add an intake or exhaust so the car can "learn" the mods right away. If I'm wrong someone correct me.

daedream

thanks....... this also works for 2001 models?

crispykid717

iTrader: (7)

I think for 3.0 5th gens you just have to unplug the negative battery cable.

spirilis

iTrader: (2)

The ECU, aka Engine Control Unit, is a small computer located under the dashboard of your car. Think of it as the neural network of the electronic functions of your engine--fuel, ignition, etc. are ALL controlled by the ECU.

Our cars are a hybrid mechanical/electrical system, with the engine and drivetrain comprising the mechanical parts, and is ultimately the most important part, however the mechanical components of our car are directed electronically by the ECU, which controls all the different pieces of electrical equipment that directly control mechanical stuff.

As any computer is nothing but a device which accepts input, performs some intelligent processing of that input, and then produces output, our ECUs are no different.

Their inputs include various sensors (MAF, aka Mass Air Flow sensor, various Crank position sensors which detect crankshaft position as well as RPM, Coolant temperature sensors, Exhaust Gas Oxygen sensors, etc.)

The processing includes various software (stored on a Flash ROM chip; the ECU is a small computer which utilizes a CPU, RAM, ROM, and some non-volatile RAM that keeps its settings using battery-backup to maintain its information; kinda like the CMOS on your PC's motherboard) which uses algorithms for computing the parameters for its outputs.

The outputs include chiefly Ignition (the ECU has direct electronic control of the ignition coil for each cylinder's spark plug--our ignition systems actually use a SEPARATE COIL for EACH spark plug) and Fuel. The ECU needs the inputs such as Crank position/RPM to determine WHEN to activate each injector and ignition coil, and it needs to know the amount of air coming into the engine (MAF), along with the engine's temperature (ECT, aka Engine Coolant Temperature), and the feedback info of the air/fuel mixture ratio (Oxygen sensors) to determine HOW MUCH fuel to put into each cylinder.

The ECU probably does a lot of other things, including control Emissions-related features (Evaporative emissions canister purge valve, possibly EGR stuff), and it also maintains our idle by controlling an air bypass valve electronically which allows the ECU to manually adjust the amount of air coming in at idle.

On 2002+ Maximas, the ECU is also responsible for adjusting throttle position, as the 2k2+ VQ35DE-based vehicles use a "Drive-by-wire" system where the accelerator pedal does nothing except operate a variable resistor (which the ECU reads via a circuit), and the throttle plate itself is electronically controlled.

I'm sure I'm missing a few other things, but that's the gist of it--The ECU is the BRAINS of our car's engine. Old engines which were mostly all mechanical used primitive electronics, mainly only for ignition, while most other functionality (fuel delivery, actual selection of the spark plug to fire, etc) were done mechanically through the carburetor/breaker points/distributor/etc. Our cars are electronically controlled using the computer.

As for years and applications for the technologies listed above...

All 4th gen (95-99) and later Maximas definitely use 1 ignition coil per cylinder, along with the relevant crank position/RPM sensors and so forth. Basically all engines under the VQ platform (VQ30DE, VQ35DE, any variants) use a similar design.
VQ35DE's also contain variable intake valve(? correct?) timing, which I believe is ECU-controlled as well.

All 5th gens and later (VQ30DE, used in 2000-2001, and VQ35DE used in 2002+) also contain a Variable Intake manifold, which is collectively called the VIAS. The switchover point from the low-end torque runners to the high-end horsepower runners is ECU-controlled as well.

imjd

That was a great explanation, spirilis!
One other tidbit that might interest daedream: just as you can flash the BIOS of a PC to update it, the ECU has a flash EPROM, and people (http://www.technosquareinc.com - there might be others too, this isn't a commercial endorsement) have figured out how to tweak the parameter table that controls things like the spark advance map, mixture stoichiometry and the rev limiter. (and speed limiter.) These guys can add several hp to your engine with no physical alteration beyond reprogramming - a good example of spirilis's point that the engine is not just a mechanical system any more.

This technology is hardly unique to Nissan; in fact there is a Federal standard, OBD-II, which dictates a standardized connector and communications protocols and a minimum number of functions that must be supported by the ECU. In states where an emissions inspection is required, part of the inspection is to poll the ECU for current and historical information about any malfunctions or out-of-spec operation of the engine management system. All cars sold in the US since, I think, 1994 model year (not 100% sure on that date) have been required to comply with the OBD-II standard, which effectively dictates the use of a digital engine management computer. (Some early designs, such as Chysler's Lean Burn of the mid-70s, used analog computers to generate the spark advance tables. But I digress.)

daedream

WOW! thanks spiril and imjd for the detailed explanation!

is crispykid correct though in pointing out that disconnecting the negative clears the ECU? or do you have to follow the step by step procedure?