[TVRProwler]

Does disconnecting the negative battery terminal reset the ECU?

 

[AndyM]

That's the usual way to do it yes. Some cars need an hour or so for the reset to occur whereas in others if you disconnect the battery and hold down the brake pedal it resets it straight away and others you can do it by pulling a fuse. Others have a sequence of things to do. When I've wanted to do a reset on my E39 I've just left the negative cable detached overnight to be on the safe side.

 

[dnyman]

What are the benefits does resetting the ECU, and why would you want to do it?

:?

 

[AndyM]

A few reasons.

If the engine isn't running as smoothly as it should.

If you have made any modifications such as changes to the air intake.

Can be used to improve performance (some say it can give 10bhp more on a rolling road)

Basically resetting the ECU is supposed to let it forget how the car has been driven before as the fuel map is reverted to standard. This can be useful when changing from standard unleaded to super unleaded but that isn't a concern as the 1 is meant to always be driven using super. There are two ways to do the reset.

1. Reset the ECU, let it idle for 20 minutes without touching the accelerator and then drive as you always drive. This should give you a good mix of performance and economy.

2. Reset the ECU, let it idle for 20 minutes without touching the accelerator and then 'drive it like you stole it'. This is where the performance increase is meant to come from. Whether it actually does or not I'm not sure as I've never put any of my cars on a rolling road after a reset but it does appear to make the car drive smoother.

 

[TK38]

Sounds interesting... Cause i recently purchased a K&N filter, and i put at air scoop thing like u get on the gruppe M kits.
Do you think reseting the ECU would increase the performance?

 

[AndyM]

I think it would be a good idea in this case as you have changed the breathing of the engine and a reset will help it to learn the new setup.

 

[TVRProwler]

Would this wipe off the effects of the remap I have recently had done and put things back to standard?

 

[TK38]

Ok.
But are their any other side effects?

 

[AndyM]

TVRProwler, as the map is written into a chip it shouldn't but I would check with the person who did the remap just to be on the safe side. The remap should be the new base settings and you shouldn't be able to loose those.

TK38, ressetting the ECU can make things behave oddly for a short time as the ECU self learns again but would be no different from when you first got the car. The difference now being that you can drive it normally and not as it would have been when the engine was being broken in. Auto boxes will also reperform their learning and may not shift the same as they did before the reset but everything should settle soon enough. The only other side effects will be things like the radio possibly losing its settings.

If in doubt - don't I have never had any ill effects from performing an ECU reset though.

 

[weasley]

This can be useful when changing from standard unleaded to super unleaded but that isn't a concern as the 1 is meant to always be driven using super.

Just a quick note on this - any car sold in the UK has to be capable of running on 95 RON fuel without damage. The 1er may prefer 97/98 and BMW may recommend it, but it'll run fine on 95, perhaps with the edge taken off it. I ran my 130i for 6 months on 95 RON until recently; now I only feed it 97/98 and the improvement was immediately noticeable (not huge, but noticeable). I didn't reset the ECU or anything, just drove it.

I personally think that there is no need for the average home punter to bother with the ECU.

 

[TK38]

Cheers AndyM, ill first look around on other forums to see what their outcomes have been.
As for weasley, yep running on 98 makes for a diffrence. It seems that extra bit eager to go, plus it runs smoother and quieter.
I use to run 91 on other 4 cylinder cars, and never really noticed what difference it made until 1 day i accidently used the wrong gun (sigh beautiful mistake :roll: ). It made it feel like a silky V6. Running 98 on my Honda Type R makes it rev quicker and happier aswell. Good stuff i say!

 

[AndyM]

Yes you could run the car on lower grade fuels but why would you want to? It will be Super unleaded all the way for my baby.

Modern ECUs should adapt pretty quickly to fuel changes due to it having knock sensors without the need for an ECU reset but that wasn't the question

 

[TK38]

Plus ive been reading that lower quality fuel slowly kill your engine cause it builds up grime on the valves. Thus reducing engine output in the long term and short term. Lose - lose i say....

 

[AndyM]

The super unleadeds are supposed to contain a superior additive package and so therefore are meant to keep engines cleaner. With low quality fuels the injectors can become clogged more easily and performance is reduced.

 

[weasley]

You're confusing low quality with lower RON. You can get high quality, regular RON fuel you know! Equally you can get ropey high RON stuff too. Not wanting to point fingers without any evidence, but I won't be putting any supermarket high RON (or regular RON for that matter) fuel in my car.

 

[AndyM]

Not confusing anything. The higher RON fuels are claimed to contain a higher quality additive package than lower RON fuels even if it is from the same company. The only mention I made to the quality of the fuel was also correct in that lower quality fuels, from wherever, can lead to clogged injectors etc. Independent tests found that the best fuel is actually Tesco 99.

 

[TK38]

Im leaning towards what AndyM is talking about.
I always believe that RON = Octane.
Plus yes i know for a fact that the valves and injectors can clog, so that not being confused in anyway.

 

[TK38]

Im reseting my ECU tonight.
Ill report on how it goes.

 

[TK38]

So ive done it.
So:
1. Initially the gearbox was slighty jerky, as it was looking for the gear that i wanted.
2. Very slow for some reason. (im guessing cause the past 2 days its been hot, and prior was decent 20~ degrees C)
3. Fuel consumption risen (maybe cause ive tried the "drive it like ya stole it!" approach)
Ill try to report back when i drive it night or slightly colder weather to compare to before.

 

[shoukov]

Can someone explain the procedure for resetting the ecu?

Is it simply disconnecting the battery cables? Just one of them? Or both?
And for how long? What about depressing the brake pedal? Is that necessary?

Cheers all