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WARNING..... Welding on an SPi/ MPiCar??


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#1 Sprocket

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Posted 28 April 2007 - 07:41 PM

The SPi ECU is a delicate electronic instrument, as are many of the sensors. If you are doing any sort of welding on the car, even if its not anywhere near the ECU or sensors, REMOVE THE ECU AND DISCONNECT THE ECU GROUND WIRE. The ground wire is located on the triangular support bracket for the bulkhead crossmember, above and behind the ECU. This ground is either one or two wires terminated in a single ring crimp, the wire itself has a rigid plastic protection sleave over it.

The MPi also has an SRS ECU, same goes. I cant comment on the explosive modules in the Pre Tensioners or the AirBag, but i wouldn't like to leave them in the car as they are triggered by an electronic signal, that the welder may manage to set off!!!

Failure to do the above can result in the ECU being damaged with the high transient currents generated when welding. It is usualy scrap as so much of the electronics have been fried its normaly beyond repair.

Also while on this subject, it is equaly important to make sure that the first thing you do before refitting the ECU is RECONNECT THE ECU GROUND WIRE, ensuring all mating faces are bright and clean. Failure to do this will again fry your ECU.

You have been warned :errr:


Dont forget that the same thing will happen to your juke box so disconnect and remove that also

Edited by Mini Sprocket, 28 April 2007 - 07:46 PM.


#2 Woody

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Posted 29 April 2007 - 07:30 AM

It is also ok to weld with the battery dissconected

#3 cowboy

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Posted 29 April 2007 - 09:04 AM

which is the best way to protect everything

#4 Dan

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Posted 29 April 2007 - 10:36 AM

Don't jump down my throat but I've been told that disconnecting the battery doesn't gaurantee protection of electronics by any means. There is still a circuit present through the welder. There are decoupling devices that you connect accross the battery which will protect all equipment in the car by managing spikes and limiting current. The issue of SRS systems is very important.

#5 Bill USN-1

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Posted 29 April 2007 - 02:20 PM

there is 2 rules of thought here...
I am an offroader and have outfitted my IH Scout with an OBA-on board air compressor and an OBW- on board welder.
All of my vehicles are fuel injected.

I have personally ran my engine to operate the welder and welded on my own truck.

I have also completely welded up the exhaust on my truck and on the mini I just converted to SPI. This was with a mig welder.

If you take your modern FI car to the exhaust shop, do they completely disconnect everything before they install(weld ) the new exhaust in....
No.

The idea is that if the welder has a good ground and the electronics all have a good ground, then the welding will not cause a problem.

Now that being said...as Sprox pointed out, if you have a bad ground...then you will probably end up with a bad ECM.

just my $.02

#6 redhotmini

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Posted 26 June 2007 - 09:05 PM

if i can find them, i'll post some pics of what happens when an airbag goes off. seat belt pretensioners arent too nice either.
its mainly burns and bruises but the plastic cover really hurts!

#7 Sprocket

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Posted 26 June 2007 - 10:16 PM

Did you do this my mistake, or is it a hazard of the job?

#8 biggav

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Posted 26 June 2007 - 11:03 PM

At the Bini Factory, an hour before the end of shift, everyone used to cheer in "happy hour" every shift got louder than the last and it ended up that anyone who happened to work on a station where the car was powered (ecu programing and some fluid fills) would sound their horn.. people would also jump up and down in celebration (wearing nylon workwear)

One saturday evening, there was a huge bang on the stroke of happy hour and a car close to the end of the line deployed a seat airbag (side impact). the door was not fully closed (an operator was in the driving seat completing an ecu check and beeping the horn) the blast blew the door completley open and it recoiled and closed so fast that only 2 people (out of about 60 in close vacinity) saw it. I came in early then next day and we re-ran all the ECU checks, replaced the seat, cleared the fault codes but were unable to replicate the condition. the car was scrapped as a precaution but we found no logical reason why it happened.

The charges used in Srs systems are usually Sodium Azide or similar charge (similar to a stack of polo mints with a detonator inside) which produce a large amount of hot gas when they are activated . the rapid release of gas inflates the airbag at an alarming rate removing any trim covering the airbag to leave the area.

As soon as you hit an obstical, the SRS ecu will detect the direction of travel/force and make calculations to decide if it deploys or not. Technology is constantly updated and some airbag modules now have a "staged deployment" and will deploy a different sized airbag dependant on the size of the passenger and speed of impact. The rapid inflation is such that your face/body/ legs (depending on the airbag) will be met by the exploding airbag travelling in the other direction which once inflated deflates almost as quickly... it's not like hitting a pillow, its like having an airbomb go off infront of you and having a football pelted at your face at the same time. The calculations of which airbag to deploy or not deploy take place so quickly that from the point of impact to returning to your seat with smoldering arms and a dry taste in your mouth is quicker than the blink of an eye. Therefore they react very quickly to changes of very sensitive sensors and don't react well to tampering or misplaced electric charge.

#9 Sprocket

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Posted 27 June 2007 - 10:27 AM

All very interesting and technical.

So the bottom line is, DONT weld on a car with SRS devices still fitted????

#10 redhotmini

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Posted 27 June 2007 - 06:28 PM

Did you do this my mistake, or is it a hazard of the job?


nah just dont remove one, and drop it.

#11 TimC

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Posted 23 February 2009 - 07:16 AM

The SPi ECU is a delicate electronic instrument, as are many of the sensors. If you are doing any sort of welding on the car, even if its not anywhere near the ECU or sensors, REMOVE THE ECU AND DISCONNECT THE ECU GROUND WIRE. The ground wire is located on the triangular support bracket for the bulkhead crossmember, above and behind the ECU. This ground is either one or two wires terminated in a single ring crimp, the wire itself has a rigid plastic protection sleave over it.

The MPi also has an SRS ECU, same goes. I cant comment on the explosive modules in the Pre Tensioners or the AirBag, but i wouldn't like to leave them in the car as they are triggered by an electronic signal, that the welder may manage to set off!!!

Failure to do the above can result in the ECU being damaged with the high transient currents generated when welding. It is usualy scrap as so much of the electronics have been fried its normaly beyond repair.

Also while on this subject, it is equaly important to make sure that the first thing you do before refitting the ECU is RECONNECT THE ECU GROUND WIRE, ensuring all mating faces are bright and clean. Failure to do this will again fry your ECU.

You have been warned :D


Dont forget that the same thing will happen to your juke box so disconnect and remove that also



I have a Jap Spec 1996 SPI automatic mini, and a question about its ECU. You mention this "ground wire"... oddly after removing the ECU tonight, all i had to do is remove one 10mm nut to the left of it which is attached to the A/C, and two 8mm nuts to the front right that are attached to the grille area support beam. Is it safe to assume that those are the ground areas, and i actually don't have any ground wire at all? It runs fine as is, i'm just a bit concerned as you mention there is actually a wire that hangs off the back of it. Anybody an expert on this subject of odd Japanese spec SPI mini's with a/c and automatics?

#12 munkey26

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Posted 17 May 2010 - 08:01 PM

What a load of rubbish.

Weld all you like as it won't;

a) set off the airbags
b) ruin the ECU

#13 mrducati

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Posted 24 May 2010 - 06:02 PM

Where and what is the SRS (is that the sensor for the airbag?).
Anyway this does comply with what I've heard about welding on a car with an ECU.

#14 miniobsessed

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Posted 25 May 2010 - 05:46 PM

What a load of rubbish.

Weld all you like as it won't;

a) set off the airbags
b) ruin the ECU


Bit silly to make such a sweeping statement. Maybe you never heard the phrase "better to be safe than sorry"...

The open circuit voltage of some welders can be up around 100V which is plenty enough to make a mess of your electronic bits and bobs if it ever managed to find it's way to them. Even if the possibility of this happening is 1 in 1000 wouldn't you hate to be that person.

#15 telestrat

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Posted 14 September 2010 - 08:56 AM

So now I'm bricking it.

I've read the comments about welding on SPi & MPi cars but am still confused.

I think I would be happier to have the welding done with the ECU removed along with the air bag modules and seat belt pretensioners etc.....

Can anyone give a diffinative on is this a must (to remove ECU etc...) and in what order to disconnect / remove.

I'd appreciate a steer in the right direction on this.

Ta

ts




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