# Re: [EVDL] Does airbag complicate an EV conversion?



## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

Air bags are deployed because of several variables that must be triggered. There is a specialized computer in most vehicles (sometimes independent) that gets information about vehicle speed, senses impact from the front collison sensors, etc. For an air bag to deploy (unlike in the movie die-hard) the car must be moving at a minimum speed and receive X amount of G impact or pressure to set them off. It is possible if you tapped into the wiring somehow and sent a voltage to the airbags that you could deploy them. 

The sensors under the bumper are not going to do it by themselves. I studied this in detail on my Saab conversion which still has 5 'active' computers including the one for the SRS and discussed it with some experts I work with. It has never been an issue. If you are still worried just disconnect the plug off the one in your dash and take the airbag off your steering wheel while you are doing your conversion. 


Mark Ward
95 Saab 900SE "Saabrina"
www.saabrina.blogspot.com







> ---- paul holmes <[email protected]> wrote:
> >
> > Would someone talk about their experiences in gutting a car that has airbags
> > in preparation for an EV conversion? Do you have to be extra careful not to
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

For an air bag to deploy (unlike in the movie die-hard) the car must be
moving at a minimum speed and receive X amount of G impact or pressure to
set them off. 


Not true: http://www.youtube.com/watch?v=LcA240QLPX0
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

Oh yeah, that's not fake (rolls eyes)

> For an air bag to deploy (unlike in the movie die-hard) the car must be
> moving at a minimum speed and receive X amount of G impact or pressure to
> set them off.
>
>
> Not true: http://www.youtube.com/watch?v=LcA240QLPX0
> --
> View this message in context:
> http://www.nabble.com/Does-airbag-complicate-an-EV-conversion--tp15705863p15716708.html
> Sent from the Electric Vehicle Discussion List mailing list archive at
> Nabble.com.
>
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

Yes, airbags can complicate a conversion. They can be disabled
to allow modifications to be safely made and reconnected and
activated after conversion is completed. Read the factory shop
manual which you need to have anyway for any vehicle modern
enough to have airbags.

----- Original Message ----- 
From: "paul holmes" <[email protected]>
To: <[email protected]>
Sent: Tuesday, February 26, 2008 8:31 PM
Subject: [EVDL] Does airbag complicate an EV conversion?


>
> Would someone talk about their experiences in gutting a car that has 
> airbags
> in preparation for an EV conversion? Do you have to be extra careful not 
> to
> do something to set them off while all the heavy modifying is going on?
> -- 
> View this message in context: 
> http://www.nabble.com/Does-airbag-complicate-an-EV-conversion--tp15705863p15705863.html
> Sent from the Electric Vehicle Discussion List mailing list archive at 
> Nabble.com.
>
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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

I can't remember if they're set for 2.5, or 5 mph. I
think it was 5.

Most come with a plastic cap, so that when you
disconnect the harness to the airbag, you can't short
it out on accident.
peace,




> --- Idgit <[email protected]> wrote:
> 
> >
> >
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*



> paul holmes wrote:
> > Would someone talk about their experiences in gutting a car that has airbags
> > in preparation for an EV conversion? Do you have to be extra careful not to
> > do something to set them off while all the heavy modifying is going on?
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

Good point was raised about the airbag system not working on most EVs.
If yours is new enough for a seat restraint system, then you probably
have an OBD system I or II. This is what I had to do to clear the error
codes on the OBDII system and bring Up the SRS.

You will need to re-create the signal from the crankshaft position
sensor. This requires on many vehicles a "toothed" wheel (in my case
60-2 teeth)and the sensor which generates a sine wave of variable
frequency. (voltage levels vary and are not read by the ECM) On my car
vehicle speed is sensed on the right rear wheel and the ABS system
computer which reports vehicle speed to the SRS computer. You must
mount a toothed wheel on your motor shaft if the original engine used
one, and save the Crank sensor from the ICE or get one that is similar.
All of these items including the generic 'typical' toothed wheel can be
found on Ebay without too much trouble. Of course if your vehicle uses
something else it may take some other research including locating the
complete electrical manual that explains your circuitry. In my case the
Saab workshop CD had everything.

You can do tests of what signal will work by connecting a function
generator to the crank sensor connector or directly to the ecm. 1-2
volts peak to peak at 100 hz is a good starting point. This will
simulate your motor turning and let you test the circuits without
running your motor. Use a tech II or other diagnostic reader and a
manual from your car to look at the codes being generated. You can
ignore many of them because they are no longer important. (O2 sensor,
fuel pump, injectors, etc.)

What all this does is tell your ECM (Motronic on my car)the motor is
turning over and it will start your tachometer circuit back up if you
have one, your SRS light will go out and your airbags will work again.
Takes some work, but well worth the effort. I had my toothed wheel cut
on a plasma cutter to the size I needed to fit behind my accessory
pulley.

I am committed in my conversion to have everything, (yes that is
everything) that is needed for safety and comfort working again. I am
about 95% of the way there now. If I am nothing else I am persistent.

Mark Ward
95 Saab 900SE "Saabrina"
www.saabrina.blogspot.com






> Peter M. wrote:
> > paul holmes wrote:
> > > Would someone talk about their experiences in gutting a car that has airbags
> > > in preparation for an EV conversion? Do you have to be extra careful not to
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

to ensure you do not accidentally set them off start by disconnecting the vehicle battery, negative terminal 1st, hold the disconnected positive and negative terminals together to drain the capacitors that are in most airbag systems, now remove all airbags and you'll be safe until it comes time to plug the bags back in after the conversion is complete. If you are hoping to keep the airbags functional, this could be difficult depending on exactly what your car is many of the later model systems are integrated into many of the vehicles electronic modules whose functions will have to be maintained and signals faked easier for some on this list than for me. If you are going to sacrifice the airbags then they are no problem if you want to keep them you'll need some detailed info about the system specific to your vehicle


> 
> 
> Would someone talk about their experiences in gutting a car that has airbags
> in preparation for an EV conversion? Do you have to be extra careful not to
> do something to set them off while all the heavy modifying is going on?
> -- 
>

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

Excellent post, Mark.

I have a question: For your wiring do you have a
dedicated 12V batt for the accessories or a DC-DC
converter? I am curious whether the airbag system
will still function and deploy should the main battery
pack become separated during a collision.




> --- Mark Ward wrote:
> 
> > Good point was raised about the airbag system not
> > working on most EVs.
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

Airbags have gone through some revisions.
Older US air bags deploy at 200mph and are suppose to be aimed at the
chest, most people (and the design of the American car especially) aim
the steering wheel at their face. The tilt on the steering column is
suppose to be used every time(all columns with airbags have tilt), but I
set it to the proper angle as specified by the NHTSB and it really feels
weird.
European,Japanese and newer American cars have a smart airbag in which
there are 3 to 5 squibs that can fire different explosive charges based
on weight sensor in seat and speed sensor.

When the ECU is not in the circuit, I wonder if the fallback is to fire
the first squib, I would be surprised if they don't have a fallback mode.

I worried about this when I was going through the mental exercise of
designing a car. I wear glasses and people sitting to close to the
steering wheel. having it at a bad angle, the 200 mph deployment and
eyeglasses has resulted in damage to the eyes as the glass lens is push
out of the frame and...you get the picture.

Talking about racing leading to developments in mainstream auto. How
many airbags in race cars? If they are so great, why not?
1) they only work once.
2) They exist to compensate for the mediocre restraints and weak seats
people are willing to accept.
3) They do nothing to keep the body in position to help driver stay in
control during extream conditions.
While the above is obvious performance issue for racing, If
an accident isn't simple staying in control after the initial impact can
save your life.


Because of this I was thinking in addition to airbags, my design would
incliude a simple upgraded restraint. a second belt crossing the other
way across the chest. The road racers in the stock classes of the SCCA
do this and it works really well, is simple and can be used for both men
and women. It still lets the driver move around.
We put our babies and racers in 5 point harness
Then we put ourself in a 3 point harness that twists your back in a
frontal accident and lets you slide out in a broadside.
I recommend a 4 point harness.





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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

I can see why the older ones were dangerous when deploying at 200 MPH!




> Jeff Shanab wrote:
> 
> > Airbags have gone through some revisions.
> > Older US air bags deploy at 200mph and are suppose to be aimed at the
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

----- Original Message ----- 
From: "Mark Dutko" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Thursday, February 28, 2008 9:58 AM
Subject: Re: [EVDL] Does airbag complicate an EV conversion?


>I can see why the older ones were dangerous when deploying at 200 MPH!

> 
Well, not an issue for most of us as our EV's won't GO 200 mph?

Bob, lucky to get 60-70MPH.

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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

Very good point raised.

Yes, if it is an older american car it may not have seat belt tensioners either, so beware. Might be better to disconnect the system on those. OBDII series vehicles (some as far back as 95 like mine) but 97 and up should have modernized SRS systems. I am going to wire a disconnect switch on my passenger side bag like the newer cars now have. Nobody sits there most of the time anyway and if it did deploy it would destroy my dash.

If the one blows on the steering wheel they are $40-$50 on Ebay and easy to change. 
at least on my car.


Mark Ward


---- Mark Dutko <[email protected]> wrote: 
> I can see why the older ones were dangerous when deploying at 200 MPH!
> 
> 
>


> Jeff Shanab wrote:
> >
> > > Airbags have gone through some revisions.
> > > Older US air bags deploy at 200mph and are suppose to be aimed at the
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

I think he was referring to the speed the airbag deploys not the vehicle speed, otherwise they would never come out for normal accidents.




> ---- Bob Rice <[email protected]> wrote:
> >
> > ----- Original Message -----
> > From: "Mark Dutko" <[email protected]>
> ...


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## EVDL List (Jul 27, 2007)

*Re: [EVDL] Does airbag complicate an EV conversion?*

Beware!

Airbag (SRS) equipped cars have a secondary power source and may be "live" 
for some time after disconnecting the 12V battery. Refer to a good shop 
manual on how to properly disarm/remove any airbags before doing major 
electrical modifications.

-Adrian

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