Mazda 6 2008 - Diesel Run-away - Air intake cut off

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Wed 23 Oct 2013 19:35
Mazda 6 2008 - Diesel Run-away - Air intake cut off - Med

Hi Everyone, have not been on here for a while!

I was just wondering that if a car, such as the Mazda 6 diesel 2008 2.0tdi was to run-away on its own fuel, by turning off the ignition - would it cause the run-away to stop?

My main reason for asking specifically about this car, is that i need to know if it has an air intake valve which shuts off when the ignition is off....knowing one of the ways to stop an engine run-away is to starve it of air.

Your response is much appreciated.

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Wed 23 Oct 2013 22:34
Mazda 6 2008 - Diesel Run-away - Air intake cut off - injection doc

when a diesel engine runs away its normally due to the fact that its running on oil/diesel mix from the sump or via a breather or turbo so switching off the ignition would have no effect !

Our coaches years ago used to suffer with runaways once the engine had done around 500,000 miles, if you were very lucky you could stick in 6th gear & drop the clucth but normally it would just strip the clucth and carry on running untill it disintigrated !

Some diesel engines now have a throttle flap that shuts when the ignition is switched off but its fitted to help with the way the engine stops and ensures a smoother stop, how effective one of these would be in the event of a runaway I do not know , it may even p[rovoke the situation as the engine will try and draw air else where which inturn may draw more oil !

I must add that most of these manifold throttle flap motors have plastic gears and are prone to shearing so how a throttle flap would cope if an engine was running at full chat would be anyones guess

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Wed 23 Oct 2013 23:23
Mazda 6 2008 - Diesel Run-away - Air intake cut off - craig-pd130

In diesels with DPFs, the intake flap is closed during a regeneration to help the process complete, so the engine would probably keep running even if switched off.

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Thu 24 Oct 2013 10:43
Mazda 6 2008 - Diesel Run-away - Air intake cut off - Peter.N.

The only sure way of stopping it is to physically block the air intake, so if you are concerned carefully examine the air ducting system to find the easiest point to access and block it before it happens.

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Thu 24 Oct 2013 11:47
Mazda 6 2008 - Diesel Run-away - Air intake cut off - bathtub tom

In diesels with DPFs, the intake flap is closed during a regeneration to help the process complete, so the engine would probably keep running even if switched off.

The engine would need to run during regeneration. The intake flap cannot therefore be cutting off the air supply.

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Thu 24 Oct 2013 15:42
Mazda 6 2008 - Diesel Run-away - Air intake cut off - craig-pd130

The engine would need to run during regeneration. The intake flap cannot therefore be cutting off the air supply.

According to Jaguar's factory manual for its V6 diesels (of course the exact routine will vary from mftcr to mfctr):

During the active regeneration period:

- The turbochargers' vanes are maintained in the fully-open position to minimize heat transmission from the exhaust gas to the turbochargers and to reduce the rate of gas flow through the particulate filter. This enables optimum heating of the particulate filter. If the driver demands a higher torque the turbochargers will respond by closing the vanes as required.

- The throttle is closed as this assists in increasing the exhaust gas temperature and reducing the rate of exhaust gas flow, both of which increase the speed at which particulate filter is heated.

- The exhaust gas recirculation (EGR) valve is closed as the use of EGR lowers exhaust gas temperatures and therefore makes it difficult to achieve the regeneration temperature in the particulate filter.

- The glow plugs are sometimes activated to provide additional heat in raising the temperature of the particulate filter. To maintain glow plug serviceability the activation period of the glow plugs is restricted to 40 seconds.

Edited by craig-pd130 on 24/10/2013 at 15:43

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Thu 24 Oct 2013 16:15
Mazda 6 2008 - Diesel Run-away - Air intake cut off - bathtub tom

>>The throttle is closed

I've never seen a diesel with one of them!

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Thu 24 Oct 2013 17:28
Mazda 6 2008 - Diesel Run-away - Air intake cut off - craig-pd130

Most diesels now have a butterfly flap in the mouth of the inlet manifold (or nearby), partially to stop the engine shuddering when switched off, and now to partially close the inlet when regenerating. The default position when running is wide open ...

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Thu 24 Oct 2013 19:26
Mazda 6 2008 - Diesel Run-away - Air intake cut off - injection doc

Med, in answer to your question talking to a colegue he confirmed throttle flap wont stop runaway engine , he has seen runaways suck everuthing in including dipsticks when the throttle flap shuts !

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Thu 24 Oct 2013 19:53
Mazda 6 2008 - Diesel Run-away - Air intake cut off - gordonbennet

Hmm.

This is a frightening thing when it happens, a manual you could hopefully stall, a proper auto you might slow the engine up enough in Drive to stuff something in the air intake to shut it off (assuming the parking brake will hold which i doubt), an automated manual or DSG type box i expect wouldn't allow a gear to engage, if it did it would probably be first or reverse, not handy.

Would take a brave soul to lift the bonnet on a car screaming itself to destruction then get close enough to plug the intake.

Fire extinguisher might work, 6 feet away would be about as near as i'd want to be.

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Sat 26 Oct 2013 12:18
Mazda 6 2008 - Diesel Run-away - Air intake cut off - Med

HI Guys,

Thanks for your answers. I am going to start another post, which again answers would be great and its for ease of reference for anyone else looking for the same answers...I do apologise in advance as its about biofuel!

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