exploding air filter box

[Auzziephoenix]

Like the title says.. my air filter box in my s2 VN exploded day while cruising at a steady 100km/h
This is the 2nd time its happened, last time is about 2 months ago when i accelerated to catch the green light.

Car is on LPG.
Any ideas?

[TVR-190]

almost certainly lpg related.

http://forums.justcommodores.com.au/...forum.php#1093

[wana s' charge stock vt]

it would be filling up with gas and exploding . i'd get it checked quick smart befor ya blow ya self up. lpg is deadly.

mates ford did similar them. except blew everything apart, intake, air box, rocker cover all cracked and the best one - haha, it blew the whole sump off. like off off, on the ground . the 10-15 bolts were still in motor and had pulled thru the steal sump.

[Auzziephoenix]

almost certainly lpg related.

http://forums.justcommodores.com.au/...forum.php#1093

cheers for that.. i didnt exactly know what to search for.. backfire never came to mind.. lol

I changed the leads and plugs around last august-september.. due to the Gas converter absolutely destroying them.. (he didnt take them off properly when installing the lpg)
it hasnt been for its first tune... will take it in asap now.. coz if i explode, media will percieve it as me speeding.. thats another bad wrap for P platers.

[levymetal]

lpg is notorious for blowing apart airboxes but it's never happened to me. with good spark and the gas tuned you shouldn't have any problems. you can also run a pod filter instead, that won't blow apart (might blow off though), but you'd want to make an enclosed area for it in the engine bay so it doesn't suck up hot air.

[BoNeZ-01]

Ok, Im gunna sound real dumb now, but I've never owned or worked on dual fuel cars, but, if the airbox blows up, wouldn't that also blow the **** outa the air flow meter's insides? $$$$?
And another dumb question, if an air intake is 'normally' in a vacuum state, drawing air 'in' to the engine, how does the gas flow 'backwards' against the flow, enough to build up in the airbox?

I have often thought of buying a dual fuel car, but when I hear about things like this happening, it makes me think twice..

[sik_dose]

my mates EL ford fairlane V8 on LPG does the exact same thing so he just unhooks the top of the air box and is done with it lol.

[woteva]

It's backfiring. Get your self some new plugs and some quality leads.
Have also seen some mods done with like a releif plate fitted to the airbox top to release the pressure when backfiring.

[levymetal]

And another dumb question, if an air intake is 'normally' in a vacuum state, drawing air 'in' to the engine, how does the gas flow 'backwards' against the flow, enough to build up in the airbox?

it doesn't. what happens is that the gas in the cylinder doesn't ignite, and when the intake valve opens an explosion can occur in the intake manifold. this ignites all the gas currently in the intake manifold and the pressure has to go somewhere - straight back out the path of least resistance, the intake. but gas does not 'build up' in the airbox. remember that petrol powered cars have the same problem when they run carbys . i dare say lpg is no more dangerous than petrol.

[FXST01]

I have seen cars with a hole drilled in their intake pipe (about 50 cent size) covered with an old neoprene stubbie holder. Just food for thought.

[BoNeZ-01]

it doesn't. what happens is that the gas in the cylinder doesn't ignite, and when the intake valve opens an explosion can occur in the intake manifold. this ignites all the gas currently in the intake manifold and the pressure has to go somewhere - straight back out the path of least resistance, the intake. but gas does not 'build up' in the airbox. remember that petrol powered cars have the same problem when they run carbys . i dare say lpg is no more dangerous than petrol.

Ahh.. OK, so it's not the fact that the airbox is 'filling up with gas then exploding', just 'backfiring' same as petrol can, meaning it's an ignition and/or timing issue?
Petrol EFI's 'can' backfire under certain conditions, but yeah, much more rare than carby engines.

[immortality]

Petrol EFI's 'can' backfire under certain conditions, but yeah, much more rare than carby engines.

sure can. my V6 had a huge backfire through the intake when i accidentally knocked the kill switch when cranking.

[wildss]

I have seen cars with a hole drilled in their intake pipe (about 50 cent size) covered with an old neoprene stubbie holder. Just food for thought.

ive seen the same but with holes about the size of 20c pieces all around the intake tube but just one section not the whole length of the tube, stubby holder over the top and problem solved.
very clever idea

[levymetal]

Ahh.. OK, so it's not the fact that the airbox is 'filling up with gas then exploding', just 'backfiring' same as petrol can, meaning it's an ignition and/or timing issue?
Petrol EFI's 'can' backfire under certain conditions, but yeah, much more rare than carby engines.

yeah, well if the gas is running lean that could be why it's backfiring as well. once you get it tuned it wouldn't hurt to check the timing to make sure it's set correctly. and that stubby holder idea posted above is genius

[Vt-Brrrlina]

the airboxes explode when the leads start to break down and spark travels back thru the system, the back pressure doesnt get stopped at the mixer and find the weakest pint (the airbox) and blows it apart.

[BoNeZ-01]

yeah, well if the gas is running lean that could be why it's backfiring as well. once you get it tuned it wouldn't hurt to check the timing to make sure it's set correctly. and that stubby holder idea posted above is genius

So I guess the problem there is trying to find the illusive sweet spot, that 'relative' happy medium between a 'good' tune for gas, and for petrol?
From what I've been told about dual fuels, the perfect tune for one, is not perfect for the other.
Or is it possible for later EFI's to have a different tune setting for both gas and petrol programmed into the ECU, which automatically adjusts?

[levymetal]

the ecu only controls the spark curve on gas, the mixtures are adjusted independently. that's what i mean by a tune - getting the mixtures for gas adjusted (this has no bearing on the 'tune' for petrol). the spark curve in the memcal isn't optimal for gas but having said that it still works perfectly fine. the happy medium is probably sticking with the petrol spark curve.

[BoNeZ-01]

Ohh ok, kewl, good info, thanx.

[wortus]

VN's don't have an air flow meter, they have a MAP sensor on the firewall. The intake duct won't be at vacuum, that happens on the manifild side of the throttle butterfly when the butterfly is shut or partially shut, vacuum drops off as you open it up. There may be a slight pressure drop after the air cleaner but not a vacuum.

[Paiste402]

ive got this on my falcon lol last owners put it there but i think its ingenious haha sits flush so it doesnt drag in air but its got a touch of slack for if it backfires

but i dont get backfires

[Vlad01]

haha thats funny. my little bros ford is exactly the same as that one there, color and all. except his box is shattered into many pieces from lpg. we are dumping the car this week for a ford of the same model that is actually able to become roadworthy.
Thats what happens when you get someone to get u a first car without knowing how to check anything :/

[nathanVY]

ive seen somewhere someone had dual memcals with different tunes hooked up to their ecu activated by a switch.

what are peoples thoughts on this? could it be done properly with optimal lpg and optimal petrol tunes?

[Gaz_3110]

I used roadie duct tape on mine, Sure enough air box still in place duct tap torn. There is so much love in this world for duct tape!

[strgas]

what system is installed on your car ? what spark plugs are you running and what gap ? Any vacum leaks from gaskets or seals can lean out the mixtures ? where was the system installed ?

[vn_wagon90]

Just a thought .. I have a NF fairlane and its on gas .. but because i change the plugs every 10.000 andi have proper leads on it .. It will only back fire if the motor is sucking air around the TB or any where in the inake system .. a blown intake gasket can cause it

I also have a friend who has a VN on gas and his only back fires if its sucking air between TB and air box ..

so maybe check all you intake piping and go from there .. also wise if you change your plugs every 10,000 and get MAX leads by top gun or something eqivalent
hope this helps