Been thinking about installing N20 but have heard of a few cars that have backfired and blew the lids/maf up.. What causes a n20 backfire? Is it more common on a dry or wet kit?

 

I'm pretty sure its caused by a wet kit being shot too early(under 3000) and fuel puddling in the intake manifold. Remember the LS1 was never ment to have fuel through the intake manifold anyway, though it is completely safe if you shoot at the right time.

 

i dontthink that is true. i asked a while back and they linked me to a couple page discussion. they said that was the common thought but was not true. i dont remember what the cause was cause it was so long i did not read it. but i think something about a leaky intake had something to do with it.

 

I honestly don't believe that the cause of backfires has ever been proved but would like to know if it has.

 

The 2 backfires I saw ripped out the back of the intake manifold in the same spot near the MAP sensor. Both were wet shots and both cars were dyno-tuned. I have no clue why it happens

 

https://ls1tech.com/forums/showthrea...trous+backfire
there is a diecent discussion. do a search nitrous backfire and you will get a lot of results. this is one of those things that has been brought up a 100 times. not bashing cause i brought it up also and still dont know for sure. if you find a post started by me in the n2o section about this i believe it has a prety good link in it.

 

i seen it happen when you accedently hit the rev limiter while spraying a wet shot. it will not happen with a dry since there is no fuel in the intake to ignite.

 

That's what I always thought, plus I've been told by others that this was a common cause of nitrous backfires.

 

Eh ?

The same thing will happen at the rev limiter with a dry shot - no fuel + nitrous = kaboom.

Dry shots won't pool fuel in the intake but they will still go kaboom if you spray nitrous with not enough fuel...

Bad30th

 

I'm no expert on this subject, but this is what I have gathered as well as some of my own theories.

It is my belief that all nitrous backfires are due to lean conditions or pre-detonation. This can happen at high RPMs or at low RPMs. A low RPM backfire is usually due to fuel puddling which is associated with wet kits.

My take on fuel puddling: For the spark to enter the intake where the fuel puddles, the intake valve would have to be open, but both valves are supposed to be closed during the power stroke. If there is a dieseling effect or a pre-detonation of the cylinder then the spark could enter the intake while the valve is open and cause a huge explosion. But this would suggest lack of fuel (that lean condition theory) or too much timing. It could also be caused by the valve overlap of the camshaft keeping those valves open longer along with the timing.

I don't know if the fuel puddle can cause the lean condition and the chain reaction to cause the backfire, or if it just happens to be there when a cylinder goes lean and exaggerates the backfire into a big explosion. I would guess that the fuel is directly related to the problem at these low RPM backfires because of the lack of velocity that somehow contributes to the situation. The question is why is velocity so important to the prevention of a backfire? And why is there a magic 3000rpm number that makes everything ok? Does the lack of velocity cause uneven fuel distribution to all the cylinders, making one leaner than the other causing the lean condition backfire? Or...is the initial hit of the fuel, starving the fuel rail and subsequently the injector and causing the backfire? I would think it could be one of those problems or a combination of both. I do know that fuel is 3 times heavier than N20, so it needs a high velocity to distribute evenly.

Backfires happen with dry kits as well, but adding fuel to the intake seems to exacerbate the problem. Someone please correct me if I'm wrong.

 

Thanks. I don't hear of it happening too often but wanted the info before I decide to install N20

 

It WILL NOT happen on a dry. On a dry you will just burn up your motor but it will not backfire till a piston comes out of it.

I will say this again. The LS1/6 intake was NEVER designed to flow fuel. If something happens to the N2O (low bottle, empty, bad noid) you going to be flowing gobs of extra fuel in a place where it does not belong.

 

I have taken out maybe 3 or 4 MAF's and 1 lid through nitrous back-fires. In fact I have a "dent" in the hood of the SS from one of the backfires. I have a wet system. All have come at high RPMs in 1st or 2nd gear. All were related to O2/exhaust problems causing the PCM to try to lean out the fuel. I "think" I have resolved the problems with my new exhaust system (I really don't have one ). No backfires since the O2/exhaust problems resolved (knock on wood).

David

 

Speaking of this, look what happened to a guy in my local club during his burnout last weekend at Carlsbad :

http://www.drugg.net/89lt1vsnitrousbackfire.wmv

Hit the limiter and fuel cut out - no window switch...

Blew out a ring, motor rebuild underway soon.

Bad30th