This is just my opinion and something to think about.

Puddel-ing myth or fact.

What is puddle-ing?
Can it cause a backfire in my intake?
Why is this term used so often?

pud·dle P Pronunciation Key (p d l)
1.
a. A small pool of water, especially rainwater.
b. A small pool of a liquid
Puddleing is a term used to described fuel collecting in an intake on the walls or in the floor of an intake.
Puddle-ing cannot make a car back fire. The fuel will not self ignite in this arena. And fuel cannot puddle in an intake.
The term is over used to describe a backfire. People will say “It is always the nitrous’ fault” when there is backfire while using nitrous. “It puddle” This thought process is simply because it is so violent when it does happen.
I have read the posts over the last few years about fuel collecting in an intake. OK
And the lean backfires. Ok

Question is “what lit the fuel in the runner”. What cause the flame to come into the intake side of things and light the fuel nitrous mixture in an intake? I believe it has to do the velocity. Airflow coming into cylinder must be decreased some how for the flame to be allowed into the intake track. This is why all nitrous companies tell you not to spray an engine below 3000 RPM’s. The nitrous injecting into your engine has a higher velocity then the actual engine cfm flow at that rpm. Air stalls or slows down just enough for the flame in the combustion chamber to come back up into your intake port and then you have a backfire. .
Also you will only be able to put X amount of nitrous and fuel into and engine. Being that it is an air pump the pump can only move so many cfm’s and a nitrous system can not pressurize the intake track. (non-boosted applications)

Damp areas are not going to light themselves; if there were any damp areas in an intake. Areas that are wet after an intake has been ran on car are from vapors that are hanging around once the car is turned off.

Air hushing into a cylinder helps push the unburned and burning media into the exhaust. If you ever started a car without a header or exhaust manifolds on; you have seen the flames. So as long as velocity is kept up no problems, this is a per cylinder way of looking at it.
Air travels though a 347cubic inch engine at __156__ mph at 6500 RPM with a 75mm throttle body. Now lets say from the backside of your throttle body to the exhaust port is 3 ft. It only takes air .0131 of a second to go from the throttle body to the exhaust port. So in no way can the fuel puddle in an intake. There is not enough time.

Note that these calculations make some assumptions like non-turbo, and airflow is equal to displacement, etc.

This is just my 2 cents.
Ricky

 

Good info.......thanks.

 

Well if your spraying too much fuel into the intake it can puddle--and that's usually what is happening to people that have puddling problems. They are spraying some pretty big shots---(big for being just a single nozzle in the intake) When in actuallity they need to be going direct set-up.

But like you said So it's not the companies fault it's the user.

"Operator Error"

 

Like the original poster mentioned, the fuel isnt going to puddle above 3k rpm.

And it's not the size of the shot - I sprayed a 2 stage 300 (150/150) wet shot through the throttle body for 5 years.

 

As mentioned in my post i said single nozzle. You are spraying through two Not to mention the blower your using to push it in. I am re-furring to people who max out the nozzles.

 

Blower is more recent. I was talking about my pre-blower experience.

Spaying through 2 nozzles would be pushing a higher volume of fuel, than overworking a single nozzle. Seems like if the puddling situation actually occurred (which I don't believe), my senario would be much worse...

 

What kind of parts were you using for the 300 shot? How much retard and fuel octane? What kind of ET's did you run? I am currently running a 175shot and have the pills to run 200 on my 355" Lt1. I ordered my second nozzle to run a similar setup to yours like 100HP on one stage and 200HP on the other nozzle. My bottomened is forged 4340crank, H-beams and Lunati pistons so they should be able to handle it. You can Pm me with the info if you don't want everybody to know. LMK Later Clint

 

Nozzle maxed out has more to do with the nitrous side then the fuel.
Ricky

 

Wouldn't retarding the timming be the bigger factor on the backfiring issue than puddling?

I would think that the nitrous making the burn so much faster, that it would burn before the intake valve could close, which would make the back fire and blow the intake off the car.

My thinking anyway.

D Moss

 

puddling is much more common on cars with wet intakes also, thats why you see lots of juiced 5.0's blow their hood off

 

Blowing there hoods off has nothing to do with puddleing which does not happen anyway.
Ricky

 

Forgive my lack of knowledge here, but I am confused how there could even BE a flame while the intake valve is open... My understanding of basic valve timing is that when the intake valve is open, the piston is traveling down the bore to draw in the intake charge. At or near the bottom of the stroke (either at BDC or just after), the intake valve closes and the mixture is compressed. At TDC or very near the plug fires, igniting the mixture.

My question is how can you COMPRESS the mixture if the valve is still open?

Doesn't make sense that you could blame it on preignition because that typically happens during compression, right? So how can there even be a flame to travel back into the intake at all?

I'm really NOT meaning to sound condescending here if it appears that way. I'm trying to learn some about nitrous, as I plan to install a nitrous kit on my car in the future...

 

Keep in mind that during overlap BOTH valves are open at the same time. If any combustion is still taking place, it can ignite fuel in the intake. This is typically due to improper timing or mixture that prevents complete combustion before the intake is actually open.

Typically there is sufficient intake mixture velocity to maintain movement into the chamber. Think of igniting the spray leaving a spray can.... the flame stays away from the nozzle due to the velocity. Keep in mind that when you inject nitrous to the intake the cooling effect causes condensation of the existing air mixture in the intake. If this occurs in the plenum some of the mixture can be drawn towards the cold nitrous as the surrounding air shrinks in size. This can reverse the direction of flow & draw the contents of the chamber into the intake. At low speeds with a big cam, there is already reversion into the intake during overlap. Suddenly you have air, fuel and nitrous in the inake & the reversion just gave you a flame source.

 

Thanks for clearing that up for me. Now I see how it can happen.