I witnessed one yesterday and it didnt make sense, the car was lean 15.1 he upped the fuel jet and next pass as soon as the N20 hit it blew up, scared the **** out of everyone. Any thoughts.


Marco

 

Fuel puddling in the intake....

 

which is caused by.......

 

Give me more info.
wet or dry kit
What RPM did he start to spray.
Did he hit rev limiter.
that car was running dangerly lean.
Dave

 

its caused by a wet kit only. when fuel gets antomized with nitrous oxide sometimes the fuel falls out of the mixture. this happens because fuel is more dense then air mixed together.think of fuel holding onto air but falling out of place because its to heavy to move.

hopefully you understand this much. sometimes when to much fuel falls out it stays in the intake runners.this is called puddling, when to much finally is in there the fuel in the intake will ignite.... and well thats all she friggen wrote. if you have backfire ports in the intake normally this will prevent engine damage. LSX and NX make intakes for this purpose, so does hollys intake as well.

this is why most people run dry or dp kits. all kits can be made safe and with the proper tuning can last longer then engine life, but its known that dry leans out while wet "puddles" which is why dp kits are the best. you can adjust each cylinder this way so can run say 40 per cylinder. total that would be a 320 shot, not good on stock interals but you get the point. wet isn't exact neither is dry.... and neither is dp unless tuned properly.

but anyways i think i went beyond the call of duty, hope that answers your question. IMHO i wouldn't have switched a jet based on a 15:1 a/f mixture. maybe look at fuel pressure and play for fuel tuning first. answer nitro dave can probably tell you exactly what happened just give him full details and i sure he has heard it or done it himself.

thanks for reading,

erik

 

The main problem would be the lean condition. You can puddle all the fuel in the world and it won't do anything unless it has time to turn to vapor/gas during ignition.
But if his car was that lean he was most likely causing preignition and ignited the mixture at the wrong time and you get the rest! Just a guess.

Jeffrey

 

He was running lean and he put larger jets in? That doesn't sound too smart

 

Larger fuel jet to richen it up and lower the A/F ratio.

 

I concur. remember think safety first.

 

this was on a 2004 Mach 1, NX Express kit wet, 75 shot, he had the jets that NX recommended, the car was lean as hell, nitrous was being turned on at 3,000rpms, we know that 15.1 is lean we never made a full pull, figured the car needed more fuel so he upped the fuel jet, BOOM!!! everything goes flying. the motor blew at like 3400rpms it was almost instant


Marco

 

Standard automatic, what gear was it in? How hot was the car? What was the bottle pressure 2nd pull.
Back fires are caused by lugging the motor, not fuel puddling.

 

5 speed
4th gear
dont know how hot the car was but i would say normal temp
950psi i think i know he had the heater on

 

sounds kind of like a waste of new 4v mod motor...... play with fire and you get burned. i would like to hear his reasoning to the dealership when they ask how this happened.

 

4th gear could have been the problem, might have lugged but then agian you said it was above 3000 rpm. Was the bottle pressure really 950? this is a retunless fuel system right? Was the 15:1 just a lean spike. The fuel noid migh have sucked it lean at first with the regulator being in the tank. Also some intaks just really do not like n20 and fuel going through them. I know of a lot of 4.3l s-10's that set the pper plenum right off in a million pieces. Mine never did though in two years of sprayin at a 11.5:1-12:1 air fuel ratio. That was also with a walbro 255. More info on the setup migh help to find the reason.

 

did you say the engine blew up or the intake? two very different things.

 

This sounds like a lean back fire to me.What was the airfuel on motor.Thatt will tell me what I need to know.
Dave

 

no idea, all i saw was the lean a/f during the N2o pulls. he ran it on the street the weekend before like that


blew the motor and the whole air intake system


marco

 

Here is the deal.The car may have been lean on motor.If it was that lean on motor it is going to be that lean on nitrous.Im going to put my money on this being not enough fuel.It may have been the tune up,or a week fuel pump or even the fuel solenoid not wired up correctly.But with out all the info its just guesses which amounts to nothing.
The 4.6 mustangs have week pistons and to little of injectors from the factory.All of them run on the lean side.That is why I always suggest a timing adjuster for anything over a 100 shot.iThe real fix is that it needs more fuel.
Tell you freind when he gets ready to try this again to give me a call.Ill help him do this safely with years of knowlede.Best of all my advice is free.
Dave

 

Thanks Dave, I'll let him know


Marco

 

That post was total bullshit. The backfire was caused by the VERY lean mixture and resulting plug damage and preignition....fuel puddling is a total myth at these power levels.....