I just ordered a Volant CAI and Ram Air duct. I'm just curious as to what happens when an engine runs lean? Complete failure? smoke? and what are the symtoms of running lean as far as noise, hesitation. Maybe Mike can help with this.


Thanks

 

Well, first off, the *only* way you will know that you are actually running lean is to have the A/F's tested. But what happens when you run in a lean condition for long enough is that you burn up teh engien, causing total failure - or partial failure, it jsut al depnds on how lean, for how long, etc., etc. You can have anythighn from a trached motor to a burnt piston or tow, or jsut a couple of burned valves.

Basically, on the 3-valve motors, any intake kit that adds significant power is doing so by reducing restriction, of course, and that alters the MAF transfer function, leaning out the motor.

Now you can run a certain amount lean and not hurt anything - then you hit a certain range where it will cause engine damage, and then even leaner, you aren't producing enough heat to hurt anything. It's really too detailed to get into here in tersm of goign over all teh exact A/F ranges that will and will not cuase damge on both normally aspirated and forced induciotn motors, but the bottom line is, we urge everyone with tuning on these 2004 & newer F-150's especially to get to a dyno and do the datalogging as per our docs (for those who purchased their tuning from us), and send us that data so we can analyze it - that is included in the cost of us doing our custom tuning.

Last - *NEVER* use any true "ram air" setup - anything that actually causes positive air pressure in the air intake tract will lean out the motor dangerously, and it will also make the engine run leaner and leaner the higher the speed the vehicle is driven at! If it's just a hood with a couple of open air scoops to let air into the engine compartment, that is OK - but a *true* ram air setup is not OK - most likely what you have is a simple sealed system with an outside scoop with that Volant, and that should be OK - but you always need to test the A/F's to know - anything else is just guessing.

 

Just curious but how would it lean the car out if the air is still going through the MAF before it gets to the motor? You are not putting unmetered air into the motor so "if" this would happen it would be the MAF's fault not the ram airs fault.

 

Hi.

Simple physics. It's called a transfer function for a reason - it's a predefined table, and it's based upon the design of the intake system (among other things). If the MAF counts ( or voltage) does not reflect the actual airflow (or Load, which is basically the amount of incoming air, ratioed against how much 1 cylinder can hold at standard pressure/density), it's fubar time.

Upset any of the expected references, be it abnormally high intake pressures, or tube design, or any 'shadetree' mods, and you can expect problems.

Here's an example, that discusses the consequences of DWV and/or silencer removal mods on '04's and up... posts 5 & 7 ...

https://www.f150online.com/forums/sh...452&highlight=

And it sure doesn't help that some of the dang things run too lean stock from the factory

Hopefully the experts will chime in to elaborate/correct my simplistic response

Cheers
Grog

 

I understand what you are saying, but unless the ram air system was the only means of feeding air to the car then it still would not matter. If the ram air system fed air into the filterbox, which is what most modern ram airs do then there shouldn't be a problem as the air will still be at normal atmospheric pressure because there is another way out of the intake box for the extra air. Now if the ram air fed into a sealed filter housing with the only way for air to get out would be through the motor then yes you would have a problem as that is now I guess what you could call small supercharging in a way.

Example, the Mustang Mach 1 comes with a shaker scoop that is what you would call ram air, the air goes through the scoop into the filter box then to the motor. It is however not the only source of air for the car in that there is still the standard opening inside the fenderwell to suck in air. Any air that the shaker takes in is not "Forced" into the motor. It is forced into the airbox and the motor takes what it needs, and what it dosen't need probably flows out of the other opening. The only real advantage to having this "Ram Air" is it will take in a colder air charge.

So if you look at it that way every car has an adaptive maf to an extent. Lets say I am riding around in 90 deg weather. The maf will still register any air that goes through it right. Now what if I am riding around in 30 deg weather? In colder weather the air charge has more density but the Maf still picks it up. That is probably more of a difference than any bolt on ram air would be.