CAI indepth.....

hampsterzone · #1 Sat, January 29th, 2011, 10:31 PM

I have heard many arguments on CAI. Gotts mod, CAI, ect. Well, a very good friend who is a mechanic of 25 yrs, gave me the low down. CAI's are the best for adding horsepower. The Gotts mod is cheap and effective but not as much as CAI. Moving the MAF sensor doesn't cause lean codes. It reads air flow no matter where it is. Lean codes come from custom exausts not CAI. Low back pressure cause the lean codes. Which makes sense cause I never had a lean code with my edge and CAI alone. But when I did headers and true dual exhaust I saw lean codes on bank #1 and bank #2. We did find that the Gotts mod is the cheapest, easiest mod you can do. But again, it is in my opinion that it depends on what you want and how much you are willing to spend. Hope this helps. Oh and by the way, removing cats could be the worst thing you could do as far as causing our engines to run lean. I am not an expert but my friend has worked on many F150's and says they are great trucks to modify if you take your time and do it right. Thanks guys.

DarkShadowSTX · #2 Sun, January 30th, 2011, 08:55 AM

Quote:

Originally Posted by hampsterzone

Moving the MAF sensor doesn't cause lean codes.

I have always read that the reason you get lean codes is because you move the MAF.

Low back pressure cause the lean codes. Which makes sense cause I never had a lean code with my edge and CAI alone.

Backpressure is supposedly just a myth. I never had a lean code with my EDGE and CAI but I did get other codes because the truck wouldn't run correctly since the CAI changed the MAF location. Custom tunes on my Gryphon fixed that. A lot of people with EDGEs and 5.4Ls got lean codes with CAIs though.

hampsterzone · #3 Sun, January 30th, 2011, 12:58 PM

Yeah, it seems to be a complex system that varies upon application and truck setup. Idk, but I can say that if you are going to do mods you better be prepared to do them right. Thanks, I appreciate everyone's opinion. As far as the MAF and exhaust causing lean codes.

Probably both! I do believe my mechanic on the exhaust though. Not sure if I believe MAF being the reason. More like more air from the CAI. I am sure we will figure it out soon enough.

***Longshot270*** · #4 Sun, January 30th, 2011, 04:05 PM

Quote:

Originally Posted by hampsterzone

I have heard many arguments on CAI. Gotts mod, CAI, ect. Well, a very good friend who is a mechanic of 25 yrs, gave me the low down. CAI's are the best for adding horsepower. The Gotts mod is cheap and effective but not as much as CAI. Moving the MAF sensor doesn't cause lean codes. It reads air flow no matter where it is.

If your wanting to add power, a blower is the best. A CAI can't compete with boost.

The CAI's are slightly more effective at increasing power because of the slight lean condition they cause. I've seen 30 horsepower on a dynoed mustang just by going from slightly rich to a leaner A/F ratio. The ratio was then tuned back to stoic out of conscern for the motor.

Those horsepower numbers that the companies advertise also is not across the entire power band. That is the peak horsepower marks. Below about 2200 rpm you could have an intake the size of a trash can but the engine will not be bringing in any more air than it was before.

The commercial "cold" air intakes use a larger diameter pipe than the stock sensor housing.
This is a picture that demonstrates what a cross section would look like. The blue area is what the truck calculates for and the red area is what is not calculated because of an aftermarket intake that is larger than the stock housing.

The MAF sensor in these newer trucks is a heated wire. As the engine pulls in air the wire is cooled by the "breeze". The resulting temperature of the wire increases or decreses its resistance to electrical current which is read by the computer. With the larger diameter, the air will flow at a different speed. If you were to bring in 60 grams/sec of air it will flow faster in the narrower tube. Higher air speed, lower wire temperature.
On a stock truck the sensor is calibrated for the stock fluid area (blue). Any result you get from the MAF sensor can be calculated into an accurate physical volume. If you increase the diameter, you change the air speed, you change the reading and in doing so, you change how much air an electrical value represents. This is where custom tunes come in and we've got plenty of threads about that. :thumbup:

So the sparknote version:
Yes, the MAF sensor will read airflow no matter where on the intake track it is located, but that does not mean the reading will be accurate.
When you increase the diameter of the pipe the air does not need to move as fast to move the same volume. The slower air velocity will read on the sensor as the wire being slightly warmer, making the resistance slightly different. When the value is different the truck fuels different.

The gotts mod does not have this issue because it does not impact the MAF sensor in any way. All the gotts mod does is allow more of the shielded fender air than the stock system.

hampsterzone · #5 Sun, January 30th, 2011, 05:50 PM

Excellently put! I appreciate your response. Any thoughts on exhaust causing the O2 sensors to relay lean conditions?

ticopowell · #6 Sun, January 30th, 2011, 06:09 PM

My question about the CAI's and the MAF is that on the 2 K&N CAI's that I have installed, the MAF sticks around, and so did the pipe surrounding it. here is a picture here is another
the pics are for different sensors which may or may not be different than what we have, but my point is the same. That specific diameter where the MAF is located stayed the same in my trucks where I put in a CAI versus stock because that piece, even though it moved up or down the intake track, was exactly the same diameter.
The only thoughts that I have that would make it different is that if the pipe or filter right in front of the MAF made air flow faster through the pipe where the sensor cant read, such as the other side of the tube, then there would be a lean condition.
any thoughts?

hampsterzone · #7 Sun, January 30th, 2011, 06:27 PM

I have to say I believe it is the amount of air going past that causes the lean condition. Makes sense because a lean condition is caused by too much air to fuel ratio. Just like exhausts being opened up and less restrictive causes lean conditions. I can't seem to agree anything other than the more air means leaner conditions regardless of MAF location. Simply put, more in & more out means the computer has to account for than it is initially set up for. Fuel seems to be the missing ingredient. Or Bill for that matter. LOL I seriously can't wait to install my gryphon and see the difference. Hope my thoughts help.

***Longshot270*** · #8 Sun, January 30th, 2011, 08:27 PM

Quote:

Originally Posted by ticopowell

My question about the CAI's and the MAF is that on the 2 K&N CAI's that I have installed, the MAF sticks around, and so did the pipe surrounding it. here is a picture here is another
the pics are for different sensors which may or may not be different than what we have, but my point is the same. That specific diameter where the MAF is located stayed the same in my trucks where I put in a CAI versus stock because that piece, even though it moved up or down the intake track, was exactly the same diameter.
The only thoughts that I have that would make it different is that if the pipe or filter right in front of the MAF made air flow faster through the pipe where the sensor cant read, such as the other side of the tube, then there would be a lean condition.
any thoughts?

Tico, I'm not sure what to say with the After Market MAF sensors. That would be a question for Bill.

I can say that having the higher flow gotts mod and AM filters that the stock MAF can easily account for it. The stock sensor can handle over 200 grams/sec of air...or the amount of air my truck consumes at WOT around 5400 rpm. No basic intake mod can overwhelm the stock sensor. On my truck I got gains of about 10 grams/sec. Things might be a bit different for turbo/supercharge kits but for a basic stuff you're good on that sensor.
Here is a chart I made a while back comparing the gotts mod to the stock intake set up. http://forum.gopowerhungry.com/membe...maf-vs-rpm.jpg

That also brings up another factor for a lean condition because over oiling can cause it to acumulate on the sensor. This would help insulate the wire. Just one of the many reasons you should properly oil AM filters if you dont still use the traditional paper ones.

Hey...that looks like 2k posts, thanks for reminding me Ticopowell

hampsterzone · #9 Sun, January 30th, 2011, 10:15 PM

Any thoughts regarding exhaust causing leaner conditions? I would love to hear your opinion. (anyone's for that matter).

***Longshot270*** · #10 Sun, January 30th, 2011, 10:27 PM

I dont really have an opinion on exhaust because I've never really messed with it besides dropping empty cans into a friend of mine's diesel stacks.

I did find that a flowmaster 40 would only add .1-.07 seconds to my 1/4 mile time (even that is questionable when I compared the 60' and 1/8 mile times). So all those heated arguments over theories and physics and them being restrictive are pretty much a load of bull IMO.

Bill does advise custom tunes for certain headers, high flow cats and other mods.

In regards to a lean condition, if it is done right you shouldn't have any trouble...that is my opinion, so me and your mechanic agree on that part.