MAP & IAT vs. MAF

MAP Sensors

MAP is an acronym for Manifold Absolute Pressure.  The MAP sensor is a key component in a Speed Density fuel injection system, and measures pressure and absence of pressure (vacuum) at the intake manifold.  MAP sensors typically have 3 wires: a 5 volt reference signal wire, a ground wire, and the wire that goes back to the ECU for all that sweet, sweet air related data.  The ECU (a.k.a PCM, ECM) then calculates the air / fuel ratio based on VE tables within the computer. We will cover Volumetric Efficiency tables at a later date.  Just imagine a magical grid in the computer that says “if you see this voltage from the MAP, then do this…”.  The cool thing about these sensors is that they are simple, and can be easily used for higher performance applications.   The bad thing about these sensors is that they are part of the speed density fuel injection system that doesn’t know exact amounts of air going into the engine, it just makes educated guesses at it.   These guesses are all well and good, but solid numbers are always better.  Or are they?  Naturally, there is much more to a speed density fuel injection system than just a MAP sensor…..

IAT Sensors

IAT is an acronym for Intake Air Temperature.  The IAT sensor measures the air temperature that is going into your intake manifold.  The colder the air, the more dense it is, and the more fuel you need to keep your engine happy.  Coool ….literally.  Almost all IAT’s are simple two wire devices that measure resistance.  As the air temperature changes, the resistance in the sensor changes and the ECU knows to change the A/F ratio based on this.  Combine this data with that of the MAP sensor and your computer can now give a pretty accurate guess of the volume of air moving through your engine.  This is great news, but it’s all based on calculations, instead of real solid numbers.  This is where speed density is tossed aside and big Mr. MAF enters the party…..

MAF Sensors

MAF is an acronym for Mass Air Flow.  These sensors are pretty impressive because they measure air volume, along with temperature, all in one (no IAT necessary!).  Remember, the MAP sensor above measured intake manifold pressure / vacuum and then estimated air volume with computer software.  A MAF actually measures real air volume so that the computer doesn’t need to guess what it might be.  As you can imagine, MAF’s are typically more accurate ways of measuring the amount of air that goes into your engine.  This sounds great, right? Well…. it is, on a stock vehicle, and even lightly modified ones.  However, if you decide that you want to make way more horsepower than your car was ever intended for (where do I sign?), then MAF just isn’t going to cut it.  MAF’s quickly become bottlenecks in your air intake system because they can only measure “X” air at once.  If your engine needs more than “X” amount of air, then your MAF freaks out causing your engine to run lean and quickly turns rotating engine parts into liquid hot magma, (Hellooo magma).  This is where Speed Density is welcomed back into the party, and brings along a couple of lovely friends, known as MAP and IAT.

So as you can see, there are pros and cons to each, and it really depends on your vehicle and its modifications to choose who is the cooler sensor at the engine party.  Luckily, choosing one or the other only needs to happen when you modify your car to the extreme.  If you have a stock car, none of this really even matters.

For those of you that are attempting to make crazy horsepower,  what do you guys & gals prefer?

L92 Heads: Do you know how awesome they are?

Can you believe that brand new from GM this bare cylinder head was only slightly over $200? Over the weekend, I spent a fair amount of time staring at a 6.2L L92 engine out of a Cadillac Escalade, along with all of it’s wonderful aluminum parts.  It made me want to build one for myself really badly.  The weight savings, the easy power, the plentiful parts.  There is no downside to this?! At $200 per bare head, you could build a complete set of these awesome flowing, 70cc combustion chamber, aluminum cylinder heads for like $800 (maybe cheaper if you are savvy).  These L92 heads, when combined with the right intake manifold, will allow you to effortlessly make 500+ hp without any power adders.  Just bolt it together and enjoy your tire smoke. After years of dealing with cast iron SBC and BBC cylinder heads, blocks, and intake manifolds, I don’t think I can go back.  I feel obligated to grab new technology by the horns and do a dance with it.  Who’s with me on this?

Question: Do I really need 17 wheels for one truck?

While doing a little spring cleaning recently, I began to realize that I had amassed a massive quantity of extra wheels and tires for the 1989 Dodge truck I have. If you combine the number of tires (18), with the number of wheels (17), you can imagine just how much space this takes up. Now, I can look at this a few different ways. I could think positively, and say “Hey, I have 1 set of wheels for each season, plus a spare!” Conversely, I could be a downer, and say “I have 17 wheels, and only 7 will physically bolt on to my truck at this very moment.” Yes, they all have the same bolt pattern, but let’s just say that my truck is weird, and doesn’t willingly accept change.  The question then arises, if the truck can only handle 4 wheels and 4 tires at any given time, do I really need 3 extra complete sets?

TIG welding is an art, but Not everybody is an artist.

Last year I finally bought myself a TIG welder so that I could weld aluminum, stainless steel, roll cages, and overall, step up my welding game.  I figured since I had been MIG welding for 10+ years, TIG would be a piece of cake, but boy was I wrong.  TIG welding is an absolute art, but not everybody is an artist.  It takes a boat load of practice and dexterity to be good at it, which is why professionals make the big bucks.  As I mentioned in this blog that I wrote a few weeks ago, MIG welding can be done with 1 hand (blind folded, tango dancing, while on fire).  TIG on the other hand requires holding filler rod with the left hand, a torch in the right hand (at the correct angle), and it has a foot pedal to control the heat.  Once you get all three limbs to work in unison, metal begins to melt, and the learning curve really begins.

Faster than I could say “this is hard to do!“, I had burned through 2 tanks of argon, countless filler rods, several pieces of tungsten, and a few layers of skin.  As I quickly learned, aluminum retains heat really well, and doesn’t look hot even when it is.  Note to readers: WEAR GLOVES when TIG’n!

Here are a few “finished” pieces from my last practice session. Like I said, TIG welding is an art, and not everybody is an artist, yet.

Arizona Junkyards Are Better

Every car in Massachusetts is rusty. Whether you have a 1955 Lincoln Capri or a 2010 Chevy Camaro, in the North East, your car’s destiny is rust.  Now, if the nice cars are rusty, just imagine what the vehicles in our junkyards look like.  They are absolutely horrifying at best.  In the time that it takes to remove a junkyard fender, it often erodes itself back into dirt right before your eyes.  Bolts? HA!  After 1 year (so… 2009 models at this point), all bolts become permanent.  At the 2 year mark, the bolts don’t even look like bolts anymore. They become round rusty buttons that can only be removed by breaking the head off with Vise-Grips.  It is truly an awful experience.  Thank goodness for torches, Sawzalls, sharp drill bits, and tetanus shots.

Arizona cars on the other hand, are better in every possible way.  Rusty cars (New England style) just don’t exist out there.  What they consider a junkyard car is usually “flawless” in my opinion.  The nicest cars I personally own aren’t as clean as what is found in their junkyards.  It’s quite sad really.  Over the last few years, I have had the pleasure of working on several classic cars from the South West, and I laugh like the village idiot the entire time I work on them because I can’t believe that the bolts come out.  Underneath the AZ cars, the original hydraulic brake lines and parking brakes cables are often still there and working.  It is a gearhead fairytale.

Let’s do a comparison, to see who the real winner is.  Massachusetts on the left, and Arizona on the right. Ding Ding Ding. FIGHT!

Sure enough, Arizona wins with a KO, as expected.  If you want to restore an old car, just buy a rust free body from someplace dry. It will save you thousands of dollars, trillions of hours, and a Tetanus shot.

On Ebay: 12 Old Jaguars Covered in Dust.

Like any car enthusiast, I often find myself scouring eBay Motors for cars and trucks that I can’t have.  While doing so, I stumbled onto a fleet of Jaguars that looked noteworthy.  Apparently they were collected between 15-25 years ago, and haven’t really been touched since.  The thing that I find most impressive is that a bunch of them are “racked” up high in a warehouse of some sort. You need to be a truly dedicated & motivated gearhead for those kinds of shenanigans.  I mean how cool would it be to be able to look up at  project cars while you work on others?  Anyway, the starting bid is $200,000, so get out your wallets.

Here is what the auction includes along with misc parts:

1961 XKE 6-Cylinder Coupe 2-Seat (Orange)

1964 XKE 6-Cylinder Coupe 2-Seat (Black)

1966 XKE 6-Cylinder 2-Door Coupe (Black)

1967 XKE 6-Cylinder 2-Door Coupe (Maroon)

1968 XKE 6-Cylinder Coupe 2+2 (Blue)

1969 XKE 6-Cylinder Convertible (Red)

1969 XKE 6-Cylinder Coupe 2+2 (British Green)

1970 XKE 6-Cylinder Coupe 2+2 (Silver)

1970 XKE 6-Cylinder Convertible (Red)

1971 XKE V12 Coupe 2+2

1974 XKE V12 Convertible (Red)

1974 XKE V12 Convertible (Blue)

And here is the eBay Listing

Electrical Gremlins 101.

Recently I acquired an automotive engine wiring harness that needed some serious love and attention.  The previous owner had apparently stirred the dirty pot of electric gremlins, allowing them to surface from the deepest, darkest bowels of the vehicle.  After seeing it with my own eyes, it became my obligation to write a “how-to” on how to successfully breed automotive electrical gremlins.  The previous owner of this wiring harness had perfected this lost art, and I didn’t want the information to become lost again for all eternity.

Step 1) Use Scotch Locks to splice a few extra inches of wire in.  That’s not what they are intended for but hey if it works, it works.

Step 2) Now solder some frayed wires together with zero flux or penetration.  If possible, just “plop” a dab of solder on the 2 wires, but not too much, this isn’t not meant to hold for more than a few days.

Step 3) Cut open a few important wires, run them through a blender, then leave them open to the elements.  This will allow for sparks, fire, and other forms of excitement.

Step 4) Add T-Taps, lots of them.  The goal here is to damage as many wires as possible, and this will get you well on your way.  Remember that moderation is not a word in your vocabulary.

Step 5) Find a connector that goes to something important, like a Mass Airflow Sensor for example, and cut it off.  Now, ever-so-gently twist the wires back together.  As soon as that is complete, pull them apart again, and lightly twist them back together in the opposite direction.  Don’t bother shrink wrapping them or taping them, it won’t be necessary.

Step 6) Your car won’t run soon anyway, so why not start early by ripping off the fuel injector connectors.  One? Nah, go for 2 or 3, at least.

Step 7) This is the final step so pay very close attention.  Find a ground loop connector, preferably with multiple wires going to it.  Now grab the nearest pair of wire cutters, and cut the entire thing off.  Quickly put the loop in your pocket, and do whatever you need to do to make sure it is never associated with the wiring harness again.

If you want to successfully breed electrical gremlins in your own (or maybe a friend’s car), these are the steps you need to take to complete the process.  Completing every step won’t be necessary because just one of these steps will cause endless hours of enjoyable electrical gremlin chasing.