1.8t Acronyms
AIT – Sensor – This is a small sensor located in the intake manifold just after the throttle body. It is responsible for monitoring the intake temperature. It can get coated with oil, and can affect gas mileage, and a loss of power. It is common to remove it and clean it with alcohol, or electronics cleaner.
Boost Leak – View Block 032 with VAG Com. If Fuel Trims are Negative more than 5% in the load range there is a very good chance that there is a leak after the turbo. Visual inspection of clamps, hoses for a loose connection is the best way to look for leaks. A common place for leaks is at the entrance to the pancake pipe located in the passenger side fender. Also the small line on the DV can rip.
Fuel Trim Details Here -
http://www.ross-tech.com/vag-c....html
CAI - Cold air intake
CTS – Coolant Temp Sensor – This part is prone to failure. 2002 and older vehicles had a bad coolant temp sensor from the factory that VW updated. It was a black sensor, and now the good one is referred to as a green top coolant temp sensor. Block 011 in the VAG COM can monitor coolant temp for erratic readings. This is a 7$ part. Do not change while engine is hot.
Diode - What does the Diode Mod do?
The MAP (manifold absolute pressure) sensor is what reads how much actual boost you are making It sends that signal to the ECU (engine control unit). Once the data that the MAP has collected has been sent to the ECU, it then compares it to the specified boost that the car is supposed to be making (this is one parameter a chip modifies among many others). If the ACTUAL boost is over the SPECIFIED boost then the ECU puts the car into LIMP MODE. This is an attempt to stop you from damaging the turbo or anything else.
The DIODE(s) is connected to the correct wire(s) in the MAP sensor wiring harness. The MAP sensor sends signal to the ECU is voltage increments (so for 10PSI there is a corresponding voltage that is sent to the ECU when the MAP is reading 10 PSI).
The MAP sends 4.7 volts to the ECU when it’s reading 17 PSI and 4.3 volts when it’s reading 11 PSI. Once the diode(s) (whichever size you chose) is connected to the correct wire(s), the MAP sensor continues to read the actual boost that the turbo is producing and sends the voltage signals to the ECU corresponding to the amount of boost its reading, UP UNTIL THE VOLTAGE THAT THE DIODE IS INTENDED FOR. (For example...if you have the 4.7v diode in the MAP will send the voltage signal to the ECU up until its sending 4.7v...once it hits 4.7 volts it will keep sending 4.7 volts instead of sending the ACTUAL voltage for the ACTUAL amount of boost the sensor is reading which would be greater then 4.7 voltages, which would ordinarily without a diode installed, send the ECU into limp mode).
Therefore, it "tricks" the ECU into thinking it is only making 17PSI (because that is what the 4.7 volt diode clamps the MAP sensor at) instead of seeing what the turbo is actually making. Since the ECU is receiving signal from the MAP sensor showing that the turbo is only making 17 PSI (with the 4.7v diode in), which is what the specified boost is for a chipped ECU, THEN THE ECU WILL NOT PUT THE CAR INTO LIMP MODE - AKA, you can run as much boost as you want without hitting limp mode!
-courteousy Spooled_AWP
Quick run down:
4.3v diode will clamp at 11psi
4.7v diode will clamp at 17psi
5.1v diode will clamp at nothing as its over 5v
Diode is said not to work on the 20ths
DV - Diverter Valve
ECU – The ECU is responsible for nearly all functions on the car. If the ECU is suspected as a bad part, you need to use a scan tool such as a VAG com to attempt to communicate with the ECU. If you can’t communicate with the ECU, then the ECU needs replacement. Check all electrical connections. Check your Fuses for blown fuses. Whatever killed the ECU might kill the new one.
ECU removal procedure -
http://www.goapr.com/VW/suppor...a.pdf
IC - Intercooler
Immobilizer – These cars are equipped with immobilizers to prevent theft. If you swap an ECU without matching up the ECU and the cluster, it will start briefly and then die repeatedly. There are 2 kinds of immobilizer. Immo II used on pre 2002, and Immo III used on 2002+. Immobilizer and ECU info can be found on the VAG COM Site.
http://www.ross-tech.com/vag-c....html
http://www.ross-tech.com/vag-c....html
If swapping an engine into a car without an immobilizer/cluster, you can get software for swaps from REVO, and Dahlback that remove the immobilizer.
Ignition Coils – These are famous parts for the 1.8T they are very prone to failure. VW has had a recall on these because they were failing rapidly on 2001+ cars. To check for bad coils the best way is with a VAG COM. Log Blocks 015, and 016. This will be a misfire counter. Drive the car or let it run, and look for misfires. If you have a bad coil you will see the counter increase on a cylinder. If you have one counting up then it’s probably a bad coil. Turn off engine and take that coil out and swap it with another coil. The cylinders read left to right 1,2,3,4 when looking at the engine from the front. Use the VAG again to see if the misfires have also swapped to another cylinder. If it moved, then you have a bad coil. Replace it. If they do not move, then you likely have a plug
problem. On some cars the ignition coils have problems and they will pop up out of the cylinder head and lose contact with the plug. Plugs should be torqued to 22 ft-lbs when changed.
Two Coil Versions:
3pin (Found on AEB motors, and others of that era) - require external ignitor
4pin (Found on all recent motors 2000+) - ignitor is built into the coil itself
Limp Mode – These cars are designed to protect themselves from engine damage. If the engine boosts too much, or the engine does not get enough fuel it will go into a limp mode where boost is limited to protect the engine. It limits boost by controlling a solenoid on the wastegate line (N75), by closing the electronic throttle or by opening the DV valve. If you are experiencing a limp mode the best thing to do is get the car scanned for codes and to see what is wrong. Look at fuel trims for signs of running lean, and to look for MAF problems, or O2 sensor problems. To look for potential boost problems log Block 115 and you can see the specified Vs actual boost. If you exceed the specified then there is a good chance that you will go into this limp mode. Stock specified is a max of 14 psi for a 2002+ car.
MAP - The MAP sensor is located in the OE SMIC end tank. There are two different sized MAP sensors, and VW didnt make the transition based on years but cars from all years might have either the small or large version (rumor has it the small version didnt come around till ~2003). When your upgrading your intercooler to a larger SMIC or FMIC and need to specify which MAP sensor your car is running the only fool proof way to check which sensor your car has. If you are making custom piping and need a MAP sensor flange check out 42nd Draft Design for a universal solution.
Rule of Thumb appears to be:
2002 and earlier cars = large MAP
2003 and later cars = small or large MAP
MAF - Mass air flow meter is used to measure the air going into the engine. It is located on the outlet of the airbox, and housed in a cylindrical tube. The ECU reads the MAF signal, and injects fuel in proportion to the airflow. There are a few different ways the MAF can fail. The MAF can get coated with oil, and will not read properly. This is common if it happens right after installing a CAI, or a K&N filter. It can be cleaned out with 99% isopropyl alcohol, or a quality electronics cleaner. Remove the sensor from the housing and clean the sensor element.
MAF sensors also go bad due to too much airflow. On a car with a larger turbo the airflow is so high that the MAF element will get burned out from the excess air flow. It is common to increase the size of the housing to prevent this (other modifications required).
To check for a BAD MAF the best way is with a VAG com. Block 002 show air mass from the sensor. At idle the air flow should be 2-4 grams/second. With a wide open throttle run to redline the reading should show up to 170 g/s on a chipped car. Look for jumpy readings in the MAF, which can indicate a
problem. More details here
http://www.ross-tech.com/vag-c....html if you suspect your MAF is bad, one way to test it is to unplug the MAF, often if the MAF is giving false readings and upsets the fueling. If you unplug it, the ECU will ignore the MAF and run off of baseline tables. Be careful, as a boost leak or a vacuum leak can be miss-diagnosed as a bad MAF, because they will throw off the readings on the MAF. (Air sneaks around the MAF).
Quote, originally posted by WhiteG60 »
Basiicly the
problem with MAF's is that VW and some/all of the OEMs run the PCV back into thei ntake tract or you're running a K&N filter or another cotten/guaze/oil filter and a film builds up on the maf element because of the oil from the PCV or from the filter. If you run a catch can, and run a paper or foam filter, and make sure the intake tract is dry you will most likely have a very very reliable maf. Most maf failures are not even failures. Its the element being dirty/oily. If people would clean them with alcohol or the CRC MAF cleaner at the FIRST SIGN of it being dirty, or hell, even if you just do it every time you change your oil or during your maintenance regement, you'd be hard pressed to ever have to replace it.
MBC – Manual Boost Controller. Often people want more boost from their car, and use a MBC. While MBC’s can get you more boost they will cause a jerky part throttle driving, and can cause over boost, often put the car into a limp mode. The way a MBC works is by bleeding off air from the wastegate control line. A wastegate is a mechanical flapper valve in the turbocharger that opens to allow exhaust gas to sneak around the turbo. By bleeding off air from the line, the wastegate opens less, more exhaust goes through the turbo, and you get more boost.
Great details on MBC here -
http://www.boostvalve.com/tech/1.8T-DBW.html
And general Turbo/Wastegate details here
http://www.streetracersonline....e.php
N75 – The N75 is an electronic solenoid valve that the ECU uses to control boost. It is located in the intake hose near the back right side of the engine. It has 3 connections.
1. Connects to charge pipe = pressure source
2. Connects to wastegate actuator
3. Connects to intake hose – bleed line.
The ecu will pulse this valve at a high frequency to bleed air off from the wastegate line. It does this based on throttle position and engine load. If the valve, or any of the liens connected to it have leaks then there can be severe boost regulation problems. It’s function is similar to the MBC above. To get more boost people often swap in different N75 valves. These different valves simply have a different response characteristic, and will act different when given the same signal by the ecu. They can get more boost, less boost, or even a big boost spike by swapping N75’s.
PCV - Positive Crankcase Ventalation
TB – The throttle on these cars is drive by wire, it is an electronic throttle with a wire attached. Most common TB
problem just requires adaptation, or cleaning out with carb cleaner. This procedure shows
how to do a TBA. TBA can improve idle, and part throttle operation.
http://www.ross-tech.com/vag-c....html. To clean the TB remove it, and spray inside with carb cleaner. Wipe out the residue that gets built up in there. NEVER port a TB on a 1.8T it won’t idle properly.
TIP - Turbo inlet pipe
