AIT – Air Inlet Temperature 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.CAI
Cold air intakeCTS – 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?
PCV- Positive Crankcase Ventilation.
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!
Diode is said not to work on the 20ths
- 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
This system redirects combustion blowby into the intake of the engine to be 'burnt off'. As an engine operates, high-pressure gases are contained within the combustion chamber and prevented from passing into the crankcase (containing the crankshaft and other parts) between the side of the piston and the cylinder bore by piston rings which seal against the cylinder. However, some amount of gas always leaks past the piston rings into the crankcase.
DV - Diverter Valve
A pressure release system for turbos. It's purpose is to prevent compressor surge, and reduce wear on the turbocharger and engine. Diverter Valves ventilate back into the intake before the turbocharger. Blow off valves (BOV) relieve the damaging effects of compressor "surge loading" by allowing the compressed air to vent to atmosphereN249 - Boost Pressure Control Valve
This electronic valve is supposed to smooth out the Diverter Valve control at partial throttle. ECU - Electronic Control Unit
IC - Intercooler
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
An intercooler, or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged (forced induction) internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through nearly isobaric (constant pressure) cooling.Immobilizer (ECU Swapping Info)
All vehicles equipped with an immobilizer by 2002. Only exception is that some TTs in 00 had an immobilizer.
All vehicles equipped with an immobilizer in 2000.The immobilizers is a theft prevention measure. If you swap an ECU without matching up the ECU and the cluster, it will start briefly and then die repeatedly flashing the immobilizer light on the dash (looks like a car outline with the base a key). 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.
If swapping an engine into a car without an immobilizer/cluster, you can get software for swaps from many chip tuners that remove the immobilizer from the ECU.
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 - Manifold Absolute Pressure sensor
is located in the OE SMIC end tank. There are two different sized MAP sensors, and VW didn't 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 didn't 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:MAF - Mass air flow meter
2002 and earlier cars = large MAP
2003 and later cars = small or large MAP
AEB vehicles do not have MAP sensors, they have BARO sensors instead.
Click here to check if your MAF is bad. M
ir flow m
eter 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).
<table align="CENTER" cellpadding="0" cellspacing="0" width="90%"><tbody><tr><td>Quote, originally posted by WhiteG60 »</td></tr><tr><td class="quote">Basically the problem with MAF's is that VW and some/all of the OEMs run the PCV back into the intake tract or you're running a K&N filter or another cotton/gauze/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 regiment, you'd be hard pressed to ever have to replace it. </td></tr></tbody></table>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
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.
TB - Throttle Body
Modified by Boostin20v at 11:39 AM 8-5-2008
The throttle on most of these cars is drive by wire, it is an electronic throttle with a wire attached (only the earliest 1.8T were not drive by wire). 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.