I bought the car (98 A4 1.8T, AEB) with a "TAP Stage 2 12.5 psi" chip installed. Carbonio Intake, FMIC, test pipe, Miltek exhaust added.

A few months ago, the K03 lost its wastegate flap (almost), and installed a custom modified "K04" from Turbo Concepts. Also installed a boost gauge (duh!).

With stock injectors, the car is now boosting:
13 psi at 3k, 18 psi at 4k, 15 psi at 5k, 11 psi at 6k, 6 psi at 7k.
No codes (lean).

I would suspect that the higher boost (stock is 7 psi) would cause a 'lean' condition (at least mid range, at 18 psi vs. 7 psi)? Stock injectors should be 210cc, operated at stock 4 bar (flowing 242.5cc).

If that is to be expected, but not occurring: is the ECU (and chip) "turning the boost down" or otherwise prevent 'lean' condition?

Stock boost is 7 psi (I have a trained stock ECU as well), the TAP chip (supposedly) increase (peak?) boost to 12.5 psi (not verified; did not have boost gauge when stock K03 and TAP was in). No 18 psi peak.

Is the chip 'controlling' the boost?

 

Subscribe..

 

Anything you intended to say with this?

 

Nope..Im curious to know if ecu controls boost myself.

 

Since there are no 'takers', let me rephrase/add to the question.

With the custom/modified K03/K04 and the "TAP stage II - 12 psi" chip (no tune or injectors or else), I get the following boost over rpm curve:



Engine is AEB, ECU is drive by cable, MAF, ECU is 8D0907557P.

Here is the info on the wheels:

COMPRESSOR WHEEL
Inducer: 41.0 mm
Exducer: 54.0 mm
Tip height: 5.6 mm
Blades: 6 double, staged , extended tip

TURBINE WHEEL
Inducer: 44.5 mm
Exducer: 40.44 mm
Blades: 12
10 degree clip

Compressor housing shape-matched to larger compressor wheel and blade shape.

With the above in mind:
a) how is the chip likely influencing the boost curve?
b) what would a MBC, EBC do?
c) what VAGcom info/logs would provide further inside on what the turbo is doing, what the tune and other hardware is doing?

 

A. The chip increases the amount of boost or air allowed into your motor. You car has a built in boost controller called an N75. The chip modifies this. So, if stock boost is set at 8 psi, your chip now allows 18 psi while adjusting for the higher air/fuel ratio, timing, no limp mode, all that good stuff.
B. A MBC/EBC do the same thing, its just that one is electronic. They effect the opening and closing of the wastegate allowing more or less boost into your motor. The longer your wastegate remains closed, the more boost you are allowing into your motor (essentially). The MBC/EBC controls the watsegate. Keep in mind, a MBC/EBC does not take the place of a chip. All it will do it force more air into the system without adjusting anything else. A MBC/EBC should be used in conjunction with a tune. Doing otherwise can result in limp mode, blown turbo, and blown motor...
C. A VAG controls and monitors many things. It can monitor boost requested vs. boost received for example. It does alot of pin-pointing and helps worlds with troubleshooting.

 

"So, if stock boost is set at 8 psi, your chip now allows 18 psi while adjusting for the higher air/fuel ratio, timing, no limp mode, all that good stuff."

With stock turbo the chip did what it's name says: 12.5 psi. Changing the turbo a K04 type increased the boost to 18.5 psi, no other changes.

Can this be explained?

Given the boost curve, is the chip responsible for the curve, or the turbo (or both?)? Can VAGcom data help answer the question? (Note: my ECU is drive by cable, no MAP info I was told).

 

Ill throw out my understanding of how everything is happening. Modern engines are controlled by a myriad of sensors which all monitor various parameters to optimize performance and economy. When you "chip" your car, you are installing a piece of hardware which contains a difference set of parameters for the engine. The ecu takes readings from the sensors and checks the tables and adjusts various things to make the actual readings closer to what the requested table value is. Does that make sense?

So with your boost question, here is an example of what I'm on about. The MAP sensor tells the ECU how much pressure is in the manifold at the moment. The ECU checks a table which says how much pressure there is supposed to be. If the pressure in the manifold is less than the table value, it keeps the wastegate closed. If it is greater than the table value, it sends a signal to the n75 to open the wastegate and relieve the pressure until the value match.

 

That's in line with my thinking (but need to replace MAP with MAF signal, since I was told my ECU does not have pressure input). This could happen in my case:
The TAP chip has table values ("12.5 psi" or corresponding flow for the MAF), but the custom turbo still manages to get up to 18.5 psi (at 4000 rpm), 'overwhelming' the ECU/chip command.

The chip at higher rpm manages to get the pressure/flow down and in line with the table, (opening the wastegate), until the turbo capabilities fall off below the table values (wastegate closed).

Understanding what is going on with the current set up would help me to de-bottleneck the setup (for example MBR to find out what the limits of the turbo, injectors, etc. are), using VAGcom logs to keep an eye on the status (air ratio, timing, etc. if that is possible with VAGcom).

 

It might be that your wastegate is not able to vent pressure fast enough with 4K rpm being the point at which the engines intake is able to take in enough air to release the pressure. I would call the guys who you got the chip from and ask them why you are having such a high peak boost, perhaps the chip design is misleading from the name.