View Full Version : What is my 'chip' actually doing?

01-30-2011, 10:16 AM
I bought the car (98 A4 1.8T, AEB) with a "T.A.P. 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:
10 psi at 2k, 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 T.A.P. chip (supposedly) increases (peak?) boost to 12.5 psi (not verified; did not have boost gauge when stock K03 and TAP was in). Now (from modified turbo with K04 size compressor) 18 psi peak but falling off.

Is the chip 'controlling' the boost to prevent 'lean'?
Is the turbine (turbo) running out of breath at higher RPMs?
Or both?

Can VAGcom tell a bit more? What can/should I log?

01-30-2011, 11:39 AM
18 psi peak is somewhat normal for a chip. If yours chip is truly a ".9 bar" chip (~13 psi), then it seems that it is overboosting a bit. A spike like that on a K03 isn't too much of a problem because the K03 doesn't really flow that much and the risk of going lean at the RPMs where that happens is accordingly low. A spike like that on K04 can be a problem because it is flowing quite a bit more and the fueling isn't matched for it (your chip is not adjusted for the flow a K04).

The reason the boost tapers off is because the stock K03 just can't keep up. To keep the turbo from spinning it's guts out trying to make 1 bar at redline, the chip reduces the boost request (decreases the N75 duty cycle) so as not to kill the turbo. The K04 can hold boost longer, but your chip doesn't know that, so you are limited to the K03 boost curve. This is probably for the best because you don't have the fueling to do it anyway. Your injectors are too small to take full advantage of the K04 at the higher revs.

So to answer your question in order:

1 - Yes, the chip is controlling (tapering) the boost. It is more to protect the little K03 that it is tuned for, but going lean is also a concern.
2 - Yes, the K03 that your chip is tuned for is completely out of breath by redline. Your K04 is better, but your chip has no idea it's even there, so the taper is the same.
3 - Yes, both.

Generally speaking, running a K04 on K03 software is ok. But yours is custom modified, so there is a concern. The concern is running lean due to the high boost "spikes" that are often part of the K03 chips, combined with the higher flow of the K04, and the tiny stock injectors. In vag-com you should look at or log the following to make sure everything is safe:

- Long term fuel trims (032)
- Timing retard (020)
- Lambda values (031,033)

If the thing is going lean, which it probably is, then you'll need to back down the boost with a manual boost controller in parallel with your N75. The better solution would be to get a real K04 tune with all the correct supporting mods (injectors, etc) so you can take advantage of your K04.

01-30-2011, 03:47 PM
Or both?

It's both and those values look normal.