It's a mass-air-metered car. That air you're dumping into the atmosphere was already measured by the MAF and the engine fuels for it since it's supposed to be there. It isn't and you get a rich spike on shifts. That excess fuel goes unburned and is therefore wasted.

Interestingly, I've never once seen anyone use an Apex'i S-AFC in an A4. Maybe because most of our membership was still playing with GI Joe when the import boom took off (that's meant as an observation, not a dis), but one of those would go a long way toward saving catalysts when someone uses done type of dump valve without a de-MAF tune. It has a feature called deceleration airflow correction, which removes that rich spike on shifts by watching the throttle position sensor. When it sees TPS voltage drop sharply (as when you jump off the gas to shift), it cuts fuel by a user-set percentage. That'd allow those of you who want to dump your charge air to do so without plugging up your cats with carbon residue from overfueled shifts.

 

Jeremy, quit being so smart. You're making the rest of us look bad.

 

With age comes experience lol. After 15+ years tuning Japanese and German cars, I ought to have learned a few things

 

Thinking of getting my 99 A4 1.8t Chipped. Do i get the DV Splitter B4 chip or after chip? Kind of a noob here so please be kind.

 

Before, preferably. That way you don't have to worry about the stock DV failing after you get chipped.

 

at the same time
order ur dv, send in your ecu to apr, or whoever, the day before the DV is expected to arrive!

 

Emil sells 'em for $70 on his website. Krauto Parts

 

^^^ what he said. Get em from Emil. Killer price, stand-up guy, and quality parts.

 

Thnks for the great advice. Are Emils dv valves a "splitter" type like the forge? Would like the swoosh sound if possible. Thanks again for treating a noob like me as good as you have so far. Lol

 

Hey OP if you need help with DVs PM me or text my cell 607 279 577 six and I can show you what I have