Running Rich *Dyno Chart Inside*

**ActiveMonkey** · 08-01-2017 07:59 AM

The car: 2000 S4, 6MT, current mods are APR Stage 2 Tune, 3" straight pipe from the collector back, OEM Cats. The reason it has a stage 2 tune while on OEM cats is that i got an absolutely crazy deal and couldn't pass it up.

Ok, now the problems. While under WOT at about 4000 RPM you feel this little hesitation that lasts until about 5500 rpm then it almost lets off. It feels like someone lightly pressing on the brakes. So with he 034 Motorsport Dyno Day coming up i threw it on to get some data.

Before the dyno day, this is what i have done to try and fix it.

1. Boost leak check
1a. Pressure tested
1b. Vacuum tested with brake clean

2. Replaced throttle body boot with 034 verson

3. Replaced Fuel Pressure Regulator

4. Tried adding 100 octane gas in case the timing was too aggressive

5. Check DV to make sure their good.
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Below is the DYNO results showing 218 HP/257 TQ. What i found interesting is that the boost levels (Green) look ok, but the Air/Fuel Ratio (Black) went super rich right where i felt the hesitation.

Any thoughts on what this can be?

**CELison** · 08-01-2017 08:04 AM

Throw in a new set of plugs to start. An OTS tune is usually not going to be the issue. Sounds like you have a hardware problem. Run logs and post em up.

**erykv1** · 08-01-2017 08:16 AM

so correct me if im wrong... the tune is for no cats, but you are running cats?

x2 on the logs.

**CELison** · 08-01-2017 08:17 AM

Only reason a tune would be for no cats (don't think apr even makes one) would be because of anti-lag.

**S4James** · 08-01-2017 09:29 AM

You cant run stock downpipes on a stage2 file.

**1thenaton1** · 08-01-2017 09:37 AM

probably have an EGT sensor that is not working and you are dumping fuel

**ActiveMonkey** · 08-02-2017 10:05 AM

Originally Posted by 1thenaton1

probably have an EGT sensor that is not working and you are dumping fuel

I sent to Griffin Motorworks (Geat Shop!) and they scanned the car with VCDS. 2 bad EGT sensors and 1 Bad O2 Sensor (Bank 2 Sensor 1)

The parts are now on order...

**chris86vw** · 08-02-2017 10:23 AM

Originally Posted by CELison

Only reason a tune would be for no cats (don't think apr even makes one) would be because of anti-lag.

The majority of tunes for no cats are nothing more than removing the annoyance of the check engine light for cat efficiency. This kind of no cat tuning predates anti lag by about 10 years.

Unless it has anti lag virtually any tune for no cats can work on a car with cats with reasonable results, often better than a tune for a car with cats running no cats, especially on older me7 used here which is kind of slow to respond. Less of an issue on the 2.7t compared to the 1.8t but if you've ever heard an A4 or say a GTI with a loud exhaust accelerating and its going waaa waaa waa waa under boost it likely has a tune meant for a stock exhaust and the wastegate duty cycle can't respond fast enough to control it properly.

**chris86vw** · 08-02-2017 10:29 AM

Originally Posted by ActiveMonkey

The car: 2000 S4, 6MT, current mods are APR Stage 2 Tune, 3" straight pipe from the collector back, OEM Cats. The reason it has a stage 2 tune while on OEM cats is that i got an absolutely crazy deal and couldn't pass it up.

Ok, now the problems. While under WOT at about 4000 RPM you feel this little hesitation that lasts until about 5500 rpm then it almost lets off. It feels like someone lightly pressing on the brakes. So with he 034 Motorsport Dyno Day coming up i threw it on to get some data.

Before or after putting in the parts you ordered, log your intake temp vs throttle angle. These ecus will shut the throttle down if intake temps get too high. Since the pressure sensor is pre throttle body you'll see normalish boost but the car goes super rich (due to lack of closed loop wideband like some later versions of me7) so it is just fueling based on the airflow.

**ActiveMonkey** · 08-02-2017 12:59 PM

Originally Posted by chris86vw

Before or after putting in the parts you ordered, log your intake temp vs throttle angle. These ecus will shut the throttle down if intake temps get too high. Since the pressure sensor is pre throttle body you'll see normalish boost but the car goes super rich (due to lack of closed loop wideband like some later versions of me7) so it is just fueling based on the airflow.

I know those two values show up on my reader. I will see what they are later today. I know my IAT have been ~120-150 depending on driving and ambient temp.