Vagitarian

Hey guys, I am looking to get a good pass at the track and see what all this setup can push mph wise in the 1/4 mile. I street tuned it with a 3" turbo back exhaust, no cat and a flowthrough muffler. My afr's are about 11.2 - 11.4:1 at full boost but if i want to drop the middle section of my exhaust off at the track to run open dp, then I also lose my 02 wastegate bung as its in that section

So I will no longer have a display of accurate afr while going down the track.

Will the tune be affected greatly? Im thining because my street exhaust is very free flowing and tuned slightly lean I may still be in the safe zone unless there is a chance it would affect it more than I think it may

V-SPEC 1

With that a/f at full boost with said good flowing exhaust, u should b fine taking ur Dp at the track and still have a safe tune.

Vagitarian

ya I figured the exhaust already being straight through, just full length it may not be a huge difference

gabocastano

Just to be safe put a gallon or 2 of higher octane fuel when in the track.

wantboost

iTrader: (2)

Depending on how much backpressure your full exhaust causes (even the best straight through exhausts can have up to 2psi) you might see the car lean out about half a point depending on the weather.

you'd still be well within the "safe" zone but like suggested above doing something to bump octane a couple points can't hurt. if you have something like water/meth injection then set it to reach full flow sooner and maybe inject a tad bit more.

blackeg

this is exactly what i used to notice going from full exhaust to open header (ecutout at the end of the downpipe)

Vagitarian

Well since from what ive read on here and from some searching ALL say the car will lean out slightly, I will simply burn a new "open d/p" tune and add a slight ammount of fuel. I like the safety of 11.5:1 especially when there is no gauge to watch!

wantboost

iTrader: (2)

You should be fine.

marc59

You can also hook your af gauge to your map sensor signal wire...ran my turbo gsr hatch that way for 2 years and tuned it that way as well

eg:R

What will this do? will it read the a/f more Accurate ?

m4xwellmurd3r

Nope. What thatll do is read map vacuum/pressure as an afr number. No idea why you would want to do that since the numbers would be useless

wantboost

iTrader: (2)

That makes absolutely no sense whatsoever

It would just read boost pressure as an afr value that would have nothing to do with how the motor is running.

boostjunkie757

pretty sure he was only referencing where he had pulled the power source for the sensor...not where it was actually pulling its reading from to display results.

m4xwellmurd3r

No he clearly states he hooked his gauge to the map sensor SIGNAL wire. As in the map sensor output. Not the power wire, which wouldnt make any sense anyways since the afr gauge needs to be connected to the o2 sensor wire

wantboost

iTrader: (2)

The value displayed by the wideband would then be the same regardless of rpm and how the motor is actually running.

15psi would show the same value on the wideband whether you make it at 2,000rpm or 9,000rpm.

Totally stupid idea, all you're doing is displaying boost pressure converted to lambda which has no role or purpose in monitoring engine operating conditions.

boostjunkie757

that was about to be my next comment, but i couldnt have imagined doing it that way since youd probably have extra wiring laying around which wouldnt exactly be good, what kinda recipe for disaster that would make...unless he isnt running an o2, which in that case you couldnt run an afr anyway...im still trying to make sense out of how he got an air fuel ratio reading out of a manifold absolute pressure sensor.