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fourbysix
01-17-2007, 09:14 AM
HP Comp=http://img96.imageshack.us/img96/6215/hpcompqo3.gif

HP/AFR Comp=http://img206.imageshack.us/img206/3819/hpafrhd1.gif

TQComp=http://img167.imageshack.us/img167/9823/tqcompgc1.gif

I did a few quick pulls today, and we noticed a fairly severe lean spot in all of my graphs..does anyone a little more experienced with fuel tuning know what could be happening at this portion of a run?

fourbysix
01-20-2007, 04:31 AM
anybody, anybody at all?

DustenT
01-20-2007, 05:38 AM
Looks normal to me. If you need more fuel look into a Rising Raise Fuel Pressure Regulator. I'd leave it be. What mods do you have? Can you tune better than BMW?

fourbysix
01-20-2007, 09:49 AM
Take a look at the HP-Comp read out..there is a definate dip in the curve..meaning leanness(i've come to understand) would using a high octance fuel and some sort of SAFC..or any air/fuel controller (i think its an apex'i product im thinking of) work to maintain a better (more solid) toque curve? as for mods, it's virtually stock, just old..and needs some TLC to bring it back up to life..this weekend will be a major fluid flush, new starter, clean the TB, run some atf through the oil, new injectors, and a fresh tank of 98 then I will run it on the dyno again to see if that dip has gone away at all

DustenT
01-20-2007, 05:09 PM
The factory ECU is more than capable of providing fuel IF NEEDED. I would suggest cleaning your injectors and replacing your fuel filter. 14.7:1 on a N/A car is stoich, and it's ok to run a bit leaner than that to keep emissions down at higher RPMs.

Are you using a sniffer type wideband sensor (the kind that goes in the end of your exhaust)? Or did you have a bung welded on? Are you running a cat?

fourbysix
01-20-2007, 05:30 PM
wideband sensor, i am running a cat. I follow you're comment regarding the oe ECU, i just found that a promenent dip like was a little weird.

DustenT
01-20-2007, 05:38 PM
wideband sensor, i am running a cat. I follow you're comment regarding the oe ECU, i just found that a promenent dip like was a little weird.

Where is the sensor mounted? After the cat?

Here is Chad's stock dyno for comparison:
http://www.318ti.org/gallery/data/500/IMG_0143.JPG

fourbysix
01-20-2007, 05:42 PM
I dont know exactly where the sensor is installed..are you refering to the wideband probe? if yes, then its rammed up my exhaust.

Hmm..same little dip just way smaller..I would like to further investigate this problem..so how much of a ruler torque curve I can make..thanks for all the help man..

DustenT
01-20-2007, 06:03 PM
I dont know exactly where the sensor is installed..are you refering to the wideband probe? if yes, then its rammed up my exhaust.

It's important to know where the sensor is located. If it's located at the end of the exhaust, it's not going to be very accurate for three reasons:

1. The catalytic converter is there to burn up any fuel that may be in the exhaust, so after the cat the air/fuel ratio is skewed.
2. If the sensor is too close to the end of the tailpipe air from the atmosphere can skew the readings.
3. As the exhaust cools, the oxygen molecules condense while backpressure from the muffler slows the gas flow. This gives a false lean condition too.

You want to mount the wideband oxygen sensor as close to the engine as possible. I have a wideband bung welded after the 2 to 1 section in the exhaust.