|
|
|
#1
|
|||
|
|||
Narrow vs Wide band Air Fuel Ratio guages
Background:
I have an 85 BMW 745i turbo that i'm tinkering with. I bought it out of California and it never ran right as it appeared to have had a number aftermarket add-ons for the purpose of emissions. These reminded me of the frequency valve junk that I would see on gray market MB's of the same era (this uses L-Jetronic). Last weekend, I removed all of the junk (which took some effort) and went back to a close to stock as possible. The result is that the car would barely run as it was running so rich. I managed to adjust the air flow meter enough to make it run very well but I need to fine tune it. BMW indicates 14.7:1 AFR as its optimal setting. While I own a tail pipe CO meter, it's not much use to me in this instance as this car is catalyzed. Question: I'm now looking at AFR gauges for the sole purpose of setting the car up. Should I buy a wide band AFR gauge and sensor or can I buy a narrow band and connect it to the existing single wire 02 sensor that was retrofitted along with the other emissions stuff. It's still plumbed in but not connected to anything. Thanks.
__________________
With best regards Al |
#2
|
|||
|
|||
Narrow band sensors are only good at measuring very close to 14.7. For actual tuning purposes a wideband sensor is the only real choice.
__________________
90 300TE 4-M Turbo 103, T3/T04E 50 trim T04B cover .60 AR Stage 3 turbine .63 AR A2W I/C, 40 LB/HR MS2E, 60-2 Direct Coil Control 3" Exh, AEM W/B O2 Underdrive Alt. and P/S Pulleys, Vented Rear Discs, .034 Booster. 3.07 diffs 1st Gear Start 90 300CE 104.980 Milled & ported head, 10.3:1 compression 197° intake cam w/20° advancer Tuned CIS ECU 4° ignition advance PCS TCM2000, built 722.6 600W networked suction fan Sportline sway bars V8 rear subframe, Quaife ATB 3.06 diff |
#3
|
|||
|
|||
Yup. To tune the car precisely you really need to use the wide-band. Narrow band is more like an "idiot light".
You can use the wide-band to get your settings dialed in and then replace it with the narrow band.
__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.” ― Brian P. Cleary, You Oughta Know By Now |
#4
|
|||
|
|||
Thanks all, wide band it is.
__________________
With best regards Al |
#5
|
||||
|
||||
All you need is to measure the voltage on an O2 sensor. David told me this once and he knew what the voltages meant. Unfortunately I don't. You will probably need to do research to find out but he said all I need on my 6.9 was some cheap sensor from pep Boys.
Fred
__________________
MB-less |
#6
|
|||
|
|||
Al, its not bmw its the whole world that slates 14:7.1 as the perfect ratio for internal combustion.
Its refir'd to as stoichiometric |
#7
|
||||
|
||||
14.7 is not a mixture, it is a base air pressure.
If the car has computer controlled FI, the mixture is meant to vary. Especially in a turbo which requires enriching at high boost.
__________________
MB-less |
#8
|
|||
|
|||
0.7 volts is the reading you want for Stoich. This is approximately 14.7:1. I say approximately because it depends on the condition of your engine. Some cars simply do not like to idle at this mixture. Fact of life, deal with it.
Narrow band gauges are only good at a steady speed. Anything which changes the air flow (acceleration, deceleration, increased load, etc.) causes the O2 reading to change which makes the NB wonky. It'll "peg out" either lean or rich and can't differentiate between the opposing conditions. It just knows it isn't "right". Hence the "idiot light" analogy. Wide band can track which way the reading is going which gives you an idea of which way you want to tune that range. 14.7:1 might be fine at an idle but may be too lean or rich at a cruise or power on rpm range. Just gotta for for the best average in this case (CIS systems)
__________________
“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.” ― Brian P. Cleary, You Oughta Know By Now |
#9
|
|||
|
|||
Clearly Emmmerik has got everything figured out, why would you try to tell someone like that anything?
|
Bookmarks |
Thread Tools | |
Display Modes | |
|
|