swathdiver
Full Access Member
What's it for? How do you use it?
2008 Yukon Denali, 135k miles, part 2!!
- Thread starter tgui
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
What's it for? How do you use it?
It measure the air fuel ratio. This one is very sensitive.
When you change things like headers, intakes, cam, etc you change the VE (volumetric efficiency) of the engine, how well it breathes. When it breathes better you gotta add more fuel, but you cant do that well without something like this sensor.
My Yukon idles like crap now with my headers and exhaust because of the changed VE. Too rich you can even kill catalytic converters. Finally I can dial things in.
Ohh, and you can make good amounts of HP too ;-) I had one on my subaru and let me dial in a shit-ton of power.
I can tie this one into my HP Tuners software
swathdiver
Full Access Member
Ok, I gather then it allows more precise tuning than the E38. The ECM shows the AFR in a different way, mine is normally 1:1 but at WOT it might go to .9:1 or .8:1 with the BB tune. Is the Mass Air Sensor not able to adjust enough until the maps are reprogrammed?
HiHoeSilver
Away!
swathdiver
Full Access Member
Me too!
Your measurements are in lambda. 1:1 is stoic which is ~14.7:1 gas AFR.
The stock O2 sensors are narrow band, can only read a narrow range of AFRs just outside of stoic. They're good for low load engine use where gas mileage is cared about. Outside this is PE mode, power enrich where you're flooring it. Stock O2 sensors arent used here. There is GM from factory calculated VE table that allows for quick RPM/Load lookup for how much the injectors are squirting in.
Sooo, when you change the engine VE with headers you need to update the base VE table and measure (much more accurately than stock sensors can) the near stoic AFRs. THEN you use the wideband when flooring it to measure things around 12.5:1 which you cant do with the stock narrow band O2 sensors.
MAF is only used for low load outside of PE mode driving.
swathdiver
Full Access Member
Ok, I mostly understand what you're saying. I just don't remember doing this with our Buicks when we added 300+ horsepower to them. Maybe I've just forgotten.
I had an hour. Drivers header out. Uuhhggg my to-do list just got longer.
- header denting for clearance
- engine mounts
- trans lines all need to be replaced
- front shocks are dead
- wideband install
155k miles, no surprises though
Easier the 2nd time. Still annoying.
- header denting for clearance
- engine mounts
- trans lines all need to be replaced
- front shocks are dead
- wideband install
155k miles, no surprises though
Easier the 2nd time. Still annoying.
Drivers mount in! I also took some time to hammer more space for the drivers O2 header that was hitting the body. I probably dont need to since these engine mounts will keep the engine still.
Out and then leaked fluid all over the floor. Thanks gm!
Trans supported then 2x4 jacked on the back of the oil pan. It's cast aluminum and braced there.
After. No damage.
AFR mount in!
Thanks for leaking all over my floor like a rubber fruit gusher. Remember those snacks?! ;-)
Out and then leaked fluid all over the floor. Thanks gm!
Trans supported then 2x4 jacked on the back of the oil pan. It's cast aluminum and braced there.
After. No damage.
AFR mount in!
Thanks for leaking all over my floor like a rubber fruit gusher. Remember those snacks?! ;-)
