random rolling a/f ratio?
Thread Starter
Intermediate
Joined: Jan 2016
Posts: 26
Likes: 3
random rolling a/f ratio?
2007 Z06 heads, cam, intake, exhaust. I have notice at warm start it takes up to 30 seconds for the car to get to around 14.7 on my a/f gauge. It will hover around 19.1 (general number but lean) and slowly work down. I am not really worried about this , maybe I should be IDK.
My concern is sometimes when coasting to stops it can change either way. I have seen it slowly go up to 19.1 or even back to the 13.1 range and stay lean or rich for up to 30 seconds. After which it will go back to normal. Any insights? Thanks in advance. Joe
My concern is sometimes when coasting to stops it can change either way. I have seen it slowly go up to 19.1 or even back to the 13.1 range and stay lean or rich for up to 30 seconds. After which it will go back to normal. Any insights? Thanks in advance. Joe
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,629
2007 Z06 heads, cam, intake, exhaust. I have notice at warm start it takes up to 30 seconds for the car to get to around 14.7 on my a/f gauge. It will hover around 19.1 (general number but lean) and slowly work down. I am not really worried about this , maybe I should be IDK.
My concern is sometimes when coasting to stops it can change either way. I have seen it slowly go up to 19.1 or even back to the 13.1 range and stay lean or rich for up to 30 seconds. After which it will go back to normal. Any insights? Thanks in advance. Joe
My concern is sometimes when coasting to stops it can change either way. I have seen it slowly go up to 19.1 or even back to the 13.1 range and stay lean or rich for up to 30 seconds. After which it will go back to normal. Any insights? Thanks in advance. Joe
at less than WOT and crusing, the ECM should be holding the A/F at 14.7, and at WOT, should be around 12.5~12.7; both of which are pre-cat numbers.
Hence at less than WOT, the system is running closed loop, then at WOT it goes into open loop instead.
Also at start up, the heaters in the O2 sensors are powered on, and this give kind of a funky reading until the O2 heaters are shut off once the car warms up to get a real reading of what the motor is doinig.
Thread Starter
Intermediate
Joined: Jan 2016
Posts: 26
Likes: 3
Thanks for the reply, I should have posted no cats and W/B sensor is in the original rear O2 location. All readings I am seeing are actual in relation to what the A/F ratio is. 99% of the time it is 14.7 cruise/idle, 12.8 Wot minus dfco
I don't no if the tuner changed the start up A/F for hot start conditions or why.
My real concern is the random coast down issue. Either I have a bad sensor, failing fuel pump, or power draw from unrelated component, etc.
I ran the HPTuner on one occasion only to see the cars 02's go flat during an episode. all temps normal, battery good, no other signs or lights.
Just thought I would ask the question as I am puzzled. Thanks.
I don't no if the tuner changed the start up A/F for hot start conditions or why.
My real concern is the random coast down issue. Either I have a bad sensor, failing fuel pump, or power draw from unrelated component, etc.
I ran the HPTuner on one occasion only to see the cars 02's go flat during an episode. all temps normal, battery good, no other signs or lights.
Just thought I would ask the question as I am puzzled. Thanks.
Race Director
Joined: May 2004
Posts: 16,667
Likes: 1,209
From: Raleigh, NC
St. Jude Donor '15
Normal. Sensor probably isn't heated up yet when you're getting the lean readings at start up. It isn't going to hurt anything even if it is correct
The spikes to 19 during decel is probably deceleration fuel cutoff.. normal
The spikes to 19 during decel is probably deceleration fuel cutoff.. normal
Last edited by schpenxel; Jul 25, 2017 at 10:22 AM.
Burning Brakes
Joined: Jun 2015
Posts: 1,190
Likes: 311
From: Shelbyville Kentucky
It will be in open loop using the VE tables till the engine warms up. (normal)
Adjusting the VE table up a bit could bring this closer to 14.7
When coasting the CPU can shut off the injectors showing a full lean condition (normal)
Make sure you wideband is not after your cats.
Adjusting the VE table up a bit could bring this closer to 14.7
When coasting the CPU can shut off the injectors showing a full lean condition (normal)
Make sure you wideband is not after your cats.
