I am a little curious on this subject. I dynoed my car with just a mac offroad h and a mac 3" exhaust and got 361rwhp and 349rwtq. I only had a 10-15min cool down time and the weather was very humid with a whopping 97 degrees. But my question is, do you think i dynoed low because my o2 sensors werent connected? Your probably asking yourself why I didnt have them connected. Well the reason for this was I had installed my h-pipe a few days before the dyno run, but the o2 sensors towards the back would not reach. So my friend decided to leave the front two disconnected also until I get my MIL eliminators in and the extensions. Anyways, I dont know if my dyno numbers were low because of not having the o2 sensors hooked up? If it did rob me hp, how much would I have gained with em on. Its kinda a stupid question, but I was told you ask the experts on the board to see what they would say. Thanks!
O2 Sensors werent connected, Does that mean low dyno numbers?
- Thread starter chrisle7220
- Start date
YES! The front O2 sensors are needed by the comp to regulate A/F mixture, you were running off the stored A/F maps and probably running very, very rich. The rear O2's are to monitor the cats, they are only for the OBD2 side of things and shouldn't affect how the car runs.
Here's my graph, you can see that the a/f dips down under 10 at about 4700rpm. Not sure if stock cobras are running this rich or not, but it doesnt look normal. What do you think about my a/f?
Last edited:
ttt
lwantSonicBlue
New Member
you are dumping way too much fuel a stock tune will go pig rich but not until above 5500 rpms at least that has been from the only two that I have seen at the dyno.
Im confused, so does it or doesnt it matter? LOL. Help!!
at WOT, you run open loop, so the system does NOT use the 02 sensors...they will not matter.
as for narrowband, it's not that they're inaccurate at 11-12...it's that they don't respond quickly enough and that they are generally inaccurate.
m.
as for narrowband, it's not that they're inaccurate at 11-12...it's that they don't respond quickly enough and that they are generally inaccurate.
m.
As mentioned above, WOt ignores 02 sensors - BUT, if you were in 'limp mode' from them being disconnected - that would affect wot performnce as well. Should have thrown a code though...
peace
peace
I forgot that WOT ignores the O2's and uses the maps anyway. But wouldn't the unconnected O2's and the associated code cause the comp to use a safe tune, not quite a limp mode, and would that affect the WOT as well?
*** Edit: Was thinking the same thing at the same time. ***
*** Edit: Was thinking the same thing at the same time. ***
Last edited:
Definately limp mode. EEC would consider Front 02 failure as catastrophic.
peace
peace
The O2 sensor readings produced in normal closed loop operation "trim" the A/F tables for BOTH closed and open loop operation. For instance, if the ECU is seeing persisitently rich readings in closed loop for a significant period of time, it will alter the tables to make them leaner in both closed and open loop. This is why you don't get maximum effect of a mod (such as CAI or cat back) on dyno in open loop until the computer has had enough runs to optimize or "trim" the tables. This is the "adaptive" function of EEC V.
Having your front O2's unhooked for a while could either trigger a "limp" mode or adversely changed the tables used at WOT.
Having your front O2's unhooked for a while could either trigger a "limp" mode or adversely changed the tables used at WOT.
That's what I thought.
Yeah I had my o2 sensors out for a while. Id say about a week or two. So the comp was probably reading some crazy numbers. But i got them connected again, so i should be all good now.
Users who are viewing this thread
