karl4x4

Anybody knows what happens at 2500 rpm? I have a wide band O2 sensor (in stock location) and digital gauge feeding my PCM and I noticed that the engine always runs slightly rich with or without load until it reaches 2500 rpm. When it reaches 2500, under med or little load it will run at 14.7 or slightly lean air/fuel ratio. Under hard load, it reverts back to slightly rich and WOT at any RPM it goes even richer. It's not speed related because it works in every gear.

Anybody knows what changes for this to happen? I would prefer if it always ran at 14.7 or slightly leaner except at WOT but when I program my sensor, it affects all RPMs and becomes too lean after 2500 RPM.

Same questionon different forum http://www.jeepstrokers.com/forum/vi...php?f=5&t=4129

cruiser54

Where's the OEM O2 sensor mounted then?

wrapstar

Are you talking post cat. if so your getting a false reading first off.

karl4x4

NO.. I have a wideband O2 sensor feeding a gauge with 2 programmable analogue outputs. right now, one is programmed to simulate a stock sensor (Its the default program)

I found many people on line with problems around the 2500 rpm range. Mine is not a problem at that speed. Its just more fuel efficient. I'd like to find out to keep it the same throughout the rpm range.

wrapstar

But down stream its not a true a/f reading. That why the location is being questioned.

karl4x4

As mentioned above, it is at stock location (more like stock distance from head). right after the 3Y header joins into one. Same average distance as stock. (there is a big variance in distance with stock manifold)... and straight pipe all the way back

mentalbreakdown00

Could just be stock programming, they are not using a MAF, so it's all old school system based off of temps, and RPMS, and is a guess to actual airflow, they might have double checked everything and set the best a/f ratio at that rpm for emissions...?

karl4x4

Thats a very reasonable explanation but with stock everything, at 2500rpm in 4th gear automatic you would be going 71 mph. A little to fast of cruising speed for me on a day to day driving..... if only in changed at 2000rpm. I would save a lot of gas.

wrapstar

Or buy a civic. Im asking because i've done quite abit of data loging and dyno tuning. But I guess I guess you know more then me

cruiser54

Sounds like it's in open loop.

karl4x4

I'm way to adventurous for a car. LOL

Dyno tunning... that's the ticket. So with your Dyno experience, what worked best? Found anything helpful you could share? Im always looking for "real life" tips.

DieselD

Going by this it could be a faulty TPS or coolant temp sensor. That is, if it's a problem. I dunno what you AFR should be.

To get your desired RPM of 2500 at a lower speed, you could add some slightly bigger tires

karl4x4

When I floor it, it goes quite a big richer, around 12.5. I think then it is in open loop.

When it reaches the magic 2500, it goes varies (bur run closer to 15) between 14.7-15.4..

96blackxj

what is your part throttle afr between 1k and 2500... and from 2500 and up..

i have been tuning cars since 2007 and every car i tune i set my part throttle cruising afr around 14.7-15.0 and wot should be around 13.0-12.8 any thing richer is wasting gas...

im about to install my wideband in my jeep and see what it does also using the analog out to use the narrowband output straight to the ecu so theres no check engine light

because it seems that if i drive the jeep in the 3 gear around town it gets better gas mileage then if i leave it in the od area but its also cruising at alot higher rpm

96blackxj

is there a way to tune the jeeps computer? i know those stupid programmers dont do anything... but i was thinking in terms of more of a air fuel controller like the ones the honda people and mitsu people use the apexi afc