beebone

Hi,

With stock injector, WG and K26/8, chipped (DME and KLR), EBC in 1 bar boost, 3" cat bypass pipe and exhaust.

Any idea about, the AFR when off throttle?
I just installed a wideband O2 monitor, the AFR is pretty rich. I've found the interesting thing, the AFR is 20 when off throttle!!! Here is what I've seen from the guage


-Idle: 11 (cold), 12 - 12.5 (warm)
-Low RPM: 12-12.5
-Boost start to high boost in high RPM: 11
-Off throttle: 20 !!!!

Let say, when the RPM drop down to around 1200rpm, the AFR return to 12 something. Everytime like that. Something wrong?!?!?!

Rogue_Ant

Off-throttle, the DME cuts fuel. I turns off the injectors completely until RPMs drop down to ~1200rpm or you get back on the throttle.
This is completely normal, and will not hurt anything.

What is your fuel pressure? You should not be running that rich during part-throttle...


-Rogue

toddk911

Not to hijack but partially on topic:

I have noticed that when at idle or coasting in neutral my EGT are pretty normal at about 1,100-1,200. But if I coast while still in gear my EGT really drop.

Any ideas Rogue?

Chris White

it should be a bizillion to one ratio...but your gauge will only indicate to about 20:1 (depends on gauge)
Rouge is right, no fuel at all during engine braking.
The 12.5:1 at warm idle is wrong. Should be 14.7 +/- . Typically the engine will be oscillating around that point – going from slightly above to slightly below every second. This indicates that the O2 sensor is in the loop adjusting the mixture. If you are ‘stuck’ at 12.5 then your O2 sensor is not in the loop.

Long term idling at 12.5:1 will carbon up you engine….

theedge

Coasting while off the throttle? Then there is no fuel being injected (above 1200RPM or so), so EGTs would drop. Coasting in neutral, the DME is still injecting fuel.

schip43

Yep 12.5 at idle is rich should be 14.7 What's your fuel pressure at idle? I had a similar problem, I was lean at idle. I did not have any piggy to add or subtract fuel. So I kept an eye on the AFR's while I let the engine idle.
I found the locking nut for the FPR was gone?! Found a new nut started to turn the FP up and the AFR was back at 14.7.

Just a thought.

Rogue_Ant

+1

beebone

the injector is stock spec, only have the 3 bar FP regulator.

beebone

So adjust the dip switch in DME or minor adjust the screw in AFM can help?

beebone

not a problem

beebone

I dont think my engine will be oscillating becuase the O2 just connect to the guage only. The O2 just added, originally didnt come with. (Mine is EU spec, no cat, no O2).

Yes, the wideband is not in loop at all.

Chris White

Hmm...that makes it a foreign foreign car..!

I am afraid that the usual 3.0 bar FPR set up won’t work that well your car unless you get a good set of chips (Vitesse) to go with it. Most mods rely on the O2 sensor to bring the mixture back to 14.7 when off load.

beebone

The chip is ProMax http://www.promaxmotorsport.com

This is UK tuner, so the chip match my engine spec. The only thing is the carbon deposit on the exhaust tip and kinda a smelly gas, the fuel consumption is excellent, the fuel consumption is good, can run 450km per tank.

beebone

I double check the fuel map today, seems pretty good but the idle. So now, I adjust the boost back to 1.1 bar, the AFR:

Idle: 12.5
low load: 12.5
Heavy load: 12-11.5

So here comes the idea, the O2 is just for the guage, no actual function for the DME (EU spec), I think the system is closed loop from the mod chip, am I right?

Hence, I did the adjustment on the AFM to become leaner, so now the AFR at idle is 13.2-13.7, pretty good!!!

New question, anyone did the adjustment on AFM? I took long way to turn counter-clockwise to hit 13.2, is it normal?

fbgh2o

What kind of driving, city or highway? 450 km seems low even for city. I would regularly get 675km highway and 540km city

You are way too rich. Have had the same issue in the past, turned out to be (1) bad grounds and (2) a bad O2 sensor.