AU2 XR8 tooo rich @ WOT

andoef · 23-09-2011, 11:20 PM

G'day fellas, i've been off the forums for a while as ive been 4wding a fair bit, but as an avid ford fan ive rescently purchased my 4th falcon, an AU2 XR8 Ute...

Anyways, i've come across a strange problem, which would have gone completely un-noticed had i not run it up on the dyno to check the AFR's...

So basically, Mixtures are fantastic, to the leaner side of stoich at idle, cruise and part load, however above 3000 at wide open throttle the mixtures go from 12.5 (expected), fly thru 11, 10 then off the richter, rich alomst instantly.

I suspected the MAF sensor could be responsible for this however backprobing the sensor gave a reading of 4.3v at 4000 rpm full load which seems normal??

The car has 130,000k on the clock and is stock except for a catback. All sensors appear to be opperating normally and no DTC's present..
Strange part is the car goes very well and has no symptoms, so this is pretty unexpected.
I knew another bloke with the same car near by with 200,000 on the clock so we ran his up and the AFR's were very similar...? Perhaps the airflow meters go out of calibration?
Basically, has anyone out there come across this?? Is this just a factory tune to protect the pistons ( hard to believe, as his was blowing alot of unburnt fuel out the pipe which would be unacceptable for a car when new).. Makes you wonder how many other XR's may be out there with the same problem un diagnosed?

Sterling · 24-09-2011, 12:14 AM

my 6cyl au throws out some black smoke at full revs... (ie 4500+ WOT)

Dave_Obsession · 24-09-2011, 12:17 AM

Quote:

Originally Posted by Sterling

my 6cyl au throws out some black smoke at full revs... (ie 4500+ WOT)

Change your o2 sensor and get your injectors cleaned out...
Checking the plugs and leads wouldn't hurt either...

andoef · 24-09-2011, 12:22 AM

Anyone with a similar vehicle able to post Dyno sheets without a tuned ECU?
Could be helpful..

mongrelEF · 24-09-2011, 01:28 AM

I would suggest fuel reg, vacuum operated regs can be fairly unreliable at low vacuum and tend to close early - particularly if the car has cams etc.
Most Falcons seem to do this in my experience, personally I've never bothered too much as you don't tend to crack 3k too often in the course of normal (i.e. Mr. Plod-approved) driving anyhow

andoef · 24-09-2011, 09:35 AM

Thanks MongrelEF, i will check it out, but I have my doubts as to wheather the fuel pressure would increase rather than fall off?

Also My main concerns are that such rich mixtures will be washing the bores of lubricant, contaminating oil and not to mention an absoloute minimum of 20% of torque and power going down the drain.

crakrz · 24-09-2011, 03:06 PM

There is nothing wrong with it. The top row of the O/L base fuel table on these things has a lambda of .88, then you multiply this with the WOT vs. RPM multiplier, which is approx .90 at 4000rpm and goes all the way to .84 at 5500 rpm. If you do the maths- .88 x .90= .79lamda or 11.6AFR, .88 x .84= .74 or 10.8AFR. It rich but its normal. So don't panic. I think most people would be surprised at how rich there's would be if it was put on the dyno. Mine was 10.0AFR at 5200rpm from factory. Don't go chasing a ghost, its all in the ECU.

Its not doing any damage as its only under high load/open loop. As you already said, cruising and mid throttle acceleration/closed loop, the O2 sensors keep everything in check.

-Craig

andoef · 27-09-2011, 07:09 PM

Your a gun thanks mate, exactly what i wanted to know...
Time to look at my tuning options.....
By the looks of your sig you would reccomend Quatrter horse, can this be used on the road with a laptop and wideband? Also is it relatively simple to use for someone that has used a haltech etc before??

crakrz · 27-09-2011, 08:09 PM

Yes to all the above. Catch code from your ECU is what's needed first. This will determine what's available to you. I have live datalogging on my laptop as I'm driving and then watch the live dashboard or replay the log when it's convenient.
Have you read this thread yet?

http://www.fordforums.com.au/showthread.php?t=11323999

andoef · 11-10-2011, 10:59 PM

Thanks alot mate... Think i,ll let her breath a little easier then consider this path... Did you get most gains in the high end area where it's is very rich or were there also reasonable gains thru low/ mid range also via spark advance etc?

crakrz · 11-10-2011, 11:36 PM

More gains in low to mid range torque than peak hp. Typical torque reduction features of the stock timing curve. Of course leaning out the top end got me a good rwkw figure but down low is where it matters everyday.