fast afr very rich. help

[bird]

hopefully going to the track this sunday. went for some test passes on the street, the target afr was at 11.2 my actual afr was close for first & second gear but dropped off to 9.19 and stayed their for the rest of the pass i had the timing set really low on the program (17.5 degrees at 24psi) for boost setting purposes only. could this cause that rich condiiton? ill obviously be turning the timing up at the track but if my wbo2 is fried i wont bother going. anyone run into this?

 

[clemsgn]

Just as a precaution, check the WB connector. Pull it apart and make sure it's extremely clean. Not just clean to the eye, but electrically clean. Use a good electrical contact spray cleaner and then plug it in and out 5 or 6 times. This should ensure the signal gets through correctly. This may seem like overkill, but I was having all sorts of problems, until I did this and now it runs great.
See if this helps. Let me know !

 

[Otto J]

Make sure your airtemp sensor is reading correctly, If the sensor fails it usually read -41 degrees, I cant tell you it will just go to 9.19. It happened to me

 

[bird]

thanks for the advice guys, ill check the ats & my o2 connections tommorrow. i was leaning toward the timing being really low & the unburned fuel being to much. the o2 correction was pegged at -10 the whole time as well.

 

[bird]

checked my o2 connection, looked mint but i cleaned it anyway. checked the ats it was reading 68 degrees fahrenheit wich was correct but the celcius reading was at 0. it should have been about 20. does the FAST program only show the fahrenheit?

 

[bobc455]

Careful!

If your sensor is reading 9.19 and you are not actually at 9.19, it might be trying to pull fuel out when you don't need to (i.e. lean = blown head gasket or something).

I had this happen to me once while on nitrous- I had an incorrect reading, and I was allowing -25% correction. OOPS! That was a very expensive lesson.

Make sure you set to -0% correction for WOT until you get this figured out.

-Bob Cunningham

 

[bird]

"bobcat" ran the car on the weekend. went a best of 10.51 @ over 130mph with a high 1.6 short. actual afr was still pegged at 9.19 during all my runs. correction was set at -12. timing was at 24 degrees. engine seemed to run very well, a little black smoke during pass. i tried bumping the target afr to 11.7 from the previous 11.2, made no difference. why is this thing reading so rich? ive got the sensor in the collector (switching it over to the downpipe this winter), and my ats is near the air filter (i heard it should be in the upper plenum) im stumped? anyone have any ideas?

 

[bird]

ttt

 

[bird]

went by norbys place this weekend. he thinks the sensor is good but just in the wrong place. possibly to much presure & turbulance in the collector. im going to switch it to the downpipe this winter and see how it goes. thanks you everyone for youre help. especially norbs.

 

[bruce]

The WB is assuming that there reaction process is relatively good. Too far retarding of the timing will indicate richer then actual. And by the same token, too far advanced will indicate a *false* leaness.

You have to double check the indicated AFRs with what the plugs look like, and a rough coorelation of fuel used to ET. An EGT would also help as a sanity check for where your at.

ie using 83 PPH @ 90% DC, a 10.5 AFR and running 13s, would indicate there's wayyyyyyy to little timing. Also probably a low EGT.
and by the same token, using 83s, @90% DC, running low 10s, an AFR of 12.5, and EGT of 1,800dF would tend to indicate too much timing.

And Knock sensors aren't perfect either. Add enough fuel and you can change the detonation frequency enough that the knock sensor misses detecting it.

 

[bird]

thanks for the response bruce. not running an egt gauge (yet). my dc was in the 70-87% range (72 inj ) most of the time depending on the boost. my timing was at 22-24 degrees. it only reads this rich after the boost hits aprox 22 psi. i could send you a log file if youve got the time to look. send me an email address.
thanks.