Need some input on A/F ratio from my dyno run today! Any input is appreciated!

[AlbertD]

So went with some of the guys to a mustang dyno just for fun to see what we would get... (None of us think much of dyno numbers, ET is where its at baby!) Well... I encountered something fairly strange with my A/F ratio.

Apparently the sniffer had some issues between 4900-5850 so I'm not worried about that portion of the graph... but, I'm definately worried about the fact that my A/F ratio steadily gets more rich starting from 3500 (12.8) till 6500 (11.4)... Also what the hell is up with the dip in between 6300-6400 (11.1) I know when the O2's go bad that the A/F ratio can be thrown off... but my question is do you think that could be my problem? Or do I need to get my car retuned correctly?

Aside from the strange A/F ratio I was extremely happy with my cars powerband! I wanted to go higher than 6500, but my driveshaft started vibrating I know for a fact that I was still building power past that point even with the stock manifold! Check out my HP for WCF, I got a big laugh out of that.

Anyways if it turns out that I need a new tune, I'm just going to go all out and slap a FRPP or C&L manifold on there, with a GT500 TB, and 39lb injectors and see what happens

Let me know what you guys think I should do! Thanks in advance.

Here are my power mods...

BBK LT headers w/ o/r x
P&P heads... 286/203 CFM Ports
Custom machined factory 34mm intake valves & Custom -machined factory 37.5mm exhaust valves
Multi axis competition valve job
127500s (locked full advance) w/ springs and retainers
JLT CAI
Stock TB
Stock Manifold
UD pullies
Electric WP

Red=TQ
Blue=HP
Green=A/F

 

[JeremyH]

At wot throttle on the dyno your in open loop so its not reading the 02s.
Tune issue maybe.

 

[mynameismike65]

That a/f reading is absolutely retarded looking on that graph lol

 

[Marc s]

At wot throttle on the dyno your in open loop so its not reading the 02s.
Tune issue maybe.

+1. Also, I seen funky readings like this when the dyno's O2's are going bad.

 

[AlbertD]

At wot throttle on the dyno your in open loop so its not reading the 02s.
Tune issue maybe.

Ah I see, didn't know that about the O2s, thanks for the input!

That a/f reading is absolutely retarded looking on that graph lol

Haha, yeah tell me about it. It's all ate up.

 

[AlbertD]

+1. Also, I seen funky readings like this when the dyno's O2's are going bad.

Thats good to hear. Thanks!

 

[BAKnBLK2010]

If you still have cats and your rear O2's are turned on the car could have gone into cat enrichment mode to cool the cats. I've seen this happen on the dyno a few times. If your rear 02's are turned off I don't have a clue what happened.

 

[AlbertD]

If you still have cats and your rear O2's are turned on the car could have gone into cat enrichment mode to cool the cats. I've seen this happen on the dyno a few times. If your rear 02's are turned off I don't have a clue what happened.

Wow thats interesting... I am catless w/ rear O2s off, so it won't apply in my case.