I have a major problem with my A/F ratio being super high - almost or at detonation levels and I just want some suggestions/advice as to what the problem may be before I go to the dealership or performance shop to start trying

I dynoed with the rest of the FGC crew this past Saturday at Next Level Performance. They use a 2wd Dynojet 248.

The last time I was there I made HP 243.6, TQ 235.9
My A/F was around 11 to 13.

My recent dyno I lost power and torque and made HP 236.4, TQ 231.2
Now my A/F was around 16, 17 when I pass 3500rpm (gradual curve). Very dangerous detonation level and too lean for my liking.

My mods from my last dyno to my recent dyno listed in my sig haven't changed.The only thing I "changed" was I switched to Royal Purple synthetic oil before the recent dyno session.



Why is my A/F ratio so high now?

Perhaps my RT cats have imploded? But if they did, wouldn't the check engine light come on?

Maybe my o2 sensors have gone bad?

Could the synthetic oil have anything to do with it? (i don't think so)

The performance of my car still feels the same. Nothing (speed, engine reving) has changed.



Either way, I plan to take my car to the dealership and hook it up to an sensor to see if i've thrown any error codes. If its the cats, I plan on changing to crawford cats (just bought used ones).

I'm just kinda bummed at the high A/F ratio. I'm actually afraid to go past 3Krpm now. Jeez....

 

A bad day? I know it may sound stupid, but it feels like my car has "faster" days....this was also true with my previous cars...

 

bump

 

It is not unusual to experience high A/F ratios when you have as many "breather" mods as you have. Also, was the AF taken before the cats or at the tail-pipe? If at the tail-pipe, I've had tuners tell me that you can ADD 1 full ratio to what you are getting at the tail-pipe cuz by the time the gases make there way through your cats and through the reat of your muffled exhaust system, it's leaned out about a point. I have simular mods as you when I was NA and I consistantly pulled a 15:1 AF ... hope that helps.

 

Ian...I have issues with that dyno shop and that machine. My A/F was reading 13 for several thousand rpm's...and on an FI engine...thats bad. But...I had a 5 hour tune the day before and my A/F barely goes above 12, all well before 5000 rpms. To make things worse....Saddler's car showed close to a 15 A/F on his Vortech. I have to question the sniffer on that machine.....

I'll have my numbers downloaded from the zeitronix in the next hour or so and I'll see where my numbers have really been and compare it to that dyno sniffer....

 

that dyno = worthless

 

Agreed


Hey J, hows your car doing now?

 

IM just starting to wonder if all these "oxygenated fuels aren't the cause of the lean conditions. I do know they kill your mileage.

 

Back to the stock map.. tried adjusting the BOV out and that didn't help boost levels, going to adjust in and if that has no effect I am going to just tear down every coupler and go from square one on checking for leaks.

Might try and pressurize the system if I can figure out a good way to cap off the pipes and cap off the exhaust. Just a lot of guess and check; one of the liberties that comes with saving money and trying to do things yourself I guess.

 

I can only surmise that the dyno wasn't working great that day either. Sorry, Turbomax, g8tor1 if it seemed like a waste of time for you guys. The last time we dynoed there, we did get pretty accurate results (or did we?). My horsepower level was a few ticks below Todd's when he was NA even (except I was missing like 20 lbs. of TQ compared to his results). My A/F wasn't as high.

So it kinda scard me when they showed me those results.

Randy-G, yes it was a sniffer from the tailpipe and not into the cat.

So should I not be worrying about detonation at that high A/F ratio or should I carry on like everything is fine? Maybe I need to go dyno at Titan Motorsports or Central Florida Turbo...

 

try a new dyno...if the results are the same...worry.

 

Okay...I guess you can't d/l info from Zeitronix...just real time data logging. So...I took her around the block and floored it for a few gears. Here is what I look like...

I began to mash the petal and I was at a:

- boost of -2 and a/f of 14.40 and lambda of .98.

- At the moment I hit 100% throttle, I read a boost of 3.8 and a/f of 13.8 and lambda of .94

- At peak boost on the first gear hits 7.0 and a/f of 12.0 and lambda of .82

- Next gear begins at boost of 2.70, a/f of 12.4 and lambda of .84

- Top boost of the next gear is at 7.6 with a/f of 12.10 and lambda of .82

Reviewing the entire run of both gears...I see that my a/f hovers around 12.4 at the beginning of my second gear and goes to about 11.9 at the top RPM. This seems leaner than my CP Race dyno sheet. Can anyone intepret this with the limited info provided.

Of course this was only one quick run. I'll have to bring the laptop with me everywhere I go.

 

Looks like I figured out the problem finally.

My RT cats were both bad. I redynoed and my A/F is now at a normal 13/14. When you shake them, you can hear the metal substrate fragments moving in the cat. Pretty scary stuff. To think I dragged raced my car with these on...yikes!

When I had the RT cats on, my Borla sounded really deep, loud, and overrall bad @$$. The downside was the annoying rasp and whisp noise when deccelerating. I've since switched to crawford cats. No raspy noise here, but I feel that the crawford cats have made my Borla exhaust quieter (which is a good thing and a bad thing).