Safe AFR's

Discussion in 'General Discussion' started by Velociabstract, Apr 30, 2011.

  1. Velociabstract

    Velociabstract Full Access Member

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    I have a SRT-6 ..... and a 300C which is why I belong to this forum, and I have great respect for the experience and knowledge of the members here.

    I race my Crossfire and got a tune recently. The original tune was rich, 10.8 rich and I lost power under the curve. The tuner adjusted the tune for "my race conditions" which is to say IAT's from 135º to 175º. Water temps reaching a maximum of 235º and an ambient temperature of 100º. I race close to sea level and see maximum boost of 17 PSI. Stock is around 14.5. I sent a dashdaq log file for the tuner to study before the adjustment. The new tune made more power but the AFR's at WOT now range from 13 to 12.7. The dyno was done on a cool rainy day with the car cold which is not how the car will be at the track or what it was tuned for, but I had no choice. As the car got hotter the AFR's got richer and the HP higher but I didn't see track IAT's or water temps on the dyno. I don't think they got over 110º IAT and 205º. The dyno used a tailpipe sniffer and is a mustang dyno. I sent the dyno sheet to the tuner and he thinks it's perfect and when the car is up to real track temperature it should be around 12.3. I use the car on the street but never run it hard. I save it for the track. What do you guys think? Should I be sh!tting in my pants? Opinions? I requested a tune for race conditions so I may be responsible. There was no sign of detonation and the power and afr curve steady.

    Les
     

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    Last edited: Apr 30, 2011
  2. TNCHARGER

    TNCHARGER Moderator

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    I am not versed well regarding the Crossfire but any street/track engine I have dealt with that has a blower should be staying around 11.5 - 12.0 at WOT with as much boost as you mentioned.
     
  3. 1bad4dr

    1bad4dr Mr. Meany

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    I'm Larry on this one.
     
  4. cmn1

    cmn1 SRT and SVT

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    So as long as you post on this thread, I will call you Larry. :bang:
     
  5. TNCHARGER

    TNCHARGER Moderator

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    And people made fun of me for mixing up names....I do know who I am..LMAO...:D
     
  6. 1bad4dr

    1bad4dr Mr. Meany

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    lololol oops. Conjunction junction, what's your function?
    yea, that's OLD age, buddy. And apparently I have it bad.
     
  7. cmn1

    cmn1 SRT and SVT

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    It's Ok, Larry it happens to the best of us.
     
  8. Velociabstract

    Velociabstract Full Access Member

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    Does anyone know how much leaner the tailpipe sniffer is than a wide band? My tuner claims when the tailpipe sniffer says 13 it's actually closer to 12.5. (I deleted the cats BTW) The tuner also tells me the ECU on my car richens up the mixture based on the IAT's so the AFR will be perfect at race temperature. I have a Zeitronix that's going in the car this week so I can see true AFR's. Any info, ego ..... etc?

    Larry (Les)
     
  9. Dookie

    Dookie Foe twenny sics

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    With cats gone, it should read pretty close, but optimal is as close to the header as you can get.

    Who is tuning it? What is he basing his statement about increased IAT's richening up the AFR. Logic tells me he's correct, it should in theory, but I would want to know for sure.

    Seems lean to me at 17PSI, 110 degree IAT's, made good power though, and torque. I would think 12.0-12.3 is where you want to see it.
    You said no knock, were the sensors desensitized any/all the way off?

    Maybe a second tune for those condition's for the street.
     
  10. Velociabstract

    Velociabstract Full Access Member

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    The car is being remote tuned by Eurocharged of Houston Texas. They have experience with the MB's and SRT-6's and I'm trusting ..... but worried at the same time. I don't know if they can desensitize the knock sensors or turn them off. I believe the statement about the IAT's, I have no clue how much it fattens up the AFR's. So thats why I'm so nervous.

    I showed the graph to the F/I tuner that was present (mostly Mustangs ... he was tuning a 2011 with a Vortec, 550 BTW) at the dyno and he didn't recognize any signs of knock on it. He said it was perfect for NA but for F/I it was on the edge in his opinion.

    You gave me some good questions to ask the tuner. How much does it fatten the AFR and are the knock sensors off. I'll remind them that I have no cats, just in case they didn't take it into account when doing the maps.

    Les
     
  11. Quick

    Quick Mgmt. - I can't help you

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    Yes, you can "desensitize" the knock sensors on the v8's. I expect you can do the same on the 6's. They change the thresholds and/or scaling of the the signal from the sensors.

    I would not expect before and after cat AFR to differ by much more than 0.2. The main effect the cats have on reading AFR is to "dampen" changes. Kind of like smoothing a graph line. Yes, the tailpipe sensor (if it reads differently) will read leaner than before the cats. If you don't have cats then it should read the same (assuming you don't have any exhaust leaks and there are no flames coming out the back).

    When you get that Zeitronix in there you can run the signal through a statistics calculator on the DashDAQ to smooth out the closed loop display :)
     
  12. LegMaker

    LegMaker LMI - LegMakerIntakes

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    i would rather see afr of 11.5 - 11.8 if it was my car. i run 11 - 13 psi with my set up on an LX car, but boost is boost...... no matter what the condition, 11.5 - 11.8 would be more comforting to me, especially if i am beating on the car.
     
  13. Velociabstract

    Velociabstract Full Access Member

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    The tuner emailed me that from 12.8 to 12.3 is where the AFR's should be for a SRT-6 and that the ECU will richen the mixture from .3 to .6 AFR depending on how hot the IAT's are. They left the knock sensors untouched. I'll be putting in some 100 octane at the track for piece of mind. Thanks everyone and I'll let you know how it goes.

    Les
     
  14. Velociabstract

    Velociabstract Full Access Member

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    Today I installed the Zietronix wide band. Let's see what the AFR's do when the car is at racing temperature. I'll make a data log and send it to the tuner and see what he thinks.

    Les
     
  15. Velociabstract

    Velociabstract Full Access Member

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    Your not going to believe this. I took the car out for a long drive to get it hot ....... it never got real hot. I didn't see less than 13.3 on the Dashdaq AFR display while getting on it. Then I switched the display to a different gauge cluster to log all the variables I wanted. There's no way to read the multi gauge screen while driving. (It logs what's showing on the screen and has a maximum of 6 signals) So I logged the IAT's, ECT's, throttle position, Spark advance, Vehicle speed and AFR's. Then I did a 30 to 70 pull close to home. After getting home I was in the process of composing an email to the tuner telling him how I'd rather be safe than sorry and to please redo the tune. Before sending it I looked at the data log. When the IAT's passed 115º the AFR's dropped like a rock. They went to the low 11's. At part throttle with IAT's lower than 115º the AFR was at 14.7. Over 115º and part throttle was in the mid 12's. I think I'm going to sleep tonight for the first time since getting the tune. It looks like it's all in the IAT's. I just have to be careful until they get around 120º. I was hoping being supercharged from the factory would include some fail safes that I didn't know about. Looks like I'm good to go.

    Les
     
  16. Quick

    Quick Mgmt. - I can't help you

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    Wow, interesting tune. Good to know. Maybe never a problem for you but you're not going to be able to race in the cold... I guess it doesn't snow in Puerto Rico :)

    On the DashDAQ you should be able to configure (4, or maybe 6?) logged parameters that are "global". They get logged in addition to whatever screen you're logging at the time.
     
  17. Velociabstract

    Velociabstract Full Access Member

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    I'll have to investigate some more. I saw a classic screen that had more than 6 but there's no way to read any of them while driving. I have a huge IAT gauge in the middle and the other perameters on the sides. I'm stuck with what came with it. (Mac owner .... no bootcamp) Otherwise I could download a bunch of neat skins for it. And the new dataloging upgrade.

    The tuner told me it would richen up. And he had a data log from the track. I'm just glad to discover for myself that he knows what he's doing. You never know for sure in the beginning who you can trust. I've learned the hard way how many cheerleaders are out there that just cheer and don't know squat. I'm going to be real careful on the street and for the first lap at the track. Of course I'll continue to log to find out all I can. Who knows, he may have to lean it out some more.

    Les