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Discussion Starter #1
i recently installed magnaflow direct fit catalytic converters on my srt8 challenger 08 I use to average 15.5-16.0 mpg and now I check on my dash and it's saying 11.5 then later on it'll say 9.0 , anyone know why is this happening ?
 

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i recently installed magnaflow direct fit catalytic converters on my srt8 challenger 08 I use to average 15.5-16.0 mpg and now I check on my dash and it's saying 11.5 then later on it'll say 9.0 , anyone know why is this happening ?
If you are not getting a CEL...my first guess would be that you are driving the car more aggressively than normal to see if your mod makes any difference that you can feel. Add to that hot summer time temps....summer formula gas....and good ole ethanol mix in most gas and maybe that explains it. Two things to keep in mind are first a advertised 10% ethanol gas can be a good ways off from being that and the more in the mix the worse the mileage will be....and second...if there was anything wrong the changing the cats job....you would almost shurly get a CEL.
PS....The way I drive my 392 sometimes puts my MPG at close to 10...lol
 

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Discussion Starter #3
If you are not getting a CEL...my first guess would be that you are driving the car more aggressively than normal to see if your mod makes any difference that you can feel. Add to that hot summer time temps....summer formula gas....and good ole ethanol mix in most gas and maybe that explains it. Two things to keep in mind are first a advertised 10% ethanol gas can be a good ways off from being that and the more in the mix the worse the mileage will be....and second...if there was anything wrong the changing the cats job....you would almost shurly get a CEL.
PS....The way I drive my 392 sometimes puts my MPG at close to 10...lol
This is earlier during the day starting her up again , it actually feels better more responsive ! And no check engine light on my car , I use to have p0420 until replaced the cats and o2 sensors aswell and light hasn't turned on yet
 

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This is earlier during the day starting her up again , it actually feels better more responsive ! And no check engine light on my car , I use to have p0420 until replaced the cats and o2 sensors aswell and light hasn't turned on yet
Only way I have ever seen that low is if I hit the reset and let the car sit and idle. The longer the car sits idleing....the lower it will get...and in a pretty good hurry too since it doesn't have the 20 something MPG to average into anymore.
 

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Have you done any manual calculations on your own to ensure the computer's reading is correct? I'd double check that first.
 

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Longing for spring
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Maby your right foot is getting heavier?
(sorry, i could not help it)
 

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"Gin'iro Ryuujin"
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Do you have a predator, Intune, or an OBD II reader? If not take it to AutoZone and they can read what code is being thrown. We need to know what codes are being thrown before we can help.
 

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Discussion Starter #10
Do you have a predator, Intune, or an OBD II reader? If not take it to AutoZone and they can read what code is being thrown. We need to know what codes are being thrown before we can help.
Yea have the Diablo intune , got the code P2098 after new high flow cats and o2 sensors
 

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Dazed & Confused
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Did you put the adapters (spark plug anti-foulers) in the rear O2 ports to get the sensors out of the exhaust stream?
 

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I would not myself. Just checking about the adapters as you would definitely throw codes with the high flows without them. Just based on the P2098 I would check for exhaust leaks on that side or see if you have a vacuum hose off someplace, don't think it's a tuning issue for it.
 

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"Gin'iro Ryuujin"
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Mechanic shop did it for me , should I try and add fuel thru Diablo intune ?
No don't add fuel. Fuel isn't the issue. Assuming you have new sensors, make sure you have no exhaust leaks prior to either O2 sensors. I had a crack in the weld of my headers which let more air in prior to the rear O2 sensor. Drove us crazy until we found it and re-welded the crack. In my case anti-foulers didn't help. Have your mechanic tighten down all the bolts and clamps on your exhaust system where pieces attach to the manifold or where the catalytic converters are connected to the exhaust. Like Joe said it is probably not a tuning issue.
 

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Discussion Starter #16
No don't add fuel. Fuel isn't the issue. Assuming you have new sensors, make sure you have no exhaust leaks prior to either O2 sensors. I had a crack in the weld of my headers which let more air in prior to the rear O2 sensor. Drove us crazy until we found it and re-welded the crack. In my case anti-foulers didn't help. Have your mechanic tighten down all the bolts and clamps on your exhaust system where pieces attach to the manifold or where the catalytic converters are connected to the exhaust. Like Joe said it is probably not a tuning issue.
Ok I'll head to the shop tomorrow morning and have them check it out down there , last night had a enhine light come on P0430 but woked up to Johan's new tune and all day today haven't had a light come on but I'll make sure nuthing leaking or anything tomorrow morning
 
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