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Discussion Starter #1
I have a 2007 SXT Charger with the following bolt on mods:

CAI - K&N
Catch can - speedlogix
71mm Throttle body - Speedlogix
JBL Short Headers
Borla Cat Back Exhaust system - dual
Diablo Predator 91 octane tune.

The top end is great. About 3000 rpm and up it pulls hard. But the bottom end seems to have suffered since the headers/exhaust and throttle body have been installed.
Since I have a predator and can adjust timing and I think fuel ratio I wanted to ask if anyone with experience with this setup (or close to it) would have some ideas I could try playing with to see if it helps my lower end acceleration.
The exhaust tips are black inside so I assume its running a little rich. What would be a safe parameter to adjust a little and try out?

Jeff
 

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From my limited experience so far with my 2010 SXT I can tell you the following.

The CAI, 71mm throttle body more than likely have messed with your fuel/air ratio and is probably making your car run rich. Which in itself is why your low end is suffering and your high end is pulling hard.

I had my SXT dyno'd stock, 168 rwhp, (I believe, I have not posted everything yet, waiting for my last tune session and dyno to post all my results) at right around 75,000 miles.

First thing I did put on my AEM CAI. Re-dyno'd and actually lost hp (156 rwhp or so I believe) and performance (could tell by just driving it). The tuner at the dyno shop said my fuel/air ratio had changed and was running too rich from the stock run.

So I ran out and bought a Diablo Intune, installed a Dynomax VT muffler (mine was shot), and Blastin Bob's 14 db reso kit exhaust.

Took it back to the dnyo shop and had it tuned (to correct the fuel/air ratio using the Intune) and then ran another dyno run. Now it did 197.5 rwhp. Let me tell you it was fun to drive. I had the throttle set to +1.5 in the Intune and my car pulled hard from start all the way up to red line. I bumped the throttle in the Intune up to +5, and could hardly keep the tires from spinning every time I took off.

Next in the series. I ordered BND (brians) oil and filter, and aces IV gas additive. Changed the oil & filter and added the aces IV to my next fill up. I did nothing else but those 2 things. Ran 3/4 of a tank of gas and my car started acting up after the fast idle shut off upon start up. It would not idle right and would idle up and down enough that you could clearly hear it from the exhaust.

After 2 days of this it started throwing p050b code. (which is idle failure) So after talking to Brian and him explaining what the aces IV is suppose to do to cleaning and lubricating the engine, I re-installed the stock tune and per Brian's advice am running 3 tank fulls of gas through my car before having it tuned and dyno'd again. I just filled up the 3rd tank yesterday, so when I am done with this tank I am going back to the dyno shop to have it re-tuned to correct the fuel/air ratio again and to see if I gained any rwhp.

It will be interesting to see if I did gain any rwhp, because all I have done is oil & filter change and add aces IV, nothing else but driving my car. I did order the rear end lubricant yesterday from Brian, but will not put it in till after I dyno my car again. Do not want to scue any of the results.

If your tuner can adjust the fuel/air ratio, I believe mine ran the best at around 12.5 to 12.8 in that range at the dyno shop. My tips also got coated with soot from un-burnt fuel before I had my fuel/air ratio corrected. Then sooted up again after the idle incident, that is part of how I new something was off.

Sorry about the long winded response, hope some of this at least helps.

Just as a side note, I was going to install the 71mm throttle body on my Charger also, but after research found out that it really won't make a difference if you haven't done something to the internal of your engine like a cam to increase air flow. I might just for giggles add the 71mm throttle to my car after this next dyno and then re-dyno it again to see if the 71mm throttle does make a difference or not. Now I am kinda curious.
 

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Discussion Starter #3
When you say it ran best at a 12.5 to 12.8 fuel mixture range does that mean it is leaned out 12.5%?
My predator can adjust the fuel mixture in three rpm ranges but it has a slider that either leans or enriches by percentage.
I leaned the two lower rpm ranges out by 3% to test and will drive it after work to see. Is there any way to monitor the engine to insure it is not leaned out too much?
 

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The shop I took it to had it hooked up to their computer, sorry I can not answer that question.
 

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I have looked around for a tool to use for fuel/air ratio adjustments, but have not found one that seems to work yet.
 

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Sounds like the only really other thing left, and it would help. Is cams. Or heads and cams. But recently on Inertia's website they have taken down our 3.5 mods :/ Right when i have money to pull the trigger on some cams
 

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Get a dyno tune.

Guessing at what settings you need is like shooting straight up in the air trying to shoot something ten feet from you. You might hit it, miss it, or blow something up that was important to you.
 

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To look at AFR you'll want to use a wideband AFR sensor and Gauge.
Essentially you add another oxygen sensor behind the cat and hook it up to a sensor like the Innnovate LC1. You take the outputs of that and hook it up to a guage like Innovate sells or an AeroForce interceptor gauge and you can monitor your AFR.

I agree with Jonny though - go get a tune done.

You might consider changing out your rear gears to something shorter like a 3.55 or 3.73. Not sure what stock in the 3.5s.
 

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When you say it ran best at a 12.5 to 12.8 fuel mixture range does that mean it is leaned out 12.5%?
My predator can adjust the fuel mixture in three rpm ranges but it has a slider that either leans or enriches by percentage.
I leaned the two lower rpm ranges out by 3% to test and will drive it after work to see. Is there any way to monitor the engine to insure it is not leaned out too much?
Typically the best air to fuel ratio is 14.7 parts of air to 1 part of fuel or 14.7 to 1

So what he was saying is that 12.5 to 12.8 parts of air to 1 part of fuel was the best for him.

To make power, you have to utilize the BTU value of the fuel and turn it from potential energy to kinetic energy or work energy. This is where the people like Bake74 are saying about using ACES IV in the gasoline to produce more hp and torque.

In a 3.5L SOHC Polyhemi V6 like what you have, it is not uncommon to see 5 to 8 hp gains with ACES IV. R/T cars have seen 8 to 13 hp anyway. My SRT8 saw 19 hp and 31 ftlbs but that was with our HP Gold coolant, our engine oil with filter and the ACES IV combined.

Hopefully this helps you realize it wasn't 12.8% fuel trim.;)

Regards,
Brian
BND Automotive LLC:driving:
440-821-9040
www.bndautomotive.com
 

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Typically the best air to fuel ratio is 14.7 parts of air to 1 part of fuel or 14.7 to 1

So what he was saying is that 12.5 to 12.8 parts of air to 1 part of fuel was the best for him.

To make power, you have to utilize the BTU value of the fuel and turn it from potential energy to kinetic energy or work energy. This is where the people like Bake74 are saying about using ACES IV in the gasoline to produce more hp and torque.

In a 3.5L SOHC Polyhemi V6 like what you have, it is not uncommon to see 5 to 8 hp gains with ACES IV. R/T cars have seen 8 to 13 hp anyway. My SRT8 saw 19 hp and 31 ftlbs but that was with our HP Gold coolant, our engine oil with filter and the ACES IV combined.

Hopefully this helps you realize it wasn't 12.8% fuel trim.;)

Regards,
Brian
BND Automotive LLC:driving:
440-821-9040
www.bndautomotive.com
14.7 is best for part throttle. The computer won't let you run anything else. You run that at WOT and you'll melt the motor. 12.5-12.8 is pretty standard for WOT on an N/A car not just "what worked best for him":notallthere:
 

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14.7 is best for part throttle. The computer won't let you run anything else. You run that at WOT and you'll melt the motor. 12.5-12.8 is pretty standard for WOT on an N/A car not just "what worked best for him":notallthere:
Agreed! I was simply describing what he was looking at as he was talking about 12.8%.

Yes, a 14.7 to 1 under load would burn up the engine and the heads especially.

Regards,
Brian
BND Automotive LLC:driving:
440-821-9040
www.bndautomotive.com
 

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RWD 3.5L 5 speed is 2.87
2006 - 2010 Chargers SXT have the 198RII rear axle. (rear independent iron)

Taken out of the service manual. "The 198 axle is available only in all-wheel-drive (AWD) models, and in V-6 engine-equipped rear-wheel-drive (RWD)
models, and is available in three gear ratios: 3.07 3.64 & 3.90:1."
 

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14.7 is best for part throttle. The computer won't let you run anything else. You run that at WOT and you'll melt the motor. 12.5-12.8 is pretty standard for WOT on an N/A car not just "what worked best for him":notallthere:

"Agreed! I was simply describing what he was looking at as he was talking about 12.8%.

Yes, a 14.7 to 1 under load would burn up the engine and the heads especially.

Regards,
Brian
BND Automotive LLC"

I guess I could have been more clear. This was on a dyno's machine with a person who tunes vehicles doing the tunning. I was not doing anything but watching.

They told me at the end that my car produced the best HP and torque at around 12.5 to 12.8 A/f ratio on the dyno.

The guy at the shop used my Intune to adjust my A/F ratio, so I can not tell you how or what he did either as far as that goes.
 
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