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Discussion Starter #1 (Edited)
whats MDS, best on or off for performance, why or why not? or does it not effect performance?

thanks, one more question anyone know about WOT fuel settings?

WOT Fuel 1k-3.8k (1,000’s rpm), WOT Fuel 4k-4.8k, and WOT Fuel 5k-7k. You are offered a bar graph with adjustments of +/- 20% in .5% increments.

which is best setup for 91 octance and only an aftermarket exhuast system?
 

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MDS is the ability for your car to drop to 4 cylinders under light load and highway cruising.
Doesnt really effect performance, saves gas
 

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mds is the mode your car goes into where it only runs 4 cylinders.

the reason it is an option on predator is if you have a non-mds cam and wanna disable mds so your car doesnt freak out when it cant cycle into MDS.

or if oyu have loud exhaust and the drone from MDS is mind numbing.

i dont think it will effect performance.. there may be a SLIGHT SLIGHT SLIGHT delay in kicking back into 8 cylcinders. but MDS only activates in "D" so if your wanting performance... you should be shifting down and shouldnt be in "D" so it shouldnt matter.
 

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Discussion Starter #4
thanks, one more question anyone know about WOT fuel settings?

WOT Fuel 1k-3.8k (1,000’s rpm), WOT Fuel 4k-4.8k, and WOT Fuel 5k-7k. You are offered a bar graph with adjustments of +/- 20% in .5% increments.

which is best setup for 91 octance and only an aftermarket exhuast system?
 

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I agree with RT racer in the definition of MDS, but if I had to choose which was better for performance, Id probably say having MDS off would be better just because you dont have that split second lag where the car kicks from 4 cylinders to 8 cylinders, but rather it is just ready to go on all 8 at all times. Otherwise, if im not mistaken there really isnt much difference of it being on or off.

In my opinion, I think its better to leave it on because the benefits of getting that extra mileage from 4 cylinders far outweighs the advantage of having the very minimal split second advantage of being on 8 cylinders at all times.

Keep in mind that if you activate autostick, MDS is disabled and cannot engage until autostick is is disengaged, so this is essentially the same thing as disabling MDS on the predator.
 

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^^^ any1 know about WOT Fuel settings?
Without a dyno and wideband 02 sensor for setting A/F ratio you are just stabbing in the dark unless the car is really rich or really lean and you can tell by smell. You are safest just using the canned tune until you can get a CMR tune on a dyno.
 

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I

In my opinion, I think its better to leave it on because the benefits of getting that extra mileage from 4 cylinders far outweighs the advantage of having the very minimal split second advantage of being on 8 cylinders at all times.

Keep in mind that if you activate autostick, MDS is disabled and cannot engage until autostick is is disengaged, so this is essentially the same thing as disabling MDS on the predator.
You don't get much benefit of MDS in city driving, only highway. So, if you do mostly highway driving, I would leave it. If you do mostly city driving, I say disable it, especially if you have a cat back, like myself, and enable it on big trips.

True that MDS does disable in Autostick...but who the heck wants to drive around town in autostick all day....not me! Especially if you have high shift points....you forget it's in Autostick, and you can bring your car up to high RPM's by mistake, like I tend to do.

MDS disable is an awesome feature of the Diablo....
- Mark
 

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You don't get much benefit of MDS in city driving, only highway.
Not entirely true... for example, a 10 minute stretch of 2 lane boulevard between my parents' house and the highway is usually driven at 35mph. Even factoring in the occasional stoplight and the quick (but not WOT) acceleration to get back up to that cruising speed, I've had my EVIC show 27.x MPG by the time I hit the highway.

At those speeds the Charger's aero losses are minimal, the RPMs are hovering around 1400 with the TCC partially unlocked and MDS on... probably close to being the most fuel efficient you can get with this car. Some acceleration can even be had at those speeds with careful attention to the pedal position.
 

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thanks, one more question anyone know about WOT fuel settings?

WOT Fuel 1k-3.8k (1,000’s rpm), WOT Fuel 4k-4.8k, and WOT Fuel 5k-7k. You are offered a bar graph with adjustments of +/- 20% in .5% increments.

which is best setup for 91 octance and only an aftermarket exhuast system?
The WOT fuel parameters let you adjust the Air/Fuel ratio in different RPM ranges. As Nightops posted, you shouldn't mess with these unless you have an accurate way to measure the results of your adjustments. Getting too lean can be (and has been shown to be) very bad.

As for the best tune to choose, either the 91 tune or 91 CAI tune will be best for you. You can try them both but will probably want the non-CAI version since you haven't changed your air intake.
 

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please dont mess with your a/f ratio's without a certified tuner and dyno.
x2 unless you have money TO BURN, since you could potentially do VERY bad things to your engine, ie, buy a new one.
 

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I was recently reading some literature on PCM tuning (A/F ratios, particularly) and I discovered something interesting about GM tuning that might or might not apply to Chargers.

Those familiar with the LT1 engine will be familiar with the huge dump of extra fuel that happens at the 4500-ish RPM range (not sure if the LS1 does it as well... perhaps not as noticeably due to the more complex PCM). Many newbie tuners just even out the fuel flow at this transition point and get a few MPH in the 1/4 for free.

Turns out that this fuel dump is most likely there purposely to cool down the cat(s) with a richer (less hot) mixture! Seems engineers thought that extended WOT with normal mixtures would heat the converter(s) too much and this extra fuel dump was meant to address this risk.

Whoever's tuning Hemis using these 3 fuel ranges might want to take that into account, if it looks obvious that calibrations were engineered to dump rich at a certain range.
 
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