Great HP Increase, but weird fuel saver problem

[kevinpowertv]

Hey guys,

I have a Magnum 5.7L HEMI.

Installed the 91 tune with CAI and after a little leaning out a spark advance, I was able to pull about 33 HP to the wheels totaling 321 HP. Not bad.

However, I've noticed a slight change in the way the car drives. When cruising, the car goes into fuel saver mode which turns off 4 cylinders from firing. This works fine up until the point I apply any more gas to increase speed which takes the engine out of fuel saver mode. When I apply the gas, the fuel saver mode turns off and the car lurches forward as if something is wrong with the transmission. Maybe its the spark advance?

I'm not super savvy with the mechanics of it all, but I know something doesn't seem right. Anyone else have this problem?

Thanks!

[SRT8Tech]

Ive seen some complaints like that come into my dealer after the wrong oil was put into it. This only happens with the 91CAI tune installed or even with the stock tune?? If you dont use 5w-20 oil weird things happen with the MDS.

[kevinpowertv]

I bought the car CPO from Dodge with 8500 miles and it has just over 9000 now, so I haven't done an oil change. I assume they would use the correct weight?

This does not occur with the stock tune. It only does it with the 91 CAI Diablo tune.

[kevinpowertv]

First and foremost, I guess I need to know if this is damaging the car. Any ideas?

[Chrispy]

I think it's because torque management is reduced in the tune. It affects the feel of the car going in and out of MDS. I dont think it'll hurt anything...

[Mike_Levy]

I assume they would use the correct weight?

Don't assume anything. When the dealer prepped my car, they overfilled the oil.

[kevinpowertv]

I'll check it out. Wont hurt to change the oil anyway.

[fordomatic69]

IT sounds like the dreaded MDS surge.... I had it a wee bit with 91CAI & stock exhaust but it got a little worse when I removed the resonators and installed Blastin' Bobs Fat Pipes.... I think the increased volume (11dB) of the exhaust has emphasized the surge. Won't hurt the tranny.... it is a byproduct of reduced Torque Management and of the increased shift firmness I believe. Before the predator, My Magnum shifted like a Cadillac instead of a Sports Car and MDS engagement and disengagement was quiet and seemless but sometimes you lose a bit of comfort when you are going for performance. I think the guys at Diablosport are doing a good job and if anyone can find a balance between performance and smoothness, it's them. Just my .02 cents

[kevinpowertv]

I had the regular 91 tune in before I installed the CAI and I don't recall it acting this way. I also noticed a bit of lag time in low end torque. I know this because I tried to burn out. I brought the converter up to about 2500 RPM and let it loose, barely burned out. Before, when the car was completely stock and I tried this, I left a 20 yard skid mark. Now it's practically nothing, so there is definately some issues with bottom end torque and power. This may have something to do with why it surges like that since the MDS is only active at low RPM's.

Need some help with this Diablo. Thanks!

[jtfinklea]

I installed a MagnaFlo Exhaust on a 05 300c before using the Predator and the car had (MDS surge) the local dealership said that the factory exhaust was tuned to remove that MDS surge. It was more noticeable after I started using the Predator, did some research and some of the forums said to disable the MDS thur the Predator which I did along with the EGR. No more MDS Surge, but took a hit in the MPG of 2-3 mpg hwy. I like the fact that the car no longer surges and it took away the exhaust drone I was getting with the new exhaust.

[dcram71]

The MDS surge occurred on my 2008 Daytona with no mods other than 93 Perf. (non-CAI) tune. It is not exclusive to 91 CAI or to cars with non-stock exhaust. Disable MDS and it goes away.

[johan]

The surge should be more noticeable in ALL tunes (except stock) due to the fact we reduce torque management and that same logic is used to dampen the MDS kick in, so unfortunately you can not have your cake and eat it too in this case.

[fordomatic69]

I 2nd what johan says.... I was goofing around and put my tune back to stock.... well, what do you know.... no more MDS surge..... and then changed shift firmness only, the MDS surge is just barely noticeable but it has indeed returned so I don't think I would be going too far out on a limb to say that the MDS surge is entirely in the torque management and WILL NOT harm anything on your car. Nice weather is almost here, install a Predator tune, turn off your MDS and drive...