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MVision

Fix for low power at low rpm

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I've got a 2004 Vision with the 427. Has no power below 1400 rpm. It kicks in at 1400 and pulls great.Been reading on here and it seems to be typical for this engine.

Truck has a recent inframe. New injectors. Had Mack update software including the step 12 b upgrade that has been mentioned on here. Still is sluggish on the low end.

I talked to Rochester about their injectors. Says they will give me more power. From talking to them I'm just not sure if they would improve the low end. Don't really need more power on the top end. Also asked about their turbos. Said they can't do anything with the variable rate turbos. I would love to hang a big non variable turbo on this engine.

So I guess I'm asking if I have any options to fix the lack of low end?

Injectors?

Turbo?

Aftermarket ECM tuning/power boxes?

A mechanical issue that can be repaired?

Other?

Thanks in advance. The wealth of information on this site is amazing.

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I have an 01 CX 427 that is sluggish down low as well. Have tried a few things with mixed results. Did 100 HP tune on ecm first. It did make a diff down low but was like throttle was way to sensitive to control at lower RPM. Then added Rochester stage 2 injectors and performance turbo. That made the biggest diff but caused problems under hard pull. Malfunction light would come on and would cut power intermittently until the pull was over. This turned out to be a erroneous timing signal due to excessive crank twisting. So I reflashed Ecm back to stock and solved that. Truck still pulls way better than stock and not as sluggish down low but still not a low end grunter like a cat. I'm thinking next step is cam advance and higher capacity radiator. If I had your model I would seriously consider deleting the egr and then going with the injectors and turbo like I have. My truck pulls very well for a 12 liter and has averaged 7.3 mpg for the last 2 quarters. I have a 13 SPD and have found that shifting up at 16 to 1650 gives me the best performance. That drops me back around 14 and it will pick right back up and go.

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Did you just get new injectors or new unit pumps as well. Unit pumps can be fairly problematic at higher mileages due to under fueling. However, you can't really test individual unit pumps. If they're original and you're experiencing low power, especially at low end, I'd say replace them first.

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I have an 01 CX 427 that is sluggish down low as well. Have tried a few things with mixed results. Did 100 HP tune on ecm first. It did make a diff down low but was like throttle was way to sensitive to control at lower RPM. Then added Rochester stage 2 injectors and performance turbo. That made the biggest diff but caused problems under hard pull. Malfunction light would come on and would cut power intermittently until the pull was over. This turned out to be a erroneous timing signal due to excessive crank twisting. So I reflashed Ecm back to stock and solved that. Truck still pulls way better than stock and not as sluggish down low but still not a low end grunter like a cat. I'm thinking next step is cam advance and higher capacity radiator. If I had your model I would seriously consider deleting the egr and then going with the injectors and turbo like I have. My truck pulls very well for a 12 liter and has averaged 7.3 mpg for the last 2 quarters. I have a 13 SPD and have found that shifting up at 16 to 1650 gives me the best performance. That drops me back around 14 and it will pick right back up and go.

Thanks Refined Trucker. Good to hear real world experience.

Since your from Illinois also, who did you get to do the ECM flash? And can they delete the egr? Deleting a mack egr seems like a top secret mission that no one is allowed to talk about. There is info on how delete other engine manufacturers egr all over the internet. Hundreds of vendors offering the service. When I call some of those vendors and ask if they do Mack's I usually get shot down. What are some options?

Will a Rochester turbo even fit on my engine? What do I do with all the variable turbo stuff? Can I remove it without tripping a lightening bolt on the dash?

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MVision Heavy Diesel tuner did my ecm tune. He is in NW IL. Just shipped ecm to him and it's a one day turn around. My Mack dealer reflashed it back to stock. I have considered sending back to the tuner for maybe say a 50 horse tune but haven't decided if its worth it or not. Once you have him tune it he will retune if needs for no charge other than shipping cost. I think he might offer delete but can't remember. You can Google Heavy Diesel Tuner he has web site. There are some others that come up now when you Google Mack egr delete but I know nothing about them. If you get a delete from one of them it should include changes in the ecm tuning that allow you to run a normal turbo without any codes or trouble. At least the guys I know that have done their ISX's that was the case. Might also call Trent the diesel Dr. in Effingham I have heard he can do some Mack stuff now. He has done quite a bit of tuning on trucks where I'm leased with good results but these have all been Detroit Cat or Cummins. His # is 217 343 3154

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FWIW...Most sites do not mention emissions equipment delete because it is against the law to remove/tamper/defeat the equipment. But as I mentioned in another thread...why is it okay for the "wanta be" hotshot pickups to remove the devices and blow solid black smoke? And not okay for HD trucks?

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I have a 2007 that was originally a 427. This was a dud when I first bought it,so I decided to have it turned into a 460P from the Mack dealer. It helped but it was a bitch to shift bc of the egr. So I sent the ecm to Heavy Duty Diesel Tune to have the egr deleted and turned up 100 hp. The truck was so much easier to shift but my torque was flat, I liked the 460P Tune better. So then I replaced all my unit pumps and put stage 2 injectors from Rochester in. Wow! What a difference it blows some smoke and has instant power. Keep in mind you need to have someone program your unit pumps to the ecm so the truck will run smoother.

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Make sure you have at least 60 psi of fuel to your unit pumps, sometimes the check valve could be weak. Also when the dealer inputs the serial numbers for the unit pumps make sure they calibrate the foot throttle.

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Try a pressure regulator on the intake manifold in front of the boost sensor. Set it at 25 psi. This should help with low end and is a cheap way to gain low end horse power.

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