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Discussion Starter · #1 ·
got a chance to pick up an MP8 pretty cheap, was wondering if it was worth it to stack on an XRT Pro (no MCC).I've seen mixed reviews on the MP8, some folks say they work well at 50% and under, some folks say theres no difference. On a mostly stock truck, my main objective is MPG's only, not smoke or huge HP/Torque gains.

I've also seen some folks say the fuel rail shim kit is a must with the MP8, and others say they did it without....

Thoughts and input appreciated.
 

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You will need to shim the valve with a pressure box, If you are running older h&s tunes you may not see much difference with the mp8 as the older tunes commanded so much duration that they drained the rail and the pump could not physically keep up. If you are running the newer updates the mp8 will help some as the duration has been pulled back and the mp8 can actually raise the rail pressure since the cp3 is not being maxed out already.
 

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You will need to shim the valve with a pressure box, If you are running older h&s tunes you may not see much difference with the mp8 as the older tunes commanded so much duration that they drained the rail and the pump could not physically keep up. If you are running the newer updates the mp8 will help some as the duration has been pulled back and the mp8 can actually raise the rail pressure since the cp3 is not being maxed out already.
This.^
I'm currently running the newer updated tunes and I run my MP-8 at about 75%. I've noticed that it helps a bit on the low end. Throttle response feels better.
 

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Discussion Starter · #4 ·
irony. The guy who offered me the MP8 is a guy that i'm swapping xrt pro's with. he has the older tunes, i've got the newly updated tunes. Not a fan of the newer ones... So at any rate, no reason to spring for the MP8 running the older tunes then?

Have you noticed any mpg gains with your setup NWRQC?
 

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irony. The guy who offered me the MP8 is a guy that i'm swapping xrt pro's with. he has the older tunes, i've got the newly updated tunes. Not a fan of the newer ones... So at any rate, no reason to spring for the MP8 running the older tunes then?

Have you noticed any mpg gains with your setup NWRQC?
I am not the best judge of added fuel economy since I am chasing a few lost MPG.
http://www.cumminsforum.com/forum/0...eneral-discussion/891258-chasing-few-mpg.html
Honestly I don't believe that I saw much if any increase in fuel economy. My overhead went from 17-18mpg (highway) to 22-24mpg on the same trip, which is a false reading. The reason that I have kept it is because it does increase low end to mid-range performance. To me it's well worth it.
 

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Discussion Starter · #6 ·
well i tried switching tuners with a guy... returned both trucks to stock, and when i went to install his tuner with the older software, i got this:

incompatible version
current tune: 1021
update tune: 1020

It would not let install the older software on my truck. Anybody know what the deal is or seen that before? H&S is killing me with mandatory software upgrade BS. I made a 6 hour roundtrip to swap these tuners and it didn't work....

In the end, i picked up the MP8 since i kept the tune. Does the MP8 need to be run with a modified relief valve shim?
 
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