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Low boost/aftermarket boost tubes (long post)

1476 Views 7 Replies 5 Participants Last post by  krywanczyk
I'm hoping someone can help. I'm chasing a low boost issue. Truck runs fine, no smoke (I'm running my jr on the 70hp setting). Last week I replaced the air and fuel filter (it was about time anyway) and yesterday I cleaned the MAP sensor. It had a slight coating of soot on the orange sensor in it which is surprising since I am fully deleted. I cleaned it off with some map sensor cleaner and no change. When in 5th gear at 55 mph (1600 rpms) I go to wot the boost builds normally until about 8-10psi then stays there. I did it a few times and it does the same thing every time. It runs fine but that can't be all its pushing out.
After I deleted I stopped using my ebrake all the time (I started doing this again thinking it might loosen up any stuck vanes (no codes at all) I even checked with my JR. I've gone around and inspected every clamp and did find some of them loose and inspected the tubes best I can with an inspection mirror. I've also changed tunes from SW1 - SW2 and back with no luck. I ran SW3 for a bit but never at wot to compare.
My plan now is to pull of the two tubes (passenger and driver) side when I get some time to look at them closer.

Questions - is it possible to check for leaks at idle or high idle? My boost gauge never shows anything until ~2k rpms unless I'm getting on it then it will start to show at 1500ish. Is this normal?

If it is the tubes, any recommendation for replacement? I'm looking at a set of Pusher right now. I read to stay away from MBRP because of the boots they use.

Any other recommendations? I've been searching for the last 4 days which is how I started with replacing the air/fuel filter and cleaned the MAP sensor but I'm at the point to start tearing the truck apart to find this leak. BTW I also called ISSPRO and talked to them to make sure I had the right parts, I do.

If the turbo was only pushing 10psi out I would think I'd get a code??

Sorry for the long post but I'm stumped.
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Does it smoke like a train? If you are truly only making 10lbs it should pour black smoke horribly. If you are not making smoke then I'd say you have a gauge problem.
Does it smoke like a train? If you are truly only making 10lbs it should pour black smoke horribly. If you are not making smoke then I'd say you have a gauge problem.
Not going to be the case with the 6.7 it restricts too much fuel before it sees boost.

How hard does it pull is it pretty slow feeling? At 10psi it should have a hard time getting out of its own way at 75mph.

If it pulls really hard like a tuned truck should it could be a bad gauge.
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No smoke at all, even when I get on it. I can pull past my brother in laws F350 with the 6.0 (stock) same with my other friend with 5.9 cummins (stock) no problem getting past them. The truck runs good. Guess I'll look into getting another sensor???

Also, if it was putting out low boost at wot wouldn't it throw a code?
When my 2nd gen. truck was new, it had 180HP with an automatic. They told me then that a pound of boost equaled about 10 HP. And at WOT, I could get 18lbs of boost, which was about right. I later made some changes, and it delivered 305 HP at the rear wheels on a floor dyno, and was making 32 lbs of boost, again about what it should using the above rule of thumb. Is it any different with the newer trucks? Have a '14 on order, what should I see with it?
im makin 433 hp with 33-34 lbs. of boost....
I think I figured it out. They sent me the wrong boost sensor. Last number should end in a "1" and mine ends with a "3" and according to ISSPRO that sensor will only show about 1/4 of the pressure so it looks like I may actually be pushing out 32 PSI at wot. I'm good with that from my stock turbo. I should have it in a few days. Hopefully this is the fix. Thanks to those who replied.
I put the new sensor in tonight and she works great! I can easily hit 35psi on the boost gauge now (I wont be doing that too much) and I thought I had a boost leak. Been chasing this problem for at least 2 months and the whole time it was the wrong sensor. At least I finally got it.
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