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  #1  
Old 06-11-2013, 12:18 PM
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High Exhaust Backpressure!?!

I was wondering whats everybodys opinion on high exhaust backpressure? Tony is tweaking my tunes for my MTW stage 2 and the lastest tune has backpressure under light throttle. Today backpressure was up to 17-19 while boost was only 2-3 psi. Seems Really high to me... But under WOT boost is at 22 and backpressure was only 31. So I know Im okay under WOT but light throttle seems out of control. Boost also seems low and I'm struggling to get boost higher than 26 on this MTW Stage 2.

The turbo sounds weird also, I just cant seem to find a noise to compare it to. When I put the tune back a different tune it doesn't make this weird noise. I tried to record the noise but you couldn't here it in the video...
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Old 06-11-2013, 12:27 PM
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Tony tunes run with a lower boost# then any I have run. I wouldnt worry to much about the boost numbers as long as the truck is performing. If I am correct your engine is running more efficiently if you can produce more HP with less boost. (someone a little smarter then me may correct that statement) I have not seen boost higher the 25 on his tunes. The noise may be (if it is the same as mine) the vanes on the turbo closing. Watch your VGT% if you are running an CAI you will most definitely hear it more. It sounds like a low growl kinda-of when you let off the throttle. Tony may have installed the Jake Brake option on the tune.
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Old 06-11-2013, 12:41 PM
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No jake brake option installed and VGT cycle % is at 65% and holding steading when I hear the noise...
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Old 06-11-2013, 12:51 PM
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Can you describe the noise at all
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Old 06-11-2013, 12:57 PM
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I wanna say the noise sounds like the whine from a supercharger but deeper sounding...
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Old 06-11-2013, 01:04 PM
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Well for what its worth each tune i run (and I have 12 different ones from 3 tuners Tony, Vivian and Eric from IDP and just contacted Matt from Gear Head today to try his) they all sound different. Some have a more pronounced whine while others sound just like stock. I am sure it just has to do with how each tuner controls the turbo vanes which also effects your back pressure.
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Old 06-11-2013, 01:26 PM
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Is the EBP atmospheric or relative? I see about 19psi atmospheric with 2pis of relative boost. At WOT and loaded I get over 32psi boost and 52psi EBP. If the converter is spinning, I get 28ish psi and 45-50ish EBP with Tony's Extreme. So if you go atmospheric to atmospheric or relative to relative, it seems one of your numbers is way off. Maybe your noise is a leak or your sensor is off on the calibration?
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Old 06-11-2013, 01:27 PM
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If you are reading boost from the obd2 port it will not display correct. Most tunes show a lower boost to keep the vanes closed longer. As for back pressure at wot you want to be as close to 1:1 as possible, in a perfect world, at cruise 2:1 is normal.
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  #9  
Old 06-11-2013, 01:37 PM
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Quote:
Originally Posted by snafu! View Post
If you are reading boost from the obd2 port it will not display correct. Most tunes show a lower boost to keep the vanes closed longer. As for back pressure at wot you want to be as close to 1:1 as possible, in a perfect world, at cruise 2:1 is normal.
2:1 cruising is what I thought was normal. If I put the truck back to the original tune Tony wrote me, backpressure is normal. Just trying to squeeze everthing out of this turbo before I go the dyno in Woodburn Oregon. I think I need to get a mechanical boost gauge to be 100% positive boost is actually low.

With this tune my VGT is 85% at WOT but once it spools up the VGT cycle drops to around 41% in 5th and 6th gear. I'm thinking that I need to lower both numbers for high boost numbers with lower backpressure numbers. I'm waiting to see what Tony has to say, I know he is busy with his family so I don't bug him and just wait for a response.
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  #10  
Old 06-11-2013, 02:48 PM
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Quote:
Originally Posted by twoicebergs View Post
Is the EBP atmospheric or relative? I see about 19psi atmospheric with 2pis of relative boost. At WOT and loaded I get over 32psi boost and 52psi EBP. If the converter is spinning, I get 28ish psi and 45-50ish EBP with Tony's Extreme. So if you go atmospheric to atmospheric or relative to relative, it seems one of your numbers is way off. Maybe your noise is a leak or your sensor is off on the calibration?
What are you using to read turbo boost numbers? Also, the noise goes away once I reprogram with a different tune so it not a leak.
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