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Does anyone know why the sound changes when idling. I have a 07 with MBRP no cat. It will sound like its building up pressure then it lets out and sounds different for a little an does it again. Any one tell me what that is?? Thanks


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That's the vanes in your turbo being cycled at idle so that they don't stick from being idled to long. A lot of trucks do it but mine doesn't as my EGR is completely deleted so it doesn't do it anymore. Kinda wish it did as I like how it sounds when it goes from sounding like a jet getting ready to take off to a deep rumble.
 

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Discussion Starter #3
Ahh cool. Thanks. Had the truck for a year so far and still learning so much.


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That's the vanes in your turbo being cycled at idle so that they don't stick from being idled to long. A lot of trucks do it but mine doesn't as my EGR is completely deleted so it doesn't do it anymore. Kinda wish it did as I like how it sounds when it goes from sounding like a jet getting ready to take off to a deep rumble.
I had not noticed that my truck stopped cycling after I deleted the EGR... Any idea how to trick it into cycling again? I miss it as well!
 

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If you guys reinstall your egr valve and plug it in your turbo will cycle as it did before your delete. Im all deleted i just left the egr valve in my intake and my turbo cycles at idle. When i had the block off plate in my turbo no longer cycled. so just throw your valve in and plug it in if you dont mind it sitting in your intake.
 

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unless you have an 04 or 03.. My truck(04) cycles and I have a full egr delete with egr not installed
 

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unless you have an 04 or 03.. My truck(04) cycles and I have a full egr delete with egr not installed
My turbo stopped cycling with my egr completly gone my trucks an 03.... It will cycle with the valve in place.
 

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My 03 will only do it on the stock tune, pretty sure it didn't matter if the valve was plugged in or not, but with the tunes the egr is turned off so it dosnt do it. So I guess if you have the 03-04 that won't throw a cel, turn the egr back on in the tune even if its deleted.
My canned sct tunes give me the option to turn egr on or off, so maybe I'll try turning it on even though its all removed from the truck and see what happens.

One thing I did notice while testing my truck when the hpop went out, my Mac tools scanner wouldn't finish the koer self test without the egr plugged in.
 

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I know i've tried what your describing portcity with a canned tune. If I had no egr valve in place with egr on in my tune I had no vain cycle . With my egr valve in place, and egr option ON in my tune the vains would cycle. With my egr valve still in place and egr option OFF in my tune I have no cycle. Every truck is different i guess, thats just my experience.
 

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I know i've tried what your describing portcity with a canned tune. If I had no egr valve in place with egr on in my tune I had no vain cycle . With my egr valve in place, and egr option ON in my tune the vains would cycle. With my egr valve still in place and egr option OFF in my tune I have no cycle. Every truck is different i guess, thats just my experience.
And mine could be the same way, I really don't remember. But if it does have to be plugged in and a person REALLY wanted the cycle without the valve they could prolly ohm the valve and plug in a resistor with the same value to trick the PCM.
 

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My experience with the EGR valve unplugged is no vane cycle (early 04), myself and others who have had this happen, have the VXAP2 strategy.

With the EGR unplugged in any tune (stock, canned,custom) would not allow the vanes to cycle.

The PCM needs to see the following conditions.

The PCM commands the variable geometry turbo actuator duty cycle from 15% to 85% in a step pattern to help the turbo vanes achieve full movement. Vane sweep occurs when the following conditions are present:

The vehicle is stopped.
The EGR is commanded off.
The engine speed is less than 1,160 RPM.
The engine oil temperature is greater than a calibrated value.
Vane sweep repeats approximately every hour if the previous conditions still exist. Vane sweep may occur during scan tool commanded test functions.


Even with the canned tunes and custom tunes set to EGR off, I got no vane sweep when unplugged. I believe it's because the PCM don't see a return signal from a unplugged EGR valve.


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Or you can have your tune writer write the file with the vane sweep at idle.
Yea they may be able to do that, I'm not sure how much control the tuning process has over it.

Prolly at least some because The canned performance tune on my 5015 spools the the turbo when you let off the pedal (to assist with stoping I think) but it sure sounds cool lol.
 

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Rich my buddy Matt has an 03 6.0 with all emissions equipment still intact and when his is idling it will idle for say 30-45 seconds where you can hear the whistle of the turbo than after that it goes to a deep rumble for 30-45 seconds or so and then the vanes cycle again and the turbo starts spooling again.
 

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Yea I was going to say that too, when stock mine goes up and down several times while sitting in a drive thru
 

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Rich my buddy Matt has an 03 6.0 with all emissions equipment still intact and when his is idling it will idle for say 30-45 seconds where you can hear the whistle of the turbo than after that it goes to a deep rumble for 30-45 seconds or so and then the vanes cycle again and the turbo starts spooling again.
Is it a VXAP2 strategy? Does he have the EGR valve unplugged?


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Rich my buddy Matt has an 03 6.0 with all emissions equipment still intact and when his is idling it will idle for say 30-45 seconds where you can hear the whistle of the turbo than after that it goes to a deep rumble for 30-45 seconds or so and then the vanes cycle again and the turbo starts spooling again.
This is what mine does with egr plugged in only and i'm a vxap1. People give me the wtf is happening look at stop lights while they stare at my exhaust lol. pshhhhh and were ready for lift off pshhhh lmao.
 

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This is what mine does with egr plugged in only and i'm a vxap1. People give me the wtf is happening look at stop lights while they stare at my exhaust lol. pshhhhh and were ready for lift off pshhhh lmao.
So you have the VXAP1 strategy, and when your EGR valve is unplugged, no vane cycle. Interesting! So this may mean that the VXAP1 and VXAP2 strategies need the EGR valve plugged in for vane cycle at idle.


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I don't know what strategy his is Rich. I do know it does cycle very frequently and love the sound of it just wish mine still did it, but I don't have an egr valve anymore so I guess no more cycling for me as I'm not about to spend $150 on an egr valve for that.
 
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