7.3 boost
Post Fiend
Joined: Feb 2006
Posts: 11,892
Likes: 2
From: Middle Tennessee
I believe as high as 24psi before the pcm will defuel but that does not make it quality boost. As for chipped, you can fool the system into thinking there's less psi, but that just aggravates the nonquality boost to a higher level.
Post Fiend
Joined: Jun 2004
Posts: 9,293
Likes: 10
From: Parker, CO
Stock I was putting up 19psi unloaded. With my DP-Tuner on 40 setting I've hit 23#'s towing a trailer uphill, 80 setting I've hit 27#'s, and the 120 setting I've hit 31 once, just to say I could. Right now I've set my wastegate to limit my boost to 26#'s. I just don't feel like destroying my turbo.
Going over 25#'s on a stock turbo really doesn't do much good. Not just for the turbo itself, but for power overall. The turbine side of the turbo has more than double the pressure of the compressor side at higher boost levels.
Going over 25#'s on a stock turbo really doesn't do much good. Not just for the turbo itself, but for power overall. The turbine side of the turbo has more than double the pressure of the compressor side at higher boost levels.
Elder User
Joined: Feb 2006
Posts: 547
Likes: 0
From: Tennessee
My 2002 is bone stock, and I pull about 0-5 unloaded running around town, 5- 10 in general towing on the interstate, and have seen a max of 17-18 pulling our travel trailer on a sizeable grade at speed. I've seen several other posts on this and other forums where people with stock 7.3's are putting up very simiar numbers.
Junior User
Joined: Jun 2006
Posts: 72
Likes: 0
From: Oxford, MS
I installed my boost gauge about 2 months ago and even with WOT i never saw the boost go over 18#......THEN......I kept hearing people tell me about unplugging the red line from the wastegate.......SO I DID THAT...........NOW......I see boost pressures to 26# WOT.
How can that be if I don't have a MAP relief valve? Is my gauge not reading correctly?
I also took the insulation off the intercooler hot pipe and WOW....I can hear everything now...I like when the boost is high and I shift gears and it sounds like a big SHHHHHOOOOOSHHHHHHHHH when it lets go of all that pressure. Is that OK or am I hurting something? I guess the air is coming out of the hole where the red line used to be. Am i right?
Thanks,
How can that be if I don't have a MAP relief valve? Is my gauge not reading correctly?
I also took the insulation off the intercooler hot pipe and WOW....I can hear everything now...I like when the boost is high and I shift gears and it sounds like a big SHHHHHOOOOOSHHHHHHHHH when it lets go of all that pressure. Is that OK or am I hurting something? I guess the air is coming out of the hole where the red line used to be. Am i right?
Thanks,
Post Fiend
Joined: Jul 2005
Posts: 14,582
Likes: 12
From: 21791
no actually, youre wrong. the woosh sound is the sound of air coming out of your intake. if you have an open element intake then it is amplified. when i let out of the pedal when i have ~10+ psi of boost, i get an awesome squealing/screeching sound from the turbine. it sounds reallly cool, and i acceleate to about 10psi at the end of the gear and then let out so i can hear the sound and then it shifts and im off again. pretty NEAT.
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Junior User
Joined: Jun 2006
Posts: 72
Likes: 0
From: Oxford, MS
Originally Posted by strokin_it7.3
no actually, youre wrong. the woosh sound is the sound of air coming out of your intake. if you have an open element intake then it is amplified. when i let out of the pedal when i have ~10+ psi of boost, i get an awesome squealing/screeching sound from the turbine. it sounds reallly cool, and i acceleate to about 10psi at the end of the gear and then let out so i can hear the sound and then it shifts and im off again. pretty NEAT.
So did unplugging that red line was the increase my boost pressure readings?
Thanks,
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Post Fiend
Joined: Jul 2005
Posts: 14,582
Likes: 12
From: 21791
open element- filter such as the AFE or the Tymar/6637 filter, with no airbox surrounding it. it is possible you are getting the woosh sound all the way out back through the filter. do you have the fendersleeve?
unplugging the red line (and of course plugging the elbow with a bolt or something) will cause the boost to rise because the wastegate no longer becomes effective until the exhaust pressure can overcome the pressure that is holding the flapper valve closed. now the exhaust pressure is not dumped out to keep the turbocharger within a safe PSI limit that ford establishes. this forces all of the exhaust through the turbine and now that means you have more oomph pushing on the wheel, so naturally you will get more boost. with the stock .84 A/R exhaust housing, the turbocharger becomes alot more inefficient at and above 25psi. at this point it no longer increases airflow, it just superheats the air and makes the intake temp ALOT higher which is bad.
if you want a lesson on wastegates and turbocharger efficiency just holler.
unplugging the red line (and of course plugging the elbow with a bolt or something) will cause the boost to rise because the wastegate no longer becomes effective until the exhaust pressure can overcome the pressure that is holding the flapper valve closed. now the exhaust pressure is not dumped out to keep the turbocharger within a safe PSI limit that ford establishes. this forces all of the exhaust through the turbine and now that means you have more oomph pushing on the wheel, so naturally you will get more boost. with the stock .84 A/R exhaust housing, the turbocharger becomes alot more inefficient at and above 25psi. at this point it no longer increases airflow, it just superheats the air and makes the intake temp ALOT higher which is bad.
if you want a lesson on wastegates and turbocharger efficiency just holler.
Junior User
Joined: Jun 2006
Posts: 72
Likes: 0
From: Oxford, MS
Originally Posted by strokin_it7.3
open element- filter such as the AFE or the Tymar/6637 filter, with no airbox surrounding it. it is possible you are getting the woosh sound all the way out back through the filter. do you have the fendersleeve?
unplugging the red line (and of course plugging the elbow with a bolt or something) will cause the boost to rise because the wastegate no longer becomes effective until the exhaust pressure can overcome the pressure that is holding the flapper valve closed. now the exhaust pressure is not dumped out to keep the turbocharger within a safe PSI limit that ford establishes. this forces all of the exhaust through the turbine and now that means you have more oomph pushing on the wheel, so naturally you will get more boost. with the stock .84 A/R exhaust housing, the turbocharger becomes alot more inefficient at and above 25psi. at this point it no longer increases airflow, it just superheats the air and makes the intake temp ALOT higher which is bad.
if you want a lesson on wastegates and turbocharger efficiency just holler.
unplugging the red line (and of course plugging the elbow with a bolt or something) will cause the boost to rise because the wastegate no longer becomes effective until the exhaust pressure can overcome the pressure that is holding the flapper valve closed. now the exhaust pressure is not dumped out to keep the turbocharger within a safe PSI limit that ford establishes. this forces all of the exhaust through the turbine and now that means you have more oomph pushing on the wheel, so naturally you will get more boost. with the stock .84 A/R exhaust housing, the turbocharger becomes alot more inefficient at and above 25psi. at this point it no longer increases airflow, it just superheats the air and makes the intake temp ALOT higher which is bad.
if you want a lesson on wastegates and turbocharger efficiency just holler.
Thanks for the info. I haven't installed the fender sleeve yet, I was waiting to do that when I get my chip from Jody.
BUT!!!!!! I haven't plugged the red line!!!! OH CRAP!!!!! Have I hurt anything?
Post Fiend
Joined: Jul 2005
Posts: 14,582
Likes: 12
From: 21791
Originally Posted by ncm0008
The "red line" is the little vacuum line that comes off the top of the waste gate. I had to search for this as I was wondering the same thing, but didn't want to ask and get flamed for beeing a "newb" 
it is actually under pressure. there is a wastegate control system on the front of the compressor manifold, down low. there is a green vacuum tube that goes to the inner-side of the intake tube that connects to the compressor inlet, and the red line goes to the wastegate actuator canister, and it controls the wastegate operation with the pressure applied to the diaphragm inside. starts opening the wastegate as low as 5psi of boost. must suck to have wastegates, doesnt it?
Logistics Pro
Joined: Mar 2004
Posts: 4,221
Likes: 3
Originally Posted by strokin_it7.3
starts opening the wastegate as low as 5psi of boost. must suck to have wastegates, doesnt it?
Also, for anyone that's curious, here's a pic in which you can see the red and green lines, to go along w/ what Kris was talking about:
http://community.webshots.com/photo/...86590301EDVRlG
The red hose goes from the connection on the intake manifold to the wastegate actuator (sorry the pic doesn't show the connection on the other end of the line). The boost through there tells the actuator to open the wastegate. Since there's always boost there, it's vented through the green line back to the intake until the PCM tells it to open the wastegate, and then the pressure is directed at the wastegate actuator and it opens. That's my understanding, at least.
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