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Hey everyone, just got my SCT Livewire tuner with five star tunes. Only have tried the 87 so far and truck seems a lot more responsive And can for sure feel the boost increase. I'm new to turbo charged engines and reading the guages. What is the stock PSI in the ecoboost? And With the 87 tune if I let off the gas.. Psi drops to -11.00 and is steady at -7. Is this normal to have Negative PSI?
 

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Stock max boost is 12 psi.

When in vacuum it is reading in inHG. Not psi. It is completely normal. When idling I see -20.
 
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Man your turbo must be spooling in reverse when you let off the gas.(Loose bearings)..its creating engine vacuum I would go to the dealer and get that checked out... After today I just couldn't help myself !!!
 

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It's a good fun loving group on here. Don't mind if people make funny comments. It's all in good fun.

But no problem. Hope you enjoy the tunes.
 

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The pressure reported out is intake manifold pressure, so once you are out of the throttle and the butterfly valve is closed the intake manifold will still see a vacuum like like a naturally aspirated motor. The turbos are still providing just enough boost that the CAC and upstream of the throttle body will still be positive pressure.
 

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Oh come on now,!,,,
I have never ever in my life ever heard of someone asking about negative boost,you have to think about what the word boost means..its pressure above atmospheric pressure which is about 14 psi your gauge is set to read zero at sea level which is Houston..

i just could not help myself man,I was not making fun of you personally ,but I am a gear head through and through ,negative boost was just the funnies thing I had heard in a while...it is apparently obvious that you have little mechanical experience and if I hurt your fragile temperament I am sincerely sorry for it was never my intention to Insult you....
i could of been rude,and made some sort of comment or responded to your name calling,but their is nothing better than being squeaky clean, cool and fresh like the morning dew.......

seruiosly this is the internet though ,but if you ever have a question I will answer it in a professional manner from this point forward....I used to teach electronics at the local college here in Houston,I also turn a wrench for 20yrs,and owned my own perfomance shop,I only tell you this so you can understand where I was coming from.....any of us that are on here in a regular basis have a fair understanding of this truck or cars in General,so pls feel free to ask...,,...I have also been having a hard time with a build I have been doing so your post was just the highlight of my day.....
MAN I Superduper clean now awesome ,,,,,,wait you weren't talking about used douche were you,lol have a great day....
 

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To OP, when you use the SCT Boost Gauge, it doesn't display exactly correct. When negative, it should really be showing "inHg" vacuum. Which would typically be double the "negative PSI".

Some people's displays do show "Inches of Mercury" (inHg) when Boost goes negative. But mine doesn't either. Instead I get "negative PSI" like you.
 
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Hey everyone, just got my SCT Livewire tuner with five star tunes. Only have tried the 87 so far and truck seems a lot more responsive And can for sure feel the boost increase. I'm new to turbo charged engines and reading the guages. What is the stock PSI in the ecoboost? And With the 87 tune if I let off the gas.. Psi drops to -11.00 and is steady at -7. Is this normal to have Negative PSI?
yep, that is normal
 

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Discussion Starter #15
Thanks for the replies everyone. @aboosted I know you didn't mean any harm by it, I was just looking for serious answers. I meant why was my PSI showing negative readings. I assumed it would stay at 0 if I wasn't hitting the throttle and increase the more I laid down on it. I knew it obviously wasn't bad or revere boost lol, I wanted serious answers on why it went under 0 if I wasn't Hittin the gas. But thanks everyone! Got new spark plugs in today and just the 87 tune feels great. 250 more miles of 87 to burn and I'll be filling up with 93
 

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Oh come on now,!,,,
I have never ever in my life ever heard of someone asking about negative boost,you have to think about what the word boost means..its pressure above atmospheric pressure which is about 14 psi your gauge is set to read zero at sea level which is Houston..

i just could not help myself man,I was not making fun of you personally ,but I am a gear head through and through ,negative boost was just the funnies thing I had heard in a while...it is apparently obvious that you have little mechanical experience and if I hurt your fragile temperament I am sincerely sorry for it was never my intention to Insult you....
i could of been rude,and made some sort of comment or responded to your name calling,but their is nothing better than being squeaky clean, cool and fresh like the morning dew.......

seruiosly this is the internet though ,but if you ever have a question I will answer it in a professional manner from this point forward....I used to teach electronics at the local college here in Houston,I also turn a wrench for 20yrs,and owned my own perfomance shop,I only tell you this so you can understand where I was coming from.....any of us that are on here in a regular basis have a fair understanding of this truck or cars in General,so pls feel free to ask...,,...I have also been having a hard time with a build I have been doing so your post was just the highlight of my day.....
MAN I Superduper clean now awesome ,,,,,,wait you weren't talking about used douche were you,lol have a great day....
I know this is a really old post. But I just wanted to tell ya I thought you handled that with grace and juuuust, the right amount of humor.
It's Just life, right!? Cant be too serious. ?
 

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I know this is a really old post. But I just wanted to tell ya I thought you handled that with grace and juuuust, the right amount of humor.
It's Just life, right!? Cant be too serious.
I gotta ask.......

Since it took a 5 year old post to draw your FIRST response ever amongst us, what will it take to draw your next?

I see you've been hanging with us since last June. I'm just curious. Was it a new brand of coffee this morning? :)

We can use the fresh blood. Lol

"And yea, it's just life. Can't be too serious "

We REALLY need more of THIS.

Sent from my SM-N950U using Tapatalk
 
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