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Discussion Starter · #1 ·
Hi all I know this has been done 1000 times but I wanted to gather some thoughts. I recall my car having previously built boost to 22-23 psi whereas yesterday I did a couple wot third gear pulls and only managed to hit 19.4 psi. I haven’t really heard anything that sounded like a leak. Is it possible that this low boost was due to a heat-soaked fmic? I’m still running the stock fmic. I’m also running a Turbosmart BOV but I doubt that is the issue as it has worked perfectly without leaks since I got it. Could an ecu reflash do the trick?

I’d like to hear thoughts on this as I was looking into a possible solenoid issue. I’ll probably be going out and data logging soon to see where I’m at.


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Discussion Starter · #2 ·
Just went out and did some wot data log pulls from a semi cold start and averaged about 20 psi with a top of 21.3. The only thing I have done to the car in recent time is 1 step colder spark plugs.


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I had a similar problem, ended up being the BOV. I have the Mountune Uprated one. The piston/plunger wasn't sliding internally as it should have been, it was binding.
 

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What is your Oct. Ratio at? Bad gas could also be the culprit or your engine not being able to hit peak boost. Also is your car tuned for cold plugs? I’ve seen a couple instances where cold plugs have decreased power if not tuned properly for them


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Discussion Starter · #5 ·
What is your Oct. Ratio at? Bad gas could also be the culprit or your engine not being able to hit peak boost. Also is your car tuned for cold plugs? I’ve seen a couple instances where cold plugs have decreased power if not tuned properly for them


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I’ve always used sunoco 91 octane and no I’m currently only stage 1 cobb ots tuned. Would you need an entirely separate tune just for adding colder plugs?


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I’ve always used sunoco 91 octane and no I’m currently only stage 1 cobb ots tuned. Would you need an entirely separate tune just for adding colder plugs?


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I have never done it my self, from other posts I’ve seen on the forum it looks like you would need one. That still doesn’t explain why it just started to lose PSI now. How long ago did you install them? When you installed them did you check that they were gapped correctly? BOVs do fail but very rarely, I would pull the plugs to check them before you take that off for inspection. It could never hurt to go down and buy 4 OEM plugs, gap them and throw them in.


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Discussion Starter · #7 ·
They were installed probably 2 months or so ago and they were gapped to the ford recommended gap length. It could have been a gradual thing that I have only recently noticed as I don’t often whip out the accessport while driving to log. I’ll try the oems again and see if boost returns.


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Hi all I know this has been done 1000 times but I wanted to gather some thoughts. I recall my car having previously built boost to 22-23 psi whereas yesterday I did a couple wot third gear pulls and only managed to hit 19.4 psi. I haven’t really heard anything that sounded like a leak. Is it possible that this low boost was due to a heat-soaked fmic? I’m still running the stock fmic. I’m also running a Turbosmart BOV but I doubt that is the issue as it has worked perfectly without leaks since I got it. Could an ecu reflash do the trick?

I’d like to hear thoughts on this as I was looking into a possible solenoid issue. I’ll probably be going out and data logging soon to see where I’m at.


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From what I've read throughout the years, a lot of conservative tunes, like Cobb's OTS stage 1, has set parameters to make power safely. On colder days, less boost is needed to achieve those parameters so you would see a decrease in max boost during WOT. I would try putting back on the stock tune and see if the boost increases then.
 
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OP, the numbers you're seeing aren't far from the norm. On some days I peak at 23.4psi and other days I peak at 20.8psi. I've even seen days where I peaked at 19psi on a 4th gear pull. There are LOTS of variables. Temp, fuel, knock (probably fuel related), plugs, heatsoak, tune parameters, etc. Try clearing our your KAM. You can do this on the Accessport, or by unhooking the negative lead to your battery for like 15 minutes. This gets rid of the memory your car has of your driving habits...and makes your throttle response more aggressive again (since it might be used to you doing highway commutes with little gas pedal movement or something) and it might help. Worth a shot.

Best of luck.



From what I've read throughout the years, a lot of conservative tunes, like Cobb's OTS stage 1, has set parameters to make power safely. On colder days, less boost is needed to achieve those parameters so you would see a decrease in max boost during WOT. I would try putting back on the stock tune and see if the boost increases then.
You're correct with all but the last bit.

Stock tune maxes at 21psi. Setting it back to stock tune should LOWER his peak PSI.
 

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OP, the numbers you're seeing aren't far from the norm. On some days I peak at 23.4psi and other days I peak at 20.8psi. I've even seen days where I peaked at 19psi on a 4th gear pull. There are LOTS of variables. Temp, fuel, knock (probably fuel related), plugs, heatsoak, tune parameters, etc. Try clearing our your KAM. You can do this on the Accessport, or by unhooking the negative lead to your battery for like 15 minutes. This gets rid of the memory your car has of your driving habits...and makes your throttle response more aggressive again (since it might be used to you doing highway commutes with little gas pedal movement or something) and it might help. Worth a shot.

Best of luck.





You're correct with all but the last bit.

Stock tune maxes at 21psi. Setting it back to stock tune should LOWER his peak PSI.
From my understanding, the stock tune doesn't make such intrusive corrections to PSI compared to ots or some protunes, so if he's seeing 19 psi on the Cobb tune, he might see 21 psi on stock under the same driving conditions. That's just my rational, but you could be right too. Any change would still be a good indicator that the tune has something to do with it.
 

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If you're running the stock tune you are limited by torque targets. So when it's colder out the air is more dense and able to make power easier. So you can hit those torque targets with less boost. If you have a tune installed you will simply make more power and not be limited by torque targets.
 

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From my understanding, the stock tune doesn't make such intrusive corrections to PSI compared to ots or some protunes, so if he's seeing 19 psi on the Cobb tune, he might see 21 psi on stock under the same driving conditions. That's just my rational, but you could be right too. Any change would still be a good indicator that the tune has something to do with it.
Like @UnfocusedST said, it's kinda the opposite of what you're thinking. Under certain conditions the MAX the stock tune hits is 21.x, under ideal conditions like cold air, that number might be 19-20 or so.

On the Cobb OTS or a flash/pro tune...if you don't have a leak and only hit 21 due to cold air or something then the stock tune probably only would have hit like 19 then hit it's goal and stopped. The stock tune is the most intrusive.
 

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Like @UnfocusedST said, it's kinda the opposite of what you're thinking. Under certain conditions the MAX the stock tune hits is 21.x, under ideal conditions like cold air, that number might be 19-20 or so.

On the Cobb OTS or a flash/pro tune...if you don't have a leak and only hit 21 due to cold air or something then the stock tune probably only would have hit like 19 then hit it's goal and stopped. The stock tune is the most intrusive.
Gotcha, thanks for the clarification!
 

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Discussion Starter · #14 ·
OP, the numbers you're seeing aren't far from the norm. On some days I peak at 23.4psi and other days I peak at 20.8psi. I've even seen days where I peaked at 19psi on a 4th gear pull. There are LOTS of variables. Temp, fuel, knock (probably fuel related), plugs, heatsoak, tune parameters, etc. Try clearing our your KAM. You can do this on the Accessport, or by unhooking the negative lead to your battery for like 15 minutes. This gets rid of the memory your car has of your driving habits...and makes your throttle response more aggressive again (since it might be used to you doing highway commutes with little gas pedal movement or something) and it might help. Worth a shot.

Best of luck.





You're correct with all but the last bit.

Stock tune maxes at 21psi. Setting it back to stock tune should LOWER his peak PSI.
Does it fluctuate like this for everyone? I hadn’t really thought of all of the factors that could affect boost pressure I was just thinking that since it is colder outside I should be getting more psi but I guess thats not necessarily true. I’ll try clearing the KAM as you said because my commute is pretty much all highway driving.

I’ll be going stage 2 pretty soon anyway so hopefully I can see some gains.


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Discussion Starter · #15 ·
Thanks for all of the commentary guys I’ll see what I can figure out about it in a little.


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Does it fluctuate like this for everyone? I hadn’t really thought of all of the factors that could affect boost pressure I was just thinking that since it is colder outside I should be getting more psi but I guess thats not necessarily true. I’ll try clearing the KAM as you said because my commute is pretty much all highway driving.

I’ll be going stage 2 pretty soon anyway so hopefully I can see some gains.


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Yup. I regularly see quite the fluctuation myself. It is this way for any turbo car like this also. My buddy in his WRX might see 16 one day and 14.5 the next, much colder day. Less boost to hit the same power
 

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Discussion Starter · #17 ·
Yup. I regularly see quite the fluctuation myself. It is this way for any turbo car like this also. My buddy in his WRX might see 16 one day and 14.5 the next, much colder day. Less boost to hit the same power
Dang. Resetting the KAM really improved the throttle response and I was able to log 21psi so I’m happy. Thanks for the help. I guess I was just concerned because I did some hard pulls and could only get a 19.4 a couple days ago. Again, I don’t pull out the accessport too often so I didn’t realize boost could and would fluctuate on a day-to-day basis.


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Dang. Resetting the KAM really improved the throttle response and I was able to log 21psi so I’m happy. Thanks for the help. I guess I was just concerned because I did some hard pulls and could only get a 19.4 a couple days ago. Again, I don’t pull out the accessport too often so I didn’t realize boost could and would fluctuate on a day-to-day basis.


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Yes sir! I am a 62 mile a day commuter on the highway, I know all about it. Try to get into the habit of resetting that once a month or something. It'll learn your habits pretty quickly, and it doesn't hurt to reset it. Sometimes when my car feels sluggish I'll reset it to get that sweet raw untampered with power curve back!
 
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