To much Boost

Reply Subscribe

Thread Tools

Search this Thread

Mar 4, 2008 | 07:19 AM

mikebadass76

Thread Starter

New User

Joined: Jan 2008

Posts: 13

Likes: 0

To much Boost

I have a 99 F-350 Dually 4x4 that when I get on it hard it will read as much as 31 PSI, I just wonder if that is a bad thing. It runs like a raped ape and I haven't had any problems with is in the last 30000 miles. I have a AFE Intake, Bully dog Exhaust and monitor system, Superchips programer, and billet Torque Converter. Everything I have read says that the 7.3 can't handle more than 25 PSI. I hear a lot of turbo whine which sounds cool.

Mar 4, 2008 | 07:22 AM

STROKIN'IT7.3

Posting Guru

Joined: Jan 2008

Posts: 1,661

Likes: 0

From: Bridgewater, VA

shouldn't see more than 25 i thought the pcm would defuel after that. does it have a boost anhilator? and is this a mechanical boost gauge or on the bullydog monitor (i doubt the digital's accuracy)

Mar 4, 2008 | 08:05 AM

Pocket

Post Fiend

Joined: Jun 2004

Posts: 9,293

Likes: 10

From: Parker, CO

31 PSI will shorten the life of the stock turbo. Every time you push it like that you are taking a chance that it will let go.

Quote:

shouldn't see more than 25 i thought the pcm would defuel after that.

There's a lot of myths about how the defueling works. It doesn't cut off fuel and completely prevent the truck from reaching higher than 25 psi. MAP sensor input is only one of many many variables of the fueling table. Combined with a chip or tuner, the defueling due to MAP is only a small effect. Without any kind of boost fooler, you can still reach well over 25 psi with ease and have lots of power.

Mar 4, 2008 | 10:01 AM

mikebadass76

Thread Starter

New User

Joined: Jan 2008

Posts: 13

Likes: 0

Thanks, I don't get on it hard all of the time because I am a little concerned about it. I also agree with strokin that the digital gauge is not as accurate as the mechanical. When I am cruising at 60 mph the boost is around 5 to 8 psi and slightly on the throttle is around 18 to 20 psi. Is it possible that the AFE intake is allowing the turbo to spool up quicker and its hitting 31 psi. Its the AFE proguard 7 intake the big one that has the new battery tray. Like I said I put about 30,000 miles on it like this and pulled very big trailers. 36' gooseneck that tipped the scales at 25950 lbs and a 44' Toy hauler 5th wheel camper and knock on wood no problems. Except a CPS that was replace last week under a recall. I have 140,000 miles on the truck now and doesn't burn or leak a drop of oil.

Mar 4, 2008 | 11:35 AM

Hiflyer746

Posting Guru

Joined: Jan 2004

Posts: 1,679

Likes: 0

The 7.3 can handle a lot more than 31 PSI. It is true that the turbo is going to be hating life after a while as it is not efficient past 25 PSI. The boost pressure from your turbo is not what you should be concerned about as far as the strength of the motor. . . you are worried about drive pressures. . . or back pressure caused by the turbine side of the turbo. Above 22-25 PSI on the stock turbo. . . the drive pressures go way up. . . somebody had them measured at one point. . . but I want to say when the boost is at 30 on the stocker. . . the drive pressure is around 40. while 40 is not harmful to the engine on drive pressure, it is harmful to the turbo. Once that turbo goes beyond 22-25 PSI it is out of its efficiency range the heats builds on the compressor side tremendously. . so in effect so does the egts, and the drive pressures go sky high. You won't see much of a performance gain by pushing that turbo that high. I would turn the wastegate down to try and keep it around 25. First determine that the wastegate is operating properly. . . and then lengthen the rod a turn and see how it works.
Tim

Mar 4, 2008 | 04:46 PM

ts_stroker

Junior User

Joined: Jan 2008

Posts: 93

Likes: 0

no your gauge is correct i have a mechanical one and with the waste gate unplug i can reach 34lbs in mine. but with the waste gate plugged in it won't hardly see over 25lbs if that....lol

Mar 5, 2008 | 07:29 PM

mikebadass76

Thread Starter

New User

Joined: Jan 2008

Posts: 13

Likes: 0

Sorry for not replying back, Im in the Military and as you can imagine I have crazy hours. I have not done anything to the Waste gate and when I punch it hard I can tell that it is defueling past 25 psi because it loses its punch. How can I tell if the wastegate is operating properly. My friend has a 01 and when you get on it hard it makes that Psssss sound or however you would type it and mine does not do that nearly as loud and when it does you can barely hear it.