a friend of mine is a ford diesel mechanic and told me to partly block the vacuum line going to the map sensor. supposed to give you a little more power and better milage.

 

Hmmmm, seems to me that would CUT your power. It reads MAP for boost and how much fuel to inject, or so I thought.

 

john keenan,

ask your friend to elabroate .. go into detail.. and explain

 

Well theoritically, If it's creating vaccum, that would mean less force on the map sensor, allowing you to overboost if you wanted to, but it would be MUCH easer to put a boost valve in there, so the map sensor never sees high boost levels... my .02

-Robb

 

Yep, when the MAP sensor reads too much boost, your engine goes into a defueling mode, cutting power and reducing boost. With a boost valve in line, you are allowing excess boost to bleed off before reaching the MAP sensor and fooling it to see slightly lower boost that what you are actually running. That keeps the ECM happy and functioning normally without trouble codes, and prevents a defuel situation.

However, most people don't usually run into that problem with a stock truck. Adding a high HP chip or tuner and then you will run into an overboost situation. A boost relief valve takes care of that.

Althought I've never seen anyone try to restrict the line to the MAP sensor, I have a sneaky feeling that if you tried it you might set off the SES light.

 

finally tryed it. I put a piece of plastic in the line with a 1/16 " hole. made a big difference in the power and milage. now getting 17.5 mpg

 

Without knowing it, you have re-invented the boost tube mod (I have one on my pickup). They are commercially available through some of the powerstroke aftermarket performance guys. 1/16" is pretty big though, most that I have seen for sale are around 0.04". How high will the boost go and have you set any codes with 1/16" aperature?

 

no codes. Don't have a boost guage , but another friend does and increased his boost 2lb

 

where is the map sensor located?,i would like to try it,thankyou.

 

What years of PSD will this work on? I have a 1995.

 

So if I have a stock truck this mod will not help ?? Right ??

 

This sounds like a good mod could we get a dis of where the map is and if you don't have mods will this work

 

Map in the OBS trucks is on the firewall above the A/C dryer.(passanger side) I can't see it making any difference unless you are running a chip and hitting overboost pressures. My truck will only make 18psi boost with no chip.

 

can only get so much so much fuel out of stock injector/programming. so you will only get soo much boost. i was running that when i still had my stock injectors in the truck, with the jodi tipton chip, with my new injectors i was worried about killin a turbo cause if i stand on it i can peg my 35 psi boost gauge now, turbo aint gonna last if i keep doing that. still havent made up my mind what im gonna do about a turbo.

it works good in a chipped truck i was running a .030 hole in mine worked nice

 

I have a 0.30" boost tube and 70 hp chip on stock injectors, I don't know what the max boost I could achieve because I loose my nerve at 30 psi. The idea behind the boost tube is that it increases the level at which the MAP detects overboost, defuels and dumps the wastegate. So you should see increased boost even in stock applications. I wouldn't reccomend running one without a boost gauge though, as you are defeating one of the engine protection features.