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Boost Control

G

gulfyankee

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Location
Jasper, TX
I am having issues with my boost. A few months ago I made a TM, because the factory system wouldn't hold a steady boost(cracked vacuum line). It seemed to work ok, i could boost as high as i wanted. The issue is at cruise. If i have the TM set at say 10-12 psi max, I am still ending up with 6-7 at cruise. I feel that is too much. If I turn the boost down so I am getting about 3-5 at cruise, then max boost is only about 7-8 lbs, and I end up blow a bunch of black smoke at full throttle.....

So today I pulled the vacuum system off of my spare engine and reinstalled it onto my truck. Good boost, spikes at about 14 psi then settles down to about 10 under full throttle. In 4th at 70mph(2500 rpm) on cruise, the boost will drop down to 2 psi, which should be good for economy. But in 5th at 70mph(1900 rpm) on cruise, boost is staying up around 7-9 psi.

I just want some way that will give me good boost, 10-12 psi, at full throttle, while dropping it down low at cruise when boost isn't really needed.

Any suggestions?
 
whats your actual fuel mileage in either condition? Just because you are making boost pressure doesn't necessarily mean you are using more fuel.
 
Do a search for Boost fooler or you would have to get a reflashed ECM. Same thing I found when I went to manual wastegate controller.
 
Am getting 16-17 mpg.....seeing sustained 12 lbs boost going up hills. isn't that high value for the boost for the factory settings?
 
Maybe the '95 is different, but mine was about 8 psi factory (with all vacuum components).

I devacuumed it, made the TM, and set it for 12 si max. 18.7 mpg avg to La Paz, Baja.
I got 1 SES light in 6 months IIRC.
Lowered it to 10 psi max, no more SES.
They will max out at whatever you set them for.

Now I get 20.5mpg IF we don't get stuck in stop and go bumper to bumper traffic, or it goes down to 17.

Of course, I have higher gears and better aerodynamics...

BTW, I used to use soy oil and diesel kleen additives, now nothing but Opti Lube.
Could have something to do with MPG.:D Oscar Mike Golf
 
Its just a function of programming. In a table of RPM versus fuel rate.

What happens is, you are probably at 2000-22000rpm in 4th while requesting about 30mm3 fuel, and then you shift to 5th, which brings you down to 1700RPM or so, which by the table sends boost to 7psi targeted.

I can modify that for you, you just have a unique setup with 5spd and 3.42 gears. And fuel mileage will go up if we drop that down to about 3 psi boost. The beauty of the vac system is any boost you want at any condition. No one cared to tweak with it though because the lines were always cracking or pumps dying.
 
i have spare vacuum pump, and can modify the lines if need be, already using my spares lol.....and i will just carry around my tm as a backup.....sending you a PM buddy
 
Are you using a scanner or GMTDScan to monitor the parameters? Compare scanner values of RPM with the gauge to see how they compare and what value of boost does scanner see compared to gauge?
 
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