Engine/Transmission (1994 - 1998) boost pressure

[cclemons]

I just installed my brand new boost gauge. At idle I have o psi. Is this normal?The best I ever get is 18 psi and that only holds for a moment then starts back down. At 65 mph it settles down to about 5 psi. Are these numbers normal?If not what would be normal. Thanks for any help.













1996,automatic,totally stock but not for long I hope.

 

[illflem]

All's normal except your 65 mph reading is a lttle high for a stock truck, most see about 3-4 psi cruising on flat land.

 

[SRehberg]

I also run a bone stock '96 2wd auto, and it use to run 3-4lbs @ 65mph, but now consistently runs 5+, going with the wind or no head wind. What would cause the numbers to crawl up ever so slightly? Seems to be adequate on power and runs great...

 

[redram]

Illfem,



that 1 or 2 psi difference is not significant because of road changes, head winds, amount of throttle applied, etc.



My 96 5 speed routinely "cruises" at 5 psi at 75 mph but will vary even with the cruise set to slight chances in road and I live in Houston, can't get much flatter than here. Only change of elevation that we get are the overpasses on the freeways!



Unless you have a fluid damped, 4" diameter 'calibrated' gauge, I wouldn't get too concerned trying to compare one gage to another on different vehicles.



Keep track of what your vehicle does under certain conditions and become concerned when they change.



Regarding "0" readings at idle. Normal. You will not produce any "boost" until you load the engine. The guage should not register any boost at idle. On a gasoline engine, it would go to vacuum.



Cheers.



PS- I used to race (SCCA) a turbocharged 4 cylinder and boost was closely checked by the officials at the National Championships.

 

[bmoeller]

Mine are close to yours. 4-6 on the flat and I've hit 20 max. for a short time at WOT going up an on-ramp empty.

 

[SRehberg]

My boost pressures have increased 2-3lbs over the same stretch of road, which I have traveled many times. It use to consistently run 3-4 and of course higher with a head wind, but normally the 3-4. Now on the same trip (last 10 or so) it runs 5+, so something has changed. I'm not overally concerned, just wondering what happened. It relates to more fuel, otherwise the pressure wouldn't be higher.

 

[redram]

I wonder if it could be an early sign of a fuel filter needing replacement which to maintian the same speed now requires more 'throttle input' resulting in additional boost.



Or, with warmer temperatures, your hose connections on your intercooler are not leaking now resulting in a higher psi in the intake manifold?



Or your 30 dollar boost guage is no longer calibrated correctly?



or????

 

[SRehberg]

You know, all those sound like good possibilities, espcially the guage, as my first one had to go back due to inaccuracies. You may have hit on an area regarding temp, as the other readings were in the winter with colder, denser air. Now things are warming some ?? Thanks for the input, these trucks can keep us guessing.

 

[redram]

So, if I understand this right, you were comparing two different gauges under two different circumstances (Winter versus Spring temperatures) and wondering why you had a 1 psi change in boost psi?



On most the gauges that are installed in a truck (2 1/16 dia), the width of the indicator needle is about one psi or definitely no better than 1/2 psi. Depending on the viewed angle (Point of reference of the driver if not straight on view), there is additional inaccuracy.



These are the kind of things that I was thinking of when I mentioned I wouldn't get too excited over an increase or decrease of 1-2 psi in boost.



Now a 10% drop in fuel mileage combined with a change in boost pressure might be totally differnt, in that you have something else to compare.



JMHO

 

[SRehberg]

Redram, my first guage failed right out of the shute; i. e. the first week, so the readings I am comparing is with the present guage. Today I made the trip again, (100mi. round trip) beautiful 80* day, light breeze, and the pressure was running just at 4 lbs at 65mph. Just last week our temps were down a lot lower, so nothing else has changed but the outside temp. I haven't checked the mileage for awhile, but I go about the same distance, but this is a crude estimate.