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#1
10-24-2004, 05:57 PM
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boost question...'85 300SD
about a year or so ago i installed a manual boost controller on my 85 300sd...i set it where my peak boost was right at 11psi...in 3rd gear under full load, it would hold 10psi constantly...it would peak at gear changes to 11psi....well, about a month ago i needed to take the boost gauge out that i installed with the controller...i just plugged up the line that was running to the gauge and took it out, and ive been riding without a gauge for 3-4 weeks....today i decided to check it and see how it was running, because it has been feeling a little sluggish...i used a handheld boost/vac gauge that measures up to 15psi boost....before any adjustments,i took a run to see what was going on...at no point did the boost reach over 9psi...under full acceleration, in 3rd gear, from 2200 to around 3500rpm, it was showing around 8.5psi....but from 3500rpm to redline, it dropped to around 6psi sharply....after shifting into 4th gear, the boost rose back to 8.5-9.0psi....
my question is..what could make me lose boost pressure under full load, but gain it back when rpm's are lower?
__________________
1985 300SD 192,000miles...Astral silver/ Grey MbTex 1983 300D 194,000miles...White/Tan MbTex...my newest addiction 
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#2
10-25-2004, 12:51 AM
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ttt...anyone?
__________________
1985 300SD 192,000miles...Astral silver/ Grey MbTex 1983 300D 194,000miles...White/Tan MbTex...my newest addiction
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#3
10-25-2004, 01:27 AM
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torque, air fuel mixture, a number of things
I don't get high boost at high revs...engine doesn't maximize efficency up there.. My boost is best right around midrange..right where it belongs..crusing speeds. I see nothing wrong with yours....anyone else?
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#4
10-25-2004, 07:51 AM
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Are these different gauges? All gauges have some variability in them.
__________________
'82 300SD - 361K mi - "Blue" "Good judgement comes from experience. Experience comes from bad judgement." listen, look, .........and duck.
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#5
10-25-2004, 09:58 AM
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the gauges are different...one was a dash mount,2 1/4" gauge that measures up to 20psi...and the one i used yesterday was a handheld vac/pressure gauge thats about 4" in diameter and only measures up to 15psi, a much more accurate reading....
the thing is, when i was installing the boost controller, i used the big gauge when making any adjustments...and then, after i got everything set how i wanted it, i installed the small, dash mount gauge....both of these gauges, at that time, showed the same readings....its definitely something going on under the hood....i was thinking it could be the boost controller, maybe the spring has lost some strength over time and is causing my boost to drop....i also wonder if it could be related to not having done the valves in quite some time, i need to get that done ASAP, but i have an issue with the hood...it needs new hinges put on... what brandon said makes me feel a little better....i dont think its a life or death issue for the car....but i would like to know why the boost drops now, and didnt drop at all before.....i think this afternoon ill take the entire boost controller off, and put it back into its stock configuration and see what the boost pressure does...at least thatll help me know if its the controller...thanks guys
__________________
1985 300SD 192,000miles...Astral silver/ Grey MbTex 1983 300D 194,000miles...White/Tan MbTex...my newest addiction
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