Re: Boost Guage Accuracy

["Scott Mo." <scottmo@teleport.com>]

Mike,
 
> This slowness kinda goes against my experience in the 91 200q. My >turbo whines loud enuf to clearly hear.  When I reach max boost of 1.8 >bar on the gauge, the turbo whine stops increasing in pitch. It's not >like the turbo quits spooling up and 2 or 3 seconds later the gauge >catches up and reads 1.8.  In 2nd or 3rd gear, it takes less than 3 >seconds to go from .5 to 1.8

Well, I haven't tested the 91 200TQ 20V to see how long they take to
make boost, so this may be an apples to oranges comparison, but they
should spool up pretty quick, with the dual exhaust and all those extra
valves in the cylinder head.....I have checked my 89 200TQ which uses
the same K24 turbo as is used on the 91 200TQ 20V. I have a stiffer
Waste Gate spring (1.7 bar) and my ECU is set to make 1.8 bar. In third
gear, my car will go from 0.45 to 2.0 bar (overboost) in ~1.5 -1.7
seconds. I use a pressure transducer and a portible Digital Oscilloscope
to capture and graph the boost versus time profile while stomping on the
throttle.

 My experience with an analog Vacuum/Boost gauge shows the needle moving
up very quickly and then I can watch the stock boost gauge count up to
the correct value after that. My comment of "several seconds" lag may be
over doing it a bit, but I have never seen the stock boost gauge respond
quickly enough to show the brief overboost that occurs for about 0.5
seconds, even though the analog boost gauge will clearly show the needle
swing past the 1.8 bar point and then settle back down to 1.8 bar.

The real reason to get a separate vacuum/boost gauge is so you can
impress all your friends during a WOT test drive when they say oooohhh,
ahhhhhhhh as the needle gets pegged at 15 - 25psi of boost....

Try and find a gauge that reads about 20% high, this will really impress
your friends...works for me....

HTH
Scott Mo.