Exhaust Back-Pressure, ever check it?

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

Turbo nerds,

I was reading through chapter 17 in "Maximum Boost" book by
Corky Bell where he checks the exhaust pressure before and
after the turbo on the NSX that had a turbo system
installed. He indicates that the exhaust pressure at the
turbo inlet  is usually 2 to 3 times the boost pressure.
The boost pressure in his case was about 6 psi with the
turbo inlet exhaust pressure measuring out at 15psi, the
pressure after the turbo (exhaust back pressure) was
measured to be 0.5 psi. 

Has anyone with a '86-90 5000/200TQ that are currently
running 1.8-2.0 bar ever check their exhaust system back
pressure while under full boost? I did this on my 89 200TQ
using the pre-catalytic converter sniffer pipe that
connects to the exhaust pipe at the turbo exit. This metal
tube is bolted to the intake manifold and is typically used
for adjusting the CO% using an exhaust analyzer. I did not
like what I saw on the pressure gauge while in 3rd gear,
1.8bar boost at WOT ~6000RPM.............take a guess how
much pressure was shown on the gauge.....1 psi? 2 psi? 4
psi? 6psi ? 8psi? 10psi?

Is there any reason why this location is not a good place
to measure the exhaust back pressure?

It would be interesting to see the difference in exhaust
back pressure on those cars that have the stock turbo but
are running the 3.0 inch exhaust system. If you show me
yours, I'll show you mine............

Cheers
Scott M.
89 200TQ
ConstipatedExhaustPressureDude