After reading the thread below I decided to finally change my O2 sensors. I replaced them and I am running a tank of BK through the system. One thing that was mentioned in the thread was to test the back-pressure in the exaust. This gave me a choice, buy the tool or make one. I chose the cheap route. I took one of my old O2 sensors and removed the sensor business, taped it for 3/8 pipe then added a fitting. Next I bought a vac/pressure gauge from checker. The whole unit cost me $32. My question is what should the gauge read and at what RPMs.
http://www.nissaninfiniticlub....16498
Exhaust back-pressure
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Q45tech
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- Car: 1990 Q45 342,400 miles 22 years ownership with original engine
1995 G20t 5 speed 334,000 miles 16" 2002 wheels - 205/50/16 Sr20ve vvl
Each 0.3-0.4 psi of backpressure at the O2 sensor socket is about 1 horsepower lost. 4,5,or 6 psi might be normal at highest rpm and load.
You rev the engine in gear and record the pressure at 4,000 and 6,000 and 6700 rpm.
The farther away a restriction is from the exhaust valves the less it is meaningful because of the temperature drop of the exhaust gases.
A good experiment is to remove the entire exhaust system or substitute straight pipes [no mufflers] and remeasure the gains [lower back pressure].
http://www.installuniversity.c...e.htmhttp://www.sccoa.com/articles/cwexhaust.php
http://www.users.bigpond.com/p...s.htm
http://www.autospeed.com/cms/a...&P=11
You rev the engine in gear and record the pressure at 4,000 and 6,000 and 6700 rpm.
The farther away a restriction is from the exhaust valves the less it is meaningful because of the temperature drop of the exhaust gases.
A good experiment is to remove the entire exhaust system or substitute straight pipes [no mufflers] and remeasure the gains [lower back pressure].
http://www.installuniversity.c...e.htmhttp://www.sccoa.com/articles/cwexhaust.php
http://www.users.bigpond.com/p...s.htm
http://www.autospeed.com/cms/a...&P=11
