Lockjaw Posted May 23, 2002 Share Posted May 23, 2002 YOu could have a leak where the barrel washerd get crushed down when you put them in the fitting and tighten the nut. Are they measuring from the same place? In other words, you are not measuring one off the turbo and one off the intake manifold, right? Are you intercooled? I have always used to nylon tubing without an issue, although I may not know I have one. HUMMM... Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted May 23, 2002 Share Posted May 23, 2002 What kind of boost gauge is it BTW? Does it show 0 psi when the engine is off? I have a VDO model that does not pick up until 2psi, so I don't know what mine is doing until that point. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted May 23, 2002 Share Posted May 23, 2002 What kind of boost gauge is it BTW? Does it show 0 psi when the engine is off? I have a VDO model that does not pick up until 2psi, so I don't know what mine is doing until that point. Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 23, 2002 Share Posted May 23, 2002 I've heard that about VDO gauges, but the one in my 92 GSX always comes back to 0. I guess I might be a bit suspect about one that doesn't, but no going to zero doesn't necessarily mean that it doesn't read correctly above that. Somebody on the DSM.org mail list tested a few that didn't zero, as I remember, and they were fine above their "sticking point". Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 24, 2002 Author Share Posted May 24, 2002 I'musing an inexpensive gauge, not sure of the brand, but it agrees with the gauge I replaced. The gauge I replace measured in inches of mercury for both negative and positive pressure. Kindof weird. Basically 10 inches of mercury translates to 5psi (approximate). It was anold Rayjay gauge. Anyway, it used to rea around 15 in/hg (7.5psi). It does read zero when the engine is off. Do the gauges measure average pressure, where mayby my computer measures peak? I'm confused. I'lllet you guys know what I hear back from AEM. Pete Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 24, 2002 Author Share Posted May 24, 2002 What is a good way to measure the accuracy of a boost gauge? My mechanical boost gauge is telling me 7.5 PSI, where my Wolf3D computer logs 12psi . I've got a call into tech support at AEM, but I was wondering if anyone has seen similar discrepencies. I'm running the nylon tubing that came with the boost gauge, and I have braided line going to the wolf computer. Any help appreciated.... Pete Quote Link to comment Share on other sites More sharing options...
awd92gsx Posted May 24, 2002 Share Posted May 24, 2002 I'd check it with a Mightyvac. pparaska - did you know that your factory guages are made by VDO? VDO is the prime supplier of guages to Mitsubishi. Quote Link to comment Share on other sites More sharing options...
pparaska Posted May 24, 2002 Share Posted May 24, 2002 I didn't know that - but the stock DSM "boost gage", as you probably know, is a display of a calculation the ECU makes based on MAF readings, etc. Not very accurate at all once you start changing stuff! I just put a mechanical VDO gage in to find out what the boost REALLY was. Quote Link to comment Share on other sites More sharing options...
Dragonfly Posted May 24, 2002 Share Posted May 24, 2002 Gage accuracy 101: Nearly every gage that has a 2.5" face or smaller has an accuracy of + or - 6% full scale (ie 100psi = + or - 6psi), if the gage is larger than 2.5" your accuracy is + or - 4% full scale. When using a compound gage (vacuum and pressure on same gage) the vacuum side is + or - 8% to 10% and the pressure side is as stated above. There are mechanical gages more accurite than that but they are not generaly durable enough to be used in a car. The electrical gages work in a different manner using a diaphram connected to a rheostat (simplest example - they are not all like that), because of the way they are made the electrical gages usualy have an accuracy of 2% to 4% indicated value (ie 10psi is + or - .2psi, and 20psi is + or - .4psi). With that said I can tell you that the more accurite reading is coming from the electrical gage, so your next concern is the source for your signal as said in a previous post. If you have concerns about the accuracy of your gages check your phone book for metrology labs, these are calibration labs and they can tell you exactly what your gage is reading at any given pressure. Dragonfly 13 years mechanical and dimensional calibration tech. Quote Link to comment Share on other sites More sharing options...
z-ya Posted May 24, 2002 Author Share Posted May 24, 2002 I'll try the mighty vac to check for accuracy. I was also thinking of using the gauge on my compressor's regulator to check it. this is goods new as it appears that I am only running around 8psi. Thanks, Pete Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted May 24, 2002 Share Posted May 24, 2002 You need more boost than that to have alot of fun. HEHE. You could have had a boost spike that showed up on the EFI deal you have, and you may not have been looking at the guage when it happened. BTW, my VDO starts at 2 psi and does not register vaccuum on purpose. It isn't broken. I like it that way so I don't have to watch my needle move all over the place. I really like this guage. I have a little SW one the reads to like 40 or so psi, but it is backwards. Boost is on the left and vaccuum is on the right, and it confuses me. My car spikes boost hardest in second gear ever since I went ot the JWT system. If I get any detonation, it is when it spools the turbo on the 1-2 shift. ALways. I have the t-5. Quote Link to comment Share on other sites More sharing options...
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