Who to believe? ISSPRO or GMTDScantech?

[chrisk1500]

Running my truck with my laptop hooked up I get two different boost readings.

For example, my ISSPRO mechanical boost gauge in my A pillar will read 10psi and my GMTDScantech will show calculated boost as being 11.5-12 psi.

If my ISSPRO gauge is off by a bit, I was actually running 19-20psi of boost when my headgaskets let go (and I haven't turned it down since installing the head studs).

Am I running 17 psi max boost now as indicated by the ISSPRO or am I running 20+ psi max boost as indicated by GMTDScantech? :hand:

 

[Jasonsmack]

I don't know much about the isspro guages so I have to ask this; Is the isspro guage liquid filled or in a sealed/nitrogen filled format? I have seen many guages set up like this give false readings. On the autometer guages sometimes there is a small screw in the top rear of the unit that needs to be opened up and closed to balance the atmospheric pressures inside and out of the guage. I often take a tiny drill bit and put a hole in the housing so it can constantly balance pressures. I have a pair of liquid filled fuel pressure guages in the dyno cell. Some days you could easily tell there was a problem when there was 2 psi reading on the guages before I even turned a switch on. I finally got fed up with it and drilled holes in the screws, no problems ever since.

 

[Turbine Doc]

Psig vs Psia, possibly ?????

PCM is sending Psia to scantech, ISSPRO I believe is psig can you convert to see if they match, also I had a bad MAP sensor on mine (bad high) kept clipping boost early on detected overboost that wasn't real by my my Banks gauge, 12 psig by gauge vs 35 psig (converted) as shown on scanner that PCM was seeing.

 

[gmctd]

Electric guages of a mechanical nature are at best accurate to +\-10%f.s. reading - that means, for a 0-30psi guage, any reading is +\- 3psi at best - I'd believe the scantool, particularly if MAP is close to Baro at idle

 

[Acesneights1]

Chris Is this helps I have GMTDscan and Autometer Fullsweep Boost gauge. They were nuts on with each other.

 

[nvmtnlion]

Believe GMTDScan. Stefan did a lot of work with me when the beta came out to get the readings accurate. I put on a 0-60 PSIG calibrated 4" gauge in place of my ISSPRO marine 0-30. ISSPRO's accuracy is lacking IMO. I have adjusted my ISSPRO to make it more accurate, the drawback is I can't see boost pressures below 4PSIG.

It also makes me not trust my ISSPRO pyro but I have no way to verify it's accuracy. I plan on buying Heath's DiPricol. As soon as finances are better.

 

[Z79outlaw]

Electric guages of a mechanical nature are at best accurate to +\-10%f.s. reading - that means, for a 0-30psi guage, any reading is +\- 3psi at best - I'd believe the scantool, particularly if MAP is close to Baro at idle

I beleive the Isspro gauge in question is mechanical, and I have read many of instances where there accuracy was not very good, technically is the MAP somewhat of an electric gauge too? Is it also subject to your same general rule?

Believe GMTDScan. Stefan did a lot of work with me when the beta came out to get the readings accurate. I put on a 0-60 PSIG calibrated 4" gauge in place of my ISSPRO marine 0-30. ISSPRO's accuracy is lacking IMO. I have adjusted my ISSPRO to make it more accurate, the drawback is I can't see boost pressures below 4PSIG.

It may not be a problem with his program as much as it may be a problem with the MAP sensor as stated before


It also makes me not trust my ISSPRO pyro but I have no way to verify it's accuracy. I plan on buying Heath's DiPricol. As soon as finances are better.

I too, have thought about going with DiPricol gauges but, have questioned they accuracy also as it seems to be that Isspro and Dipricol may be the same company or a meger or a buyout of some sort, I really like the Dipricol gauges as they design them to look like they may of been stock in the truck, unlike autometer that just builds stuff that doesent even come close to the factory gauge designs

 

[Dave12]

Sounds similar to mine. The mechanic that did the work on my truck told me that my boost gauge was not reading correctly. He said there was about a 2 psi difference between what my gauge was reading and what his snap-on scanner was reading. Snap-on was reading more boost.

Dave

 

[Acesneights1]

I love the look of my Autometer guages. They were not cheap. Pyro, boost and Tran were about 300$ IIRC but accuracy is key and from racing days always found Autometer pro stuff to be really good. Plus it looks bad ass too. I have not hooked up my trans guage yet but it will be interesting ot see how it matchs GMTDscan.

 

[Acesneights1]

update on this. I originally said my Autometer was nuts on with GMTDscan but that was unloaded. I saw almost a 1.5 psi difference towing. GMTDScan was reading 15.5 while Autometer was reading 14

 

[gmctd]

Guages means just that: guages - the human interface, can be accurized to +\-3%f.s. - the sending units, or sensors, are as accurate as spec'ed - if the oem buys 5% sensors, then that is what your system gets - not really much point in having instruments accurate to 6d.p.'s in an automotive environment, unless it's in a lab-based scenario - correct factory service-bay procedures for module\sensor testing is to check if it's within spec'ed +0.5v to +5.5v limits - if so, substitute with a known good unit, see if the problem goes away - now, there's the officially-sanctioned NST criteria for accuracy, eh........

Again - trust GMTDScan or AE or whatever - then you're seeing exactly what the PCM is seeing - countermeasures to be derived therefrom