Deadleave Posted May 15, 2011 Share Posted May 15, 2011 I installed a boost gauge today. Tapped via air bypass valve. So to test out its accuracy, I ran it along with romraider measuring relative manifold pressure I noticed a big discrepancy. Boost gauge is able to record last five peak values during a run. Gauge Romraider Peak 1 17.8 15.4 Peak 2 16.4 13.9 Peak 3 15.2 13.1 Kinda scary, unsure which is accurate, even scarier that I've been tuned of off those manifold values. Thoughts ? jay Link to comment Share on other sites More sharing options...
Legend Posted May 16, 2011 Share Posted May 16, 2011 Did you use manifold relative pressure (corrected) in romraider? My '05 LGT My '07 Supercharged Shelby Link to comment Share on other sites More sharing options...
Deadleave Posted May 16, 2011 Author Share Posted May 16, 2011 Not sure, Ill have to check, but checking my logs file, this is the parameter I logged Manifold Relative Pressure (4-byte)* (psi relative) Ill go check on it when I get to my car, and if its there, ill log that vs the gauge. Thanks Link to comment Share on other sites More sharing options...
ClimberDHexMods Posted May 16, 2011 Share Posted May 16, 2011 What kind of boost gauge? Sea level so elevation shouldn't have thrown it off... [CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER] Link to comment Share on other sites More sharing options...
rtbrjason Posted May 17, 2011 Share Posted May 17, 2011 Hmm 15% off.. Can you take a pic of where you tapped into for boost reference? I watch the same boost parameter (MRP 4byte) and have a $20 Sunpro vac/boost gauge and they're close enough to dead on that I can't tell a difference. Link to comment Share on other sites More sharing options...
Deadleave Posted May 17, 2011 Author Share Posted May 17, 2011 took some quick phone pics.... Gauge in the vent , and t fitting by BPV. Link to comment Share on other sites More sharing options...
ClimberDHexMods Posted May 17, 2011 Share Posted May 17, 2011 If your MAP sensor and sensor scaling are stock, it's most likely your gauge reading way wrong. Most likely as in not for sure. If you had a leak somewhere near your MAP sensor, it is possible you could be bleeding off a little pressure. But that is a bit far fetched. You can pressure test your system to be sure, if you have the resources to do so. Even if pressure testing is 99% guaranteed to not show anything per this issue, except perhaps to allow you to have more comparison data points between the two boost readings, it still may pay off in other ways if you actually find a leak. They do happen. Again, just trying to throw out whatever I can, if far fetched. [CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER] Link to comment Share on other sites More sharing options...
dwolson2 Posted May 17, 2011 Share Posted May 17, 2011 good luck with it... how do you like the guage otherwise? Link to comment Share on other sites More sharing options...
bmx045 Posted May 17, 2011 Share Posted May 17, 2011 I had a mechanical autometer gauge and it was reading 7 psi off and -8 inHg vac off, had me searching high and low for a vac/boost leak when there wasn't one at all . Now I have an electronic prosport premium. SWEET. Link to comment Share on other sites More sharing options...
Deadleave Posted May 17, 2011 Author Share Posted May 17, 2011 I am not stock actually Stage 2 map, with supporting mods, and going 16g with supporting mods by end of the week. I went with this gauge, due to the fact that it does boost and AFR from PLX-SM AFR. Since I am installing the wideband, thought this was the best option for gauge. I am going to do some more testing, from what information I got back, the gauge calibrates itself to atmosphere at each start up. So plan is to, test some more, logging manifold pressure relative, absolute and corrected, see if I can pick up on more info. Then start looking for a leak (doesn't seem like it, but one never knows) I think the gauge is stealth tits. Link to comment Share on other sites More sharing options...
ClimberDHexMods Posted May 17, 2011 Share Posted May 17, 2011 I didn't say stock, I said stock MAP sensor and sensor scaling. If Infamous didn't tweek that sensor (no reason he would), then that which matters is still stock. Did you wire the gauge/sensor power to ACC or Ign? Because ACC gets shut off when you turn the key to Start, so if the gauge powers off then back on, it might reference engine cranking (vacuum) as 1 bar atmosphere. I don't know how you will be able to read your AFRs while accelerating super fast, but then that is not really of anyone's concern but your own. Excellent concept to flush mount it like that in the vent. [CENTER][B][I] Front Limited Slip Racing Differentials for the 5EAT now available for $1895 shipped, please inquire for details! [/I][/B][/CENTER] Link to comment Share on other sites More sharing options...
dwolson2 Posted May 17, 2011 Share Posted May 17, 2011 I think it logs the AFR's if I read the post right(on the other thread) Link to comment Share on other sites More sharing options...
WhiskeyTango Posted May 17, 2011 Share Posted May 17, 2011 [ATTACH]100219[/ATTACH] [ATTACH]100220[/ATTACH] took some quick phone pics.... Gauge in the vent , and t fitting by BPV. details on the gague install? Link to comment Share on other sites More sharing options...
CasopoliS Posted May 17, 2011 Share Posted May 17, 2011 [ATTACH]100219[/ATTACH] [ATTACH]100220[/ATTACH] took some quick phone pics.... Gauge in the vent , and t fitting by BPV. Is there a calibrate feature in Lossol's gauge there? Perhaps his scaling for the sensor is slightly incorrect. It would be great if he could incorporate some autoscaling feature. I don't know much about the product, perhaps he already has something like that. Link to comment Share on other sites More sharing options...
Deadleave Posted May 17, 2011 Author Share Posted May 17, 2011 details on the gague install? http://legacygt.com/forums/showthread.php/vent-boost-gauge-digital-led-bars-numerics-125083.html Thats the Lossol's vent boost gauge thread. He is member on here, and he developed this gauge over the last few years. Yes the gauge does auto calibrate at every start up, and its wired to IGN2 right in the fuse panel under driver vent. Did some more testing. My "relative" and "corrected" values are within 2% of each other. I don't know what "absolute" manifold pressure is specifically, but that spike as high as 25 The gauge seems to spike a bit more than the ECU data. If I drive and do small ramped up throttle to say 3.5k they stay pretty clode, both showed 17.4/17.5 If I go WOT, and hit 4.5k quickly the gauge will show a peak @ ~18, but not in my logs. Or if I just rev from a stop to go up a hill, gauge showed 10 psi vs 8. Not to worried, car drives fine, this weekend, I plug in a friends gauge and compare that to my romraider data. If its off, its my sensor, if it matches, then gauge probably needs minor tweak. Link to comment Share on other sites More sharing options...
iNVAR Posted May 18, 2011 Share Posted May 18, 2011 What are your numbers reading when you're doing a third gear pull? You know what your target boost level should be around on an average stage 2 tune at sea-level... about 17.5-19 probably, depending on the tune. Is that what you're seeing from both RR and the gauge? Link to comment Share on other sites More sharing options...
STIBungy Posted May 19, 2011 Share Posted May 19, 2011 I would trust the stock MAP sensor more as that's what the ECU uses to make any adjustment it needs for the car to run safely. Link to comment Share on other sites More sharing options...
I Donated thefultonhow Posted May 19, 2011 I Donated Share Posted May 19, 2011 I have the same issue with my VBG1. I have hit over 23 psi when my peak in the tune is 20.5. lossol says that the gauge is much more sensitive to transient boost spikes than then the ECU boost reading is, hence the higher peak readings. I'm not sure if I buy that, but I don't have any concrete reason to disbelieve it either, so I'm giving him the benefit of the doubt. I love the gauge overall, so there is no way I would give it up, even if it's a bit inaccurate. It's just an amazing setup -- probably my favorite mod so far (of all my mods, including the Evo 16G). I am using the oil pressure functionality and not the wideband, though. Link to comment Share on other sites More sharing options...
Deadleave Posted May 19, 2011 Author Share Posted May 19, 2011 Yeah love mine too. I am a casual driver, so I have it off most of the, but its handy to have on hand to see boost, and same with AFR. Since I had to get a PLX wideband, might as well use the 5v to read AFR. This weekend I am going to test the gauge though against another one. Use the same VAC line and log. so Gauge 1 vs logger Gauge 2 vs logger If logger matches either gauges but not G1 vs G2, then at least I know my sensor on ECU is ok. Link to comment Share on other sites More sharing options...
I Donated thefultonhow Posted May 19, 2011 I Donated Share Posted May 19, 2011 Mine is always on, and I am always entertained. The boost graph is so beast. Link to comment Share on other sites More sharing options...
CasopoliS Posted May 19, 2011 Share Posted May 19, 2011 My guess is the auto calibration feature shifts the calibration curve based on ATM measured immediately at startup. That can only define 1 point, not the slope. So it could be that the slope needs tweaked? If the calibration slope is off, my guess is that the gauge would read closer to accurate at low pressures, and further off at higher pressures. Pressure transducers are interesting little things. Who is to say which one is right or wrong. Without a dead-weight test on a xducer calibration machine its tough to say. That being said, your ECU is using the stock sensor, so getting closer to that number would perhaps be preferred since the tune is based off that. Link to comment Share on other sites More sharing options...
LegacyDan Posted May 20, 2011 Share Posted May 20, 2011 "absolute" manifold pressure is relative plus atmospheric so you can probably take away 14 psi from what you get when logging AMP and that should give you your actual boost, that my understanding of it anyway as explained by my tuner Link to comment Share on other sites More sharing options...
I Donated thefultonhow Posted May 20, 2011 I Donated Share Posted May 20, 2011 Nobody is talking about absolute pressure, though. Everyone is talking about relative pressure. Link to comment Share on other sites More sharing options...
LegacyDan Posted May 20, 2011 Share Posted May 20, 2011 ye its all relative Link to comment Share on other sites More sharing options...
iNVAR Posted May 21, 2011 Share Posted May 21, 2011 Deadleave, perhaps you should have a passenger in the car with you that can actually look at BOTH the gauge and RR while your car is actively boosting, so he can tell you if the numbers are matching up. Just because the peaks don't match up doesn't mean the gauge isn't reading properly during other times. Link to comment Share on other sites More sharing options...
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