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Thread: Mechanical vs electronic - completely different reading

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    Mechanical vs electronic - completely different reading

    Recently installed a Glowshift (safe the flaming you Autometer diehards) and also got myself another Bluetooth OBDII reader (been using one for years on my BMW's, but it wasn't compatible w/ Fords) while using the Torque app on my Android phone.

    Since having the boost gauge, I've been reading around 21lbs of vacuum at idle, and under WOT I'll get the 13-15psi range depending on how long I stay in it. Gauge zero's out just like it should w/ the truck off.

    With the OBDII reader I'm reading /out 25lbs of vacuum, and WOT I don't read over 6psi. While writing this, I never checked it it's readin zero while the truck is off.

    Now, knowing I've got a 6lb lower, intake and my exhaust mods being the only physical changes to my engine at this time, it makes sense why I'm hitting the boost numbers I am. My concern is where is this factory sensor that is feeding the ECU information so I can change it for a more accurate one. If the ECU is only seen half of the boost I'm actually running, that can't be good for driveability. Hell, maybe that's the reason only get 9-11MPG even after all new fluids and plugs.

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    I think the sensor you are reading is probably the boost bypass valve, and it's operation is either open or closed, the actual psi reading should not effect driveability or gas mileage at all (how often are you in boost? for me it's for 3-4 seconds tops...)

    the only sensor that reads vacuum for the ECU is the MAP sensor.

    addtionally, without having a self calibrating boost gauge (like one of these -
    http://www.summitracing.com/parts/ATM-6359/) which calibrates to ambient pressure every time the truck is turned on (has its own MAP sensor), than you can't really trust the boost gauge either.

    In any case, boost is not a tuning aide and has no effect on the tune, what does effect driveability, gas mileage, etc is the air/fuel ratio, and having a good self calibrating wideband a/f gauge like an innovate is what you should be more worried about with the mods that you have.
    2002 DSG HD #09617 NHTOC Truck of the month November 2012
    Ported eaton/plenum/tb, 6lb lower, SCT BA-2600 MAF, OBX longtubes, JLP intake, FTVB, L-spec bilsteins, Hotchkis TVS, 22" replicas. Tuned by Ray McClelland of FTK

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    I see three widebands on eBay...but I've no idea which model number is the one to get. Also, I'm guessing Glowshift is out of the question to have matching gauges. Looking at the two, Glowshift mentions how it uses the most current LSU4.9 - http://www.ebay.com/itm/52mm-Tinted-...5de017&vxp=mtr while the Innovative MTX only uses LSU4.2 - http://www.ebay.com/itm/INNOVATE-INN...d68e7a&vxp=mtr A friend said it comes down to how many times a second it samples the data, which is something I have no clue about either gauge, but either way they both use Bosch 02's
    Last edited by m5james; 07-17-2012 at 01:24 AM.
    2002 HD F150 DSG #01235

    Powertrain: Unknown tune, 6lb lower running 13-15lbs, TR5IX's @ .36, BA2400 MAF, deleted precats/Magnaflow postcats, K&N filter w/ heatshield, L&S separator, rebuilt 4R100 w/ shift kit. Plans - KB2.3, BA2400, 255's, TR6IX's, new tune!
    Interior: Harley custom mats F&R, Glowshift 7 color LED boost gauge. Plans - 3M Di-NOC wrapped in graphite carbon fiber, LED conversion, sound deadener
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    I run the G2, it matches the stock gauges ok during the day, but doesn't match at night, doesn't really bother me, mainly it's very easy to read in the corner of my eye while driving, though I do look at the boost/vacuum gauge pretty often when I'm trying to drive for good gas mileage (keep it around 10" of vacuum while accelerating).

    G2 Gauges: Air Fuel Ratio Guage

    they make several styles, all that really matters is getting a kit with the LC-1 sensor, as that's innovate's calibrating wideband unit that also has a bad sensor detector so you know when it's really time to replace the sensor.

    here's an article comparing widebands -
    http://tunertools.com/articles/FordMuscle.pdf

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    I'll have to read the article, thanks. I thought it would probably be better to have a digital display in this case since I need something so accurate, correct? A needle leaves room for variances.

    I kinda though that having a sideband would be like my boost gauge...after it's first use, it's basically useless See the truck already has a tune. How much is anything going to change after the fact that I wouldn't notice obviously otherwise, ie if a belt broke, coolant hose popped, etc. Short of driving in the winter, is my understanding that these readings won't change, and it's not like I'm going to go get a winter tune...Seattle only goes from 40's to 70's most of the time anyways. I'm just trying to justify another gauge and hole in my dash

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    it's really just a tuning aide, and I feel that a needle is a quicker alert to me than a digital readout, as the digital readout will always roughly look the same, 2 digits 1 dot and then a 3rd digit. The sweeping needle is a really quick indication if the truck is behaving correctly (under 12:1 while in boost, about 14.7 at idle and cruising down the freeway).

    I don't think it's critical to always keep an eye on it, but like a fuel pressure gauge I think one or the other should always be in the line of site on a v8 running ~15psi of boost, I went with the wideband as I tuned the truck myself and unless something is horribly wrong the fuel pressure is what it is and can't be changed without a different regulator, which isn't needed on these truck unless you're doing something weird like going to straight E85. I'm just very afraid of a bad tank of gas, fouled fuel filter, or anything like that which would make it run lean when going into boost, and having the wideband in my line of site makes me more confident to drive the truck hard when I want to.

    The gauge type analog needle vs digital readout is really just preference, I think they make a decent one that also has a blinky light that sweeps the face to light up various a/f ratios to give a quick glance idea of everything is working/tuned right.

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    unless you added a boost sensor for your digital gauge, there's no factory sensor in the engine that measures the amount of boost it's seeing.

    M.HYDE: 2000 HD F-150 #0356 of 8197, Built 05/18/00, Bought 07/03/00, 700/784, 09.89@138.78
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    It's the reading from the OBDII sensor, but otherwise the only boost sensing device I've added to the truck is the gauge itself.

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