PLX DM-6 Gen 4 Install

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georryan
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PLX DM-6 Gen 4 Install

Post by georryan »

Ok, so after doing lots of searching and looking around I settled on a PLX DM-6 (Gen 4) wideband Air Fuel ratio gauge.

I chose it because of it was expandable with the option of adding other sensors, and more importantly, it allowed for a narrow band simulator wire so I could just replace my existing narrow band 02 sensor. The install was actually pretty straightforward, and after getting it hooked up, everything worked right out of the gate.

I ordered the DM-6 Genertion 4 SM-AFR kit that came with the AFR sensor along with a multi-gauge display.

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The multi-gauge display came with the gauge, an extensions, splitter (for additional sensors if you choose not to pigtail I would imagine).

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The SMF sensor came with the little sensor module, a grey wire for narrow band output that can be pinned into the pigtail going to the guauge, the Bosche Wideband sensor (LSU 4.9), a wiring harness that connects the wideband to the sensor module, a daisy chain cord (for additional sensors), and some power wire (ground & power).

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I ran the harness through the rubber plug behind the clutch pedal that comes out near the brake master cylinder. I had already ran wires through it for my AWIC pump and my boost gauge hose, so it was pretty simple to cut a little larger opening and fit the new harness wire through. The harness plug is pretty good size though, so getting it through the plug was a bit of a struggle, but all in all, not too bad.

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To plug the narrow band wire into the ecu, I found the oxygen sensor's signal pin (B43.6 - White wire) from an EJ20 ECU pinout in one of the Rob Tune threads (I'm running a Rob Tune - but the pinout should be the same on an EJ22T ecu). I just used a sewing needle to pull the pin out of the harness and then spliced a connection to plug in my own narrow band signal wire. I made it reversible so I could pull it out if I need to.

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You can see here that I had to plug the pinned grey wire (supplied) into the pigtail connector of the gauge. It has two empty spots for pins to be added to the connector. Both supply an analogue output.

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I wasn't sure where to put the module at first, but I wanted it under the dash somewhere and hidden away. I thought about hiding it behind the radio, but found a good spot for it above the driver's right knee under the dash. There is a metal lip that I was able to zip-tie the module to. With all the connections in there, it is pretty solidly in place and shouldn't be going anywhere.

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I wired power to a switched ignition power wire that I had previously used for the AWIC pump, so that was easy enough to splice in. I then used ground on the a bolt into the chassis between the driver's right knee and the radio.

The little sucker is pretty bright I have to say but not too obtrusive. The LED lighting is definately more vibrant than an incandescent gauge. The gauge is touch sensitive with 3 touch areas for changing modes and readouts.

With the one sensor I have the AFR, volts, sensor life expectancy, and sensor reaction speed. With each of those you can change how that information is displayed on the gauge in a few different ways.

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The gauge is reading a bit rich at idle on there because the engine was cold and I had just reved it to see it work. Normally it sits at about 13.6-14.7 while idling.

I took it for a drive and was seeing the it read in the 12's under WOT with 13psi of boost on the vf-23 and the rob-tune. I've wanted to get this thing installed before playing with any higher boost numbers. I'm thinking this is a little lean (?). I'll be doing some more testing and looking for boost leaks and/or getting my injectors cleaned and flow tested. I'm getting some knock light flicker under load when boosting and I need to figure out if it is a legitimate warning or not.

So far I like it, but haven't had much time to play around with it yet.

-Ryan
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turbo970
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Re: PLX DM-6 Gen 4 Install

Post by turbo970 »

i have a older plx i likes it. i need to upgrade soon
Legacy777
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Re: PLX DM-6 Gen 4 Install

Post by Legacy777 »

Nice write-up and install Ryan!

Yeah, I would agree that AFR's in the 12's is a probably a little too lean for running full boost. I'd suggest targeting 11.0 at full boost.
Josh

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georryan
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Re: PLX DM-6 Gen 4 Install

Post by georryan »

That's what I was afraid of. I'll have to check for any boost leaks. I'm going to pull out the injectors and have them flow tested as well. I never had them tested before putting them in, so its possible one may be putting out less volume than the others, although I don't get any hesitation issues. The car will drop into the 11's and 10's under partial throttle, but full throttle it drops to 12's and 13's under full boost (which is actually at 12 not 13). I have the stock exhaust on there right now, and I'm curious how the 3" might affect things.

Anyway, got to get it all sorted. Would the fuel pressure regulator fit this scenario at all? I don't seem to recall many people really having problems with their FPR.

-Ryan
91 Pearl White Sport Sedan
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Legacy777
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Re: PLX DM-6 Gen 4 Install

Post by Legacy777 »

Is your wideband O2 sensor in the stock location?

3" exhaust wouldn't affect the AFR's.

Boost leaks would typically cause richer AFR's since you're losing metered air. Are you running the stock airbox or an aftermarket style filter?
Josh

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georryan
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Re: PLX DM-6 Gen 4 Install

Post by georryan »

Wideband is in the stock location. Stock airbox....although, what if I'm getting in air that isn't metered? That would make me a little more lean. The intake was adapted a bit. I have a 90 degree samco hose for the front of the turbo (VF23 doesn't have the metal intake elbow), and I fabbed up an exhaust pipe connector piece to attach the airbox elbow to the scamco hose off the turbo intake. If any of that leaks, I would probably be getting more air than is metered under boost? I'll have to take a good look at it and look for cracks and such that could have cropped up as well.
91 Pearl White Sport Sedan
04 Java Black Pearl Forester XT
2014 Volvo S60 T5
18 KTM 1290 Adventure S

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imtb
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Re: PLX DM-6 Gen 4 Install

Post by imtb »

Thats pretty cool how you can use the o2 sensor and tap into the ecu.

I would like to add some gauges some time in the future.
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Re: PLX DM-6 Gen 4 Install

Post by wtdash »

Didn't read this thoroughly but Rob's tune targets high 10>>low 11:1 AFR.
Td
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Legacy777
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Re: PLX DM-6 Gen 4 Install

Post by Legacy777 »

Yes, if you have an air intake leak pre-turbo and it's sucking in more air then yes that could be causing things to go lean.
Josh

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georryan
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Re: PLX DM-6 Gen 4 Install

Post by georryan »

Well I spent some time spraying carb cleaner around the intake, and all the intake connections pre and post turbo. Nothing. I did notice a small crack in the 90 degree elbow that comes off the snorkus just before the turbo. The clamp covers it, and spraying carb cleaner in there didn't cause any difference in idle. It is possible that maybe the boost leak only happens when under boost since the turbo is pulling more air than usual. I'm getting the injectors sent off to be cleaned and flow tested and I'll see what their results are.

I have a forester now as well. It also has the same injectors I believe. I could toss those in and see if there is any difference. Maybe I'll try that while the others are getting cleaned.

We'll see. First things first. If I keep having problems I'll make another thread. Probably shouldn't muddy up this thread too much. =)
91 Pearl White Sport Sedan
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2014 Volvo S60 T5
18 KTM 1290 Adventure S

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Re: PLX DM-6 Gen 4 Install

Post by Legacy777 »

You should use starting fluid rather than carb cleaner to check for leaks.
Josh

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georryan
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Re: PLX DM-6 Gen 4 Install

Post by georryan »

Oh yeah? Ok, I'll pick some up and see if I notice anything.

I did get my injectors cleaned and I had one injector operating at fair condition. After the clean they all ran within spec. Putting them in actually helped the initial start-up stutter that apparently was worse than the normal ej20 cold start issue. The WOT runs are still running lean, though.

I looked around the internet and heard lots of talk about Walbro pumps sometimes loosing pressure at WOT when they start to go bad. I found some for sale on ebay for a steal with a lifetime warranty brand new with thousands of good reviews, so I picked one up just in case. While I wait I'll pull the current pump out and inspect it. I'll do some voltage/resistence checks on the MAF as well, oh and try some starter fluid around the intake and vacuum lines pre-turbo.
91 Pearl White Sport Sedan
04 Java Black Pearl Forester XT
2014 Volvo S60 T5
18 KTM 1290 Adventure S

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Re: PLX DM-6 Gen 4 Install

Post by Legacy777 »

Ok, let us know what you find.
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
2020 Outback Limted XT

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georryan
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Re: PLX DM-6 Gen 4 Install

Post by georryan »

Ok, well I poked around with some starter fluid. No noticeable differences. I got the fuel pump, and then I installed it. The old fuel pump looked good and with the new one installed easily. I didn't notice any difference in A/F ratios.

So now I'm going to look at the MAF and probably buy an adjustable FPR and see if I can bump up the fuel pressure a little.
91 Pearl White Sport Sedan
04 Java Black Pearl Forester XT
2014 Volvo S60 T5
18 KTM 1290 Adventure S

87 Grey GL-10 Sedan (so long old buddy) - donated
97 Toyota 4Runner SR5 - sold
2002 BMW r1150rt-p - sold
2004 BMW r1200ST - sold
2016 BMW r1200RS - sold
georryan
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Re: PLX DM-6 Gen 4 Install

Post by georryan »

Updates:

So doing some more testing, I did a couple things. I picked up another MAF and FPR from the junkyard. The MAF didn't make a difference. While changing that out I also hooked up a fuel pressure gauge, and used a hand pump (suggested to me by Rob), to test the vacuum and pressure values on the FPR.

What I noticed was the at idle, the car was running 40ish psi of fuel pressure, and pulling the vacuum line off the regulator didn't make a difference. Also, applying pressure, would raise the fuel pressure up. It would be consistent up toabout 10 psi of boost, and then anything above that would eventually drop back down to about 10psi boost, 50psi fuel pressure.

I traced the vacuum line off the regulator to see where it went and compared that to some vacuum diagrams. What I saw was that my FPR vacuum line was attached to my purge valve, when it was supposed to go to an intake vacuum line. Instead, the hose going to the top of the throttle body went to that intake line, but it was supposed to go to the purge valve. I don't know if this would make a difference in stock form, but since the purge valve is inoperable with the Rob Tune, it wasn't doing a thing for me. Effectively, I was neither reducing fuel pressure under vacuum, or increasing it under boost. So whenever I went under boost, the fuel quickly leaned out.

Once I swapped those lines, the numbers looked pretty good. I tested the fuel pressure up to 20 psi with the hand pump, and noticed that the vacuum line was borderline wanting to expand and pop off at that point, so I will need to tighten it with mechanics wire or a zip tie. I also noticed that the fuel pressure would drop some after shutting off the car. I'll be doing some more tests, and swap over the other pressure regulator.

At this point I think I almost have it all squared away. I was running 30ish psi at idle, and 40ish with the vacuum line disconnected. I'm hoping the newer regulator will run it a little higher than that. If I need to, I can pick up an adjustable regulator and set the fuel pressure a few psi higher for a safety margin if I'm seeing any knocks when under boost.

SO happy to get it figured out.

-Ryan
91 Pearl White Sport Sedan
04 Java Black Pearl Forester XT
2014 Volvo S60 T5
18 KTM 1290 Adventure S

87 Grey GL-10 Sedan (so long old buddy) - donated
97 Toyota 4Runner SR5 - sold
2002 BMW r1150rt-p - sold
2004 BMW r1200ST - sold
2016 BMW r1200RS - sold
czei
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Re: PLX DM-6 Gen 4 Install

Post by czei »

Nice writeup, and a cool device. Is there any point in having one on an NA engine, or is this just a turbo thing?
georryan
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Re: PLX DM-6 Gen 4 Install

Post by georryan »

Sure. If you want to have an accurate reading on what your fuel/air mixture is at. I can imagine having one on a motorcycle or other vehicle that has a NA motor. If you are running stock, there isn't too much expectation that things will be off, but it would be a safety measure. Say you go around a corner real fast, and your fuel pump leans out due to a low tank of fuel or something. Your gauge would then alert you of a sudden change in mixture. This could then alert you to let off the gas and save your engine some damage. I know guys at the track have had just that experience.

The nice thing about this little device is you can also see volts, and if my car doesn't start, a quick check at the voltage lets me know that the battery is just slightly too low to turn over the engine. You can also hook up other sensors, like oil pressure or vacuum/boost and run them all to the same gauge. So that aspect is quite nice as well.
91 Pearl White Sport Sedan
04 Java Black Pearl Forester XT
2014 Volvo S60 T5
18 KTM 1290 Adventure S

87 Grey GL-10 Sedan (so long old buddy) - donated
97 Toyota 4Runner SR5 - sold
2002 BMW r1150rt-p - sold
2004 BMW r1200ST - sold
2016 BMW r1200RS - sold
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