Perplexing PLX !!**??

[Dirty Howie]

Here is the log in 3rd. (I guess you can only do 5 uploads per post )

The 0-121 MPH is at frame 4600 ......... 12 second in 80+ temps


DH

[VYSSLS1]

its happening at all rpm's involving closed loop operation at 14.7
and happening on several brands of wideband...4 that I have seen now...

all 4 brands of wide bands using the bosch LSU4.2 (7057) sensor ?? ie innovate, PLX, WB02??

the lsu 4.2 is ultra sensitive to heat, get it hot and it wont read correctly, but put it in the tail pipe and it will read perfectly all day (all be it a little slow)

the bosch LSU4 (6066) is not as sensitive but is 3x the price of the 4.2..

i use 3 widebands for tuning, a Autronic B model with 2 different sensors, Microtech using a LSU4 (6066) and a PLX using the LSU 4.2
nothing comes close to the autronic for heat control and accurate readings

[domestic rice]

I want believe that the WB02's are reading right. My NB read mid to high 890s before headers. 950s and up after headers. Would it not be logical to think that since the probes are further back with LT's it might make it richer or read higher?

How would I get my switch points to switch higher, which will in fact make my fuel trims more accurate and my mpg better?

[Dirty Howie]

Nobody wants to comment further on this ....... Russ, Scott, Doug, Bill, anybody ??????????


DH

[S2H]

I'm saying to believe the widebands
I've now asked 8 different Manufacturers....some of them our budget O2's...2 of them not so budget....
same basic response from 7 of the 8...one of the cheaper ones I'm still waiting on a response from...but I'll guess its gonna be similar also

I've Eliminated the Heat issue by trying it further away from the source...and by adding heat shields and heat sinks...
I can verify the O2 temp after a nice long Drive with both Cruise and WOT...and can say that Heat is not skewing what I am seeing on my wideband....but it is skewing what I see on the narrowbands...
I tried a little experiment on a car I tuned...
I placed one Narrow in the header bung and one further back(using other sides front O2 connector and an extension) in the exhaust...both of them in the same piece of pipe... no cross pipe involved so no contamination from the other sides exhaust...different reading on both...I'd guess from the heat difference...
when I placed the Wideband in either spot it read the same....

Thats My take

I suggest Full Time Open Loop and some Bias Table Tuning work on modded cars...or dual widebands simulating Narrowbands to run Closed Loop

sorry I dont have the log right now...I'll see if I can get it frommy buddys laptop

[VYSSLS1]

if your using a WB in one pipe simulating NB and a narrow band in the other pipe of course your going to get different STFT's bank to bank

the narrow band sensors are extreamly sensitive to heat and are not accurate at all hence the reason you will always get different STFT's day to day with a narrow band, a 50deg temp difference on a narrow band sensor will give you a huge variation in readings,

the only way to do it correctly is it use 2 WB's and sim the NB's off them or run in OLSD full time,

[Dirty Howie]

Scott:

Thanks for all the research. Personally I'm comfortable believing my WB when in open loop. I adjust my VE or MAF and it changes accordingly. And there seems to be a plausable explanation of how heat can alter the functioning of the NB. I will get on a dyno one day for confirmation. Also I can run my original tune which was dyno'd in at 12.5-13.0 to see what the PLX reads.

I am checking fuel economy right now in CL and will try OL next week. If there is no difference in gas milage is there any other reason to be in CL ??

VYSSLS1:

I believe you can run OLMAF don't need to go SD .......


DH

[EC_Tune]

My last comments on this "issue":

If the stock o2's were such a POS why do the OEM's use them? NB's pass emissions tests (that modified vehicles have no chance of passing!) and are warrantied for 100K miles? Yeah, we all know that the OEM's run the engines rich at WOT (in factory form) to protect their warranty. So what, that won't hurt the sensors anyway.

I have tuned a TON of vehicles with the factory o2's, most with LT headers and they don't have issues. Headers can have POS designs so that's your problem not the NB o2's.

NB's work within a WIDE heat range. The switch point doesn't change just the overall range as I have stated before and have tested this as well. As the NB gets hotter (say WOT for a minute or so) the high end of the range will decrease from say 980 mv to 850 mv but the switch points DON'T change. That's another reason you shouldn't do WOT tuning with NB's.

Wideband o2's are made from the same basic material as a NB but have a closed loop (ah yes, widebands are a closed loop system too!) controlled heater and pump circuit. If heat is an issue with a NB sensor it's just as much an issue with a wideband sensor. The remedy with the WB is the closed loop heater control.

Pressures will affect the pump circuit as well so placing your WB ahead of the turbo will give you different readings compared to after the turbo (and a cooler WB as well!) Thus the closed loop nature of the pump circuit as well.

So suffice it to say that if the WB manufacturer has a poor heater or pump circuit controls your results will vary....

EC - Out

[domestic rice]

My last comments on this "issue":

If the stock o2's were such a POS why do the OEM's use them? NB's pass emissions tests (that modified vehicles have no chance of passing!) and are warrantied for 100K miles? Yeah, we all know that the OEM's run the engines rich at WOT (in factory form) to protect their warranty. So what, that won't hurt the sensors anyway.

I have tuned a TON of vehicles with the factory o2's, most with LT headers and they don't have issues. Headers can have POS designs so that's your problem not the NB o2's.

NB's work within a WIDE heat range. The switch point doesn't change just the overall range as I have stated before and have tested this as well. As the NB gets hotter (say WOT for a minute or so) the high end of the range will decrease from say 980 mv to 850 mv but the switch points DON'T change. That's another reason you shouldn't do WOT tuning with NB's.

Wideband o2's are made from the same basic material as a NB but have a closed loop (ah yes, widebands are a closed loop system too!) controlled heater and pump circuit. If heat is an issue with a NB sensor it's just as much an issue with a wideband sensor. The remedy with the WB is the closed loop heater control.

Pressures will affect the pump circuit as well so placing your WB ahead of the turbo will give you different readings compared to after the turbo (and a cooler WB as well!) Thus the closed loop nature of the pump circuit as well.

So suffice it to say that if the WB manufacturer has a poor heater or pump circuit controls your results will vary....

EC - Out

So if I understand this correctly, my headers are a poor design that makes my NB02 read higher (950 vs 890 WOT)? Well shy of getting rid of my headers is there not a way to make the switch points think that 14.6 afr is 800 instead of the 550 or whatever it is from the factory?

Im sure the NB02 works great for emissions and how they have it set up with the FACTORY intake and exhaust. When we start messing with that stuff I dont think it would far fetched to believe that the way the NB reads might be slightly different (probe further back making the temp/combustion out of the factory specks).

If there was a way we could recalibrate the NB to add and subtract fuel at where the WB said 14.7 is It will probably dial in nicely. How it sits now We can have the WB saying 14.7 on the money but the NB thinks its lean due to the mv being off and it will dump fuel therefore messing up the WOT because its now very rich.

Dont know if this makes sense to anyone or not. I might be intotal left field here just trying to think of why so many of us are having problems getting this to match.

I do know that prior to my header install my NB read 890 day in and day out. After the header install the same NB reads 950.

[Dirty Howie]

Doug

Thanks for restatement of your position !!!!!!!!!!

Which is, if I understand ...... the NB are only capable of switching at one AFR...period, end of conversation. Therefore the WB must be faulty as it is in close proximity to the NB (in my case about a foot closer to engine)...and should read the same.


DH

[jalleva]

So what's the point in having a WB that reads incorrectly?

[Dirty Howie]

I spoke to the tech at PLX today. He agreed to read this thread. So if there are any questions that should be asked please post them up now


DH

[2000C-5]

Howie, here are some of my logs per request.

You will have to use my config files because I read my wideband throught the EGR since it is installed permanently in the car. These scans are a couple of months old because I have been messing with it lately. I changed injectors, and have been messing with the 02 switching points. I also have a Z06 intake I'm getting ready to put on, so I figured I would tune it all at one time.

[Dirty Howie]

Howie, here are some of my logs per request.

You will have to use my config files because I read my wideband throught the EGR since it is installed permanently in the car. These scans are a couple of months old because I have been messing with it lately. I changed injectors, and have been messing with the 02 switching points. I also have a Z06 intake I'm getting ready to put on, so I figured I would tune it all at one time.

Thanks....I will look it over soon ....busy weekend.

My WB is permanent too but doesn't go thru EGR ...... is that because you don't have the PRO ????? I wonder if that makes any difference in the WB readings.

[orange ss]

Subscribing.

[2000C-5]

Thanks....I will look it over soon ....busy weekend.

My WB is permanent too but doesn't go thru EGR ...... is that because you don't have the PRO ????? I wonder if that makes any difference in the WB readings.

It is because I don't have the Pro version and because I mounted it permanently, the only connection I have to make is to the OBD2 port. You have to connect your wideband to your interface each time.

It shouldn't make any difference in readings. The wideband output puts out 0-5v, the EGR reads 0-5v. You just have to set up a custom pid to change the voltage to AFR and log EGR. I have a write up in a sticky on the corvette forum in the scan and tune section. You have to add a wire to your PCM since we don't have EGRs, but you just poke it through a thin rubber seal. I have some of the correct pins with a short piece of wire on it, if you're interested, I can mail one to you.

[jknox]

I'll add my .02 here. I'm running my plx in through the egr position input. My controller is in the cab, in the center console. I ran it "controller only" for about a week before I got my y-pipe hacked up for another bung. What I found was interesting.

The controller is putting out a constant 2.33V without a sensor connected. This corresponds to 14.66:1. With the engine not running, I was getting roughly 2.27-2.31V from the ecm - not bad for an 8-bit a/d conversion. But I also found that with the engine running, I got a voltage drop that was roughly proportional to rpm - down to 2.18V by 5600 (AFR of 14.36).

After getting the sensor connected, I was watching to see if the same thing was occuring. Difficult to say the least, since really the only time you could tell was at the top end of a wot run by watching the display and then going back and comparing with the log. But after several times I was convinced that I still had it going on.

PLX's documentation is adamant about two things: the noise filter capacitor on the analog outputs and good grounds to wherever you're connecting it. I initially just had the analog out going straight into B55, and the ground was the small gauge wire they supplied going to a nearby body point. One thing I consider to be a design deficiency in the controller is the fact that there is only one ground carrying both signal ground and heater current, which is 2-3A. So I embarked on a ground wiring upgrade campaign. I had already found it necessary to upgrade the alternator cable when I went to a bigger alt for the e-fans. I went back and added 4ga battery cables from the alt bracket to the frame, and from the alt bracket to the body. I also rewired the power connector to the plx - it's now got a 12ga wire going to the body point.

Things looked a lot better after this but the readings seemed to me to lack consistency (for lack of a better way to describe it). So this weekend I went back and added in the capacitor. I picked an unused sensor reference on the ecm (you'd think egr reference would be available but no...). Don't remember what the function was listed as, but it's B27 (I think - notes are at home). Ohm'd out to the same as the ecm ground connections. Connected the capacitor from there to the wire running into the egr position.

So far things appear better. I'm currently redoing ve after setting the charge temperature bias table to 1 and I'm finally getting a little consistency going here. I'll better be able to tell in a few more days.

If it isn't working out there are really only a couple more things I can try. I can run a large gauge ground from the controller all the way to the ecm. Might be better, but still a pretty good potential for a ground offset. I can move the controller to the engine bay in close proximity to the ecm. I don't like this idea because there's absolutely no weather resistance to the controller design. Or I can bite the bullet and upgrade to a pro and keep the wires between the controller and interface very short.

I'll probably do the latter Since I haven't heard of anybody burning up their interface with a plx yet, I'm assuming that the internal ground traces are adequate for the heater current, and since the interface's a/d converters will reference the same ground that should get the rest of the grounding issues out of the way.

Does this help anybody out? I may not know jack about tuning, but I'm halfway decent at electronics...

[2000C-5]

I'll add my .02 here. I'm running my plx in through the egr position input. My controller is in the cab, in the center console. I ran it "controller only" for about a week before I got my y-pipe hacked up for another bung. What I found was interesting.

The controller is putting out a constant 2.33V without a sensor connected. This corresponds to 14.66:1. With the engine not running, I was getting roughly 2.27-2.31V from the ecm - not bad for an 8-bit a/d conversion. But I also found that with the engine running, I got a voltage drop that was roughly proportional to rpm - down to 2.18V by 5600 (AFR of 14.36).

After getting the sensor connected, I was watching to see if the same thing was occuring. Difficult to say the least, since really the only time you could tell was at the top end of a wot run by watching the display and then going back and comparing with the log. But after several times I was convinced that I still had it going on.

PLX's documentation is adamant about two things: the noise filter capacitor on the analog outputs and good grounds to wherever you're connecting it. I initially just had the analog out going straight into B55, and the ground was the small gauge wire they supplied going to a nearby body point. One thing I consider to be a design deficiency in the controller is the fact that there is only one ground carrying both signal ground and heater current, which is 2-3A. So I embarked on a ground wiring upgrade campaign. I had already found it necessary to upgrade the alternator cable when I went to a bigger alt for the e-fans. I went back and added 4ga battery cables from the alt bracket to the frame, and from the alt bracket to the body. I also rewired the power connector to the plx - it's now got a 12ga wire going to the body point.

Things looked a lot better after this but the readings seemed to me to lack consistency (for lack of a better way to describe it). So this weekend I went back and added in the capacitor. I picked an unused sensor reference on the ecm (you'd think egr reference would be available but no...). Don't remember what the function was listed as, but it's B27 (I think - notes are at home). Ohm'd out to the same as the ecm ground connections. Connected the capacitor from there to the wire running into the egr position.

So far things appear better. I'm currently redoing ve after setting the charge temperature bias table to 1 and I'm finally getting a little consistency going here. I'll better be able to tell in a few more days.

If it isn't working out there are really only a couple more things I can try. I can run a large gauge ground from the controller all the way to the ecm. Might be better, but still a pretty good potential for a ground offset. I can move the controller to the engine bay in close proximity to the ecm. I don't like this idea because there's absolutely no weather resistance to the controller design. Or I can bite the bullet and upgrade to a pro and keep the wires between the controller and interface very short.

I'll probably do the latter Since I haven't heard of anybody burning up their interface with a plx yet, I'm assuming that the internal ground traces are adequate for the heater current, and since the interface's a/d converters will reference the same ground that should get the rest of the grounding issues out of the way.

Does this help anybody out? I may not know jack about tuning, but I'm halfway decent at electronics...

I guess, since this is a big part of the equation, I should state how mine is hooked up.

- I am simming the narrowband with mine and both analog outputs have the noise reducing capacitors connected to them and grounded at the PCM.

- the ground for the PLX is on a chassis ground that is near the PCM ground (the PCM grounds to the passenger side head)

- I did not use any wires that came with the controller, I used bigger wire for all connections.

- my controller is mounted in the battery area, against the firewall. It is amazing how cool this area stays even with the hot engine bay temps


Oh yeah, JKnox, where in the hell is Chapmansboro?

[Dirty Howie]

jKnox

Thanks for throwing in ......

Do you have any logs ????

I was told the capacitor was NOT necessary. As the electronics dude do you think this would have any inpact on AFR readings between OL and CL ??

I was told that the voltage reading should be 2.35 with ignition on and that as the heater element warms up it should get leaner (higher voltage ?) and when the car is started the voltage should drop. That is all the help I got from them and obviously nobody from PLX posted to this thread.


DH

[S2H]

I'll probably do the latter Since I haven't heard of anybody burning up their interface with a plx yet, I'm assuming that the internal ground traces are adequate for the heater current, and since the interface's a/d converters will reference the same ground that should get the rest of the grounding issues out of the way.

Does this help anybody out? I may not know jack about tuning, but I'm halfway decent at electronics...

do not ground the wideband heater to the HPTuners Device
the traces are not designed for the heater ground of other devices to go thru it....they are designed for just the analog output of the controller device...