Groundings: PE/XPE ...FYI
12-30-2004 | 12:48 PM
#1
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Senior Member
Joined: Dec 2004
Posts: 4,323
From: EU Scandinavia
Groundings: PE/XPE ...FYI
Just got the 'ground breaking' picture ready on my cardomain page, just for you all: Its on 3gen Maxima J30 VG30E !. Here it is, take a look...
Groundings:
Electrical devices need supply voltage. The current flow thru the device produces the energy for it. Thereby the flow needs a place to go. This is source to drain the current, is commonly called the ground.
Electronic devices are suspect to interference from spikes produced by powerful devices, like starter etc. Thereby they typically are isolated from this ground, and have their own gnd 'source'.
A car has battery (&alternator) and its negative pole -the gnd- is strapped to chassis and engine block. Typically this is enough on new and clean products. However, oxidation between various parts, result in disconnection and/or resistance inhibitng current flow.
The extra grounding straps ensure grounding between chassis and the engine parts. One part is the exhaust pipe, typically it has to be grounded cause the O2 sensor & other possible interference problems.
Extra grounding from chassis to alternator is imperative. Manufacturers leave this device to ground itself just via its support bolts which will oxidize, question is just how fast. Oxidation will break this ground, and ruin battery as it will never become fully charged. Add one strap between alternator body and vehicle chassis - all connection points clean & electric conducting grease added.
In electrical devices, adding extra groundings will never do harm, only increases reliabiltity. In electronics one has to think also radio frequencies: a loop forms an antenna which may induce problems to the low voltage electronics devices. Thereby all electronics grounding cables networks must have to form a tree [never a loop].
Anyways, I think cars (not just maxima) have poor poor electronics design as default (used to be R&D ...) and they have inherited systems designed for climate controlled rooms within one small box. All longer distances in computing world use special drivers with CRC & other error correcting signal transmission methods, these are nowhere to be seen in cars: extra long cabling for DC supply plus the digital/analog signal to noise -ratio would be laughable if I could stop crying... Dunno understand why cars even work...
Typically you lose one volt per meter on those lousy thin car wires. Doubling or quadrupling wiring thickness is always beneficial.
Electrical GND kit is important; but its only half story... and maybe even not that: ECU driven things get their ELECTRONIC-ground AND + supply via ECU thinny skinny wires. AND ECU & 'all' ECU controlled sensor wirings are isolated from Electrical chassis ground like tranny box.
Industrial applications typically speak/utilize of PE=electronics groundand XPE=electical chassis ground. I suspect Nissan designers have no info (!) of these basic grounding principals: at least knock sensor and injectors seem to ground to PE, not into ECU's XPE as they should...
The next picture outlines chassis ground PE and how all computers ECU, ABS, etc. are connected to there. However, all their sensors get grounding XPE only via the computer itself. The sensors should never ! be connected to PE, which sadly is not the case in all Maxima sensors...
THEY'RE SEPARATE:
PE shields from inductive pulses in the chassis and its mechanical parts, but will not help current flow in a computer driven device circuitry which does (never!?) ground to chassis. XPE is used for the electronics signal processing, and the nissanthinny wires provided for them is a black sinkhole... Not to mention those poor voltage (0-5V) levels [no driver circuits =cheap] used in car computers. All these grounding issues practically mean that ECU electronics is fighting always on the starving edge, and at first sign of oxidation (will come, when?) will kill u car, blink all lights with all ECU codes...
XPE ground = computer signal wires should be shielded. This shield [not seen in car applications] should be grounded into PE. (did not add that to the pic, would have been too crowded)
Last word: If you have a chance to triple all ECU wires in thickness plus shield them, do so!
Groundings:
Electrical devices need supply voltage. The current flow thru the device produces the energy for it. Thereby the flow needs a place to go. This is source to drain the current, is commonly called the ground.
Electronic devices are suspect to interference from spikes produced by powerful devices, like starter etc. Thereby they typically are isolated from this ground, and have their own gnd 'source'.
A car has battery (&alternator) and its negative pole -the gnd- is strapped to chassis and engine block. Typically this is enough on new and clean products. However, oxidation between various parts, result in disconnection and/or resistance inhibitng current flow.
The extra grounding straps ensure grounding between chassis and the engine parts. One part is the exhaust pipe, typically it has to be grounded cause the O2 sensor & other possible interference problems.
Extra grounding from chassis to alternator is imperative. Manufacturers leave this device to ground itself just via its support bolts which will oxidize, question is just how fast. Oxidation will break this ground, and ruin battery as it will never become fully charged. Add one strap between alternator body and vehicle chassis - all connection points clean & electric conducting grease added.
In electrical devices, adding extra groundings will never do harm, only increases reliabiltity. In electronics one has to think also radio frequencies: a loop forms an antenna which may induce problems to the low voltage electronics devices. Thereby all electronics grounding cables networks must have to form a tree [never a loop].
Anyways, I think cars (not just maxima) have poor poor electronics design as default (used to be R&D ...) and they have inherited systems designed for climate controlled rooms within one small box. All longer distances in computing world use special drivers with CRC & other error correcting signal transmission methods, these are nowhere to be seen in cars: extra long cabling for DC supply plus the digital/analog signal to noise -ratio would be laughable if I could stop crying... Dunno understand why cars even work...
Typically you lose one volt per meter on those lousy thin car wires. Doubling or quadrupling wiring thickness is always beneficial.
Electrical GND kit is important; but its only half story... and maybe even not that: ECU driven things get their ELECTRONIC-ground AND + supply via ECU thinny skinny wires. AND ECU & 'all' ECU controlled sensor wirings are isolated from Electrical chassis ground like tranny box.
Industrial applications typically speak/utilize of PE=electronics groundand XPE=electical chassis ground. I suspect Nissan designers have no info (!) of these basic grounding principals: at least knock sensor and injectors seem to ground to PE, not into ECU's XPE as they should...
The next picture outlines chassis ground PE and how all computers ECU, ABS, etc. are connected to there. However, all their sensors get grounding XPE only via the computer itself. The sensors should never ! be connected to PE, which sadly is not the case in all Maxima sensors...
THEY'RE SEPARATE:
PE shields from inductive pulses in the chassis and its mechanical parts, but will not help current flow in a computer driven device circuitry which does (never!?) ground to chassis. XPE is used for the electronics signal processing, and the nissanthinny wires provided for them is a black sinkhole... Not to mention those poor voltage (0-5V) levels [no driver circuits =cheap] used in car computers. All these grounding issues practically mean that ECU electronics is fighting always on the starving edge, and at first sign of oxidation (will come, when?) will kill u car, blink all lights with all ECU codes...
XPE ground = computer signal wires should be shielded. This shield [not seen in car applications] should be grounded into PE. (did not add that to the pic, would have been too crowded)
Last word: If you have a chance to triple all ECU wires in thickness plus shield them, do so!
12-31-2004 | 01:42 AM
#2
dude, its not worth my time to go and do all that.
I made a ground kit. Still need to get wire for the altenator but other than that its complete and covers all of the engines common grounds.
My car gets excellent gas mileage with a tank that will not hold pressure, an old **** O2 sensor that is from a turbo VE, and a bunch of other crap. Maybe I'll ohm the exhaust to the battery or body to see the resistance and see if adding another cable helps at all, but that will probably be at about the same time I get a new O2, which isnt any time soon
good post though, it's just not practical for me to go through and remake my entire wire harness out of 14/16/whatever gauge sheilded wires :-/
I made a ground kit. Still need to get wire for the altenator but other than that its complete and covers all of the engines common grounds.
My car gets excellent gas mileage with a tank that will not hold pressure, an old **** O2 sensor that is from a turbo VE, and a bunch of other crap. Maybe I'll ohm the exhaust to the battery or body to see the resistance and see if adding another cable helps at all, but that will probably be at about the same time I get a new O2, which isnt any time soon
good post though, it's just not practical for me to go through and remake my entire wire harness out of 14/16/whatever gauge sheilded wires :-/
12-31-2004 | 03:30 AM
#3
Thread Starter
Senior Member
Joined: Dec 2004
Posts: 4,323
From: EU Scandinavia
I wanted to highlight the gnd principal in case of mods, and the idea that when rewire is needed, thicker wires if possible should be used... Its better to keep electronic groundings separate. Err... which is not really what nissan does...
Tranny solenoids might ? get boost from thicker wires [measurement from solenoids or near are needed - while driving], dunno if any other thing would be noticeable.
Typically all car manufacturers are lost in the grounding principals. Thats because their core field has not before been electronics. It is not my invention, but generally known fact that wrong groundings makes that wrong wiring an antenna loop calling for trouble...
Black Helicopters in the night:
Who knows: state traffic dpt here few years ago were investigating an instance where ABS brakes on several vehicles, cars & buses were lost on certain 5mile radius 'spot' for a while. Was that some outside energy field (passing fighter plane, radar station etc) affecting the vehicle elctronics?
Tranny solenoids might ? get boost from thicker wires [measurement from solenoids or near are needed - while driving], dunno if any other thing would be noticeable.
Typically all car manufacturers are lost in the grounding principals. Thats because their core field has not before been electronics. It is not my invention, but generally known fact that wrong groundings makes that wrong wiring an antenna loop calling for trouble...
Black Helicopters in the night:
Who knows: state traffic dpt here few years ago were investigating an instance where ABS brakes on several vehicles, cars & buses were lost on certain 5mile radius 'spot' for a while. Was that some outside energy field (passing fighter plane, radar station etc) affecting the vehicle elctronics?