Apexi's Stupid Way Of Earthing

[3LGODZILA]

OK were getting a little electrical here. and because the contact page on the apexi site is blank, i don't know who to contact, if anyone can point me in the right direction...i'm listening

anyone who's installed a SAFC or AVC-R or something similar will know what i'm on about, when u hook up the earth wire apexi specifically says to join 2 grounds to 1 wire and VERRRRY important that one comes before the other, why is this? does any1 have a clue?

here's my dilemma, on my r33 i had both installed. the earth wire for the SAFC was different to the earth wire on the AVC-R. BUT now i wanna install both on an RX-7 and the earth wire for the SAFC is the same wire as on the AVC-R, in my head yeah i know how to wire it up BUT since apexi is sooo anal about getting 1 wire before the other and it must be at least 1 cm apart from each other i'm thinking they made the earth on separate wires on the r33 for the reason of running both a SAFC and AVC-R, i just cant see why they didn't do it like that on the RX-7?? unless the RX-7 has 1 main ECU earth and the reason they did it like that on the r33 was to spread out the solder joins. i dunno.

Edited August 12, 2010 by jimmys-33T

[paulr33]

not aware of any issues? earth is...... earth

houses do it, sparkies do it, cars do it

just join where ever you like

perhaps it's their insurance policy, they can turn around and say, see nah we told you not to join them together, they should have been 2cm apart, its your installers fault

[GTScotT]

I dont know the actual reasoning behind Apexi's decision here, yet keep in mind electrons travel through the earth (not the positive). A good earth is CRUCIAL in all applications.

I think the difference in manuals is an oversight, and the anal document is the correct one to follow.

GL

[3LGODZILA]

not aware of any issues? earth is...... earth

houses do it, sparkies do it, cars do it

just join where ever you like

perhaps it's their insurance policy, they can turn around and say, see nah we told you not to join them together, they should have been 2cm apart, its your installers fault

so u've installed an safc or something and grounded the wires how u normally would and it works fine?

i can see what ur saying, its just that they're so anal about it they have like 3 diagrams on it ffs, i didnt have the balls to try and do it my way to test it so i just followed the guide. if someone can confirm that they've earthed it normally then thats good enough for me

[DVS JEZ]

earth is earth for most power applications, but when it comes to signals such as air flow or wideband 02 sensors etc it is very important to keep the earths to a single lug to help minimise interference and foriegn signals

[Kinks]

not aware of any issues? earth is...... earth

houses do it, sparkies do it, cars do it

just join where ever you like

Even though for all practical purposes you're right, the electrical engineer in me is cringing at your simplification of the concept of earthing

The reason they go into detail is because one of the ground eyelets has more current going through it than the other, or is more sensitive to the ground potential (or noise). It will still work fine if you hook them up the other way around, but in a dark back room somewhere a japanese engineer dies a little inside when you connect it the wrong way. Please, think of the (excessively anal) engineers

[Kinks]

earth is earth for most power applications, but when it comes to signals such as air flow or wideband 02 sensors etc it is very important to keep the earths to a single lug to help minimise interference and foriegn signals

Yep, star earthing is vital in audio power amplifier design as well. Ground loops are no fun.

[Duncan]

interesting. i guess that's why the r35 systems runs seperate eyelets for pretty much every wire, all to common studs. stuffed if I could work out why, it must be very sensitive

[rob82]

NO NO NO. When it comes to sensor signal grounds there is a big difference than chassis ground. The AVCR is just driving a solenoid so using the chassis as a GND is fine. When it comes to SAFC or any device that is connecting to a signal voltage then you must use the sensor GND as its most likely at a different potential to chassis GND. On most cars it is HIGHLY critical that device manufacturer has matched the input impeadance of the aftermarket device to that of the std ECU and they will almost all use sensor GND as a reference NOT CHASSIS GND.

[3LGODZILA]

NO NO NO. When it comes to sensor signal grounds there is a big difference than chassis ground. The AVCR is just driving a solenoid so using the chassis as a GND is fine. When it comes to SAFC or any device that is connecting to a signal voltage then you must use the sensor GND as its most likely at a different potential to chassis GND. On most cars it is HIGHLY critical that device manufacturer has matched the input impeadance of the aftermarket device to that of the std ECU and they will almost all use sensor GND as a reference NOT CHASSIS GND.

are u getting positives and negatives mixed around? like how sensors use a +5volts not +12 ?

yes the signal wire is a variable resistance to EARTH, ie straight to ground, therefore every ground is the same.

and im not gonna chuck and eyelet on the safc ground wire and just ground it, im still gonna go off the earth wire on the ecu, its just ive gotta do that with the avc-r and safc so ill need 4 wires hooked onto the 1 earth. im guessing they did it differently on the r33 to keep it neater and the rx-7 ecu must just have 1 main earth, its got others but i think they like to have an independent earth for each injector. but yeah id just be guessing i dont know much when it comes to the internals of the ecu

[MBS206]

are u getting positives and negatives mixed around? like how sensors use a +5volts not +12 ?

yes the signal wire is a variable resistance to EARTH, ie straight to ground, therefore every ground is the same.

and im not gonna chuck and eyelet on the safc ground wire and just ground it, im still gonna go off the earth wire on the ecu, its just ive gotta do that with the avc-r and safc so ill need 4 wires hooked onto the 1 earth. im guessing they did it differently on the r33 to keep it neater and the rx-7 ecu must just have 1 main earth, its got others but i think they like to have an independent earth for each injector. but yeah id just be guessing i dont know much when it comes to the internals of the ecu

No, you can get a floating "earth" IE, your earth can actually be at 7Volts when compared to the negative on the battery.

The sensor runs on a 5 Volt different between its positive, and it's negative.

[3LGODZILA]

i was always taught earth was earth. for example hooking up voltage reducers only the positive goes through the neg isn't touched.

not doubting you or anything, but yeah might have a chat to the old timer at my work he seems to know everything lol