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Alternator Noise with MS2

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Hey guys,


I got the 240z running now which is great but getting some noise from the alternator.


I noticed this lately after my afr readings were different between the gauge and the ms2. I am using a lc-2. With the car off they read the same. With the car on they vary.


After seeing that result i decided to check all my grounds and moved them proper. I then unplugged my alternator and boom! They were both perfect. Plug it back in... bad again.


I decided it would be a good time to replace my alternator for a 280zx one which I did and still get the same result.


Has anyone had this issue and resolved it or do you just adjust your afr reading in ms2 to match the gauge?


Thanks for your help,



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General consensus from what i'd read is to match the MS2 to the gauge as you said.

My LC-1 had the exact same readout as my MS2 (until the gauge gave out on me).   I assume you have two separate grounds as stated in the instructions?  I was getting a lot of noise in my system until I realized I had removed a good body ground.   Replaced it once again and 95% of the noise is gone.

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Did you see my E-Mail that I sent the other day, regarding the EMI suppression capacitor that must be attached to the +12 V terminal on the alternator?  It is to reduce electrical noise.

Also, the LC-2 ground must go to the Intake manifold ( In your case ) .  You said Body above, but I think that may have been a Typo. Also, the Innovate ground wire has to go to a separate stud on the Intake manifold, not to the same stud as the ECU ground..... for the reason below.  


Innovate stupidly combines the Heater ground and gauge/sensor ground into one wire. Which is really dumb as the O2 heater wire is a high amperage draw and will can create a Voltage offset. Good manufacturers use a separate ground for the O2 Heater ground and that must be mounted separate from the ECU and regular AFR sensor ground. 


When you have a proper WB controller with two ground eyelets, the WB controller ground is " Star grounded " to the same point as the ECU ground to decrease voltage offset.


Interestingly, the Innovate wiring Loom does have a separate O2 heater ground. Then for some inexplicable reason they spliced them into one wire exiting the Loom. Some people have had success with unwrapping the loom, and soldering on a separate ground wire with eyelet for the O2 heater ground. Other people have reported great success with taking a BFH .... and beating the living S**T out of their Innovate WB controller. Your call... 









Edited by Chickenman
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I have read your email.


I have done all that your talking about. I moved o2 ground to intake on its own stud. There is a condenser on the alternator. I added a new ground strap from alternator. I put a capacitor inline to try to silence noise. Nothing worked.. only unplugging the alternator. I did notice that this is not very uncommon and I am only having issue with my o2 sensor. Nothing else is being affected. I will try moving my ms2 mounting position and see if that makes a difference but if not I am going to just adjust the afr voltage in tuner studio to match the gauge. I have done that now, but don't like masking a known problem.


Thanks for your help

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But adjusting the setting in Tuner Studio is not masking anything. It is a common electrical Calibration that is done with all AFR gauges and auxiliary outputs. The 14 point sevn article explained it in Technical terms. I think you're worrying a bit too much about the " Ca;libration "  


 Many, many industries dealing with electronics or electricity in general have to deal with voltage offsets. It is very very common to see adjustable voltage pots ( or digital  voltage regulators on  allsorts of electronic boards. The high end car audio industry deals with voltage offsets and ground loops all the time.  You should see what an electrical plant has to do with matching frequencies and voltages before tapping into a new Power grid. That's just the way it is. 


 You design your circuit to minimize the voltage offset. With proper ground procedures. That will take care of the big offsets. Then you fine adjust the difference in the software.


The alternator issue is a different matter though. It could very well just be old or faulty. A bad rectifier bridge in the alternator will introduce electrical moise into the whole cars electrical system. Worn brushes or a worn commutator. will also create noise. A failing alternator can generate a lot of AC ripple. Which is very bad in a DC circuit. Especially for modern day electronics with digital micro processors that operate on very low voltages ( some operate with millivolts ).


Edit: Even a new re-manufactured alternator can put out excessive  AC ripple. Depends on how good the electronic components are inside. Rectifier bridge's and   Voltage Regulator circuits can be utter pieces of crappola on " Off Shore "  made Alternators. It can be a crap shoot....  


Come to think of it, didn't you mention that your charging voltage was pretty low.? That is one of a failing alternator. Consider the Maxima 80 Amp internal upgrade. Newer " Small frame " design,  that is much more efficient than the old 280zx  Internal regulator models. The Maxima alternator can crank out 50 amps at just 1,000 rpm .


Just my .02c. Others may have some incite to this as well. Good Luck with your project.

Edited by Chickenman
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And as I mentioned before. Innovate WB controllers seem to be  very sensitive to voltage offsets and electrical noise. ( EMI ) More so than other manufactures. Lots of information collaborating that on numerous forums. The actual design of the WB controller is not up to the standards of other manufacturers 


I think an alternator change would be a good idea, to solve this particular issue. 



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I have got the 280zx alternator cranking out 13.5 volts. I have made the adjustments in Tunerstudio and will just be okay with it as no other reading is off besides the o2 reading. Also I have no problems getting into high rpms.


As a final test I will be moving the ms2 away from other wiring and see the results. If nothing changes I will just be satisfied. I will look into the maxima alternator.





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Matt: Ok now I'm officially confused.  Direct grounding of the ECU to the negative Battery terminal  goes against recommendations by other Manufacturers and your own information. Voltage impedance from the Starter cranking ( huge amperage draw ) can damage components in the ECU if you  connect it directly to the Negative Battery terminal. Especially if you  have a bad Chassis ground. And these are 40+  year old cars.  And if you have a bad starter ( shorted commutator or  excessively high draw ) you can blow sensitive Microelectronics in the ECU. 


Shane:  I thought you said you had grounded the ECU to the Intake Manifold. And the Innovate WB controller to the Intake manifold but in a different point.  Was that a Typo about having the ECU grounded to the Chassis?  And I thought we went over the issue issues of the secondary ground in the Nissan Optical distributor requiring that the ECU ground be attached to the engine  so that you have the smallest ground Loop in the Ignition circuit.  Preferably Intake Manifold on our engines. As per factory design 

Edited by Chickenman
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Matt" Here is the documentation direct from MS Extra showing proper grounding schemes to the Engine  Cylinder Head or Block And repeated by other manufacturers. 


3.2 Grounding (Earthing) Schemes

 Implementing a correct grounding scheme is critical to a successful Megasquirt install. 

Connecting sensors to the wrong ground, using corroded ground points or dubious original wiring are sure-fire 
ways to give you a headache.

There are two key rules:

1. All sensors must ground at the Megasquirt

2. Ground the Megasquirt at the engine block/head using both available ground wires.


When a current flows through a wire there is always a voltage drop, the bigger the current, the bigger the drop 
(this is ohm's law.) During cranking there is a very large current flowing through the ground strap from battery to 
engine and perhaps a few volts may be dropped across it. Even during running, a number of amps will flow 
through the Megasquirt grounds to the engine. 

The sensors (coolant, air temp, throttle position, wideband, tach input) all use low current, low voltage signals. 
The Megasquirt measures the voltage from the sensor and converts it into a temperature, position etc. reading. 
If that sensor is grounded to anything other than the Megasquirt itself, then that input voltage will be altered by 
any external voltage drops. For a sensitive measurement such as AFR (lambda) this can be a real problem. All 
good wideband controllers offer a high-current ground (connects to engine) and a sensor/signal ground 
(connects to Megasquirt.) 

Tach input (e.g. crank, cam sensors) will be even worse - they can show false or missed teeth and cause sync-
loss due to the ground voltage difference.

The following two diagrams illustrate good and bad wiring schemes showing where the troublesome voltage 
drops are created and how that would cause sensor readings to be garbage.

Edited by Chickenman
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21 hours ago, madkaw said:


Might need to elaborate on this statement 

In my experience, good chassis grounds are usually bad, and bad chassis grounds are horrible.


A chassis ground may look like a nice thick piece of metal running straight to the battery. But in practice, there's often a fair amount of rust, spot welds with poor contacts, and possibly sections where the current is trying to get through paint and rusty screws in the path of current that you try running through the chassis.


So grounding the ECU to the battery is the best option for grounding.

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Don't overlook that when the engine is running and the alternator spinning that the bulk of the current is actually flowing through the alternator circuit.  The battery is actually a low current draw.  So it's the alternator charge wire and ground that might be most important.  The battery is often thought of as the primary power source but when the car is in use, it's not really.

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