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..When you start your engine, do you momentarily notice a belt squeal? If so, you might consider turning on the the 12V to the resistor only after the engine is running. Only a theory, havn't tried that yet.
It would be cool if you could try this and get the Holley community straightened out with the 2 pin alternator. Hell, it they sponsored me, I'd swap my AEM infinity and drop in the Dominator is a heartbeat.
I actually just posted a video on IG showing the Holley dash during cold start. I get belt squeal only after it has rained (I have a hole in my hood....LOL). In the video you can see that it takes a moment for the voltage to rise after the engine starts. I can try reconfiguring the output to the L terminal to come on once engine hits say 400RPM. I am not sure what you think that will do...
Originally Posted by LSswap
Andrew,
Do you have a scope? Even if you don't install this alternator, it would be great to connect the resistor and zener as above, to one of your free PWM+ ports and look at the waveform. If it looks like a 5 volt square wave, then it is highly likely to work with the 2 pin alternator.
I do not have a scope or a 2 wire alternator...LOL
I wouldn't have to change the wiring around. I can just reconfirm the wire going to the L terminal to be PWM, via software. The alternator that my LH8 had on it originally was a 2 wire, but I did not receive it with my engine. If anyone around Tuscaloosa, AL has parts and wanted me to do some testing, I would be happy to...LOL
Sorry, you are incorrect. The voltage will adapt to load as things go on and off. The PWM to the alternator is like a command... "Give me exactly 14.5 volts!!!" The regulator inside the alternator has it's own separate PWM to control the field coils, to automatically adjust everything internally so it puts out the commanded voltage no matter what. The only time it won't be able to maintain the commanded voltage, as with any other alternator is when it's turning too slow.
Without an external sense wire it can only regulate the voltage at the alternator output lug. So yes, constant volts at the alternator lug but varying load current will cause voltage drops and fluctuation through the wires. Same as a one wire set up.
It would be a pretty simple matter to hook up an arduino to vary the PWM signal and regulate the voltage at the fuse box.
Oh and by the data sheet I'm reasonably certain you can power it off 12V directly.
Shoot. Just saw your arduino post. Now have it sense the voltage at the fuse box and adapt the signal to maintain constant volts.
Yep. very easy to do. I kept it simple so as to not scare people away. Looking at a sense voltage and compensating is a few extra lines of code.
Then while you're at it, add code to see if the engine is running. Then check the voltage before the engine starts to determine what condition the battery is and compensate with extra charge for a while........
Having a programmable control give you ultimate flexibility. The question is where do you stop. I haven't learned how to do that. I'm up to 13,400 lines of code in my project.
Just an update. I've been using the 2 wire alternator in my 77 Vette for a while now. Works great! when I first start the car, my computer commands it to put put a very low voltage so as not to put extra load on the starter or cold engine. Then brings it up to 14.1 volts over time.
This is very informative. Thanks for your work. I read on the 67-72 chevytrucks.com thread. A post by Hartrod also got this type of alternator to work with some re-work on the wiring.
This is very informative. Thanks for your work. I read on the 67-72 chevytrucks.com thread. A post by Hartrod also got this type of alternator to work with some re-work on the wiring.
Thanks, I tried finding that article, had no luck.
There are ways to wire up either the PWM+ or PWM- port on the Holley, but it will be easier to use the PWM+. 5V zener Diode
The zener diode is 35 cents quantity 1.
Here's how I would try it. Keep in mind I've never seen or smelled a Holley. I'm fairly confident it should work.
I am not sure, but, depending on the Holley system they can do both PWM+ or PWM-. The TerminatorX can only do PWM- while the HP and Dominator can do either.
Here is how I would try it connecting to PWM-. Please keep in mind that I can't test this.
The L pin is the command voltage pin. A 5V PWM signal would be sent from the Holley at a frequency of 128hz. Here are the PWM duty cycles I would try for PWM-. They are the opposite of PWM +.
90% = 11.0 V
80% = 11.56 V
70% = 12.12 V
60% = 12.68 V
50% = 13.25 V
40% = 13.81 V
30% = 14.37 V
20% = 14.94 V
10% = 15.5 V
LSswap, I'm pulling my hair out and I'm hoping you can help.
I've got a 2006 Pontiac GTO with the 2-wire pwm alternator with the overrun clutch. I'm running a Holley dominator but the e40 is still running behind the scenes to control a/c, trans, alternator, dash, etc. BCM is still in place as well and the battery is in the trunk. I have removed a number of the engine wiring that was, or I believe was, not needed. My problem is, I never see over 13.7 volts, and that is only for a few seconds after start up, most times it's low to mid 12vdc. Last night, during a highway pull, it dipped below 12vdc according to the Holley datalog.
According to the tech 2, at idle after first start up, the ecm is commanding ~50% duty cycle and I get mid-13.3-13.5 vdc.
Alternator has been tested. Battery has been tested. Both tested good.
I've also bought the signal generator from this thread and a pocket o-scope as well. I cut the signal wire from the PCM and wired in the signal generator and set it to 128hz and 50% DC to start. I verified the settings with the pocket o-scope. Started the car up and saw 13.6-7 vdc. I increased the duty cycle 10% at a time, up to 90 with no change in voltage. I then lowered it down to 10%, again with no change in voltage. I've used both 12vdc and 5vdc as source voltage for the signal generator.
I wired the factory PWM wire back up and tapped it with the o-scope. The o-scope showed a freq of 250Hz, not 128. I tried the signal generator at 250Hz as well, and again, no change in voltage.
What am I missing? Why cant I get the alternator to increase or decrease voltage?
Last edited by wicked_95z; 10-24-2019 at 08:42 PM.
LSswap, I'm pulling my hair out and I'm hoping you can help.
I've got a 2006 Pontiac GTO with the 2-wire pwm alternator with the overrun clutch. I'm running a Holley dominator but the e40 is still running behind the scenes to control a/c, trans, alternator, dash, etc. BCM is still in place as well and the battery is in the trunk. I have removed a number of the engine wiring that was, or I believe was, not needed. My problem is, I never see over 13.7 volts, and that is only for a few seconds after start up, most times it's low to mid 12vdc. Last night, during a highway pull, it dipped below 12vdc according to the Holley datalog.
According to the tech 2, at idle after first start up, the ecm is commanding ~50% duty cycle and I get mid-13.3-13.5 vdc.
Alternator has been tested. Battery has been tested. Both tested good.
I've also bought the signal generator from this thread and a pocket o-scope as well. I cut the signal wire from the PCM and wired in the signal generator and set it to 128hz and 50% DC to start. I verified the settings with the pocket o-scope. Started the car up and saw 13.6-7 vdc. I increased the duty cycle 10% at a time, up to 90 with no change in voltage. I then lowered it down to 10%, again with no change in voltage. I've used both 12vdc and 5vdc as source voltage for the signal generator.
I wired the factory PWM wire back up and tapped it with the o-scope. The o-scope showed a freq of 250Hz, not 128. I tried the signal generator at 250Hz as well, and again, no change in voltage.
What am I missing? Why cant I get the alternator to increase or decrease voltage?
wow, I feel your pain.
Are you sure you are on the correct pin? Both alternator pins contain PWMs. One if from the ECM to the alternator, the other is from the alternator to the ECM. Did you check the PWM on both pins?
Also, any possibility your overrun clutch is slipping?
BTW, I only use a 5V source for the alternator PWM. I have no idea if 12 will damage the regulator or not.
Understood. Well, I script kiddied your code and stuck it in a Nano I bought from Ebay for $6.00. Designed and 3d printed a small box to enclose it on the firewall. Still a ways off from starting the motor to see if it works.
Are you sure you are on the correct pin? Both alternator pins contain PWMs. One if from the ECM to the alternator, the other is from the alternator to the ECM. Did you check the PWM on both pins?
Also, any possibility your overrun clutch is slipping?
BTW, I only use a 5V source for the alternator PWM. I have no idea if 12 will damage the regulator or not.
I'm fairly certain I was on the correct pin, the grey wire. On the GTO, the Duty Cycle Signal (grey wire) goes to pin F on alternator and Gen On Signal (org wire) goes to pin L on the alternator.
When I put my scope on the grey wire, it's a 250Hz signal, not the 128 I expected. I tried both freqs on the signal generator and no change. I even tried 500Hz that is supposedly used on certain SIlverados. I've tried both 12v and 5 v. The clutch seemed fine by hand but I welded the pulley just in case, no change.
I did notice that your drawing shows the PWM signal going to the L terminal on the alternator.
Last edited by wicked_95z; 11-01-2019 at 09:05 PM.
12-22-2018, 04:38 PM
