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Discussion Starter #1
I have a 2011 Range Rover Supercharged (full size) and for like 5-6 years I didn't have any problems but now when I am accelerating, the vehicle slightly jerks when the subwoofer hits. If I am driving at a constant speed, you can feel the vehicle lose some power as if you let off the gas and on again very quick or quickly tapped the brake; you can also see the bump in the RPM on the gauge as well. When climbing a hill, it is very noticeable too.



We first thought it was an old battery problem and replaced the battery; that didn't help. Next, we found out the alternator had issues and that was replaced with a new one; that didn't help with the jerking.



I am about to purchase a new capacitor, likley a 3 farad and installing that to see if it gets better.



Does anyone have any idea where the problem might be?



The set up is as follows:



2 Alpine Type X suboofers

2 Alpine PDXM12 1200W amplifiers

1 Farad Pheonix Gold Capacitor



Thank you.
 

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how loud is it when this happens?
any way to monitor voltage?

good possibility the ECU is browning out?

caps are worthless, wont help the problem at all, unless you put the cap on the electronic part that is being effected by the voltage sag :D
 

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Discussion Starter #3
It is at higher volumes that this happens.. when it is turned down, then it is okay.. The louder it gets, the stronger it jerks.

How should I test the voltage?

I am not sure how to tell if the ECU is browning out..
 

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It is at higher volumes that this happens.. when it is turned down, then it is okay.. The louder it gets, the stronger it jerks.

How should I test the voltage?

I am not sure how to tell if the ECU is browning out..
if you were to play a really strong tone, like 40hz, really loud. can you kill the vehicle for a longer time? try to isolate if you have a loose connection or if it is literally pulling down the voltage and making the electronics freak out.

does it do it if you are sitting still?

the only real way to monitor the voltage in real time would be an oscope.
 

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Discussion Starter #7
If I play a hard constant tone, it won’t kill the vehicle out..

The connections are all good and tight..

Even if the voltage was dropping when the bass hits, what am I left to fix/upgrade? Keep in mind, it works fine with this exact set up for several years and the battery and alternator were replaced..
 

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Discussion Starter #8
When sitting still, you can very slightly see the RPM nudge but not nearly what it’s like while driving or accelerating.. you would think it would be less noticible while driving since the RPM is higher and alternator is probably producing more..
 

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If I play a hard constant tone, it won’t kill the vehicle out..

The connections are all good and tight..

Even if the voltage was dropping when the bass hits, what am I left to fix/upgrade? Keep in mind, it works fine with this exact set up for several years and the battery and alternator were replaced..
I meant a connection of the vehicle electrical system. since this has just started, something changed.

something to try, leave the stereo off and find a crazy bumpy road and drive fast on it and see if the impacts and vibrations of that will make it cut out.
 

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When sitting still, you can very slightly see the RPM nudge but not nearly what it’s like while driving or accelerating.. you would think it would be less noticible while driving since the RPM is higher and alternator is probably producing more..
ya, but at higher RPM and WOT, you are demanding more of the ignition system and if that is the problem you would see it more then than at idle.
 

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Discussion Starter #11
I would think that Land Rover checked the vehicle electrical system when they replaced the alternator.. they looked into this issue as well since I still have warranty on it.. but they blamed the sound system since they can’t replicate it with the sound system off.. something to look at perhaps..

Driving on bumpy roads does not cause anything to clip out.. even cranking the factory sound system very high with the aftermarket amps switched off doesn’t lead it to jerk the vehicle at all.. it has the Harmon kardon 19 speaker upgraded sound system..
 

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You are running 2400 watts RMS (2 Alpine PDXM12 1200W amplifiers) on stock electrical? I would say that is your issue. Another 2nd battery may help but a bigger alternator may be the only save there.

Check the voltage at the amplifier while the subs are playing at the volume that this happens (vehicle sitting idle) and if it dips below 13 volts than your stock electrical cannot keep up, assuming you have good grounds and connections with good solid power and ground wiring too. Stock electrical voltage should be between 13.2 volts and 14.4 volts and most are around 13.8 volts.
 

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You are running 2400 watts RMS (2 Alpine PDXM12 1200W amplifiers) on stock electrical? I would say that is your issue. Another 2nd battery may help but a bigger alternator may be the only save there.

Check the voltage at the amplifier while the subs are playing at the volume that this happens (vehicle sitting idle) and if it dips below 13 volts than your stock electrical cannot keep up, assuming you have good grounds and connections with good solid power and ground wiring too. Stock electrical voltage should be between 13.2 volts and 14.4 volts and most are around 13.8 volts.
I would agree except he did this for 5 years with no issues and he recently replaced the battery and the alt.

IMHO, something is loose.
 

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I would agree except he did this for 5 years with no issues and he recently replaced the battery and the alt.

IMHO, something is loose.
O-missed that minor detail. Surprised he didn't have an issue on stock electrical from the start. yeah, that has to be a connection/ground issue somewhere between the alternator, battery, and amplifiers.
 

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Your alternator is loading down the engine when it's in full field. Same thing that happens when the a/c compressor kicks on and off. I know when the alt in my car is under extreme load I have to almost floor the car to keep acceleration normal (although I'm also hauling around ~1000 extra lbs of gear and it's a Neon).

As for why it's happening you need to monitor voltage, preferably from at least a couple points. You can monitor "car" voltage by measuring at the battery terminals when the system is turned up and the electrical is under load. You can also use something like a voltmeter that plugs into your cig lighter for when you're driving around town. It would also be good to measure at the amp's + and - terminals under load to make sure it closely matches the same readings you see at the battery.

If you are dropping below 12v with any regularity you need to turn down the gain on your sub amps.

It could also be some random loose connection that gets jostled enough to have intermittent contact when the bass shakes the car, but check your voltage first.
 
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My g/f had an Isuzu Rodeo that did something similar before the fuel pump went out. New fuel pump went in and it never did it again. I’m not saying that’s for sure your issue, but stranger things have happened. Just have the dealership put in a new one and that’ll tell you if that’s the problem or not. Fuel pump on a Range Rover can’t cost more than 3, maybe 4 thousand bucks to swap out, right? Bam, problem solved.
 

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Discussion Starter #17
I regards to it being a weak alternator or not enough battery power, again, it worked flawlessly for several years with the stock equipment.. the battery was replaced with a better battery than original as well when I replaced it, so in a better position than original..

In regards to the fuel pump comment.. oddly enough, my truck is going in on Monday to have something done related to fuel.. I had a “check fuel cap” light come on recently (which stopped coming) then the yellow check engine light which stays on.. they mentioned something about fuel pressure releasing or something.. however, that only came on a few weeks ago and this problem started about a year ago.. fingers crossed that it will fix the problem but I doubt it lol

P.s. spark plugs were replaced recently as well..
 

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Your alternator is loading down the engine when it's in full field. Same thing that happens when the a/c compressor kicks on and off. I know when the alt in my car is under extreme load I have to almost floor the car to keep acceleration normal (although I'm also hauling around ~1000 extra lbs of gear and it's a Neon).

As for why it's happening you need to monitor voltage, preferably from at least a couple points. You can monitor "car" voltage by measuring at the battery terminals when the system is turned up and the electrical is under load. You can also use something like a voltmeter that plugs into your cig lighter for when you're driving around town. It would also be good to measure at the amp's + and - terminals under load to make sure it closely matches the same readings you see at the battery.

If you are dropping below 12v with any regularity you need to turn down the gain on your sub amps.

It could also be some random loose connection that gets jostled enough to have intermittent contact when the bass shakes the car, but check your voltage first.
^This^ looks correct. However let's look at the other causal mechanisms.

The fuel pump pressure has some voltage dependancy, and if it has a regulator then the injectors still have an opening and closing response that is voltage dependant. (The injector is a linear motor just like a speaker).

Most Fuel Injection (FI) systems have some 1/pressure^2 factor for fuel pressure and tables for "injector opening dwell time" versus voltage.

If the fuel pressure was actually low, then a "fuel log" is a capacitor of sorts for the fuel pressure. That would help for transients, but would not work if the whole system is being pulled down.

We should assume that the injectors tables are used and implemented correctly... as all EU4 emissions require that as well as humidity sensors etc.

Another mechanism is the spark coils. And they also have a dwell value that is voltage dependent. But they usually either miss or spark... So we can probably discount that.


In any case there are mechanisms which are related to variable voltage that can (and should already) be used to as strategies to account for input voltage.

If the voltage going low is correlated with the loss of power then finding the mechanism is worthwhile.

We think it is a case of the voltage going low, but we do not yet have proof that the voltage is going low.


If the battery and/or alternator was changed and then the problem reared its head, it may be cable related or some secondary effect of something close by damaged or changed.

I think you need to measure the voltage as was previously mentioned... But a capacitor will not hurt anything.
 
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