New Mechman 250 Alternator Question

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iamdub

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Not sure if the design of the 2010 is similar to my 2006. The alternator is somehow connected to the "computer" as part of controlling the output. The voltage is high for awhile and then drops as the computer "thinks" the battery is charged after doing some starting work.

Yup- RVC (Regulated Voltage Control). Prevents unnecessary (over?)charging of the battery and load on the alternator. The reduced drag from the alternator when it's not needed increases fuel economy. It's nothing you'd ever realize, but it's still a factor. The reduced load and wear are the primary benefits.
 

iamdub

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If you're upgrading to a mechman 250 because you are going to have a larger draw, (from probably a stereo), then cool, but you only have a few posts, and it's common for people to be concerned about the dropping voltage. 05+ the alternator's voltage is no longer internally regulated, and instead the voltage is controlled by the ECU in order to reduce drag and increase mpg. Voltage dropping down to as low as 11 volts while running is doing what it's designed to.

if you plan on having an additional draw of 90 amps, that should cover somewhere around 1300w-1500w. You might also want to look into changing that voltage so that it's a steady 14.* volts.

90 amps x voltage, lets say 14.4 = 1296w.
1296w x amp efficiency (call it 80%)= 1036w about a 1000w from amp.
That's when your sub is hitting on full at full volume. You have some room in your stock, and that 1000w is not a full draw all the time, (it's charging between those hits). Depending on the music, you can usually go 30-50% over that and still keep fully charged at full volume.


That is very un-hot-rodderish of you. We should always go for MOOOAAAARRR POWUUURRRR!

Fo real, doe, it's good to apply the math and logic. I wanted to replace mine and was looking at upgrading like a megalomaniac. Being realistic, that 30 amps I sacrificed by going with the high output OEM alternator was easy to accept considering the 220A was still more than enough and a couple hundred bucks cheaper than the Mechman.
 

Burban22

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I have an 03 burb z71 with every factory option, bose, front rear trizone hvac. I've added a 500w amp with 2 12" subs and LED headlights but other than that its stock. Voltage gauge reads 14 all the time seems fine but when running a 140W power inverter on the rear power plug, if it draws more than 75W the low voltage alarm on the inverter goes off.
Not sure what alternator I have but its the LM7 5.3 and battery is always charged, not sure if I have the 105 or 145amp. I've seen some threads. of people upgrading to this 253 amp china special.

Personally I may repalce mine with a Denso 145 amp but only if it needs it.
Denso Products 210-5384 Denso Remanufactured Alternators | Summit Racing

Are alternators the same GMT800 and GMT900 2001 - 2013? Mine had the 4 pin rectangle plug on the rear.
 
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Fless

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Sometimes the alternator amperage is stamped into the alternator housing, so you may be able to see it on yours. If you post up your Kxx RPO codes we may be able to tell you what came with it as OE.

The 145A alternator will have the center spacer in the case (see arrow below) but the 105A will not.

145a.JPG

105A:

105a.JPG
 

Burban22

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@Fless
1701312232269.jpeg

I’ll also look at alternator to see if it has the gap or not. Could have been replaced in the past 20 years.
 

Doubeleive

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I have an 03 burb z71 with every factory option, bose, front rear trizone hvac. I've added a 500w amp with 2 12" subs and LED headlights but other than that its stock. Voltage gauge reads 14 all the time seems fine but when running a 140W power inverter on the rear power plug, if it draws more than 75W the low voltage alarm on the inverter goes off.
Not sure what alternator I have but its the LM7 5.3 and battery is always charged, not sure if I have the 105 or 145amp. I've seen some threads. of people upgrading to this 253 amp china special.

Personally I may repalce mine with a Denso 145 amp but only if it needs it.
Denso Products 210-5384 Denso Remanufactured Alternators | Summit Racing

Are alternators the same GMT800 and GMT900 2001 - 2013? Mine had the 4 pin rectangle plug on the rear.
probably because you are drawing too much power thru those tiny wires at the rear power port.
 

Burban22

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probably because you are drawing too much power thru those tiny wires at the rear power port.
I would have thought a fuse would blow instead of it not suppling enough power to the 140w inverter with a draw of 90w. I guess I could wire in another power port on the other side and tap into the heavy gauge amp power and ground wires.
 

Burban22

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Good to know I have the 145a alternator. Can anyone recommend a decent amp clap meter or another way to measure what my alternator is putting out?
 

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