Our alternators come in a variety of performance options, as indicated in the drop-down menus in each listing.

100% New H.D.(Heavy Duty) MAXX units are direct heavy duty replacements for your original alternator.

High Performance Super MAXX, Ultra MAXX and Mega MAXX alternators are excellent for extra accessories, high watt sound systems and off road light packages.
Also they can be used as a Super Heavy Duty replacement for your original factory alternator.

High Performance 160, 170, 200 and 250 amp units must have the positive battery wire upgraded, please refer to our technical information page for wire sizes

160 amp units will put out 70-80 amps at idle
170 amp units will put out 75-85 amps at idle
200 amp units will put out 90-100 amps at idle
250 amp units will put out 120-130 amps at idle

If you do not see your vehicle listed and want to place an order please contact customer service.

Pictures are for reference purposes only
Units will vary according to year, make, model and engine size


Installing our high amp alternator will be a direct bolt-in installation unless otherwise notified before purchase. Proper performance, though requires more than standard installation expertise.

Keep in mind that you are not installing a stock alternator and it will not function the same on your car as your stock alternator does. The most common problem you may experience on initial installation is low out put at idle. This problem is easily solved with system upgrades that we describe below.

If you are not prepared to make needed system upgrades or feel you will not need to make those upgrades for whatever reason, please do not attempt this project.

High amp alternators are very RPM, WIRE GAUGE and BATTERY sensitive. These three things are absolutely necessary for optimum performance -

#1 - The positive battery cable to alternator MUST be upgraded to heavier gauge wire according to the amperage of the new alternator. Please refer to chart on the technical information page for correct wire gauge size needed. WARNING - IF THE POSITIVE BATTERY WIRE IS NOT UPGRADED, YOUR NEW HIGH AMP ALTERNATOR WILL NOT FUNCTION CORRECTLY!!!

#2 - A smaller than stock pulley is used on the 200 amp and 250 amp alternators to achieve maximum output at engine idle speeds. A worn or stretched alternator belt that is working fine on your stock alternator will slip on a high amp alternator and cause a no charge or low output condition due to excessive torque created by the new high amp alternator. In some cases even a new stock size belt will slip. For that reason, in some cases a shorter than stock belt is needed. This is not always necessary on the 160 amp and 170 amp upgrades.


#3 - A fully charged heavy duty battery is a must. Alternators do not charge dead batteries and batteries must be fully charged with a battery charger before installation. If your battery is located in your trunk then you will have to consider that distance when selecting wire gauge size.
If you are attempting to install a high amp alternator with a battery isolator, you must make sure that the isolator is installed and wired correctly.

If you would like to discuss your installation project before you purchase, please feel free to contact us at 586-585-1931 or use the Parts Request Form at the bottom of this page in the footer.

Mimimum cable size to use (AWG)

Amps < 5 Ft 5-10 Ft 10-15 Ft 15-20 Ft 20-25 Ft 25-30 Ft
12 Volt 0-60 8 AWG 4 AWG 2 AWG 2 AWG 1 AWG 0 AWG
12 Volt 60-100 6 AWG 4 AWG 1 AWG 0 AWG 0 AWG 2/0 AWG
12 Volt 100-150 4 AWG 2 AWG 0 AWG 2/0 AWG 2/0 AWG 3/0 AWG
12 Volt 150-190 4 AWG 1 AWG 2/0 AWG 3/0 AWG 4/0 AWG 4/0 AWG
12 Volt 190-250 2 AWG 0 AWG 2/0 AWG 4/0 AWG 4/0 AWG 4/0 AWG
12 Volt 250-300 0 AWG 2/0 AWG 3/0 AWG 4/0 AWG 4/0 AWG 4/0 AWG
24 Volt 0-30 14 AWG 14 AWG 10 AWG 8 AWG 8 AWG 6 AWG
24 Volt 30-50 12 AWG 10 AWG 8 AWG 6 AWG 6 AWG 4 AWG
24 Volt 50-75 10 AWG 8 AWG 6 AWG 4 AWG 4 AWG 2 AWG
24 Volt 75-100 6 AWG 6 AWG 4 AWG 4 AWG 2 AWG 1 AWG
24 Volt 100-125 4 AWG 4 AWG 4 AWG 2 AWG 2 AWG 1 AWG
24 Volt 125-150 2 AWG 2 AWG 1 AWG 1 AWG 0 AWG 0 AWG

Electrical Formulas For Determining Amperage Needs

Watts Divided by Volts = Amperes (amps)   

Watts Divided by Amperes (amps) = Volts

Volts Divided by Amperes (amps) = Ohms

Volts Multiplied by Amperes (amps) = Watts

Pulley Ratio

For most people, the only alternator rating they are familiar with is the amperage rating.

Alternators are spoken of as a 65 amp or 100 amp alternator. When replacing the alternator on the family car, this is probably the only information that is necessary. After all, all one needs is an alternator that matches the original.

When building a custom car from the ground up however, a deeper understanding of the power curve of an alternator is required. Usually a custom pulley or so-called "power pulley" set is used with a performance alternator. A mismatched pulley ratio and alternator will spell trouble, especially at idle speeds where alternator performance is critical. To avoid this, it is important to understand the alternator's capability at slow speeds.

An alternator's output is dependent on speed, but this can be deceiving because this output is not linear. Instead, it follows a curve. Each alternator has a unique curve, and at idle small changes in the alternator's speed can make a big difference in its output capacity.

Because of the preceding, pulley ratios are very important, especially when using high amperage alternators. The pulley that are supplied with the alternator are matched to the winding and power curve. It is important that any dress up pulley sets do not deviate from this ratio. Typically, a street driven car should have a pulley ratio of at least 3:1. If the vehicle has an automatic transmission with a low idle and the vehicle spends a lot of time cruising, then a higher pulley ratio - perhaps 3.5:1 - should be used. Alternators can take high speeds up to 20,000 RPMs for short periods, so overdriving the unit is not a problem.

The output of high amp alternators can drop off substantially under 2400 rotor RPMs. Therefore, Motor City Reman does not recommend power pulleys with high amp alternators.

Motor City Reman uses a state-of-the-art computer alternator dyno to measure the performance of each alternator we manufacture. Output curves, engine idle speeds, and alternator pulley ratios are carefully considered to assure good drivability at idle and slow cruising speeds.

How to Determine Ratio and Rotor Speed

The alternator rotor RPM is not necessarily the same as engine RPM. To calculate the actual alternator RPM, determine the ratio between the two pulley diameters.

Ratio = Crankshaft Pulley Diameter/ Alternator Pulley Diameter

Now that we know the ratio, we can now determine the rotor speed:

Rotor RPM = Pulley Ratio x Engine Speed (example; 2.1 x 870 = 1827 Rotor RPM)

Tech Tip: Generally, the alternator should be 1:1 with the motor for circle track racing. For drag racing, the alternator should be overdriven by a ratio of 1.75:1 or more. This will allow charging on the return slip and in staging. For street use, we recommend 3:1.
Scroll to top