T7Design Alternator Underdrive Pulley Honda K-Series K24 20% Underdrive

£66.00

SKU T7D-C91-83D-4D7 Category: Brand:
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why buy from us

The T7Design Alternator Underdrive Pulley increases performance by reducing the force needed to overcome the inertia of the alternator during acceleration and gear changes, this will result in a snappier throttle response and more horsepower reaching the wheels.

Alternators, in general, have a broad generating power band with the Honda K20 alternator producing a reasonable output from just 1,500 rpm, with max output being produced from 4,000 to 18,000 RPM, with this latter figure technically being the maximum warrantied rev limit. In some applications, where the engine is spending most of its time in the upper half of its rev range, you simply do not need to drive the alternator at such a high speed. However, the only issue you would potentially face is a lower output at idle, in which case you may need to increase the idle speed to ensure the alternator is producing more current than is being consumed by the vehicles electrical systems. An underdrive pulley should also be considered if you have raised your rev-limit of your engine, for example if it is now 10% higher we would recommend fitting a 10% underdrive alternator pulley and so on.

  • Underdrives the alternator pulley to free up additional Horsepower.
  • Hard anodised black for superior finish, corrosion resistance and wear resistance.
  • Precision machined to very tight tolerances.
  • Almost half the weight of the OEM steel pulley.
Specification Metric Imperial
Weight – 10% Underdrive 0.145 kg 0.319 lbs
Weight – 20% Underdrive 0.175 kg 0.385 lbs
Weight – Stock Steel Pulley 0.275 kg 0.605 lbs
Construction Billet 6061-T6 Aluminium
Finish Hard Anodised Black
Manufacturer T7Design
Part Number C91-83D-4D7

ATTENTION

  • It is recommended to use an impact gun to remove the original alternator pulley.
  • Fits both models of Honda K20/K24 alternator.
  • For road applications we would not recommend going less than the 10% underdrive pulley, any less and you may find the OEM alternator cannot provide enough charge at idle with all electrical accessories turned on.

Returns Policy

We want you to shop with confidence at Sansoms Specialist Parts. If you are not completely satisfied with your purchase, you may return eligible items in accordance with the policy below.

  • Returns must be requested within 14 days of delivery

  • Items must be unused, uninstalled, and in original packaging

  • Products must be returned in a resaleable condition

  • Proof of purchase is required

Custom-made, special-order, or clearance items may be non-returnable unless faulty.


 

How to Request a Return

Please contact our support team before returning any item. Returns sent without prior authorisation may be refused.

Email: support@sansomsspecialistparts.co.uk
Include your order number and reason for return.


 

Refunds

Once your return has been received and inspected, we will notify you of the outcome. Approved refunds will be processed to the original payment method within 5–10 working days.

Original shipping costs are non-refundable unless the item is faulty or incorrect.


 

Warranty Information

All products sold by Sansoms Specialist Parts are covered by a manufacturer’s warranty, where applicable.

Warranty coverage typically includes:

  • Manufacturing defects

  • Faults occurring under normal use

Warranty does not cover:

  • Incorrect installation

  • Wear and tear

  • Damage caused by misuse or modification

  • Track or competition use unless stated otherwise


 

Warranty Claims

To make a warranty claim, please contact us with:

  • Order number

  • Description of the issue

  • Supporting photos or videos

Claims are subject to inspection and manufacturer approval.


 

Important Notes

  • Professional installation is strongly recommended

  • Warranty may be void if parts are incorrectly fitted

  • Vehicle compatibility is the customer’s responsibility


 

Need Help?

If you have any questions regarding returns or warranty, our team is happy to assist.

Delivery Options

We aim to get your performance parts to you as quickly and safely as possible.

  • Standard UK Delivery: 3–5 working days

  • Express UK Delivery: 1–2 working days (subject to availability)

  • International Delivery: 5–10 working days (depending on location)

All orders are carefully packaged to ensure your parts arrive in perfect condition.


 

Shipping Costs

  • Standard delivery is charged at checkout based on weight and destination

  • Free UK delivery on orders over £100

We offer tracked shipping so you can monitor your order every step of the way.


 

Stock Availability

  • Most parts are held in stock for immediate dispatch

  • Some specialist or custom parts may have longer lead times

  • Stock levels are updated regularly, but occasionally items may be temporarily unavailable

If a product is out of stock, we will notify you immediately and offer alternatives or an estimated delivery date.


 

Order Processing

  • Orders are typically processed within 1–2 working days

  • You will receive a confirmation email once your order has been dispatched

  • Large or heavy items may require additional handling time


 

Important Notes

  • Performance parts may require professional installation

  • Delivery times are estimates and may vary during peak periods

  • International shipments may be subject to customs or import fees

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