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Ignitions and Electrical› Computers, Chips, Modules and Programmers

RENNtech

HHT ECU Upgrade

$2,980.00 $1,950.00 Save $1,030.00

SKU: 50.215.CL600.KIT

In Stock
In Stock
Ships by Aug 31
Free Shipping over $200
$100 Minimum Order
30 Days Return
INSTALL DIFFICULTY
DIY PRO SHOP

Advanced — 4+ hours

Overview

The RENNtech HHT ECU Upgrade is a performance tuning module for the CL 600 C215. It increases output to 417 HP and 446 lb-ft of torque. This upgrade offers significant gains across the entire RPM range while maintaining daily driver reliability.
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The RENNtech HHT ECU Upgrade is designed for the CL 600 C215 model, specifically for the M137 5.8L V12 engine. This proprietary ECU tune provides substantial performance enhancements across the entire RPM range, aiming to improve power without compromising daily drivability or reliability. According to RENNtech's dyno results, this ECU upgrade pushes the M137 engine's performance from its stock 362 HP and 390 lb-ft of torque to an impressive 417 HP and 446 lb-ft of torque at the crank. The vehicle's stock performance is noted as typically exceeding factory ratings, with the modified performance numbers reflecting the significant gains achieved through this tuning module.

Product descriptions are provided by our supplier partners and may not always be perfectly accurate. Not sure this fits? or call (760) 282-4645 and we’ll verify before you order.

Fitment

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Specifications

BrandRENNtech
Part Number50.215.CL600.KIT
CategoryIgnitions and Electrical

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Returns & Fitment

Built for enthusiasts. Every order is backed by our 30 day return window on eligible items. Unused and uninstalled products may be returned with approved RMA and no restocking fees when received in new condition. Orders placed through the MOTORMIA app with a complete build qualify for our Fitment Guarantee — free return shipping if the part doesn’t fit your exact setup. The guarantee covers fit only; installation must follow manufacturer instructions, and we recommend a qualified shop for parts marked Difficulty 4–5.

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Shipping

Orders are processed in 1–3 business days. In stock parts ship promptly from our partner network. Special-order items either aren’t currently stocked or are built to your spec — expect 4–6 weeks. If a part goes on backorder while your order is in the queue, we’ll reach out and work through discounted alternatives together.

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