Stage 2 Exterminator Kit // 2025-2027 Arctic Cat CATALYST M 858 C-TEC2 Models

FREE ECU Tune (Reg. $449.95) - Use Coupon Code "M858" - Speedwerx Power Check

Speedwerx Stage 2 Exterminator Kit // 2025-2027 Arctic Cat CATALYST M 858 C-TEC2 Models

Our Exterminator Kits are designed and tested as a package to ensure our customers are running the correct combination of parts for their particular model, giving you the confidence that you are getting the best bang for your buck. These kits are designed for everyday type riding and require premium pump gas. 

Dyno testing on the 858 has shown a 18hp gain with our Pipe, Y-Pipe, Stealth Head, and Air Intake, with another 3hp gain estimated with increased compression ratios at high elevation! We will be offering our Exterminator Kits for a complete package that include these parts plus an ECU Tune and Hypershift Clutch Kit for maximum power and performance in a bolt-on kit. Update 2/28: an ECU Tune is required with the Pipe/Head/Intake combo! Note: If you wish to use pump gas at varying elevations, order the Stealth Head for the lowest elevation you regularily ride at. Higher compression heads can be used at lower elevations with high octane race fuel or a race/pump blend, however we do not have specific fuel recommendations for these cases.

Stage 2 Exterminator Kit Includes:

• Speedwerx Fat Daddy Pipe & Y-Pipe
• Speedwerx Stealth Head Mod
• Speedwerx ECU Reflash
• Speedwerx Hypershift Clutch Kit
• Speedwerx High Flow Intake

Optional:

• Speedwerx Standard Lightweight or L2 Series Muffler
• EZ LYNK Device + Cables

 

We highly recommend our Exterminator Kits to get a complete bolt-on performance package developed on our dyno and thoroughly field tested to meet our strict performance standards. The Stage 2 Exterminator Kits are the ultimate choice for those wanting maximum power and performance in a naturally aspirated, stock displacement bolt-on package with pull and go reliability on pump gas. The Stage 2 consists of our Fat Daddy Pipe & Y-Pipe, Stealth Head Kit, ECU Flash, Hypershift Clutch Kit, and High Flow Intake.

The Fat Daddy Pipe & Y-Pipe is the key to making big power, but that's just one part of the performance equation. Our ECU Flashes that are developed in-house change the fuel and timing parameters to ensure you’re getting maximum power and excellent throttle response with pull and go reliability on pump gas. Our Hypershift Clutch Kits keep the revs in the sweet spot to get all that added power to the ground when pipe temps and RPM’s climb on a long pull across the lake or up the mountain. The Stealth Head Mod has our interchangable billet domes with a special chamber and cooling design to reduce the chances of triggering the knock sensor to keep you at peak power all the time, and it also enables those riding at higher elevations to safely bump up the compression on premium pump fuel as well. The High Flow Intake opens up the restrictive stock intake plenum to round out the package. You can use all of this in conjunction with your stock muffler for quiet power, or add our standard Lightweight Muffler that's lighter than stock for a liitle better sound at a level reasonably low for everyday trail riding, or the L2 Series Light n' Loud Muffler for the lightest weight with an aggressive race sound. 

 

You must send your ECU for programming, and Cylinder Head for exchange! Please include a copy of your invoice or a note with your return address and order number. We will hold your order to ship after we complete the Pipe Modification. 

Ship to:

Speedwerx, Inc.
20195 Greystone Avenue
Forest Lake, MN 55025

 

TECH NOTE: Power Valve cables- we have seen a large number of sleds that the power valves are not set properly from the factory or they have moved, this dramatically effects the overall performance of you machine. Using AC tool # 836-00005 you need to confirm these are set right and if you have issues check them again. In our opinion, this is needed on every single 858 out there even in bone stock form. There is also a Technical Advisory regarding the Servomotor Bracket Alignment issued 12/5/25- your dealer may have already contacted you about this done this as part of the pre-delivery inspection, but they can help you with these adjustments if you are not comfortable doing them yourself. You can purchase the Adjustment Tool Kit here- https://speedwerx.com/apv-adjustment-tool-kit-858-c-tec2-models.html 

 

Arctic Cat 858 Dyno Test Article from SnowTech Magazine 

 

SPEEDWERX 858 ARCTIC CAT CATLYST POWER UP 

It is an understatement to say the entire industry was beyond excited to see the new 858 engine platform from Arctic Cat.  We got on the dyno as soon as we could last fall and here is what we know as of today. 

We have over 350 dyno runs on our Superflow 901 engine dyno, and  over 150 more runs on our track dyno / simulator.  Everything we are talking about on this article is 100% 91 premium pump gas / non -ethanol from Kwik-Trip. 

We focused on intake, cylinder heads, y-pipe, single pipe, mufflers, and ecu programing. 

Our target water temp was 80-90 degrees and we didn’t start any runs until the pipe was around 850 degrees F.  We use the AIM and EZ Lynk data loggers to monitor all of the stock Ecu channels and knock sensors to verify everything is safe and in a good working order. 

Bone stock with the stock hood and intake 100% in place we are seeing 148.4 hp at 8200 rpm on our engine dyno and 148.8 hp at 8150  our track dyno / simulator. 

Run# 262 Stock baseline. 

EngSpd	STPPwr	STPTrq	AFLam2	AirTmp	WtrOut	STPCor
RPM	CHp	Clb-ft	Ratio	degF	degF	Factor
5900	86.2	76.7	15.37	63	84	1.037
6000	89.8	78.6	15.35	65	83	1.039
6100	91.3	78.6	15.08	65	83	1.039
6200	93.1	78.9	14.83	64	83	1.038
6300	94.6	78.9	14.67	64	83	1.038
6400	95.1	78.1	14.58	64	83	1.038
6500	97	78.4	14.53	64	83	1.038
6600	96.6	76.9	14.55	65	83	1.039
6700	96.8	75.9	14.58	65	83	1.039
6800	99.3	76.7	14.59	65	83	1.039
6900	97.1	73.9	14.56	65	83	1.039
7000	98.1	73.6	14.29	65	83	1.039
7100	97.1	71.8	14.05	65	84	1.039
7200	97.8	71.3	14.04	65	84	1.039
7300	98.9	71.1	13.94	65	84	1.039
7400	102.3	72.6	13.88	64	84	1.038
7500	136.2	95.4	13.07	64	83	1.038
7600	138.5	95.7	13.03	64	83	1.038
7700	140.5	95.8	12.99	65	83	1.039
7800	144.1	97.1	12.84	65	83	1.039
7900	146.8	97.6	12.78	65	84	1.039
8000	148.2	97.3	12.78	65	84	1.039
8100	148.1	96	12.72	65	84	1.039
8200	148.4	95	12.69	65	84	1.039
8300	145.1	91.8	12.65	65	84	1.039
8400	141.9	88.7	12.55	65	84	1.039

 

Intake: 

We had a good suspicion there would be a lot to be gained in the intake.  The first thing we did was remove the hood, then the seal between the hood and air box, and then the air box.  This kind of told us what was there to be gained.   We also put a few of the other older 800 intake plenums on it to see what it liked or didn’t like.   With all of these parts removed we saw there was about a 5 hp gain over stock available.   We went to work and we were able to get the stock hood and air box to make the same power as we did with everything removed.  Our high flow intake kit consists of 3 frogzskin vents that go on the front / lower half of the airbox and a billet adapter with seal that goes between the hood and the stock airbox.  This set up does require you to remove material from the inlet flange of the air box and to drill 3 holes for the frogzskin. 

Speedwerx, Inc. | High Flow Intake Kit // 2025-2026 Arctic Cat ZR / RIOT / M 858 C-TEC2

 

Run # 265 Speedwerx High Flow Intake

EngSpd	STPPwr	STPTrq	AFLam2	AirTmp	WtrOut	STPCor
RPM	CHp	Clb-ft	Ratio	degF	degF	Factor
6000	92.4	80.9	15.95	61	85	1.035
6100	94.8	81.6	15.31	61	85	1.035
6200	97	82.1	15.04	61	86	1.035
6300	98.2	81.8	14.79	61	85	1.035
6400	100.3	82.3	14.59	61	85	1.035
6500	100.4	81.1	14.54	61	85	1.035
6600	99.9	79.5	14.62	60	85	1.034
6700	101.2	79.4	14.64	61	85	1.035
6800	101.2	78.1	14.58	61	86	1.035
6900	100.9	76.8	14.32	61	86	1.035
7000	101.2	75.9	14.1	62	86	1.036
7100	97.8	72.3	13.86	61	86	1.035
7200	98.8	72	13.83	61	86	1.035
7300	100.1	72.1	13.81	61	86	1.035
7400	103.1	73.2	13.8	62	86	1.036
7500	135.1	94.6	13.02	62	85	1.036
7600	138.3	95.6	12.97	63	85	1.037
7700	144.3	98.4	12.84	63	85	1.037
7800	147.2	99.1	12.72	63	86	1.037
7900	150.7	100.2	12.69	63	87	1.037
8000	152.1	99.9	12.67	63	87	1.037
8100	152.6	98.9	12.63	63	87	1.037
8200	153.2	98.1	12.65	63	87	1.037
8300	154.6	97.8	12.66	62	87	1.036
8400	152	95	12.61	62	87	1.036

 

Heads:

 We ran stock, stock with tighter squish, stock with different squish to pocket blend radius, different squish band widths, different squish thicknesses.   All in all we ran over 18 different head spec configurations to come up with what we have now.  The stock head is around 12.75:1 compression ratio.   We are now offering heads in the 12.75 / 13.25 / 13.75 / 14.25 and 14.75 ratios for different elevations and applications.  Our heads are a lot different from the stock head design.   We have found that the 12.75 and 13.25 domes will work for everyday pump gas trail riding applications, if racing 500’ drags you can go even higher but as you do things get riskier too.  The 12.75 heads add 5 hp at sea level on premium pump gas.  Riders riding at higher elevations like 6000’ + can run our 14.25 heads and see an 8 hp gain over stock. 

Speedwerx, Inc. | Stealth Head Mod // 2025-2026 Arctic Cat ZR / RIOT / M 858 C-TEC2 Catalyst

 

Exhaust / Mufflers:   

We have 3  muffler options.  Our L2 light and loud race series in stainless steel – 14.1 lbs and Titanium -16.35 lbs and our Standard trail muffler -9.15 lbs. Both are guaranteed not to loose or hurt performance over stock.  We verify this with flow testing, verifying exhaust pressure in the field and dyno testing. 

Speedwerx, Inc. | L2 Competition Series Lightweight Muffler // Stainless Steel // // 2025-2026 Arctic Cat ZR/RIOT/M 858 C-TEC2 CATALYST Models

Speedwerx, Inc. | Lightweight Muffler // Ceramic Coated // 2025-2026 Arctic Cat ZR/RIOT/M 858 C-TEC2 CATALYST Models

Speedwerx, Inc. | L2 Competition Series Lightweight Muffler // Titanium // // 2025-2026 Arctic Cat ZR/RIOT/M 858 C-TEC2 CATALYST Models

 

Speedwerx Pipe and Y-pipe: 

We tested 9 different pipe and y-pipe configurations.  Pipes that ran at lower rpm, higher rpm, different stinger sizes both length and diameter.  Y-pipes with bigger throats, smaller throats and everything in between.   The set up we liked the best added power everywhere as you can see on the dyno chart.   Its an easy 8 hp gain or more from 6000 rpm up.  Early on in our testing we thought we would be able to run this package on the stock ECU program but once we got it in the field we learned that was not an option.  This dyno data is with early rough in fuel programming we had to finalize the programing in the field and we have not been back on the dyno since to verify what the #’s are but if anything we expect them to be even better.  We have 2 versions of Single pipe 0-5000’ and 5000’ +, we have been doing this now for about 15 years with great results.  The 5000’ pipe is tighter for the thinner air at higher elevation. 

Speedwerx, Inc. | Fat Daddy Single Pipe and Y-Pipe // 2025-2026 Arctic Cat ZR / RIOT / M 858 C-TEC2 // 0-5000' Elevation

Speedwerx, Inc. | Fat Daddy Single Pipe and Y-Pipe // 2025-2026 Arctic Cat ZR / RIOT / M 858 C-TEC2 // 5000' + Elevation Only!

 

Speedwerx Stage 2 package:  + 18hp at low elevation / +21 at higher elevations. 

Intake

Head

Y-pipe Pipe

ECU flash

Speedwerx, Inc. | Stage 2 Exterminator Kit // 2025-2026 Arctic Cat CATALYST ZR 858 C-TEC2 Models

Speedwerx, Inc. | Stage 2 Exterminator Kit // 2025-2026 Arctic Cat CATALYST M 858 C-TEC2 Models

 

Run # 332 Speedwerx Pipe and Y-Pipe, Speedwerx 12.75 Head, Speedwerx High Flow Intake

EngSpd	STPPwr	STPTrq	AFLam2	AirTmp	WtrOut	STPCor
RPM	CHp	Clb-ft	Ratio	degF	degF	Factor
6100	94.8	81.7	14.32	51	80	1.029
6200	96.9	82.1	14.14	50	80	1.029
6300	98	81.7	14.04	50	80	1.029
6400	99.5	81.7	13.94	50	80	1.029
6500	102.2	82.6	13.92	51	80	1.030
6600	104	82.8	14.04	51	80	1.030
6700	104.2	81.6	14.26	51	80	1.030
6800	104.4	80.6	14.38	51	80	1.030
6900	106.6	81.1	14.42	51	80	1.030
7000	106.8	80.1	14.22	51	80	1.030
7100	106.9	79.1	14.13	51	80	1.030
7200	107	78	14.06	51	80	1.030
7300	135.9	97.8	13.38	51	80	1.029
7400	142.4	101.1	13.17	51	80	1.029
7500	146.1	102.3	13.01	51	80	1.029
7600	147	101.6	12.98	51	80	1.029
7700	154.1	105.1	12.9	51	80	1.029
7800	158.3	106.6	12.75	49	80	1.029
7900	161.2	107.1	12.79	49	80	1.028
8000	164	107.6	12.83	49	80	1.028
8100	167.9	108.9	12.84	49	80	1.027
8200	166.7	106.8	12.84	49	81	1.027
8300	165.9	105	12.84	49	81	1.027

 

Stock vs. Speedwerx Stage 2 Kit

Track Dyno / Simulator Stock 74.4 Hp vs. Speedwerx Stage 2 kit 84.4 Hp. 

                     

 

ECU flashing:

This summer we just released a 500’ drag race ecu flash that adds 10 hp over stock. This flash if designed to run on ISR legal sleds with stock motor, head, and exhaust. 

 

Turbo Kit:  

We released this package for the mountain sleds late last winter with great results and success.   We have a trail package ready to start field testing once the lakes freeze up and the trails are ready.   This package is producing 220+ hp on 91 premium non-oxy fuel from Kwik-trip. 

 

Stage 2 84.4 hp  vs. Turbo kit 113.4 hp. 

 

We would like to remind everyone that it is not good practice to compare dynos from different facilities as they are all different.   We have been using the same dyno here for the past 30 years but just this past summer started a dyno facility renovation that will be up and running later this fall.

 

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Sending us your ECU is always the easiest and preferred way to get it done, but for those that wish to purchase a tool to flash their own ECU, we are using the new industry leading EZ LYNK Auto Agent 3 system. This will not only allow you to flash your ECU but you can also do much more.

• Data Log live and record data to share with tuners or friends.
• Run diagnostics checks on your machine as well as several other powersports and over the road vehicles. (brand-specific cables required for other powersports machines)
• Reset power valves on Polaris 850 and 9r models.
• Flash your own ECU with optional ECU Flash Power-Up Adapter

 

Get Connected with The World's Most Powerful Vehicle Scan Tool. EZ LYNK puts your technician in the front seat whenever and wherever you choose and is the vehicle interface for all EZ LYNK apps.

The EZ LYNK Auto Agent 3 Vehicle Diagnostic Scan Tool and Electronic Logging Device (ELD)

Who is it for?

Vehicle Owners - From 18 Wheelers to Powersports and everything in between. See what we offer for your Vehicle

Vehicle Technicians - Get Connected with your customer and their vehicles; Whenever and Wherever

Transport Companies - Owner Operator, Small and Large Fleet Sizes and even Bus Transport Companies

Commercial Motor Vehicle Drivers - Hotshot, Short Haul, Long Haul, Agricultural and Construction

 

60 Second Setup:

Plug the device into the Vehicle's OBDII Diagnostic Connector

Install the EZ LYNK Mobile App on your Android or iOS Device

Connect via WiFi

Diagnostic Scan Tool and More:

 

A Connected OBD Scan Tool for You and your Vehicle's Technician

Lynk with your Technician

View and Record Vehicle Data Parameters in Real Time

Share Recorded Data Logs with your Technician

Read and Clear Diagnostic Trouble Codes (DTC)

Perform Technician Recommended Vehicle Functions

Install Vehicle Firmware Updates provided by your Technician, Over-the-Air

Chat with your connected Technician, within the Auto Agent Mobile App

 

Auto Agent 3 w/ OBDII Connection

Devices and Software Compatibility:

Android 8.0 or Later

iOS 12.0 or Later

iPad

iPhone

iPod touch

 

Additional Accessories to expand the Auto Agent 3 Connection and Convenience:

Class 8, Medium and Heavy Duty (Semi) vehicles - Auto Agent 3 HD Cables (6 and 9 Pin Round)

ATV, UTV, SnowMobile and WaterCraft applications - Auto Agent 3 Powersports Diagnostic Cables and ECU Flash Power-Up Adapters

EZ LYNK Phone Window or Dash Mount - The phone mount that sticks!

EZ LYNK ELD system requires a monthly subscription