Building F1/WRC Style Exhaust Heat Shields - Process, Materials & Tooling

In the last post I covered what multi-layer thermal shielding is and why it works. This post covers the how - the materials, tooling and process required to actually build these shields. For those do did not see the last post and have never seen this type of thermal management system before, I recommend you give it a read as I go in-depth their on the why and the limitations.

This methodology is not new – it has been standard practice for many of the top teams in F1, WRC, and other high-level motorsport. What is lacking is accessible information on how to implement it. Most of what exists sits in manufacturer technical documents or gets passed between specialists who have worked at that level. The goal here is to make the process available to those building club-level and privateer cars in once concise place as well as provide valuable tools to make it easier to get started.

To demonstrate the process I will be using a recent project as a case study - a dump pipe shield for a Barra swapped 180sx drag and drive build owned by @wintersgarage with the fabrication work on the car completed by @reaper_performance_aus.

🛠️ Materials

The system uses two primary materials - 6mm ceramic fibre paper as the insulating layer and 0.15mm embossed 304 stainless steel sheet as the outer shell.

The ceramic fibre paper is rated up to 1260°C well beyond typical exhaust gas temperatures and provides the bulk of the thermal resistance. The stainless steel sheet protects the ceramic fibre from environmental damage, oil contamination and physical abrasion while providing structural integrity under vibration and thermal cycling.

The stainless sheet thickness can range from 0.05mm to 0.20mm. Thinner material is easier to form around complex curves and provides a marginal weight reduction - useful shapes are complex, clearance is tight or weight is a major concern. However, thinner material is more prone to denting and damage during fitting and in service. For most applications 0.10-0.15mm is the ideal balance between formability and durability.

Exhaust material grade matters significantly. As covered in the previous post, trapping heat accelerates exhaust corrosion. Of the commonly available grades, 316 is ideal, 321 is better again and 304 stainless can be used but will experience accelerated corrosion compared to an untreated setup. Mild steel or cheap stainless grades of unknown origin will not survive the elevated temperatures created by heat trapping - do not use them for this application regardless of cost savings.

I source materials direct from manufacturers in China via Alibaba. Most suppliers will sell "sample" quantities of 10m rolls which is more than enough for multiple projects. The ceramic fibre comes from yaoxingfiber.en.alibaba.com and the embossed stainless sheet from tometal.en.alibaba.com. Buying direct brings the cost down significantly compared to local distributors. For hobbyists this often easily justifies the 10m MOQ when compared with purchasing the lengths they need locally.

If local is the only options then I would suggest looking for the ceramic paper from hobby kiln suppliers as it is used heavily when building DIY kilns.

For the stainless steel embossed sheet I was unable to find a consistent source within Australia. I understand it is much more available in Europe so your mileage may vary.

🔩 Tooling

The tooling required is relatively simple and inexpensive:

• ■Heavy duty scissors for cutting both ceramic fibre and stainless sheet. Something like Black Panther Shears from Sterling works well - they need to handle repeated cuts through thin stainless without dulling quickly.
• ■Jewelers round nose pliers for creating small crimps where the stainless meets flanges. When the stainless sheet is wrapped around the exhaust it is often the case that there is a step down between the sheet and the flange due to the ceramic fibre thickness. The small crimps allow for a neat reduction of the tube diameter to meet the flange cleanly.
• ■An 8oz fibreglass cross pein hammer for tapping down embossing on flange areas to create a flat surface for spot welding, and for flattening the crimps made with the round nose pliers.
• ■A battery cell spot welder. I use an AwithZ UF20B running at 20-40% power depending on material thickness and condition. Too high and you blow through the thin stainless, too low and adequate fusion can't be achieved. Most spot welders marketed for custom battery pack assembly will work - check the manufacturer specifications for their rated material thickness.
• ■Adhesive spray for bonding ceramic fibre to the exhaust surface.
• ■Acetone for cleaning the exhaust surface before applying ceramic fibre.
• ■Any paper or thin cardboard and markers for easy cut template creation.

📐 Process Overview

The process follows a consistent sequence regardless of the exhaust component being shielded:

1. ■Clean the exhaust surface thoroughly with acetone to remove any oils or contaminants.
2. ■Template the stainless shell pieces using paper or cardboard.
3. ■Cut ceramic fibre pieces to shape using the created template and apply using adhesive spray.
4. ■Template the stainless shell pieces using paper or cardboard.
5. ■Transfer templates to stainless sheet and cut out, keeping in mind overlap required for joins.
6. ■Form the stainless around the ceramic-wrapped exhaust, tacking in place as you go using the spot welder.
7. ■Crimp and hammer edges where required for a clean finish against flanges.
8. ■Once everything is in place, go over all seals thoroughly with the spot welder to ensure everything is fully sealed and held in place.

Note: The goal here is to mitigate ingress and remove sharp edges, a full seal will never be achieved nor do we want it. It is important that trapped moisture can escape during operation.

✂️ Templating and Cutting

The hardest part of the entire process is cutting out the correct shapes from flat sheet to wrap three-dimensional compound curves. A bend that looks simple on the pipe becomes surprisingly complex when you need to create it from flat material.

Additionally we must consider we we are going to join adjacent pieces. This is obvious and easy when it is a simple straight section, hover when you have a merge, is it important to take extra time in your planning to ensure all pieces has a suitable overlap between their neighbors.

Paper is an effective templating tool. Cut and wrap paper around the section you need to shield, mark where it overlaps, and trim until you have a shape that wraps cleanly. If you mess it up you can simply get another sheet. Additionally, thick paper or thing cardboard does not like to bend in multiple opposing directions, the same is true for the stainless sheet. Once you are happy with your template, simply transfer to the stainless sheet or ceramic fibre one or multiple times depending on your needs. This trial and error approach with cheap material saves wasting expensive stainless or ceramic fibre on shapes that don't quite work. As much as a "patchwork" on the outside works fine from a technical perspective, we all know aesthetics are important for our builds.

For pipe bends specifically, the geometry can be calculated. I have developed a Blender add-on that generates printable cut templates for any combination of outer diameter, centerline radius, insulation thickness, total bend radius and number of segments. This is hosted on my Github. The repository also contains pre-made templates for common pipe sizes and is available at https://github.com/BBBBower/Blender-Pipe-Unwrapper. For most exhaust system, this removes a majority of the guesswork and templating time.

Forward planning is critical for odd seams and joins. Think several steps ahead about where seams will land and how pieces will overlap. It is very easy to overestimate the bends able to be achieved by the stainless sheet and get stuck with an impossible join. It's not fun having to under several hours of work just to fix a small oversight. When in doubt, use paper to test the approach before committing to stainless.

It is even good practice to cut all pieces out before install to be able to physically confirm fitment before any welds take place.

An alternative to this is to break up the exhaust into sections that start and end in a simple straight sections. This way you know for a fact your prior work will not interfere. with your future work.

🔨 Forming the Shell

The embossed stainless forms relatively easily by hand around most exhaust geometries. Work progressively around the component, pressing the material into contact with the ceramic fibre underneath.

Where the shell meets flanges or pipe ends, the material needs to be reduced in diameter. This is done by creating small crimps around the circumference using the round nose pliers, tacking in several evenly distributed placed, then flattening these crimps with the hammer. The embossing pattern needs to be tapped flat in these areas to provide a smooth surface for spot welding and eliminate any share edges.

The goal is a tight fit against the exhaust component without crushing the ceramic fibre underneath. The small air pockets created by the embossing pattern provide additional convective isolation and help maintain the structural integrity of the shell.

⚡ Welding

The outer shell is spot welded rather than continuously sealed. This approach prevents warping or burning through the thin stainless during welding while allowing moisture to escape, preventing condensation buildup that would compromise the ceramic fibre insulation and accelerate corrosion.

Spot weld spacing of 5-15mm is typically sufficient to hold the shell securely. Welds are placed along seams where pieces overlap and at edges where the shell meets itself around flanges.

The AwithZ UF20B or similar battery spot welder provides enough power for this application when run at 20-40% capacity. Start at the lower end and increase until you get consistent fusion without blowing through. The embossing needs to be flattened at weld locations for proper contact. For joining of adjust pieces often heavy pressure from the spot weld probes and careful weld placement is enough to get proper contact.

To minimize sharp edges it is advised to go over all seams with the corner of the hammer to push down any high spots.

📸 Case Study: Winters Garage Barra 180sx Dump Pipe

This build presented typical challenges - a large dump pipe, multiple size changes, pie cuts, in a tight engine bay with multiple clearance constraints.

In several areas clearance was too tight for the full multi-layer approach. Where the dump pipe routes closest to surrounding components or additional clearance is required for install, ceramic fibre was forgone and a stainless shell only was fitted. This is visible in areas where the shield sits closer to the pipe surface. The shell-only approach provides very limited protection but adds minimal thickness to maintain overall appearance over this immaculate build.

This is the reality of working in tight engine bays. The ideal solution is not always possible and compromises need to be made based on the specific constraints of each application. Understanding where full shielding is critical versus where shell-only is acceptable comes down to identifying which components are most at risk and prioritising protection accordingly.

If additional protection is an absolute must and the space allows multiple layers of ceramic fibre can be used to provide even greater protection. Think sensor, rocker covers and body panels. Thinner sheets of the ceramic fibre can also be sourced down to 1mm allowing for it to still be utilised in some of the tightest applications.

⚖️ Trade-offs and Considerations

The downsides require honest discussion. This is a labor intensive process. A dump pipe shield like the one shown takes many hours of templating, cutting, forming and welding. Each piece needs to be individually fitted and there is no shortcut to getting clean results on complex geometries.

For simple geometries my Blender add-in and premade templates can be utilised to save a substantial amount of templating time but the rest of the work still need to be completed step by step.

Material cost is relatively low when sourcing direct, but the time investment is significant. This is not a weekend bolt-on modification - it requires patience and a methodical approach to achieve a high quality outcome.

Mild steel exhaust components should not be wrapped or shielded using heat-trapping methods. The elevated temperatures created by insulation will cause rapid corrosion and eventual failure. Only use this approach on stainless steel exhaust components, and preferably 316 or 321 grade where budget allows.

As an alternative, internal ceramic coating can be used on these lower end alloys as it rejects the heat internally, preventing the exhaust material itself being heat saturated - though this does bring up the questions of why.

Another alternative is to use the same methods outlined here except instead of wrapping to the exhaust itself, surround the ceramic fibre on all sides with the stainless sheet. Using hose clamps with offset mounts this can be an effective way to protect a nearby component or panel without while allowing proper airflow against the exhaust wall.

📝 Summary

Building multi-layer thermal shields comes down to:

• ■Sourcing the correct materials - 6mm ceramic fibre paper and 0.10-0.15mm embossed 304 or better stainless sheet.
• ■Having the right tooling - heavy duty scissors, round nose pliers, cross pein hammer and a battery spot welder.
• ■Planning the templating sequence before cutting expensive material.
• ■Accepting that some areas may require shell-only where clearance prevents full shielding.

The process is straightforward but time consuming. The results are incredibly effective thermal management that matches what is used in top-level motorsport, at a fraction of the cost of commercial solutions.