Exhaust System Fabrication

Hints & Tips that will save you time & hassle

Where To Start ??

The main factors to consider when fabricating an exhaust system are:

1. Good ground clearance

2. Well mounted & supported (down-pipe bracing)

3. Designed correctly with a exhaust flexi or exhaust bellow for movement.(for more information on exhaust flexi & bellow and how they can help with exhaust longevity click here)

In this article we will explain how we manufacture our systems and a few handy tips to help if you are starting out or giving it a go yourself from home.

Stainless steel is a different beast than mild steel it moves a lot when welding so this write up would be more suited for stainless steel.

You can get away with tacking up and welding off a lot more with mild steel as it will not move the same as stainless.

With stainless steel If you are going for full penetration welds and back purging then the stainless will move more than you think, there are a few ways which you can help with the movement and we will explain these in the follow sections of this article.

The main trick to combat the movement is to make the system up in stages, you can use the slip type ends of an Exhaust Flexi, resonators and mufflers to your advantage.

We like to fabricate the exhaust system in stages. Generally = Down-pipe, middle section and rear section. Each section we fully weld off and fit to the vehicle before moving onto the following section, this helps the battle of movement when welding the sections off. For example = if you tacked up the down-pipe, middle and rear sections all at once, took them all back to your bench welded them off and fit them, I can almost guaranty you will have misalignment and clearance issues.

or

You can fabricate, weld and fit the down-pipe then move onto the middle section do the same fabricate, weld and fit, then the rear section do the same. This way you greatly reduce the chance of alignment and clearance issues, by taking your time and paying attention.

Down-Pipe

This picture shows the downpipe after a few hundred kilometres, this is why it has the burnt colour to the stainless steel

Here the downpipe is bolted up with the down-pipe bracing added

Middle Section

Generally you would make up the middle (longest) part of the exhaust in x3 sections, and have a exhaust vband or exhaust flange after the down-pipe and one at the rear of the system after the sub-frame. We do this so the system can be pulled off and on with ease and at the rear we like to have the ability to add removable sections so straight pipes can be used if needed in the future. It also gives you the ability to make up the middle main section of the exhaust fully and have it fitted up and mounted on the hangers before the rear section is made up.

In this photo is the first section of exhaust that will be tacked up in place, the tube will not be attached to the flange or the flexi at this stage

Here is the section that can be pulled out and welded up on the bench

We have added the flexi a bit further down the system so it sits up above the chassis rails for good ground clearance, the flexi also sits higher than the exhaust itself so if anything scraps it will be the stainless tube not the braided flexi which will soon wear out if it happens regularly

After welding up the first section and letting it do all the moving from welding you can now sit the exhaust system back up on your stands and re-align the section into your exhaust flange, also you can add the flexi back on the end and start to cut up and fabricate the next section of the exhaust.

With the first section welded up we also have added a wastegate starter for our re-movable wastegate setup

We now tack up the next section in place leaving the flexi on the first part of the exhaust, then pull the next section off weld it up and re-fit it.

With the x2 first sections fully welded and put back in place it now pays to align everything checking for clearances and add a few tacks to the flexi, if you are happy where the flexi is sitting then it pays to add at least x10 tack welds or a few good stitch welds to stop anything from moving

The last section has been tacked up, removed and fully welded then fit back in place and some tack welds placed on the start/entry of the resonator, we also add a mount to the section at this stage and let some of the weight be taken so the exhaust will sit correctly. It is important to have enough tack welds on the resonator before adding any rubber mounts, if only a few tacks are on it then the tube can move.

Middle section of exhaust fully welded and ready for final fitment

Pro Tip = Before adding your exhaust hangers raise the exhaust system up slightly to allow for the rubber mounts to have a bit of preload on them (the amount varies depending on the type of rubber mount but start with 5mm)

Rear Section

The rear section is much the same process, once the middle part of system is fitted and hanging on the rubber mounts, you can setup your rear canon in place and tack up the tube between the rear vband or flange set, remove it, fully weld it and then slip back in place for the final tacking up in place.

Once again you want at least x10 tack welds or x3 good stitch welds on the tube before re-moving it for final welding. With the tacks in place we add the last of the rubber hangers (lifting the rear section around 5mm for these mounts we are using as once the weight comes on the mounts when the stands are re-moved then the exhaust will sit very close to where you need it to)