Tempest RS - B5 S4 Widebody “Stingray”

Troy Tempest

Registered User
Hi all,

I thought I'd make a post about my build here. I run my own specialist workshop and needed a demo project to use in advertising my business and skills.

As this will be a lot to post in one go (as the car is nearing completion) I’ll make posts over several days. Although saying that, I have started to post this elsewhere - so I have a couple of posts to submit here in one go.

A little about myself: My name is Troy Tempest, those of you of a certain age group may recognise the name from a Gerry Anderson TV show. Given the namesake, the business had to follow suit and it only made sense to nickname the car "Stingray". I studied motorsport engineering at the University of Brighton and worked for a VAG specialist for a little while before moving back to my roots in Nottinghamshire. I then worked for a well known kit car manufacturer before deciding to open my own workshop.

In deciding to build a race car an important consideration is "what do I want to compete in?" - I had my eyes set on the VW Classic Cup, sponsored by the guys at KW Automotive UK. This series, at the time, had a GT class and allowed: 4WD and any VAG group vehicle that was manufactured before 2003. SO, with that in mind I started to look around for what I could buy. I knew it had to be Audi based, 4WD and I ideally wanted a wide body, so that narrowed it down to several models. The B5 RS4 is prohibitively expensive to buy and convert to a racecar and if I were to use a C5 RS6 saloon, I'd have to do the manual conversion. There's also the consideration that the C5 RS6 is a heavier car and the two extra cylinders aren't really needed.

With the criteria in mind, the obvious solution was a B5 S4 sporting the RS4 widebody conversion - the issue was that all the cars I'd seen for sale at the time were complete, highly finished cars in road trim. To cut the story short, no more than five minutes after that thought passed I saw a post in one of the B5 Facebook groups with a widebody converted S4 for sale as a project. It pretty much ticked all the boxes...

Here's a short run down of the spec list:

  • Widebody chassis, freshly painted in Porsche Riviera Blue
  • Freshly built engine with Mahle Motorsport Pistons, Upgraded rods, TDi oil pump conversion, Crank Girdle, 2.8 heads with Rosten Performance valves and titanium retainers, etc.
  • TTE 780 Turbos on MRC manifolds
  • Fidanza lightweight flywheel
  • Gearbox rebuilt with uprated first and second and taller 6th gear - quaife front LDS and 4:1 Torsen torque washers.

That's pretty much the parts that piqued my interest as any interior trim, oil coolers and other parts that came as part of the deal were of no use to myself.

After a few conversations with the owner the deal was done and I went to collect the car.

Here's how it looked when I collected the car:

Now it was in my posession it was time to make a spec build sheet and work out what components I would be adding to the car:

  • Link thunder ECU
  • ECU Master PMU 16
  • ECU Master CanBus Keyboard to control the PDU
  • Cosworth/Pi Omega P4 Pro Dash
  • Pro Alloy 45 litre fuel cell
  • -8 front to back fuel system
  • Tilton 600 series pedal box and master cylinders
  • KW Competition 2 Way dampers
  • Air jack system
  • Custom Cages BTCC STC spec roll cage
  • Aerodynamic package including large single element rear wing.

One the build general specs were decided upon, stage 1 is to strip the car of all in-necessary wiring, brackets and any panels such as the boot floor.


Troy Tempest

Registered User
Part 1:


The most important part of any race car build in my eyes is the ROPS (Roll Over Protection System). There's no point going fast without giving yourself at least the chance to come out alive.

The cage was supplied by Custom Cages here in the UK - The kit is based on the cages that were used in the 1990's BTCC STC A4's driven by the likes of Frank Biela. Comparing the kit to the FIA homolgation docs, its a mix of the '97 and '98 cages.
There are two options for material specification, CDS and T45. CDS is heavier due to needing a greater wall thickness to achieve the same strength as T45, it therefore costs less as its a less superior material. I opted for a T45 cage as I wanted to keep the weight down as much as possible on the build. Even with adding a few extra tubes, the kit comes in at 41.5 KG.

The cage is a 12 point fitment with welded joints to the tops of the front turrets, bottom of the A pillars, bottom of the B pillars, middle of the B pillars, rear seat pans and the tops of the rear turrets.

I wont lie - the process of getting this cage from the manufacturer was difficult and I had to spend lots of time chasing them. When I placed the order I was initially given a two week lead time. After six weks the cage arrived, however a third of it was missing - that took another two weeks to arrive. However, on the flip side, the product is good overall - I did have to adjust some of the tubes to get the best fitment possible, but the material supplied was fantastic to work with and welded very nicely.

Once the kit was laid out it was time to strip all the panels and glass from the car. The problem with turning a freshly painted shell into a race car and welding in a roll cage is trying not to damage the paint!

With all the panels off it is then a case of doing a dry run with the tubes, mark out the footplate positions and start to tack everything in place. This part required more than two hands ideally, so I had my friend Conor give me a hand.

Main ROPS structure in place (A pillars, screen bar, main hoop)

Conor tacking in the A pillar to main hoop lower brace bar

Door bars tacked

Most of the cage now tacked in to position

A personal challenge for me was welding in the cage. There are two options to which welding process you can use to install the cages, MIG or TIG. I had been teaching myself TIG for about 6-8 months at this point and as part of getting the cage certified by the manufacturer you have to send a weld sample in for them to stress test. Given how new I was to TIG I was quite nervous about this part.

weld test sample

I got the test results back after a week and I passed with flying colours - I even got a comment on the test sheet that the visual presentation of the welds were better than the majority of what they see. I was rather proud of myself and passing this stage gave me the confidence to move on to fully welding the joints of the cage.

As I previously mentioned, an issue with the kit was that some of the notches on the tubes weren't the best fit. The inital thought is to adjust them to make them fit better, but in most cases I was unable to do so, as the adjustment would have moved the tube into the wrong position.

Door bar to A pillar/A pillar to Main hoop brace
This is a good example, as I had to build the welds in order to fill them nicely.

Here was the worst offender: LOOK AT THOSE TACKS!

At first Custom Cages told me to just lift the tube up, so that the gap was taken up - as the other tubes around it form a triangle. I wasn't happy with this as lifting the tube up moved it away from its triagulation point and wouldn't conform to the cage design drawing they supplied with the kit. I requested they send a replacement length of T45, which I then profiled myself using my milling machine.

Tempest's Tube!

Finished off with a lovely weld.

Welding the cage into the car took HOURS, TIG is a great welding process, but it is slow and you have to contort yourself in to all sorts of horible positions. I even had to do several joints with the welder amperage control foot pedal between my knees, squeezing them together and relaxing them to pulse the amps up and down on each dab of filler!

Front lateral tube to top of the front strut mountings

I have photos of literally every weldment on the cage, so I'll skip all that and show the finished thing!

One thing, some eagle eyed viewers will notice that there are some extra bits of tube work I haven't covered in the write up in this section. I'm going to be posting this as 'chapters' rather than in a chronological order, as it will make more sense that way.

I'm going to try and post a 'chapter' a week, maybe several a week.

If you've read this far, thank you for getting through it. There's lots more to come!

Troy Tempest

Registered User
Part 2:

Other tube work

As per my last post there was additional tube work that has been put into the car along with the rollcage.

The seat mountings are made from tube also and are constructed from the same material as the cage. When it came to how to build the tubes into the car I took advice from Royce, a good friend of mine who has many years experience building BTCC and other cars here in the UK. He currently works for Motorbase on their Ford RS BTCC program, so I asked how they're mouning the seats into BTCC cars these days. So here's my take on what he told me:

Firstly, I had to remove the original seat mountings, which is a bit of a chore to be honest. There's some 60 odd spot welds between the front mounting that runs across the floor and the runner rails at both sides.

Original seat mounting removal by spot weld drilling

Ignore the big bleb of weld, it fell off the end of the rod on the first pass as I finished the weld. S**t happens! haha.

The tube is placed into the car across the floor and goes through the inner cill section and then through into the tunnel. Supporting plates were then welded around the tubes and to the existing metal panel work. The tubes themselves also have stanchions that come down to the floor, with steel threaded bushes inserted and welded inside, these are the bolted through the floor pan with spreader plates on the underside. The threaded bushes take M10x1.25 bolts (fine pitch is stronger than coarse) and there's four stanchions per seat tube set. So in order for the seat to come out with its framework in the case of an accident, the whole floor pan below the seat, a section of tunel and a section of inner cill would have to come with it all.

I think I posted this above, but you can see the seat tubes quite clearly.

Being able to sit in the car with the seat properly fitted was a big milestone!

Next thing on the list was the frame work for the Tilton 600 series rear facing master cylinder pedal assembly. Again, inspiration taken from the conversation I had with my friend Royce about the seat tubes. I decided to make a framework that would come forwards from the front seat tube, to a cross bar that then would be welded near the bottom of the roll cages A pillar tube. It would also have stanchions to the floor with threaded bushes that secure it through the floor in the same manner as the seat tubes.

The pedal assembly itself is bolted through these box section extensions

Tube framework welded together, but just sat in position

With the framework just sat in position and bolted through the floor with one stanchion, I could pull the whole car across the workshop on the dolly with no movement or deflection. Lovely and strong!

Test fitting the pedal box to the framework. Notice the original steering column being used and tied into an additional tube I welded into the cage.

Seat, pedal box and column all in

As the car is going to be fitted with a Pro alloy fuel cell and as I am going to be running a comprehensive aerodynamic package at the back of the car, the rear floor pan with the spare wheel well had to be removed.

This made the seat runner seem like nothing!

About an hour later!

Booted out

The idea is to weld two tubes across the rear chassis legs that have enough space between them to sit the fuel tank in a new floor section made from aluminium.

Tubes in place

The replacement aluiminium panel was cut to shape and the opening for the tank was made. There will be stanchions that come up from the tubes for the panel to rest on.

Fuel cell placed on jack stands to mock up positioning

The tubes also serve as a great triangulation point to add even more connection points between the chassis and the roll cage, but also the became the support for the air jack installation.

Every true race car needs air jacks in my opinion. If you don't have them and you have an issue during a session at the track, so much time is lost having to jack the car up and put in stands, especially with a small crew.

I purchased a three jack set from Yellow Speed Racing, they're entry level units - the budget has grown so large on the car that I had to compromise somewhere. Ideally I'd have bought AP or Krontec units.
You need the most jacks where most of the weight is, so in my case two at the front and one at the rear. When I looked at the FIA homologation docs for the STC BTCC A4s I noted how the front jacks were fitted and emulated this, with a little less finess but its perfectly functional.

70mm hole in the front corners

I fitted tube into the hole and made plate supports that are welded to the tube and the chassis. I had to MIG these parts as the metal that makes up the original panels has lots of contaminants from cavity wax, undersealer, bitumen sound absorption pads, etc. This makes it extremely difficult to TIG weld.

Oooh my MIG work leaves alot to be desired compared to my tig

Here's the off side unit to the side and rearward of the pedal box

To fit the rear air jack unit I decided to make a framework that would be supported from the forward tube that was previously welded into the rear chassis legs.

So I fabricated this, cut the notches on the milling machine and TIG welded.

The idea behind the ally guide bushes is to tie the framework into the rear subframe, where the rear tie arms are located. This should brace the assembly from being levered forward and backward somewhat.

I have to admit, these were some of my best welds to that point!

Sat roughly in location

Due to the fact that the aluminium pipe that supplies the air jacks with air comes in from the top, I had to put a tube in the middle of the lateral bar between the chassis legs to allow it to pass through.

Supporting tubes in postition, ready for welding.

I can't find any more photos of the completed air jack installation. So I'll get some and update this post.

I hope this is of interest to people out there and it's worth the read!



1x S3 and 3x Fiestas.
Awesome, love seeing this

Troy Tempest

Registered User

Troy Tempest

Registered User
Part 3: Engine

The engine came built with the car when it was purchased. It's not something I would usually go for as I prefer to build my own engines, but I had a discussion with the machine shop that carried out the work and got all the sort of answers I expected from my questions.

I did have to correct the inlet cams as they were on the opposed heads, but this was due to the fact they were unaware that TDC cylinder 1 on the timing marks isn't cylinder one on the block. Swapping the cams corrected the issue and the engine came with no cam belt fitted, so shouldn't have been turned to cause any damage.

Some detail on the engine components:
  • S4 Engine Block
  • Ported 2.8 Cylinder heads with camshafts
  • 2.5 TDI oil pump conversion/upgrade
  • Mahle Motorsport pistons (81.5mm bore)
  • Forged connecting rods (although I have no detail on brand)
  • Silly Rabbit Motorsport main bearing girdle and ARP main cap hardware
  • Rosten Performance inlet and exhaust valves
  • FCP Performance valve springs
  • Rosten Performance titanium retainers
  • RS4 inlet manifold port matched to heads
  • Fluidampr crank auxiliary drive pulley

The engine as it came to me.

MRC exhaust manfolds

I sold the red cam covers fairly quickly, as they are't my cup of tea - red and blue dont go together for me.

There was a spare set of cam covers with the car, So i cleaned them down in my parts washer, then sand blasted them. My cabinet and compressor aren't amazing for blasting. So I'll probably get them re-blasted at some point by the powder coating company I use.

A before and after comparison

Before Cleaning the baked on oil/carbon

After, not too bad

People forget to clean out the breather traps, I don't fancy an engine full of aluminium oxide grit!

Breather cover plates cleaned

Engine built up with more parts including inlet and coil conversion

Gearbox mounted to the engine, fluidampr and timing covers fitted

The car won't be running a heater matrix in the cabin, so I turned some steel bungs on the lathe and then welded the outlets on the engine coolant pathways up.

Balance bar outlet

Transfer pipe outlet

When I posted about this in one of the B5 facebook groups I had a number of people tell me the car will overheat without the heater matrix fitted! I was also told that if I blank the matrix outlets I won't get any coolant flow. If you look at the self study document for the S4 you can clearly see that there is a short circuit path that allows coolant to circulate if the matrix were to get blocked.

SSP 198

I decided I wanted to upgrade the engine mounts, but wanted to make my own, rather than buying something off the shelf.

I got some aluminium bar stock in several sizes and some powerflex black series generic kit car bushes and set about making my own.

Bushing half

I never took any in progress images unfortunately, heres the two halves slotted together

One mount fitted - I ended up milling some more away from the bottom edge of the bushing half to stop them bottoming out.

Engine in on the mounts

There's probably quite a lot more that I could post about the engine, however some of those aspects - such as the fuel system, will be covered in another post.

Thanks for reading!


Registered User
Looking really good mate, I wish to have as much space you got there.
Love the look of the engine mate, well done.