Over the last couple of years I've been slowly building a one-off track-day car which mates an S4 v6 to an Esprit v8 chassis and GTM composite tub. I've maintained a build diary but not posted anything yet, so the project is now pretty advanced.
The spec is:-
Audi S4 V6 engine - will be chipped to 320bhp
Lotus Esprit V8 suspension and front and rear chassis members
6mm thick steel spine joined to the front and rear sub frames and tub
Brembo front and rear brakes
Chassis and Engine Frame
Sizing it up...these are a few early photos of when I was working out how it would all go together
When I'd worked it all out it went to Jim Walker Motorsport in Nanpean for the basic fabrication. This is how it looked when it came back from Jims.
car view side
car view frontRear end on 15th March 08. This is now in a more advanced state. I've added additional bracing bars and a cross member. It looks crooked in the picture, but its not, (everthing is tack welded here).
Shows the mounts for the coolant expansion tank and the vacuum reservoir
header tank etcThis is the cross-member with mounts for the expansion and vacuum tanks
Engine out......again. You get a better view of the rear subframe. All the unpainted areas are just tack welded at the moment
Engine and Gearbox Mounts
I wanted to try and get the engine as low as possible in the chassis so the bottom of the sump was level with the lowest chassis tubes. After much searching through Audi parts manuals and having a chat with Doug at MRC I decided to use shorter mounts which are normally used at the gearbox end. This meant fabricating a cup for the mount to bolt in to. In this picture the original mount is on the left. Doing this has lowered the engine nearly two inches.
Gear Linkage
The lever mechanism inside the car is from a Toyota Starlet and I have fabricated a complete linkage at the gearbox end
This picture is the mk 1 but after much debate I decided to change the 5-speed type 012 gearbox for a much later and stronger 6-speed 01X. This is the gearbox commonly used in the 3.0 V6 TDi cars, although this particular one came out of a 2.4 cabriolet because it has much better ratios than the ones from a diesel and its the same type of box.
Pictures of the new 01X gear change mechanism (this is on the side of the box rather than the back on the old box)
Exhaust System
I used the original Audi downpipes, removed the pre-cats and changed the angle so that they turn outwards. The silencer itself is from a Porsche 996 Turbo/GT2 which I have turned through 90 degrees and modified the inlets on so that the exhaust enters from the bottom directly into the cats (which are built into the first part of the silencer). The exits from the silencer - which currently point upwards, will curve round and back into the tailpipes.
The silencer is mounted onto outriggers I welded onto the main chassis rear hoop - you can see these at the front of the next photo. It is amazingly light, (I suppose Porsche needed it that way because it hangs so far out of the back of the car on a 911) and I've kept it as tight in as possible to the rear of the car to reduce any rear overhang.
The whole thing is sat on rubber bobbins to isolate it from the chassis. These are spaced away from the silencer so they don't get too hot. Everything will have massive heat shielding around it when it is finished.
Intercoolers
The intercoolers I've used are much bigger than the standard Audi items. I've based mine on two Nissan Pulsar GTi-R coolers I got off eBay.
I then had these modified so the outlets were where I wanted them and spent a fortune on silicone hoses and large bore aluminium pipe to connect them up.
The intercoolers are mounted in front of the rear wheels on rubber mounts. Air will be ducted from side vents, through the intercoolers and then blown over the turbos to help keep them cool.
Electrics
I have the complete loom and bits from an Audi S4 and I intend to use this as much as possible. The problem is its HUGE and weighs about 25kg.
Because the loom is built for the engine in the front of the car I've had to extend 37 wires from various engine sensors, injectors, etc, etc, so I've made a loom extension which will be soldered in.
As of 12th October 08 I've fitted a lightweight Fidanza flywheel, changed the gearbox to an 01X 6-speed and the engine is now running
The fuel tank is now fabricated and in place (sorry I'll take pics when I take it out next) and a strengthening cage has been made to put the strength back where I cut the rear box section out of the GTM tub. The tank is fabricated in aluminium with a swirl pot built into the sump which mounts the standard Audi pump. I'm also using the Audi fuel guage sender. The capacity is 64 litres so it should give me a decent range.
I've also made a crash structure to prevent minor accidents impacting straight into the gearbox and pushing the whole engine forward right into the fuel tank (although it is behind the bulkhead). I'm going to make up some stainless steel cable restraints to help prevent this in a bigger impact. The aluminium structure is from an MG ZT and weighs very little and will also form part of the mounting system for the body.
To see the video of the first engine start go to the Youtube link below. It started on the second turn of the key and after a couple of puffs of smoke it ran pretty clean and smoothly - not bad for an engine that hasn't run for nearly 5 years. I'd turned it over on the starter a few times to get some oil round it before putting fuel in and after the tappets had pumped up it a quietened down nicely. Its running a little rough because I didn't bother putting the clips onto the turbo hoses so it was leaking air into the inlet - it will all be coming apart again soon, but rest assured when I build it for the final assembly it will have all the clips in place.
Listen to this with proper speakers or through headphones so you get the full v6 engine noise !
www.youtube.com/watch?v=V7EG7fl-GLY
As you can see from the end of the video I've still got to do a little bit of tidying of the loom to do because it needs moving off the roof of the car(!!!). But now the engine is running I can move onto the next big job - re-doing the front with the Esprit V8 power steering set-up and piping it all up.
