Project Update
Hi Everyone… We’re Back!
Well it’s been a busy couple of months here at
Autotechnica
Andy, Ben and the team have been working very hard on Project Cupra and we’ve made some great progress along the way. During the last update we got to the stage of cutting out the boot floor plan to make way for the Audi S3 Rear Axle. This was a scary moment of no return but it all went well.
The welding and cutting works have been done by Andy’s mate Dave from
Auto Solutions. Dave is an experienced welder who did an excellent job fabricating up a new box section for the boot floor. This guy is a real character and made us laugh when he did the first cut, he turned towards me with a rather large angle grinder in his hand and asked… are you nervous lad? Err… and before I had a chance to reply, a large whizzing sound erupted as he started cutting! Lol
So following on from the last update, the next job we looked at was to take the gearbox out, this had to be matched up with the front transfer box that we got from the R32 donor car. This was easier said than done and took a little while to sort but we got there in the end.
As Cupra Kung Fu had only done a very low mileage then naturally we were reluctant to change the gearbox for one off an S3/R32. It’s also unlikely we would have ever found one in the same condition without paying top dollar, so we thought we’d give it a go with the existing unit.
Ben started to strip down the box taken off the Leon. It’s amazing how many cogs; nuts and bolts there are in these things! A big boys Meccano Set!
Photo below shows the engine bay once the gearbox was removed; exposing the Loba clutch and single mass flywheel that we installed just a few months back:
Photo below shows the GT3071R Turbo after we had removed the gearbox:
We recently bought a Quaife limited slip differential of which we had fitted just before XMAS when we went to REVO Stage 3. Most of the high performance cars on the road (or at least FWD cars) will be fitted with some sort of a limited-slip diff (LSD) and they are installed for a good reason.
Without an LSD, if one wheel loses traction and starts to spin, all the power is transferred to that wheel. This not only limits your acceleration, but it also upsets the handling, especially in front-wheel-drive cars, by causing severe on-throttle understeer. Not good. An LSD helps eliminates this.
Depending on its design, either by forcing both wheels to turn at similar speeds regardless of which has grip, or, in the case of the Quaife ATB diff, do the opposite of an open diff and transfer the power to the wheel with the most grip. So while, in theory, an LSD offers an advantage over an open diff, the question is, will it actually make that much of a difference to your car? Will your car be noticeably faster with a diff fitted; faster than if the money was spent on performance engine upgrades?
Well we were pleasantly surprised by Quaife’s engineering and had found a big difference in the car’s performance and road handling. When you go anything beyond 300 horses then you really start to struggle with the traction and will also find the cornering can be a real challenge. One has to realise however that all LSDs are not a complete solution but more a compliment to your handling.
If you thrash the car with big power on a FWD then of course both wheels will start to slip and spin against the tarmac. Having a decent mechanical LSD does however
help to prevent this issue by transferring the power to the wheel that has the most traction. Straight line drag races will give the same annoyance, but it is more the cornering at high speeds where it comes into play. The best way to describe the difference between them is being pushed into a corner with little confidence that you’ll come out the other side, but with an LSD it’s a bit like being pulled around the corner with a big rope.
You can instantly feel the difference when an LSD is doing its job. The traction of the wheels crosses over from one wheel to another and the whole process is done in milliseconds backwards and forwards until you find the grip the car needs, or at least until you made it clear out of the bend.
With AWD, the Haldex system transfers power to the rear wheels when the car needs it the most. Having power to all wheels makes a massive difference to the car’s grip on the road, keeping the LSD in the mix will complement the situation giving better control of the front wheels.
It was real shame at the concept that we would lose the use of this fine piece of engineering having only had it for a few months, so we contacted Quaife to see what they could do to
help. As it turned out they do in fact manufacture an LSD for the R32 and S3, so we did a little research to see what options there were.
We contacted Dave King from
Quaife, one of their technical engineers who advised on a workaround for our project. Basically the gearbox used on the Cupra MK2 and the S3/R32 are of a similar design, but there are subtle changes in the outer casing i.e. the mounting holes that are used when bolting on the front transfer box (the gearing that transfers power to the rear wheels)
In order for the LSD to reach the gearing on the front transfer box, we had to take apart the unit and replace the housing for one with a longer body (model off the AWD system) Dave and his team from Quaife were very helpful and were able to provide us with a new housing. They stripped it off another unit they had on the shelf so were able to send it up to the team at
Autotechnica in a matter of days.
The photo below shows the FWD and AWD units:
Photo shows the inside of the LSD, the helical gears which transfer the torque bias from one wheel drive link to another. A real piece of engineering!
So we put the two casings side by side and you can see the difference between the old and new. The housing on the right is the old unit and the one of the left is the new one:
Photo below shows the new housing fitted to the gearing:
Once the new diff was installed then we looked at the re-assembly of the gearbox only to find there were no fixing points on the casing for attaching the front transfer box… rats! So these subtle differences we mentioned earlier are somewhat fundamental to the installation of the AWD running gear!
Well all we had to do was to order a new middle section casing for the S3/R32 which obviously does hold the correct fixing points in all the right places. Most car makers will always skimp on the manufacturing costs where ever possible and therefore will make most of the parts fit as many of their vehicles as possible. The main assembly of the gearbox between the various models all share a lot of the inner workings and therefore replacing the casing alone was all that was required to turn this Cupra gearbox into an AWD version.
Photo below shows the inner side of the two casings, no prizes to guess which one the new unit is! On the inside of the casing we could not see any difference in its construction, essentially they are both the same design:
Casing then turned over, spot the difference?
Photo below shows the two units, the newer casing has the mounting holes for the front transfer box:
Once we put the gearbox back together again, we were able to install the front transfer box:
Closer look at the transfer box:
Photo below shows the rear view of the box assembly; the triangular spindle wheel drives the propshaft that sits underneath the tunnel of the chassis to the rear diff.
New bolts and fixings were used, advisable when re-building the box assembly:
And now for fitting! The hefty lump was raised up on the hydraulic lifter ready to fix into position:
Now now boys!
We also had to find a replacement driveshaft for the front offside side wheel. Once we’d fitted the transfer box into position, we realised that Cupra’s driveshaft was going to be too long. We went on the internet searching for a couple of weeks until we found an OEM unit.
These type of components are actually quite hard to come by because there are far fewer S3/R32s out there than the standard Audi/VW models. We looked at buying an aftermarket version but in the end we decided it would be better to find an original part considering the increased power being put through the wheels and we were unsure how strong the 3rd party units would be:
It was a bit of a milestone getting the gearbox fitted successfully. Once the transfer box was installed it was all a pretty tight fit. We had to reconfigure some of the hosing from the GT3071R Turbo to make space for the drive shaft assembly to the front offside wheel. Andy got a local company to fabricate a custom braided hose connector which now fits perfectly.
Nothing is ever straight forward with these type of projects and we have on many occasions had to tweak a few things here and there to make it all fit together, the joys of mechanical engineering!
Glad we got that job out of the way!
Now for a short break while the team get to play with a couple of RS4s for the day, definitively needed to test drive those new windscreen wipers!
A little while later we pressed on with the next phase of the works. Dave from
Auto Solutions was busy laser cutting up a new box section for the boot floor plan so we had a couple of weeks to get the car ready for his return. There were two areas that needed to be prepared for the welding works, the first being the boot floor plan and the second was the tunnel underneath the chassis where the propshaft sits. The prop has an elbow joint approximately half way along where it is held up against the chassis by a heavy duty bracket. Mounting plates are usually built in with the S3/R32 but were not present on the Cupra so we ordered these in ready to be installed.
Welding underneath the car causes a lot of heat and we therefore had to strip out the interior to avoid the carpet from going up in flames! Dismantling the car’s interior was an awkward job but one that had to be done, a little pain for a big gain! I actually volunteered to do it myself as this would give the guys some breathing space to get on with other things. I went along one Saturday morning and it took me a good few hours to sort.
Gurr you wouldn’t believe how awkward SEAT interiors are to take out, mind you I’m sure most cars are the designed the same. To remove the carpet and underlay we had to strip out nearly every piece of plastic trim and panel there was! It was quite daunting to see the Cupra in so many pieces, not a sight we really want to see again!
Photo below shows me in action…removing the centre console which luckily came out in one piece. I still managed to trash one of the other panels though! easily replaced.
Small tip, front seats are a nightmare to remove when taking out through the front or rear doors. We ended up taking everything out through the boot which was a lot easier. The Darth Vader like rear seat covers on the Cupra R are made of a glossy shiny black plastic and can easily scratch if not removed carefully. Luckily all went well and we soon got everything out.
Write up in progress...