Knackered old Porsche with loads less room for hair products
Discussion
Project Bugster Concept:
Sensible people would leave it at that, sensible people definitely wouldn't even contemplate a Boxster based RAID buggy, sensible people would know that you couldn't possible build a competitive off road competition vehicle from a hairdressers car, sensible people wouldn't have two other Porsche based projects on the go.....
Anyway I bought this last week:
An awesomely base spec 2.5L 1998 Boxster with a depressingly grey interior and a proper poverty spec with the exception of having climate control.
Clean isn't it.... that's because it's done less than 45K miles. I had said I'd only build this if I could fine a mint monocoque to do it with that was ripe for Rothmans livery - three days later this popped up. So basically it was fate.
The astute amongst you will note the major problem with the concept is that the rads on a 986/996 are in the corners of the bumpers so there's no way to build that actual concept because you'd never get the corners clear to allow for that amount of front wheel clearance/exposure...
So anyway here's the concept for frunk mounted rads on a 986:
The front of the boot will be removed to create an inlet air duct with the original rear rad ducts / fan carriers used to seal the backs of the rads to chimney out the bonnet in the low pressure area in the middle third of the bonnet skin.
There are a few challenges with this, the rad duct intake is going to be pretty small but its workable. The diffuser ramp angle in the feed side of the rad box is compromised by the rad position but by splitting the duct in two and with some pragmatism this becomes workable as two seperate rad ducts. The rad exits I can get to about 1.3X the rad core and into a low pressure zone so this really helps extraction. Bottom line is I can cool 150KW at 100KPH and that's all I need for a 2.5L M96!
Still a bit of work to do around this but the math does actually math so we're off to a good start!
Intrax are already in to do dampers so that's another piece of the puzzle:
They'll be slightly based on their existing 986 Rally product shown above but with a remote res and a longer body to accomodate more stroke and more spring length whilst increasing the amount of oil capacity to deal with the constant high frequency suspension movements this sort of competition brings.
I'll be going for a 75mm increase in ride height on the suspension with another 25mm from tyre with the expectation to run a 215/65/16 BFG KO3 as the prime tyre on a Braid Beadlock B rim. Probably a Winrace S like this:
As they support a bit more dish than the T variant I ran on the Cayenne and as such allow for more options in offset and caliper clearance.
The Boxster kinematics actually look pretty good for this, I'll need some longer control arms (which I can do by modifying GT3 Motorsport 996 arms) and some adjustable rear track rods, maybe some adjustable tuning forks too on the front but either way the kinematics stack up once a couple of rubber bushes are replace with poly or sphericals.
Front and rear bumpers will be tubular as per the concept and I'll do a multi-piece aluminium skid plate down pretty much the whole car, something which is really required due to the amount of lines etc. under the car. Finding some decent mounts for this will be the main challenge as it's not good squashing those lines flat with the skid plate so we'll need to beef a few bits up under there to take some hard landings.
Power will be from the original flat 6 M96 for now using the Audi 5 speed gearbox with a 240mm clutch and a limited slip diff. I might drop the gearbox 25mm (ala Booster) to get the drive shaft angles back but we'll see if that's actually required first.
I'll be removing the soft top mech and associated bits and fitting a hard top in the name of weight reduction, also the original seats etc. for some buckets and harnesses. I'm aiming to get this around 1350KG which with 200bhp and a decently flat torque curve from the M96 should be pretty decent on the gravel.
First order of business though is to give it a decent service, find a hard top and remove the soft top and then run it around for a thousand miles or so to make sure it's happy, healthy and ready for what's going to happen to it!
One thing is for sure though, it'll be much more of a challenge in this than the Cayenne! 2WD only, lighter car, way less durable in terms of suspension component strength etc. and definitely a requirement to be quick whilst also driving it not to break it!
Oh and if we need to get at the motor there's going to be a lot of dissasembly required so I better make sure it's got a snorkle so air filter changes aren't a two hour job...
Sensible people would leave it at that, sensible people definitely wouldn't even contemplate a Boxster based RAID buggy, sensible people would know that you couldn't possible build a competitive off road competition vehicle from a hairdressers car, sensible people wouldn't have two other Porsche based projects on the go.....
Anyway I bought this last week:
An awesomely base spec 2.5L 1998 Boxster with a depressingly grey interior and a proper poverty spec with the exception of having climate control.
Clean isn't it.... that's because it's done less than 45K miles. I had said I'd only build this if I could fine a mint monocoque to do it with that was ripe for Rothmans livery - three days later this popped up. So basically it was fate.
The astute amongst you will note the major problem with the concept is that the rads on a 986/996 are in the corners of the bumpers so there's no way to build that actual concept because you'd never get the corners clear to allow for that amount of front wheel clearance/exposure...
So anyway here's the concept for frunk mounted rads on a 986:
The front of the boot will be removed to create an inlet air duct with the original rear rad ducts / fan carriers used to seal the backs of the rads to chimney out the bonnet in the low pressure area in the middle third of the bonnet skin.
There are a few challenges with this, the rad duct intake is going to be pretty small but its workable. The diffuser ramp angle in the feed side of the rad box is compromised by the rad position but by splitting the duct in two and with some pragmatism this becomes workable as two seperate rad ducts. The rad exits I can get to about 1.3X the rad core and into a low pressure zone so this really helps extraction. Bottom line is I can cool 150KW at 100KPH and that's all I need for a 2.5L M96!
Still a bit of work to do around this but the math does actually math so we're off to a good start!
Intrax are already in to do dampers so that's another piece of the puzzle:
They'll be slightly based on their existing 986 Rally product shown above but with a remote res and a longer body to accomodate more stroke and more spring length whilst increasing the amount of oil capacity to deal with the constant high frequency suspension movements this sort of competition brings.
I'll be going for a 75mm increase in ride height on the suspension with another 25mm from tyre with the expectation to run a 215/65/16 BFG KO3 as the prime tyre on a Braid Beadlock B rim. Probably a Winrace S like this:
As they support a bit more dish than the T variant I ran on the Cayenne and as such allow for more options in offset and caliper clearance.
The Boxster kinematics actually look pretty good for this, I'll need some longer control arms (which I can do by modifying GT3 Motorsport 996 arms) and some adjustable rear track rods, maybe some adjustable tuning forks too on the front but either way the kinematics stack up once a couple of rubber bushes are replace with poly or sphericals.
Front and rear bumpers will be tubular as per the concept and I'll do a multi-piece aluminium skid plate down pretty much the whole car, something which is really required due to the amount of lines etc. under the car. Finding some decent mounts for this will be the main challenge as it's not good squashing those lines flat with the skid plate so we'll need to beef a few bits up under there to take some hard landings.
Power will be from the original flat 6 M96 for now using the Audi 5 speed gearbox with a 240mm clutch and a limited slip diff. I might drop the gearbox 25mm (ala Booster) to get the drive shaft angles back but we'll see if that's actually required first.
I'll be removing the soft top mech and associated bits and fitting a hard top in the name of weight reduction, also the original seats etc. for some buckets and harnesses. I'm aiming to get this around 1350KG which with 200bhp and a decently flat torque curve from the M96 should be pretty decent on the gravel.
First order of business though is to give it a decent service, find a hard top and remove the soft top and then run it around for a thousand miles or so to make sure it's happy, healthy and ready for what's going to happen to it!
One thing is for sure though, it'll be much more of a challenge in this than the Cayenne! 2WD only, lighter car, way less durable in terms of suspension component strength etc. and definitely a requirement to be quick whilst also driving it not to break it!
Oh and if we need to get at the motor there's going to be a lot of dissasembly required so I better make sure it's got a snorkle so air filter changes aren't a two hour job...
I take you followed the FCP euro build
https://www.fcpeuro.com/blog/rallye-cayman
A bit more trick for the rad solution, but the swapped calipers around to run smaller wheels
Also club auto sport do a GRP hardtop
https://www.fcpeuro.com/blog/rallye-cayman
A bit more trick for the rad solution, but the swapped calipers around to run smaller wheels
Also club auto sport do a GRP hardtop
e21jason said:
I take you followed the FCP euro build
https://www.fcpeuro.com/blog/rallye-cayman
A bit more trick for the rad solution, but the swapped calipers around to run smaller wheels
Also club auto sport do a GRP hardtop
Just had a read up on it, it feels like there are several fundamental problems with their rad setup (note the extra holes drilled in the nose in some of the later videos) but it does look very cool! As always more parts and more complexity is rarely the optimum solution - I mean mine won't be either but I'll have a fiver on the fact it'll function better than their setup.https://www.fcpeuro.com/blog/rallye-cayman
A bit more trick for the rad solution, but the swapped calipers around to run smaller wheels
Also club auto sport do a GRP hardtop
Running front uprights on the rear is a good solution to the track rod fouling a 15" wheel, you could also billet some rear uprights that kicked the track rod mount rearwards to but gave you the same kinematics to avoid having to remake the subframes and run a shorter toe arm. You could design this upright to be none handed with the track rod mount and caliper mount sharing the same bolt spacing and the track rod mount being a bolt on to allow you to account for bump steer when running different ride heights.
There's no one right way to do any of this as it's all one of and untested but leaning on modern FEA and CFD is a game changer when it comes to seeing how well stuff might work. It's also very sensible to lean on empirical data i.e. there are several rules of thumb which really help (like your rad exits needs to be larger than the core size by 20% or so).
One of the things I'm looking forward to most in this project is solving these sorts of challenges, love a good engineering puzzle
E-numbers said:
PPBB keeps delivering!
This looks like an adventurous project after the Cayenne- as if you re trying to up the stakes. Will be watching with interest, your builds are always inspirational.
Exactly that, this will be one of the first home projects that involves some fairly deep CFD and bespoke suspension bits that change the pickup points/kinematics of the original car. Much more of a challenge to build than the Cayenne which came with a huge amount of inbuilt capability in this area (and a beautiful double wishbone front suspension setup!).This looks like an adventurous project after the Cayenne- as if you re trying to up the stakes. Will be watching with interest, your builds are always inspirational.
RustyNissanPrairie said:
Subscribed!
But whats going to happen with the Cayenne and the potential class win?
The Cayenne is going to be run by another Porsche Clubber this year and I'm going to compete in the Boxster/Bugster. To be honest I proved enough with the stage podiums last year that I'd developed the car enough for it to win, the weak link in that is me plus I like the build as much as the competition - so time for a new build. But whats going to happen with the Cayenne and the potential class win?
C2 Class win should be possible....
TV8 said:
That is quite a project. Does it have a glass or plastic rear window?
It'll be glass / perspex in the hard top. I'm going to use a Porsche OE hard top rather than the various GRP aftermarket options as they don't fit well or seal well and the idea here is to create something at least a little bit dust proof! One of the potentially more challenging aspects of this build is going to be camber, or rather how to put a load more height into a vehicle that's designed to be very much at one static height and is on mcpherson struts on the front. The nature of a strut type suspension is that it has camber change during its motion, in the case of the Boxster it gains negative camber in compression and looses it in extension.
What this means is that if you extend the suspension, for example by increasing the length of the damper you end up with a load of positive camber.... something which is not good or useful in any way.
To solve this we can do two things, either move the upper pickup point i.e the top mount which in turn moves the angle of the wheel or extend the lower wishbone length which again moves the angle of the wheel.
Eurowise actually make a lift kit for the 986 which extends the damper by adding a section between the top mount and chassis and in turn moves the effective pickup point:
This is fine for circa 50mm of ride height increase but above this stuff starts to clash as you need more offset to compensate for the height. You also don't get any more travel.
Hence I need a better way to do it.... with a longer bottom arm. This means I can also keep the ball joint angle under control i.e. I can position it so the deflection is biased where I need most travel. So basically I need longer arms.
No one makes a longer bottom arm for a 986 but Porsche (and a few copy cats) do make shim adjustable arms for the GT2/GT3:
Which use a seperate inner bush carrier which is then shimmed off the main component to provide camber adjustment:
So the plan is to use the main component as is and then draw up and manufacture a new inner bush carrier which has circa 20mm more material on it before the studs. This will take a poly bush to allow for greater range of movement vs bonded rubber and the additional length means it will increase the effective length of the wishbone whilst still allowing the use of standard Porsche GT2/GT3 shims for adjustment.
This way the stiffness of the arm should remain pretty much OE and I benefit from all the positives of an OEM dust sealed ball joint etc. vs a spherical. I can also delete the camber adjuster bolts on the inboard and set the car up with shims which is far more preferable.
Some questions still to be answered around if the tuning forks will reach or not as I'm moving the centre bush outwards along with the ball joint but there are ways around that too!
If nothing else and if these prove to be too easily broken bouncing over stuff they will give me the geometry required to billet up a new arm but I suspect the loads on a softly sprung Safari esq car aren't that different to a Cup car doing kerb strikes at Spa!
What this means is that if you extend the suspension, for example by increasing the length of the damper you end up with a load of positive camber.... something which is not good or useful in any way.
To solve this we can do two things, either move the upper pickup point i.e the top mount which in turn moves the angle of the wheel or extend the lower wishbone length which again moves the angle of the wheel.
Eurowise actually make a lift kit for the 986 which extends the damper by adding a section between the top mount and chassis and in turn moves the effective pickup point:
This is fine for circa 50mm of ride height increase but above this stuff starts to clash as you need more offset to compensate for the height. You also don't get any more travel.
Hence I need a better way to do it.... with a longer bottom arm. This means I can also keep the ball joint angle under control i.e. I can position it so the deflection is biased where I need most travel. So basically I need longer arms.
No one makes a longer bottom arm for a 986 but Porsche (and a few copy cats) do make shim adjustable arms for the GT2/GT3:
Which use a seperate inner bush carrier which is then shimmed off the main component to provide camber adjustment:
So the plan is to use the main component as is and then draw up and manufacture a new inner bush carrier which has circa 20mm more material on it before the studs. This will take a poly bush to allow for greater range of movement vs bonded rubber and the additional length means it will increase the effective length of the wishbone whilst still allowing the use of standard Porsche GT2/GT3 shims for adjustment.
This way the stiffness of the arm should remain pretty much OE and I benefit from all the positives of an OEM dust sealed ball joint etc. vs a spherical. I can also delete the camber adjuster bolts on the inboard and set the car up with shims which is far more preferable.
Some questions still to be answered around if the tuning forks will reach or not as I'm moving the centre bush outwards along with the ball joint but there are ways around that too!
If nothing else and if these prove to be too easily broken bouncing over stuff they will give me the geometry required to billet up a new arm but I suspect the loads on a softly sprung Safari esq car aren't that different to a Cup car doing kerb strikes at Spa!
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