Scirocco Track Car Development...X-Flow Conversion preparation

So... having had a play at Curby on Sunday, I spent a couple of hours down the man cave tonight, doing the prep to take the head back off. First up was a compression test, to check the engine is still running OK. I have a suspicion it was slightly down on power yesterday - maybe just 20+ kg too much fuel in the tank slowing it down, but it wasn't getting to the rev limiter on the back of the circuit like it normally does.

Anyway, got all the top end bits stripped off tonight. Just the manifolds to come off and then I can pull the head off and measure the piston dish to give the Wizard Of Plymouth the data to CC the head correctly. Aiming for 11.5:1 compression to match the 298 cam. Hopefully I won't find any problems with the ring lands when I get in there. It's a high-ish compression engine running standard cast pistons, and has done a few races, and load of trackdays since it was built. Time will tell - hopefully I can get another version of it together, before it finally makes way for the 2L 16v lump that I've got all the bits for.

The cam of choice is a 298 degree Hydraulic job with 12mm of lift, from Sportcam in South Africa. Seems ideal for my needs. Nellis on here is the man to contact if you want to get hold of one.

 

So, a package arrived yesterday, from The Wizard Of Plymouth - a.k.a. Mr Hillclimber...

The X-Flow Head and cam are back, and the next step is to start working on the manifold. It was like Xmas morning unwrapping this lot!

So the spec is:
- X-Flow head based on mexican casting from an AFT 1.6 engine - ported by Mr Hillclimber and flow-tested using the wizard's sleeve flowbench I've since learned that this isn't the ideal casting to use, although it should be OK for the power target I have in mind. A german 2.0 casting from an ABA(?) would probably have been better to start from.
- Sportcam 298 hydraulic cam with 12mm of lift from Nellis on here - bargain price, including delivery from South Africa
- Custom manifold still to be made - aiming for 12.5" runner length, including distance from head face to back of valve. Expecting peak torque around 5500-6000 rpm. Manifold will be fabbed up by my mate Deano - the Rollcage builder and welder-artist!

The manifold will be made from the bottom half of the original manifold, and the flange from the top half, kindly milled flat for me by Steve R on here. The plenum end will probably be made up from the 2E manifold I have lying around, but it depends on what seems to fit the best.


Note that the tappet bores have been clearanced for the big lumpy cam lobes.




Inlet valves are the 40mm ones from a Mk2 scirocco, replacing the 39.5(?)mm X-flow valve.


Target static CR is around 11.75:1, but that should bleed off nicely with the long duration cam, and not end up killing the engine - fingers crossed!

Peak power target is 165bhp, but with the hope of getting closer to 170bhp. Hoping to redline it a 7500 rpm. Currently soft cut is at 7000 and hard cut is at 7200. Power is dropping off by then anyway.


In the process of doing this, I'm also planning to drop the radiator down and move it forward a little, to make room, and fit a different radiator that I've got in stock, from a Seat Toledo, as the position of the hose outlets will suit the X-flow better, I think. Current rad is from a Mk2 golf GTD, I think

So there's a fair bit of work to do, and a lot of figuring out how to make things fit. I'll try to keep this updated as I go through it - warts, c*ck-ups and all!

 

Right, now that the 16v is on the road, it's time to start on the track toy again.

Head was taken off a while ago, to measure cc of the pistons for the new head. Last night I moved the car into the work bay of the barn, and started stripping out the engine bay of the radiator, alternator, bits of loom, etc. Lots of room in a Rocco bay.



Overall plan is

- XFlow head and 298 cam
- Bike ITBs
- Remap
- Change front brakes, delete servo and linkage
- lighten bonnet
- stiffen front end of car with weld-in bracing
- cut front slam panel and move radiator down/forwards.
- modify front X-member to lower radiator mounting point

 

Packaging all this extra stuff in the front of the engine bay will present a few problems I expect. Dipstick is in the way, dizzy cap is close to the No.4 throttle body. (I'm wondering if a modded ABF dizzy cap will fit, and give enough timing adjustment without fouling on things) and some other bits will need a bit of thought.

Front engine mount might need to be moved - top rear of engine maybe - mounted to the weld in strut brace? If I chop the front X-member to drop the radiator, then I'll need to move the wiring, and I think it could weaken the X-member to the point where it needs more help supporting the engine. Better to move the mount to the top rear, rather than put extra strength and weight right out in front of the car.

Rear of engine bay should be much easier now, although some wiring will have to be moved if I tie in the brace to the scuttle panel, and the expansion tank will need to be moved, which is fairly easy. The battery is in the passenger rear footwell, so there's a fair bit of space in front of the passenger side turret, where the battery and Kjet airbox once were.

I was chatting to Tom Smudge about where best to brace the front end (he's got a better engineering brain than I have). I'll post up a modded pic with some of the ideas.

 

I'll be watching this with renewed interest now Mike....will save me some time when I come to do mine

 

This is kind of where my thinking is at after the conversation with Smudge. I've mocked these up so that folk can make suggestions and see what I'm up to.

Pictures borrowed from google images. The first one is actually a Mk1 rocco, but it's close enough.


The car already has a 6 point weld-in cage - Custom Cages CL4 kit. However, when Ian Carvell installed it, he also tied it to the A & B pillars, and roof support box sections, so it's holding the shell of the car pretty tight.


I think the key areas to stiffen are, I think...

1. around the wishbones, where the lack of a subframe allows for a lot of flex. I've got a single bar type strut brace on there at the minute, but I think an X-Brace across the wishbone mounts would make a difference. I reckon that cornering forces will be trying to push the whole front end, and particularly the outside wheel/wishbone/etc across towards the inside strut

2 Between the turrets, where the tops of the turrets will be trying to move around.

3. Where I'm less sure, is whether there's any benefit to adding more stiffness in front of the turrets - e.g. bracing to the chassis leg. On a rally car that's going to get a lot of hard landings, then I'd think that's a yes, but maybe less so on a track car. I don't want to start adding extra weight unless it's going to make a difference to front end strength.

4. Not shown... I was thinking of adding bracing behind the inner wings, up the door pillar and along the top rail of the inner wing. Again, I'm wondering if this is more for rough surface stuff. The aim would be to stop the front end flexing at the A pillars. Maybe it would be better to do this via a brace from front leg of cage to the front turret?


Wishbone bracing. In reality the shapes will be more complex, for clearance under the sump, diff, and probably some other stuff I've forgotten Need to have a careful look at clearances for suspension, driveshafts, and other oily bits.


Engine Bay Bracing. Not sure about the brace bars in front of the turrets down to the Chassis Leg. What do folk think?


Materials - The weld-in stuff will be T45 tube I think, for reasons of weight, and I'm thinking of having the Wishbone brace done in Ally, or maybe T45 again.

The turrets will have reinforcing plates attached for any braces to weld to.

 

Looks great Mike, looking forward to seeing you implement the work and get that X flow on a dyno! I'm hoping for big things (often thought about making an 8v cross flow on ITBs myself - just for the crack really and to really see what one can achieve compared to an ABF etc.)

 

I have never seen or considered adding in bars from the forward wishbone points up to the leg. But not to say it is not needed, but that pick up point is quite short so I would suggest on a track it should not see that heavy a load.

Would really recommend the lower wishbone strut brace you have lined up and the upper one too. When we fitted these to the mk1 it really did tighten up the front end. remember with the cross flow head you will have plenty of space to run the rear strut brace behind the head.

But if you can add in forward braces from the A frame loop through the bulkhead, too then I would suggest you would have it about perfect. Any more I would think would be just adding kg's to the car.

 

Thanks for the feedback so far.

Do you mean from the front wishbone mount to the front X-member?

I was looking at it tonight, and chatting to my welder-fabricator mate. He reckons that seam welding the front end would be enough, and that adding braces forward of the turrets probably isn't worth the extra weight. I was half thinking that way anyway, that the bracing lower down or further back creates less of a penalty in terms of weight distribution.

The reasoning behind the brace from the front subframe mount to the chassis leg (which might be right or wrong) was that the cornering force from the outside front wheel is trying to push that in towards the engine. The simple lower strut brace spreads that load across to the other. less loaded wishbone, but I'm thinking that bracing to the chassis leg will help to hold that in place. Feel free to tell me that's wrong though

On the other hand, the rally golf I bought from Jon Olds has a lot of extra bracing round the front, but then a rally car has to survive a lot of heavy landings, and soak up the battering that the sumpguard gets.

Taking Tony B's car as a bit of a guide, a lot of the front panel strength has been removed I think. I'll need to have a second look at the thread and check what he's done in there

 

No sorry, I was meaning if you where to run a brace the top of the strut tops to the main 'A' frame legs. Then a upper brace between the turrets and lower strut brace bolted.

I had taken it as read with the amount and standard of work you were looking at on this that seam welding was a given

I really don't think it is quite a case of this statement being wrong (to my mind it is not) but more a question of is adding XKg's at the front of the car worth what I suspect would be a small increase in strength. I really don't thing that for the sort of use you are planing it is worth the effort or added Kg's really. If you are willing to think of an other solution to this issue you could add a small "web" on the inside of the front wishbone point to give it some extra lateral strength without adding much extra metal.

the mk1 we built had a removable front panel (it was held on with a few self tappers and the bumper) as it made big engine work a lot less hassle at the track. and we did not think it would make much odds as all the forces etc are well behind that.

 

Cool - I think I understand what you meant a bit better now. Thanks for the input. I'm not completely sure where I can brace the wishbone bracket web. and a foot of t45/chrome moly tube doesn't weigh that much, but I'll have a look at the options, with your feedback in mind.

I'd have liked to weld those bracing bars in, but I think that'll make it really difficult to change the engine and box - it'll remove the option of dropping out the bottom.... on the other hand, the removal of the servo and brake linkage nonsense should make it easier to pull the whole lot out the top.

The car isn't currently seam welded. One of those jobs I've never quite got round to. You're right though... it should be, and the time to start is now, when the engine is coming out for the other mods.

Thanks for the point on the front panel. I was thinking that really it's just there to hold up the lights and radiator... and give the bonnet something to hook onto


This should give some good development ideas for the Mk1 Scirocco racer, although I'm subject to a more restrictive set of regs on that.

 

Glad my second attempt at describing it was better you don't need much bracing to add a fair bit of strength to a object. If you were to run a 10-15cm strip of 2mm steel along the inner edge of the wish-bone pick up point I would suggest that would go a fair way to help cut down any flex there.

we always did the engine in and out from the top on the mk1 till we had the removable front then it was all done like a mk2

it really was not any more than a few of the self tappers that hold the wings on that we used to fix the front panel on with. it coped all ok. Are you planing to weld in a brace on the bulk head between the supports for the steering rack? as this is a week spot on the mk1 shell?

the regs are normally only restricting the location of pick up points not say how the front end is stuck on

 

Remember if you use solid engine mounts the engine and box become part of the chassis and stiffen every thing back up as they wont bend or distort! Look at a 916 Ducati.

 

Thanks - will look at the options over the weekend.

Rack mounts were braced last year when I put the quick rack in.

Main regs differences for classic touring cars would be pickup points, 6 point bolt in cage, and no seam welding.

 

Was planning to be a big Jessie and leave it on poly / rubber mounts - Mr Hillclimber lower rear mount. Mike H custom top rear mount. Uprated end mounts.

 

Got hold of an ABF dizzy cap today... looks like that will work to give clearance under the manifold and ITBs


ITBs should sit about here....


Washer bottle bracket removed. Drilled out the spot welds.


Brake Servo and linkage removed... never to return!


My fabricator mate came round to size up the manifold job. Need to get hold of the silicon hose bits to mock it up, using some ally pipe I had lying around. and the laser cut flanges I got from DrunkenAlan

Tomorrow's plan is to take the engine and box out, and start seam welding in there.

 

Today, I had a final measure up for the ITB manifold with the tame welder (see Tylah Motorsport on Facebook) took the front suspension and brakes off, took the engine and box out and started prepping the engine bay for seam welding. I got busy with the angle grinder and knotted wire brush.


There are bits of the bay that are already seam welded, so I might add some more to those, but I'll be concentrating on the spot-welded bits, mainly.



Sorry for the poor quality pics... I think my hands were shaking from using the grinder all day - you wouldn't believe the thickness of underseal around the inner wing/suspension mounts!

 

So... a quick progress update. The seam welding on the driver's side of the bay is done, as is under the driver's wing. I had a few issues with the welding, and some of it isn't as pretty as I'd like, but it'll be strong enough. The biggest problem was the rubberised sealant and wax running out of the seams and body cavities as the metal gets hot with welding, which makes it difficult to get a good clean weld.

Meanwhile, I weighed the brake linkage and servo bits I removed, and they come to a bit over 6kg, according to my bathroom scales. I didn't include the master cylinder and reservoir, as obviously I'll still have something similar on the car when it's finished.

 

Mike, how are you looking to hold the dizzy cap on? do the location cut outs match up between the diffident cap's?

 

The location cut-outs match. The ABF cap needs modding with a dremel to allow the KR Dizzy spring clips to hold it on. It's the same as modding it to use on a KR dizzy in a Mk1 16v conversion, where it's needed to fit in the space between the dizzy and the brake fluid reservoir.

The direction the cap is pointing in is where it's sitting in the slots on top of the dizzy. I think it should fit under the inlet manifold OK, as that will be angled up slightly (sits at 90* to the head but the whole engine is tilted back when mounted. )