Year two summary

I have had a wonderful summer going to every available track day with either the Westfield or the Sylva but mostly with the Westfield. The Westfield is more of raw track car. However the Sylva has had problems left over from the initial build that can only be fully explored on a track. It is the engineering of the car into a better state that keeps my interest going forward. The Sylva was reliable enough early in the year to go to Stoneleigh and Applecross total distances of 1500 - 2000 miles.

After the above trips the problems summarised were:

* Inadequate protection from the roll-over-bar.
* Throttle response giving unpredictable engine braking.
* Engine mounts that wanted to destroy themselves.
* Brake effectiveness was poor.
* Complaints from track marshals about fuel spillage from my tank overflow pipe.
*  Handling was poor going into and out of the hairpins (it scared me!).

If you follow the previous blog entries you will see that I have addressed all of these issues. Although I have spend most of my efforts this year on the Westfield I have spent a considerable amount of time recently on the Sylva. I was able to confidently drive around Kames lately and I think these videos summarises the progress better than words.

http://youtu.be/_uidzWq31YQ

http://youtu.be/FhXoJRMqCfQ

Contents
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Anti-roll bars ARB

I have been trying to improve my track times in the Sylva J15. My impression is there is some over steer going into a corner that is not to my liking. One of the ways of controlling this is to fit front and rear ARB's and play about with them on a track. I have times on a dry day recorded on my RaceChrono app in my smart phone. All I need now is to try out these ARB's and plot the difference.

Rear

Unfortunately Sylva Autokits don't do an ARB for the J15, however Playskool do one for the Westfield that is a very useful starting point for the design. I copied the design of  the two alloy pivots from the Playskool parts on my Westfield modified of course to suit the Sylva. The drop links are standard 100mm x M8 parts from McGill Motorsport. The chassis attachment point braketry was a custom fabrication. It is bolted to the rear chassis rail and the (old) Roll bar attachment points near the top of the coil springs. I wanted something that was simple to adjust when finished as I don't know how much compensation to set the bars up for. The roll bar is fabricated out of seamless spring steel 3mm wall thickness 19,mm tube obtained from Blakes Metal Store and bent using a hydraulic former with a 1040mm curved right angle at both ends..

Adjustment points

Drop link ball joint to wishbone

Offside arrangement

Nearside arangement

ARB Bearing arrangement



Detail of drop link

Rear fully assembled

Front

The front design is technically simpler than the rear (no custom extended mounts) but there is a lot of stuff to come off the car  including draining the radiator and removing the front clamshell. In my case the brackets mounting the radiator had to be remodelled to allow the ARB bar to pass between the upper chassis rail and the cooling fan. Also the alloy plate around the pivot point site had to be relieved using a dremmel and a chassis weld flattened. I used captive threaded studs welded from the rear to secure the pivot points, however bolts and spacers passing thu the chassis would have worked assuming they are long enough. The ARB bar shape has to take into account the relatively large steering angle change from lock to lock. The initial bend of the ARB was contacting the wheel on full lock so adjustment to the initial simple design was made. The bar is made of spring steel and ideally needs a hydraulic bender to implement.

General layout



Trial fitting the front

Radiator back in

Adjustment
I plan to base the initial settings based on an article and spreadsheet by "Keen tnkerer" on the WSCC site. I will be in contact with him shortly.

Contents
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Fuel overflow management

I have been hauled up on several occasions in my Westfield about fuel discharge during track days and sprint/hill climb events. This fuel overflow issues are exactly the same on the Sylva despite my previous efforts. This only happens when the tank is above half full. I fitted a Mocal valve which I thought would cure the problem as it has a dual function a) When the vacuum in the tank exceeds 0.5bar it will ingest air from outside. b) If however the tank pressure increases due to temperature effects (or sloshing) then the valve release in the other direction if that pressure exceeds 0.75bar. By this method the valve can act as a roll over valve and hopefully keep the fuel in the tank.

The problem occurs on track days when the fuel is warming up (so positive pressure) and the corners pull some g, if now the pressure release happens on a right hander then fuel is emitted momentarily till threshold of the valve closing is reached.

I have tried fitting a catch tank (fuel filter bowel) but this only delays the problem till the catch tank is overflowed. This results in dumping fuel from the catch tank onto the ground between sessions.

The answer may be quite simple, let the main tank overflow when positive pressure exists, collect the fuel and suck it back in when the fuel is used up and the pressure becomes negative.

Contents
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Brake bite

I have found the J15 as originally constructed has underwhelmed me in terms of the brake bite. In other words I am not getting the control leading up and into a hairpin in a Sprint track. I have had the need to emergency brake the  car and it did lock up the wheels fast enough but far too much pedal pressure for my liking.

The original brake design by Sylva Autokits specified HiSpec (on the front), my  brake setup is similar but uses 2 x 4 Pot Willwood midlights (on vented discs) on the front and 2 x VW Passat rears (Rally Design OEM handbrake callipers). The setup is common enough as I have something similar on my Westfield and I have no problems. I recently changed the front discs for X drilled and grooved discs similar to my Westfield. This had little improvement effect.

The master cylinders are the Sylva Autokits recommended 0.75" on the rear and 0.625" on the front with a balance bar configuration.

I decided to swap the 0.625" on to the rear callipers and fit a new 0.5" on the front. This by my calculation should increase the effectiveness by the change in the piston areas. This equates to 17% for the rear and 20% for the front.

I tried to get a Willwood part for the master cylinder but all I could get is a Rally Design copy at a reduced price. Apparently Willwood don't make them.

Only time will tell if I am on the right track. This is the third major change recently to the Sylva and I am beginning to feel I am at last getting somewhere.

The fourth and final change is to add ARB's - another winter project I think. I doubt I will get to try all this out properly before the spring. Early indications on a test day at Kames are promising. The effectiveness has improved but I still get a less than totally firm pedal. I think this may be due in some part to the pads needing time to bed in.

RD master cylinder

Contents
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Engine mounts re-design

Back in July 2013 I identified a problem with the stiff engine mounts as supplied by Sylva Autokits. It is a known problem with the Ford Sigma engine when you tune it, with a fast road cam, that will result in a resonance between 2-3000 revs. I successfully turned the right hand (offside) engine mount into a 6mm double rubber and metal sandwich with very little modification. The left had mount I was less successful with as the casting on the engine has very little surface area as it interfaces with the mount. My attempt to fit a 5mm steel plate at the bottom of the sandwich failed due to insufficient clearance with the chassis rail and the bottom of the gearbox.

After the near side failed recently I had a moment of inspiration. I decided to modify the Sylva Autokits mounting to give me adequate clearance for a full sandwich. This involved disassembling the bottom plate (next to the engine casting) with a 1mm cutting disc and removing 12mm from the fabrication and re-welding the bottom plate back on.

Failed sandwich rubber

New mount design note new base plate

Finished sandwich in place

Contents
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Throttle response

The next area of investigation was the Throttle response.  If you rev up my engine, esp when warm it currently rests at 2000rpm for a few seconds before settling back to the normal 900rpm tick over.

This has a dramatic effect on the ability of the engine to brake predictably going into a corner. In addition the Ford ECU has no feedback from the brakes so it makes it's own mind about the engine revs, emissions being the priority.

I have decided that the Idle Control Valve (ICV) is the culprit. If you pull the ICV during it's high idle the engine settles at a rate set by the butterfly end stop screw on the throttle body (usually about 500rpm). The ICV is a servo type valve controlled by the ECU, by changing the pulse width thereby modulating the current to it. By observing the waveform to the ICV on an ossiloscope it is about 150uS for a tickover of 1000rpm and increases to 300uS at 2000 rpm. By empirically adding a 33 ohm resistor you can slug the tick over response completely yet maintain a steady 1000rpm but will not surge. The down side is I suspect the emissions will be well out of order (thinking MoT in the future). I therefore decided to only add the resistor during braking. By adding a relay as follows you can force a specific idle during braking.

The down side of this modification is that  when the engine is cold the idle is well below normal when braking and can result in a stall.

An initial test drive with this mod looks extremely promising, returning drivability thru engine braking. However during a day out at Knockhill I came back with an engine that would not start properly. During subsequent troubleshooting I discovered that the ICV had failed almost completely but not badly enough once the engine was started but still displaying the erratic tick-over. Replacing the ICV with a part specifically recommended for the 1997 Puma 1.7 made a dramatic cure to the throttle response negating the need for all of the above. Lesson learned: Don't use cheap ICV's from ebay. However I have learned a lot about the ECU and it's control loop. Proper ICV's are adjusted to match the ECU for that model so you must insert the correct ICV part. Also the health of the closed loop system affects the throttle response. An air leak in the inlet or exhaust can affect the signal from the O2 sensor and therefore in turn affect the ICV setting and therefore throttle response.

Contents
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Bike rack

I have spent a lot of time thinking how I can get my road bike on the back of the Sylva. Here is the fruits of my deliberations. I doubt there is a queue out there for the design. The parts were fabricated in 35mm sq  section ERW 1.5mm wall thickness to keep the weight down. The rear plate is 12mm thick alloy. Just a bit of fun for the holidays.


Parts fabricated in 1.5mm ERW

J15 Bike rack

Contents
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Helmet loop

One of the many issues concerning fitting GRP seats in a J15 is the roll-over bar helmet clearance. I took advice about hill climb/sprinting the J15 and the verdict from a track-side scrutiniser was that the helmet clearance to the roll-over bar was insufficient. Apparently for MSA road going class this is a grey area but the advice was "don't do it".

The other issue is the supports for the roll bar have not been installed by me as the rear tub has to be cut. I think the one bar to the rear chassis leg would have less impact on the rear tub.

I recently obtained a special seamless tube from Jeremy bent in a loop to create a helmet loop. I made templates out of plastic ducting left over from the Virgin Broadband install.

I have now welded the loop in place  I got a piece of 37mm high tensile seamless tubing 2mm wall thickness from Blakes Metal Merchants which made up the rear stay.

The rear chassis leg support bracket strength has been enhanced by an extra support to link it to the lower chassis leg.

Creating templates

Welded loop

Chassis leg attachment point

Some chassis paint

Rear stay fitted

Contents
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Re-visit Dynamometer

There was a problem with the last power plot I did last year as the throttle body butterfly was not opening fully. This visit back to Sitech Racing was to validate the update to the throttle body linkage. Here is the plot from my visit in August 2013: http://sylvabuild.blogspot.co.uk/2013/08/ecu-re-mapping.html

The standard engine produces 125bhp at the flywheel so no increase in power was observed in August. Since then I have fixed the butterfly versus pedal position.

You can clearly see the maximum power has increased by 43bhp to 155bhp @ 6700rpm a most agreeable result for the cost of a sift in pivot point in the throttle linkage.

Contents
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Headlight covers

One of the key aspects of the J15 is the retro classic look which would not be complete without the headlight covers. I have pondered for at least the last year on how to mount them or weather I would be better off not fitting them at all. The build guide is not a lot of help. One of the forum members suggested fitting with 3 off fixings each side using alloy right angle brackets and rivnuts.

While I agreed with the three fixing approach. I did not want unsightly alloy brackets. I opted for straight brackets made of 5mm thick GRP board (which I had lying about). The board was fashioned into 15mm x 30mm plates with a 5mm rivnut in one end. A slot was then cut into the GRP bonnet (hood) around the extremity where the Plexiglas cover was to attach. To finish them off I mixed up a small quantity of Gel Coat to make them blend in. To make the ss bolts captive I used M4 nylon washers over the M5 thread. If they work loose at least I won't loose the bolt.

GRP board with rivnut fixing

Gel coat added

Finished headlight covers

Contents
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