Archive for 2009

R888 Setup Tips

Posted: 22nd December 2009 by asteriskr in Rallye 16v

Blatantly lifted from Mike Nash‘s site:

Setup Advice for Toyo Proxes R888

What I would like to do is to offer some advice on tyre temperatures and pressures and how to achieve the best from our tyres when taking part in either trackdays or racing.

The R888 has a semi race construction (very stiff) and a race tread compound. The optimum tread temperature range is between 85C and 95C measured using a probe type pyrometer, and ideally a maximum difference across the tread of 9C. The maximum hot pressure we recommend is 40psi. Camber angles up to 5 degrees are permissible but the final setting will depend on tread temperatures. It is advisable to have as much positive castor as practical as castor induces a beneficial camber change during cornering. I recommend that the tyres be put through a heat cycle before hard use, this will scrub them in and remove any mold release agent.

The pressures you use will initially depend on the weight of the car, too little pressure on a heavy car can lead to over deflection of the tyre and subsequent failure.

Below are some basic settings:

VEHICLE WEIGHT | COLD PRESSURE | HOT PRESSURE
Very Light < 800kg | 17 – 22 psi | 22 – 29 psi
Light 800kg – 1000kg | 20 – 26 psi | 24 – 32 psi
Heavy 1000kg – 1400kg | 23 – 27 psi | 28 – 40 psi
Very Heavy > 1400kg | 27 – 35 psi | 37 – 40 psi

As a tyre gets hotter the pressure increases, this is due to the moisture in the air. The cold pressure you set to achieve a desired hot pressure will depend on the conditions on the day i.e. ambient and track temperature, wet or dry. If the day/track is cold you will need to start with a higher cold pressure as the tyre will not get as hot therefore the pressure increase will not be so great.

Hot pressures must be balanced side to side. Once the tyres have cooled you will find that you will have a difference in pressure side to side, if you have been racing on a right hand track you will find the offside pressures will usually be higher than the nearside.

Changing hot inflation pressures by small amounts can be used to fine tune handling.

  • Reduce Oversteer Reduce rear pressures or increase front pressures
  • Increase Oversteer Increase rear pressures or reduce front pressures
  • Reduce Understeer Reduce front pressures or increase rear pressures
  • Increase Understeer Increase front pressures or reduce rear pressures

Achieving the required tread temperatures will depend again on the conditions on the day i.e. ambient and track temperature, wet or dry.

You often here competitors saying “My tyres started to go of towards the end of the race”, this is usually due to the tread getting to hot.

The tread temperatures are constantly changing through out a race, hotter when cornering and cooler when on the straights and cooling even more when you are slowing to come into the pits. Therefore the temps you record in the pits will be lower than those during the race. So if you record temperatures within the range given above the probability is the temps will be too high during the race.

Increasing your tyre pressures will cause your tread temperatures to increase, more pressure stiffens the tyre’s casing which results in the tread having to do more work resulting in the tread getting hotter. Lowering your pressures will cause them to decrease.

Inevitably changing one thing will affect other things, the whole set up of your car is a compromise between anything that is adjustable.

Alan Meaker
Technical and Motorsport Manager Toyo Tyres (UK) Ltd
For more info on Toyo Tyres then please go to www.toyo.co.uk

Alternator Update

Posted: 21st December 2009 by asteriskr in Rallye 16v

Colin Satchells Alloy Alternator Pulley wheels turned up a while back, but I’ve been too busy to post up about them.

Pulley Wheels

Pulley Wheels

Few extra weights:

Steel v-belt alternator pulley wheel – 180g
Steel multiribbed belt pulley wheel – 495g (inferred estimate)
Alloy multiribbed belt alternator pulley wheel – 100g
Alloy multiribbed belt crank pulley wheel – 220g

That’s another 340g saving over the steel versions, so the total saving for my setup is 4.6kg of which I estimate that 1.5kg is rotating mass.

Alternator Weights

Posted: 13th December 2009 by asteriskr in Rallye 16v

photo

V-Belt Type

5.34kg Alternator, belt and pulley wheel
0.48kg Crank pulley
4.82kg Alternator
0.92kg Standard Bottom Mounting Plate and Tensioner
0.16kg Modified Tensioner
0.15kg Alloy Top Mounting Bracket
0.11kg Steel Top Mounting Bracket

Total: 5.76kg

Multi-Ribbed Belt Type

7.84kg Alternator, belt and bulley wheel
1.32kg Crank Pulley
5.44kg Alternator
1.06kg Tensioner wheel assembly
1.12kg Mounting brackets

Total: 10.02kg

A worthwhile and relatively cheap saving. Should get a further slight saving by moving to the alloy pulley wheels when they arrive. Started polishing the cast residue off the upper alloy mounting. I’ll get this a bit better finished and then it will be either painted or anodised.

photo

Cut the tensioner out of the plate. The plate mounting doesn’t fit on the 16v block so is useless anyway.

photo

Electric Maker

Posted: 11th December 2009 by asteriskr in Rallye 16v

Managed to pick up an 106 8 valve model type alternator during the week. These run on a v-belt rather than a multi-ribbed belt like the GTI engine. The difference between them is weight, the actual v-belt type alternators are lighter, but the real weight saving comes in terms of the rotating mass – the crank pulley wheel is almost 1kg lighter. Unfortunately I couldn’t get the mounting brackets from that breaker, so I had to try a different one for those and picked these up at lunch time. I suspect that having seen the amount of cast iron used in the mountings from the multi-rib belt fitting (which also uses a tensioner pulley wheel setup), this will be significantly heavier that the more simplistic tensioning system and cast alloy mountings on the v-belt type.

Engine builder Sandy Brown has pointed out that the downside to the V-Belt is that it is prone to inverting at high RPM, so the multi-ribbed belt is preferable. As a result I have been in contact with Cornish machining expert Colin Satchell, who is sending me some of his alloy multi-ribbed belt pulleys. So when these turn up I’ll get them fitted. Swapping alternators has been far from simple, but the weight advantages in total should make this conversion worthwhile.

A few other jobs are now on the agenda:

  • Remove the exhaust manifold, heat wrap it and fit proper brass nuts. This should help prevent some radiant heat damage and also improve engine performance slightly.
  • Fabricate a robust alloy heat shield for the oil level and pressure sensors. In addition to the above.
  • Remove the wishbones and treat with POR. These were the new one fitted last year and are already corroding.
  • Remove the air/oil cooler and fit a coolant/oil cooler. This is what the car had as standard and it is not getting the oil up to temperature due to over cooling.

Progress

Posted: 5th December 2009 by asteriskr in Rallye 16v

So the new Lambda sensor turned up during the week. Fitted it and was disappointed to find it made absoultely no difference.

New Lambda

So then spent the rest of the day trying other things. First up was checking all the vaccum hoses. I hooked them up to the trackpump and gave them a good high pressure blast, but nonw were blocked. So I did the same thing on the plenum vaccum inlets and they were all clear too.

Then I swapped the throttle body unit with all three sensors from the GTI on to the Rallye and as expected (but I wanted to be sure) that made no difference either. By this point I was running low on ideas, but decided that I would also investigate another issue thet car has been experiencing.

This is the oil pressure light coming on dimly. I first noticed it in spring but it didn’t seem to make any sense as it couldn’t be correlated to any other issues. I decided to investigate any way and found that the wires to both the oil pressure sensor and oil level sensor had become very inflexible undoubtedly due to the fact that they receive several hundred degrees of radiant heat from the exhaust manifold. They are normally protected by an aluminised heatshield, but this had been butchered at some point and there was no barrier to shelter them from the high temperatures.

So I unplugged them both and also disconnected the alternator and pulled this section of the engine loom up to the engine bay to make working on it easier. I cut out the heat damaged sections and fitted in new wiring (from a new spade connector back for the pressure sensor and I had to open up the special connector plug and use some new bullet inserts for the level sender and feed new wire back from these).

With an earthing wire from the connector on oil pressure wire to the body, I started the car up and it ran perfectly. I couldn’t really believe it. So I refitted everything and started fabricating a new heatshield for the wiring. Everything back in place, started the car again and it was back to sound like a Massey Ferguson. At this point I may have cursed a bit.

So back under the car! I disconnected the oil pressure and level sensors and earthed the pressure sensor wire to the body again. Started the engine again and it was still running badly. Disconnected the alternator and it’s fine. Weird!