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The Mighty MMI (man machine interface)

What makes a race car go faster? More specifically, a cheap road car based racer, not dissimilar to hundreds that get campaigned round our fair land by enthusiastic club-persons most weekends.
Power is a good thing, obviously. Suspension and brakes all help, of course.
How about seat mounts?
What, I hear you say, is he mad? Well, quite possibly, however here we will go over how to tune your driving environment so you can get the best out of your car, feel comfortable and be in control.

1. Feedback
There is something very important here and it involves your arse. When you have a car on the limit round a corner, you sense the onset of slip etc by relating what you see to what you feel. The more isolated you are from the car the more difficult it is to be precise, and I speak as someone who has spent some time drifting splendidly isolated Bentleys (but that’s another story, maybe later)
Having a very firm seat that is rigidly bolted to the car gives you the best possible feel for what is going on. When you turn the steering wheel on a road car, there can be a lag before the car moves and then the seat moves. This give a feeling of uncertainty and if its really bad (worn bushes etc) your ability to place the car precisely all goes to pot.
Now this is an important fact, your confidence and precision depends on the feedback you get through the seat and through your eyes. It also depends on the car doing exactly what you expect it to, but we will come on to that later.
By the way, don’t get confused if you see compliant seat mounts on a GT LeMans car, they need some isolation because of the rigidly mounted engine and rose jointed suspension, over a two hour stint that would rattle anyone’s nerves.
By comparison, our compliant mounted engine and suspension means we are quite well isolated to start with, so the seat gets nailed to the floor. By ‘nailing’ I am of course referring to the MSA compliant 3mm steel or 5mm ally mounting plates described in the Blue Book.
The mounts need to be able to take huge forces in case of a crash where accelerations of over 10g could have you bouncing round the car like a Nomex covered tomato in a blunt blender. 10g, that’s like expecting the supports to hold up the best part of a ton, the Blue Book spec (section Q) for seat belt mounts is 1.8 tonnes and for seat mounts it is 1.5 tonnes. The word ‘gosh’ springs to mind.
On the subject of seats, it is worth making sure your arse cant slide about and also that your shoulders are given a bit of support. That means you can feel the car moving directly and can concentrate on moving your feet and hands without also trying to stay upright and located in the seat.
Having said that, you must make sure you can move your arms freely to fully rotate the wheel in a mad panic (just try rotating the wheel whilst flapping your elbows like a manic chicken impersonator, you will be amazed how many bits of car are in the way).

2. Physiology.
Right then, that’s your arse out of the way, lets move on to thighs (which reminds me of a party near Turin, but again that’s another story).
Your thighs should be supported so that your feet rest naturally on the pedals with very little effort. Try relaxing your legs completely and see where they flop, if its in a reasonably good driving position then the job is done, if its with your feet under the pedals, you have some adjustments to make. The more natural it feels then the less likely you are to miss the pedal when it all gets exciting in a spin on the track.
Next we must look at the rest of your new office furniture. To get the max from the car and yourself all the controls need to be in just the right place, falling to hand naturally where you expect them to be.
The steering wheel should be at a comfortable (but safe) distance, elbows slightly bent but everyone has there own preference, whatever works for you is the key here. The dash and stalks, if used, should be clear of the wheel, I once span at Cadwell in an SD1, the frantic twirling of the wheel resulted in me bending the indicator and wiper stalks. They seemed fine during normal driving, when I had time to work round them, but in the heat of a spin they were in the way.
The gear stick should fall to hand easily and your elbow should not encounter any obstacles when shifting. If you need to modify it then make sure any welds are strong enough to cope with an angry driver putting their full force on it. The throw should be short enough for quick changes but long enough so you don’t get the wrong gear. Often with production based cars, replacing rubber linkage joints with Rose type joints helps quicken gear shifts because it feels better and gives you more confidence.

3. The view.
The seat is not only responsible for your arse, but also for your head, oh yes. With the seat in your chosen location, you must be able to have a clear view of the road. I know its obvious but it is surprisingly easy to forget whilst working late in the confines of your garage, you loose perspective in there. And 13mm spanners as well, odd really.
I built my first racer on the driveway and the view forwards seemed fine until I got to my first race, then I discovered I couldn’t see the apexes or the grid lines, with comedy results as you might expect.
Importantly, the gauges should be easy to read even when you are not looking at them. In the good old days gauges had needles and they were arranged so that all the needles were vertical when all was ok. We are very good at detecting horizontal and vertical lines, which may go some way to explaining tartan. If the engine overheats or oil pressure drops the needle deviates from the perpendicular and it is easily noticeable. These days we have simple warning lights, shift lights, oil pressure warning light etc These are excellent and work well using your peripheral vision, and lets face it, in the heat of the battle you wont be looking at the dash board.

4. Clearance.
If the view is good you then need to check for clearance, during this check anyone walking into the garage will think your are a sad git, hey ho. Sit in the seat, preferably with the harness on. Have your crash helmet on. Wave your fist around your helmet. Now you look really silly. There should be a fist size gap between your helmet and the padding on the roll cage and any other bit of car.
Try doing this whilst moving your head about. If you find anything hard which cant be moved, it needs padding, not soft B&Q foam which instantly crushes, oh no, you need high density rubbery stuff, roll cage padding is a good example.
If you have a crash, your neck will stretch, side impacts are the ones most likely to send you into a coma. Check there is nothing hard for you noggin to smash into. Also check for clearance to the steering wheel, whilst strapped in and you skid lid on, try to head butt the steering wheel, if you get within a fists width then you will hit it in a crash. I had a crash a couple of years ago on a Comp Safari, I skidded and hit a tree at about 40 or 50 mph which shortened the car by a foot. Sitting in the remains of the car afterwards it tried the above test and could not get any part of my lid within 4 inches of the wheel, yet in the accident I hit it with enough force to smash the visor.
This is serious stuff, we want serious fun, but to do that we must survive.

5. Air
Now you are comfortable, well secured, the controls fall easily to hand and your warning lights are sorted, we need to give you some air.
You need fresh air to your lungs to keep you awake and also you need to be at a comfortable temperature. Give some though for where the cabin air comes from, make sure there is no chance of engine bay fumes or exhaust getting anywhere near it. Remember that the air coming into the cabin must also leave it at some point, otherwise the flow slows down and any farts will make your eyes water for fifteen laps. Or is that just me?

6. Compromise.
Of course this theory is all very well and good, but some cars present a ‘challenge’. As an example lets see how this fine theory relates to my fine motor car, a Jaguar XJS.
Well, to tell the truth, badly. Sitting in the car as standard, my head hits the roof and cant rail. Add to this a crash helmet and a roll cage and I will have to remove four vertebrae!
In the standard seat, my arse is about six inches off the floor. If I mount the race seat base touching the floor my head will still hit the roll cage, this is not good.
It gets worse however, there is a large box section cross member on the floor that joins the transmission tunnel to the sill, its about 4 inches high. Hmmm.
The best solution is obviously a compromise, which is quite often the case with club level motorsport, and benefits from a bit of lateral thinking.
In this example I decided to use a high back seat usually used in off road racing, it has a near vertical back which means I can fit it with the rear mounts on the floor and the front mounts on the cross member. This gives a steep recline which I prefer and gives me a tad more clearance.
The steering wheel is replaced with a lighter weight racing item that has a sensible rim width, not the spindly rim of the standard Jag wheel. Its also a smaller diameter which improves the steering feel remarkably, this is because the same movement of my arm now has a greater effect on the car. I also lowered it by putting spacer blocks and longer bolts on the column mounts which made a huge difference in steering feel.
Now that I am sitting on the floor, the gear stick it a little high. Also, it wobbles too much due to the compliant rubber mounts it is on, again this relates to the need to have things fall to hand and behaving as expected, the wobble introduces uncertainty which reduces my performance (and it really is a performance). Removing the mounting plate and bolting the selector directly to the trans tunnel improves things no end.
Next issue is the gauges. There is a small rev counter which is not too easy to see in my peripheral vision. Just as importantly, the temperature gauge (these cars are renown for overheating) is a particularly useless linear bar graph type affair, as are the oil pressure, fuel and battery indicators. Not only that, but they are also wrong and have a very small movement between ‘normal’ and catastrophe. When the temperature gauge reads just above cold, but below normal, the radiator is at 90 C. That means that a reading of Normal would only be reached when the engine has seized and caught fire.
New gauges are in order but beyond my tight budget. So to make use of our horizontal line recognition I put a piece of thin red tape across the gauge, at the max temp that I was happy with in a race. When the needle reaches this point it makes a continuous line and is easy to see at a glance. Now the whole lot works quite well together. Most Autograss racers simplify things further by fitting a fog light on the dash as an oil pressure warning and leaving it at that.
I like my race cars, they are very individual and any other driver would hate it, but they are built for my own needs, and that’s the key. Everything is where I expect it to be and does what I expect it to do. Even in an emergency. The way you do things in your own racer may be completely at odds to convention, but if it feels right then it is right. And of course conversely, that £2000 carbon fibre seat may look the dogs, bit if it is uncomfortable then to you then its worthless.
Well there you have it, the interface between this man and his machine was sorted, and lap times fell.
The next big performance gain will come from practice.
In theory.

Simplicity is the key, with direct and positive feedback.
Jim's Autograss racer just has a big light for oil pressure, charging and a rather small rev counter just used when setting up.
This is a poor feedback environment, although very comfy.
This is a good feedback environment, and much more fun too.














©Ralph Hosier