Royally shafted

Racing. It's a game of extremes. 

You are either going as fast as you possibly can, or trying to stop as quickly as you can. There is no "cruise" mode in a race car. Because of this, everything in the car gets subjected to the outermost limits of their tolerance pretty much all the time.

It is said that if you ever want to find the weakness in your road car, stick it on the track for a couple of laps. Very soon the weakness will become known. This, I have witnessed first hand on many a track day, when seemingly robust and well conditioned cars end up disgorging their innards onto pit lane.

That said, we build our race cars to withstand the tortures of the life to which they are destined. 

Although, recently I have been wondering about this. You will recall that I have been having a few issues with cracked front disks. This has now become a regular one-per-race scenario, with the last one presenting a fairly catastrophic failure that stopped just short of a piece actually breaking off the disk. You might be thinking at this stage that, surely, this is rather dangerous and just a little foolish. You would be correct on one account. Racing is a slightly foolish endeavour, especially for us amateurs. As to the danger, interestingly, all these disks have cracked after being abused. I actually heard one crack a couple of race days back while we were sitting in the holding area after our race. Granted, this scenario might well be different were we doing a three hour enduro, but for our sub-15 minute sprint, the disks actually hold up, until they start cooling down.

New extreme sport. How badly can you break stuff?

Ok, so in defence of the disks, these are not exactly high performance racing components. More like off the shelf, cheapies that we slot ourselves. The reason is two fold. Firstly, I can buy ten of these for the price of a high performance race item, but, more importantly, these disks are from the Toyota Rav4, and not a whole lot of race equipment manufacturers make high performance parts for this particular run of the mill shopping trolly. 

Anyway, we are going to be adding some brake cooling ducts soon to see if that helps. If not, we might have to look at changing the fronts for something that has a little more support in the performance market.

All of this is, naturally, due to the upgrades we did on the car a while back. Remember, we took a perfectly functional and reliable car and bolted on some go faster goodies. The knock on effect has been quite educational to say the least. 

Another casualty of the increased power and torque was one of my rear half shafts. The half shaft is a particularly important part of the car in that it connects the output of the gear box to the rear wheels. Break one of these and you are effectively in walk-home mode. Which is precisely what happened on a Sunday drive some time back. Thankfully we were near home and a quick tow avoided embarrassment. The shafts I use need to be lengthened, which necessitates a sleeve being welded onto the shaft to join the two parts. Unfortunately, the act of welding on the shaft creates a point of high stress in the metal and this is where the shaft had sheared off.

Another entry in the Extreme Sport of Breaking Stuff

Craig did a fine job of welding up the broken shaft, but I had this niggling feeling, driving to race day the following weekend, that I might be in for some more breakage. 

And so it was. On lap three of the qualifying session, as I speared into turn one and snatched third gear, there was a thump-clatter-clatter sound that I had heard before. Sure enough, as I exited the corner and come on the power, nothing happened. I coasted to a stop on the inside of the corner and suffered the ignominy of being towed off the track for the first time ever.

Closer inspection confirmed my fears. I was fully expecting the same shaft to have broken again, but it was the other side one this time. The failure, however, was exactly the same, a clean break at the weld point.

This provided me with a bit of a dilemma. I would need to get the shaft repaired so that I could drive the car home again, but should I fix it and race on it? The chance of another weld giving up was pretty high, going on the current experience. However, it was a race day and we were there to race, so I decided to give it a go. The shaft was duly stripped off and handed over to Steve at Harp Motorsport, who set about making a new sleeve to join the two bits of shaft. While we were inspecting the damage we noticed a spiderweb of fine cracks in the remaining intact weld. It was only a matter of time before the shaft broke there too. Clearly they were being pushed way outside their comfort zone.

Track side repairs, a necessity in this game of racing

The shaft repair took a little longer than anticipated and I ended up getting the car finished an running again just as the leaders of my race crossed the finish line. In retrospect it was probably just as well. Later inspection would show that the remaining weld on the shaft that had previously broken was also mimicking a spider web.

I slunk off home, smarting from the three most expensive laps of racing I had ever done.

Thankfully there are all manner of clever engineering folks around town, and within a week Craig had organised me a set of custom made drive shafts. The chap who made them would not tell us what he made them of, but assured us that we could enter the car in a drag race without any problem. Judging by the beefiness of these things, I tend to agree with him.

The old versus the new

New beefy shaft ready to be fitted

The new shafts were duly fitted, and not a moment too soon, as the next race day was looming awfully close on the horizon.

We had been treated to some of the best weather Cape Town had to offer over the week leading up to race day, so it was no surprise that rain was forecast for the actual race day. I arrived good an early, cleared documentation and managed to qualify well, but as we sat in the holding area before the race, the rain began to fall. A couple of slick shod cars pulled out and headed back to their pits. By the time we were waved onto the track it was well and truly wet. The race, if one could call it that, proceeded without major incident and was won by a Porsche followed by a string of other Porsches. I wonder if they have some kind of driver aids to deploy in these conditions....

As it usually happens, the weather cleared up straight after our race and everything dried out nicely. By the time our second race rolled around, everybody was back on slicks and ready to do proper battle.

I had drawn fourth on the grid and had a Lotus 7 and a pair of Porsche GT3's up front in class D. Behind me were a few more GT3's and Steve who was piloting the Harp Mazda MX5 Turbo for the day. 

By the start of turn 4, on the first lap, I had been overtaken by a Porsche and Steve in the MX5. Now, the Porsche I could understand - it was an RS after all, but the MX5 was a little more difficult to stomach. That said, Steve is an old campaigner and can probably lap Killarney faster in a wheelbarrow than most of us in our race cars. Either way, I was not particularly happy with this position and decided to try for a bit of a comeback. This, while also keeping the remaining GT3 firmly behind me.

I quickly realised that I was much quicker on the straights than both the MX5 and the Lotus, and, it turned out, the GT3 behind me. This provided a bit of wiggle room, so the usual plan was hatched. Catch up on the back and front straight, hang on through the twisties and then pass coming out of turn 4 onto the back straight again. This would give me the front straight to make some headway and hopefully stave off an return challenges. Steve is, of course, a wily old bugger and made his MX pretty wide, but in the end there was no substitute for grunt and I watched him rapidly shrink in my mirror going down the back straight. Hennie in the Lotus suffered the same fate a lap or two later, and then it was all about staying ahead of the GT3. We had a great battle, as the GT3 was better under braking than me, but I was faster on the straights than him. In the end I managed to hold on to my position and finished the day with a fourth place in class D. I was the Harper fly in an otherwise all Porsche bottle of class D ointment.

I would like to say that everything had gone smoothly for the day, but sadly I have cracked yet another disk. Those cooling vents are now absolute top priority! Other than that, the car is going exceptionally well and is regularly clocking 22's.

With a new set of tyres and a bit more practice that ever elusive 21 should be making its eventual appearance.

The only problem I can foresee with achieving this goal, is that the next will be to crack a 20. Doing 20's around Killarney is pretty serious business and the air starts getting quite rarified up at that end. Knocking a second off a lap time when you are doing 27's is not that hard, but as the number shrinks, the effort required to knock time off exponentially increases. 

But then, in the last 18 months we have managed to slice close on 4 seconds off the Type 6 lap times. All we need is another one. Just one.

I mean, really, how hard can it be?

The one that wasn't...

I would like to say that race day dawned bright and clear, but that would be a lie. In fact, it could not be further from the truth. The past few weeks in Cape Town have been more akin to living under a waterfall than the shadow of Table Mountain.

I woke early having readied the car the previous night. We were scheduled to qualify fairly late, so there was no tearing rush to get to the track. Even still, it was dark at 7:30am when I rumbled out of the garage. The darkness was partly due to it almost being the middle of winter, but mostly due to the brooding dark clouds that were rolling in over the mountain. I decided to chance the weather and left wearing my usual peak cap and glasses. Within a couple of hundred metres I was severely regretting my decision. The rain had started to fall and at any decent speed it felt like somebody was tossing iced ball bearings at my face.

I pulled into the petrol station to fill up and quickly hauled out my helmet for the rest of the journey to the track. Of course, once I had cleared the shadow of the mountain and was on the highway, the rain dried up and clear patches appeared between the clouds. Could the dire weather predictions for the day have been wrong? Might we actually get some dry track after all?

It was not to be.

I arrived at the track warm and dry, completed documentation, and set about chatting to my fellow drivers about their expectations for the day. Everyone was fully aware of the predicted cold front that was destined to make track-fall by around 11am. This neatly coincided with our first race. However, at this point things were looking fine. The clouds were high and thin and the sun even made an appearance or two. We rolled out to qualify and I managed to grab third slot on the grid in Class D. I was a little perturbed when the engine cut out briefly as I opened things up on the back straight for the first time. It seemed as though my over-boosting problem was making a unwelcome return as I noticed the boost spike to 0.7bar briefly. 

A couple more squirts of the throttle seemed to sort things out and I figured the waste-gate had maybe just been a little rusted, what with the rather high levels of airborne moisture we had been experiencing of late. But, more about that later.

No sooner had we parked up in our pits when the pitter patter of rain drops rang out  all around us. The predicted weather front seemed to be making it's scheduled appearance after all. The pitter patter quickly turned into a thunderous roar as the rain came down in biblical quantities. People scattered in all directions seeking shelter. The day was taking a decided turn downhill, or downstream as it would seem.

And then suddenly, the whole paddock was empty.

The organisers valiantly tried to keep things going, but the torrential rain was creating vast rivers and ponds of standing water on the track. Of course, were we professional race car drivers, this would have just been par for the course, but most of us do this for fun and I was not relishing pitting the combination of my mediocre skill, 500Nm of torque and a pair of elderly semi-slick tyres against the rampant surf out on the track.

A couple of classes went out to race, with the predicable results. The Fine Cars race was red flagged when two cars came together on the main straight and ploughed into the pit wall. The bikes even had a go, with a good couple of riders ending up lying about in the muddy runoff areas around the track.

I had just donned my plastic water proofs and cattle prodded my mind into the start gate, when the announcement was made to cancel our race. Apparently, with a large percentage of our class being open topped, it was decided that visibility for these drivers would be a serious problem. The Porsche drivers were similarly concerned since they were expecting their cars to fog up within half a lap. Not ideal when you are trying to control a rear engined german missile, while skating over lakes of water.

I was both relieved and, strangely, annoyed at the same time. I guess I was actually keen to see how I would be able to manage in such atrocious conditions. But then, while we had raced in the wet before, it had been nothing like this, so considering I was sponsoring all repairs to my car, it was probably a good thing the race was cancelled.

It was now almost lunch time and rain was still coming down in the proverbial buckets. I swear I saw an old chap with a long beard, wondering around collecting pairs of animals a little while back! The Volkswagen GTI guys when out for their race and most put up a good show, but in reality, with lap times in the 1:50's, it was really a case of keeping the cars on the track and away from the others.

The Fine Cars regatta gets under way

Eventually, after one of the V8 Master cars almost rolled after spinning off in Turn 5, the rest of the day was cancelled and we all started packing up. The weather did choose that exact time to start clearing, but we were later to hear that the real reason the day was cancelled was more to do with the damage to the runoff areas, than the water on the track. Apparently a number of corners had had substantial ditches washed into their runoffs, creating the real possibility of a car rolling. Other areas were almost knee deep in standing water. I shudder to think of being trapped in a rolled car in that much water. All told, the right decision was made and I tiptoed home.

And then, in other breaking news.

I spent the following weekend dismantling my waste-gate again, only to find the shaft once again packed with carbon deposits. This device was fast becoming a waste-my-time-gate. After some Googling, it was suggested that high temperature copper slip should be applied to the shaft to prevent the build up. It seems to have something to do with a combination of bad fuel, low boost and me not using the car all that often. Time will tell if the copper slip actually works or simply gums the waste-gate up completely. I'm on the fence with this one at the moment.

Waste-gate carbon build up. The source of the over-boosting issue

Of course, once the waste-of-a-gate was back in the car, a test drive was called for, so on a clear Saturday afternoon we set out to see if boost would be stable.

This all went surprisingly well, until about a kilometre from home. You know how you get a little more reckless the closer you get to home, figuring that if anything went wrong, you would not have that far to walk and all that? Well, that's sort of how I was feeling as I pulled off from a stop street and floored the throttle in second gear, a quick snap change into third was met by an almighty bang from the rear, followed by a loud clattering noise and no more forward urge. We coasted into a side street and called for backup.

It was of course a broken half shaft, and was bound to happen. I had almost been waiting for it. My current items are made from BMW 540 shafts, and while they are strong, they have been lengthened. They have also endured two and a half seasons of hard racing, mistimed downshifts and, more recently, a huge increase in torque.

Operating parameters somewhat exceeded.

So, this week the car heads back to Harper Headquarters for some further development. It's also going to be fitted with the new headlight units to replace the ungainly frog eye versions. These were fitted temporarily when the new larger wheels took up all the space, usually set aside for the original headlight system.

Like I have said before, when you start making changes to an already working car, it's quite hard to predict the knock-on effect. But that is exactly why my car is called the prototype Type 6, because it's where all the development gets done. 

And I quite like that.

Cracking disks and cracking times

Race cars can be as simple or complex as you make them. 

Generally the way things work is that you start off with a nice small, simple car and a firm intention of keeping things that way. 

Where it all started. Simplicity personified.

However, within a handful of races, the red mist descends on the brain and the urge to go faster begins its insidious corruption of your most determined plans for simplicity.

Drivers will know it well, but for the uninitiated, "Red Mist" is a term used to describe what happens when a driver (usually a race car driver) looses all sense of reason and "MUST WIN AT ALL COST". This is usually associated with an on-track event, like being overtaken by a competitor, but can relate to the degree of self convincing that happens when unjustifiable sums of money need to be spent for dubious return on a race car. 

Personally, I managed to hold out for almost half a season before I started to fiddle with my perfectly functional Lotus 7. By the end of my first season of racing I had already justified building a bigger, faster car, with the firm intention of that being the end of the story. I reasoned, quite logically, that once I had a good strong platform to work off, I could focus on improving my skill rather than my equipment.

That lasted a whole season, which, looking back, was not a bad achievement actually. 

What followed, I firmly blame my fellow racers for. 

You see, I had managed to knock a whole 3 seconds off my Lotus 7 laps times with my new car. However, everyone else seemingly suffers from the same affliction and, by the end of the season, my 200kw V8 powered rocket ship was one of the slowest cars in the field, and, for once, this did not have all that much to do with my rather mediocre skill. Even in skilled hands, my car was barely tickling the middle of Class D. Success during my second season came more from the misfortune of my fellow racers, rather then me beating their pants off.

Thus, the following season saw work start on making the Type 6 a little more ferocious. This process involved a number of upgrades on the car, all culminating in the fitting of a big fat turbo at the end of last year. 

Hair dryer attached.

This is where the complexity thing comes in. Once you start changing things on an already built car, the knock on effect is hard to quantify up front. Seemingly small issues tend to have gloriously profound effects later on down the line.

Test driving the car on the road seemed to indicate that we had got everything right, and the 2014 season should be a "good one". The emergence of smoke from the exhaust a few weeks after the install was a cause for some concern, but race day was looming and we decided to adopt a typically "racing driver" strategy of "lets race and see what breaks".

The first race of the season started well with me clocking a sub 1:24 time on the third lap of the race. This was the fastest I had ever gone, so I could be forgiven for being a little bullish.

However, things rapidly turned sour as the car started cutting out under full throttle. I finished the race and, suspecting a low fuel level, topped up the tank for race two. The addition of the turbo has severely dented the fuel economy of the Type 6!

Needless to say, this was not the problem, and I pull off after the second lap, sneaking home quietly to avoid ridicule.

The following weeks involved a number of fault finding sessions, culminating in the replacement of all the fuel lines and the high pressure fuel pump, none of which solved the problem. 

New AeroQuip all around and a beefy Bosch "044" pump

Eventually a trip to Herman and the dyno revealed a waste gate that was stuck partially open. The earlier smoking issue, which had been due to a incorrectly routed turbo oil drain pipe, had caused a carbon build up on the waste gate plunger shaft. Once the car was used in real anger for the first time, this build up burnt hard and caused the plunger to seize solid. 

The cutting out was the ECU desperately trying to save the engine from becoming a shrapnel generator behind me. On the up side, we now know the engine can handle 0.7 bar of boost for short periods.

Dyno-side waste gate repairs

Some spanners, sand paper and a couple of hours later the waste gate was, well, wasting as it should again. Herman did a few dyno runs just to ensure all was well, and the figures were stable at 260kw and 500Nm. 

Just in time for the second race day of the season.

April is not normally known for it's heat down here in Cape Town. That honour usually falls to February. But, this year, clearly Feb was on leave and April was standing in. I knew it was hot when I keyed the ignition of my car for the second race, after it had been standing for around 4 hours, and the temperature gauge still read over 60 degrees. Track temperatures where measured at deep into the 40's, and the day was a real test of man and machine. Many did not survive and I was glad to have an open top car to cool me down during the action. I noted many a Porsche driver emerge red faced and slightly wobbly from their rear engined ovens after the racing.

The heat did allow for some seriously sticky tyres and I was revelling in, what was essentially, a new car to me. Race one was extra special as I managed to out drag Cyril's GT3RS coming out of turn 5, clocking a 23.3 lap time in the process. The fastest time ever recorded by the Type 6. I took second place overall in Class D for the day and was happy that the car had performed flawlessly the whole day, despite the searing heat and close racing.

Well, almost, that was. On the way home that evening I detected a bit of a ticking noise coming from the front brakes. This seemed to be coupled to a pulsing feeling from the pedal. 

All had not survived the day, it seemed.

Closer inspection yielded, not one, not two, but three of the four disks had cracked from edge to centre. We would later discover that the fourth would also have cracked had the calliper for that wheel not have been sticking. 

This crack is not an attempt to increase braking efficiency!

To be honest, we had sort of created the problem for ourselves. 

Soon after the car had been finished, it showed a rather alarming propensity to warp the off-the-shelf 250mm Toyota RunX disks we were using. After some consultation with "those who know" it was recommended that we get slotted disks. The logic was that we were overheating the disks by using race spec pads. The gas build-up under the pad was not being allowed to escape and this was causing the "high spots" on the disks often mistaken for physical warping. Rather than spending copious amounts of cash on custom race spec disks, we opted to have the off-the-shelf items slotted. This was duly done and the consumption of disks immediately ceased.

Fast forward to the present, where we had replaced the 250mm disks with 282mm items. Thinking to avert the same issues as before, we dutifully slotted these disks as well. Of course, the forces at play now were all a little bigger. I was arriving at the corners much faster and braking effort was much increased with the extra downforce. Add this to fact that we slotted our disks right to the edge, and the result was somewhat predictable. All the disks had cracked down one of our slots.

This proved to be the perfect time to finish off the brake upgrade we had started the year before. The long term idea was to use standard 305mm disks off the Toyota Rav4 SUV, but at the time we could not get the correct calliper brackets made up in time, so instead we using some existing brackets and cut the 305 disks down to 282.

Craig designed some nice brackets which were made up by a local CNC shop and, hey presto, we had 305mm disks all round. 

Race car porn, right there!

We again slotted the disks, but this time we stopped short of the edge of the disk. Hopefully this will maintain the structural integrity of the disk under load. Sometimes I think I should attach my GoPro to a chassis member and film the underneath workings of the car. One can't help feeling this might well be more exciting to watch than the racing sometimes.

Anyway, at the recent race day the new brakes worked exceptionally well, although I suspect some extra cooling ducts might be next on the never ending list of "stuff to do".

Fetching blue tint to the new brake disks

The racing for the day was once again fast and furious, with the added excitement of the inclement weather. Clearly Feb was back from leave and April could once again revert to it's usual character. I arrived good and early having neatly dodged a rather determined rain cloud, only to have it catch up with me during qualifying. This created a situation more suited to creatures with gills, than cars with slightly ageing semi slick tyres.

Storm clouds gathering...

After attempting to drift (like a race driver, not a boat captain) through turn 2, and failing dismally, I decided it was safer to just start at the back of Class D. 


Thankfully the weather cleared up for our races and both were action packed events. Unfortunately, in Class D, competition is fierce, and starting at the back will mean finishing at the back if everyone brings their A game. 

It was an A game day for all except me and I finished the day fourth over all. Not exactly stellar, but a great day of good, clean racing none the less.

Class D is now looking like "the" place to be. The class times have been realigned due to the ever decreasing lap times, putting around 9 cars in D, with just over a second separating them. This provides for some good, close racing.

All told, the season is shaping up better than it started. Now, if I can just keep the effects of the red mist at bay.

With a huff and a puff

Bigger brakes? Check!

Stronger clutch? Check!

Wider wheels? Check!

More downforce? Check!

It was time. The collection of parts that had being slowly building over the last year and a bit were about to meet their destiny. It was finally time to turbo charge the Harper Type 6 V8.

The 4.0 litre, naturally aspirated, Lexus V8 that is fitted to my car is a bit of an unsung hero in the engine world. Often overlooked owing to its rather small capacity, at least when compared to brawny American muscle, this all aluminium engine boasts some fairly advanced tech for its time. 

Designed in the late 80's by Yamaha for the Lexus LS 400 saloon, it quickly made its way into a number of Toyota vehicles, running in production until 2000. Designated as the 1UZ-FE, it featured an all aluminium over square block, 6 bolt main bearings and belt driven quad cams acting on four valves per cylinder - all combining to produce 195kw and 360Nm out of the box. 

Quite impressive for the day!

The engine quickly built a reputation for being strong and reliable, gaining it a sturdy engine transplant following. It was not only fitted to virtually every type of four wheeled vehicle, but also ended up in home built aeroplanes and boats over the course of its life. Despite the enthusiastic fan club, even by the mid 2000's, aftermarket go-faster goodies were scarce and expensive. The desire for more power was ever present and it was not long before turbos were being bolted onto the little V8. The pre-94 version of the engine had slightly thicker con rods, but more importantly, a lowish compression ration of 10.1:1. Not exactly ideal for slapping on a turbo, but tuners realised that if the boost was kept below 0.8 bar, the engine was still reliable and could produce over 300kw. This was a nice option, since you started off with a 200kw motor and then just increased the peak power and torque. Turbo lag was not an issue with this setup.

Of course, there were those that went a bit crazy and built 1000hp versions of the engine, but at vast cost and effort. Generally, if you wanted huge power you were best off starting with a big block American engine, but if you wanted cheap power, you slapped a turbo on a 1UZ. Dropping the compression ratio with aftermarket pistons allowed boosting of over 1  bar and power number in the 400's. Again, a nice option, but the real strength of the 1UZ was, well, its strength. Not having to open the engine up before adding the turbo was a huge gain, both in terms of cost and time.

Thus, our plan was to bolt a rather large turbo directly onto my two season old race engine without even taking the engine out of the car. Further, the car still had to run on pump fuel, a tall ask for a high compression engine being force fed buckets of air.

The car as duly dispatched to the Harper head quarters where work began, as always, in ernest.

The design of the Type 6 lends itself rather well to the addition of a turbo, since there is a large open space behind the engine and above the gearbox that happily coincides with the exhaust pipes. 

A space in need of filling

Craig set about designing and fabbing up all the required bits. A manifold had to be made, oil feeds routed, intercooler installed, dump valve and waste-gate plumbed in and numerous other small fiddly bits all needed doing. 

New two into one exhaust manifold..

..and fitted in place waiting for the turbo and waste-gate

Turbo and waste-gate fitted

Of course, the addition of a turbo meant I would be losing my twin tail pipes. I was a little unhappy about this as they gave the rear of the car some serious cred. However, there was no way to route the exhaust back up and still split it into two for the effect. In the end we decided on a single large 76mm tail pipe exiting low out the back of the car. I think it actually looks a little meaner now.

Single large exhaust pipe

While all the activity was going on, and body panels were removed, we decided to also fit an oil cooler. I had managed to get away with not having one for two seasons so far, but oil temps were a little on the high side and the addition of the oil cooled turbo was likely going to push things over the edge. A nifty all in one kit was ordered and installed in one of the side pods.

Oil cooler sharing space with the fuel pumps

Once the intercooler had been added, the space that was previously there, ceased to exist.

Intercooler, dump valve and "traffic fan" installed

Space? What space?

No really, there is no space left

Once all the mechanicals had been completed, a small modification was required to the engine cover to allow cool air into the intercooler. This was easily achieved by chopping a big hole in the existing cover and building on a new scoop. 

Hole made (no, he did not cut it out with the scissors!)

Scoop taking shape

The final finished item turned out rather well I think, adding just a little more menace to an already menacing car.

The new scoop

Subtle, but present

While Craig was busy finishing off the look-good bits, I decided to go shopping. I was a little concerned about how I was going to monitor the engine. The digital dash I have installed would easily be able to give me the boost pressure as well as all the usual temperature readings, but what I needed was a way of checking the state of the engine when it was working hard.

(DANGER - Technical stuff coming up)

Plonking a fat turbo onto a relatively high compression engine can produce two undesirable results. 

The first, and possibly most dangerous, is pre-ignition. Also known as knocking or pinking (although not technically the same thing), pre-ignition is when the fuel in the cylinder spontaneously ignites before the piston has reached the top of its stroke. 

Normally, the piston, on its way up the cylinder, compresses the air that was drawn in on the previous down stroke. As the piston nears the top of its stroke, a carefully choreographed dance takes place between the piston passing the top of its stroke, the injector injecting just the right amount of fuel into the ever decreasing space and the spark plug firing to ignite the air/fuel mix bomb. The engine ECU coordinates all this according to the "map" that has been written by the tuner. Fire the spark plug too soon and you will explode the bomb before the piston has past the top of its stroke. It then hits the expanding flame front instead of being pushed down the cylinder by it. This is when you hear the "knock" or "ping". 

This chattering noise is bad for an engine and should never be heard in a modern electronically controlled, fuel injected car if it is well tuned However, most normally aspirated engines can survive some "knocking" without ill effect. 

The problem with adding a turbo to the mix, is that now, one is forcing more air into the engine. When you squeeze air, it gets hot. Eventually you will get to the point when the air being forced into the engine (the boost), assisted by the compression effect of the piston, reaches the ignition temperature of the fuel. Thus, as soon as the injector squirts the fuel into the cylinder, it explodes. With a turbo car on high boost, this can happen way before the piston reaches the top of its stroke. This is pre-ignition, and it usually ends in tears as bits of piston end up in the sump.

Pre-ignition can be averted by having a good tuner and running an additive in the fuel. The tuner needs to make sure the engine timing and boost pressure is within a suitable range to ensure no knocking happens, while the additive slows down the burn rate of the fuel, making it a bit more predictive. The idea is not to have a massive, short lived explosion just as the piston rolls over top dead centre, but rather a controlled burn as it makes its way back down the cylinder. The higher the octane rating of a fuel, the slower the burn. By slow, of course we are talking relative here, milliseconds and stuff.

The second issue that presents itself is a little more insidious. This is the problem of running "lean". Running lean essentially means that there is not enough fuel being injected into the piston at each firing stroke. While this may seem like a good thing from a fuel economy point of view, it can be terminal for an engine. What happens normally is that the squirt of fuel from the injector actually serves to slightly cool the piston and valves down each firing stroke. When you run lean, you lose this slight cooling effect. Under normal street driving conditions, one would probably never know a car was running lean. However, put a car on a track and add a turbo to the mix, and quite quickly one can turn nice aluminium pistons into blobs of molten goo. This can happen in the space of a few laps and could even be caused by something as simple as a failing fuel pump. You, as the driver, will have no warning until clouds of smoke appear from the rear of your car.

(Note for anoraks out there. This is a vast simplification of the problem, and there are all manner of discussions about  stoichiometry, "insulation boundaries" and subsequent increased heat transfers to piston crown etc that actually cause the "melting" issue, but let us not get caught up in all that here)

Anyway, back to the shopping. I was going to rely on Herman from Mace to ensure I did not have any knocking,  but I turned to technology to ensure I did not melt any pistons. Drivers of modified diesel engines use gauges called EGT's to keep an eye on this whole issue. The EGT or Exhaust Gas Temperature gauges measure, well, just that. Increase in EGT means pending doom, so slow down.

Us petrol heads have a much better way of doing this. We measure AFR or Air to Fuel ratio. If there is too much air in the AFR, you are running lean, simple as that. I bought a neat little kit that included everything one needs to measure AFR, with the added bonus of it being able to send the reading directly to my on board logger too.

New anti-melt toy

Large LED readout with colour coded bars around the edge

The AFR gauge is very simple in that it actually consists of a wide band lambda sensor that goes into the exhaust pipe anywhere after the turbo, and the gauge itself. The gauge measures the voltage from the lambda and translates this to an AFR. A very simple and completely stand alone system, and an easy way for me to make sure no in-engine melting takes place.

Once all this was fitted and the car was ready, we needed to get it mapped. We started out by simply recalibrating the existing map for the extra air and then carefully drove it down to Mace for a tender loving thrash on the dyno.

Herman started off with his knock sensor attached to the engine to determine how much boost we could run with the standard fuel. The result was a rather low 0.3 bar. We added some NF Black octane booster and things looked much better at 0.45 bar.

After much fiddling and tuning, Herman eventually called it a day at 261kw and 502Nm of torque under only 0.45 bar boost. The turbo itself is good from over 2 bar, but we would need to convert to avgas or ethanol if more boost was desired with our current compression ratio. I was happy with the numbers. Some 60 extra kilowatts and over 100 Nm of torque was going to be fun and games in a car already endowed with a tail happy streak. There is still plenty of room to expand as well, so we are starting off conservatively. Reliability is still very important.

Now, while you may be thinking.."260kw? I can get that from a tuned egg box", bear in mind the Type 6 only weighs 900kg giving it a power to weight ratio of 395HP/Ton. Still not convinced, take a look at where this places the humble Type 6 in the BHP/Ton standings.

Playing with the big boys

Video: Herman, working his magic

Nice smooth curves, always a good thing

It was now time to hit the track to see if the whole was greater than the sum of the parts.

Typically, Cape Town was raining on the day of the track booking, but thankfully it cleared up just in time for me put in around 30 laps or so.

So, what's the verdict you ask. Well, the car was always pretty fast. With lots of torque low down, it would come out of corners like a scalded cat and I would easily reach 215km/h down our, fairly short,  back straight. The wing and larger wheels have eroded some of this urge. The wing by adding drag and stealing 10km/h from my top end, while the larger wheels by changing the gearing and putting me lower down the torque band on fourth gear corners. 

The turbo has fixed all that and more. On my initial runs, and I was taking it easy given that everything was still shiny and new, I managed 220km/h top speed. Lap times were nothing to shout home about, but then it was wet and I was being a little cautious. 

It's a curious effect though. The turbo has added a whole lot more power and torque with no perceptible lag. Booting the throttle launches the car toward the horizon at an astonishing pace, which just seems to keep going until your either run out of nerve or road.

Driving the car on public roads now requires quite a bit of concentration. You can't just be tootling along in third gear behind granny and then stomp on the throttle when a gap appears. This can elicit  a lot of scrabbling from the rear and some unwanted sideways action. 

Grannies generally disapprove of big black noisy cars coming past them sideways.

All told, the conversion has been a success so far. Time will tell if we have messed with the excellent reliability of the car, and I'm sure we will be presented with some teething problems as the season begins. The truth will, of course, be in the first full blown race day where I hope lap times will show a significant improvement. 

But for now, I just love stomping on the throttle to feel the massive urge pushing me into the seat followed by the raucous hiss of the dump valve just behind my ear as I come off the load pedal.

It really is quite addictive. I think I might be starting to like turbos again.