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.
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.
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.
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.
Once the intercooler had been added, the space that was previously there, ceased to exist.
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.
The final finished item turned out rather well I think, adding just a little more menace to an already menacing car.
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.
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.
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.
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 |
 |
| Single large exhaust pipe |
 |
| Oil cooler sharing space with the fuel pumps |
 |
| Intercooler, dump valve and "traffic fan" installed |
 |
| Space? What space? |
 |
| No really, there is no space left |
 |
| Hole made (no, he did not cut it out with the scissors!) |
 |
| Scoop taking shape |
 |
| The new scoop |
 |
| Subtle, but present |
(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 |
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 |
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.
