How long have you been in the turbocharging industry and what sort of vehicles have you owned?
I've been in the industry close to 30 years now. I started with NormalAir Garrett in Melbourne when they were doing their dealer option turbo Commodore and the start of the Mitsubishi Sigma turbo. That's going back a while - back in the days of carburettors and things like that. In those days we had no idea that things like MoTeC, Autronic and Microtech - and all of the other management systems - would go on to be readily accessible and relatively cheap. I must say, if we had today's technology back then, it would've been a lot of fun!
From there I moved from NormalAir Garrett to one of our independent distributors - Dynamic Turbochargers. I was involved with them for some 12 years. I ran their Melbourne workshop, opened and ran their South Australian division and moved to their Airport West facility. From there I moved into various businesses of my own - some of them involved in turbocharging - and about 4 years ago I was approached by Garrett to come back and manage the turbocharger division. That's how I arrived back here.
My own cars? I ran a Mazda RX-7 many years ago, which was built in Adelaide. We actually had a Nissan race team type engine mid-mounted in it, and Mick Montorosso - who's fairly well known these days - at that stage had a BDG-powered Escort. We were archenemies. If I bolted on a new set of tyres I'd win and if he bolted on a new set he'd win. We used to have some great races.
I've also had a Sprite with a turbocharged Ford engine in it, a turbo 2-litre Capri, Bluebird turbos and all sorts of weird and wonderful things. These days I think I'm getting too old for that sort of thing though - I've got a MG TC, which isn't turbocharged. And it never will be!
Tell us your background in motorsports.
Recently I've been fairly heavily involved in things like sports sedans - development of the engine side of things.
My own personal interest was with Nissan type race engines. I did all the preparation with Seton on most of the Group C Nissan Bluebirds. That was great, because it gave me the opportunity to learn hands-on with the help of Nissan and the Nissan race team. And - even back in Marsden's and Seton's days - we had the availability of engines and dynamometers that most of us could never dream of having access to.
They used to contact me at that stage - when I was living in Adelaide - and he'd simply say,"I've got a couple of engines ready, bring over a box of turbochargers and let's try some things." So I'd come over for the weekend and we might wear one or two engines out over the weekend - but we'd learn a huge amount. We'd machine a little bit off the turbo here or add a little bit there and we'd work out exactly what it did.
In your experiences, what are some of the best-matched factory turbo installations?
Generally speaking - because of emissions and design rules - you won't find too many turbo cars these days that aren't well matched. We might be comparing a Saab on one hand with a Porsche on the other hand - they're designed for different markets.
To be truthful - personally - I've got a very soft spot for the Subarus. From a relatively small engine, the performance and driveability is quite remarkable - but, again, as we touched on earlier, the electronic controls and things available these days are quite mind-boggling.
All the OEs [original equipment manufacturers] are doing an amazing job - the performance and reliability speaks for itself. It's nothing to get a 10-year old Nissan Skyline GT-R that's still in reasonably good mechanical condition. We see Subarus that have been hard-driven and still run perfectly, then there are cars like Toyota Supras and VL Commodores - they came out in 1986!
I've only been involved in one OE matching on a vehicle - it's almost inconceivable to imagine the number of areas that they look at. They look at the total vehicle package, everything that exists from drivetrain to driveability, emissions, fuel economy, underbonnet temperature, light-off cat converters and life of all components - it goes on. One OE overseas manufacturer - on one test run - consumed over $20,000 worth of fuel alone in this process.
Some Nissan turbochargers use ceramic turbine wheels - what are their advantages and limitations?
Ceramic turbines are wonderful. We've used them in Caterpillar engines and Detroit engines and they're very heat resistant materials, they're light and very responsive - but they don't like foreign objects. You've only got to have the engine tuned once on the dynamometer a little bit lean - it'll drop a bit of spark plug electrode and it's a bit like a puff of talcum powder out the exhaust. And then you don't have a turbine wheel any more. Even if you're pulling one of these turbos apart and you knock the head of the wheel, they will actually break.
The other thing that happens if they are drastically over-sped - and I mean fairly drastically - the head joint will let go at the back of the turbine wheel. It's not necessarily the turbine wheel that goes, but the assembly to the shaft. The OE has designed it to suit their application. They don't want you to go from 9 psi to 15 psi, because it's designed to be at maximum efficiency at 9 psi. Turn it up to 15 psi and the turbine speed has probably gone up 40 percent - the head of the wheel has never been designed to spin at those revolutions.
With some of them you can get away with lots of extra boost before you run into turbo problems - but it's model specific. We've not seen too many problems with basic modifications like an exhaust, air cleaner and a very mild boost increase. When you're chasing the horsepower that's available, though, that is when turbine wheel heads drop off - or if you're using the car for competition use. Over time - like in an endurance race - it'll get to the point where it fatigues.
Sometimes, with hand fabricated exhaust manifolds or even cast manifolds, if there's a little bit of welding dag or casting dag left in it - again - you might end up with no turbine wheel.
So they're generally very tough, very reliable items but they're not happy about impacts. I guess you could say they're an excellent fair weather sailer - when everything's perfect, they're wonderful. But they're not drastically good with foreign object damage.
Ball bearing turbos are now very popular - what are their advantages?
There are a few big plusses for us.
There is much less oil consumption inside the turbocharger - it runs only a 0.8 to 1.1mm oil feed hole, so the engine doesn't have to supply lots of oil to the turbocharger. It remains in the engine's main bearings or wherever it's required. The response from the ball bearing is also very good because of the small amount of oil and the design of the ball bearings. We get a better driveable package, generally speaking.
They're also very strong - a ball bearing turbo is about three times as strong in thrust. So if you want a fairly small engine to produce big hp in the top-end, we have the scope to mismatch the turbo - something we struggled to do before. If we had this kind of ball-bearing technology when we were building Group A race Sierra turbos for Dick Johnson, we wouldn't have had the thrust bearing failures we had. We generally would have also been able to run more boost easier and achieved better driveability - which those cars had none of.
Does the small diameter oil feed create any problems?
No, generally not. The only thing we've got to be a little bit careful of is the restrictor in the top of the turbo is quite small - we've had a few of these returned with bits of gasket and Silastic blocking them. That'll soon cause turbo failure. So, certainly, cleanliness is fairly critical.
In the old T3s the oil feed holes to the thrust bearings were still only about 1mm in diameter - similar to those in the ball bearing turbos - but you might have had two or three of those holes, not just one.
Obviously ball bearing cores have had a lot of development, what about blade profiles?
Yes we have come a long way. But unfortunately - or fortunately, whichever way you want to look at it - the old T3 and T4 that we built many years ago is still very popular and, in certain applications, is still one of the best turbochargers we can get. It's still got some wonderful design in it, but our latest GT-series ball-bearing turbochargers incorporate lightweight design and wonderful materials. Blade angles have changed, angles on the turbine wheel and compressor wheel have changed - and they're a great improvement.
Are turbo timers still essential to give your turbo a good lifespan?
With the modern water-cooled turbocharger we've certainly reduced - but not completely removed - the need for turbo timing.
The advent of turbo timers was early in the piece with cars like Nissan Pulsar ETs, which used just an air-cooled or oil-cooled turbo. Nowadays the development has been to put a full 360-degree encasement of water around the core. So, really, all you've got now is one end that gets red hot if you've been charging along quite hard, and - hopefully - the other end is nice and cool if you've been picking up cool air.
A gasoline engine at an idle isn't going to drop an enormous amount of temperature. If you let it idle for 15 minutes it'll drop, but it'll still stay hot due to the combustion of the gasoline. Some people might want to let it idle for a short length of time - but if you've just been chugging around town or locally, you only need to idle into the car park and switch it off.
The other thing we want to do is make sure the turbo is spinning slowly before you shut it down. Many times I've seen people come into a car park quite quickly, turn the key off, pull the handbrake on and the turbo is still spinning down even when the engine's stopped rotating and there's no oil pressure. This continued spinning is particularly noticeable if you're in an off-road race vehicle and you have a spin and stall the engine. You can still hear the turbo - especially if it's a ball bearing unit - spinning some minute or so later.
Many years ago an insurance company asked me a question in regards to a turbo timer. An automatic vehicle had been left with children in the car and they knocked it into Drive, and it actually hit somebody. So there are some debates about leaving a vehicle running while unattended.
What can an early switch-off cause?
Generally speaking, if it's just been running around locally, no problems at all. What can happen is the oil - especially if it's been a while between oil changes - drops down onto a red-hot shaft and, as you can imagine, it forms a carbon layer. It just bakes. So next time you go to start it up there's this lovely abrasive carbon there, which rips the daylights out of the bearings.
But it's not so much a problem these days - we've got wonderful oils available, 360 degree water cooling, wonderful fuel management systems and things that keep mixtures at the right levels - so it's not really the problem it used to be.
How important is it to use very high-grade oil?
You'd have to be guided by the oil companies on that one - I don't profess to be an absolute expert on oil.
It's probably more relevant that the oil changes aren't left too long on a high-performance vehicle. There might be a bit of blow-by past the rings when it's on full boost - we often get fuel dilution. So I guess it's a more a situation problem than the oil type.
It appears that most of the oil companies' products are great at coping with turbocharged pressures and stresses. I've seen some terrific results from most of the synthetic oils - but I've also seen some great results from testing on vehicles with straight-grade mineral oils too.
But - as I say - fuel dilution and carbon particles in the oil are the things that can kill the turbocharger.
Many modified turbo cars use an aftermarket air filter in a position that's relatively exposed to foreign material - how sensitive is a turbo to increased dust ingestion?
Extremely. With most of these smaller automotive turbochargers it's nothing to talk a turbo spinning at 150,000 revs. One dust particle will be like it hit a brick wall - so good filtering is very critical.
We don't see an enormous amount of dust erosion on everyday road cars, but we certainly do in some off-road vehicles and rally cars. You'll see the compressor wheel eaten back, and it's nothing to have almost no blades left in it.
Putting an air pod at the turbocharger compressor, you'll collect hot air from under the bonnet. The factory goes through a lot of trouble to put in little plastic ducts that pick up air where it's nice and cool. So a pod might improve the flow but you'll pick up hot air. And before anyone can say that a particular airbox won't work or that air clearer element's got restriction, you've really got to put a gauge on it. A manometer.
If the air cleaner is too small and restrictive, it may force the turbo to pull oil past its own seals. You get a fairly large vacuum at the entry to the turbo and it says, "I want more air", so it pulls it from behind its own compressor wheel and they pour oil out. We've had turbochargers come back with somebody claiming a problem and there's been nothing wrong with them - the air clearer might be too restrictive. The pre-compressor air hoses might even be closing down - we've seen that too.
On a factory turbocar with - say - just an air filter and exhaust, is an aftermarket BOV recommended?
Not necessarily - you can't really talk in general because every blow-off valve is different. But - certainly - if the valve is big enough to flow what's required then there's no need to change it at all. Of course everybody wants the noise, though - and you don't get that from a factory vehicle. A factory blow-off valve recirculates because manufacturers like them to be nice and quiet, they don't want the noise that a lot of guys in the aftermarket enjoy.
It really depends on the extent of the modifications. The OEs are very clever engineering people and they generally don't make anything bigger than it needs to be. The whole system is designed around its requirements. If you suddenly put a much larger turbo on the vehicle you may get to a point where the standard blow-off valve doesn't cope.
From a turbo point of view, a blow-off valve's a great thing. It stops that enormous pressure build up between the compressor and the engine when the throttle is shut quickly. It allows the turbo revs to continue a little bit rather than stopping on a brick wall.
In some conditions the effect of a blow-off valve is very noticeable - like hard and fast deceleration and acceleration. If you're just quietly meandering off the throttle for a while into a corner or whatever, then the turbo will have to slow down to a point and then speed up again. But if it's a sharp off/on the throttle, then the turbo can continue some of its momentum and it'll have a decided effect.
In the next instalment, we'll get Geoff talking about some nitty-gritty tech - turbo sizing, turbine wheel back-cutting, compressor surge and more!
Contact:
Honeywell-Garrett Turbochargers
+61 2 9755 3311
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