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Turbo Talk with Terry

We interview one of Australia's most experienced turbo gurus - Terry Wilson of AVO...

Interview by Michael Knowling

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AVO (Advanced Vehicle Operations) is one of the longest established turbo tuning specialists in Australia. They've tinkered with everything from turbo EH Holdens to R34 GT-R Skylines and adapting turbo kits to suit the most unlikely vehicles. Their workshop today contains some ultra-desirable machinery, in addition to a fabrication shop, engine dyno and four-wheel-drive chassis dyno. In this interview we get the oil from Terry Wilson, founder and head-honcho of this Melbourne based go-fast 'shop...

The Early Days

"I started out working on cars with my old man and my brother back in the early '60s.

"We started motor racing in about 1964, and we got into racing turbos in the early '70s. We began with a lot with HR Holdens and that sort of thing, and then we moved on to turbocharging an EH Holden. That thing had 500hp at the flywheel un-intercooled - we had heaps of water sprays on it. We've actually had an engine dyno - an old water brake - for thirty years. I've still got it here [in addition to a current model engine dyno]. We also used to do a lot of general engine reconditioning - like crankshaft grinding - and engine building before we got stuck into things like turbo kits.

"After that I was with the old AIT turbocharging mob for a while in the '80s - before they went broke. I was the head of their prototype department and went all over the world fitting kits and doing development. Then I went along to Harry [Nakajima] at Nakajima Trading and started AVO with him - I put a proposal in, he put up the money and we started AVO there and then. That would've been about 1992. We started at Harry's Nakajima Cars at Springvale and we've been here - at Cheltenham - for about four years, I suppose.

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"I developed the early XF Falcon turbo and twin turbo kits back in the late '80s. We had a twin-turbo four-wheel-drive Falcon, which I took to England for about four months and - the day before we were ready for a press release - I crashed the thing. That car was making about 380 horsepower and about 540ft/lb of torque on the engine dyno. 540ft/lb is pretty good even today - there aren't many cars on the road with that torque, that's a shitload. Yeah, that was a pretty state-of-the-art thing at the time - we had a ZF 5-speed in it and a trick four-wheel-drive set-up. The only problem was the EA was coming out the next year and that made it difficult. I did some work on the early stages of the AIT EA Falcon turbo kit and then I left.

"The first cars we worked on when we started AVO were really all Japanese. Harry used to import cars like Mazda RX-7s and Nissan Skylines and that. Celicas we used to do a lot and, really, anything that wasn't turbocharged we'd put one on."

Turbo Cars Now

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"It's harder modifying a car now - the electronics have now made it extremely hard. Like that IS200 ["New Car Test - Lexus IS200 Limited Edition"] you can up the boost and it'll ping a little bit, but drive it a couple of times and it goes away - it learns. On that car we've used a crossover injection system - it runs on the standard ECU and then it crosses over to another one.

"The cars we do here at AVO have changed as well - we mainly do factory late-model turbocars. But, you know, if the Americans or the Arabs want a turbo kit, we'll develop one for them.

"You can get good gains without having to do much on the late model turbo stuff. The exhaust should be your starting point. I think that going 3-inch is mainly just for fashion, because a 2½-inch system with good flowing mufflers is good for 300 horsepower without any troubles - without too much back-pressure. Everybody seems to love 3-inch, though, so I guess we have to stick with the trends...

"The next thing I'd say is to up the boost tiny bit - through the standard intercooler. A computer is also important because as soon as you improve these things the car runs richer and you've gotta get some of the fuel out of it. I reckon the air intake should be done about the same time you do the intercooler.

"Depending on boost pressure, you can take - say - a Subaru WRX from about 100kW at the wheels to around 160-180kW with these mods. After about 180 - 190 they're out of injector [flow capability]. And, look, you can probably get up to 170 - 180kW with the standard turbo on the earlier WRXs, but the ones after that are pretty small. Bolt on one of one of our 400hp turbos and they make power easy.

"The point where you need to change to a bigger turbo is different for different vehicles. We find the later WRX stuff is getting pretty stuffed at about 150 on our dyno. And, on a Skyline GT-R, I wouldn't go above 15 psi with their ceramic standard turbos. When they flake off they can go back through the engine. When this happens, people tend to back their foot off and that'll suck the thing into the engine - that makes a hell of a mess! We've seen about three cases of those.

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"Aside from modifying the factory stuff, though, we've developed a few bolt-on turbo kits. We've got them for Mazda MX-5s (Miatas), about all the Hondas, Suzuki Swift GTis, the Nissan Patrol 4.8 and 4.5, the big Toyota 6 cylinder and V8, Lexus IS200 and more. We've also got a kit for the late Toyota RAV4 - that also fits Celicas.

"On some of those kits we run an extra injector, but on others we don't. Some engines have got big enough injectors to play with, but anything over about our Stage 1 we go for an extra injector and a computer. Most of the late-model cars you get about 2 psi of boost into them and you're out of injector - Hondas are like that, they're so close to the mark.

"On the early MX-5s I put in pyrometers in each exhaust port and I moved the extra injector around until I got it right. And it is - it's beautiful. I think up to 7 or 8 psi of boost an extra injector is good, but much over that I wouldn't run them."


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"One thing I've noticed is there's a lot of horseshit surrounding intercoolers these days. Personally, I reckon bar and plates are heaps better than a tube and fin. An intercooler is only a heat sink - the more aluminium you've got per side the better.

"Here is a tube and find core which is called 3½-inch because it suits 3½-inch end-tanks - but actually it's not. Have a look and you'll notice the end plate sticks out from both the front and rear sides of the core. The core thickness isn't anywhere near as thick as the end tank design. Also, the entry on a tube and fin is bad - if you were porting and polishing a head you wouldn't want anything like those big daggy tips sticking out.

"There's all this crap about tube and fin cores flow better - that's not the case, because I can alter the number of internal fins per inch. I could put absolutely nothing, no fins, in there if I wanted - it'd flow real good but it wouldn't cool very well.

"There are also different types of tube and fin designs - there's a straight fin and an offset fin. Offset fins cool better than a straight fin, but they don't flow as well. There's a straight fin core I put in RX-7 SP twin-turbos, and there's a twinned version that I run on Porsches that have offset fins. The single RX-7 core needs to flow a lot more air than either of the ones used on the Porsche, but ultimately it doesn't have as much cooling capacity.

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"I've got a computer program that lets me pick the intercooler by taking into account the flow rate of the turbocharger and the power output. Boost hasn't really got much to do with intercooler pressure drop. People say they've got half a psi pressure drop at 15 psi - that's wank. It's the airflow that matters - it's pounds per hour. You see, I can put 20 psi through a core and I can put 150 psi through it and it won't make any difference - it's the flow volume that's critical. We quote our bar and plate replacement top-mount for early WRX with a 1 psi loss at 360 horsepower.

"We also produce some water-to-air cores, which we generally use when we can't fit a large enough air-to-air. As far as I'm concerned air-to-air is better because it's completely maintenance-free. With a water-to-air, if the pump stuffs up when you're half way through a race your engine detonates and everything's gone. We do use water-to-air on our Rav 4 kit - the pump we use is a Flowmaster, which flows 18 gallons a minute. You've got to get water through them quick and you've got to have a huge radiator in the front of them otherwise it's just a waste of time.

"I think water sprays help air-to-air intercoolers a little bit, but it doesn't work if you just keep flowing water onto the core - you've got to have a flow of both air and water. You really need the airflow for the spray to work - so using the spray standing at a set of traffic lights isn't going to make much difference. You only need to put a little bit of water on your finger and put it out the window as you drive along - you feel it's the coldest when you're moving along. It's the evaporation. You don't need to hose gallons of water on the thing.

"Also, what we do in our water spray kits is run a timer - they squirt and turn off, squirt and turn off. Plus, that way, they don't use as much water - which can save weight."


"Blow-off valves, I find, are also a bit misunderstood.

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"To be honest they've really only got one principle - to stop the pressure spike that can build up before the compressor. Forget about all the other scientific horseshit. You've got to get rid of that spike; if you data-log the intake, you'll see when you back off you get a boost spike. We've seen that testing on the chassis dyno.

"You've really got to put the right size blow-off valve on to suit the size of your turbocharger. There's no use putting a tiny bastard on when you've got a whopping great turbo that whacks through a lot of air. The valve has to open fast and wide enough to dump the air. I don't think there'd be any difference in performance with a different blow-off valve. A lot of it is wank - if you ate a big dinner that'd make the difference in performance.

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"One thing people often don't think about is intercooler pipe diameter. We made an intercooler for an engine guru with a Lancer GSR. He wanted 2-inch pipes because he said the throttle response would be better - we told him it'd be worse but, anyway, we made a set of pipes in both 2-inch and 2½-inch. The 2½ ended up making about 18kW more at the wheels and its throttle response was miles better. But, look, this guy was running 15 psi boost - if he had have been running 5 or 6 psi, 2-inch pipes probably wouldn't have been a problem. You've gotta remember the turbocharger can easily flow more than the pipes - if the pipes are too small the induction air is just going to bank up."

Sacred Cows

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"The gearboxes in the Subarus are rubbish - they're terrible. The gears are simply too small. I went to Brunei a while back and put some 450hp turbos on all these Subarus. I was driving along with one guy and told him to flatten in it fourth gear at about 2000 rpm - he did, and as soon as it got to about 4500 rpm it just ripped the teeth all off. What can you do?

"The best solution is a straight-cut 'box, but it isn't really a good solution for road use. I've got customers with them and, to be honest, I wouldn't want to drive them everyday. I think somebody should be able to make a tougher synchro 'box that's nice to drive.

"It might help if the clutch slips a bit, maybe. I try to steer clear of the paddles [ie paddle clutches] until they're totally necessary - most people just want to drive their car on the road. If you've got a real idiot I guess you've got to put a paddle in it. The gearbox oil is a key thing in Subarus too - it's got to be changed regularly and with a good quality oil.

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"My ideal performance streetcar would be a toss between an Evo Lancer and a GT-R Skyline. They're both a lot stronger than the Subaru - you don't have to keep working on the thing. We get a few customers with GT-Rs making 270 - 280kW at the wheels and they don't have any problems at all. I've also got a coupe of Evos making 250 at the wheels with no gearbox troubles. The Evos are a lot more drivable than a Subaru too, because they've got a small bore and a huge stroke - the Subaru is the other way.

"My future prediction is that if you don't modify your car in a legal way you won't do it - simple as that. Even now you need to have in the back of mind that one day you'll get pulled over. The EPA here is clamping right down, and I found it's the same all over the world - which I don't think is a bad thing. But it means the days of huge cams and things like that are limited. I don't reckon it'll be long before all racecars here are forced to use cat converters, like a lot of the European stuff already.

"At the end of the day, the more cars that can drive around smog-free the better. Really, that's got to be a good thing."


AVO (Advanced Vehicle Operations)
+61 3 9584 4499

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