Walker’s World March 04

I was a 13-year-old schoolboy when I first did 'automobile engineering' as a subject. Here at last was a subject that captured my imagination. I knew right after that first lesson that this was the trade for me. My teacher was 'Knobby' Clark and it seemed to me that he knew everything about engines. One of the other lads had a bigger brother with a scooter. We used to sit and look at the engine and try to figure out which bits were which. Sitting at the kerbside dreaming I came up with a plan. I knew which bit was the carb and I had a propeller from my model aeroplane. If I could rig up a belt drive to the propeller with some ducting I could blow air into the carb and make more power. I asked Mr Clark (only ever 'Knobby' behind his back) if it would work. “You’re on the right lines” he said “go and look up 'supercharger' in the library”. It was a bit more complicated than I had imagined!

Turbo Technics

This company did a lot to pioneer the turbo conversion business in the UK. More recently they have come up with a turbo compressor wheel driven by belt via a special gearbox. Basically the TT supercharger is a turbo driven at 120,000rpm by a belt off the crankshaft. There are some disadvantages to this system over a turbo but there are also two major plus points. First there is no exhaust heat to cope with. I for one am not too happy with the idea of a cherry-red lump of cast iron glowing away under the bonnet. Better still the drive to the compressor wheel is direct. You get the same boost, at the same rpm, every time you open the throttle. Here are some recent experiences:

340R

This month I have seen three different examples of the TT blower in three different applications. The first was a Lotus 340R which came in for a quick rolling road check. After a few days playing with the blower and the map settings we saw 270bhp from this engine. The only down side is the poor idle quality, I believe caused by the plenum-type intake system.
One of the big attractions of the TT blower is that you can still tune the engine in a conventional manner. Apart from compression ratio, you can port the head, fit big cams, fancy exhaust systems and fit throttle bodies (more of that with the next car). The peak gains are not as big as a turbo, but when you drive the car it’s like having a much bigger engine – power is instant. Okay, so the 340R is really making 285bhp but you lose out about 15bhp through the blower drive. The end result is still a breathtaking driving experience.

Rover BRM

This car was interesting in that it had already been converted to Lumenition throttle bodies, prior to the blower being fitted. This meant making up the induction system to blow through the bodies. In theory this is not as efficient as throttling before the blower intake (as with the 340R above), but the result on this car was a super smooth idle and instant throttle response.
You’ll have to take my word for it but working the throttle you would never know that a blower had been fitted. About the only give-away on the rolling road was the boost showing on-screen. Our new TAT software logs boost and you could see it going positive with just a whiff of throttle. You can’t get that with a turbocharger - 230bhp in a front wheel drive car is interesting to say the least.

Cheetah

Andrew Varey was looking for more power from his home-built Suzuki Hyabusa-powered sports car. He has joined a race series where modifications are pretty free when you only have 1300cc to play with. I suggested that he try the TT supercharger unit on his car. Although it is only 1300cc (against the 1800cc of the K) it still pumps a lot of air, enough to make 185bhp as standard.

Andrew and his Secret Weapon (that’s Andrew’s Dad; Brian Varey) put the blower unit on the chassis way back behind the engine. The compression was lowered with some 8.5 to 1 forged pistons and they then made up a new air box, with four additional injectors fitted into it, (fabricated in 3mm aluminium sheet). This has a second set of Hyabusa injectors in little bosses welded into the plenum. The Emerald software allows you to run different size injectors, upper and lower, but in this situation the additional injectors were there to make up the fuel flow, not to cool the inlet charge. We set them to force over at 80per cent of duration on the primary set.
A few interesting things happened on the rollers. First off one of the injectors started to fall out of the fuel rail. We stopped the mapping session and I turned up some plastic spacers to clamp the injectors between the fuel rail and the bottom of the boss. Next the aluminium plenum started to blow up like a balloon! It’s hard to believe that just 12psi air pressure would do that but I was seeing it with my own eyes.

Eventually we had the engine mapped to 10,000rpm but we had a small problem with maintaining boost pressure. This we put down to belt-slip due to the very long belt run so an additional tensioner will be added at a later date. At 225bhp it might not sound like a massive gain but don’t forget we were losing about 15bhp by driving the compressor. The biggest gain was that we had positive boost on the slightest of throttle opening.
Andrew did an event that weekend and said that the engine: “pulls like a V8” so he was pretty happy with it. There is still plenty of development to come but I think this TT compressor route will prove faster than a turbo conversion, just on driveability. I’ll keep you posted as the car develops.

Dodgy Injectors

Until we bought the ASNU injector tester/cleaning machine I don’t know how we used to manage without it. We get so many cars in here with dodgy injectors. A Rover V8 recently had a set of brand new injectors fitted prior to a mapping session but only six of the eight were working! The ASNU brought them back to life.
Then we had a supercharged Golf with very marginal fuelling at the top end. The injectors turned out not to be the expensive mega-flow jobs that the customer had paid for. The guy doing the conversion had just put the fuel pressure up to 5 bar.

In the photograph you can see four injectors under test. The spray pattern on number one isn’t great but number four is hardly working at all. No amount of cleaning or basket filter replacement would bring it back to life. There was no option here but to fit a new injector.

Don’t start from here

I had an Elise in for mapping and the owner was very worried about passing the MoT. I have to say that more than a few Elise owners I know have removed the cat altogether. But as long as the cat is fitted it isn’t difficult to pass the MoT test with the K Series engine.
Having hooked up the gas analyser I use the “don’t start from here” principle. I leave the closed loop switched off and manually adjust the mixture as close to spot-on as I can get it. This means looking at the sites either side of idle and at fast idle (2500rpm).
Once I have it as close as I can get it I enable the lambda closed loop but limit the swing (it’s all adjustable in the software) to about 2-3per cent. The closed loop software then has almost no work to do because the mixture is going to be about right before it starts doing its stuff. I’ve had a 230bhp Caterham idling with zero CO and zero HC and it passed the SVA test without any problems using this system.

The same principle is employed in boost control. Set the boost manually using the keyboard and then enable the automatic bit. That way the boost-control-valve setting starts pretty much were it wants to end up.
The exception to this rule seems to be traction control. If it was as easy as some people say, how come Renault has the best launch control in F1? You would think that MacLaren or Ferrari could be just as good when they have something like a hundred software engineers at their disposal. There’s obviously more to it than meets the eye. Anyone out there know how it really works? Obviously someone knows but do they want to share it with the rest of us? Probably not!

Rave Says:

I don’t hold with superchargers at all: big lungs that’s what you need. A length of hose on the intake via a t-piece and you just stick it in your mouth and blow. Of course, not everybody’s lungs are as powerful as mine, blown an engine block or two apart in my time; but then I am blessed with an exceptionally big mouth too. Few people have ever argued with that statement I can tell you. Why, I remember the time…(yes, you probably do – Ed)