Those funny things tee’d into intakes…

Posted on November 30th, 2003 in Opinion by Julian Edgar

One of the unheralded changes that has occurred in engines of the last decade is the use of resonant volumes on the intake. You know, those odd blind-ended boxes and tubes that you can see under the bonnet, tee’d into the intake. Sometimes they’re long and thin, other times they’re short and fat. Often they’re in full view but every now and again they’re hidden inside a guard or under a radiator cover plate. So what are these resonant volumes for?

And how do they work?

As the name suggests, they’re part of the ‘tune’ of the intake system. As more commonly understood with exhausts, the opening and closing action of the valves creates a rapid starting and stopping of gasflow in and out of the engine. Each time the inlet valves close, the columns of gas rushing in towards each cylinder are abruptly stopped. This creates a high pressure wave that gets bounced back along the intake runner. When it reaches the beginning of the runner, it’s reflected back towards the intake valves. If the intake runner is of the right length, the reflecting high pressure wave will arrive just as the intake valves are again opening – which will help jam in more air.

Hard and honest car assessments

Posted on November 16th, 2003 in Opinion by Julian Edgar

The other day I was in communication with an engineer who works for an Australian car company. He’s also an AutoSpeed reader, and our discussion initially wasn’t about his company, but about a personal matter. Simply, he had read that I’d bought a 1988 Maxima Turbo grey market import and was wondering whether I’d like to buy the Nissan workshop manual for a car which came with a very similar engine. He had the manual but no longer needed it. The answer was that yes, I would like it, and over some subsequent emails some amiable negotiating went on over price.

That sorted, the conversation turned to a car that he was driving – his company’s latest and greatest.

In one email he described – at some length – what a wonderful car it was. He listed many other cars that he had driven and/or owned, commenting how good his company’s product was in this light. Since I have heard this from employees of every car company I have ever had contact with (ie ‘my company’s latest product is fantastic’) I simply raised my eyes heavenwards and sent back an email suggesting that I’d heard it all before, and could he come up with some faults that the car had?

This is an anathema to anyone who works for a car company: the current model is always so perfect that nothing could be better… until the next model comes out, of course. To give the man his due (I think he was genuinely enthusiastic about the product, not just pushing the company line), he responded with a few problems he perceived with the car.

Trouble is, they were relatively trivial…

A range of tech tips

Posted on November 2nd, 2003 in Opinion by Julian Edgar

With the use of remote filter airboxes (and intercoolers in all turbo cars),

there’s plenty of plumbing through which air has to flow before it can become part of the combustion process. Then of course after the burn has happened, the exhaust – again, a long piece of bent pipe – has to be negotiated. The flow through these bends therefore becomes an important part of performance. Sometimes in automotive modification we tend to think that we are inventing something new, but there are plenty of other industries where the flow performance of long pieces of bent tube is critical to the performance outcome.