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Some of this week's Letters to AutoSpeed!

16 November 2003

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A Matter of Manifolds

I have been enjoying all of your junkyard and low budget tech articles for the past two years. I have even been adapting some of your ideas to my own turbo project car - a 1977 280Z with a 1982 280ZX turbo motor. I recently decided to run the stock cast manifold due to its durability and I was wondering if you guys are planning a test between cast and tubular manifolds?

Kyle Kuhlmann

We have done a couple of stories covering cast and tubular manifolds (see "Buncha Bananas", "Out the Exhaust - Part Three" and "Spool Time").A side-by-side test would be almost impossible to perform.

Down with the Drone!

I was just reading Response at and came upon "Damn Drone!" from Gordon Pieterse, South Africa. I think I know exactly what he needs...

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The short answer is to mount something like the Moroso Spiral-Flow or a Flo-Pro Twister muffler immediately after (or in place of) the cat converter. Follow this with an effective straight-through absorption muffler like those made by Borla.


The Moroso and Flo-Pro designs are very similar and very cost effective. Each uses two different length flow paths for the exhaust - one path is around the circumference, the other is straight through a centre pipe. The length of these two paths allows destructive interference of the acoustic waves as specific frequencies. This can be very efficient at reducing loud resonances IF they are tuned fairly close to the offending frequencies.

Word on the street (and track) is that the Moroso Sprial-Flow muffler is very good at reducing cabin resonance in cars with large, open flow exhaust system with or without turbos. It offers less restriction (it seems) than chambered mufflers, but is very effective where most resonance occurs (about 3000 rpm).

Martin Queckenstedt

Unorthodox Drive

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I wanted to contact Unorthodox Racing at their website after reading "Michael's Speed Zone". There seems to be no email and I was wondering if you knew how to get a hold of them? I'd like a crank pulley for a 1999 Mazda 626 2.0-liter 4 cylinder.

Randy S.

Try There's a Contact Us box on the site.

'Cooler Comparo

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Excellent timing on the intercooler article ("The World's Biggest Intercooler Comparison - Part One")! I am just about to purchase a JDM Galant VR4 (another excellent article by you guys!) and the info on the intercooler was a real eye opener. I had always thought that bigger was better, but please bear with me on this... The mass of the core is important in regards to dissipating heat while intercooler flow is important in regards to spooling the turbo up? Does that mean if I intend to use the car for occasional track days that mass or flow is more important? Additionally, is there any way to improve the flow or do you just ditch the 'cooler and throw in another one? Keep up the great work.

Brett Clarke

The mass of the intercooler is important for absorbing short stints of boost, which is typical in point and squirt traffic conditions. The biggest advantage of a high flowing intercooler can be found at high rpm and load, where the engine is consuming a huge mass of air. A good 'cooler will pose minimal flow restriction between the turbo and engine, while a poor flowing core will require you spin the turbo harder (and generate more charge air heat) to achieve the same manifold pressure. It's difficult to improve the charge-air flow through an intercooler without inserting a new core and/or end-tanks - you might as well "throw in another one" in most cases. For track work - where boost is sustained for long periods - the cooling volume of the core is most important. Bigger is generally better in this regard (ignoring internal design, etc).

Dyno Details?

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I am playing around with a dyno program from the 'net - program requires detailed specs on the car such as gear ratios, Cd, etc. Do you know where this sort of info can be found? I notice most of your articles quote this sort of information, but it is not in my car's user manual and I can't find it on the 'net (I have a 1992 Mazda 323 Astina SOHC). Any leads will be gratefully accepted.

Stewart Hamey

Aerodynamic figures and other tech data are often quite difficult to find - particularly as the car gets older. The best way to obtain this info is to look back through old car magazines (accessible at a public library near you) and search the web (as you've already tried!).

Come to Me, Cdti...

I would like to know if there is any way to get an Opel CDTi 1.3 litre Ecotec 4-cylinder diesel engine in Australia and what would be the best way to get it.

Brian Stocks

Try Holden Australia or Opel dealers overseas - maybe some readers can help out?

HSV Holiday #1

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Re Julian's visit with HSV "The Spin Circuit"... All very valid observations from another who is perhaps cynical of marketing spin. Just because it's new doesn't mean it's better. I read with utter confusion why a manufacturer might say that the new car has x% better torsional resistance, x% better power, x% better this that and the other. Does this mean the previous model is a heap of sh*& and should be sold immediately before it kills you? I think not. Why else would we restore older cars? It's all about what appeals to you. Why else would there be a '67 Alfa GTV in my garage when my daily cars have been more modern (fuel injection, turbo, electronics, etc)?

I hope that Julian isn't a victim of a company shutting down freedom of speech and that more journalists get to the real questions. Who cares if their green is better than yours, or worse "they aren't even on our radar"?

Simon Brown

HSV Holiday #2

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I've written to AutoSpeed briefly in the past about little things, but I wanted to convey my thoughts on the article "The Spin Circuit". The Spin Circuit is, possibly, the best technical-or-not thing I've read on AutoSpeed since I began reading. It had everything - from the marketing crap, to who'd speak and who wouldn't, other journalists' behaviour and more.

I just have two points to make - first, I hope the candid material you got from those sadly rare interviews sees the light of day in future articles. And, second, did HSV fly you business class or economy? That'd be an interesting footnote to add to the article. That said, though, congratulations for continuing to try and raise the ethical standard by noting such details.

Chris Waltham

Julian was flown economy class and, yes, there will be stories appearing from those interviews

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