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Some of this week's Letters to AutoSpeed!

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Butterfly Catching

You have an article on your site Butterfly Effect - "Active Exhaust Systems' latest electronically-controlled exhaust butterfly..." How can I get more information on this valve and a price for it?


Contact Active Exhaust Systems Australia at or HyperFlow Technologies at

Airflow Data

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Do you know of any electronic products that show intake airflow in cfm, etc?


There is a variety of ECU reading software that will give you engine airflow data - assuming you own a relatively late-model vehicle. For more details, check out Reading Your Car's Brain - Part 1 and Reading Your Car's Brain - Part 2

More on EWPs

A newspaper appeared last week stating that Davies Craig has won a contract to supply electric water pumps to the manufacturer of the forthcoming Connaught GT coupe in Britain. Apparently, there will be several more production cars with these Davies Craig pumps fitted as OEM due over the next twelve months. BMW already uses an EWP in its 3-litre engines, but Davies Craig believes that it breaches their patents.

Are you able to offer us readers a brief rundown on what happened when you tested the EWPs? Surely there must have been some positive points - otherwise why would car manufacturers pursue the R & D into it? Perhaps see if you can do an article on retro-fitting a BMW unit?

Trevor Ng

We have not had any more experiences with EWPs since our original article in 2000 (Testing the Davies Craig Electric Water Pump - Part 1) and we are unable to present any of our test data.

Re Electric PS Search

In reference to your "Response" column this week - Response. There was a query about electric power steering. I know that 1989 model Suzuki Alto Works I.E. have a setup that looks very similar to the picture. Cars equipped with this feature have a ‘power steering’ sticker on the rear hatch glass, a control box under the driver’s seat and a heavily different loom to non power steer cars

Daniel Griffiths

Some Extra Nuts and Bolts Info

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I've just read your article All You Need to Know About Nuts & Bolts... It was generally a very informative article, however I did notice a few omissions that might require some clarification. I run the mechanical engineering department in the company I work for and thought I might throw in 2c...

You have gone to some trouble to describe the differences between the imperial fasteners "grades" yet you only mention metric "class" 8.8 steel fasteners. Metric fasteners are generally available in class 4.6 - a lower tensile strength grade. Class 8.8 fasteners are commonly available and are regarded as the lowest grade acceptable for structural applications. Class 10.9 is also available as the high tensile variant. As can be noted from the table in your article, class 8.8 is quite different to imperial grade 8 - the numbers must not be confused in structural applications!

It is worth noting that some types of fasteners are only available in certain classes - for example, socket head shoulder screws from quality manufacturers (such as James Glenn and Unbrako) are typically class 10.9 only. Likewise, you didn't identify preferred sizes. I recall in a recent article Julian noted that he was forced to rework because he chose to use M8 x 1.0 rather than M8 x 1.25 fasteners.

Technical drawing books such as "Technical Drawing" by A.W. Boundy, or "Technical Drawing - General Principles (as 1100.101-1992)" released by SAI have tables detailing which metric thread sizes are preferred within Australia.

In general, unless it is required for engineering or functional purposes, *never* use fine pitch threads as it will be very difficult to obtain fasteners. Sizes that are commonly used in general mechanical engineering include M4 x 0.7, M5 x 0.8, M6 x 1.0, M8 x 1.25, M10 x 1.5, M12 x 1.75, M16 x 2.0. M7, M14 and M18 are generally not used.

BTW, if you are not already aware, the best global repository for all information on threads is "Machinery's Handbook".  This covers everything from Metric to UNC, UNF, Whitworth, Acme and even Panzer thread information.

Adam Seedsman

Link Problem

In All You Need to Know About Nuts & Bolts, the links for the imperial and metric thread gauges point to the same place. I want the metric one, please.

Patrick Berry

Thanks for that - problem now fixed.

Love the Lamp

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Re the Zero Cost High Tech Interior Lamp...

Thanks for yet another great idea - it's often the little stuff like this that keeps me more than happy with the value of my subscription...

Although, I did not actually use my old scanner to make an interior light, your article made me realise I could quite easily gut, rewire, and transform my scanner into a light box for viewing slides and negatives, etc. (I'm mostly done, I just need to figure out how to frost the glass.)

In use, the scanner lamp throws out a really nice light - it has me itching to raid some second-hand stores in search of more old scanners as I can think of several more things I'd like to make with them. I'm currently thinking a compact portable work light - perfect when working under the dash and there isn’t enough room for the usual oversized auto lamp.

The only thing I came across with my lamp that differed from yours was that, when using it with a mains powered DC pack, my light wanted the full 24 volt 500ma supply from the original scanner - anything less gave a very dull light.

Kerry Novak

Excessive Drivetrain Loss?

In relation to the article of the 3.0-litre turbo Supra engine - 7MG Mega Motor!...

The power at the wheels is stated as being 570hp. The flywheel figure is quoted as being calculated at 850hp (or even closer to 900hp). Surely, the car would not be losing 280+ horsepower through the drivetrain?

Fergus O' Connell

The old fashioned auto trans would be responsible for a sizeable percentage power loss but, equally, the car is difficult to run on the chassis dyno due to tyre slippage – so the 280+ hp loss is an estimate based on these factors.


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