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Some of this week's Letters to the Editor, discussion group posts and other feedback!

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Coming AutoSpeed Changes

Just read your proposed changes list with a sense of increasing anticipation. I look forward to seeing the 'new' AutoSpeed. Good work on the articles so far and good luck for the changes.

Mike Brothers

Just read issue 150 ["From the Editor"] and wanted to congratulate you on the success of your 3-day staff meeting. I say 'success' because the ideas you introduced in your column sound excellent. Can't wait, bring it on!

Rob Haylock

The changes to AutoSpeed you have outlined in your editorial sound great. Features for indexing past articles are useful. With so many articles it is difficult to find them. Another feature that would be useful is to track which articles each member has read. I periodically browse past articles and quite often cannot remember which articles I have read.

Some other ideas:

  1. The only way to see the result of the weekly poll is to vote. After voting the results should be displayed, rather than the question. This could be done with a cookie.
  2. It would be useful to be able to rate articles. It would give you good feedback and publishing the average ratings would indicate which past articles are worth reading.

I enjoy reading AutoSpeed and have also purchased 21st Century Performance. I enjoy the do-it-yourself articles and as I own a Skyline GTSt - I enjoy articles on imports and turbos.

David Radnell

The proposed changes sound great - I look forward to seeing them. User relevance grouping of articles will be really useful. Glad you're looking to improve an already good magazine. A quote from a recent company training course I did was "If you're not getting better, you're getting worse".

Patrick Felstead

I enjoy viewing your website and find it contains much useful information. However in your 150th issue letter you make mention of the fact that you will be reducing the number of free articles available to readers. I am a university student living away from home and as such finances are pretty tight, a subscription to AutoSpeed is a 'want' and not a 'need' and therefore doesn't make the budget; if you were to reduce the number of free articles available your website would no longer hold my interest. I have recommended the site to several of my friends some of which have purchased subscriptions and would continue to recommend the site if the current level of free articles were to remain or increase. I don't mean to complain, but if you're on to a good thing why not stick to it?

Glenn Maughan

Thanks for the positive feedback, everyone. Glenn, it is extremely unlikely that your budget is so tight that you cannot afford to pay one dollar a week.

Recommending Workshops

Last week in the 'Response' column you said that you couldn't recommend an exhaust shop in Victoria to someone who wanted to know a good place to get his exhaust fitted. I can see reasons that you can't tell people the workshops not to go to (ie because of legal reasons, etc), but why not tell us about the good workshops that you know of?

Bryan Beret

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Hmm, good question. Firstly, we have never heard of any workshop that didn't have at least a few unhappy customers - so even the best workshops will have detractors. However, in general, as well as looking at how personally relevant the type of work is that they do (eg predominantly V8s or mostly turbos), one of the best guides to a workshop's quality is to look at their equipment.

AFAIK, the best-equipped workshop in the country is that of Beninca Motors [] in Melbourne. They have a chassis dyno (soon to be four-wheel drive), engine dyno, shock absorber dyno, flowbench, digital balancing machine, all types of welding equipment (TIG, MIG, gas and spot) and a full machine shop with CNC mills and lathes. Throw in staff with degree-level qualifications in mechanical engineering and computer science, decades of motorsport experience (including winning Australian championships) and you have an extraordinary workshop.

Other highlight modified car workshops around the country include Melbourne's Nizpro, Sydney's Silverwater Automotive, Brisbane's Bob Romano Motors, the Gold Coast's ChipTorque, and Adelaide's Awesome Automotives. Each of these workshops has brainpower, experience and high capabilities.

Leaking Pshhht!

After disconnecting my blow-off valve from the intake on my air-metered car and trying your method to have satisfactory idle relating to your article "PSSSSHHHT" it worked fine. However I noticed that when on full boost the blow-off valve began to open without lifting my foot off the throttle, so not allowing maximum boost to be reached. I then began to have a think about how this could happen and came up with this conclusion:

Because this system alters the strength of the vacuum system at idle it also alters the boost when on full boost thereby changing the pressures on either side of the diaphragm inside the blow-off valve allowing it to open before full boost is reached as the air escapes out of the blow-off valve instead of entering the intake manifold.

This is just a theory of mine but what are your thoughts on this?

PS my car is a WRX with boost set above factory at 1 Bar or 15 psi - could this be the problem?

Steven Collins

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Your theory may well be right. However, if in fact that is the problem, it is easy to overcome. Just add a one-way valve (eg a brake booster in-line valve) to the system as shown in this revised diagram. As the flow through the system will now be altered, you may need to re-adjust the controls to get satisfactory pssshting again.

Tyre Widths

I've recently discovered some new (to me anyway) info on tyre specs. Maybe you could confirm this for me? If a tyre is spec'd at 195/60/15, the 195 figure is not the actual tread width but is the widest part of the tyre when unloaded and inflated to the recommended pressure. In the tyres I've looked at this seems to occur in the sidewall.

Does this sound right? A few measurements on actual tyres seem to bear this out and confirms that the actual tread width is around 20mm less for this style of tyre. Obviously, this will vary from tyre to tyre, brand to brand, and the difference should reduce the lower in profile you go. Also, (from recommended wheel sizing) all things being equal, on a given rim a higher profile tyre will allow a wider tyre. The two tyres would obviously have different cornering characteristics, but is one necessarily more sticky than the other, or will the lower profile tyre last longer?

It makes tyre selection a bit more confusing, especially when considering your earlier articles on width, profile and heat buildup etc.

Love the tech articles, I'll definitely keep up my subscription.

Bret Parker

We have mentioned the variation in nominal tyre widths in a column - "Michael's Speed Zone" - and found in fact that there is even more actual variation than you imply. As to your other points, well, your guess is as good as ours!

Freelance Contributions

I'm upgrading our course in Freelance Writing and am locating magazines on the Web that our students could look at as examples of publications they might contribute their work to. I read through your Freelance Guidelines ["Freelance Guidance" ] and would like your permission to include them, in full, in our latest course notes. It is very helpful for our students to see the 'real-life' requirements of publishers - perhaps you will get an article or two from our students. I'll include your web address so students can view this text on-line as well.

Thank you for your assistance.

Ian Ryan
Professional Writers Training

No problem.

Smooth, Silky Skin?

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Do you have any idea how rough a surface has to be to have a minimum air resistance? Cause I'm a sailer, I know that using fine sandpaper for grinding the hull reduces the water resistance. 3M is currently testing a so-called riblet foil to reduce the air resistance of airplanes.

Jochen Herrmann

Generally the surface should be as smooth as possible to reduce skin drag, but most aerodynamic drag on a car is 'form drag' where the shape of the car is much more critical than skin smoothness.

Blow-Off Valve and Idle

Knowing that you and your staff own or have owned several Liberty RS Turbos, I was wondering if you could help me by explaining whether or not the factory blow off valve has a bearing on the idle speed of the engine? I have found that by pulling the B/O valve out of the intake duct (and plugging this hole) and having it vent to atmosphere (hence "noise"!!) has caused the engine to 'rev' at idle for about 30 secs before settling down. I realise that you prefer not to answer engine problems but have found no one locally that can give me a logical answer...usually a lot of BS!! The local Subaru dealer was VERY vague also. Many thanks if you are able to help.

Jon Stow

Many factory blow-off valves are open at idle vacuum, and this would account for the change in idle speed. Refer to our Pssht! article at "Psssshhht!" for a means of overcoming this problem without spending much. Note that we have a slight upgrade to this approach mentioned above.

Oxygen Injection

I've just found and read an old magazine from early 1998. In it Julian Edgar discussed the idea of oxygen injection. The article says he didn't carry out the test. Did he in fact proceed with the idea at a later date? The idea is one I've been curious about for a couple of years myself. If he did follow it up I would love to hear about it. Keep up the great articles in this online magazine, I really enjoy them.

Rob Grant

While Julian Edgar did not carry out any further experimentation, some readers of the story did go ahead with the technique on a naturally aspirated Laser. They reported great success.

ECU Capability With Boosted Power

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I have a question regarding my '83 Mitsubishi Starion. I'm sure you will know that JA Starions were not intercooled, so I'm planning to go ahead with installing an intercooler. My question is: will the standard ECU be able to cope with an intercooler, 14 psi, 2.5-inch exhaust and an upgraded filter? At the moment it seems fine (with the exhaust and filter), but I am wondering if the intercooler and boost will mess things up. I'm not sure what sort of power this will all make, perhaps around 60% up on stock? (Stock is 125kW-6psi) I had no worries spending the money until I was reading Julian Edgar's book (21st Century Performance), in particular the ECU chapter, and read that standard ECU's can handle around 10-20% more power with no problems.

What sort of modifications will need to be carried out to handle this extra power? Is it expensive? Any help is MUCH appreciated. Thanks.

Dane Shackle

It is a safe rule of thumb to assume that pretty well all ECUs can cope with a 10 - 20 per cent power upgrade. We can't comment specifically on the Starion, but on all cars there are two main areas to look at: fuel supply and ignition timing.

When you are implementing a 60 per cent power increase you are implicitly assuming that the fuel supply system (eg pump, pump pick-up, fuel pressure reg) was designed from factory roughly 60 per cent bigger than it actually needed to be. This is quite often not the case, so assessing how good the fuel supply system is can be an important step. A simple way of doing this is to measure the fuel flow at the maximum rated boost pressure (in your case, applying 14 psi boost to the manifold connection of the fuel pressure reg (we assume that the throttle body style injection of the Starion uses a conventional fuel pressure regulator). Using the figures regarding fuel flow that are covered in the book, you can then work out if the fuel supply is sufficient.

Next, can the electronics cope with the extra fuel supply needed? This can be dependent on two factors - are the injectors physically big enough to handle the fuel flow required, and can the ECU understand the amount of fuel that is actually needed? By measuring the duty cycle of the injectors (what proportion of time they are open) as the load increases, you'll be able to see how close to 100 per cent duty cycle is being used. (100 per cent duty cycle means that they are fully open all of the time - they can't pass any more fuel). Typically, a turbo car hasn't got big enough injectors to cope with the sort of power gain that you are suggesting. In this case, you can do a number of things - use bigger injectors and have the ECU re-mapped (or the load output signal altered), add extra injectors triggered by another ECU or by the factory ECU working through a pressure switch system, or raise the fuel pressure (eg by fitting a rising rate fuel pressure reg).

If the injectors aren't reaching 100 per cent duty cycle but the engine is still running lean, you need to then look at telling the ECU that more fuel is needed. This can be achieved with re-mapping or fooling certain ECU inputs (eg the engine coolant temp sensor or load sensor).

Once the fuel side of things is worked out, you need to then make sure that the engine isn't detonating because of inappropriate ignition timing being used with the greater power output. Keeping the intake charge as cool as possible is usually effective enough that no ignition timing changes are needed with this sort of power upgrade, especially in a car that wasn't intercooled in the ex-factory guise. Water injection is also a superb (and massively under-rated) way of controlling detonation. However, if required, the ignition timing can be changed by altering the input of certain sensors (eg the intake air temp sensor), certain ECU outputs (eg the ignition coil trigger) or by ECU re-mapping.

As to cost, if the car is a $2000 roughy you could make all of these changes on a DIY suck-it and see approach for less than a few hundred dollars - even including another fuel pump. On the other hand, if the car is your freshly re-painted, pristine pride and joy, the bill for injectors (and a multipoint manifold in the case of the Starion), programmable ECU, dyno tuning and the rest of the bits could cost you $10,000.


Congratulations on a great site. The information on this online car site is better than any magazine I have ever bought.

Rob Moulton


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