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Variable Nozzle Turbo Boost Control

In response to Brilliant Boost, I don't think this approach will work with variable nozzle turbochargers (VNT).  My car (Ford Focus turbo-diesel) has one, and boost is controlled by varying the angle of the turbine nozzles which vary the angle of impingement of the exhaust gases onto the turbine blades. This is I think is supposed to increase the range of engine speeds over which effective boost pressure is available. The vanes are controlled by the ECU and there is no wastegate.  I assume in these cases the boost would need to be raised by remapping the ECU. VNTs can usually be identified by the actuator linkage and pivot attached to the turbine housing.

Ben Garside
United Kingdom

As you have said, a pneumatic boost control modification is not suitable for a variable nozzle turbo. By now you will have seen Turbo Diesel Hilux Power! which covers the power-up of a diesel engine with direct ECU actuation of the turbo geometry.

Ben Again!

In reply to Peter Bodon's letter in Response, diesel tuning is already big business in the UK and Europe, since around a third of cars sold here are now diesels, mostly turbocharged. Tuning generally takes the form of chipping, adding on a tuning box or remapping, with or without a rolling road session.

Companies often quote increases of 20-30% in power or torque available without resorting to further mods such as free-flow intakes or exhausts. Check out companies such as Superchips (, Tunit ( and Van Aaken ( I'm sure at least some of these type of products must be available in Australia.

I've driven the Prius a few times - we have a number as pool cars at work - and also various turbo-diesels (I own a Ford Focus TDCi) and, for me, the effortless low-to-mid-range punch and relaxed high-speed cruising of a modern turbo-diesel beats the Prius hands-down every time. Open road fuel economy is pretty similar as the hybrid gives its best results around town.

Ben Garside
United Kingdom


I write to offer an observation on repeated articles. Whilst I would rather not see them, that is not the main reason for my email.

I note that recently you have published a number of letters offering negative feedback regarding repeat articles, but none offering positive feedback (that I could see, anyway). Either you are choosing to only publish negative letters, or you have not received any positive ones. Whatever the case is, it's not a good look when you are constantly publishing only these negative letters and then defending them, and in one recent case, quite abruptly (the “vote with your money” response). I do note that you have subsequently removed it. All I am suggesting is that you give consideration to balancing the negative feedback by publishing some letters in support of the repeated articles, if you have received any.

You have stated that you are unlikely to change this editorial policy, and at the end of the day, it's your magazine and you can publish what you like. As a long-time subscriber, it won’t cause me to discontinue my subscription; I just fear that if you are seen to be resisting frequent calls to reverse the policy, it might give the perception that AutoSpeed is not giving what the readers want. I'm sure this is not the case, but as you are well aware, what the public see and what is the reality can be very different things. In closing, despite my feedback above, I believe AutoSpeed is a good alternative to the mainstream car magazines (to which I no longer subscribe), and while it remains that, I'll continue to be a reader.

PS: Please, please, please give consideration to bringing columns back. When I do read a mainstream car magazine, I always go and read them first.

Brendon Black

The reason for the existence of Response is to allow readers to complain, state where corrections need to be made – and yes, occasionally praise us. To suggest that “it’s not a good look” when we publish criticism is to completely miss the point of why Response exists. Incidentally, we have not removed the reply from the previous Response that, should a reader feel sufficiently aggrieved with our editorial changes, they have the option of withdrawing financial support. Nor do we consider such a sentiment abrupt: it’s a fact that should be stated.

We have received no letters specifically in support of repeat articles. That’s not surprising since contributions to Response are limited to subscribers - and long-term subscribers are those most likely to have previously seen the repeated material. Instead, to gauge the popularity of repeat articles, we refer to Reader Ratings (ie the score subscribers can give by clicking on the numbers at the end of the articles) and actual readership page views, which include both subscribers and non-subscribers. As we have previously said, both sets of stats show that repeat articles are popular.

Re the columns: where have you been? The columns were dropped about 5 years ago....

Falcon Exhaust

I fitted the Jim Mock Motorsports exhaust to my 94 NC Fairlane in combo with existing Pacemaker extractors about 18 months ago. This was followed by a 10,000km "test drive." The improvement in power off the mark and through to 4500 rpm is awesome. There are no droning noises and the exhaust noise is well within legal requirements. It is easy to forget the improved exhaust is fitted until you put your foot down. Power uphill is dramatically improved and overtaking is a breeze. Average fuel consumption improved from 11.5 l/100km to 10 l/100km. Considering this was with a fully laden car with four adults on board (about 2 tonnes all up) and driving through days up to 39C heat, I reckon the exhaust was worth every cent.

It would be interesting to see the results of the same exhaust fitted to your test Falcon.

Russ Bathurst

Where are the Diagrams?

Water Injection is a very interesting article, which is unfortunately let down by a lack of your usual brightly coloured diagrams; this would greatly improve comprehension of the systems proposed.

Ashley Rogers

Fair point. The whole topic is very interesting and is one we keep meaning to revisit with a fuel economy-based project. We promise we’ll use colour diagrams then!

Diesel Emissions Technology

Your magazine is top shelf for technology reviews. As such, I would love to see a review of the current diesel NOx abatement systems, with and without urea injection, to meet the Tier 2 Bin 5 emission requirements, including assessments as to hardware complexity (maintenance/control), performance and/or mileage impacts, etc. Other diesel emission abatement equipment assessments, such as particulate filters, would be a plus.

Dennis Waller
United States

It’s an area we expect to do a tech article on in the near future.

More Complaints

Something which has always attracted me to AutoSpeed has been the constant source of new ideas, innovation and the practical technical articles. However, I think some of the latest changes are taking AutoSpeed into the territory of the boring monthly magazines. As you have pointed out before, it is common for monthly publications to repeat topics every two or three years as new readers come on board. AutoSpeed's recent adoption of this principle has significantly decreased my reading enjoyment! I for one would support increased subscription fees, or an increase in site advertising, to support a return to the “one new article per day" editorial policy. Yes, I realise I might not be in the majority with the first suggestion, but I think its something which requires serious consideration.

Grant McAuliffe

Let’s be blunt: no modified car publication in the world has over the long term a constant stream of new, worthy ideas and innovation. Some can sustain it for a period; none can sustain it indefinitely. We have never made any pretence that we are a “constant source of new ideas [and] innovation”. How many ways can you do a car exhaust? How many ways can you do a car intake? How many ways can you do a turbo boost control?

But that said, in the same way that we have been doing for the last 8 years, we strive to put a new slant on car modification and technology. In just the last 8 weeks we’ve done stories which, we think, you’d look a long way to find in any other modified car publication. Stories like Diesel Hybrid!, Building a Work Bench, Springs and Natural Frequencies, Common Rail Diesel Engine Management, Part 1 and Common Rail Diesel Engine Management, Part 2, Spring Swaps!, How Heavy's Your Knob?, The New Intelligent Intercooler Water Spray Controller, Part 1 and The New Intelligent Intercooler Water Spray Controller, Part 2, and The New Global Hybrid System.


Just wanted to comment on the excellent article on fitting the exhaust system (see Frank's Exhaust, Part 2).  I have read Julian Edgar's excellent book "21st Century Performance" recently cover to cover.  Finding AutoSpeed only recently and then the added bonus of his articles that are not only informative but definitely focussed on the real world of true motoring enthusiasts, made my decision to subscribe both easy and rewarding. Back to the exhaust article: this has provided me with a lot of information for some modifications I wish to make on my current exhaust system.  So a big thankyou.

Ashley Biermann

Won’t be Coming Back

Your review on the new Astra SRi Turbo is very unusual for a so-called motoring expert web site.  Also you say the Focus XR5 is fantastic yet it is so noisy in the cabin (tyre and road noise), a just as hard ride, no foot rest, no cruise yet you say it is fantastic. It has massive torque and weight at the front.  Like the Mazda 3 MPS, too much for a FWD.  When you give it a blast (like any other turbo) it will also give you 13L/100km. Same performance as the Astra. Sure a good car but fantastic? I won't be returning to your web site, not for me but some will like it.



Is it possible to print readable versions of the thumbnail pictures that come with the technical articles?

Fred Temple
United Kingdom

In nearly all cases, clicking on the picture will bring up a larger version.

Likes Audi Test

I just changed my vehicle from an '03 BMW M5 to an '06 Audi S4 Avant and having had it for a few days and being rather disappointed by the performance, decided to Google some reviews to see if it is just me or my vehicle.

Your Audi S4 Road Test is absolutely spot on. I have the exact same feelings about the curious throttle response, wooden and understeery chassis and complete resistance to throttle steering. Add to that list pedals poorly placed for heel-toe downshifts and slower than expected acceleration and I’m starting to miss my M5, which did everything the complete opposite. That was a far, far more thrilling car and just loved to hang the tail out.

The S4 is good for people who drive on part throttle and never venture near the limits of adhesion. Driven in these conditions the S4 is in its element. Beyond that, it falls apart and reveals Audi's real philosophy, even for their S models: safety and security but zero excitement.

Some further Googling revealed that you are the only magazine to REALLY say it how it is. These problems are barely alluded to in other reviews and I appreciate your honesty. I have bookmarked your website!

Sam Pat

Oval Shaped Chain-rings 1

In your latest driving emotion 'Engineering innovation that leaves modified cars for dead' (see Driving Emotion) you spoke of the oval shaped chain rings and their lack of popularity in pedal powered machines. I own an older model race bike which I received free from someone who didn’t want it any more and noticed that the chain ring was oval. Because I had never heard of this before I went to the bike shop to ask about it. The store guy told me that this system is unpopular because it leads to knee injures so that would explain the lack of popularity. All I can say is while I now have a new bike I haven’t had any injuries after riding the oval for 2 years, and now my dad rides it and hasn’t had any injuries either.

Hope this helps, and keep up with the articles on cheaper fun cars for young people with no money!

Joel Garrigues

Oval Shaped Chain-rings 2

Interesting what was written by about the oval cogs for bikes. I had used these on a pushbike nearly twenty years ago. Yes they are excellent but they have one major downside which caused me to remove them, that being - every 13 revolutions or so, the whole pedalling process resets itself. For one whole single revolution your legs completely 'free wheel'! You can still order them from most bike shops in Oz but the bike sales staff will more than likely try to talk you out of buying them.  Surprised this never got mentioned, that's why they never took off.

John Kirkham

There is no reason why oval shaped chain-rings should exhibit the behaviour to which you refer – and as far as we’re concerned, they don’t.

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