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Response

Some of this week's Letters to AutoSpeed!

24 August 2003

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Exhaust Studies

I was very interested in your editorial on motor tuning myths ("Autospeed's Myth Meltdown") - in particular the idea that an engine doesn't need back-pressure to give a good spread of power at low rev ranges etc.

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Since childhood I have been reading car and bike motoring articles about the effect on power bands of different exhaust and intake set-ups, and references to ideal back-pressure. Your own excellent periodical places great emphasis on intake set-up, with analysis of ideal intake pipe lengths, air-ram effect or not, etc., which seems to be in line with most other people studying the matter. You seem to argue, though, that the theoretical best exhaust for any engine at any rev range (ignoring noise and emissions) is direct to atmospheric. This does seem to make practical sense, but why is there so much analysis to the contrary?

Stephen
Ireland

We are yet to see an example where a greater amount of exhaust backpressure - downstream of a tuned exhaust manifold/extractor system - aids in producing torque anywhere in the rev range. This is assuming mixtures and timing remain near their optimal values - something which in comparative testing is often not achieved.

350Z Reaction #1

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Julian, get over it. You did your money on a Nissan R32 GT-R - if you had waited a couple of years I'm sure the pain would not have been as great. Attacking everything Nissan build will not regain your bank balance.

Loved the story on the 350Z vs Tamborine Mountain, though ("Driving Emotion"). I had the pleasure of taking my two daughters (ages 8 and 5) for a scenic drive up it in a Gold Coast micro hire car. At one stage we had the thing locked in first, foot flat to the floor and doing 20 km/h. It used half a tank of juice to get to the top, but was worth it. Next time will try with something half (?) decent - maybe a Z. Regards.

Rod Wilmot
Australia

350Z Reaction #2

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Julian, the article about the 350Z distresses me in regards to your adverse comments regarding this car. A HSV is not a sports car and their drivers generally cannot drive. HSV does a great job in making up for the lack of sporting prowess by chucking a lot of torque in the front. The Nissan on the other hand is a bold and very successful move to bring the company back to its fundamental ideal of what a sportscar should be. The 300ZX was an abomination and was the direct influence of people like you making comments like this. It was for the North American market who like big, heavy underpowered "sports cars" which did nothing for the purist. Now Nissan is the second most profitable motor manufacturer in the world... second only to Porsche. It makes me think that, like Porsche, they have some great thinkers at the top of Nissan who are uncompromising in their standings and the 350Z is the result... and a huge success. Just think what this highly engineered and efficient chassis is going to be like when it has the GTR spec. Let's think about the driver who is well rewarded in this case, not the majority, as it is a purist's car.

Craig Watson
Australia

Response to Response

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This is in reply to "Stick to Pick-ups and Old Triumphs!" by Shaun from the UK ("Response").

He says that half of our country drives in pickups and old Triumphs but I'm sorry to say that, from my experience as an Australian, only people from the UK would be silly enough to pay for a Triumph. I find it quite funny that he had a go at our motor industry considering that four of the most famous and greatest contributors in British motoring are now owned by Germans, Americans and Malaysians.

As for his comment on your review on the Alfa 166 ("New Car Test - Alfa 166 Sportronic"), the last time I checked this is an Australian publication, the majority of readers ARE planning on driving on AUSTRALIAN roads NOT European.

In conclusion here's my favourite quote from Shaun... "The 166 was designed for smooth European roads and not the Aussie outback, so we benefit more from the excellent steering and handling." I couldn't have said it better myself. Oh yeah, keep up the good work.

Kong Lam
Australia

What You Want?

As you have asked for feedback from "Driving Emotion" I will give it to you.

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First of all I would like to say that reading re-runs of articles in printed magazines gives me the sh&^s and, as you said in Driving Emotion, it did make me stop buying that magazine - so its a good guess that it would do the same on AutoSpeed. It is good to see all the articles about turbo upgrades, boost control, intercooling and the like, but what I would personally like to read is some articles on naturally aspirated performance upgrades - yes, you have already done some but I would like more.

Having said that, I do think that articles such as fusion intercooling and DIY adjustable temp switches are pure gold! The more the better - no matter what type of car they are for!

Ian Armstrong
Australia

How Much Boost For B16A?

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I would first like to say thanks for such an informative mag - I find it to be one of the most useful resources available. My question is related to safe boost levels. I drive a '97 Honda Civic hatch B16A V-Tec (CR of 10.2 to 1) on which I have fitted a Garret T3, custom intercooler and engine oil cooler - the internals are all stock. I currently run 0.35 Bar boost with no detonation (I am using a locally made Perfect Power SMT6i piggyback to drive one additional injector and modify the existing timing and fuel maps).

What I can't seem to get a straight answer on, is what boost pressure can I run without lowering the CR of the motor? I currently use a good quality 94 octane unleaded fuel. Am I correct in saying that I can run a higher boost level as long as mixtures remain correct? I wanted to run in the region of 0.6 - 0.7 Bar. Your help is greatly appreciated.

Gordon Pieterse
South Africa

A lot comes back to fuel quality. If your "94 octane unleaded fuel" is simple 94RON we'd guess you could probably run to around 0.5 Bar without too much problem - but only if the turbo has a cold air intake, the intercooling is moderately effective, the tune is fairly 'tame' and the car isn't given a hard time in really hot conditions.

If, however, your local fuel octane rating is calculated as RON plus MON divided by 2, you won't be able to run quite as much boost.

Aall this is just an educated guess, though. The best thing for you to do is read and act on "DIY Detonation Detection - Part 1" and "DIY Detonation Detection - Part 2".

And re "Am I correct in saying that I can run a higher boost level as long as mixtures remain correct?" Mixtures are certainly a large part in determining a safe boost level, but detonation must also be avoided at all costs. With rich mixtures and no detonation, your only other concerns will be clutch, gearbox, rods, etc!

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