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Some of this week's Letters to AutoSpeed!

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Big Daddy Mack

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Re your idea in Driving Emotion ("An intercooler fan powered by turbo boost")...

A similar idea has been used by Mack trucks for many years. The 30 old Macks that I have driven in the army use a tip turbine to power a fan that draws air through intercooler. You can hear it coming in and spooling up when you are trying to use high power at low speed. This was done as these old Macks spend a fair amount of their time out in the bush using full engine power but at low road speed. It’s not a bad setup for a 10-wheel-drive 30 year old truck that can pull 8 ton onboard plus a 20 ton trailer... I’m not saying a Mack intercooler setup would make it under your old Maxima but it could be a place to start looking to see how they have done it. I am not sure if they are using boost pressure to power the tip turbine or if it is inserted in the intake flow somewhere. I’ll leave that up to you guys to find out!

Keep thinking outside of the square - this is what I like to see.

While I am at it, has anyone out there had any experience with supercharging a 4.2 litre Jaguar XK engine? I’m interested to know if I am breaking new ground or reinventing the wheel.

Robert Williams

Thanks for that, interesting stuff – we’ll look into the Mack system a bit more. We haven’t heard of anyone turbocharging the XK engine – anyone else?

Troublesome Trans?

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I have a question to ask... I own a Holden VS V6 Commodore and have a problem with what I think is the auto trans. When I drive the car, its power seems to be all over the place with what seems to be gearbox slip. I have serviced the auto and maintain the car very well. Lately, I have given it a carbon clean, replaced the leads and put in a new set of spark plugs – and the problem is still there. I have also installed a sports exhaust and cold air intake.

When you pull up (say, at a set of lights), you can take off with a lot of revs but the car accelerates slowly. Other times the rear wheel break out in wheel spin and acceleration is excellent – it can do 0 – 100 km/h in 6.8 seconds. It will run 14.7 – 15.1 second quarter mile times but when it’s going like this it would have trouble doing a 17...

I have had the computer and sensors checked and they seem to be fine. I have been told the MAP sensor is noisy but apparently this won’t affect the car’s performance.

I am fairly sure it is the auto trans slipping but I’m not sure. Your thoughts?

Brad Walther

Hmmm – interesting one. It’s hard to judge without going for a ride in the car but it certainly sounds like there might be an intermittent problem with the trans. We suggest installing an air-fuel meter to make sure the engine isn’t doing anything whacky first, though – see Smart Mixture Meter, Part 1 for details on the meter. It’d also be a good idea to take your local transmission specialist for a drive and ask their opinion. You might also be interested to read Auto Trans Dyno.

RS v GTi-R

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Hey, your website is very informative - I always come on to find out the latest in cars.

Just a question... I own a 1991 Subaru Liberty FWD and wanna buy a new car next year. I’d prefer a turbo – I’m considering either a Nissan Pulsar GTi-R or a Subaru Liberty RS turbo. If you have any advice, it would be great.


The GTi-R is a better package for performance when left in standard form – but there’s no need to keep it standard! We suggest the Liberty RS as the better option since there are so many aftermarket and second-hand parts floating around to suit. New genuine replacement parts are also readily available.

Read Pre-Owned Performance - Subaru Liberty (Legacy) RS for things to look out for in a Subie RS. Also check out Supercar Steal for our GTi-R buying used article – but keep in mind this article was written a couple of years ago.

Clamp Currents

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Just a quick tip regarding current clamps you mentioned in "Using Multimeters, Part 3".

You rightly state that current clamps are inaccurate when measuring small currents – however, the situation can be improved (at times) by passing the wire under test through the clamp more than once. By placing more turns inside the magnetic core, the clamp becomes more sensitive by a factor of the numbers of turns present. Place the wire through the core twice and the voltage output of the clamp will increase by two times. This technique can be used to successfully measure small currents that would otherwise require you to break the circuit and insert the meter's probes.

Cary Wintle

Front Diff Findings

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I did a search of AutoSpeed and was not able to come up with an article on adding an aftermarket front LSD to a car (such as a Subaru WRX). This modification should improve AutoCross handling by reducing understeer.

If you haven't done that article/test yet... well, add it to your list.

Mako Koiwai

No we haven’t covered that topic. Good suggestion - we’ll keep our eyes open and cover it if the opportunity becomes available.

Pssstttt-ing Diesel!

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After reading the "Electronic Blow-Off Valve" article The Electronic Blow-Off Valve! in your excellent e-mag, I have gotta have one on my turbo diesel car. The problem is my car has mechanical injection, so it doesn’t have a throttle potentiometer. Is there another method of sensing the throttle position that can be used to signal to the Delta Throttle unit that I am coming off the gas, thus opening the BOV? Could I perhaps fit a micro-switch to the car's throttle lever?

Please help as I’ve gotta have that psssssssttttt noise on my car! Keep up the good work on the mag.

Andy Birch

A simple 2-position switch won’t work because the DTT looks at the rate of throttle movement – not throttle position. You can, however, fit an OE throttle position sensor, feed it the appropriate regulated voltage and then take the signal from it.

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