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No Such Thing

It's a great thing that all these years later, we are still reading AutoSpeed! Big cheers.

Mate, can I bone pick for a moment? I notice in many articles the mention of 'roller bearing turbos'. The latest being the Cappuccino article (see Coffee Kick). To the best of my knowledge, there is no such thing as a roller bearing turbo. I could be wrong, but I don't think so Roller bearings would just have too much drag, I would think. I have never seen any exploded views of anything other than ball bearing cartridges. It is just one of those things that irks me, and perpetuates a myth.

Peter de Vries


Yes it’s a mistake that a few years ago we realised we were making – and, we thought, stopped doing so! However the (repeated) Suzuki article slipped through – it’s now fixed.

12 Valve Heads

Just wondering if you have enough resources for an article on 12v heads?

We have come a long way since the torqueless wonder in terms of 4v Tech but there are vast arguments that the 2v head has better down low performance than 4v heads until higer rpms are reached. The polyquad head theory is a valid one on combining swirl and tumble And several companies have incorporated 12v heads at some stage and even bringing them back seems to be happening. The one in particular that interests me was the renault/pug douvrin head only release at the end of the end of the 505 and other french cars. It had two un-equal sized inlet valves, one big exhaust and a strategically place sparkplug. It was a cheaply cast head and suffered reliability issues unfortunately.

Some dyno sheets Ive come across on 12v engines through past emails years ago have showed torque curves that were fatter than 4v equivalents or versions. One particular tuner had a datsun 1200 race car with the ka24e and ka24de fitted one after another and mentioned the 12v was much more responsive and driveable. The article you did a while back of the Pintara shows the ka24e motor has very low compression and wonder if a high comp version of the 12v would have ever challenged the ka24de and other nissan twin cam engines of the time.

Either way Im also interested in the Mazda, honda, ren/pug, Merc, Ford, mitsubishi, nissan and other after market 3v heads for chev smallblocks.

I feel the 12v have merit for everyday cars that need torque and better swirl/tumble designs without complicated inlet manifolding. Even honda went back to 8v with twin spark plugs. I also suspect that the 12v vs 16v argument is similar to the log vs equal length turbo manifold designs where log is better below 5k (which is where most of the driving is done) and equal over 5k.

Theoretically a well designed 12v with unequal length inlet valves on large exhaust inline with the smaller inlet valve to prevent overlap or mixture escaping and the larger inlet valve facing the sparkplug seems to be the best design exc. chamber shape and biased porting.

Hopefully with your experience and research avenues you can shed more light on the 12v head as a probable solution for some tuners searching for an overlooked low to mid range solution?



We don’t have any plans for such an article.

Air 150 Trike

hello there. 1st, you guys put out absolute real quality reading! Its technical intelligent and far from boring. What i like to call highly tangible reading.

I wanted to know more about the Air 150 trike (see Air 150 Recumbent Trike, Part 1), namely contact information for where i could potentially buy one, I did a quick search online and was unable to find any information. If you could let me know anything regards this, i will be happy to know



The Air 150 recumbent trike is not being produced commercially. The best known commercial recumbent trikes in Australia are made by Greenspeed, but they do not make a full suspension machine.

Lexus 400h

I read your Lexus RX400h test and thought you might enjoy where the Lexus 400h showed up in USA auto sales in January 2009 in the USA: I was surprised to find the 400h was the top selling, Lexus hybrid in January.

Bob Wilson

United States

Raising the Back of the Bonnet

Regarding Matt Allen's letter about raising the back of the bonnet to improve engine cooling: I tried this on my 1987 300zx and monitored the results with both underbonnet thermometers and wool tufts to see where the air was flowing.

The results were that at very low speeds and stationary, the air came out of the now present gap, and radiator temperature might (or might not) have been very slightly lower. At higher speeds (say above 30 km/h) air flows backwards, down into the gap. This probably reduced flow through the radiator, but definitely cooled the rear and top of the engine bay. Recorded temperatures were 10 degrees lower in similar conditions, dropping from 80 to 70 degrees.

So it depends on what part of your engine bay you want improved airflow in.



Intelligent Intercooler Water Spray

i am construction the intellegent intercooler water spray to cool my pajero 4d56t. i have made the circuit with no real issues and found apon testing the unit is designed to turn on or off the pump as required using logic from boost/throttle position and intercooler temp. i also noted the circuit for the 12/24v motor controller and decided to buy a kit and tie these circuits together. i now have a fully functional intellegent intercooler water sprayer that has a progressive pump/water feed.

the system is working perfectly and having independent trigger systems i can have the intercooler circuit just comming on to trigger the pump controler on min speed but the pump controler will increase the flow as i accelerate to max flow on full open throttle . i am building in a failsafe that is a temp sensor that will feed the pump controler 5v if the intercooler temp is realy excessive. thanks guys for a great web site and for the circuit information. Just have to get the nozzles and i can install the units and test on road.

Martin Stone


A Few Things Amiss

Re: The X7 Road Rocket

A few things seem amiss in this story.

1. Stated output from a tuned LS1 5.7 was 246 rwhp. Most pull around 300 rwhp easily with a tune, it's been done thousands of times as can be checked on (including mine). So the Brock "special" was pretty poor at 221 rwhp! Maybe the exhaust he has doesn't help.

2. Out running a GSXR-1100 ? Must have been a very high speed run (although they will do around 180 mph), they do 0-100 in around 2.9 sec versus the claimed 4.5 for the featured car. I've owned fast cars (featured by you in the past) and bikes and I wouldn't fancy the chances of any high powered car against a big bike in a straight line. The ZX9 should do a similar 0-100 as the GSXR so might be aother case of only 1 of the 2 was racing...

Beautiful little car though, would be awesome.

Andrew McKellar


Electric Car Race

Having read articles on building a hpv, you may be interested in the construction of small, simple electric vehicles for one of the few electric car races in the country - the swan tafe EV Challenge. Up to 50 entries including many schools and tafes enter with students building their own electric cars. The design of a simple electric car is an excellent step from a HPV as it develops an understanding of simple DC electric drive systems and frees up contraints associated with pedalling mechanisms – plus is a hell of a lot of fun and good entry level to electric vehicle technology. Vehicle budgets are $1200 max.



Pretensioner Warning

Re: Reshaping Factory Seats

It should also be pointed out that many cars (eg my 1996 Holden Calibra) have a seatbelt tensioning system, which is designed to pull the belt tight in the case of an accident. It was pointed out to me by the wreckers that it was set off with an explosive charge, and should be treated with respect! It was a tube attached to the underside of my seat, that then attached to the seat belt stalk via a cable.

Good article. I was just thinking the other day that the lumbar support in my seat had gone soft...

Paul McVitty


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