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Response

Some of this week's Letters to AutoSpeed!

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BMW Blunder

Re The The BMW Six Cylinder Guide...

In this article, you state that "The Si suffix identifies the fitment of D-Jetronic mechanical fuel injection."

In fact, the D-Jetronic (which uses a MAP sensor) was the world's first production electronic fuel injection (1968 VW Type III). Obviously you'd have to verify all this, but I'm pretty sure my memory is correct.

Greg Griffiths
Australia

Our mistake – you’re right. Article corrected.

Providing the Juice for a 5W Luxeon

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Re Luxeon Lights... Will the phone charger based power supply be able to drive a heatsink-equipped 5W Luxeon? I need more grunt than the 1W can provide. P.S. LOVE this mag.

Hopson Matthew
Australia

Unfortunately, a 1W Luxeon is the most you’ll be able to supply. Jaycar sells a kit that can drive a 5W Luxeon from a 12V supply – details can be found at Starpower - A Switching Supply For Luxeon Star LEDs

The Correct Tyre Angle?

The article Front Suspension Designs makes the comment “Car tyres work best when they are vertical to the road ie have zero camber.” Doesn't this assume that the tyre itself is rigid when in fact the tyre shape changes dramatically under side and bump loads?

Warren Adams
New Zealand

This statement is based on the references quoted in the article.

Sophisticated LPG Injection

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How about an article or two on how to convert an LS1 to run on LPG using injectors? Parnell has what they call VSI LPG injection but this seems unable to supply enough gas to make LS1 levels of power. I wonder if supplementary injectors (throttle body) would help? The drop-off in the popularity of V8s shows people's concerns for the running costs of big cars with big engines. Those of us stuck with such cars have no doubt been wondering about LPG but there appears to be no well-sorted kit for modern V8s - the kits seem to target the older 5-litre Holden engines, etc. I'd imagine that performance LPG kits might be popular if petrol continues to rise.

Peter Hall
Australia

Yes, it appears LPG systems are poised for another surge in popularity. We are considering doing some articles but for now, an interesting system can be found at http://www.gas-injection.com/lpg-gas-injection-technologies.html under the heading “The GTi System”

Aftermarket Sequential Set-up

Any idea how this works - http://www.turbosmart.com.au/index.php?id=75?

Mark Leerberg
Australia

Wow – that’s impressive. Probably one of the first sequential twin turbo systems developed in the aftermarket. We don’t have any more details but, looking at the engine close-up, it appears the GT25 is constantly fed exhaust gasses from all four cylinders. An external wastegate opens (presumably in the mid-range) to allow the secondary hybrid turbocharger to start spooling. Boost pressure is limited by a second wastegate that vents gasses leading to the secondary turbo. There’s one blow-off valve and we imagine there would be at least one other turbo control valve in the intake system.

Two-Stroke AF Measurement

I'm interested in adapting an air/fuel mixture meter for a racing two-stroke motorcycle. I believe a wideband sensor is required for best indication of oxygen content of the mixture. Do you have information on (a suitable kit for) this use?

Bernie Summers
Australia

We haven’t tried using an AF meter on a 2-stroke. If you can source an oxy sensor that’s happy working on 2-strokes and has an output voltage of 0 – 1V there’s no reason the Mixture Meter can’t be used. Can any readers off suggest a compatible sensor?

Love the HPVs

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Excellent article on HPVs Building a Human-Powered Vehicle, Part 1! My University (University of Central Florida) sends an engineering senior design group to participate in the ASME human powered vehicle challenge and I have been participating with them for the past two years. It is amazing how many different designs you'll see when you tell a bunch of college students to go design and build a bike.

With regards to frame materials, it is also important to take cost and how easy it is to repair your frame. This is especially important if you wish to go touring. And with aluminium, just please be very careful with your geometry and pay attention to where your forces may cause problems - because they will cause problems. Another option for frame material is exhaust tubing – it’s cheap, you can get bends easily and any exhaust shop should be able to weld/bend it. I believe the Bearacuda used 2 inch exhaust piping and has achieved world records. And after a nice powder coat, no one has to know! If you pay enough attention, you can even make a SWB bent from wood - http://www.blids.nl/gallery/PlywoodRecumbentBuildingworkshop2003.

It is also important to look at your frame type - a tadpole design (two wheels in front) is in most cases much more stable then a delta (two wheels in back). And what I find interesting is how weight plays a factor (or appears not to) when it comes to top speed... The current IPHVA world record holder, Diablo II, went a tad over 80 mph (129 km/h) and weighs about 60lbs (27kg)! I loved the article - can't wait until Part Two! Any possibility for a fairing?

Paul Jehlen
USA

Glad you enjoyed it and thanks for the interesting info. There’s more to come on HPVs so stay tuned!

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