Response

More on HPV?

I have enjoyed the series "Building a Human Powered Vehicle" very much. I am wondering however, will there be a Part 7, or some form of summary?

Brian Hanson
United States

Sorry for the delay in the series. We’ve been doing some interesting things with the machine, including data-logging suspension travel and measuring seat vertical accelerations. There will be at least two more parts to the series, with the next part scheduled to appear in about four weeks. To see a sneak preview of the machine in action, have a look at www.youtube.com and www.youtube.com .

Upsizing MAF Flow

One of my friends mentioned that you converted a Toyota air flow meter to increase the size of the air inlet.  I have a GTR and was wondering if you think it is possible to carry out a similar modification? I have HKS turbos, and most people seem to just get 300ZX Bosch units (at $350 not cheap!). I liked what you did in building the 4WD controller for the GTR! Great to see people actually trying things for themselves and not just buying things off the shelf!

Daniel
Australia

Our airflow meter bypass was done on a Nissan – series starts at Airflow Meter Bypass, Part 1.

Auto Air Off

Re: Driving Emotion. “I didn’t feel a huge lack of power (although I did switch off the air when overtaking)........” I am surprised that you haven’t fitted a ‘switch’ to turn off the AC in these situations.

Craig Dunn
Australia

We intend covering such a system using the Voltage Switch kit.

Space for Speakers

I was just reading your Driving Emotion from December in regards to speaker size issues. I have experienced this issue in a few small cars. My solution would be to try Akai speakers. They have a very shallow mounting depth and are very lightweight; the only drawback I have found is that the quality is not as great as some of the better aftermarket speakers.

Stephen Mason
Australia

Finding Stuff

I consider AutoSpeed to be the most useful car mag that I have ever read in the past 45 years (back to when I was still wearing short trousers to school even in the middle of winter). I have been able to top up on my, somewhat, out of date degree in automotive engineering and visit areas of the theory and practise that I might never have even considered.

However, I find it quite time consuming trawling the back issues to find articles for research to help me with my projects. Is it at all possible that you have kept a database and could incorporate an A-Z index of all previous content?

Best wishes from a cold and rain soaked South Coast of England, but never mind I ain't the usual 'Whinging Pom' even if we did lose the Bl**dy cricket again and Summer’s only 5 months away.

William Keightley
United Kingdom

Thanks for the positives. We don’t have an index of articles so the easiest way of finding relevant material is to use the search function using a variety of terms.

Measuring Intake Systems

Re: Negative Boost Revisited, Part 4.

Firstly, good quantifiable research in the recent articles, as always!

It may be too late, however in the original intake configuration, I note you tested at 5000 rpm in 2nd gear (high load).  I don't recall if you've had the vehicle run up on a dyno yet?  Is 5000 rpm the rpm for peak torque? I expect having driven an EF in the past that the torque band is rather flat and wide, and across mid-range revs, trailing off towards 5-6K rpm.

What about taking an additional set of measurements at the peak torque RPM, on the standard intake? Or even say 1500, 3000, 4500 rpm? Or on the dyno!

As you're well aware, intake systems on production vehicles are a compromise on many fronts, performance, noise at full throttle opening, cost, and consideration of the 'normal' operating rev range.

I would expect that the plumbing and bell-mouth etc are designed to approach peak efficiency around the middle of the rev range (or perhaps the torque peak area) to try to give the best all-round experience for general driving - so by testing at 5000rpm you may be on the fringe of the area that Ford focused on during development! In which case yes, you could likely make significant gains, however will you be affecting the mid range and thus general driving? Without a before and after, will you know - apart from the seat-of- pants dyno?

As you noted there is also a chamber on the intake pipes close to the throttle, presumably a resonant cavity based on Helmholtz principles.  It may be for noise reduction or even to help provide reduced pressure oscillations between intake valve opening times at a given airflow, thus improving volumetric efficiency at those load points.

One of your own articles talked about S2000 exhaust system comparisons -  if I recall correctly most reduced mid range torque+power to produce a higher torque+power output later in the rev range!  Fine for a race car driven at 10/10ths, not so good for the quick overtake in traffic!

Anyway, just suggesting some more research on that front would help satisfy my curiosity!

Brett Kofoed
Australia

By definition, peak cylinder filling per intake stroke occurs at peak torque - that’s what makes it peak torque! However, peak airflow occurs at peak power, and that’s when the greatest flow losses in an intake system will be measured. A torque loss anywhere in the rev range results in a power loss at those same rpm, so dyno sheets will clearly show if this has occurred. Pressure drop measurement will not show the tuned behaviour of the intake system. So for all of these reasons, intake manifold pressure drop measurement should be done at peak power (or at revs near peak power).

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