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 I have been able to top up on my, somewhat, out of date degree in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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