Hello All,
I have been lurking now for a few months with only one previous post as I
have only had my GT6 since July. She is now bedded down for the worst of the
British winter and I have had the chance to get to know Triumphs again after
a gap of some 30 years. I have been meaning to contribute for a while but
never got round to it till now, I hope I don't go on too long!
John Mac was talking about Jaguars and the Bentley Mulsanne turbo which
caught my eye as I have recently defected from Jaguars (Only on grounds of
cost, they are lovely cars) and I have done a lot of work for Rolls-Royce on
the Bentley and other cars. They are as John describes, very comfortable,
very large, very quick and very expensive! They are also the only modern car
I know that you have to step UP into ! All this leads back to list matters
via the fact that I am an engineer working for a subcontractor supplying the
electronic control unit for the electrically adjustable shock absorbers on
all Rolls and Bentley cars. (This sometimes involves a lot of high speed
driving on closed test tracks! but I digress) This control unit contains
accelerometers to measure car acceleration and it is possible to use the
acceleration and weight of a car to calculate the actual Horse-power. When
the thread started about measuring HP of a car from the top speed I thought
of using one of my control units to do this but on reflection there is a
much easier way, unfortunately involving a bit of maths. If you measure the
time needed to accelerate between two speeds you can calculate the
acceleration and if you know the car weight you can work out the HP
required. You have to compensate for wind and rolling resistance but that
can be done by measuring the time needed to decelerate between the two same
speeds on the same bit of road when in neutral. This will allow a figure for
HP at the flywheel to be calculated. The two speeds involved must be either
side of the engine speed at which you want your HP reading. I will try to
generate a simple formula and step by step procedure which is applicable to
all our cars. Any body interested please contact me or if of sufficient
interest I will post it to the list.
My car is a 1969 GT6 with about a stage three tune as defined by
Triumphtune. It was done by the PO to a very high standard but I think he
over did it with the camshaft which is a "Sprint 83" spec. The engine is
powerful but only over 4500rpm, for a road car a milder cam would have been
better. I might be able to improve things after I have done some work on the
distributor advance curve which is not optimum. I must be careful as we are
shortly going to lose our leaded fuel.
One interesting point on the car is the fact that instead of using 1.75" SU
HS6 carbs the PO used 1.75" SU HIF6 versions. These seem to have been
dismissed on this list as "emission" carbs with no adjustment and of no use.
I have investigated and as far as I can see they seem to be as good if not
better. They can use the standard needles available for the HS6, they have a
concentric float bowl with a sensible fuel temperature compensation, the
overrun valve built into the throttle butterfly can be easily removed and
soldered up, and they have a mixture adjustment by screwdriver. Finally they
seem to be more plentiful, at least in this country, in good condition from
breakers yards.
All comments welcome,
Peter French
1969 GT6 mkII
peter@pmfrench.free-online.co.uk
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