[Diy_efi] RE: Timing and dyno pulls

M. Claywell clay0052 at umn.edu
Mon Dec 23 08:55:20 GMT 2002


Hello,

In regards to F1 guys running high water temps (~ 125 Celsius), one of the
main reasons they do it is to reduce aero drag. They are likely down on
power (from what they could make if they ran a lower water temp), but are
also saving on aero drag. The higher temp differential between the air and
water temperature will allow higher heat transfer rate, thus require
smaller radiator, thus lower drag. I think it was two years ago or so, that
the FIA limited the maximum pressure that F1 cars could pressurize their
cooling systems to. I believe it is around 50 psi. Running higher pressures
would allow even higher water temps if they desired, and if it proved
useable, as far as the trade off between aero drag and power goes.

Cheers,
Mark



On 20 Dec 2002, Dave Dahlgren wrote:
> The Beemer I am sure is tuned for emissions and mileage not peak power..
The
> compression ratio is probably a little on the high side for 87 octane as
well
> but that will make for a greater efficiency at part throttle.. Emission
and
> fleet mileage.. They have lots of compromises that race engines never
see. If
> you build an engine with too much compression for the fuel available you
can
> pull timing out at WOT to stay out of trouble but it will never run as
well
> as
> if it had the right fuel. For all you know the BMW might run best on 98
> octane
> that is not available in the USA at the pump.. Easiest test would be to
add
> some
> 103 octane unleaded race gas and see how she goes..
> 
> As far as head temp goes I never suggested a heat riser in the way of
sharp
> edges was ok. It will always be a problem, 40 degrress of coolant temp
will
> not
> make the sharp edge show up though. A long pull on the dyno sure will
though.
> You can not find it in 1 second on a dyno jet though might take about 3
or 4
> seconds under full load..
> 
> If the F1 guys needed to have the engine run cooler do you really think
they
> would say nope can't do it guess we will just be 30 hp down.. Face a
couple
> of
> million to solve the problem is pocket change to them..
> 
> Why not beryllium.. It makes real good valve seats.
> 
> Dave
> 
> William Shurvinton wrote:
> 
> > No: dave's point: Best power is way off detonation in a race engine. My
> > question, why does a modern road car gain 10HP when run on high octane
> (real
> > test, think it was a BMW) when all it has to go on is the knock sensor.
> > Inference: it must be running close to knock all the time.
> > 
> > > > and race cars (F1 in particular) only ran so hot
> > > > because the aero package demanded a limited rad area
> > > > and air flow. Hotter was more efficient.
> > >
> > > With the engine components themselves, you are limited
> > > by how much heat the materials involved can withstand
> > > before weakening.  With highly-stressed engine parts
> > > that are built to JUST withstand the stresses of a
> > > race and be as light as possible, managing temperature
> > > is CRITICAL.  So there are conflicting needs; the need
> > > to keep the engine structurally sound, and the
> > > "desire" to have it as hot as possible in the
> > > combustion chamber.
> > 
> >  I quoted F1 because it is an extreme case. The engines are run at
> > riduculous coolant temps and revs and until recently were billet
> unobtanium.
> > I like beryllium in space apps, but not sure I want it in my car.
However
> > the coolant temp in this case is due to not being able to get the heat
out,
> > not because the engine liked the heat.
> > 
> > _______________________________________________
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> 
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