[Diy_efi] RE: Timing and dyno pulls

Grant Beaty gbeaty at ufl.edu
Mon Dec 23 17:34:06 GMT 2002


So higher cooling system temp helps heat transfer from coolant -> radiator
as well as engine -> coolant? I thought only the latter was true.

Grant Beaty

----- Original Message -----
From: "M. Claywell" <clay0052 at umn.edu>
To: <diy_efi at diy-efi.org>; <diy_efi at diy-efi.org>
Sent: Monday, December 23, 2002 2:02 AM
Subject: Re: [Diy_efi] RE: Timing and dyno pulls


> 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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>
>
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