[Diy_efi] RE: Timing and dyno pulls

[Dave Dahlgren]

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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