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#Post#: 2568--------------------------------------------------
Re: Bugatti Type 37 Build - engine cooling
By: StefanN Date: July 2, 2020, 9:10 am
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Given the engine has a fan, I’ve built a shroud around the inlet
and then will feed cold air in. The idea is that a positive
pressure of cold air is better than recirculating hot air.
Will it work?
#Post#: 2569--------------------------------------------------
Re: Bugatti Type 37 Build
By: chrisenamels Date: July 2, 2020, 9:24 am
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Yes it'll allow you to draw cooler air from outside the engine
compartment, but the cross sectional area of the inlet needs to
be more than the total area of the intake slots in the fan
shroud. If it isn'y you'll restrict your airflow, and to some
extent negate the advantage of cooler air.
#Post#: 2570--------------------------------------------------
Re: Bugatti Type 37 Build
By: StefanN Date: July 3, 2020, 3:11 am
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[quote author=Chris Brown link=topic=3.msg2569#msg2569
date=1593699865]
Yes it'll allow you to draw cooler air from outside the engine
compartment, but the cross sectional area of the inlet needs to
be more than the total area of the intake slots in the fan
shroud. If it isn'y you'll restrict your airflow, and to some
extent negate the advantage of cooler air.
[/quote]
I was wondering about that Chris. The first thing I noticed is
that the fan, which is supposed to pull air in the centre and
then accelerate it out to the edge, has "inlet" slots exposing
the fan blades along quite a bit of the radius - which
presumably then spills air? Wrt cross sectional area, I'm
working on the basis that one large inlet is much more efficient
from a flow perspective than lots of turbulent, lossy narrow
slots....but the new inlet size is a complete guess...errr
experiment! Time will tell. Hopefully I'll get to run the
engine again in the next few days and will get a feel for it
then.
#Post#: 2572--------------------------------------------------
Re: Bugatti Type 37 Build
By: chrisenamels Date: July 3, 2020, 4:58 am
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Just as well I've got ahead of myself by buying engines! I've
just checked, and as I thought the fan is within the shroud
area, so all the slots in the pull start housing are inlet. The
inlet to your cool air feed needs to be more than the total area
of all those slots.
Feeding cool air in should not only improve engine cooling, but
also the temperature of the air exiting the shroud should be
lower, reducing the heat build up. As Rhys points out though
letting the hot air out is just as important, and as it's volume
is greater a larger cross sectional area of vents is needed.
When I build an enclosed kart I'll do some experiments on heat
extraction, the Morgan is a different proposition as the engine
and exhaust will not be enclosed by the body.
#Post#: 2573--------------------------------------------------
Re: Bugatti Type 37 Build
By: RhysN Date: July 3, 2020, 7:02 am
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Quite a bit of the airflow is directed across the cylinder head
fins by the fan. I believe that most of those slots in the
housing are to draw air in. It might be interesting to do some
testing on a running engine to check, smoke a a method? I don't
have one running right now or I would try that this afternoon.
It would be a good exercise for those with video skills (Hint :)
)
#Post#: 2574--------------------------------------------------
Re: Bugatti Type 37 Build
By: chrisenamels Date: July 3, 2020, 8:05 am
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I think you'll find all of the slots draw air in, they all feed
into the suction side of the fan. I've got a digital
differential manometer which I can bring with me when I can next
get to a gathering. That'll allow approximate airflow
measurements to be taken on both inlet and outlet sides.
#Post#: 2579--------------------------------------------------
Re: Bugatti Type 37 Build - remote choke
By: StefanN Date: July 6, 2020, 4:46 am
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I wanted to make a remote choke for the Mikuni carb. I
experimented with using a cable pull to the existing lever, but
didn't like the way it looked.
So, I drilled a 2mm hole down the middle of the shaft of the
plunger and then an exit hole for the wire. A blob of solder on
the end stops it coming back out. I then drilled a bit of brass
5.3mm to take the end of the sleeve of the cable. At the other
end I drilled it so it could fit over the shoulder on the end of
the original brass nut and soldered these together. Seems to
work. Adjustment will have to be at the lever end of the cable.
Would have been even simpler to make a new piece to replace the
original nut but couldn't figure out what thread it was so went
this route.
#Post#: 2624--------------------------------------------------
Re: Bugatti Type 37 Build
By: StefanN Date: July 17, 2020, 2:24 pm
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I finally managed to fit the smaller tyres to try on the
Bugatti. 3.25 down to 2.5 should make for an interesting
comparison.
#Post#: 2625--------------------------------------------------
Re: Bugatti Type 37 Build
By: RhysN Date: July 18, 2020, 1:41 am
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Stefan, have you changed all 4? Are they the same make as
previously? It will be interesting to see what differences you
feel.
I have noted that the guys in the US now talk about different
makes and versions of tyres, grip vs wear and such, so perhaps a
straight size swap may give other knowledge.
#Post#: 2626--------------------------------------------------
Re: Bugatti Type 37 Build
By: StefanN Date: July 18, 2020, 3:00 am
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[quote author=RhysN link=topic=3.msg2625#msg2625
date=1595054460]
Stefan, have you changed all 4? Are they the same make as
previously? It will be interesting to see what differences you
feel.[/quote]
No I’ve only changed the rears so far. That’s partly cost but
also because I always scuff up the rim when changing tyres.
Also, I’m still working on weight distribution and understeer,
so for the purposes of this test, keeping the weight and contact
at the front will mean I’m not changing too many things at the
same time. It’ll probably look odd and will change the angle
the ck is sitting at a bit .... hmmm that’ll give me more
caster!
As you say, will be interesting to feel the difference.
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