[Diy_efi] The Hunt effect

[Jim Butterfield]

ok, understood... thanks

--- John Gross <jogross3 at hotmail.com> wrote:

> Jim,
>   I apologize, I wasn't too clear about the alcohol
> vs. temp thing.  If you
> take a gasoline engine and convert it over to
> alcohol, it will run cooler,
> typically because the engine is not optimized for
> the alcohol, and therefore
> does not see the full benefits of the heat of
> vaporization differences,
> compression ratio allowances, etc.  What determines
> an engine's cooling
> requirement is power production, plain and simple. 
> If you have a 500 cid V8
> gasoline drag motor with a blower making 1300 hp,
> you have to cool X amount
> of heat.  If you have an alcohol variant of the same
> motor, but for some
> reason (usually tuning), it's only making 1200 hp,
> you have to cool less
> than X amount of heat.  However, if that alcohol
> motor is optimized and is
> now making 1500 hp, you will have to cool more than
> X.
> 
> The reason alcohol dragsters (and it's not uncommon
> is gasoline dragsters
> either) don't run a radiator, or run a small one is
> due to the short
> duration that the engine runs.  It doesn't have much
> time to heat up.  
> 
> But on the blowers, yes they can run larger
> displacement blowers and more
> boost because of the knock resistance of the fuel.
> 
> FWIW, top fuel dragster engines (500 cid, blown big
> blocks running nitro),
> make approximately 7000 hp at the flywheel.  They
> must run roughly a 2:1 AFR
> to burn the nitro (nitro has so much oxygen inside
> the molecule that it can
> combust on it's own internal oxygen...it needs no
> outside oxygen to
> burn...it just doesn't burn well like that  ;-), but
> by about half track,
> the electrodes of the spark plugs have melted away,
> and the engines diesel
> the rest of the way down the track.  That, combined
> with the AFR is the
> reason most top fuel engine failures occur past half
> track.  The engine is
> relying on dieseling at that point, and if a
> cylinder fails to ignite, on
> the next cycle, it will hydrolock on fuel.
> 
> -----Original Message-----
> From: diy_efi-bounces at diy-efi.org
> [mailto:diy_efi-bounces at diy-efi.org] On
> Behalf Of Jim Butterfield
> Sent: Wednesday, October 05, 2005 12:17 PM
> To: diy_efi at diy-efi.org
> Subject: RE: RE: [Diy_efi] The Hunt effect
> 
> Ohhh John, hence the reason alcohol dragsters dont
> run
> a radiator.... because the run cooler temps.... also
> they can run those huge 6-71 12-71 XX-71 blowers on
> top of the big blocks... alcohol runs cooler so less
> knock to kill pistions...
> 
> In our grand prix club, countless guys think just
> dropping a pulley sizeto increase boost is ok, not
> scanning the car for Knock retard, soon there all
> pissed because two of the front three pistions are
> chipping from detnoation... them youngn's just dont
> get it, they think hp is cheap and easy...
> 
> thanks john, your wealth of knowledge is awesome
> 
> jim
> 
> maybe off line you could explian how too much octane
> is a bad thing... guys in the club think 108/113
> octane is better for our little 3800 series II
> engines
> and others say 103 is well enough more is a bad
> thing???
> 
> 
> --- John Gross <jogross3 at hotmail.com> wrote:
> 
> > It takes less air to burn an equivalent amount of
> > fuel, but since an engine
> > is an air pump, it?s typically better to look at
> it
> > from the other
> > direction
.you need more fuel to run the engine at
> > stoich at a given load
> > and given rpm with alcohol.  Methanol has about
> half
> > the AFR of gasoline
> > (6.5 stoich compared to 14.7), but half the
> energy. 
> > Where methanol is able
> > to make its power over gasoline is 2-fold.  First,
> > it has an equivalent
> > octane rating of ~113, so you can run a lot of
> > compression, boost, whatever.
> > Secondly, it absorbs much more heat (almost 4x)
> than
> > gasoline when it
> > evaporates, meaning that it greatly reduces intake
> > air charge temps, making
> > the charge more dense, allowing more mass of air
> and
> > fuel to be inducted.
> > If you look at the intake manifold of an alcohol
> > dragster on a 100 deg F day
> > after it makes a ? mile pass, there?s ice on it. 
> > Long story short, alcohol
> > engines run cooler, are less prone to knock on an
> > equivalent engine compared
> > to gasoline, need more fuel to make the same
> power,
> > BUT, could possibly make
> > more power on the same engine if correctly
> > configured.
> > 
> >  
> > 
> > -----Original Message-----
> > From: diy_efi-bounces at diy-efi.org
> > [mailto:diy_efi-bounces at diy-efi.org] On
> > Behalf Of Jim Butterfield
> > Sent: Tuesday, October 04, 2005 7:32 PM
> > To: diy_efi at diy-efi.org
> > Subject: RE: RE: [Diy_efi] The Hunt effect
> > 
> >  
> > 
> > Hey John ,can I ask the master a question... as
> you
> > said below the alcohol
> > AFR is 9:1 so 1)does this mean it takes less air
> to
> > burn... and 2) given
> > two engines equal, on setup with proper alcohol
> > required fuel delivery, will
> > the ahcohol car get more HP if the pcm/
> electronics
> > were tuned for the
> > alcohol????? if so any guess how much HP
> > imporvment???? How does the alcohol
> > act under a bloan application... heat,
> > detnoation-knock etc....
> > 
> >  
> > 
> > thx
> > 
> > jim
> > 
> > John Gross <jogross3 at hotmail.com> wrote:
> > 
> > I'd have to look at the ratios, but yes, certain
> > additives like ethyl
> > alcohol have an effect on octane ratings. HOWEVER,
> > keep in mind that ANY
> > alcohol will dry out any rubber seals, o-rings,
> etc
> > in a fuel system
> > designed for straight gasoline. Also keep in mind
> > that ethyl alcohol burns
> > at a stoich AFR of 9:1 (it's an oxygenated fuel),
> so
> > if you blend it into
> > gasoline, it will change the required pulse width
> of
> > your injectors to
> > maintain the correct lambda. Also, it will tear up
> > your injectors because
> > they're not designed for alcohol either. That's
> why
> > you can't just run E85
> > in an everyday car. The fuel pump, fuel lines,
> > injectors, o-rings, seals,
> > and even fuel tank liner must be designed to work
> > with alcohol-based fuels.
> > 
> > -----Original Message-----
> > From: diy_efi-bounces at diy-efi.org
> > [mailto:diy_efi-bounces at diy-efi.org] On
> > Behalf Of dalemahan at charter.net
> > Sent: Tuesday, October 04, 2005 4:48 PM
> > To: diy_efi at diy-efi.org
> > Subject: Re: RE: [Diy_efi] The Hunt effect
> > 
> > Hi John,
> > 
> > Ah hah - a chance to ask a real IC engineer about
> > fuel questions!
> 
=== message truncated ===



		
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