Depending on how rich the idle circuit is set in a particular engine will
dictate how acrid the fumes are from the exhaust. When running gasoline,
this setting is particularly critical. The approximate air/fuel ratio for
gasoline is 14.7 to 1. For Methanol, the ratio drops to around 6 ~ 7 to 1.
For Nitromethane the ratio is around 4 to 1. However there are other
critical variables that come into play. Gasoline has a very high latent heat
of combustion. In other words for every ounce or lb. or gallon of gasoline
that you burn, how much energy do you get in return. For Gasoline, this
value is very high, around 120,000 Btu/lb. if I remember correctly (I'm sure
I'll get corrected on these figures but I'm at work and all of my references
are at home) for Methanol it's around 50,000 Btu/lb. and I believe Nitro is
around 80,000 Btu/lb. (again, I'm running from memory at the moment). Here's
where it gets tricky, and where the factors surrounding the proper design of
a FUEL SYSTEM come into play. Gasoline, lb. for lb. creates more energy than
any other fuel, drawbacks are that it's octane ratings are relatively low,
and as the octane rating increases, the burn rate decreases. Methanol
generates considerably less energy lb. for lb., but because of it's air/fuel
ratio requirements, twice as much Methanol is required for a given engine
(right now you're probably thinking 2 lbs of Methanol at 50,000 Btu/lb. =
100,000 Btu vs. 120,000 for 1 lb. of Gasoline is still less energy) however,
since Methanol has an extremely high research octane #, you can compress it
much much more than Gasoline, and still not have predetonation (plus it
burns cooler due to it's low latent heat). For this reason, typical
naturally aspirated Methanol engines are compression ratio limited more by
piston to valve clearance than by Octane #'s. As a result, Injected Alky
motors don't notice an appreciable jump in power over gasoline motors.
However, when a blower is added- VOILA ! Plenty of power can now be
realized. Static compression ratios in supercharged Alky motors are much
higher than for gasoline ( a competition supercharged gas motor- assuming a
good tight blower is used, typically has a compression ratio around 7 ~ 8 to
1, with perhaps 25% OD in the blower. ) An Alky motor is usually around 9~11
to 1 with up to 40% OD (beyond that, all you're really doing is wearing out
the blower and losing power as you generate heat in your intake mixture)
This is also part of the reason why Screw type superchargers are so
successful in FM/D and FM/FC. Effective compression ratios now exceed 25 to
1 when the boost is factored in. Also, jetting is not as crucial when
running methanol. If you're close, you're car will run pretty good. With
Gas, you'll foul plugs at idle, load up the engine, or smoke a piston if
you're even slightly off with your jetting. On Injected engines you'll
notice a main, low speed, and high speed bypass on gas burning motors in an
attempt to more accurately match the fuel curve, whereas in an Alcohol
motor, some guys don't run more than a main bypass, (or pill). The motor
will Idle rich without any severe detriment to the motor, perhaps some
excess oil contamination and watery eyes at the starting line, and a little
rich on the top end, or be right on at high rpms while a little lean in the
midrange. Bypasses help match the fuel curve (or a computer works pretty
killer as I'm sure John will attest) to optimize engine efficiency
throughout the entire rpm range, but aren't super critical, again, Methanol
is much more forgiving (Methanol solves Mysteries!). Plus Methanol is around
$1.30 a gallon versus about $4.00 a gallon for good racing gas (It's
probably more now- it's been a while). Now on to Nitro. Nitro produces a
relatively decent amount of energy per lb. burned, but because of it's
air/fuel requirements approximately 3 times as much Nitro is burned as
gasoline. In doing so, 3 lbs. X 80,000 Btu/lb. nets us 240,000 Btu from
Nitro vs. 120,000 Btu for gasoline (again approximate figures here). This is
where Nitro really makes it's power, and as a result of the fuel demands,
typical fuel pumps are the size of an aircraft starter, and fuel lines look
more like storm drains. For example, the fuel pump that we run on the
AUTODESK A/FD idles at 150 lbs. of pressure and tops out over 300 lbs. of
pressure on a typical pass. And this pump is already outdated and is being
upgraded for the 2000 season. Similar to Methanol, Nitro would be more
forgiving on jetting were it not one fact. As Nitro burns, it releases it's
own Oxygen, this is a key factor that relates to the low air/fuel ratio.
When a gasoline engine runs, the intake charge is a finely atomized mist of
fuel, conversely, a Nitro motor burns an intake charge that is approaching a
pure liquid. Since there is so much liquid fuel in the cylinder, compression
ratios are very low. On the dragster we run about 10.5 to 1 compression-
Injected- no blower. Typical supercharged Nitro Motors run about 5 to 1
compression ratios, and rarely run more than 7 to 1 (assuming 90-100% load).
Here's the problem with Nitro-(besides having to upgrade every part, and it
costs about $19.00 a gallon if you buy it by the drum). If you can't burn
the Nitro in your cylinder (and Nitro burns relatively slow- in fact a Nitro
motor won't run stable over about 7000- 7500 rpm MAX) the cylinder is full
of almost pure liquid, and as you know, you can't compress a liquid, the
result is your cylinder decompresses itself by blowing the motor apart (more
commonly known as Hydraulicing). This is why Nitro is so unforgiving in
reference to jetting. Now that MSD has developed a Magneto that generates 44
amps vs. 4 or 5 amps for a good Vertex or Mallory Supermag, Top Fuel and
A/Fuel cars are making more power than ever, with fewer engine failures.
When running two of them, that's 88 amps of burn, per cylinder- and for the
most part, you're burning whatever is in that combustion chamber. While the
Top Fuel cars are increasing in their "relative" reliability, A/Fuel cars,
don't have the supercharger to press air into the cylinder along with the
Nitro and therefore, are a bit more temperamental. Just as a reference as to
the volumes of fuel burned, we'll burn about 8 gallons of Nitro between the
burnout and a 1/4 mile pass. Chauvon Emmons' # 422 AFMR, prior to it's
encounter with the dyke at Bonneville, running a comparatively conservative
tune-up, would consume about 34 gallons of Nitro on a typical blast down the
long course. At 20 dollars a gallon, I'll let you figure out the fuel bill
for Speedweek on his machine !
Hope this helps !
Darrell Ferguson
BLACK RADON ENGINEERING
# 939 BBFALT
http://my.cybersoup.com/blackradon
> -----Original Message-----
> From: Keith Turk [SMTP:kturk@ala.net]
> Sent: Thursday, November 04, 1999 8:13 AM
> To: dferguso@ebmail.gdeb.com; Land-speed@autox.team.net
> Subject: Re: Methanol Solves Mysteries
>
> My only Problem with Methanol was sitting on the line next to someone
> running it when I was strapped in waiting to go.... I about gagged on the
> fumes...
>
> I think John and Brad were both concerned and it was very distracting
> .....
>
>
> When you get to the line you really need to be thinking about the
> requirements of driving the car and what your game plan is... not choking
> on Methanol....
>
> other then that I agree it's the fuel of choice if you can put up with the
> hassles of running it.... especially in the Turbo mode... it simply allows
> a bunch more boost without the associated detonation problems...
> Keith
> ----------
> > From: dferguso@ebmail.gdeb.com
> > To: Land-speed@autox.team.net
> > Subject: Re: Methanol Solves Mysteries
> > Date: Thursday, November 04, 1999 4:16 AM
> >
> > well, maybe some of the veteran land speed racing gurus can help out
> here,
> > but i think methanol has an equivalent octane of near 140 , and while a
> > gasoline internal combustion engine utilizes an air / fuel ratio ( by
> > weight ) of 14+ to 1, methanol is at around 6 or 7 to 1, and nitro is
> near
> > 1 to 1, so jetting, still critical, becomes less sensitive with the
> latter
> > fuels. but likewise fuel flow demands increase dramatically, especially
> > when nitro is introduced. another quality of methanol is that for a
> given
> > expansive force on the piston during combustion, the net thermal
> component,
> > or heat output , of the methanol is a little less, so the engine tends
> to
> > run cooler yet still makes alot of power. other factors are involved-
> > unfortunately there is no direct correlation between gasoline and
> methanol
> > since they are very different compounds, but the fact that top alky drag
> > racers can run static compression ratios of 12 or 14 to 1 with big 14-71
> hi
> > helix blowers and such with viscious overdrives and go through the
> lights
> > at very high rpm sheds light on why methanol stands as an important fuel
> to
> > racing. dont forget that methanol is somewhat corrosive, so this is a
> > disadvantage which must be weighed against some of the superior
> qualities
> > if your not into draining and flushing your fuel system on a regular
> basis
> > . - doug @ black radon
> >
> >
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