Grail Engine - A Critical Look
A non-marketing driven inspection of the Grail Engine technology and problems likely
associated with it
By: Bruce Bahlmann - Contributing Author (your
is important to us!)
Created: April 4, 2012
Recently, I read with great interest a story about the promising
qualities of the Grail Engine as explained in an online how to article (how
does the grail engine work). In fact, I was so taken by some of the
concepts of this engine that I went on to read more about it on the
grail engine company website.
This article represents a collection of my thoughts and reactions as I read about
the Grail Engine with a sprinkle of my life long fascination with the combustion
engine for good measure - the aim here is to provide a non-marketing focused
interpretation of this technology.
"Promising" benefits of the Grail Engine
The Grail Engine leverages a number of innovative technologies (I will
discuss later) to achieve
sizeable horsepower, torque, fuel economy, and fuel diversity - all within a
very compact space that requires little (if any) cooling that normal 4
stroke engines of similar horsepower and torque require. Below are the
from various sources on the Internet detailing the current working prototype as well as larger versions of the Grail
Engine that are
currently being engineered.
||65 ft lbs (@1,500 rpm)
||180 ft lbs (@? rpm)
||? (@? rpm)
||? (@? rpm)
||? (@? rpm)
||? (@? rpm)
Of particular interest in the above is the surprising amount of torque at
what appears to be a low (1,500) rpm.
Reached for Comment
I did reach out to the company in an attempt to verify the information I
found about the various engine versions on the Internet (this was how I
completed the chart above), however when the company called me back they
simply stated, "We are in phase three of the process of building our
proprietary engine and do not divulge such information as torque, etc." In
response, I proceeded to tell them "Actually, you have some information on
your website and that other sources have quoted you as giving out some of this
information in the past. So, why not share it with me?" The company response
to this statement was simply, "This is not the case and that we do not give
out that information." So, rather than argue with the guy, I just told them
"Perhaps you need to review your website because some of this information is
definitely in there." It was a brief exchange, but I cannot help but feel
disappointed with how this was handled. Who are these guys and why would they
get so defensive? Probably a topic for another article or for someone else to
further investigate the company - my sense is that something is definitely
The Grail Engine claims to not rely on a single breakthrough technology
rather simply combines the use of several "proven" innovations to achieve
these significantly compact performance figures. These technologies include:
Direct Injection provides up to 50% fuel savings
over traditional carburetor engines.
|This technology involves spraying fuel directly into the firing
chamber as opposed to using a traditional carburetor which mixes
fuel with incoming air. Fuel injection is commonly used in cars
today however it is not directly injected into the cylinder.
Forced Induction provides up to 40% fuel savings
over non-supercharged engines.
|This technology involves using the engine's exhaust to spin a
turbine which in turn spins another turbine to collect and focus
large amounts of fresh air to be sent into the engine. Forced
Induction is less commonly used (due to its associated costs) but
can be found on high performance vehicles (sports cars, luxury
|Homogeneous Charge Compression Ignition (HCCI)
HCCI provides up to a 15% fuel savings over
traditional spark plug ignition while meeting current emission
|This technology involves compressing fuel air mixture to the point
it combusts. HCCI closely resembles the ignition process that occurs
in diesel engines. The Grail Engine uses a variant of this where
instead of compressing to the point of ignition, it compresses
"nearly" to the point of ignition and then fires three spark plugs
to more completely burn the compressed fuel air mixture.
Achilles Heel of the Grail Engine
What I believe is the Achilles Heel of the Grail Engine is its
innovative use of a valve atop the piston (this is NOT common among modern
day engines) which is uniquely shown via an animation provided by the company. In this
animation, the valve atop the piston opens at the start of the upward
compression (pre-combustion) stroke to allow fresh air previously compressed
(pre-heated) below the cylinder (during the previous power stroke) to enter the combustion chamber to replace the exhaust
which is vented out the valve atop of the cylinder head that is opened and closed just prior to
the piston valve opening.
The top of the piston is typically a combustion battleground, where
unused combustibles (artifacts) wind up and adhere to its surface (see
example figures of a traditional piston after extensive use). While the
Grail Engine probably does perform quite well when everything is new (most
engines do), the Grail Engine would exceedingly become sensitive to the
natural build up of combustible artifacts that will not only severely impact
its efficiency, but also can lead to malfunction (such as blow-by which is
caused when a combustion chamber is improperly sealed by its rings and the resulting
combustion is able to forcibly enter the crank case) and or a much shortened
Traditional (non-Grail) engines all use pistons, but their valves are
placed atop the header (the top of the engine). While nothing prevents a
traditional 4 stroke engine from placing an intake valve atop its pistons,
the placement of the valve atop the header has advantages - particularly
since gravity pulls artifacts from the combustion down onto the piston (thus
away from the sensitive valves). As a result, traditional valves would likely require
less maintenance than the Grail Engine.
Also, the pistons used in traditional (non-Grail) engines have a
fairly thick non-critical surface that combustion can push against, the
Grail Engine has the framework of a piston with a valve in the center which
is extremely critical to its operation. The ability for this valve atop the
piston in the Grail Engine to not only resist combustion artifacts, but also
properly seal, and perform flawlessly, creates a crutch on which the whole
Grail Engine leans on to properly operate. When (if) this crutch (piston top valve)
malfunctions, the whole engine fails.
What I don't like about this aspect of the Grail Engine is the following:
- The piston top valve represents a moving part which is part of another
moving part - odds say this would be the first to fail
- "When" the piston top valve fails, since it is placed all the way
inside the engine, a complete overhaul is in order - very expensive to
- While bringing fresh air into the crank case would provide unique
cooling opportunities, pre-compression, and pre-heating, it also
places extreme requirements on the quality of the air entering the engine
as any impurities found in the air would find their way into the crankcase
and impact the lubrication effectiveness of the oil there - there is a
reason why traditional engines keep the crank case separate from the
combustion chamber as well as free flowing air. This brings up another point, if the crankcase oil,
cylinder walls, and main bearings are exposed to a constant flow of
this probably demands a specialized oil that can withstand constant
exposure to air and humidity and or contaminants within the air - humidity
being a monumental challenge to solve in my opinion.
- Finally, utilizing the power stroke to compress and preheat the air
below the piston sounds like a good idea, but it also robs some of the
energy of the power stroke. Also, with regards to larger versions of the
Grail Engine, such compression likely places increased demands on the
starter (particularly cold starts).
After all this time spent reading about this Grail Engine, I went back
and reread the article that started me down this path (the How To article
referred to earlier in this article) which, oddly enough, is linked to from
the company website. What is odd about the article, is that there is a error
in the way they describe the engine that has be incorrect, but the company
must endorse it because they have linked to it. I'll be happy to edit this
article and add the name of the person who can identify the incorrect
statement - I know there is at least one.
While the Grail Engine shows some promising engine efficiencies, car
makers are well on their way in utilizing improvements on the technologies
mentioned within this article to achieve similar if not better and more
reliable results. For example Transonic Supercritical (TSCi) Fuel Injection
could be used to with very little changes to modern engines to achieve
better fuel efficiency than modern hybrids.
I hope all of you who read this article find my critique of this
technology useful and interesting. I welcome your thoughts and comments.
The following are other articles I found about the Grail Engine. I did
not check those too for accuracy, but have provided them as additional
|Can Birds-Eye.Net help you or your Company?
Receive your Birds-Eye.Net articles and white
papers hot off
the presses by adding our RSS feed to your reader.
(C) Copyright Birds-Eye.Net, All rights reserved.
It is against the law to reproduce this content or any portion of it in any form without the explicit written permission of Birds-Eye Network Services, LLC. Federal copyright law (17 USC 504) makes it illegal, punishable with fines up to $100,000 per violation plus attorney's fees.