Smart Plugs Ignition System?

[Dan Cordon]

Again, Javad is right on with his comments. I'll insert some commentary 
as well.

> Ok, granted, the list you just created sounds like an impressive argument, 
> but lets look at them one at a time:
> 
> - Failure - IME, the CIS3 ignition system is incredibly reliable in stock 
> trim, and with reasonable and affordable tuneups ever year or two, there should 
> really never be a problem.  Also, for the approximated cost of the system 
> ($1400?), you could do an awful lot of tuneups.  Fouled plugs have also never been 
> a problem IME.

I'm planning to get rid of the CIS system on one of my cars. But this is 
only because the CIS system  will not meter the fuel correctly at higher 
boost levels. While it can be modified to work, the CIS metering plate 
becomes more restrictive at high boost/flow conditions. For a stock, or 
even moderately modified engine the CIS system will work fine. The CIS 
ignition control is as good (or better) than what you'll find for 
aftermarket systems. If you're fouling plugs, it's likely a symptom of a 
component problem rather than any design flaw from the factory.

> 
> - Leaner Mixtures - Ok, leaner does not mean better MPG or better efficiency. 
>  The point of the Stoichiometric ratio is that it is the point of max. 
> efficiency in the gas 4 stroke engine.  I have read a study recently that showed 
> 15.2:1 was, under certain conditions, more efficient.  With the Stage II 034efi 
> system, I can tune my 80 to run down the freeway at 18:1, but it will actually 
> get worse mileage, thus I tune it right to about 15:1 under part throttle 
> cruising.  Detonation isn't a problem typically unless you're under full load.  
> Now, if the SP system can run your engine at 30:1 a/f at a greater efficiency, 
> then it sounds, as you said, too good to be true, or I don't understand it and 
> I encourage you to research it further.

Smartplugs an ignite high lean mixtures that spark plugs cannot. That 
alone isn't any reason to switch to them. Most of the hyper-lean 
conditions have been run on a CFR engine. This is a single cylinder 
engine with a variable compression ratio (on-the-fly) head. The air, 
oil, and water temperature are precisely controlled at all times. It was 
originally designed to determining octane ratings of fuel, and as such 
can resist periodic and frequent detonation. This is a fantastic, 
forgiving research platform that is good for proving concepts, but is 
*far* from the range of operating conditions engines on our cars see.

Javad is also correct....running lean doesn't necessarily mean better 
fuel economy. Lets look at an example. A NA 2.3l engine running down the 
highway at 2500 rpm and say 1/4 throttle. We'll assume that the air 
entering the engine is at 50% the density (or pressure) of the air 
outside (~0.5 bar on our display). The flow rate of fuel could be 
approximated as:
rpm * displacement per revolution * density of air * air-fuel ratio.
For the stoichiometric 2.3l engine as audi designed it this will be ~ 
1.97 grams of fuel per second. If we look at the same engine and speed, 
with full throttle (ambient density in cylinder) and an air-fuel ratio 
of 30:1, we see that the mass flow rate of fuel is 1.92 grams per second.

While this was produced by a simple, crude model, the main point is that 
there's really no difference in the fuel consumption you'd see running 
extremely lean for cruising.

What the smartplugs *can* do (which is why the auto manufacturers are 
interested) is offer similar performance at normal compression ratios 
(CR of 9-10 that will work for gasoline engines), AND offer a 
detonation-free hyper-lean operation at very high compression ratios (up 
to CR 18 so far with lambda 3.0). To make this useful, the OEM's will 
have to change (real-time) the compression ratio on a few cylinders, 
while dropping the remainder (opening valves and cutting fuel) for 
extended highway cruising. With the high compression ratio and lean 
mixture we are capable of producing enough power for cruise (and 
dragging the extra cylinders along) with half or less of the cylinders 
running. In this situation, there *is* a benefit of significant fuel 
consumption reduction.

But again, this will require an engine with far more capabilities than 
any of our I5's have on them. And you can't go hyper-lean (much past 
22:1) with regular compression ratios w/o detonation.

> 
> Overall, your assesment sound too good to be true, so I encourage you to 
> contact them and verify if your understanding is at all reasonable.
> 
> Looking forward to hearing what they say.

The main reason I wanted to chime in about these is that I know the 
company well. They make money by promoting and selling their product. 
The statements they've made on their site (and promotional literature) 
aren't lies, but they also aren't all realized on a single application. 
ie: for one application they designed it such that it can run leaner, 
for another, increased power w/o detonation, yet another, improved 
ignition reliability..... The smartplugs have done all they're claming, 
but a single application will not see all these benefits.

The inventor does drive around a stock Quad-4 with smartplugs in it, and 
has gotten a *very slight* increase in fuel economy while having decent 
longevity of the catalyst. On the flip side, one of our test engines in 
the lab will only go about 5-15 hours before a plugs dies. Planning on 
taking a day-trip. We'd have to bring along half a dozen igniter cores.

Let me bluntly summarize my feelings about putting these in a NA 
audi.....these will make no perceivable difference on a stock engine, 
and even if I were given a few sets for free, I wouldn't put them in any 
of my NA cars. The Jacobs ignition system is a better 'bang for the 
buck' item than smartplugs, and IMO the Jacobs is a waste of money.

> 
> Javad
> 

In a message dated 2/14/2004 7:04:55 AM Pacific Standard Time,
> duandcc_forums at cox.net writes:
> Less failure points. No ECU and wiring, no distributor, no cap, no rotor, no 
> plug wires, no timing problems, no fouled plugs.

True....less failure points, but the points of failure on the audi are 
quite robust. How often does your ECU, wiring, distributor, cap, rotor, 
and wires fail? They'll likely make it 50-300 thousand miles. I have yet 
to see *any* single smartplug last 50k miles. And "no timing problems" 
is stretching the truth some. Timing is *NOT* discretely controlled. 
They can be optimized in one operating region, but you'll just have to 
live with whatever timing is elsewhere. ie: set timing for good full 
throttle power (w/o detonation) and you have be running 10° too retarded 
at cruising loads. To make things worse, there's virtually no way to 
observe ignition timing. My research engines have modified heads where I 
can take high-speed in-cylinder pressure measurements. We use this to 
measure timing, then and make changes to optimize it. All you'll have to 
optimize timing will be acceleration and detonation.

Live in a cold climate (and can't live w/o spartplugs)....do some 
homework on cold-start with smartplugs.

  Plus as he said you can run a
> MUCH leaner FA mixture (1:30?) with no detonation. Wouldn't you like to dial 
> back the fuel to 1/2 what your using now for long highway trips? yeah, it 
> would cut back on power, but imagine being able to cruise in your Audi 4000q or 
> other NA I5 powered car and get 40 MPG on the highway, then when you get to your 
> desination you crank back up the fuel for full power driving. 

See above. While it *is* possible, you'll have to have a new engine 
designed for your car, and some pretty sophisticated management to go 
with it. If you do the math, I think fuel will have to be somewhere 
around $50/gallon for smartplugs to pay for themselves in fuel savings. 
That is, of course, assuming you don't have to replace the cores very 
often.

I'm sure the
> engineer who spoke up a little while back can explain how timing is done, but it 
> appears that timing is done properly, including advance. 

I can explain this if anyone was interested, but it probably doesn't 
need to be on the list. While the new designs do portray the desired 
trends in ignition timing (advance with speed and retard with load), 
they don't give precise control like an ECU will give. So, while you may 
set the geometry for great part load timing, you may be 5-10° retarded 
from desired timing at full load. This is why I said an aftermarket (or 
even stock CIS with new chip) is likely to yield greater 
performance....you have direct control of the ignition all across the 
board. You don't have that with the smartplugs.
> 
> Dave
> 87.5 CGT
> SE Virginia

I believe that this technology has a lot of potential for improving 
power density, or reducing emissions, or creating flexible fueled 
engines, or better fuel economy, or improving ignition reliability, 
or.....  But it WILL NOT do all these for any one application. I *do 
not* believe that this technology has anything spectacular to offer the 
daily driven, stock configuration vehicle. What it does do (which is why 
it's so amazingly cool) is open up a whole realm of options for engine 
configurations and fuel choices not previously possible with spark plugs.

I hate to sound like I'm "bashing" this technology. I'm actually a HUGE 
supporter of it because its potential to revolutionize engines as we 
know them. But I can't in good conscious recommend anyone purchase these 
as an "upgrade" for their daily use car.

-- 
Dan Cordon
Mechanical Engineer - Engine Research Facility
University of Idaho