Question for Walter Atkinson

Hi Walter,

I watched with great interest all of the threads on lean of peak operation and also some concerns with electronic ignitions over the last couple of years. On several threads you have indicated that the electronic ignitions and their mapping should be a concern in regards to peak pressures in the cylinders. You indicated that the existing elec ign manufacturers don't have data on what is happening to intracylinder pressures with their various systems. The folks at GAMI talked about the PRISM system and monitoring the peak IC pressures. I have been holding off on deciding on elect. ign. for the 8 I am building, in the hopes that there would be progress on PRISM. Do you have any thoughts on when this system will become available or any guess as to costs? At OSH 2006 I talked with someone at the GAMI booth and asked when it would be available and they said within a year. Any info or thoughts you could add regarding this topic would be appreciated!


Thanks in advance,

Last time I spoke to them

They told me in the order of 8 grand.

Frank 7a

WHOA!!!

If that is the case, too rich for my blood!

If I'm not mistaken, the whole goal of the PRISM system will be full EI and EFI eventually. A true FADEC. And it's going to be CERTIFIED which is why the high price tag.

We've supplied a handful of FADECs over the last 13 years to Lycoming and Continental owners plus hundreds more for auto engine powered aircraft. The systems have racked up over 30,000 flight hours to date.

New flight testing on O-320s should begin soon and a complete conversion kit may be in the works. This system is user programmable but we hope to develop baseline mapping for most standard O-320 configurations to reduce programming time for clients. Work is being done both here in Calgary and California on this concept. We anticipate total kit costs below $4K. We will be at Reno this year, helping out with a Sport Class entry using SDS on a Conti 550 twin turbo as well.

Two current SDS users with Lycomings have accumulated just over 1000 flight hours and one has run LOP for the whole time with good results.

The PRISM concept with chamber pressure sensing is similar to what has been used by several auto makers for some time now and is really the cat's meow as this saves much of the considerable test/ dyno time required to map ignition curves over many MAP/ RPM/ AFR combinations. Power to GAMI if they get this to work well at a reasonable price. Cool technology.

Of course its better, the salesman said so

jim said:

Hi Walter,

I watched with great interest all of the threads on lean of peak operation and also some concerns with electronic ignitions over the last couple of years. On several threads you have indicated that the electronic ignitions and their mapping should be a concern in regards to peak pressures in the cylinders. You indicated that the existing elec ign manufacturers don't have data on what is happening to intracylinder pressures with their various systems. The folks at GAMI talked about the PRISM system and monitoring the peak IC pressures. I have been holding off on deciding on elect. ign. for the 8 I am building, in the hopes that there would be progress on PRISM. Do you have any thoughts on when this system will become available or any guess as to costs? At OSH 2006 I talked with someone at the GAMI booth and asked when it would be available and they said within a year. Any info or thoughts you could add regarding this topic would be appreciated!


Thanks in advance,

Click to expand...

If you are flying a big twin Cessna, say with IO-550 contenental's, that can eat fuel like crazy (60 gal/hr total), I can see something like the PRISM might earn its keep, especially if you fly 500 hours a year. However the cost I guess will be out of sight.

Second Walter, God bless, his buddies are the folks developing it and selling it. The fact it's measuring ICP (instantaneous cylinder pressure) may be the ultimate in engine parameters, but it's going to add 4 more expensive probes.

Where do ICP probs go? Good question. It ain't easy. You need a pressure transducer that goes in the combustion chamber. The common way is a custom modified spark plug or adaptor. There is no other way unless you drill another hole into the cylinder as far as I know.

We have had air-cooled aricraft engines, basically with the same technology we have today since the 1930's and 1940's. The small Lyc and Continental's came out in the 50's and 60's based on the earlier radials. So over 60 years with out ICP or PRISM. Heck in the 80's and 90's, even today most planes on the ramp are lucky to have a single CHT and may be a EGT if lucky. We have flown with out all this stuff for a long time. Than again gas was a buck n half.

Walter has thrown out aspersions on EI and cast doubt on their safety. I really dislike fear mongering; the terrorist win if you don't buy a PRISM. He's backup data for making those claims is we have secret info that only we know and can't share! Well gee that is fine, but there has been very positive service experience the last 15 years with EI on Lycs in experimentals. The experience in the field with the PRISM..... Zero. I can't allow folks to throw out comments like that, saying something is dangerous without proving it, for one it affects me. So I researched it and there is no proof to support Walters claim, sorry. Unless he shares his secret info all we have to go on is almost two decades of experience. Same with internally regulated alternator's, people who sell the opposite type say they are dangerous. Hog wash.

It is so simple, when below 75% power, which is easy to accurately estimate with RPM/MAP, despite what Walter says, you can start to lean and advance ignition. Now if you have a big IO550 engine, you can save gas by leaning at higher power in climb. Why? Well those engines are sucking 26-30 gal/hr, times two for a twin. Early and aggressive leaning, even in climb right after takeoff can save a lot with a big engine. With RV's we can start to lean a little at 5,000 feet by "feel", but it's full rich till than. SO WHAT! We climb at over 2000 fpm initially. Getting to 5,000 feet altitude is less than 5 minutes, so its not like we are going to save much gas. Again small 4 cyl engine, low utilization per year and not going to the poor house buying probes, you really don't need them. Ignition can only get so good and do so much.

The current EI's for experimental aircraft gives 2% to 6% increased efficiency, say 4% nominal, lower fuel burn, plus a little more power as well. How much better could the PRISM be, 1/2% or 1% more? Is it worth it. If you have a Cessna 421 with two IO-550's flying 500 hours a year, may be. However a little 4-banger RV sport plane you fly 100 to 150 hours tops per year? Not so much a value added thing. The ironic part is we fly faster and climb quicker than those Bonanza drivers, he, he, he.

A RV with a O-320 carb, wood prop, day VFR only and one CHT is all you need. More gauges and stuff will not make much difference in performance, econ or fun. Keep your RV-8 light and simple. It will be less maintenance, easier to maintain (with less probes to trouble shoot) and feel better on the stick because it's light.

Jim, if you want an EI hold off, but I recommend a Lightspeed III. One unit and a magneto is fine, but dual units sync'ed will give you even more performance. Also I recommend STOCK compression. EI will work with higher compression pistons (the have a advance mapping that is less aggressive), that is not the reason I prefer stock compression. I am just not a fan of the HC pistons for several reasons: Hartzell has not tested their prop for that engine mod, there is much great experience with EI with stock compression and 100LL gas may be hard to get in the future. With 8.7 to 1 or less you will be able to run the new 95UL. There are EI and very high compression running just fine, but indeed you have to use full rich much more. It's a racing choice not a choice for a daily flyer in my opinion.

Several auto OEMs use the spark plugs with a small current across the electrodes to measure ionization characteristics and the combustion process. Very neat idea as no separate pressure transducer is required. Delphi in particular has done a lot with this technology.

As I mentioned before, the advantage of this technology is that fact that you don't need to run hours of dyno testing on dozens of different engines which should reduce system costs for the end user. By being able to plot pressure rise, spark timing in particular can be optimized for many different piston and chamber shapes, compression ratios and fuels.

If we were just concentrating on one engine, say an O-320 with 8 to 1 pistons running on 100LL, it would not be too bad to develop a near optimal spark curve through testing using a system like ours, when you talk about modified engines with all sorts of different upper end parts and operating on mogas and 100LL, the permutations and combinations become staggering to test.

FADECs are good for lazy pilots or they can reduce workloads substantially. They can do a better job than the pilot when properly programmed, especially in the taxi, climb and descent phases of flight which is where we find most of the fuel burn advantages.

It is not easy to guess at optimal ignition timing on many different engine types at various MAP/ RPM combinations especially with non-programmable systems like most aircraft EIs on the market. Unless the system has been tested ON YOUR ENGINE COMBO, either on a dyno, test stand with club or in flight, most manufacturers are guessing and must/ should be erring on the conservative side, especially if they are covering many different models of engines. This is the same idea as in the performance auto world where "one chip fits all". This only works well on one engine combo with specific parts.

I applaud GAMI for going down this road and wish them well but wait to see several thousand hours of flight time on their systems. In this business, as others have learned, the proof is in the pudding and theory can be relatively meaningless.

I agree 100% (its true)

rv6ejguy said:

It is not easy to guess at optimal ignition timing on many different engine types at various MAP/ RPM combinations especially with non-programmable systems like most aircraft EIs on the market. Unless the system has been tested either on a dyno, test stand with club or in flight, most manufacturers are guessing and must/ should be erring on the conservative side, especially if they are covering many different models of engines.

I applaud GAMI for going down this road and wish them well but wait to see several thousand hours of flight time on their systems. In this business, as others have learned, the proof is in the pudding and theory can be relatively meaningless.

Click to expand...

Totally agree 100%. But you can estimate a mapping and its not impossible. It may not be ideal but it will be safe.

I agree its a beautiful thing and wish them much luck with the PRISM, but we are not their main market. They may want us to buy them and flight test them before they certify them, but they want Bonanza guys. When a Beech sells for in 2007 prices $500,000.00 to 3/4th of a million, a $9,000 ignition does not sound too bad. (I have no idea what it would sell for or if they will get it to market).

I did not know that! Neat technology, current thru plug, ionization, computer to analysis and so on. How did we live with out it. So this stuff is on the family sedan? I knew they had knock sensors but not ICP measurements. Another thing to turn the check engine light on.

Yes, George, I think their market will concentrate on Lycoming 540 and Continental 550 types first 'cause that's where the big bucks are needed to pay for all this technology and where fuel savings are the greatest. Designing the hardware and writing the code to do this along with validation, testing and certification does not come cheap and probably puts this out of budget range for most RV 4 banger types.

None of the other certified FADECs are cheap either- which is where we come in.

I think this ion sensing technology has been around for 7-8 years and was first used by Saab. Bosch, Siemens Deka and Delphi have been offering coils and ECUs with this technology for a while. Those automotive guys are pretty clever!

Sometimes sophistication breeds problems and the more code you have simply becomes a nightmare to debug. With some automotive ECUs running millions of lines of code now, we see problems landing in the customer's laps. BMW has had some serious problems along these lines as have other OEMs. For aircraft, maybe keeping it simple and just do the basic job is safer and cheaper. We can run the engine just fine on less than 6K lines of code. Not only that, I see many electronic systems like GPS, EMSs etc. so complicated now that the end user can't figure out how to use all those "features". Granted, a certified FADEC should run behind the scenes without owner input but we have seen here with other microprocessor based devices what happens when code fails to execute properly or poorly designed hardware fails. Mayday, Mayday.

For further info on this ion stuff, SAE paper 980166 covers the topic and

http://www.fs.isy.liu.se/~larer/Projects/main.html nine years old now so it is not a new idea

http://delphi.com/manufacturers/auto/powertrain/gas/ignsys/ionized/

I like playing with the nobs. If the machine just took care of itself, I would get far less enjoyment out of flying.

Well big of you to admit it

JonJay said:

I like playing with the nobs. If the machine just took care of itself, I would get far less enjoyment out of flying.

Click to expand...

A lot of people like playing with their nobs but never seen any one admit it on a public forum. Yea the older I get, the more old school I get and grumble at the "new finagled stuff". When I was younger, peach fuzz on my chest (now ape like), I thought I'd never get like those old timers; now I have one foot firmly in the grumpy old man camp, but I'll never get tired of playing with my knobs....mixture and throttle and prop of course.

Reliability

Ok guys, enough about your knobs.......but it's not just about fiddling, it's knowing that a steel cable is connected to a brass butterfly valve and that it is ALWAYS going to do what you ask. No worries about software incompatibilities, sensor failures, bad terminal crimps, electrical system failures........just good old-fashioned reliabiliy.

The reason our hair is grey George is because we've seen how often this electrical stuff fails, and we are not going to pay for the privilidge on our days off.