34:1 Afr?!

[MAP]

Greetings,

I have to admit I wasn't expecting such an inundation of excellent responses. It's a privilege for a simple hobbyist such as myself, to be able to come here and interact with such a knowledgeable, connected group. Thank you.

On to specific points:

1.) A number of acronyms were shared here that I don't understand. A quick definition for the following would be most appreciated: "COP's", plus "ITB" and "PICO" injectors.

2.) David - thank you for your comments. With gas approaching $4/gal, I think the business argument for "wide-bandwidth" carb's and EFI, which might entail increased design complexity and production cost, becomes very different. Case in point: ten years ago, I told myself that putting a $3k EFI system on my motor didn't make sense, because at $1.20/gal gas, the difference in economy would take about ten years to amortize. Today, that's coming down to about three years, and if we now factor-in the further potential gains of a very lean-burn condition, then maybe the amortization period could be brought down to just a shade over two years!

My point is, if I could now justify a $3K EFI system based on an economy-savings amortization schedule, then what does that imply for carburetor manufacturers? (Of course, I believe the answer is, "plenty." But, that's if, and only if, they can deliver the lean-burn goods along with the WOT performance we take for granted from carburetors.)

3.) Devious - fascinating response. My interpretation of your comments is that, just as for a carburetor, an EFI system that would work over an unusually wide bandwidth would likely need to get more expensive as well. Even so, if AFR's into the 20's and even 30's are seen as desirable, then quite possibly we're beyond a range that even the most perfected mechanical carburetor could attain?

Or have we re-opened the case for throttle-body injection as an intermediate solution in terms of efficacy of operation as well as price? (I remember, for example, how you, David, spoke well of Holley's "mile-a-dial" carburetor back in the day.)

Interesting comments about the Latham supercharger - I'll check out that web site.

Devious, about the reference in the article to Exxon, I have no idea. My apologies. On edit: I've sent the author of the cited article an e-mail inviting him to comment here.

4.) Automotivebreath - I'm not sure I understood everything you said, but the parts I understood were very interesting indeed. Thank you.

Best regards,
Mark

[CREW CHIEF]

Originally Posted by MAP

Greetings again,

I thought this would work better as a separate post rather than a cumbersome edit to the opening one.

Question: in trying to improve economy, I contacted a few carburetor manufacturers and tuners a few months ago about trying to get 17:1 AFR in cruise. To the very last one, they grumbled that lean surge and tip-in stumble would be the bane of such an attempt.

Do I presume correctly that fuel-injection (the Mass-Flow vendor on this site comes to mind, for instance,) is the ticket out of these difficulties, by artful adjustment of the fuel and ignition maps? Or is that a speed-density (MAP sensor) system trick only? And can any single injector handle the very broad range of duty cycle that would be required, to provide the very lean allotment of fuel at cruise, while being able to support full output at WOT and high rpm? In combination with gearing and chassis refinements, and now reading about the possible benefits of very lean AFR's, I'm wondering whether 460 hp peak from a 383 SBC, with 30mpg cruising at 60mph, is out of the question. (I count myself very fortunate indeed in that there are no emissions requirements where I live.)

Best,
Mark

I have been asked many times by street/pro-street this same question because they all want great gas mileage when thay are cruising.
With a carb there is almost no way to go from a 17:1 A.F.R. rating at cruise to 12.8 : 1 or a 12.5 under-boost or nitrous application at W.O.T.
The transistion is just to great.

[MrWOT]

Originally Posted by MAP

1.) A number of acronyms were shared here that I don't understand. A quick definition for the following would be most appreciated: "COP's", plus "ITB" and "PICO" injectors.

Coil On Plug

Individual Throttle Body

and I assume the last one is piezoelectric injectors? though I've never heard them referred to as "pico"

[MAP]

Thanks Mr. WOT for the acronym decryptions. Piezoelectric actuators make sense where one wants high force, high efficiency, but small displacement. They present a capacitive load to the drive source, which may or may not be problematic. Overall, however, the first items sound like a reasonable recipe of attributes for a fuel injector.

Crew chief, I see your point. But although I'm a simple hobbyist when it comes to cars, my career is in engineering, where I have a reputation for a very agressive approach toward dealing with situations where people (including engineers) tell me, "that can't be done." Most of my designs, in fact, arose from situations where engineer colleagues told me that what I wanted to do was impossible. Now, billions of dollars of corporate income later, I rarely hear that comment...

And so I ask the question here, "what prevents me from having the best of both worlds (i.e., cruising economy with unhindered WOT performance,) from the same fuel delivery and ignition systems?" Until it can be absolutely proven from first physical principles that something can't be done, I don't give up.

Thanks,
Mark

[automotivebreath]

Mark,
Perhaps it would help if I were to explain some of my points.

The gas fired turbine engine example relies on lean burn to reduce emissions. Yet
in Bill’s post he explains “The biggest problem with lean burn in modern engines is
emissions control. Until recently, it just wasn't practically possible to reduce NOx to
acceptable levels except by running near stoichiometry.”

So if we were to look at the difference between the two engines perhaps we can
identify areas for improvement in the SI engine to accomplish similar results as
achieved with the turbine.

First your example uses spark ignition, the turbine does not. This is one of the
concerns with a lean burn SI engine. The solution being “long spark duration”.

In addition, with the turbine steps are taken to assure the mixture is completely
homogeneous. The SI engine is considered to use a homogeneous mixture, in the
cylinder this is far from true. Where the overall mixture may be considered to be
some specific ratio, in the cylinder lean areas, rich areas and regions with high
levels of residual will exist. "If the mixture passing through the plug gap at the
point of ignition does not contain enough fuel to support combustion, the resulting
misfire will result in the drive ability issues (lean surge and tip-in stumble) and high
HC emissions." Part of the solution is high levels of in-cylinder mixture motion
along with very effective use of available squish areas.

Lastly the turbine uses natural gas and hydrogen as fuel; your example uses liquid
gasoline. This offers several challenges; the gasoline must be vaporized before
burning and hydrogen has very high flammability. Solutions, earlier Pinhead talked
about hydrogen enrichment, not a bad idea. And the best fuel delivery system avalable
along with engine heat to prepare the fuel for combustion.

[Devious]

This topic is near and dear to my heart.
I believe that the average racer and hobbiest can benefit from leaner burning (more efficient) engines that will allow them to go further and faster than they are currently running. And that leaner running at cruise can allow good mileage on high performance engines without detracting from transient engine response. A win-win situation for everyone.

On otherwise optimized engines, this is going to take improved atomization from injectors (or possibly carbs) over a wide range of engine demands, combined with good ignition systems that are able to light off the leaner air/fuel mixes.



The Magneti Marelli Pico injectors are a type of compact (very short), top feed injector (like the ones used on high performance motorcycles) that have good atomization and are rated for operation at pressures up to 10 bar (145 psi).
http://motorsport.magnetimarelli.com...WPR_rev5.0.pdf

These injectors can offer improved atomization at the same fuel pressures compared to Bosch or Bosch-type injectors, or even the small diameter "pencil" injectors like the excellent Deka units. At higher pressures, they perform even better. When used in stages, multiple injectors per cylinder can allow smaller flowing injectors to be used at higher fuel pressures for very good atomization over a wide range of engine speeds. Many of the newer performance bikes use just such staged systems, as well as several systems on Corvettes. The compact Pico designs also lend themselves to better being able to fit multiple injectors to intake systems where space and location are issues.



As for long duration (inductive) spark being the answer for lean burn, several studies would show that this is not necessarily the case. It would seem that high output, short duration CDI (capacitive discharge ignition) systems have shown very good results at lean air fuel ratios when used with coil per plug systems (not necessarily COP). In fact, the CEI system mentioned in the article above is CDI.

My personal experience with high output, single strike, CDI (such as Motec's CDI-8 or M&W's Pro-14) has shown that when used with the correct coils, about 3 degrees less advance can be used in conjunction with AFR's about .2-.4 of a ratio leaner for best power and torque. In several cases, cruise AFR's leaner than 14.7 have been used without lean hesitation on rapid throttle tip in. Below peak torque rpm, and otherwise optimized engine can pick up a couple percent more torque by the simple addition of a good CDI system with optimized tuning. Idle improves, and the engine sounds noticeably different and more crisp.

I am just a dedicated hobbiest, perhaps others have seem similar or different results.

I would assume that Nitro2 might have a good bit of information and data on this topic... as to whether or not he is able share it is another issue.

[CREW CHIEF]

Originally Posted by MAP

Thanks Mr. WOT for the acronym decryptions. Piezoelectric actuators make sense where one wants high force, high efficiency, but small displacement. They present a capacitive load to the drive source, which may or may not be problematic. Overall, however, the first items sound like a reasonable recipe of attributes for a fuel injector.

Crew chief, I see your point. But although I'm a simple hobbyist when it comes to cars, my career is in engineering, where I have a reputation for a very agressive approach toward dealing with situations where people (including engineers) tell me, "that can't be done." Most of my designs, in fact, arose from situations where engineer colleagues told me that what I wanted to do was impossible. Now, billions of dollars of corporate income later, I rarely hear that comment...

And so I ask the question here, "what prevents me from having the best of both worlds (i.e., cruising economy with unhindered WOT performance,) from the same fuel delivery and ignition systems?" Until it can be absolutely proven from first physical principles that something can't be done, I don't give up.

Thanks,
Mark

I have used many after-market carbs. over the years.
On any of the high-dollar engine builds we have been using Pro Systems carbs.
Patrick at Pro Systems is one of the best carb. guys I have ever ran across.
For the street/strip cars AED or Quick Fuel are O.K.
I do like you attitude.
Do or die.

[Devious]

Originally Posted by MAP

My point is, if I could now justify a $3K EFI system based on an economy-savings amortization schedule, then what does that imply for carburetor manufacturers? (Of course, I believe the answer is, "plenty." But, that's if, and only if, they can deliver the lean-burn goods along with the WOT performance we take for granted from carburetors.)

3.) Devious - ...My interpretation of your comments is that, just as for a carburetor, an EFI system that would work over an unusually wide bandwidth would likely need to get more expensive as well. Even so, if AFR's into the 20's and even 30's are seen as desirable, then quite possibly we're beyond a range that even the most perfected mechanical carburetor could attain?

Or have we re-opened the case for throttle-body injection as an intermediate solution in terms of efficacy of operation as well as price?

Best regards,
Mark

Mark,
While I am (by far) no carburetion expert, and it is fact that some carb designs atomize fuel better than many EFI systems, I believe that EFI can do things that many current carb designs simply cannot - especially four-barrel designs. However, a larger version of the Keihin FCR (or similar carbs) on an individual runner manifold might get the job done very well. But the cost may be prohibitive.

I also feel that a V8 using throttle body or port injection on an intake manifold designed for carburetion is giving up a lot of the potential that EFI offers, in trade for simplicity and compact design.

Compared to a carb manifold with throttle body injectors, a port injected sequential injection system can offer considerably improved part throttle performance and mileage potential. The cost to go full sequential port injection does not have to be more than that of a throttle body system - especially if you can fabricate a few parts yourself. However it will cost more than a good carbureted system with the same peak power numbers. But, IMHO, there is more to performance than peak horsepower numbers.

A related story:
A friend swapped a 302 Ford into a Mazda Miata a couple of years ago. The engine was a later model 5.0L EFI engine that was converted to a dual plane intake and Holley carb for ease of initial installation. He later added aftermarket aluminum heads and cam. He now wants to rebuild the short block (possibly a 331 stroker) but he is currently not happy with the performance nor mileage. He considered installing a performance aftermarket Ford EFI system or Weber individual runner carb set up... until he researched the cost of such systems. He and I are currently working on a cheaper alternative.

After we considered his desires for performance against his budget, we considered many options. He really liked the idea of an individual runner EFI system and ended up talking me into donating some time to build/terminate the wiring harness and a bit of welding. After researching the throttle diameters and flow required, my friend located two motorcycle throttle bodies (four butterflies each) with injectors, harnesses, fuel rails, and throttle position sensors at a cycle salvage with very low miles. These cost him right around $175-185 each. We are currently building an intake manifold from sheet and tube to mount the throttle bodies, and have sent the injectors out to be cleaned, flowed, and matched. He will still need to fabricate a throttle linkage or cable connecting the two throttle bodies, add velocity stacks of appropriate length, and air filters.

He considered using an ECU from a modern factory V8 engine, but the sensor compatability issue was a concern, so he has ordered an aftermarket engine management system from Link EMS (linkecu.com) in New Zealand that can drive 8-16 injectors (8 sequentially or 16 in batch pairs) and 8 coils, and works well with the mismatched sensors - for around US $1500-1600 plus shipping (if I remember correctly). So for around $2000-$2200 total cost (and some fabrication work) he will have a fully sequential, individual runner EFI system that should give good power, good mileage, and great throttle response. At a later date he can use the same ECU and much (if not all) of the rest of the parts on another engine if he chooses, which (with the improved performance and mileage) helped him to justify the cost compared to the current carb and manifold he is running. This system will also offer a custom appearance that he wants - which is a big deal to some, like my friend.

Granted, this is a relatively low performance engine compared to some, but likely more than he needs for the 2500 pound vehicle on the street with some track use - road track and 1/4 mile.

I have completely wandered off topic, but I hope this answered a few questions.

[MAP]

Greetings,

More excellent food for thought! I'm under a crunch for time for what will probably be the rest of the day, but for now, I just wanted to share that Dr. Michael Ward of CEI may well join this discussion before very long, and that he sent the following information (moderator: please advise if what I'm posting here goes beyond simple sharing of information, to promotion or marketing. Thank you.)

Best,
Mark

[automotivebreath]

Imagine what this picture would look like if the plug were
indexed 90 degrees clockwise.