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Old 08-19-2022, 07:07 AM
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Default A carburetor IS a computer

From time to time I see (and participate in) good natured jousting between old school and new school hot rodders regarding the pros and cons of carburetors and electronic fuel injection (EFI). My sense is that some EFI proponents see them as more efficient and less mysterious than that carburetor they once had that they could never get to run right. Carburetors are also seen as primitive and unsophisticated by some. . . So I'd like to set the record straight by noting that carburetors ARE computers, and they can do much (but not all) of what EFI can do with a less complex system.

In today's world most people assume the word "computer" refers only to an electronic digital computer. But well before digital computers there were analog computers. An analog computer is defined as:
A type of computer that uses the continuous variation aspect of physical phenomena such as electrical, mechanical, or hydraulic quantities (analog signals) to model the problem being solved. In contrast, digital computers represent varying quantities symbolically and by discrete values of both time and amplitude (digital signals).
I was first introduced to an analog computer during engineering school back in the 1960s. It was a maze of electronic tubes, resistors, capacitors, etc. connected to an oscilloscope. By turning the dial on any of several variable resistors, the scope would produce any of an infinite number of wave forms. And that is one of two advantages an analog computer has over a digital computer.

The first advantage is that while a digital computer with sufficient memory can consider a huge number of possible inputs and outputs, the number for an analog computer is infinite. The second advantage is that an analog computer reacts to unintended inputs with whatever output it is configured to produce, while a digital computer will simply stop processing or enter its error routine. This means an analog computer (like a carburetor) can respond to a less that ideal input (e.g., the wrong size jet) with a less than optimum but still workable output.

So, am I saying that carburetors are "better" than EFI? No. I'm saying that both systems involve computers receiving inputs and producing outputs. Both are complex and the added complexity of the EFI system allows it to do a better job of tuning in real time - provided ALL of its systems are functioning correctly. But carburetors have their advantages too, including operating under less than ideal conditions. And they are not as mysterious as some think they are.
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Old 08-19-2022, 01:47 PM
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Excellent points, Tommy.

In a peak hp contest a properly tuned carburetted engine will give up little if anything to a properly tuned EFI engine. Where the injected engine will pick up an edge is in the various part throttle driveability metrics.

Because the carburetor relies on air bleeds, emulsion tubes, power valves and main jets to deliver the proper fueling over the engine's operating rpm range it provides an OK and sometimes even good fuel delivery performance. The EFI engine, which is continually monitoring the exhaust oxygen content in a closed loop fashion and in MAF based systems the pounds of air being consumed, the EFI system has the ability to immediately modify the fuel delivery to match the air available to the engine.

The net net bottom line of the contimuous process monitoring is a much closer to commanded (presumably correct) fuel dellilvery than the carburetted engine across the engine operating range. Where guys like us get flummoxed is in all the additional controls provided to deliver that fuel volume with a high level of precision and repeatability even in wildly changing atmospheric conditions.

EFI tuning is not that difficult and while better done on a dyno, it can be easily done on the street with an extra set of hands. As luck would have it, to produce 100 HP an engine, any engine, needs to process 10 lbs of air per minute. At what is referred to as Standard Temperature and Pressure (STP) air weighs 0.0765 lbs per cubic foot.

That means 1 pound of air, at STP, will be equal to 13.1 cubic feet of air. Now to make 100 Hp the engine will need to process (consume) 131 cubic feet of air per minute. If we have a 600 Hp engine it wll need to consume 131 * 6 or 784 cubic feet of air every minute.

When you consume 784 lbs of air and you are fueling to an AFR of 14.7:1 for Plain Jane gasoline you will need a little over 53 lbs of gasoline per minute. At 6.5 lbs/gallon (in round numbers) that means a fuel delivery demand of a little over 8 gallons per minute! Changes in air density require modificatins to that fuel delivery in real time. This is where the EFI systems shine.

An over 8 GPM consumption behavior is cruising fuel consumption at a 600 HP power level. If you are accelerating you will need to drop your AFR down to somewhere in the low to mid 11's (about 0.75 lambda) for max safe power. That will drive your fuel consumption up to a little north of 8 gallons per minute.

The transitions between different driving models is usually a complex problem with a comparable solution process. EFI systems are digital computers with sensors to tell the software program what is happening. The program along with your commanded fueling, air density metrics and injector flow characteristics determine when and how long to keep the injectors open to delivery the engine's required fuel.

A carb accomplishes essentially the same function but not quite as accurately because it does not have a closed loop feed back system like an EFI system. As a result the delivered fuel is 'in the ball park' but not exact.

Can you notice the difference in daily driving? The answer is yes if the fueling misss is big enough and usually but not always no if you are in the ball park. Most guys driving with carbs do not notice the difference unless the weather changes or there is an adequate whoops in the power valve or air bleeds or emulsion tubes or jetting.

These whoops are usually cumulative and except for some of the newer Holley and Holley like carburetors emulsion tubes and air bleeds are not changeable but main jets and powervalves are so there can be a correction possible and available — it just cannot dynamically change with the air.

With the EFI systems the correction capabilities are significant and can be overwhelming in number until you get familiarized. Once you are familiar with the location and naming conventions for the fueling variables your ability to tune is substantially increased.
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Old 08-19-2022, 05:04 PM
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This makes my head hurt?
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Old 08-19-2022, 05:35 PM
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when will the next genius come out with the new fuel distributor that will use both systems thats what I what to know.
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Old 08-19-2022, 06:24 PM
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Makes no sense. At 8GPM, no Cobra on the planet can be driven for more than about 4 to 5 minutes... Are you sure its not Gallons Per Hour (the standard rating on fuel injectors).
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Old 08-19-2022, 07:17 PM
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Old 08-20-2022, 04:32 AM
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That means 1 pound of air, at STP, will be equal to 13.1 cubic feet of air. Now to make 100 Hp the engine will need to process (consume) 131 cubic feet of air per minute. If we have a 600 Hp engine it wll need to consume 131 * 6 or 784 cubic feet of air every minute.

When you consume 784 lbs of air and you are fueling to an AFR of 14.7:1 for Plain Jane gasoline you will need a little over 53 lbs of gasoline per minute. At 6.5 lbs/gallon (in round numbers) that means a fuel delivery demand of a little over 8 gallons per minute! Changes in air density require modificatins to that fuel delivery in real time. This is where the EFI systems shine.


Your calcs are a bit out - using a BSFC 0.50 lbs/hr a 600hp motor will consume:
600 X 0.5 /6.25 = 48 Gals per hr - not 8 Gals per minute.

Otherwise I like your take on things.
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Old 08-20-2022, 02:01 PM
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I've been considering EFI for quite some time, looking at both throttle body and multi-point systems. As such, I've been talking to people with direct personal experience, watching forums and Facebook groups, etc. to get a sense of what works and what doesn't.

While the auto industry has used and proven EFI for decades, it seems to me the after-market industry still has a long way to go before it consistently and reliably provides an alternative to 'modern' carburetors.

I realize those with EFI systems that are running well aren't spending their time shouting their successes from the rooftops, but there are a lot of disgruntled users out there with sometimes huge problems.

I can wrap my head around the high probability that most of the FiTech or Sniper issues are due to flawed installations, exhaust leaks, etc., but I hear far too much about failed ECUs, oxygen sensors, long delivery times for replacement parts, poor customer service, yada, yada, yada.

I'll keep watching the industry to see if the situation improves but, for now, I'm going to stand pat and stick with my Holley Street Avenger.

Please, no lengthy dissertations to explain how my observations and opinions are incorrect.
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Old 08-20-2022, 03:54 PM
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Regarding the state of the aftermarket EFI offerings, I confess I haven't looked seriously at them for several years. When I did look about five years ago, I was surprised by the ready availability of "factory refurbished" units. I had to wonder why the manufacturer had so many returns they could carry a large stock of refurbished units. The most likely reasons (faulty components and high difficulty of installation) caused me to drop them from consideration.
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Old 08-21-2022, 02:45 PM
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Quote:
Originally Posted by Snake2998 View Post
That means 1 pound of air, at STP, will be equal to 13.1 cubic feet of air. Now to make 100 Hp the engine will need to process (consume) 131 cubic feet of air per minute. If we have a 600 Hp engine it wll need to consume 131 * 6 or 784 cubic feet of air every minute.

When you consume 784 lbs of air and you are fueling to an AFR of 14.7:1 for Plain Jane gasoline you will need a little over 53 lbs of gasoline per minute. At 6.5 lbs/gallon (in round numbers) that means a fuel delivery demand of a little over 8 gallons per minute! Changes in air density require modificatins to that fuel delivery in real time. This is where the EFI systems shine.


Your calcs are a bit out - using a BSFC 0.50 lbs/hr a 600hp motor will consume:
600 X 0.5 /6.25 = 48 Gals per hr - not 8 Gals per minute.

Otherwise I like your take on things.

Snake2998’s commentary was spot on when he identified the gasoline consumption as over the top!

As luck would have it, I experienced a high-level spousal interrupt during my original post-authoring phase. When I returned from my mandated honey-do, I assigned the numeric volume of air consumed as if it was the weight of air consumed. The weight was not 784 lbs; the volume was 784 cubic feet, which weighs 59.98 lbs, not 784 lbs. With correct math, the numbers play out as follows;

784 cubic feet of air weighs 60.0 lbs. (784 * 0.0765). A cruising AFR of 14.7:1 would require 4.1 lbs of gas to meet stoichiometry. (I also missed a digit in my gasoline weight representation. Regular Pump gas is reported as 6.25 lbs per gallon by the department of energy and Snake2998 — it was a tough day!). A weight per gallon of 6.25 lbs would equate to 0.66 gallons of gasoline per minute (4.1/6.25), not the 8 gallons per minute I originally represented.

These numbers bring the BSFC to my 0.41 value above. [(Gals/hr)*(Gas Den)/HP]. The 0.41 value assumes, among other things, complete combustion and minimal energy spent to operate the actual engine mechanism. When you factor in combustion efficiency, volumetric, and mechanical efficiencies (or lack thereof for all), a 0.5 BSFC is not an unreasonable expectation. Most significantly, Snake2998’s intuition and quick analysis was spot on! — Thanks for the heads up and clear thinking Snake.


P.S. A similar tip of the hat and thanks should also go to Tony for his early detection of my whoops
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Old 08-21-2022, 03:39 PM
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Quote:
Originally Posted by cycleguy55 View Post
I've been considering EFI for quite some time, looking at both throttle body and multi-point systems. As such, I've been talking to people with direct personal experience, watching forums and Facebook groups, etc. to get a sense of what works and what doesn't.

While the auto industry has used and proven EFI for decades, it seems to me the after-market industry still has a long way to go before it consistently and reliably provides an alternative to 'modern' carburetors.

I realize those with EFI systems that are running well aren't spending their time shouting their successes from the rooftops, but there are a lot of disgruntled users out there with sometimes huge problems.

I can wrap my head around the high probability that most of the FiTech or Sniper issues are due to flawed installations, exhaust leaks, etc., but I hear far too much about failed ECUs, oxygen sensors, long delivery times for replacement parts, poor customer service, yada, yada, yada.

I'll keep watching the industry to see if the situation improves but, for now, I'm going to stand pat and stick with my Holley Street Avenger.

Please, no lengthy dissertations to explain how my observations and opinions are incorrect.
The sweet taste of apparent low cost, apparent simplicity and visual similarity to a carb system we are already familiar with fades as the buyer attemptes to gain functionality he thinks ought to be present in his system only to find it is not.

Easily the best fully featured system available right now is the MS3Pro Plug and Play systems available from DIY Auto Tune <=clickable. Pick any one of the three Ford PnP systems they have to offer and you will not be disappointed! They are the poor man's Haltech, Motec and you don't need $8-10 thousand. They are actually affordable!

They plug right into an OEM Ford wiring harness and use OEM Ford Sensors. Buy the Harness from Ford where they are still available or scrounge one out of a salvage yard and you are good to go. The 03/04 SVT Cobra unit comes with an excellent base tune that delivered somewhere around 440 HP out of a stock O3 Cobra.

The DIY AutoTune route is easily the shortest way home from both a price and installation point of view. The ECU comes with absolutely excellent tuning software and data logging software. When you are on their site check out the list of features the EFI provides, it is stunning!

This is a video of the install in an 03 Cobra, click here => MS3Pro Install The video is 7:45 minutes and the install is really as simple as it looks.

Here is the DIYAutoTune first start Video, First Start Video The video is 10:51 minutes.

Here is another install video including first start, Malcolm Install The story plays out exactly the same.

You can easily get snookered with half steps and throttle body this and somehting else that sort of installs. This stuff just works right out of the box! It gives you access to every tuning variable but does not require you to use the more sophisticated stuff unless you want to. It is for sure the short way home and there is lots of YourTube video support along with an active user community on their website.

Check out the Vids, you will not be disappointed!

BTW the EFI unit allows you to plug in your engine displacement in liters or cubic inches and will work for any sized engine and any firing order. Injector sizing is also fully customizeable, high impedance, low impedance, low flow rates up to multi thousand cc's per injector flow rates.

This stuff is the short way home for real.



Quote:
Originally Posted by Tommy View Post
Regarding the state of the aftermarket EFI offerings, I confess I haven't looked seriously at them for several years. When I did look about five years ago, I was surprised by the ready availability of "factory refurbished" units. I had to wonder why the manufacturer had so many returns they could carry a large stock of refurbished units. The most likely reasons (faulty components and high difficulty of installation) caused me to drop them from consideration.
You and I think very similarily Tommy. If the units are reliable where did all the cores come from for rebuilds?

If you are considering EFI check out the MS3Pro stuff I was yacking about above. It works no matter what size or power level the engine, supports nitrous, supports, turbos, supports superchargers, flex fuel the list just goes on and on.
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Last edited by eschaider; 08-22-2022 at 09:33 AM.. Reason: Spelling & Grammar
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Old 08-21-2022, 06:59 PM
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Quote:
Originally Posted by eschaider View Post
The sweet taste of apparent low cost, apparent simplicity and visual similarity to a carb system we are already familiar with fades as the buyer attemptes to gain functionality he thinks ought to be present in his system only to find it is not.

Easily the best fully featured system available right now is the MS3Pro Plug and Play systems available from DIY Auto Tune <=clickable. Pick any one of the three Ford PnP systems they have to offer and you will not be disappointed! They are the pooor man's Haltech, Motec and you don't need $8-10 thousand. They are actually affordable!

They plug right into an OEM Ford wiring harness and use OEM Ford Sensors. BBuy the Harness from Ford where they are still available or scrounge one out of a salvage yard and you are good to go. The 03/04 SVT Cobra unit comes with an excellent base tune that delivered somewhere around 440 HP out of a stock O3 Cobra.

The DIY AutoTune route is easily the shortest way home from both a price and installation point of view. The ECU comes with absolutely excellent tuning software and data logging software. When you are on their site check out the list of features the EFI provides, it is stunning.

This is a video of the install in an 03 Cobra, click here => MS3Pro Install The video is 7:45 minutes and the install is really as simple as it looks.

Here is the DIYAutoTune first start Video, First Start Video The video is 10:51 minutes.

Here is another install video including first start, Malcolm Install The story plays out exactly the same.

You can easily get snookered with half steps and throttle body this and someting else that sort of installs. This stuff just works right out of the box! It gives you access to every tuning variable but does not require you to use the more sophisticated stuff unless you want to. It is for sure the short way home and there is lots of YourTube video support along with an active user community on their website.

Check out the Vids, you will bnot be disappointed!

BTW the EFI unnit allows you to plug in your rngine displacement in liters or cubic inches and will work for any sized engine. Injector sizing is also fully customizeable, high impedance, low impedance, low flow rates up to multi thousand cc's per injector flow rates.

This stuff is the short way home.





You and I think very similarily Tommy. If the units are reliable where did all the cores come from for rebuilds?

If you are considering EFI check out the MS3Pro stuff I was yacking about above. It works no matter what size or power level the engine, supports nitrous, supports, turbos, supports superchargers, flex fuel the list just goes on and on.
They seem to be targeting the late 90s+ Mustang engines. Will they work on a 60's FE or Windsor?
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Old 08-21-2022, 07:34 PM
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Quote:
Originally Posted by twobjshelbys View Post
They seem to be targeting the late 90s+ Mustang engines. Will they work on a 60's FE or Windsor?
Absolutely, Tony!

In the Engine and Sequential settings pop-down window, you can specify the engine size in cc's. I have attached a screenshot of the section at the end of this post. You go to the Engine Size field and enter the engine size in cc's. Get the appropriate Mustang wiring harness out of either Ford (if it is still available) or a salvage yard if it is not. Wire up your engine, and you are 98% done.

The MS3Pro does not care what year, size, number of cylinders, firing order, or fuel you choose to run. It is all configurable through easy-to-find menus. That little blue box with a question mark in it takes you to a three-line explanation of the field you are in. An excellent manual comes with the system that covers more than you will ever use in the EFI System and manages to do it in conversational English, so it is understandable.

Check out the videos, download the manual off their site. This is a universal EFI system that can even run a Wankel! I think you will be impressed.
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