fuel injection EFI or SEFI? - Ford Truck Enthusiasts Forums



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fuel injection EFI or SEFI?

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Old 01-23-2005, 05:57 PM
bigtoolracing bigtoolracing is offline
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fuel injection EFI or SEFI?

hey guys i need to know if a 1990 F-150 has sequential fuel injection or multi point injection
thanks Robert
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Old 01-23-2005, 07:01 PM
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Multipoint batch fire - batch 1: 1-4-5-8; batch 2: 2-3-6-7.
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Old 01-23-2005, 09:54 PM
bigtoolracing bigtoolracing is offline
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thanks alot
Robert
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Old 01-25-2005, 07:44 PM
broncoman66 broncoman66 is offline
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You have SEFI, as in each injector injects fuel as a specified time. Some cheap EFI systems, like Chevy's throttle body EFI, just has one or two injectors spraying into what is basically an ordinary carburator intake manifold. They inject all the time, with varying amount according to throttle position ofcourse.
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Old 01-25-2005, 08:39 PM
fefarms fefarms is offline
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In Ford nomenclature, EFI means any form of fuel injection.

MFI means multi-point fuel injection. For an 8 cylinder truck there are 8 fuel injectors, positioned near the intake ports. The intake plenum and runners are "dry", no fuel passes through them. Ford's MFI systems are batch fire, as EPNCSU2006 described. 4 injectors are fired at once, even though the 4 "batched" cylinders are each at different points in their intake-compression-power-exhaust sequencing. This is different than throttle body fuel injection, in which there is just one or two injectors, fuel is injected above the throttle plate, and the intake manifold is "wet". Ford did not make throttle body injection for the 1986-1996 model year range, at least not in any trucks.

SFI or SEFI means sequential (electronic) fuel injection. The injectors are timed to fire at the beginning of the intake stroke, with each cylinder fired individually. The system is otherwise the same as MFI.

SFI is somewhat more efficient at idle and low engine speeds. At higher engine loads, there is very little difference between SFI and MFI, since the injector on time is greater than the duration of the intake stroke regardless of when the injector is fired. For the 1986 to 1996 range Ford used SFI in (most) cars and MFI in (most) trucks. In 1996 and beyond, Ford moved to mostly/exclusively SFI.

One other set of buzzwords is MAP vs. MAF.

MAP stands for Manifold Absolute Pressure. The air flowing through the engine is estimated with pressure, temperature, and RPM sensors and compared to a volumetric efficiency table stored in the computer. The injector on time, and thus the amount of fuel supplied, is computed using the estimate. This is otherwise known as "speed density". The MFI trucks are all MAP sensor driven.

The other way to do it is with a Mass Air Flow sensor. The actual weight of air flowing through the throttle body is computed using a hot wire sensor. The amount of fuel needed is very easily computed by using the desired Air/Fuel ratio and the measured weight of air. Most of the SFI cars are MAF sensor driven.
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Old 01-25-2005, 11:36 PM
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Throttle body EFI? do you mean CEFI? as in Central EFI, as opposed to SEFI/TP or MAFS/TP-EFI?

The "hair wire" of MAFS system is not in the Throttle Body, it's in the mass air orifice housing. Some may be stacked near throttle body, others are nearer filter in induction, or intake ducting.

What's batch fired? Are you referring to Bank Fired, like FoMoCo commercial vehicles? FWIW, CEFI systems are bank fired. That means it has to fire one injector in a CEFI or all the injectors on one bank in a SEFI, before any RAM program changes can happen. These are speed density systems regardless if they're CEFI or SEFI/TP. These are all EEC IV based. This is mid term or early TP/EFI technology, one step above CEFI. Some SEFI/ TP systems are bank fired sequencing. Others are fired in unrestricted sequential
numerical order. But again they're all still Speed Density, EEC IV logic.

The MAFS/TP-EFI systems are numerical sequential Mass Air Logic systems. MAFS/TP can have EEC IV or EEC V logic if you have coil packs it's EEC V, but if you have a TFI distribuitor it's EEC IV logic, usually. MAFS/TP EFI systems use BAP instead of the MAP sensor to compute the relative Ambient Air Density needed for comparative Air flow density/velocity in system. It is 1 factor in predetermining injector pulse width timing.

CEFI is not cheap it's primitive, it's not port injection, so it's no better than a decent carburetor is, as far as performance. In fact with speed density logic, CEFI is probably not as good as a decent carb, performance wise. IMHO. . . .

Speed density SEFI/TP is an improvement in air/fuel mix quality & distribuition into the combustion chambers, but it is still limited by speed density logic, more so if it suffers from bank fired sequencing also. It's the reason FoMoCo Commercial vehicles get poor fuel mileage and are slugs, compared to engines without speed density or bank firing.

FBp
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Old 01-26-2005, 12:09 AM
fefarms fefarms is offline
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Ford had some earlier efforts at fuel injection called CEFI. They resembled the GM throttle body injection. My point in the earlier post is that the range of vehicles discussed on this particular forum (1986 to 1996) does not include such systems.

I did not mean to give the impression in my earlier post that the mass air sensor is part of the throttle body. It isn't. It is typically mounted in the air ducting somewhere ahead of the throttle body. I stand by my statement that the MAF sensor measures the weight of air flowing through the throttle body -- at least if there aren't any leaks in the ducting between the MAF sensor and the throttle body.

Both MAP and MAF systems may be augmented by a BARO sensor that measures the uncorrected barometric pressure of the ambient air (primarily affected by altitude above sea level, but secondarily by weather). This is a somewhat redundant sensor used to fine tune the MAP sensor, and provide some degree of backup to the MAF sensor.

By batch fire I meant the "4 injectors at a time" scheme as described by EPNCSU2006 above. I suppose "bank fire" might be a synonym; I don't care for that term because it could be confused with the two cylinder banks of a V8.

"That means it has to fire one injector in a CEFI or all the injectors on one bank in a SEFI, before any RAM program changes can happen."

I do not understand the above statement.

Batch fire means the injectors are electrically tied together. They all must do the same thing. All 4 are either open or closed together. The PCM can and will make plenty of "RAM program changes" during the time of any one injector pulse, batch fired or not. The use of batch fire was common to all of the pickup trucks in the 1986 to 1996 range. It was commonly used by GM as well, for example the TPI Camaros and Corvettes through 1992. Such a feature can be critiqued as being somewhat less efficient and/or susceptible to higher emissions at low engine speeds and loads, but its presence, with all due respect, did not make any of these vehicles "a slug".

Many practitioners consider Speed Density to be superior to MAF technology. MAF sensors tend to be both delicate and expensive, as compared to MAP sensors. For a production vehicle which has been well tuned on a chassis dyno, a speed density system gives excellent performance and can be manufactured more cheaply than a MAF system. I will agree that MAF systems are superior in terms of automatically reacting to changes in the engine configuration, instead of requiring a re-tune of the speed density tables. They have also been found superior in the latest generation (post 1996) for reasons of better emissions and fuel mileage. Plus the bugs have been worked out of the MAF sensors by now and they don't fail as often.

Is SEFI better than batch fire. Sure. Is MAF better than Speed Density? Generally, yes. But both are subtle differences -- maybe 5% in fuel mileage and a modest improvement in idle quality and low speed driveability. No difference in peak power. I cannot agree with the sweeping statement that speed densitiy leads to "poor fuel mileage" or that such vehicles are "slugs".

A speed density, batch fire pickup truck is, indeed, a gas-hogging "slug" compared to a SEFI MAF-equipped Mustang. But I submit that vehicle weight and aerodynamics have much more to do with that situation than the difference in fuel injection systems.
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Old 01-26-2005, 06:50 AM
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Ford used the EEC-IV computer to control coil packs on early 4.6L motors in the crown vic's. EEC-V came about in or just prior to 1996 when the government mandated OBD-II. Anything between say, '85 or so and 1996 is EEC-IV, regardless of whether it is sequential (SEFI one injector per cylinder, fired as the intake valve opens), speed density, batch fired multipoint (MFI, one injector per cylinder, multiple injectors fired at once), has coil packs, or mass air. If you are interested, there is a great book on Ford's EFI systems by Charles Probst, Ford Fuel Injection and Electronic Engine Control. There are a couple versions for the different years of EFI; I have the one for '87-'93.

I also don't agree with batch fired speed density systems being slugs. That's what Ford used in all F-series trucks with the exception of the '94, '95, and '96 F150's.
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Old 01-26-2005, 07:16 AM
jroehl jroehl is offline
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Originally Posted by fefarms
Ford had some earlier efforts at fuel injection called CEFI. They resembled the GM throttle body injection. My point in the earlier post is that the range of vehicles discussed on this particular forum (1986 to 1996) does not include such systems.

You're right about the trucks not having it, but Ford did use TB injection on some other platforms into the late '80s. I had an '87 Mercury Lynx (Escort) with a 1.9L TB-injected engine. If you took the air cleaner off with the engine running, you could see the injector firing into the throttle body. (Or not, in one case, when the computer puked on me, making it fire erratically).

Jason
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Old 01-26-2005, 09:12 AM
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Thanks for an intelligent discusion here. I appreciate exchanges like this one.

CEFI fires a left or a right injector, program upgrading, what little of it slower speed density logic will provide, occcurs between signals thus operational changes occur.

I agree CEFI is off topic, and is antiquated, old hat stuff, except maybe to Holley or Moon Equipment who still try to push their CEFI systems as "real" Fuel Injection. True enough injectors atomize controlled Fuel loads, but distribution & A+F column density, sectional column homogenization, and column velocitys suck, just like with carburetion.

Speed density is a low/ slow logic narrow parameter program, lacking RAM power, as well as read out speeds found in MAFS systems. Tuned Port technology aside, MAFS systems when operating correctly, run roughly 1.5khz faster than speed density chip & system does. Plus MAFS system has a larger library of ROM/ PROM thus it creates or reads many more RAM programs faster & more accurately. Speed density, with limited ROM Library & very few enhanced programs lacks compensatory capabilities of MAFS.

Speed Density, bank firing systems, are greatly hardware specific, thus limited to that operation. Speed density systems are intolerant of system or hardware changes while MAFS with Mass Air Logic is virtually wide open for those who have a grip on laws of fluid dynamics, physics, math & engineering, plus the different functional capacities of digital operating systems used in the field today. It is not possible to change hardware or system, beyond parameters of ROM in a Speed Density chip & still get it to run very well, if at all.

This is not the case with MAFS systems, they will compenaste an incredible amount & they are not "confused" by changing their ROM, P-ROM chips nor piggybacking chips which are compatable, into their system. In fact one can take an MAFS digital control or ECM system off a 5.0L and install it on a 7.5L with adequate hardware & mechanical provisions & have it run well. This can not happen with speed density systems, period.


None of this can be done effectively with speed density. The reason most techs like speed density is it offers wide "average" to work within, so all one need do is get close within their the set up, and the system will run satisfactorily. But a MAFS system can be tweaked and peaked to perform beyond most peoples wildest imagination & dreams and that's a fact.

Unlike speed density, MAFS systems can be dialed in finitely and precisely for specific operational req's, if that is the case. As I said either a ROM Chip, a P-ROM or an array of piggybacks can be used to modify the program focus in any MAFS system. Another entirely different, but relative problem develops with MAFS when tech's push programs by trying to re-write the laws of physics, fluid dynamics, and mathematics.

However I will categorically state, if one has mastery of MAFS system function plus a good understanding & respect for supporting fields of science, math & engineering it takes to make an engine perform, Mass Air Logic is light years ahead of Speed Density and offers potentials which are still unexplored by most users today.

In that above statement is another reason "the masses" prefer S/D. It's less complex, easier to work with so long as 1 has correct logrythyms in PROM/ ROM, sensors, wiring harneses for the specifics of whatever engine you're tryin' to run.

IOW (&IMHO) S/D is a limited, narrow parameter, slow Hz, logic system while MAFS is as wide open as ones expertise may go and as fast as whatever chip one runs.

I have to admit, a SEFI/TP system running Speed Density & bank firing programming is a world away from mechanical fuel injection systems such as older Hilborn, or Enderle systems were. Although IMHO MAFS's as far ahead of Speed Density as Speed Density is from yesterdays mechanical fuel injection systems today.

But what do I know, huh?

FBp

Last edited by FordBoypete; 01-26-2005 at 09:17 AM.
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Old 01-26-2005, 10:25 AM
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Speed density is a low/ slow logic narrow parameter program, lacking RAM power, as well as read out speeds found in MAFS systems. Tuned Port technology aside, MAFS systems when operating correctly, run roughly 1.5khz faster than speed density chip & system does. Plus MAFS system has a larger library of ROM/ PROM thus it creates or reads many more RAM programs faster & more accurately. Speed density, with limited ROM Library & very few enhanced programs lacks compensatory capabilities of MAFS.
The EEC-IV should have the same processor and ram across the board, or so I thought. The reason MAF systems are adaptable is that they can measure the exact airmass that is entering the engine - I don't think it has anything to do with processor speed or computer memory. There is nothing wrong with speed density itself - the system works fine, but is just tuned for a small range of operating conditions. Our race car here at NC State (FSAE race car - 600cc Honda F4i motorcycle engine; www.wolfpackmotorsports.com) is programmed to use throttle position as the only load sensing device (for both fuel and spark timing curves), and it works fine under the conditions we operate it under. Having said that, we are going to forced induction this year and are planning on using a MAF meter to calculate load points for fuel, and use MAP to calculate load for ignition timing. At the moment we are running sequential spark and sequential injection, but in the past, we have used batch fire on the injectors, and a wasted spark output for the coils (coil on plugs), and all have worked for what we tuned them for. Having a MoTeC ECU, it's fully user defined, it's just a matter of getting the engine on the dyno and writing the maps, which is actually quite time consuming. It's all a matter of tuning - we have an engine dyno, so that is more feasable in our situation, whereas Ford tunes the computers and writes the maps for a certain set of operating conditions, maps that aren't easily modified by the general consumer. MAF offers more flexibility for modifications than does speed density, but I wouldn't necessarily say that one system is better than the other overall (comparing multipoint to multipoint here, I'm not including CFI/TBI systems).

Last edited by EPNCSU2006; 01-26-2005 at 10:29 AM.
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Old 08-15-2005, 05:41 AM
Raylostinfuel Raylostinfuel is offline
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Question Lost in fuel

1986 LTD what kind of EFI system was in place just wondering
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Old 08-15-2005, 06:11 AM
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