EFI OFAB & OFAC differences are a internet myth - discus
37 posts • Page 1 of 2 • 1, 2
EFI OFAB & OFAC differences are a internet myth - discus
Seems to me that the differences between OFAB and OFAC are pretty much a internet s**t myth!
They are both under the same wiring diagram in the Haynes manual and there isnt much documentation about the two either. It looks like the OFAC was just an upgrade to the OFAB in the same way that the Escort Turbo has 3 different ECU's which all work the same but have slight differences - ie the knock sensor.
The slight differences between the OFAB & OFAC are:
Pin 8 or 27 - CO Signal
Different connector for the map sensor
Different map sensor
Pin 45 is the same on both and apart from this there are no differences! So people are right when they say you must match a OFAB ECU and Map sensor & you must match a OFAC ECU and Map sensor but everything else including the wiring looms are interchangable.
Discuss and lets see if we can sort this out once and for all!
Dave.
They are both under the same wiring diagram in the Haynes manual and there isnt much documentation about the two either. It looks like the OFAC was just an upgrade to the OFAB in the same way that the Escort Turbo has 3 different ECU's which all work the same but have slight differences - ie the knock sensor.
The slight differences between the OFAB & OFAC are:
Pin 8 or 27 - CO Signal
Different connector for the map sensor
Different map sensor
Pin 45 is the same on both and apart from this there are no differences! So people are right when they say you must match a OFAB ECU and Map sensor & you must match a OFAC ECU and Map sensor but everything else including the wiring looms are interchangable.
Discuss and lets see if we can sort this out once and for all!
Dave.
- DavidBolton
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haveing looked my self at the wiring diagrams i cant see much differances other than like you say with the map sensors which as mention elsewhere a very different in that ofab is voltage type like cossies etc and the ofac is frequancy type like used on efi xr's but with a greater pressure range.
i have an efi loom from an xr2i to convert origionally to ofac but i now want ofab due to being able to run the 3 bar map sensor for greater boost. but having found info on loom changes from efi to ofac turbo i couldn't find an for ofab ecu, so after looking at the diagrams i cant find much in between ofac and ofab.
next opinion please.....
i have an efi loom from an xr2i to convert origionally to ofac but i now want ofab due to being able to run the 3 bar map sensor for greater boost. but having found info on loom changes from efi to ofac turbo i couldn't find an for ofab ecu, so after looking at the diagrams i cant find much in between ofac and ofab.
next opinion please.....
- RS TURBO S2
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The XR2i loom uses the right connector for the OFAC map sensor so you could use that ok. To use the OFAB map sensor just chop off the connector and wire in the OFAB style connector! Check the location of Pin 7/28 and select your ecu.
Dave.
Dave.
- DavidBolton
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the main problem i find with wiring looms is colour changes to the wires like when ford change from 1 manufacturer to another for the speedo like changing the fuel and temp guages round pointless unless they are setting out to confuse us mad modders...
ultimatly i will go for an aftermarket management on my car but i need efi to map it better thn the old mfi kak and aint the money for pectel or wot ever cossie stuff is ok but expensive by comparison to festa turbo stuff and not that much better in terms of mapping and reliability on a car with say 250 bhp.
ultimatly i will go for an aftermarket management on my car but i need efi to map it better thn the old mfi kak and aint the money for pectel or wot ever cossie stuff is ok but expensive by comparison to festa turbo stuff and not that much better in terms of mapping and reliability on a car with say 250 bhp.
- RS TURBO S2
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Stoned wrote:...... more boost and may be slightly less economical
if we cared about fuel economy would we drive these cars???
- RS TURBO S2
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Stoned wrote:bottom line is 0FAB lets you run more boost and may be slightly less economical
end of discussion
I know mate thats why I have OFAB but Im not talking about which system is best at the moment, simply the workings of both systems!
I lot of people still go OFAC because they arent looking to run high boost and parts are easier to get, like the 3 ecu's on ebay at the moment!
Dave.
- DavidBolton
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dave you say ofac is easier to get hold of your right about the ecu but trying to get a map sensor for the ofac is like trying to look cool in a nova
imposible
what does seperate them is down to the workings of the map sensor from wot i here, the ofac frequancy type is much more precise and acurate than the ofab voltage affair, maybe why the ofac's have better fuel economy,, i dunno. but this is all around the time of emissions this n that so maybe ford changed to ofac to lower the emisions for gov figues
any thoughts??
imposible
what does seperate them is down to the workings of the map sensor from wot i here, the ofac frequancy type is much more precise and acurate than the ofab voltage affair, maybe why the ofac's have better fuel economy,, i dunno. but this is all around the time of emissions this n that so maybe ford changed to ofac to lower the emisions for gov figues
any thoughts??
- RS TURBO S2
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Didnt know it was hard to get a OFAC map sensor, never tried though!
Yeah I'd agree that it sounds like the OFAC works better and is more precise. I bet most people who go OFAB because they want to run high boost probably never do as 1 bar is normally enough for most people!
Dave.
Yeah I'd agree that it sounds like the OFAC works better and is more precise. I bet most people who go OFAB because they want to run high boost probably never do as 1 bar is normally enough for most people!
Dave.
- DavidBolton
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OFAC
Mine is OFAC and seems to idle rev slightly lower than 2 OFAB FRSTs ive been in despite adjusting the screw, so maybe this is the only way OFAC reduces emissions???
Life moves pretty fast. If you don't stop to look around once in a while, you could miss it.
- MIK3Y
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>
Also both having 2 bar map sensors as standard does this mean it can gauge up to 2 bar of boost (28psi) or only 1 bar (14psi) of boost and 1 bar of vacum as ive read somewhere? Thanx
Thus meaning id hav to go OFAB and get a 3-bar map sensor to run more than 14psi?
Thus meaning id hav to go OFAB and get a 3-bar map sensor to run more than 14psi?
Life moves pretty fast. If you don't stop to look around once in a while, you could miss it.
- MIK3Y
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yes m8 thats right a two bar sensor measure 1 bar negative (vacumm like off boost yeah?) and 1 bar positive pressure (14.5 psi)
so basically a 2 bar will go to 14 psi acuratly and a 3 bar to 28 psi and so on i have seen a 5 bar map sensor somewhere
so basically a 2 bar will go to 14 psi acuratly and a 3 bar to 28 psi and so on i have seen a 5 bar map sensor somewhere
- RS TURBO S2
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yeah dave the 2.5 is the ofac one ?? is that right so should see 21 psi which is high enuff for most .. but i will run 28 psi for 1/4 miles or down the odd home straight on track days, thats if my 3 stage system works
- RS TURBO S2
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Go to search and search for ofab. Someone has asked this question before to which Gadget replied to showing pictures of the two different types of map sensor. Also you can look at the ECU - where the multi plug plugs in it says either ofac or ofab.
AHH yes that's right 2.5bar is escort cossie!!
AHH yes that's right 2.5bar is escort cossie!!
- RS TURBO S2
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oriont wrote:mines running ofac and peaks at 23psi and holds 21psi.
thanks
oriont
yeah have herd that this is fine especially on ofac stuff but the map sensor is not as acurate with boosts over its intended design parameters.
doesn't mean it wont work just that it may say there is only 20 psi when there is 24 and thus the ecu will only fuel accordingly with this reading.
this is only what i have been told by the way
- RS TURBO S2
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the map sensor is not as acurate with boosts over its intended design parameters.
doesn't mean it wont work just that it may say there is only 20 psi when there is 24 and thus the ecu will only fuel accordingly with this reading.
this is true but mine has been mapped by msd and has a box of tricks fitted to the map sensor wiring to smooth out signal
thanks
oriont[/quote]
doesn't mean it wont work just that it may say there is only 20 psi when there is 24 and thus the ecu will only fuel accordingly with this reading.
this is true but mine has been mapped by msd and has a box of tricks fitted to the map sensor wiring to smooth out signal
thanks
oriont[/quote]
- oriont
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oh i c the old box of trick trick eh?
dont think it works on the other map sensors does it??
only ofac type
???
just a geuss
dont think it works on the other map sensors does it??
only ofac type
???
just a geuss
- RS TURBO S2
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Alan Fibblesnork wrote:DavidBolton wrote:OFAC is still 2 (-1 +1) the 2.5 is cossie!
Dave.
Errr, are you sure about that one?!
Yeah OFAC is 2.5 isnt it, OFAB is 2 but can be replaced with a 3.
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Its excellent cheers Rolls, I just wish I could get some pics of the thing!
I dont have access to a digi camera! I have some pics on my phone but I need a blue tooth adapter for my pc to get them from the phone to my pc.
Dave.
I dont have access to a digi camera! I have some pics on my phone but I need a blue tooth adapter for my pc to get them from the phone to my pc.
Dave.
- DavidBolton
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James-UK wrote:Still not started then Dave?
Running standard ofab map at the moment, thanks for asking.
Dave.
- DavidBolton
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the truth
OFAB : - used in ERST managment, open an ecu and you will see the small pcb on spacers isolated from the ecu, (in other words there the same) used sign wave (voltage levels + and - 5 volts) to signal the processor on the main board (ecu) to drive the injectors.
OFAC : - uses binary 0s and 1s to signal the processor in the ecu that drives the injectors to vary there on and off time. Think I was told that this was changed due to noise levels on the signaling.
Ahmed bayjoo gave me this intresting info, thought I would share for those who maybe intrested.
OFAC : - uses binary 0s and 1s to signal the processor in the ecu that drives the injectors to vary there on and off time. Think I was told that this was changed due to noise levels on the signaling.
Ahmed bayjoo gave me this intresting info, thought I would share for those who maybe intrested.
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Re: EFI OFAB & OFAC differences are a internet myth - discus
Sooooooooooooo this debate still rumbles on,,not on this thread though untill now....
Found this http://passionford.com/forum/pictures-v ... urbos.html
the first post is all im interested in...20psi ..i thought standard management was supposedly s**t an no-one wants to map it anymore [ERRR] according to the bs on net its old hat an cant do much with it???
Reason i bought this up is im lookin at standard ecu's on skip bay an some are rather cheap..Gotta be fecked?...But i've become rather interested in all things electrical..eg pcb circuit design/layout/REPAIR..But i Cant find any FMC original circuit design/layout schemetics of how these ecu's were designed or what parts are used in em...?
Seen a Niche i wanna possibly fill
Anyone know how or where to possibly obtain such Data as someone designed the ECU's internal circuitry so original design Blueprints must be about somewhere?
Found this http://passionford.com/forum/pictures-v ... urbos.html
the first post is all im interested in...20psi ..i thought standard management was supposedly s**t an no-one wants to map it anymore [ERRR] according to the bs on net its old hat an cant do much with it???
Reason i bought this up is im lookin at standard ecu's on skip bay an some are rather cheap..Gotta be fecked?...But i've become rather interested in all things electrical..eg pcb circuit design/layout/REPAIR..But i Cant find any FMC original circuit design/layout schemetics of how these ecu's were designed or what parts are used in em...?
Seen a Niche i wanna possibly fill
Anyone know how or where to possibly obtain such Data as someone designed the ECU's internal circuitry so original design Blueprints must be about somewhere?
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Re: EFI OFAB & OFAC differences are a internet myth - discus
The yanks have spent a lot of time on EECIV and knew the system inside out about 20 years ago. There is loads of info out there.
Both OFAC and OFAB can run 20psi, but not particularly well. The OFAC MAP sensor is a frequency type and offers more accurate control, but has a limitation.
A mapper can go beyond the limit but accuracy goes out of the window.
The systems are good for a standard-ish car, but you are better off with something like MS if you want to start going beyond.
Both OFAC and OFAB can run 20psi, but not particularly well. The OFAC MAP sensor is a frequency type and offers more accurate control, but has a limitation.
A mapper can go beyond the limit but accuracy goes out of the window.
The systems are good for a standard-ish car, but you are better off with something like MS if you want to start going beyond.
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Re: EFI OFAB & OFAC differences are a internet myth - discus
Excursion wrote:The yanks have spent a lot of time on EECIV and knew the system inside out about 20 years ago. There is loads of info out there.
Both OFAC and OFAB can run 20psi, but not particularly well. The OFAC MAP sensor is a frequency type and offers more accurate control, but has a limitation.
A mapper can go beyond the limit but accuracy goes out of the window.
The systems are good for a standard-ish car, but you are better off with something like MS if you want to start going beyond.
Cheers fella...Was more lookin at the original design of the system....Like i say im trying to find if at all pos the original "CAD" if you will,,circuit layout diagrams/Bueprints for the circuit board itself..components list that stuff...
If that makes sense
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Re: EFI OFAB & OFAC differences are a internet myth - discus
legend,,
thats the stuff im lookin for...
where can i find them fella?...also is there a component makeup/id list/diagrams available?
thats the stuff im lookin for...
where can i find them fella?...also is there a component makeup/id list/diagrams available?
- Fraggle
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Re: EFI OFAB & OFAC differences are a internet myth - discus
PWM for the pressure transducer would be more accurate as you're only looking for rising / falling edges at the ECU end - the amplitude doesn't matter so long as there's enough deviation to trigger upon. Since the electrical characteristics of the loom change with time of year and age this system can only be described as a Good Thing. This would also make for less complicated code and use less resources on the ECU itself (you're just counting timings as opposed to requiring a historically expensive A/D converter). Also means less points of failure, another Good Thing.
The problem is that there's almost certainly not "room" in the ECU for the additional calibration data needed for a high pressure system (plus the transducer probably has limited resolution at the upper limits - you'd be pushing what the hardware can do at either end) which would limit what you could do with the ECU without losing map resolution.
Also seems to me that it would be a straightforward thing to build a PWM generator off the back of an A/D to allow you to run your own choice of MAP sensor; getting hold of the timing data and knowing if the A/D sample time would be acceptable for rapidly changing boost levels is quite another matter though.
OTOH I could be talking nutsack.
[/streamofconsciousness]
The problem is that there's almost certainly not "room" in the ECU for the additional calibration data needed for a high pressure system (plus the transducer probably has limited resolution at the upper limits - you'd be pushing what the hardware can do at either end) which would limit what you could do with the ECU without losing map resolution.
Also seems to me that it would be a straightforward thing to build a PWM generator off the back of an A/D to allow you to run your own choice of MAP sensor; getting hold of the timing data and knowing if the A/D sample time would be acceptable for rapidly changing boost levels is quite another matter though.
OTOH I could be talking nutsack.
[/streamofconsciousness]
Nothing to see here...
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37 posts • Page 1 of 2 • 1, 2
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