My S3C has no airflow meters
Discussion
I am confused 
about the fuel injection system on my S3C. All information I have seen on the S series and the Ford Sierra shows the system fitted with the twin airflow meters between the filter and plenum.
However, my S3C does not have any airflow meters, just uninterrupted flexy hoses leading directly from the filter to the plenum. Instead there is a MAP (manifold absolute pressure) sensor connected to the rear of the plenum.
Does anybody else have experience of this? What are the performance implications of the flow meters vs MAP type setup? How common are the cars like mine?
BTW, as far as I know, most injected motorbikes stick with just the MAP, I guess due to space restrictions.
My S3C runs perfectly so no immediate problem. However, any info would be much appreciated, especially if my car is consequently inferior in some way!
Jonathan W.
about the fuel injection system on my S3C. All information I have seen on the S series and the Ford Sierra shows the system fitted with the twin airflow meters between the filter and plenum. However, my S3C does not have any airflow meters, just uninterrupted flexy hoses leading directly from the filter to the plenum. Instead there is a MAP (manifold absolute pressure) sensor connected to the rear of the plenum.
Does anybody else have experience of this? What are the performance implications of the flow meters vs MAP type setup? How common are the cars like mine?
BTW, as far as I know, most injected motorbikes stick with just the MAP, I guess due to space restrictions.
My S3C runs perfectly so no immediate problem. However, any info would be much appreciated, especially if my car is consequently inferior in some way!
Jonathan W.
Thanks for the info guys. It's good to know that my car is "normal"!
I wonder if deletion of the meters was more of an economy or reliability measure? They are expensive and do fail on other vehicles I have known. Generally, I have seen plenty of modern catted cars (all makes) with both the flow meters and lambda sensors.
Maybe there is a fuel injection tech out there who can enlighten us.
I wonder if deletion of the meters was more of an economy or reliability measure? They are expensive and do fail on other vehicles I have known. Generally, I have seen plenty of modern catted cars (all makes) with both the flow meters and lambda sensors.
Maybe there is a fuel injection tech out there who can enlighten us.
This came up once before. Here is the waffle I spouted at the time, it may help to confuse you. 
The S3Cs run closed loop systems using the lambda sensors which feeds a control voltage to the vane air flow meter which is part of the Ford EEC IV system (Bosch L-Jetronic). The mass for a given volume of air will change with temp and another sensor measures the air temperature.
I am led to believe that the non cat 2.9s and 2.8s (Bosch K-Jetronic) also use an electronic sensor reading from the exhaust flow but not in closed loop. This operates in a similar manner with a temp sensor being used to calculate the the mass per given volume of air.
The V8 Lucas system uses a mass air flow system which measures the cooling effect of a hot wire positioned in the air flow.
The S3Cs run closed loop systems using the lambda sensors which feeds a control voltage to the vane air flow meter which is part of the Ford EEC IV system (Bosch L-Jetronic). The mass for a given volume of air will change with temp and another sensor measures the air temperature.
I am led to believe that the non cat 2.9s and 2.8s (Bosch K-Jetronic) also use an electronic sensor reading from the exhaust flow but not in closed loop. This operates in a similar manner with a temp sensor being used to calculate the the mass per given volume of air.
The V8 Lucas system uses a mass air flow system which measures the cooling effect of a hot wire positioned in the air flow.
Thanks for that. I AM more confused now!!!! (But appreciate the info nontheless)
How can the lambda feedback a control voltage to the flow meter when there is no flow meter?? This appears also to be the case on other forum members' S3c & S4c cars.
On my S3c the flow meters are absent and there is a MAP sensor instead. I think if there were flow meters, then there would be no MAP sensor, just a barometric pressure sensor?
I have an American book at home about the EEC IV system. It says that the flow meters and MAP sensor are basically alternate systems, you have one or the other. Unfortunately it does not say which system is "better". Also I am not at home again for another week before I can check further.
Oh well, the car goes alright so no worries.
Jonathan W.
How can the lambda feedback a control voltage to the flow meter when there is no flow meter?? This appears also to be the case on other forum members' S3c & S4c cars.
On my S3c the flow meters are absent and there is a MAP sensor instead. I think if there were flow meters, then there would be no MAP sensor, just a barometric pressure sensor?
I have an American book at home about the EEC IV system. It says that the flow meters and MAP sensor are basically alternate systems, you have one or the other. Unfortunately it does not say which system is "better". Also I am not at home again for another week before I can check further.
Oh well, the car goes alright so no worries.
Jonathan W.
I don't think de-catting will have any impact on the need of airflow meters vs MAP. Mine is de-catted and runs fine with no other mods. The Lambda senosrs are retained.
There are plenty of other catted vehicles on the road using flow meter and plenty of non-cattted with MAP sensors.
The lambda sensor is supposed to keep the mixture accurate so as not to damage the cat. I think it is true that orignally non-cat S's don't have Lambda sensors?
As far as I know the flow meters and MAP are a different way of achieving the same thing, ie measuring how much air is going into the engine.
What I would like to know is, what are the pros and cons of the two systems??? When I get home, I will make furher enquiries.
J.W.
There are plenty of other catted vehicles on the road using flow meter and plenty of non-cattted with MAP sensors.
The lambda sensor is supposed to keep the mixture accurate so as not to damage the cat. I think it is true that orignally non-cat S's don't have Lambda sensors?
As far as I know the flow meters and MAP are a different way of achieving the same thing, ie measuring how much air is going into the engine.
What I would like to know is, what are the pros and cons of the two systems??? When I get home, I will make furher enquiries.
J.W.
Not sure of the details of the EEC IV ECU (whoever has that American book - any chance of a look / copy??).
All the ECU needs to know is how much air is coming into the engine. I assume that use of a MAP sensor and air temp sensor, then you could have an output signal correlating to the air mass. You then use the Lambda sensor to maintain your air/fuel ratio and voila, you have an engine operating without air flow meters.
The main reason to do away with them is that they give a flow restriction - unless they are a larger 'free'diameter than the throttle bodies.
In the V6, the plenum and fuel manifold also restrict airflow, so any way you can minimise this is good - hence more torque from the Cat models - no AFM's.
All IMHO at least!!
Marcus
All the ECU needs to know is how much air is coming into the engine. I assume that use of a MAP sensor and air temp sensor, then you could have an output signal correlating to the air mass. You then use the Lambda sensor to maintain your air/fuel ratio and voila, you have an engine operating without air flow meters.
The main reason to do away with them is that they give a flow restriction - unless they are a larger 'free'diameter than the throttle bodies.
In the V6, the plenum and fuel manifold also restrict airflow, so any way you can minimise this is good - hence more torque from the Cat models - no AFM's.
All IMHO at least!!
Marcus
It's me that's got the book. It's very informative. I am indeed offshore at present and can't remember the title, but I bought it from Demon Tweeks.
Fuel injection mystery is currently not my preoccupation as the engine is kaput due to seized No2 cam bearing = scrap block after 65k miles.
However, a problem with the MAP system is that the engine becomes very sensitive to vacuum. Anything which changes the vacuum changes the fuelling. So a small air leak or changing the cam can mess things up, so I am informed.
Will see what happens when I have rebuilt this heap with a new block.
JW
Fuel injection mystery is currently not my preoccupation as the engine is kaput due to seized No2 cam bearing = scrap block after 65k miles.
However, a problem with the MAP system is that the engine becomes very sensitive to vacuum. Anything which changes the vacuum changes the fuelling. So a small air leak or changing the cam can mess things up, so I am informed.
Will see what happens when I have rebuilt this heap with a new block.
JW
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