S3C fuel pressure and Lambda sensors?

[sebackman]

I have an adjustable fuel pressure regulator in my S3C. What fuel pressure do you run in your cars? Do you set it a idle or at a certain revolution?

In the S3C there are dual lambda sensors, one in each exhaust manifold. I believe that both are connected to the Ford EEC IV ECU.

But does the Ford EEV IV box need both Lambda sensors connected or just one. This is the normal in other cars and if there are indeed 2 sensors, the second is usually after the cat not before as in the S3C.

I'm going Emerald ECU later but would like to go to a wide band sensor already now but the one I'm using only has one narrow band sensor output.

Or can I feed both Ford ECU lambda inputs the same narrow band signal?

The lambda instrument in the dash will show both banks wide band input.

Thank you
//Rob

[mentall]

The wiring diagram I use (XR4x4 1990, German) which corresponds pretty exactly with my engine wiring (1990 S3C) shows "HEGO sensor right" and "HEGO sensor left" separately connected to the ECU. Right is a blue/black wire and left is a blue/white wire

Do they alter the fuelling independently for each bank of cylinders? Probably, although of course they are only effective when the ECU is in 'closed-loop' mode.

I'm not aware that any of the EEC-IV systems had a post-cat lambda sensor, and Probst doesn't mention them in his book. Presumably the purpose of the lambda sensors is to make the oxygen content of the exhaust correct for the cat input, without any feedback from the cat exhaust output. And of course we have two cats, each needing its lambda control.

My 1990 car is decatted anyway, but it still needs the lambda sensors to meet the (slacker, pre-1991) emission requirement.

Fuel pressure: I run a standard (equivalent) Ford part. This is a 3.0 bar item: I don't think the pressure can be altered using a standard ECU.

No idea about other ECU's: don't they allow for 2 separate cats (ie one per bank)?

[magpies]

Within the range 40 to 45 psi is normal - I have also included a fuel pressure gauge in my dash.

[sebackman]

Thank you for feed back.

I will set the fuel pressure to just under 3bar then. Great

There will be a dual channel wide band gauge connected once I can sort the HEGO connections.

Mentall, can you please share the wire diagram you mentioned or a link?

I have also sent and email to Emerald on the topic but for now I want to use the Ford box with the new wide band O2 sensors and I only have one simulated narrow band signal to feed the Ford box with.

[Fefeu52]

I own a 1992 S3C. When I bought it, one of the 2 HEGO was disconnected, and the mixture was awful on this side of the engine (bank)
There is 2 sides for the faulty codes (41 and 91 for too lean left or right bank ; 42 and 92 for too rich left or right bank)

2 catalytic converters, 2 HEGO, 2 systems to regulate the mixture.

The only way I found to adjust accurately my Malpassi regulator, was to build a default code reader. With it, it's pretty easy to adjust the mixture. 30 PSI is correct at idle (a little bit more than 2b) and 40psi with the vacuum remove. The only important value is the 30psi at idle, and you will need to adjust accurately with the default code reader.

[mentall]

Here's the diagram: print on 3 A4 pages, trim and stick together.

I'm trying (again) to 'panorama' them on to 1 sheet, but no success so far.

I was sure I had put these on "Useful links" years ago, but apparently not.

The original thread from 2019 is at: https://www.pistonheads.com/gassing/topic.asp?h=0&...

Edited by mentall on Friday 22 July 17:09

[sebackman]

Brilliant. Thank you.