Can an S5 AFM be used with an S4 ECU?
 

Didn't see this in the 'search' function.

Both are from N/A cars.

I have an S5 engine swapped into a Jensen Healey. I am planning to dump the electronic OMP and go with an S4 front cover, mechanical OMP, S4 TPS etc. It would greatly simplify things for me if I could use the S5 air flow meter with the S4 ECU.

I understand it can be done and does anyone out there have wiring info?

TIA.

Not easily. Damn it, I just went to find a link to a page that describes how the conversion is done, but the site is dead :(.

Why can't you use an S4 AFM, space issues?

EDIT, this may help:
http://www.nopistons.com/forums/S4-S...ion-t3067.html

yes, it will work fine.

the wiring is straight forward...there's a guide out there that is actually wrong on the wiring.

follow post #9 on that nopistons link and it should work properly.

Someone posted the jpg below. As for being right or wrong? Got me. Never did it or looked at it that much. No gain over the stock series four from what I understand.

the jpg is wrong.

The afm plugs are different b/t series four and series five. Are you going to cut a series five afm plug off the series five harness and then splice the wires on THAT plug to the series four harness? OR????????? How are you going to handle that?

You will lose the fuel pump switch that you have in the series four afm when installing a series five afm. That switch puts a gnd on the circuit opening relay when the engine is actually running. Keeps the fuel pump running once the engine starts.

Go look at YOUR series four afm plug from the WIRE side of the plug. ON the far left of the plug, are the wire colors as following: a Brown wire.......a pure black wire.........and the third wire from the left a Brown/Black wire. Forget the other colors for now. This is to determine if you have a early series four EM harness or a later series four harness. NEED TO KNOW.

The two wires on the far left as you look into the wire side of the plug, will not be used in the series five afm plug. Those two will be jumpered together permanetly, causing the circuit opening relay to be pulled in anytime the key is to ON or better. Means the fuel pump will always run with key to ON or better.

The third wire over from the left is brown/black and the brown/black of the series five does the same function.

The G/O wires are the same function in the two series.

The G/L in the series four is the same as the pure green in the series five.

The BROWN/WHITE in both series are the same function also.

Early series four cars use brown/black wires for gnd and the later series four use pure black instead. Confuses people who have early cars and are looking at later series dwgs.

Curious, what's wrong with the JPG?

I'm the original author of that JPG. I made it a long time ago when I installed a S5 AFM in my old 86 SE. The wiring lined up as shown and never had a problem with it.

-Jeff

Thanks for all the replies!

Mostly it's space issues for the MAF. I'd also have to build another complete intake between the air filter and AFM. Also, I currently am using an S5 ECU and harness, and I have already bypassed the original ECU controls for the fuel pump relay. I'm planning to custom wire an S4 ECU. I have wiring diagrams for early and late S4 and also for S5 but they just show you where they go, not what they do.

I am trying to get rid of that damn 'limp mode', which kills the trailing ignition. The OMP is working just fine but every so often it goes into limp on acceleration for no discernible reason and I am tired of screwing around with it.

i originally wired mine as per the jpg, making sure i had the plug orientations correct, afm didn't work. so i basically matched the colors of the wires...and bam it worked.

chip the ECU so you can keep VDI