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Topic: Stock 5.0HO - MA vs SD - but I don't understand something... (Read 754 times) previous topic - next topic

Stock 5.0HO - MA vs SD - but I don't understand something...

All,

Okay, my apologies if this is something of a dumb question.

Almost any reference I've come across says that Ford switched from Speed Density to Mass Air on the 5.0 HO in 1989.

Fine, all well and good.

However, everything I've come across also says that:

1) Fuel economy went down by about 1 MPG city and 2 MPG highway.
2) Despite not changing the ratings on paper, the engine actually lost some power.
and
3) The Mass Air system, as calibrated from the factory, runs a bit on the rich side, and there's actually power to be gained by leaning it out (probably also the lost fuel economy as well).

Okay, I could understand that . . *IF* the system were running open-loop.  But shouldn't the computer know to lean things out because the oxygen sensors should be sending a signal basically saying "Hey moron, you're running too rich here!"?

So, why does the stock 5.0HO mass-air system run richer, and thus with less power and fuel economy, than it should?
1988 Thunderbird Sport V8 - only 1 previous owner, and 110% bone stock so far... and sold to Nate!

Stock 5.0HO - MA vs SD - but I don't understand something...

Reply #1 –
Im no expert on it but i believe the "problem" with the mass air cars was the fact that the mass air sensor is smaller than the throttle body and is a restriction on the intake causing the "loss of power". Thats what my understanding was though i know someone else on here knows alot more about fords EFI than i do.
 

Stock 5.0HO - MA vs SD - but I don't understand something...

Reply #2 –
1.The maf being smaller is correct,therefore causing the loss of power.
2.The car being slightly richer is ford's doing,all there eec's are rich due to the fact that all engine's are different as well as the wear factor over time and they did not want there engines possibly leaning out and causing parts breakage(safety thing).
3.Yes there is power to be gained by leaning the A/F out a point or 2 but to do so you need a wideband to monitor the A/F and an adjustable fuel pressure regulator or tuner to do so correctly.