Cpu to EFI Error?
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New User
Joined: Aug 2003
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Cpu to EFI Error?
I have a 89 E350 MH. The tires were changed to a larger size from noted factory size. I have a 7 1/2% under mileage error from the change. Obviously the mileage is reported incorrectly, but is there a change to trans operation and EFI metering from this under speed feedback that would change mileage, primarily, or mechanical longevity. If there is a change is it worthwhile or cost effective to change the VSS gearing?
to get a better handle on this the facts are: current tires are 235x16.5 from normal 215x16.5 with a recorded 1.85 miles over a measured 2 miles.
Jeff
to get a better handle on this the facts are: current tires are 235x16.5 from normal 215x16.5 with a recorded 1.85 miles over a measured 2 miles.
Jeff
Elder User
Joined: Aug 2001
Posts: 508
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Cpu to EFI Error?
Your current setup has a slight amount of "error" - the computer probably thinks you are towing something heavy all the time.
However, changing the VSS gearing will introduce significant "error" because the engine rpm vs measured mph relationship will change.
Your 7.5% error is probably within the acceptable speedo error. The difference between fresh tires and bald tires might be that much.
However, changing the VSS gearing will introduce significant "error" because the engine rpm vs measured mph relationship will change.
Your 7.5% error is probably within the acceptable speedo error. The difference between fresh tires and bald tires might be that much.
