×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Air & Fuel Filter Restriction

Air & Fuel Filter Restriction

Air & Fuel Filter Restriction

(OP)
After many years working with carburettor engines and the problems caused by the above, I have yet to see any clear facts on how air & fuel filter restriction affects engines with fuel injection and engine management systems. It would appear that the EMS must compensate, presumably by reducing power output to maintain correct exhaust gas balance.
   Is anyone any better informed?

RE: Air & Fuel Filter Restriction

Air filter restriction will be compensated for because all EFIs measure manifold air pressure.

Fuel filter restriction might flag an error code due to low fuel rail pressure, but other than that would not be compensated for so the engine would run leaner than expected at high power. I suppose the flag could be used to force the engine into a limp home mode with a reduced red line but AFAIK this is not done on ours, since we don't measure the fuel-rail pressure. Persistent lean running might flag an error, but I doubt the mixture is checked at WOT since it is open loop.

Cheers

Greg Locock

RE: Air & Fuel Filter Restriction

When the vehicle is closed loop, the O2 sensor would probably increase the injection slightly to compensate for the clogged fuel filter.  Other than WOT, there may be little or no noticeable power loss.  EFI systems seems to have a wide tolerance to compensate for poor maintenance.  I had a hard case student that though he could detect a missing spark plug at idle.  We pulled 5 plug wires off a V-8 before the idle became unsteady.  It even restarted (hot) on 3 cylinders.  Power however was lousy and you shouldn't try this at home!

Blacksmith

RE: Air & Fuel Filter Restriction

(OP)
Thanks for the foregoing answers. My curiousity has been stirred to wonder, in a worse-case scenario, do you end up with an engine running at idle and no more? I did have a two-stroke boat engine that reached that state but that was due to carbon build-up on the piston covering 85% of the inlet port!

RE: Air & Fuel Filter Restriction

More likely you will end up with a "code" and limp home mode due to a  mismatch between RPM, throttle position and manifold pressure in either case.  (The diagnostic algorithm just compares the three values to see if they are tracking and the engine is responding accordingly.)  Plugged air filter = manifold pressure too low, plugged fuel filter = throttle position too high.

Blacksmith

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources