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Thread: Getting atrocious mileage?

  1. #61
    Join Date
    Nov 2010
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    NC
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    Quote Originally Posted by Vovchandr View Post
    Update:

    Replaced the o2 and here is the latest data.

    City low RPM cruising 12.7 miles .493 gallons. ~25mpg
    All highway ~70mph average in 6spd 30 miles 1.481 gallons ~ 21mpg

    Average ~21mpg

    I think I'm in the right ballpark now?
    Your in the right direction yes , Fuel psi is to high , Unhook the Vac to your regulator and see what the psi is engine running at idle ( proper way to check psi ) adjust psi to 39-41psi by lowering your fuel psi you could throw off your WOT A/F so watch that , your target WOT A/F is 12.8 and anything over 13.2 after 3500 LET OFF your lean

    Now we need to see what your stft1 is reading , this reading is your short turm fuel trim ( Info from your new o2 to the PCM to control fueling ) and if it is way off you could loose 1-3 MPG with very steady throttle at idle or cruise ideally you want it to read between .97 to 1.03 always switching up and down and up and down , when logging it should resemble a castle top around the castle wall if that makes sense

    When you log I will be glad to remote in and look at the log why its running , I use www.teamviewer.com if you would like the help

    Tom

  2. #62
    Join Date
    May 2018
    Location
    Albany, NY
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    233

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    Quote Originally Posted by 1turbofocus View Post
    Your in the right direction yes , Fuel psi is to high , Unhook the Vac to your regulator and see what the psi is engine running at idle ( proper way to check psi ) adjust psi to 39-41psi by lowering your fuel psi you could throw off your WOT A/F so watch that , your target WOT A/F is 12.8 and anything over 13.2 after 3500 LET OFF your lean

    Now we need to see what your stft1 is reading , this reading is your short turm fuel trim ( Info from your new o2 to the PCM to control fueling ) and if it is way off you could loose 1-3 MPG with very steady throttle at idle or cruise ideally you want it to read between .97 to 1.03 always switching up and down and up and down , when logging it should resemble a castle top around the castle wall if that makes sense

    When you log I will be glad to remote in and look at the log why its running , I use www.teamviewer.com if you would like the help

    Tom
    Tom, my TWM FPR is part of the fuel rail and doesn't have a vacuum line hook up? I can adjust down to ~40psi and from what I've seen so far my fuel pressure doesn't fluctuate at all. I have never diverged into fuel system in vehicles, but to make sure i understand correctly, typically fuel pumps put out constant pressure and systems like FPR adjust the pressure with vacuum or other means? ECU never controls pressure at fuel pump with different voltages for closed/open loop conditions? IE running rich or lean wouldn't be a function of ECU commands? Car is getting better mileage but feels more sluggish on the top end on the butt dyno, but we all know that measures pretty inconsistently.




    I'm still struggling to get my profile loaded to get Pectel to communicate with Descpro software properly and will keep addressing that.


    I'll be looking at my A/F at idle as I adjust it? I use my downstream plug past the cat I should expect to read ~.2 to ~.5 richer or leaner?
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    2001 Caterham Superlight R

  3. #63
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    May 2018
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    Albany, NY
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    Quote Originally Posted by Slonie View Post
    I've got this issue too, I did some Googling about those TWM throttles (what I've got on my Zetec), and found Honda guys complaining about the same issue. One guy fabbed up a secondary return spring to get them to snap all the way closed. Have been planning to look into doing that myself, after fixing other things...
    I'm going to be taking a better look at this myself. I did a through lubing of the cable yesterday and will see if that helped.

    Otherwise this is what I gathered on the matter

    As the shaft that the spring loaded butterfly valves are attached to rotates in the brass or bronze bushing in the throttle body housing, it tends to wear one side of the bushing out.
    2001 Caterham Superlight R

  4. #64
    Join Date
    Jan 2018
    Location
    California
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    20

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    Quote Originally Posted by Vovchandr View Post
    I'm going to be taking a better look at this myself.
    I'm looking forward to your findings, for when I get around to it. It's a few rungs down on the hierarchy of needs for my car right now, but one of the truly annoying things with it when it was up and running...

  5. #65
    Join Date
    Nov 2010
    Location
    NC
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    159

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    Quote Originally Posted by Vovchandr View Post
    Tom, my TWM FPR is part of the fuel rail and doesn't have a vacuum line hook up? I can adjust down to ~40psi and from what I've seen so far my fuel pressure doesn't fluctuate at all. I have never diverged into fuel system in vehicles, but to make sure i understand correctly, typically fuel pumps put out constant pressure and systems like FPR adjust the pressure with vacuum or other means? ECU never controls pressure at fuel pump with different voltages for closed/open loop conditions? IE running rich or lean wouldn't be a function of ECU commands? Car is getting better mileage but feels more sluggish on the top end on the butt dyno, but we all know that measures pretty inconsistently.




    I'm still struggling to get my profile loaded to get Pectel to communicate with Descpro software properly and will keep addressing that.


    I'll be looking at my A/F at idle as I adjust it? I use my downstream plug past the cat I should expect to read ~.2 to ~.5 richer or leaner?
    No way to answer this , depends on to many things , I would use the front o2 hole and see what it reads vs behind the CAT

    " typically fuel pumps put out constant pressure and systems like FPR adjust the pressure with vacuum or other means? " With your System yes your correct return fuel system , In the Focus the ECU/PCM controls the Fuel psi which is a non return fuel system

    " ECU never controls pressure at fuel pump with different voltages for closed/open loop conditions? " in a non return fuel system ( most EFI cars ) the ECU totally controls the fuel pump psi , with a return system most have a Vac port and depending on Vac raises or lowers the fuel psi.

    " IE running rich or lean wouldn't be a function of ECU commands? " Incorrect
    Closed loop ( idle and part throttle ) fuel control works off the front o2 and tells the ECU what your A/F is to rich or to lean the ECU adjust the fueling through the short turm fuel trim , The stft will tell you if you need to add or remove fuel to hit the targeted closed loop fuel

    Open Loop Fueling ( Wide Open Throttle ) is set tables in your tuning software and depending on your WOT A/F you adjust these to hit a set A/F , I use 12.8 A/F

    Tom

  6. #66
    Join Date
    May 2018
    Location
    Albany, NY
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    233

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    Quick update.

    Tried to adjust this two days ago before a track day yesterday. As soon as I tried to rotate the allen key on the FPR with the car at idle, the twisting force let the gas squirt out around the mount of the FPR (it's bolted straight to fuel rail as shown above).

    Tried it again and same thing happened.

    At the same time my wideband computer box stopped working (battery corroded off the 9v terminal).

    with no way to measure and a track day the next day (yesterday) and still trying to get ready for NJMP I left this alone right now and won't touch it through the week.



    Got some other issues to troubleshoot right now to get the car ready for next week.

    If the FPR leaks during operation that could also be a relevant issue to the bad MPG.
    2001 Caterham Superlight R

  7. #67
    Join Date
    May 2018
    Location
    Albany, NY
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    233

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    New pigtails ordered to fix the wide band.

    Will mess with this further after NJ

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    2001 Caterham Superlight R

  8. #68
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    May 2018
    Location
    Albany, NY
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    As some of you know the car had an transmission/clutch fail at NJMP. It's still down waiting for me to do an engine out troubleshooting of what exactly happened.

    This obviously puts any MPG troubleshooting on hold for at least another month.


    On this subject, should I do both engine and transmission at once or separate at the bell housing and just pull the engine out? I'm coming out of the top.
    2001 Caterham Superlight R

  9. #69
    Join Date
    Feb 2009
    Location
    NYC
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    4,553

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    Do both at once is the accepted wisdom.
    Mike
    2010 Caterham CSR with Cosworth 2.3 Duratec
    2018 Caterham 420R with 2L Duratec 210hp at Donington UK
    1975 BMW CSL Group 4 (restoration - engine and dry sump install time)
    1977 Holden Torana "A9X" (awaiting restoration)
    1985 Holden Commodore Group A (restoration - engine rebuild)
    1982 Ferrari 400i (will repaint to original color in 2020)
    1965 Ford Mustang Fastback "Holman Moody"
    1992 Ford Escort RS Cosworth WRC (fettling after long period of storage)
    1990 Range Rover 2 door Classic

  10. #70
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    Jan 2006
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    Just remember to drain the transmission first or you will have an oil slick under the car once the driveshaft separates.

    -John
    '95 Westfield SEiW w/2.0L Duratec
    '68 Lotus Elan FHC
    '91 Miata w/Flyin Miata suspension & brakes
    '95 Porsche 993 C2
    '86 Porsche 944 turbo (neglected project car)
    Throttle Steer

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