Results 1 to 10 of 10

Thread: Cruising oscillations at light load tip-in.

  1. #1

    Default Cruising oscillations at light load tip-in.

    I have a Ford 427W that I recently installed the Holley HP to control. The cam is about 250° @ .050" with 300° advertised duration & about 0.600" lift. 110° LSA installed 4° advanced as specced by the manufacturer. The engine has 10.7:1 compression. Transmission is manual TKO500, gears are 3.55s. I'm using the Holley dual-sync distributor, not the Ford TFI.

    The engine runs quite well using the MPI48BB245HE base GF modified for my engine particulars with tweaks to Ford IAC to get a solid 900 RPM idle. Idle vacuum is about 9" Hg on my gauge, which matches what the Holley sees using a GM 3 bar. IAC Hold Position is 35% during this datalog. The main issue I have is the typical tip-in oscillations one normally sees with a larger cam.

    I've attached a zoomed in part of a datalog where I tipped in the throttle after a deceleration. I think it speaks for itself. I can provide my tune if needed, though it's essentially the base GF mentioned above with some fuel table learning. I'm just wondering if there are any methods/secrets to minimizing the oscillations, which lead to driveline clunking in the worst case. Any input will be appreciated.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Oscillations.jpg 
Views:	18 
Size:	76.1 KB 
ID:	8556  

  2. #2
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,376

    Default

    For further assistance, post your Global File and a short datalog of this occurrence for us to analyze.
    Also, review the datalog and inform us of exactly where in the datalog (time/seconds) the problem occurs.
    Datalog & Global Files must be linked to a document hosting website. I use Dropbox.com.
    Files can also be "zipped" (compressed zipped folder) & attached directly to a forum post.
    Your Global File is in the "Documents", "Holley", "HEFI V4", "Global Files" folder (.hefi file).
    Your Datalogs are in the "Documents", "Holley", "HEFI V4", "Datalogs" folder (.V4.dl file).
    Someone will analyze/troubleshoot the problem & offer advice. Also, ensure all this is right:
    http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Steps #1-#6!)
    Quick Datalogger Information:
    Always provide data, not just symptoms. Is the AFR & ignition timing optimized? Overlay the datalog onto your Global File.
    Ensure the Target A/F Ratio table is properly programmed for your engine. Ensure the ECU is "Learning" (Learn Table LINK).
    Scroll through the datalog to the problem area. Then look exactly where this happens on the Base Fuel & Timing Tables. Scrutinize:
    RPM, MAP, MAT, TPS, CTS, IAC, Target AFR, AFR Left, CL Comp, Ignition Timing, Duty Cycle, Fuel Flow, Fuel Pressure & Battery.

    Using the Holley EFI software (LINK), look at where the live cursor moves to during this occurrence, and
    manually tune that area of the Base Fuel Table (enrich or lean) & Base Timing Table (optimize ignition timing).


    I find the most helpful datalog function, is overlaying the datalog on your Global File.
    I'm in the habit of using the datalog Overlay feature every time I review a datalog.
    Click on "Datalog" (on the top Toolbar), "Activate Overlay", then "Open Data Log".
    You can literally "playback" a recorded event, and watch it as it happened on any screen.
    Minimize (shrink) the datalog window, and move it to the bottom of any Global File screen.
    Then click & scroll anywhere on the datalog, and watch it playback on your Global File (EFI software).
    http://documents.holley.com/techlibr...9r10543rev.pdf (Holley EFI Datalogger Instructions)
    https://forums.holley.com/showthread...s-amp-Datalogs (Datalog & System Log Information - Read "NOTES")
    https://www.youtube.com/watch?v=iqHO...C6FEA0BB99AF17 (How To Record & Email A Datalog)
    https://forums.holley.com/showthread...7531#post77531 (Closed Loop Datalog Tuning - Posts #2, #4 & #6)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, 100HP progressive dry direct-port NOS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, 160A 3G alternator, Optima Red battery, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3

    Default

    Thanks Danny! it must be tedious reposting the same information repeatedly for different users. I feel like I should apologize for the post, though in writing said post it prompted me to use better search terms which lead me to several threads on this topic. I learned how to use the Overlay to look at the region in question. I learned from another of your posts to look at a tuning manual from a different vendor which suggests that with larger cams, one should enrich the mixture even more at lower RPM to compensate for exhaust dilution caused by the larger overlap camshaft. Since my idle works quite well at 14:1 target, I'll likely try a "peninsula" of richer targets for these high vacuum conditions just off idle to about 2500 RPM. I'll start with 13.5:1 in this area and go from there. They also suggest possibly advancing the timing in this area to get a head start on these diluted slow burning mixtures, but fueling seems like the 1st concern followed by timing.

    I feel like I jumped ahead a bit here, if anybody reading this would like to reference the threads I was reading, I could hotlink them into the text above. I have included a snippet of my datalog file and my Global File in an attached zip file if anybody is curious to see what this looks like. Turn on the Overlay and you'll see the area between 1600-2000 RPM highlighted. Thanks again Danny, it was your attention to detail in reposting links to relevant threads that gave me a better understanding of how to deal with this issue.
    Attached Files Attached Files
    Last edited by Cougar5.0; 08-10-2019 at 07:26 AM.

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,376

    Default

    You're welcome, and thanks for the compliment.
    TIP: http://forums.holley.com/showthread....4647#post64647 (How To Search The Holley Forums)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, 100HP progressive dry direct-port NOS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, 160A 3G alternator, Optima Red battery, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  5. #5
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,345

    Default

    If you rescale your MAP in your Base Fuel Table so it does not go down to zero, and then look at your fuel map in VE form, you'll see how terrible your fuel map is.

  6. #6

    Default

    I actually haven't touched the fuel map much so it's pretty smooth still. The interesting thing I'm seeing right now is when I tip-in, the AFR goes a little rich so fuel is pulled (note there's no AE fuel involved here), then as the AFR starts to get above target ~13.5:1, the engine starts misfiring (when AFR gets above ~14.5:1) while fuel is being added, which causes even more fuel to be added. I think this is difficult to deal with in Closed Loop as it's alternatively subtracting & adding fuel in the same area of the Base Fuel Table. I'd like to keep Closed Loop control, so I'm thinking of pulling fuel in this area, then commanding a richer AFR through this area in an attempt to prevent the misfires, which seem to toss a match onto the control scheme. Or maybe I won't touch the Base Fuel Table and just keep commanding richer until it stops misfiring, then let the Closed Loop control fix the table. Hmm...

  7. #7
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,376

    Default

    Quote Originally Posted by Cougar5.0 View Post
    I actually haven't touched the fuel map much so it's pretty smooth still.
    You don't know how smooth the Base Fuel Table is because the Learn Table values are directly applied to it. You have to Transfer Learning To Base, then look at the Fuel Graph. Read this thread! http://forums.holley.com/showthread....7370#post47370 (Closed Loop & Learn Table - Especially posts #2, #6 & #11.)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, 100HP progressive dry direct-port NOS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, 160A 3G alternator, Optima Red battery, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  8. #8
    Join Date
    Nov 2014
    Location
    Ont. Canada
    Posts
    1,345

    Default

    This is your Fuel Graph in VE form. You tell me if that looks smooth.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	Untitled.jpg 
Views:	33 
Size:	22.5 KB 
ID:	8558  

  9. #9
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    22,376

    Default

    Cougar5.0, read 4th & 5th paragraphs: http://forums.holley.com/showthread....2523#post62523 (Holley EFI Tuning Tips & Information)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: Dominator MPFI & DIS, 100HP progressive dry direct-port NOS, A/C, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, 160A 3G alternator, Optima Red battery, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  10. #10

    Default

    Yes, I realized after I posted that the table wasn't smooth due to "flashing back" the Learn Table to the Base Fuel table. I did figure out how to select just the area of concern (cruising RPM) and "Graph" them, then do the VE "Conversion". I even fixed a couple of "off" cells just because they were obviously off. Thanks to both of you for emphasizing this, I didn't realize how to zoom into a particular set of cells until y'all beat me over the head with it. Excellent, thanks! And yeah, I'm done with transfer and smooth, I may never Transfer the Learn Table again, at some point it only serves to potentially create issues.

    But, back to what I was saying above, it seemed pointless to smooth a whole table that was dealing with a misfire on tip-in that was causing false Closed Loop corrections (ECU thinks it's lean when it isn't.) So, I did the later thing I suggested, I enriched the Target AFR to 13:1 in the entire cruising region, then I ignored the suggestion to adjust the fuel table for the new targets. I did this because the table was too rich in this area due to adding fuel based on false lean AFR readings. I then cleared the Learn Table without writing to fuel table (lots of fuel would've been added just where I didn't want it.)

    It worked! The Closed Loop compensation barely goes negative on tip-in and the "bounce back" correction when the RPM starts to increase is also minimal. The "larger overlap cam" misfires are now small enough that they aren't noticeably upsetting the Closed Loop compensation. Now I'm looking for spots where the correction is more than 3-4%. In the 1st case I looked at, it was indeed caused by a "dent" in my otherwise smooth ribbon (the area I looked at was only 2 cells wide by 8 tall.)

    The car feels much smoother on tip-in, even at lower RPM and in higher gears. The Target and actual AFR track surprisingly well now so I feel like I made it over a hump here and can hopefully continue to fine tune from here. Thanks again for all the help Danny & TransAm.


    Edit - I added before and after plots here to make it clearer what I'm saying here:

    Click image for larger version. 

Name:	before.jpg 
Views:	12 
Size:	67.8 KB 
ID:	8561Click image for larger version. 

Name:	after.jpg 
Views:	9 
Size:	68.9 KB 
ID:	8562
    Last edited by Cougar5.0; 08-11-2019 at 09:11 AM. Reason: Add before and after plots

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
About us
Holley has been the undisputed leader in fuel systems for over 100 years. Holley carburetors have powered every NASCAR® Sprint® Cup team and nearly every NHRA® Pro–Stock champion for four decades. Now, Holley EFI is dominating the performance world as well as our products for GM's LS engine. Holley's products also include performance fuel pumps, intake manifolds & engine dress–up products for street performance, race and marine applications. As a single solution, or partnered with products from other Holley companies - Hooker Headers, Flowtech Headers, NOS Nitrous, Weiand, Earl's Performance Plumbing, or Diablosport - Holley products can give you the edge you need over the competition.
Join us