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Thread: Blown Cadillac tuning assistance.

  1. #1

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    Hello. I'm green to the EFI world and have been manually tuning my engine. My combination is a Big Block Cadillac with 871 Blower. It's stumbling around 2000 RPM. I took a trip around the block and datalogged it. This stumble seems to be best represented at RTC 153.5 seconds through 155 seconds. During this time, the Overlay shows the cells used are mostly two cells, with a little overshadow of the two below them. When graphed, it looks pretty smooth, but it's only two blocks. The AFR looks really rich. Would leaning this out make the fuel flow smooth? Any help would be appreciated. Thank you.

    Here's the datalog. Thank you.
    Attached Files Attached Files

  2. #2

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    What is the point of having EFI if you don't use Closed Loop? Your AFR varies from in the 8s up to the 18s and it doesn't look like the system is ever in Closed Loop. No wonder it's stumbling. I'm surprised it even runs. Why doesn't it go into Closed Loop? Did you turn it off? What sort of EFI system are you using?

  3. #3

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    Yes, Closed Loop is turned off, because it's open header. I'm running a Hilborn 4 injector blower setup with the Holley HP. Is there a way to run Closed Loop and still keep the headers open? I thought the only way to run CL was to shield the WBO2 with the rest of the exhaust.

  4. #4
    Join Date
    Dec 2009
    Location
    Connecticut
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    Yes, manually tune the idle/off idle area of the Base Fuel Table if you're not allowing it to Closed Loop or Learn at idle. However, don't completely disable Closed Loop/Learn:
    http://forums.holley.com/showthread....ension-Harness (Read 2nd paragraph under "Wideband O2 Sensor Notes".)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 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 M/T Street Comp tires.

  5. #5

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    Quote Originally Posted by cadillac531 View Post
    Yes, Closed Loop is turned off, because it's open header. I'm running a Hilborn 4 injector blower setup with the Holley HP. Is there a way to run Closed Loop and still keep the headers open? I thought the only way to run CL was to shield the WBO2 with the rest of the exhaust.
    Okay, that helps explain things a little more. You can run a WBO2 sensor in open headers, but it won't work at idle or low speeds so you just turn it off below a set RPM point. When you do it that way you have to tune the idle area like you would a carb by manually adjusting the Base Fuel Table. For what you're trying to do you should give FAST Man EFI a call. Look at the pictures on his website and you'll get a feel for how people do this trick. He can help you out with a tune. Get some help before you damage an expensive engine.

  6. #6

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    Quote Originally Posted by Danny Cabral View Post
    Yes, manually tune the idle/off idle area of the Base Fuel Table if you're not allowing it to Closed Loop or Learn at idle. However, don't completely disable Closed Loop/Learn:
    http://forums.holley.com/showthread....ension-Harness (Read 2nd paragraph under "Wideband O2 Sensor Notes".)
    Thank you very much, Dannny! I didn't know I could do that. That sure will help a lot.

  7. #7

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    Quote Originally Posted by AndyF View Post
    Okay, that helps explain things a little more. You can run a WBO2 sensor in open headers, but it won't work at idle or low speeds so you just turn it off below a set RPM point. When you do it that way you have to tune the idle area like you would a carb by manually adjusting the Base Fuel Table. For what you're trying to do you should give FAST Man EFI a call. Look at the pictures on his website and you'll get a feel for how people do this trick. He can help you out with a tune. Get some help before you damage an expensive engine.
    OK, great to know. I didn't know I could turn it off under certain RPM. What do you think the computer would think is low speed? I idle around 1100. You think enabling Closed Loop at 1500 would be good?

  8. #8
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    25,560

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    http://forums.holley.com/showthread....ension-Harness (Read 2nd paragraph under "Wideband O2 Sensor Notes".)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 200A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/3000 RPM converter, B&M Hammer shifter, FPP aluminum driveshaft, FPP 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 M/T Street Comp tires.

  9. #9

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    1500 is probably too low for the wideband O2 to read correctly. You can figure this out by running the engine and watching the wideband while the engine is running. Outside air coming back up the exhaust makes the wideband O2 read lean. So at idle the wideband O2 will tell you that AFR is 16 or 17. At some point the wideband O2 readings will become correct. Could be 2000 RPM, could be 2500 RPM. Just try it and see. Go look at your Closed Loop settings in the EFI software and you'll see that you can control the RPM at which the wideband O2 turns on.

  10. #10

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    Quote Originally Posted by AndyF View Post
    1500 is probably too low for the wideband O2 to read correctly. You can figure this out by running the engine and watching the wideband while the engine is running. Outside air coming back up the exhaust makes the wideband O2 read lean. So at idle the wideband O2 will tell you that AFR is 16 or 17. At some point the wideband O2 readings will become correct. Could be 2000 RPM, could be 2500 RPM. Just try it and see. Go look at your Closed Loop settings in the EFI software and you'll see that you can control the RPM at which the wideband O2 turns on.
    OK, I'll mess with it. Thank you. I can see it reads super rich at the 2100 mark, so I know at that RPM range it seems to be reading properly. Thanks for the help.

    Quote Originally Posted by Danny Cabral View Post
    http://forums.holley.com/showthread....ension-Harness (Read 2nd paragraph under "Wideband O2 Sensor Notes".)
    Thank you.

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