Page 3 of 5 FirstFirst 12345 LastLast
Results 21 to 30 of 47

Thread: Exhaust pops under acceleration.

  1. #21

    Default

    So I uploaded a known to be good Global File from last year. Still doing the same thing. Could it be possible that this is "normal" with the way my exhaust is run? I'll take a short video and try to post it here, if that's possible.

  2. #22
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,593

    Default

    Quote Originally Posted by Gaz64 View Post
    I can't see an exhaust system change causing this issue. But also, why would a tuning issue cause this? Have you had the spark plugs out for inspection?
    I don't think "normal" comes into it after an exhaust change.
    Regards, Gary

  3. #23

    Default

    So I have a strange update, wish I could post the videos I took. I mounted the camera in the car, on the rear bumper, and under the car near the mufflers. Watching the videos in the car you can clearly hear the popping/backfiring, like something is wrong. The videos from outside the car (bumper & under car) have NO unusual sounds! Made about half a dozen videos, all are the same & consistent.

    I was NOT expecting this, it appears to be some sort of acoustic vibration that's getting amplified inside the car. If I can't hear it at either tailpipe, my only conclusion is that there's nothing wrong with the engine or tune, right? I'm a little embarrassed, but I'll try some sound deadening.

  4. #24

    Default

    Well, I've been chasing this issue all summer. The sound deadening did not get rid of the issue. I replaced the muffler, added an H-pipe, but the sound persists. Sounds different with the H-pipe, but still there. Swapped plugs & wires side-to-side (less than 4000 miles on everything). Watching the AFR on the Holley touchscreen (driver side) and the stand-alone wideband O2 (pass side) they both seem steady. If there's a misfire wouldn't they pick that up?

  5. #25
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,109

    Default

    Maybe it's not an EFI issue. Often times a valvetrain issue gets overlooked. I'd first perform a compression test. If any cylinder is suspicious, then perform a cylinder leak-down test to determine the problem.

    Perform a compression test (LINK), and if necessary, a cylinder leak-down test (LINK) too.
    A compression test determines if there's a problem, and a cylinder leak-down test determines what the problem is.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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, 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.

  6. #26

    Default

    OK I'll try that, though it's a pretty new crate engine, I guess anything is possible. Just can't seem to think of a good way to diagnose it.

  7. #27

    Default

    I also should have asked what's the best way to crank an EFI engine over while doing a compression test? Just pull the main power to the ECU?

  8. #28
    Join Date
    Dec 2009
    Location
    Connecticut
    Posts
    23,109

    Default

    If you're working alone, use a remote starter switch (LINK) to jump the starter to crank the engine. You can leave the ignition switch off.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 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, 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.

  9. #29

    Default

    So I did a compression test, all cylinders 200-220 psi. Changed plugs, wires, tested, same thing. Opened a known good V2 Global File in V5, no change. Tried to make AFR richer across the board, then leaner. Still the same issue. Had a mechanic ride with me and he's puzzled too. My next try will be chopping off the Borlas and trying another muffler.

  10. #30

    Default

    Cut off Borlas & added Magnaflows. No change, maybe even worse. The only other thing I did is update from V2 to V5. I compared the Global Files from V2 to V5, and see really no difference. Could something happen from going to V5?

    I may have not been totally clear, and there are three pages of posts here so here is the bottom line:
    Prior to 10/2018 the car ran great, no popping with Holley V2 & Magnaflow mufflers.
    After 10/2018 updated to Holley V5 & made several changes to the car's suspension as well as welding in a roll bar over the winter.
    Disconnected all ECU wiring while this was done. Suspension changes meant the exhaust had to change. So out came the Magnaflows & H-pipe, in went Borlas.
    Completed in spring 2019 when the exhaust popping was noticed.

Page 3 of 5 FirstFirst 12345 LastLast

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