PotM GrandMarq.NET - Panther Headquarters Forum Index PotM
GMN Chat Room GMN's STORE!! GMN's Gallery Please!!
Results 1 to 11 of 11

Thread: 2.25" H-pipe Restriction?

  1. #1
    P31 Pursuit Car Brown_Muscle's Avatar
    Join Date
    Jan 2008
    Location
    New Jersey
    Posts
    3,232

    Default 2.25" H-pipe Restriction?

    There seems to be a lot of misinformation online... I currently have a stock 2.25" catted mustang h-pipe on my vehicle. My 351w should be pushing 375-400hp at the crank (trying to be conservative). How restrictive is my h-pipe compared to a 2.5 catted pipe? I do feel its lacking in the upper top end (above 5000rpm), but the cam should still have plenty of power up that high, so that's why i'm wondering if the pipe is holding me back.
    -Phil



    +1982 Ford LTD-S Police Car. Built 351w, Trickflow 11R 190 Heads, Edelbrock 1906 Carb+ RPM Intake, WR-AOD, Full exhaust headers to tails. 3.27 Trac-Lok Rear. Aluminum Police Driveshaft. Speedway Springs+Bilstein Shocks, Intermediate Brakes, HPP Steering Box.

    +2003 Acura CL Type S 6-speed

  2. #2
    Beater gonna beat sly's Avatar
    Join Date
    Mar 2010
    Location
    Lewisville, TX
    Posts
    22,723

    Default

    Check the bends. Typically the restriction is in the over axle bends that really crimp down the pipes to as small as 1.5 inch in diameter in the middle of the bend. That may be your biggest issue. If everything is mandrel bends, you should be fine and need to check cat/muffler flow next. You may need to go 2.5 inch to get more out of the top end, but I imagine there's other spots to look first. The H-pipe shouldn't be a restriction point unless it's made wrong.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  3. #3
    I'm an air-conditioned gypsy gadget73's Avatar
    Join Date
    Jan 2005
    Posts
    40,983

    Default

    yes, that. The corkscrew over the back axle is likely way more of a choke point than another 1/4" of H pipe would be.

    if you want to know for sure, a pressure gauge plumbed into one of the O2 bungs would tell you. If the exhaust is a choke point it will show on the gauge. Won't tell you where the restriction is, just that there is one.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  4. #4
    GMN Regular DerekTheGreat's Avatar
    Join Date
    Sep 2014
    Location
    Warren, MI
    Posts
    6,646

    Default

    I'd step up to a 3". I believe Engine Masters did an episode on exhausts and if I remember right, even the turd engine benefitted from a 3" exhaust. The ole "You want some restriction or you lose bottom end" argument was invalidated.
    1985 LTD Crown Victoria - SOLD
    1988 Town Car Signature - Current Party Barge

  5. #5
    I'm an air-conditioned gypsy gadget73's Avatar
    Join Date
    Jan 2005
    Posts
    40,983

    Default

    the more practical concern is just one of space and ability to bend pipes. Most places can't do 3", and if they kink-bend it, fair chance the actual flow ability is going to be less than a mandrel bent pipe of a smaller diameter.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  6. #6
    P31 Pursuit Car Brown_Muscle's Avatar
    Join Date
    Jan 2008
    Location
    New Jersey
    Posts
    3,232

    Default

    the bends on the h-pipe are extremely good, I don't think they were madrel bent, but there's really no kinking/downsizing from the bends. The mufflers are super-turbo's, which are the freest flowing quietest mufflers you can get (engine masters did a segment with them as well, and they flowed as well as a straight pipe). I'd also prefer not to go 3" because I'm trying to keep it as quiet as possible, so if 2.5" will do it, that's fine by me. Perhaps that cats are the restriction at these power levels, The pressure gauge would definitely provide some interesting data
    -Phil



    +1982 Ford LTD-S Police Car. Built 351w, Trickflow 11R 190 Heads, Edelbrock 1906 Carb+ RPM Intake, WR-AOD, Full exhaust headers to tails. 3.27 Trac-Lok Rear. Aluminum Police Driveshaft. Speedway Springs+Bilstein Shocks, Intermediate Brakes, HPP Steering Box.

    +2003 Acura CL Type S 6-speed

  7. #7
    Beater gonna beat sly's Avatar
    Join Date
    Mar 2010
    Location
    Lewisville, TX
    Posts
    22,723

    Default

    How are the bends over the axle or do you have the exhaust dumped at the mufflers? the 2.25 inch pipes on my 93 are crinkle bent over the axle and pinch down to just over 1.5 inches at one point.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  8. #8
    P31 Pursuit Car Brown_Muscle's Avatar
    Join Date
    Jan 2008
    Location
    New Jersey
    Posts
    3,232

    Default

    The rest of the exhaust is all 2.5", save for the h-pipe. The Bends over the exhaust are mandrel bent, impala tailpipes, so basically no restrictions there, although they are getting up there in age at this point. I remember my stock tailpipes were so tiny, bent and restrictive it was laughable
    -Phil



    +1982 Ford LTD-S Police Car. Built 351w, Trickflow 11R 190 Heads, Edelbrock 1906 Carb+ RPM Intake, WR-AOD, Full exhaust headers to tails. 3.27 Trac-Lok Rear. Aluminum Police Driveshaft. Speedway Springs+Bilstein Shocks, Intermediate Brakes, HPP Steering Box.

    +2003 Acura CL Type S 6-speed

  9. #9
    Beater gonna beat sly's Avatar
    Join Date
    Mar 2010
    Location
    Lewisville, TX
    Posts
    22,723

    Default

    hmm... Yeah... then the only thing I can think is intake, cats, headers, or maybe just needing the 2.5 treatment on the H-pipe. I know the tails and manifolds are the restriction on mine. If I put headers and mandrel tails, I would probably need 24# injectors to keep from leaning stuff out. My intake may also be a restriction. It's not much larger than stock but the MAF is now matched to the intake tube instead of being half an inch smaller.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  10. #10
    I post a lot...
    Join Date
    Dec 2011
    Location
    Yonkers NY
    Posts
    4,481

    Default

    Here is a random table which makes me feel good cause I thought I remembered anything near 400 hp needing a larger exhaust. Mostly i remember when deciding what exhaust to put in old wagon my research showed 2.25 was plenty for my goals as I never even conceived of getting into the high 300's.

    So 2.5" it is Also if I remember right diameter was more important at the front with the hotter gases having higher volume.

    https://m.roadkillcustoms.com/determ...t-tubing-size/
    Last edited by jaywish; 01-09-2022 at 01:47 AM.
    03 Marauder DBP, HS, 6disk, Organizer Mods> LED's in & Out, M&Z rear control arms, Oil deflector, Blue Fuzzy Dice
    02 SL500 Silver Arrow
    08 TC Signature Limited, HID's Mods>235/55-17 Z rated Cooper Zeon RS3-A, Addco 1" rear Sway, Posi, Compustar Remote Start, floor liners, trunk organizer, Winter=05 Mustang GT rims, Nokian Hakkapeliitta R-2 235/55-17
    08 Escape Limited V6 Auto, Beamtech LED headlight bulbs,

  11. #11
    P31 Pursuit Car Brown_Muscle's Avatar
    Join Date
    Jan 2008
    Location
    New Jersey
    Posts
    3,232

    Default

    That makes sense Jason, its not a huge deal, but when it rots out, makes sense to go bigger. I fully support you upgrading the headers, tails, and injectors

    That's a nice little chart Jay, according to the first, i'm undersized, according to the second I'm right at the limit of my exhaust.
    -Phil



    +1982 Ford LTD-S Police Car. Built 351w, Trickflow 11R 190 Heads, Edelbrock 1906 Carb+ RPM Intake, WR-AOD, Full exhaust headers to tails. 3.27 Trac-Lok Rear. Aluminum Police Driveshaft. Speedway Springs+Bilstein Shocks, Intermediate Brakes, HPP Steering Box.

    +2003 Acura CL Type S 6-speed

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
GMN Approved Links!


www.rockauto.com www.adtr.net