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Exhaust Pipe Size? - Between Cat and Resonator

Discussion in 'Gen 2 Prius Main Forum' started by Tyler Wrage, Apr 29, 2021.

  1. Tyler Wrage

    Tyler Wrage Junior Member

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    TL;DR - what is the exhaust pipe size between cat and resonator? ID/OD, want to butt them together and clamp, preferably slide the pipes in the connecter, no welder access.

    Hey all, I recently bought an 07 hooptie Prius for 500 bucks with a dead hybrid battery from someone who didn't want to put money into it, and to my surprise, the car still had its original catalytic converters in it! Since I am trying to keep the car a low-buck deal (college student atm), I decided to sell the OE cats on ebay (sold yesterday, ($1969.99!) to fund the replacement of the hybrid battery, probably going GreenBean for the warranty. However, after I sawzalled the old cat out and went to install the aftermarket one, I realized I need a way to connect the new cat to the existing couple inch stub in front of the resonator, I thought the aftermarket cat would be flared to slide in. I used a janky caliper I have on the pipe and got neither 1-5/8 ID or 1-3/4 OD exactly, they were a good bit off from either measurement (I am an idiot and put them in a vice to trim and slightly egged them), and I cannot find any info online. I found a piece of exhaust from another project that seemed like I could slide over the Prius pipe, so I did so and clamped it, but the pipe I slid over is too large, and now I have an exhaust leak. The info I found online said the pipe was 1-5/8', but I can't seem to find a female/female slide-in connecter that small, is it 1-3/4? I just want to be able to slide the pipes together and clamp, I already trimmed both the new cat and stub off the resonator to slide my non-working pipe on... I could just take the cat with me 30ish miles to a parts store, but they often don't stock anything under 2" so I will likely have to get it online. Anyone who knows the appropriate connector size, please let me know! Also could get one of those flat clamp-over clamps, but can't seem to find any that small either. Thanks all! - Tyler.
     
  2. Too Many Cars

    Too Many Cars New Member

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    My cat's got stolen, and the thieves sawed it off right up to the resonator, leaving no pipe to connect to. Can you tell me what size the pop is that comes out of the resonator? ID and OD? Seem like when I crawled under there and measured it had a one and a half inch ID and best I could tell a 1.75 inch OD. So I'm going to have to weld on a piece of pipe to the resonator. I have an after-market on order and trying to determine what size the pipe is on that aftermarket Pat. Do you know what yours is? Thanks.
     
  3. TMR-JWAP

    TMR-JWAP Senior Member

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    Find a salvage yard with a Gen 2. Most likely they all have the cats removed, but you can typically purchase everything after the cat for about a dollar a foot, including the resonator. Just find one that had the cats removed and still has the pipe forward of the resonator. I've bought a handful like this. Makes it much easier for swapping out exhaust systems when I can have one already mocked up ready to go. I can get actual pipe dimensions and post them after I get back this afternoon.
     
  4. Tyler Wrage

    Tyler Wrage Junior Member

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    I went to my NAPA and ordered a 1-5/8 ID connecter, won't be here til Tuesday or so but I will reply back here if it fits so anyone looking in the future will know what to buy. Thanks!
     
  5. TMR-JWAP

    TMR-JWAP Senior Member

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    1.674-1.692" as measured around the entire outside diameter. I think 1 5/8" is going to be a bit too small, but any muffler shop can probably expand it.

    (~42.5 - 43 mm)
     
    #5 TMR-JWAP, Apr 30, 2021
    Last edited: Apr 30, 2021
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  6. Tyler Wrage

    Tyler Wrage Junior Member

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    Awesome, thanks for the measurement! I do have a cheap-o exhaust expander, so hopefully I will be able to make it work, if not, I will order a 1.75 and crank it down. I'll update the post when I get the 1-5/8" and see how it goes together.
     
  7. TMR-JWAP

    TMR-JWAP Senior Member

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    If it's one of those that has a threaded shaft down the center with 6 or 8 long metal pieces, don't waste your time trying to expand an exhaust pipe with it. You'll get way too frustrated. They're really only good for flattening out dents and similar stuff.
     
  8. Mendel Leisk

    Mendel Leisk Senior Member

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    that’s the number I got measuring my 3rd gen at reg pipe dia just downstream of last cat or whatever it is. Maybe 43.1~.

    92971446-327A-4646-A134-F1905B709EF1.jpeg
     
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  9. The Lizard King

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    If you don't live in CA or NY, I'd just buy an aftermarket whole system.

     
  10. Tyler Wrage

    Tyler Wrage Junior Member

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    Well, I got my 1-5/8 in today, it IS slightly too small - about the thickness of the pipe too small. Some hardcore persuasion would probably do it (or butt weld them), but I have a 1.75" connecter coming tomorrow, 95% sure that will do the trick. Will update once again once I get the 1.75 on and confirm for sure it's the correct size.
     
  11. Mendel Leisk

    Mendel Leisk Senior Member

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    43 mm translates to approx 1 11/16”.
     
  12. Paul Schenck

    Paul Schenck Active Member

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    I found The auto parts store has a bunch of adapters for tailpipes just take your parts and get what you need


    iPhone ?
     
  13. Tyler Wrage

    Tyler Wrage Junior Member

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    Hey all, just wanted to give my final update on the Prius exhaust. I purchased a 1.75"-1.75" connector, PN#41926, and it just slides over the stock pipe between cat and resonator nicely (maybe 1/16" of slop, about as good as you can hope for). However, for whatever reason, my aftermarket cat off ebay must use a slightly larger diameter pipe than the stock cat did, so the 1.75" didn't fit over it. I had to cut two slits in the connector with a sawzall, beat it on, and dig out the flux welder to weld the connecter and slits shut. Clamped the rear of the connecter to the piece of pipe before the resonator on the car, and I am in business! The aftermarket cat doesn't seem to muffle as well as the OE one (not surprisingly), but it doesn't seem like I have any audible/significant leaks. Another thing I do want to mention, if you are planning to replace your donut gasket between the manifold and cat inlet, DO NOT buy NAPA PN#31379. It is supposed to be the correct part, but the diameter of the thing is much too small. Thankfully my OE one doesn't seem to be leaking so I got by ok, but just wanted to save someone the frustration of parts chasing if they are doing something similar. If you are buying an ebay cat (assuming it is the same as the cheap one I purchased) and are wanting to do what I did, I would recommend an exhaust adapter from 1-7/8" (or whatever you can find that is slightly larger than 1.75to 1.75, these measurements are all in ID), assuming you don't want to cut slits and weld the thing like I did. Sure, the easiest thing to do would be take the aftermarket cat and a piece of the car's tubing to the parts store and smash exhaust adapters together until you find what you need, but if you live rurally like me and the parts store gets stuff like that in on order only, I hope this helped you out a bit. For anyone doing the job who is looking to get the O2 sensor out as well, it is a 22mm. Cheers!
     
  14. lunacyworks

    lunacyworks Member

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    I ordered a different donut but when arrived to pick it up the Napa store swapped it for 31379 and like you said it's about .100" to small and I had a hard time fit, and after it did seem to fit, it leaked. Not looking forward to taking everything off again. The good thing is I used U bolts before and now am going to use lap join band clamps instead since the Ubolts seemed to leak.
     
  15. Storm88000

    Storm88000 Active Member

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    Almost $2,000 for a couple cats from a 2009?! Wow. Did they contain more of the expensive metals back then? Thats cray
     
  16. lunacyworks

    lunacyworks Member

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    In our area in California, the dealers were quoting 3 months to get an OEM in stock at $2500. So $2k to get your car on the road today isn't so bad.
     
  17. wukinpanub

    wukinpanub Junior Member

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    My daughters each have Priuses. We just had a catalytic converter stolen. My plan is to put aftermarket cats on both Priuses. I will keep the OEM cat for when the aftermarket cats fail, or if we ever need to pass California emissions.

    I have searched the internet for a reducing lap band coupler. The after market catalytic converter I bought came with a 2" pipe. It is too big to clamp down with simple U-bolt exhaust clamps. (I don't know if I could make it airtight if I cut a couple of notches in the the larger pipe to help it cinch down.)

    I see reducing lap band couplers for 2.25" to 2", but nothing from 2" to 1.75".

    Autozone sells a 2" non-reducing coupler (Exhaust Pipe BRExhaust 265-827). I don't know if I could put some muffler tape on the outside of the stock 1 5/8" (or 42 mm) pipe to create enough space to make an airtight seal, or not.

    I'm trying to solve for simplicity here. I want to be able to drop out the aftermarket cat and replace it with the OEM cat (for the purposes of passing California smog; both my daughters live in Southern California), then put the aftermarket cat back in. I want it to be as easy as possible, not only for fewer points of possible failure, but also so my daughters' boyfriends can make the switch.

    Butt joints would be the easiest, because then I don't need to get any longitudinal distraction to slip one pipe over the other. But, since the pipes aren't presently the same diameter, I am worried about joining the butt ends with off-the-shelf parts.

    I could get reducing pipes (like from O'Reilly's, or Autozone). Ideally, I'd reduce both after market catalytic converters in a way that they will have the exact dimensions of the OEM catalytic converter when I cut it out. At that point, the junctions will all be 1.75" to 1.75" butt joints. (In other words, the reducing coupler will be "permanently attached" (though, not necessarily welded) to the after market cats.
    Providing I can find a 1.75" butt joint that will give me a proper seal, that might be the best compromise.

    Does anybody with real experience have wisdom to offer? Again, a 2" to 1 5/8" reducing lap joint band clamp is what I am after. But I can't seem to find it. Perhaps I am using the wrong search terms.

    Thanks for your help.
     
  18. wukinpanub

    wukinpanub Junior Member

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    Also, should I be using exhaust pipe sealer, or will that make it more difficult to undo?
     
  19. Storm88000

    Storm88000 Active Member

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    A friend has a 2012 Prius and his cat was stolen TWICE - he lives in San Francisco. He ended up buying some kind of "cage" for it when he replaced it the 3rd time. I'm not sure if "cage" is the correct term - but it was something around that made stealing the cat very very difficult and much more time consuming; so our fellow humans WHO ARE ACTIVELY TRYING TO MAKE THIS PLANET WORSE have a harder time doing so. OR, he says, will notice that it's protected and move onto another vehicle. I still can't believe people sometimes. Probably take it to some shady scrap metal guy and get a tiny fraction what it cost to replace and spend it on booze or whatever.
     
  20. alftoy

    alftoy Senior Member

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    Not sure how long the stub pipe remaining from the resonator is but you could try the exhaust pipe expander, rent borrow one from Advance or Pep Boys.


    Curious which aftermarket cat did you buy? The Autosaver88 from Amazon slides right on to the front pipe of the resonator.



    Another aftermarket cat on Amazon had the dimension chart.

    Another poster mentioning odd pipe size matching. Post #6 and #9

    Catalytic Converter Theft, Parts and Repair | PriusChat
     

    Attached Files:

    #20 alftoy, Jan 17, 2022
    Last edited: Jan 17, 2022