Problem with my Hahn Turbo Intake Plenum

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  • I finally got around to installing the DDMWorks Map Sensor clip and in the process of doing so, I managed to bump my intake plenum. I was surprised to see it literally pop off the throttle body (TB). Before installing my Hahn turbo kit, I had a Hahn CAI and when I went to remove it as part of my turbo install, I noticed that my TB had some wear on it from the CAI intake plenum, so I guess the TB wore some more over time. When I initially installed the turbo system, I used a thin metal-cutting jigsaw blade in my Rockwell X2 Bladerunner to enlarge the gap in the clamping ring in hopes of getting a tighter seal, but with the wear shown, it looks like the clamp is too loose even under full clamping pressure, so I guess I may need to increase the gap in the clamp so I can get a tighter fit.

    I had been wondering why my Boost gauge was typically showing boost pressures of 3 psi or less and I guess the worn fit between the TB and the intake plenum was allowing leakage and keeping my boost levels down.

    I've already emailed Hahn Racecraft for advice, but I was wondering if anybody else has experienced anything similar?

    I guess worst case, I need to replace the TB and probably the Intake Plenum clamp ring, O-ring and the spacer sleeve that holds the O-ring in the right spot. I also wonder if there is any sealer I could use to better seal the intake plenum/TB joint since that would be a lot easier and cheaper fix than replacing everything with new components.

    Other than the lower levels of boost I've been seeing, the engine runs fine and still seems to have plenty of pep when accelerating, but now that I know I have a poor air seal at the plenum/TB, I feel the need to improve that situation.

    Edited once, last by BKL ().

  • Update - I reinstalled the plenum back on the TB, but when I went for a short test ride, at around 2.5 psi boost, the plenum popped off the TB, hitting the hood with a noise!

    As the attached pic shows, the clamping ring that secures the plenum to the TB has a gap that allows the clamping ring to be tightened against the TB.

    I'm thinking about enlarging the gap by running it past a metal cutting jigsaw blade mounted in my Rockwell X2 Bladerunner (basically a vertically mounted jigsaw) to hopefully increase the gap and provide more clamping pressure to secure the plenum to the TB.

    An o-ring at the top of the compression sleeve is supposed to form a seal between the plenum and the TB, but the o-ring appears to have come off somehow, so I'm considering using some RectorSeal T Plus 2 Sealant/pipe dope (…Plus-2-Sealant/1000092785), which is not supposed to harden and is pressure rated for up to 2000 psi when used on threaded connections. Since I would not be using the sealant on a threaded connection and would basically be using the sealant as a gap filler in a compressed fit, I thought I'd post here for some opinions. I have ordered some parts so I can try to adapt a silicone cobra head elbow to connect the intake piping to the TB, but I really don't wait the 3-7 days until the parts come in before I can next drive my Slingshot.;) I'm also considering Permatex The Right Stuff Gasket maker since it's listed as Blowout resistant, although I'm not sure about this application other than the sealant would be clamped in the same sense that bolts clamp oilpans, etc.


    Edited once, last by BKL ().

  • Did the o-ring come off twice? It's missing in your first post too.

    No. I reused the photo with a new orientation. I can only assume the o-ring t came off when I initially bumped the plenum when installing the MAP Sensor clip or it may have self-destructed while the plenum was wearing the top of the TB and may have gotten broken and maybe blown out from between the TB and plenum or gotten sucked into the intake.

    My big concern is not getting a tight seal against the TB and the plenum popping off the TB, causing total loss of boost.

    Bill Hahn, jr., emailed me that he was concerned the intake pipe from the intercooler might not connect properly to the cobra head elbow since the pipe doesn't connect to the middle of the plenum as the cobra head elbow expects, but I think the 22 degree elbow and the short length of 3" x 4" aluminum pipe will allow me to get everything lined up.

    I just want to try and get back on the road and not have to wait until the parts get delivered. Bill also said he was looking at an alternative and should have something a in a couple weeks or so.

  • I can get you a new o-ring if you need one/ Just PM me your mailing info

    Thanks, but I think my problems involve more than that.

    I had a Hahn CAI before I installed my Hahn Stage 2 turbo kit and I must have done something wrong when I installed the CAI because I noticed when installing the turbo that the plenum wasn't seated parallel with the TB shoulder and had worn the TB so that the plenum wasn't seating properly. I thought I had fixed it when I broadened the gap in the clamping ring for additional pressure, but evidently it continued to wear against the TB and now the plenum's clamping ring doesn't tighten enough against the TB to keep it from popping off.

    As I posted earlier, I had contacted Bill Hahn, jr, about possibly needing a new compression sleeve that fits around the TB, along with an o-ring and asked him about needing to replace the TB due to the wear and he replied he thought I might not need to replace the TB and that he was working on a new design to secure the plenum to the TB.

    In the meantime, I have ordered a cobra head elbow designed for boosted applications, along with some other components that should hopefully let me line everything up until Bill releases his new solution. Here's a pic of the pieces I think will fix my problem -

    I just want to ride my Slingshot now instead of waiting.:) I might have already gotten a spare o-ring from Hahn Racecraft, but finding anything in the mess of my garage can be difficult. Thanks again for the offer.

  • Update - As I posted in Post # 1, my Hahn turbo intake plenum has worn the top of my Throttle Body TB) and no longer fits tightly, having pooped off during my test ride after trying to tighten the plenum-TB connection once boost went over about 2.5 psi. It turns out that when the plenum popped off the TB, the compression ring that holds the o-ring at the right position for a tight seal popped off the TB when the plenum popped loose.*

    The parts I ordered (Post # 6) to try a fix arrived Monday and today I put everything together as the following pics show -

    Hahn originally used a grommet fit into a 11/16" hole to hold the Air Intake Temp Sensor in the plenum via a friction fit, so I thought I'd do the same, but while drilling the hole for the grommet in the silicone Cobra Head elbow, I realized the Cobra Head silicone was too thick for the grommet to fit. I ended up pushing the Air Intake temp Sensor into the hole I'd originally intended for the grommet and it seems to fit reasonably tight, but I have a little concern as to whether or not the friction fit will hold once boost (under 7 psi) gets applied. The sensor feels about as tight in the silicone as it did in the plenum or the original stock intake tubing, but I'm wondering if I should use some sensor-safe silicone gasket material such as one of these products from Permatex -**

    The original Hahn aluminum charge tubing had beaded ends for a more secure connection, but since Han tube I shortened and the connecting tube I used are non-beaded, straight pipe ends, I will be replacing the screw-based stainless pipe clamps I currently use with T-bolt clamps which clamp over a little wider area, hopefully providing a better seal between the aluminum tubing and the silicone elbows.

    I'm anxious to try a test ride, but would appreciate any community feedback on the need for/use of the silicone gasket sealer between the Air Intake Temp Sensor and the Silicone Cobra Head elbow before I go for a test ride. Hopefully I can wait long enough for some feedback before I try the test ride!:D

    * I realized during my second test ride the next day that I hadn't lost the compression ring that positions he o-ring. I had removed it when the plenum popped off the TB and placed the compression ring over my shift handle.

    ** I have no idea what impact on engine performance would be if the air intake temp sensor were to get blown out, but I think I'd rather use some silicone sealant tha risk finding out.

    Edited once, last by BKL ().

  • Took the Slingshot out for a short 10 mile or so test ride. I now have enough boost to easily break away the rear Achilles ATR Sport 2 305/30R18 tire. IIRC, the Hahn Stage 2 kit should generate around a max of 7 psi or so and I got it up to 6.5 psi w/o blowing the Air intake Temperature Sensor out of the hole I drilled in the silicone Cobra Head intake elbow. I also stopped by Auto Zone and took piccs of the different gasket sealants they carry so I can research a little more in case I decide to use some silicone gasketing to help ensure the Air Intake Temperature Sensor's friction fit stays in the intake boot.

    Update - I went for an extended test ride of about 100 miles late this evening. During the test ride, I stopped several times after some heavy boost runs to check the fit of the Air Intake Temperature Sensor into the elbow. According to my Innovate SCG-1 AFR/Boost gauge, I hit boost pressures as high as 7.4 psi (once) and around 6.4-6.7 psi several times. So far, the sensor has stayed securely in its hole in the elbow, but I may still try to better secure it in place. See the attached picture -

    After I see how the sensor works in its current hole in the elbow over the next week or so, I'll make a decision on how to better secure the sensor in place. I also have the option of buying a new Cobra Head elbow and drilling a smaller hole for a tighter friction fit between the sensor and the elbow.

    Overall, I'm very pleased with the performance of the new setup. I hadn't realized how much boost I had been losing and my Slingshot now feels like a new vehicle again!:thumbup::evil::thumbup:

    Edited 5 times, last by BKL ().

  • Just thought I'd provide a list of parts in case anyone wants to try using a silicone Cobra head elbow on their Hahn turbo setup. The Cobra Head elbow will also work on a DIY CAI, but will need some different aluminum tubing. See this TDS link about the DIY CAI -….5989/page-69#post-189205, Post # 819 or this TDS thread which provides several different approaches -…-intake.5326/#post-114668.

    Tips and parts list for the Turbo application -

    The throttle body has a 70 mm opening (2.75"), so if you use the ATP Cobra Head elbow, be sure to also order the 2.75" adapter designed for the 3" Cobra Head elbow -…IL-251&Category_Code=RUBB.

    I also used a 3" diameter x 4" long aluminum tube -…tubing-3-od-x-4-long.html, and a 22 degree, 3" diameter silicone elbow -…bow-3-id-x-22-degree.html.

    I also ordered a 4-pack of T-Bolt clamps (83-92 mm according to the listing, but actually marked 83-91 mm) from Amazon -

    A tip for fitting the Cobra Head elbow to the TB - You may want to trim about 1/4" off the bottom of the elbow where it connects to the TB, if you have clearance issues with the hood rubbing against the top of the Cobra Head elbow. I haven't done this yet and I have some rubbing, so it looks like I'll either need to remove some materiel from the hood ribs, shorten the CH elbow where it attaches to the TB or both. See pic -

    Edited once, last by BKL ().

  • Follow-up on using the ATP Cobra Head elbow - The throttle body normally has a rim along the top edge that was worn down due to me not properly installing the Hahn CAI/Turbo aluminum plenum, resulting in wear on the TB which now seems to be allowing the Cobra Head elbow to slip off the top of the TB due to the missing rim edge on the top of the TB. I originally tried using a T-bolt clamp, but I believe it actually exacerbates the sealing problem since it is a wider clamp, placing pressure along the top of the TB, even when the T-bolt clamp is as tight as possible. I'm hoping that using a regular screw-clamp that is a little narrower than the T-bolt clamp will place the clamping pressure below the top edge of the TB so that the Cobra Head elbow will remain in place under high boost.

    If the narrower clamp doesn't stop the elbow coming off under high boost, I guess I'll try replacing the TB with a new unit that still has the rim along the top of the TB throat.

    Polaris lists a new part number for the TB, but Googling either part number (new pn 12670836 or older pn 12632093) produces the same search results, with GM parts sources listing the TB for as low as the mid $80s compared to prices int he $120s from Polaris parts sources.

    Edited once, last by BKL ().