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Thread: Help with Rotrex lack of boost

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    Help with Rotrex lack of boost

    Hey guys, looking for some help from anyone with experience with a rotrex setup. I have a simple k20a2 with minor bolt ons and a c38-81 running 138mm stock crank pulley and 90mm blower pulley. I'm tuning as we speak and everything was going great up until 5500rpm. By that point I was reaching 8.7psi and all was peachy. The next map I start losing boost as the rpm rose, it would drop to 5.6psi by 6500, then levels back up to 7psi until 8000rpm. I have the TTS billet bracket with additional idler pulley to give the blower 270 degrees of belt wrap. I am running the stock tensioner. I have a Tial Q BOV and a Tial MVR with a 4 port MAC solenoid controlling boost. At this point in tuning the BCS is deactivated, and the wastegate is welded on backwards to a typical turbo setup meaning the compressed air is blowing keeping the valve shut (meaning the boost can't be creeping out the wastegate unless its told to). Also the fact that I can build almost 9psi then all of a sudden it drops makes me think its not a leaking charge pipe. Has anyone here experienced belt slip? That's the only thing I can imagine is happening but its strange since the OEM tensioner is reading normal and the belts taught and is fine until 5500rpm. I know that was a bit of a rant but I like details when I'm trying to help someone so guess its a habit. Seen alot of builds on this site for a long time and love them all. Cheers guys and thanks in advance for any help.

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    Quote Originally Posted by 04carboncivic View Post
    Hey guys, looking for some help from anyone with experience with a rotrex setup. I have a simple k20a2 with minor bolt ons and a c38-81 running 138mm stock crank pulley and 90mm blower pulley. I'm tuning as we speak and everything was going great up until 5500rpm. By that point I was reaching 8.7psi and all was peachy. The next map I start losing boost as the rpm rose, it would drop to 5.6psi by 6500, then levels back up to 7psi until 8000rpm. I have the TTS billet bracket with additional idler pulley to give the blower 270 degrees of belt wrap. I am running the stock tensioner. I have a Tial Q BOV and a Tial MVR with a 4 port MAC solenoid controlling boost. At this point in tuning the BCS is deactivated, and the wastegate is welded on backwards to a typical turbo setup meaning the compressed air is blowing keeping the valve shut (meaning the boost can't be creeping out the wastegate unless its told to). Also the fact that I can build almost 9psi then all of a sudden it drops makes me think its not a leaking charge pipe. Has anyone here experienced belt slip? That's the only thing I can imagine is happening but its strange since the OEM tensioner is reading normal and the belts taught and is fine until 5500rpm. I know that was a bit of a rant but I like details when I'm trying to help someone so guess its a habit. Seen alot of builds on this site for a long time and love them all. Cheers guys and thanks in advance for any help.
    It could be a leak somewhere... Just a small one that doesn't show its face till 9 psi, then it drops, then the charger catches up again, then it drops again. Not saying it's definitely that, but I wouldn't make any assumptions yet.

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    Help with Rotrex lack of boost

    That's a good call. Guess Ill pressure test the whole system first before trying to diagnose everything at once haha. I have one coupler I can bet if it's leaking, it's leaking from that. Cheers!

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    Good luck!

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    Re: Help with Rotrex lack of boost

    I know jaydee had abswered you back on k20a but do you have a grouo of photos we could see of the setup? Close up of the belt as well. You can try simply things like belt dressing to see if that takes car of slip if thats your issue. Perhaps that belt tensioner mod jaydee did may help as well being factory tension was ok to moderate but a little extra was needed.

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    Help with Rotrex lack of boost

    Hey sorry for the delay. Ill grab a couple photos in the morning, but I'm ruling out belt slip as of now, since I was so excited/nervous during street pulls for the Etune, my ears were missing the super loud sound of boost leaking lol. I'm 99% positive now my BOV is leaking due to the distance it is from the throttle body so I'm going to get it moved and hopefully that fixes my problem. I went to do a leak down tonight but was parked on the street and didn't have a jack or anything and couldn't get the air chuck to get on the valve great so said fuck it, I'm confident in how I out on the rubber connectors on the charge piping. Thanks for the reply guys

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    Not sure how the bov's distance from the throttle body would cause it to leak...

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    Help with Rotrex lack of boost

    I'm pretty bad at explaining this, but since I'm running a -2psi spring in the tial q, my guess would be when the high cams roll on, the motor is essentially taking a deeper breathe and lowering the pressure at the manifold, so now the blower/charge piping where the BOV is, is at 10psi but the high cams may drop the pressure at the manifold to 8psi and the pressure in the charge pipes being just greater enough to crack open the valve. This is all I can think of for now but it makes sense in my head. It always happens at my vtec point and never before that even though I get up to 9psi then it cracks, then all of a sudden at 7000 you can hear the leak just stop entirely and the boost shoots back up then leaks again, so it seems like the BOV or wastegate opening, but can't be the wastegate since I have it mounted backward so the pressure is holding the valve shut and the boost solenoid isn't activated at this point in tuning. I'm going to post a pic of the bay to show what I mean for my placement. Also mind the piping lol long story, but it stays until my next upgrade.


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    I ran into this similar issue this July during a race. We checked everything for leaks but nothing. It turned out to be the Bypass valve sticking open and not creating any boost. I ordered a replacement and works perfect again. I asked the company if they have had any issues with the kits bypass valve and they said I was the first.

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