O2 dump kicks in but not out?

[I-luv-em-all]

I am having a little bit of an issue. I have RnR 3" external dump o2 housing. Whenever I spool the turbo fully the o2 dump kicks in like it should, but then when I let off the gas, and then get back on the gas, the exhaust is still coming out of the external dump. it takes about 3-5 seconds to go back though the muffler like it should. Any ideas what this could be caused by?

Since it is winter I have the BC cranked all the way to minus, could that be blocking too much flow for the waste gate or something?

 

[PSI NRG]

Its probably because you have the boost turned down so low. A wastegate opens to keep boost at a stable level and vent off un-needed exhaust gases. So if you have the boost set so low that the wastegate is staying open as soon as any kind of serious exhaust flow is going through the turbo that would explain why its not going through the muffler. I'm still confused on how you know its not going through the muffler? And why turn the boost down so low because its winter?


The lower you turn the boost controler the earlier the waste gate opens
The higher your turn up the boost controler the later the waste gate opens

Keep that in mind.

 

[I-luv-em-all]

I have an O2 dump thats how I can tell that is not going through the muffler, because after I let of the gas the waste gate stays open, and I can tell because it is very loud, and coming from under the hood.

And I understand how a wastegate works and what it is for.

The reason I have the boost really low is because I just blew the HG, so I am taking it easy on it for a while. Even though the colder air, will be better for everything anyway.

But I did turn the boost up and the wastegate is again working properly.

 

[DSM007]

sir...please park the car and drain the oil now and fix the HG,a blown head gasket allows coolant into the oil in the engine,it will displace the oil away from the bearings when the car is sitting and will start to CORRODE the bearings and damage them...otherwise if you dont....your looking at a total engine rebuild due to rod knock,not a head gasket replacement.

 

[PSI NRG]

First things first replace your head gasket asap. Thats not something you want to drive around on not matter how low you turn the boost down.

From reading your profile you didnt list an upraded turbo, so regaurdless a t25 with an 02 dump is going to be loud. The turbo is so small and it builds boost quickly that even if you let off the gas and the second you hit the gas again the turbo is gunna spool right back up. Small turbos with 02 dumps are always going to be loud cause even under monderate throttle you can spool the turbo to full boost so the waste gate is open much of the time. I'm pretty sure everything is in working order. If you dont want your car to be so loud change out your 02 housing for something the recirculates back into the downpipe and save your 02 dump until you have a larger turbo or run more boost. Otherwise fix the HG and everything should be fine. I dont see a problem otherwise that needs to be fixed.

 

[I-luv-em-all]

Sorry, I should have been more clear, I blew it, and of course got it replaced. No damage done. New HG, oil, antifreeze, arp head studs, T-stat, exhaust gaskets, the works. I was taking it easy because I didnt want to blow it again.

Also first gen DSM's do not have the T-25's, only 95 and up (2G)'s did. My car is a 1992 with a TD05-H Mitsubishi turbo.

I fixed the probelm, it was just my BC turned basically off, I turned it to about 14 psi for now, and it is working fine.

 

[oldman]

Which mbc do you have? Sounds like your wastegate pressure relief hole on the mbc isn't doing its job causing pressure to be trapped between the mbc and wastegate after letting off.

 

[PSI NRG]

Its either a t25 or a 14b bottom line is its small and builds boost quickly.

 

[oldman]

Its either a t25 or a 14b bottom line is its small and builds boost quickly.

Why does the size of your turbo and how fast it spools has anything to do with the wastegate staying open after letting off? How does one build boost quickly if the wastegate stays open?