Guest nicksri Posted January 13, 2006 Share Posted January 13, 2006 My second turbo does not kick in when it is supposed to at around 4K rpm. I have a Greddy electronic boost gauge and I have around 0.7 bar of boost before 4K rpm and the pressure gradually dropped to 0.4 bar after that. I did the TTC to troubleshoot the problem using Andrew Petrie’s method (http://mkiv.supras.org.nz/articles/andy.htm), but the problem is still there. Therefore, I tried another TTC using Randy Dellinger’s method (http://www.mkiv.com/techarticles/ttc/ttc.htm) by wiring IACV and EGCV actuators open at all time. This worked. Both turbos came on-line at the same time and pulled hard at around 3500 rpm, so I put everything back into standard and checked all the hoses. They are all OK. I then disconnected the hose that runs from IACV VSV to IACV and plugged in the hose that goes to the boost sensor to check for pressure. I drove and boosted the car and there was no pressure. I then disconnected the hose that comes from the pressure tank to IACV VSV and plugged in the hose that goes to the boost sensor and went for a drive. There was also no pressure. I put everything back and disconnected the hose that goes from the intake to the pressure tank lower port at the pressure tank side and extended this hose to connect at the boost sensor and went for a drive. There was boost pressure. I put the hose back and took out the hose from the upper port and connected the hose that goes to the boost sensor to this upper port and went for a drive. There was no pressure after a boost. I can then conclude that there is pressure coming in the pressure tank but there is no pressure coming out to push open the IACV and EGCV. Before I go out and try to find the pressure tank replacement, I want to make sure that the tank is really bad. Is there anyone happen to have the diagram or instruction on how to check the pressure tank operation to make sure that it is bad? I actually tried disconnecting the hose from the lower port of the pressure tank and connecting it to the upper port and connected the lower port to the boost sensor and went for a drive. There was a boost pressure coming out from the lower port and it was pressurized!!! I am confused. Thanks in advance for any help. Link to comment Share on other sites More sharing options...
Ian C Posted January 13, 2006 Share Posted January 13, 2006 That's a fantastic bit of fault diagnosis you've done With the pressure tank plumbed in the "wrong" way round did it store any pressure? It really sounds like a failed tank though, and there are a few people over here that are experiencing late second turbo problems which seems like it could be the pressure tank not holding any pressure, so, hopefully someone will fix this issue (Heckler? Soop Dogg? ) once and for all and report back on it. -Ian Link to comment Share on other sites More sharing options...
supRo Posted January 13, 2006 Share Posted January 13, 2006 Hi, I have had same problem. Everything was checked out - Hoses, actuators, wastegate, VSV's. In the end it was indeed the pressure tank. Here's a secondhand tank for sale if it helps: http://www.mkivsupra.net/vbb/showthread.php?t=53685&highlight=pressure+tank Edit to say, When the problem occurs, If you drop a gear or two and floor it (manual gearbox!) does the second turbo kick in? Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 13, 2006 Share Posted January 13, 2006 nicksri: Has the engine been out, or the head been off, or any small hoses changed for (say) blue *hit? Link to comment Share on other sites More sharing options...
Guest nicksri Posted January 13, 2006 Share Posted January 13, 2006 With the pressure tank plumbed in the wrong way round, it did store pressure. This is why I am not sure whether the wrong way round is actually the right way. I bought the car used and everything is standard. There has been no modification. I have been driving the car like this since I bought it about a year ago thinking that this is how it is supposed to be. After I tried my friend's car (also standard), I then realized that there was something wrong with my car as I could feel the second turbo kicking in when I drove my friend's car, but not mine. I looked at all the hoses and they are standard from the factory. There is no blue hose or other colored hose. I think it is not likely that the hoses were connected to the pressure tank incorrectly from beginning, but there is still a slight chance. It is why I want to see a diagram or instruction on how to check the pressure tank operation. Then, I can be completely sure. I did further diagnosis. After I plumbed the pressure tank the wrong way round and realized that it hold pressure after a boost, I then left the hoses incorrectly connected to the pressure tank and disconnected the hose going from the IACV VSV to IACV actuator from the VSV side and connected the hose that goes to the boost sensor and went for a spin. The boost gauge shew no boost and no vacuum at idle and it shew no boost until around 4K rpm when the needle swing right to around 0.6 bar and stayed there until I lifted my foot off throttle. It went back to 0 a few seconds after I lifted my foot off the pedal. This means there is pressure coming from the pressure tank and the IACV VSV is working properly to hold the pressure up until 4K rpm when it is pulsed open by ECU to allow pressure to go through. I did the same experiment with the EGCV VSV and the result was the same. Then, I put everything back as original except for the wrong plumbing at the pressure tank and went for a spin hoping that the sequential system will work, but the response got worse. The car boosted to 0.7 bar up until around 4K rpm and the boost suddenly dropped to nearly 0.1 bar. What went wrong? I kept trying. I did the TTC again using Andrew Petrie’s method (http://mkiv.supras.org.nz/articles/andy.htm), and went for a drive. The result was very satisfactory. The two turbos came on-line at the same time. The IACV and the EGCV actuators were kept open by the pressurized air from the pressure tank. After I shut down the engine, I took a look at both actuators and they were still open. I disconnected the hose and the pressurized air hissed off and the metal rod on the actuators moved back to the closed position. I then left the EGCV connection as it is in the TTC and put the hoses back to original at the IACV and went for a drive. The car did not boost well at low rpm and pulled up strong when the IACV opened at 4K rpm. I then disconnected the hose from the EGCV actuator to leave it close at all time and went for another spin. The car boosted well at low rpm up to 0.7 bar and suddenly dropped to nearly 0.1 bar when the IACV opened at 4k rpm (the same feeling as when I put it in sequential system with the wrong plumbing at the pressure tank). This should mean that when I put it in sequential system with the wrong plumbing at the tank, the IACV opened at 4k rpm, but the EGCV did not open. Can anyone tell me why? I will get a used pressure tank to try with the correct connection next week and will see what happened. Till then, I am on TTC which gives very impressive power delivery from just below 4K rpm up. If I can fix this, I will try eTTC so that I can choose between going quietly (sequential) or louder (TTC). By the way, my original problem is that the second turbo does not kick in at all because of a possible bad pressure tank. The boost went from 0.7 bar at around 2K rpm to around 0.4 bar at higher rpm. If the IACV and the EGCV do not open, I wonder where the boost was gone. The #1 turbo should be able to keep on boosting by itself to the wastegate limit of 0.7 bar, but the boost dropped at higher rpm. If the second turbo kicks in late, it should be the EBV problem where it does not open to prespool the second turbo. Link to comment Share on other sites More sharing options...
Ian C Posted January 13, 2006 Share Posted January 13, 2006 I don't know if you've had a look at this article yet but it describes the "boost dropping off when #2 turbo should come on line" problem... If you are running on turbo 1 only due to a sequential fault then boost will indeed fall off as the poor blighter can't flow enough air up top at all - that's why there are two of them. If it falls suddenly to about 0 or 0.2bar at 400rpm then the EGCV isn't opening, but is it tails off as you get higher up the rpm range then I'd say the IACV isn't opening. Have you tried the tinfoil method to see if the actuators are moving? Fold up a strip of tinfoil so it's long and thin and wedge one end firmly between the actuator and it's stop. Go for a spirited drive. If the tinfoil has gone when you get back, the actuator opened -Ian Link to comment Share on other sites More sharing options...
Steve Posted January 13, 2006 Share Posted January 13, 2006 Shall keep an eye on this thread. I seem to be getting the same problem. Doesn't happen all the time but ocassionally the second turbo comes in late (5000rpm) or sometimes not at all. Maybe its time for the single!! Link to comment Share on other sites More sharing options...
Guest nicksri Posted January 14, 2006 Share Posted January 14, 2006 Thanks Ian. A very smart way to test whether the actuator is open or not. I thought of a similar way but could not figure out what material to use. Tin foil!!! Brilliant. Thanks. I will try it later today. I already looked at the article before I posted. That is why it made me curious how anyone can get 0.8 bar of boost at 5K rpm from #1 turbo without the second one kicking in. Mine gradually dropped from just above 4K rpm to 0.4 bar at 6800 rpm. When I plumbed the pressure tank the wrong way, I am sure the IACV is open while the EGCV is closed because the pressure suddenly dropped from 0.7 bar to around 0.2 bar at just above 4K rpm and never picked up even at 6800 rpm. I will use the tin foil method to confirm my thought. Now I really want to know whether the upper port of the pressure tank is the pressure in port or the pressure out port. Link to comment Share on other sites More sharing options...
Guest nicksri Posted January 17, 2006 Share Posted January 17, 2006 I already checked whether the IACV and the EGCV actuators opened or not at 4K rpm. I have a boost gauge and an EBC that can read boost pressure. I connected the hose from the the boost pressure sensor to the hose that goes from the IACV VSV to the IACV actuator using a T. I did the same with the EBC connecting it to the hose between the EGCV VSV and the actuator. I can then check to see whether there is any pressure to open the actuators at 4K rpm. I did get a reading of around 0.5 bar from the EGCV at around 4K and also around 0.5 bar from the IACV right after the EGCV is opened. This means they both opened. However, I still have the boost drop problem dropping to 0.3 bar at 4K rpm right when both actuators opened. I wondered where the boost pressure went. I noticed that if I immediately lifted off the throttle when the pressure dropped and floored it right back, I got the full boost pressure. I did the TTC again afterward and I got full boost at 0.85 bar without any drop. What could be the problems? Link to comment Share on other sites More sharing options...
Guest hemogoblin Posted October 1, 2007 Share Posted October 1, 2007 Great thread on the seq system. Im having almost the same exact problem, #2 comes on late, and sometimes not at all. Andys TTC method didnt work, but wiring up the actuators (mkiv.net) worked. Im hoping its not a pressure tank issue, did this ever get resolved? Link to comment Share on other sites More sharing options...
flyby Posted October 17, 2007 Share Posted October 17, 2007 did anyone fix this problem, as i got the same http://www.mkivsupra.net/vbb/showthread.php?t=117820 Link to comment Share on other sites More sharing options...
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