Strange Boost Pattern And Late Transition
12-03-2002, 08:03 PM
#21
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Originally Posted by P'cola FD' date='Dec 3 2002, 08:48 PM
I would recommend not checking your vacuum chamber with a pump, but rather checking the entire system by "T"ing into the line Rusty is talking about, starting the car for long enough to build a vacuum, and then turning the car off. If you lose much vacuum at all, no matter how long the car has been sitting, then you have a leak. That leak could be your problem.
Rusty
12-04-2002, 09:01 AM
#22
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Originally Posted by P'cola FD' date='Dec 3 2002, 05:48 PM
I don't think that the CCV will open unless there is boost on the back side of it. I could be wrong, but I "think" that for it to open, there has to be equal boost pressure on both of its nipples. And I "think" that its other nipple gets boost from the secondary turbo. I would recommend not checking your vacuum chamber with a pump, but rather checking the entire system by "T"ing into the line Rusty is talking about, starting the car for long enough to build a vacuum, and then turning the car off. If you lose much vacuum at all, no matter how long the car has been sitting, then you have a leak. That leak could be your problem.
I like that vacuum test. Not only does it test the entire system but it is also very easy to do
Thanks P'cola FD and 13brv
by the way, I have a thread going on rx7club about how the boost gauge (and the boost itself) is affected by altitude. This may partially explain some of my strange boost pattern, but I haven't entirely figured it out yet. The thread is here:
http://www.rx7club.com/forum/showthread.ph...threadid=137455
12-04-2002, 11:42 AM
#23
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I found some info that refers to transition at 5500rpm!
At the boost control section of Rob Robinette's site:
http://www.rx7turboturbo.com/robrobinette/.../boost_note.htm
It says that the manual suggests transition occurs at 5500rpm under lite load. Maybe my problem is that the ECU thinks load is light. Does anyone know where in the manual it says this; I'd really like to read it first-hand.
How does the ECU know that load is light? Does it compare throttle position and rpm?
At the boost control section of Rob Robinette's site:
http://www.rx7turboturbo.com/robrobinette/.../boost_note.htm
It says that the manual suggests transition occurs at 5500rpm under lite load. Maybe my problem is that the ECU thinks load is light. Does anyone know where in the manual it says this; I'd really like to read it first-hand.
How does the ECU know that load is light? Does it compare throttle position and rpm?
12-04-2002, 01:48 PM
#24
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I think that if your ecu thought the engine was under light load, then it would be running on the fuel maps for light load. And if it were running on the wrong maps, you would be worried about a lot more than just boost problems right now.
I'm really starting to think you are having a TCA problem. Check the vacuum chamber's storage, the operation of the TCA, and "T" into the lines going to the TCA when it stops snowing. I think your problem may lie therein.
I'm really starting to think you are having a TCA problem. Check the vacuum chamber's storage, the operation of the TCA, and "T" into the lines going to the TCA when it stops snowing. I think your problem may lie therein.
12-04-2002, 02:39 PM
#25
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Originally Posted by P'cola FD' date='Dec 4 2002, 11:48 AM
I think that if your ecu thought the engine was under light load, then it would be running on the fuel maps for light load. And if it were running on the wrong maps, you would be worried about a lot more than just boost problems right now.
Agreed. It's just that the whole 5500 thing is really bugging me.
Originally Posted by P'cola FD' date='Dec 4 2002, 11:48 AM
I'm really starting to think you are having a TCA problem. Check the vacuum chamber's storage, the operation of the TCA, and "T" into the lines going to the TCA when it stops snowing. I think your problem may lie therein.
I will do what I can tonight in the garage, and I'll do the running tests as soon as the weather will allow.
Man, it's really good to have people to bounce ideas off of; keeps me from wasting hours (days?) chasing my ***.
12-05-2002, 08:15 AM
#26
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The vacuum system is fine. I hooked a vacuum pump to the hose on the front side of the check valve and the system held 15inHg steady for over 5 minutes. I also checked the check valve.
I checked the TCA by hooking a pump to it's hose in the rats nest. It worked fine (watched it move from under the car when the pressure was released). I think the only actuator I have not yet checked is the wastegate.
It may be a while before I can do any running tests due to the weather. I'll revive this thread and describe the results when I get them.
Thanks everyone.
I checked the TCA by hooking a pump to it's hose in the rats nest. It worked fine (watched it move from under the car when the pressure was released). I think the only actuator I have not yet checked is the wastegate.
It may be a while before I can do any running tests due to the weather. I'll revive this thread and describe the results when I get them.
Thanks everyone.
12-06-2002, 03:31 PM
#28
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Ok, today was my day off, and the roads were dry 
.
T'd into TCA (at the hose in the rats nest). Here's what I get:
<3500rpm: 15"Hg
between 3500 and 5200rpm: 0psi
>5200rpm: 7psi
I'm not sure about the change at 3500rpm. Can anyone shed any light? (Does one solenoid click at 3500 and the other at 5200?) Is it supposed to do that? 7psi should be enough to open the TCA (which I checked the other day - see post above), so the secondary turbo should be seeing exhaust (albeit a little late at 5200rpm!).
I then T'd into the CCA (also at the rats nest, just off the solenoid). Here's what I got:
<5000rpm: 0psi
>5000rpm: 6.5psi
This should also be enough to open the CCA: Thus, I should be getting compressed air from the secondary. Note that the 5000rpm in this test was distinctly different from the 5200 of the TCA test, implying that the CCA opens slightly before the TCA. I guess this is normal? Either way it doesn't seem like a problem.
These results seem to point to the CRV as the reason for my low secondary boost; maybe it's staying open or something. I'll T into that next (when the car is cool).
Still no clue as to the late transition. Any ideas?
By the way, I also hooked the boost gauge back up to the UIM and when for a final run, just to make sure my boost pattern was the same: it was the same (13psi, dropping to 10 by transition at 5500rpm, 5psi at transition, and 6psi to redline)
What do you guys think?
T'd into TCA (at the hose in the rats nest). Here's what I get:
<3500rpm: 15"Hg
between 3500 and 5200rpm: 0psi
>5200rpm: 7psi
I'm not sure about the change at 3500rpm. Can anyone shed any light? (Does one solenoid click at 3500 and the other at 5200?) Is it supposed to do that? 7psi should be enough to open the TCA (which I checked the other day - see post above), so the secondary turbo should be seeing exhaust (albeit a little late at 5200rpm!).
I then T'd into the CCA (also at the rats nest, just off the solenoid). Here's what I got:
<5000rpm: 0psi
>5000rpm: 6.5psi
This should also be enough to open the CCA: Thus, I should be getting compressed air from the secondary. Note that the 5000rpm in this test was distinctly different from the 5200 of the TCA test, implying that the CCA opens slightly before the TCA. I guess this is normal? Either way it doesn't seem like a problem.
These results seem to point to the CRV as the reason for my low secondary boost; maybe it's staying open or something. I'll T into that next (when the car is cool).
Still no clue as to the late transition. Any ideas?
By the way, I also hooked the boost gauge back up to the UIM and when for a final run, just to make sure my boost pattern was the same: it was the same (13psi, dropping to 10 by transition at 5500rpm, 5psi at transition, and 6psi to redline)
What do you guys think?
12-06-2002, 04:13 PM
#29
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Oops!!!!
I'm really sorry, but I had a brain fart on that previous post. Everywhere that I say CCA I should have said CRV.
So, the two tests I just did was the turbo control actuator (TCA) and the charge relief valve (CRV).
Now, if I'm not mistaken (and I probably am) doesn't the CRV need a vacuum to open? It's only getting 0psi when it needs to open (before transition, right?). I need to double check. I have all the info, I just need to look at it. Maybe this is my problem (or one of them at least).
Sorry I'm making such a mess here. In a hurry to do as much as I can before it gets dark.
I'm really sorry, but I had a brain fart on that previous post. Everywhere that I say CCA I should have said CRV.
So, the two tests I just did was the turbo control actuator (TCA) and the charge relief valve (CRV).
Now, if I'm not mistaken (and I probably am) doesn't the CRV need a vacuum to open? It's only getting 0psi when it needs to open (before transition, right?). I need to double check. I have all the info, I just need to look at it. Maybe this is my problem (or one of them at least).
Sorry I'm making such a mess here. In a hurry to do as much as I can before it gets dark.
12-06-2002, 04:53 PM
#30
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Which TCA solenoid line did you "T" into? There are two. One attached to the ACV for vacuum, and one in the rack for pressure. They should both switch over at 4,500 rpm. If they aren't, then I'd try checking the solenoid's vacuum/pressure source. If that looks good, then it may be related to your ecu or wiring. This is pretty wierd.