Weird Boost Issue
10-07-04, 02:19 PM
#16
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First time I've looked at this thread but it sounds to me like the turbos are not always switching properly from parallel back to sequential during decel. I think you are completely right with it being some sort of turbo control actuator or door problem. I wouldn't bother hunting anything else as I think you've covered it all.
The only thing I can think of would be to disconnect the TCA from its door. Then you could wire the door open, make certain the car performs consistently and then wire it closed while making certain the car behaves consistently. Of course the boost will not function correctly but if the results are consistently repetitive in their respective case I would say it's safe to insist the problem is either the door or its control system. If the results with the door wired open/closed don't stay consistently repetitive you know you're fighting something else.
The only thing I can think of would be to disconnect the TCA from its door. Then you could wire the door open, make certain the car performs consistently and then wire it closed while making certain the car behaves consistently. Of course the boost will not function correctly but if the results are consistently repetitive in their respective case I would say it's safe to insist the problem is either the door or its control system. If the results with the door wired open/closed don't stay consistently repetitive you know you're fighting something else.
Last edited by DamonB; 10-07-04 at 02:22 PM.
10-07-04, 03:54 PM
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Originally Posted by DamonB
First time I've looked at this thread but it sounds to me like the turbos are not always switching properly from parallel back to sequential during decel. I think you are completely right with it being some sort of turbo control actuator or door problem. I wouldn't bother hunting anything else as I think you've covered it all.
The only thing I can think of would be to disconnect the TCA from its door. Then you could wire the door open, make certain the car performs consistently and then wire it closed while making certain the car behaves consistently. Of course the boost will not function correctly but if the results are consistently repetitive in their respective case I would say it's safe to insist the problem is either the door or its control system. If the results with the door wired open/closed don't stay consistently repetitive you know you're fighting something else.
The only thing I can think of would be to disconnect the TCA from its door. Then you could wire the door open, make certain the car performs consistently and then wire it closed while making certain the car behaves consistently. Of course the boost will not function correctly but if the results are consistently repetitive in their respective case I would say it's safe to insist the problem is either the door or its control system. If the results with the door wired open/closed don't stay consistently repetitive you know you're fighting something else.
I've replaced the TCA with a new one and when I did it the door appeared fine. But doesn't the TCA stay open all the time in a non-seq system? If so then even if it stays open I should be able to get my boost back. I have a feeling its something with the pre-control/wastegate solenoids or something with the pressure/vacuum there. I might have to T into those. And does anyone know why there is a vacuum point connected to that area? Is it to offset the pressure that the lines from the motor are generating? To me that area is the most confusing section of them all. I want to know how it works.
I was thinking that maybe its electrical but my problem is too consistant to be electrical I think so I am steering away from that.
10-08-04, 01:28 AM
#18
don't race, don't need to
If I got it right, there isn't really a vacuum or pressure control on the wastegate, unlike the controls that actuate the turbo control, charge relief valve, charge control actuator, and of course other things as well such as secondary air source routing and control (air pump and related errata). Rather, the pressure from the turbo output is routed from the nipple on the side of the primary turbo outlet (just under the air pump), through the wastegate actuator, then through the soft line to the relevant hard line that goes up behind the air pump, then turns to a soft line that attaches to the wastegate control solenoid. If you block one end of the wastegate actuator and blow in the other, the actuator pulls the rod in, which would open the wastegate on our turbos (and most others, I think). The ECU keeps the solenoid closed during pressured operation from the primary through 4500 rpm, then statrs opening and closing in the "duty cycle" mode to begin to modulate the wastegate actuator. As it opens and closes, the wastegate actuator responds by opening the wastegate. There is a restriction in this whole line to regulate the amount of pressurized air that passes through the line, thereby controlling the wastegate's effect. In the original turbos (early 93's), this restriction was from a little drilled slug of metal in the line right after the nipple, the so called "pill". Later turbos have the restrictor cast into the source nipple, necessitating a bit of drilling the allow finer regulation of wastegate actuation (read boost control). If there is too much pressurized air that can go through, the wastegate actuator opens the wastegate too far for a given amount of duty cycle at the wastegate control solenoid, resulting in less exhaust flow through the turbines, and therefore less turbo pressure. Likewise, restricting the pressurized air flow through this circuit (nipple to WG actuator, through hard line to solenoid, out of solenoid to vented air I believe) increases your boost by reducing the amount the WG opens for a given duty cycle.
The "Prespool" is really simply another wastegate, only rather than route the exhaust around the turbine to the regular exhaust (i.e. less exhaust to drive the turbo, so less pressure), the prespool routes its exhaust to the secondary turbo to begin spinning it . The principle of duty cycle regulation through restricted air flow from pressure source (litterally right next to the wastegate source) through the prespool actuator, through the hard line to the prespool solenoid, then to open air, is the same for both circuits. A pill or inline restrictor is also used.
I don't know if anyone put this site in here yet, but if you go to http://www.autosportracetech.com/RX-7/rx7stuff.htm you can find all sorts of neat stuff on turbo activities, including a really helpful cutaway diagram that shows the exhaust and intake paths.
I don't know if a stuck open prespool actuator would cause this in that it can be open and you still get primary boost (this is the case during transition at 4500 rpm, where you typically oinly drop to 8 psi from 10psi in the stock system), whereas the case described herein has zero boost until something "resets" below the point where the secondary system is activated at all. Not saying it isn't the problem, just that the deeper exhasut tone described indicates to me LARGE amounts of exhaust going where it shouldn't oughta..
That other post took me a day or so to figure out and write it all out to myself. I need to go through and play the mind game of "what if" for all the other possible scenarios to think if there is another route this could manifest. These turbos are actually part of why I bought the car. Secretly, I knida admire the engineers for dreaming up such a vastly complicated system to try and provide seamless boost from sequential small turbos. Masochistic and all that..
The "Prespool" is really simply another wastegate, only rather than route the exhaust around the turbine to the regular exhaust (i.e. less exhaust to drive the turbo, so less pressure), the prespool routes its exhaust to the secondary turbo to begin spinning it . The principle of duty cycle regulation through restricted air flow from pressure source (litterally right next to the wastegate source) through the prespool actuator, through the hard line to the prespool solenoid, then to open air, is the same for both circuits. A pill or inline restrictor is also used.
I don't know if anyone put this site in here yet, but if you go to http://www.autosportracetech.com/RX-7/rx7stuff.htm you can find all sorts of neat stuff on turbo activities, including a really helpful cutaway diagram that shows the exhaust and intake paths.
I don't know if a stuck open prespool actuator would cause this in that it can be open and you still get primary boost (this is the case during transition at 4500 rpm, where you typically oinly drop to 8 psi from 10psi in the stock system), whereas the case described herein has zero boost until something "resets" below the point where the secondary system is activated at all. Not saying it isn't the problem, just that the deeper exhasut tone described indicates to me LARGE amounts of exhaust going where it shouldn't oughta..
That other post took me a day or so to figure out and write it all out to myself. I need to go through and play the mind game of "what if" for all the other possible scenarios to think if there is another route this could manifest. These turbos are actually part of why I bought the car. Secretly, I knida admire the engineers for dreaming up such a vastly complicated system to try and provide seamless boost from sequential small turbos. Masochistic and all that..
Last edited by spurvo; 10-08-04 at 01:31 AM.
10-08-04, 08:01 AM
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I am pretty sure it is vaccum from the air-inlet of the primary turbo that connects to the little cylinder that also has the pre-control, wastegate, and the 2 nipples from the block that I assume could have vaccuum or pressure. That's kind of what is confusing me. Why should a hose that should always have vaccum be connected to that little metal cylinder when its pressure that is required to operate those two actuators? Unless it somehow offsets the pressure created by the two other nipples. On the Robinette vaccum diagram its the dark blue sections I am referring to. I have an understanding of how the actuators work I am just dumbfounded on the vacuum/pressure system related to these two soleiods.
But I agree with you. This seqential system lets me go play in the garage, gives me some time away from the wife.
But I agree with you. This seqential system lets me go play in the garage, gives me some time away from the wife.
10-09-04, 12:07 AM
#20
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Thread Starter
Ok, I worked on it again today and figured out what the problem is. But I still haven't fixed it.
Started out by re-checking the check valves for the vacuum and pressure tanks. In addition to vacuum testing them, as I'd done before, I also applied pressure to them. One (the vacuum tank valve) could only withstand about 10 psi of pressure, so I replaced it with a new one that would take 20 psi.... but I didn't think that was the problem and turns out it wasn't.
I checked the vent lines for the wastegate and pre-control solenoids (the lower nipples on each) to make sure they weren't blocked and holding pressure. They were fine.
I also checked the vent filters (the little round filters that are attached to the solenoids) on both turbo control solenoids to make sure they weren't blocked. They checked out ok.
Then I checked the adjustment on the Pre-Control and Turbo Control actuator rods. Both were OK.
Now here is where it gets interesting.
I bought a $20 web cam from CompUSA. It is crappy quality, but it has a built in white LED light and is USB and capable of 30 frames per second. The light was a plus (in a dark engine compartment) and I didn't want to risk my expensive ChaseCam if I didn't have to.... turns out that was a good idea (read on).
I placed the camera where I could see the Charge Control actuator and went for a test drive. It behaved exactly as it should, actuating at 4500 and turning off at 3000. I did quite a few runs and it worked perfectly every time.
Next, I placed the camera where I could see the Turbo Control actuator. I did a WOT run in second gear and the TC actuated at 4500 (as it should). Then I coasted back down to about 2800... TC stayed open, 2500 rpm, still open, put the clutch in and stopped. About the time I stopped it finally shut. I did several test runs and it behaved inconsistently every time. Sometimes it would slowly open after dropping below 3000, sometimes it wouldn't open at all, sometimes it wouldn't open until I hit 3500 or 4000 on the way back up during another WOT run.
Then the camera melted
I figured there was enough airflow down there to keep it from melting (guess I should have used that aluminum foil tip, Dgeesaman)
So the TC is the problem.
I hadn't checked the TC actuator while the car was hot ('cause I don't like being burned). So I checked it right after a few WOT runs. The vacuum and pressure lines for the TC run right behind the air pump and are pretty easy to get to there. I hooked my mity-vac up there and applied vacuum or pressure to the TC actuator and it worked perfectly every time. I thought about going ahead and replacing the TC actuator with a spare, but thought I would run another test first.
So, then I tee'd a vac/pressure gauge into the vacuum side of the TC actuator and went for a drive. It worked perfectly. At 4500 I would get vacuum on the gauge and at 3000, poof, the vacuum gauge dropped to zero.
Went back home and moved the gauge over to the pressure side of the TC actuator. The pressure side of the TC line is showing the same weird behavior that the video camera revealed. The pressure never left the line at 3000. Sometimes it stayed pressurized (TC open) through several runs, causing zero boost below 4500. Sometimes it releases after a few seconds, etc.
So.... something is keeping the pressure from leaving the TC actuator.
It can't be wiring because: Both turbo control solenoids are wired together to a single output on the ECU. Recall that the ECU grounds the solenoids to activate them. If one solenoid connection had a frayed wire that was grounding intermittently, it would also activate the other solenoid, which isn't happening. It can't be an ECU problem for the same reason. The ECU only has one wire to ground for both TC solenoids, so if it was keeping the solenoids activated, I would have also seen a problem in the vacuum TC solenoid.
I can't think of anything the TC actuator could do that would keep pressure in the line. When the pressure TC solenoid shuts off, it basically switches the TC actuator (pressure side) from being connected to the pressure tank to being connected to a vent to atmosphere (thus dumping the pressure from the line and shutting the TC door).
So, that leaves me with two possibilities. A) My replacement TC solenoid (pressure side) is also bad or B) I have a restriction in the line between the TC actuator and the TC solenoid.
I've tested the pressure TC solenoid several times (and replaced it once), but not when its really good and hot. It could be failing when it gets warmed up.
But I'm betting on option B. I think there is gunk (or something) in one of the steel pipes that connects the TC solenoid to the actuator. That would also explain why so many people have had this problem and replacing everything (solenoids, actuators, etc.) doesn't fix it.
I'll find out tomorrow and let you guys know. I'm going to check the steel pipes and clean them, or just bypass them completely with a long piece of hose. I will probably also replace the pressure side TC solenoid with a 3rd spare that I have.
Also, I can post those videos I made if anyone wants to see them. They are really poor quality, but all I needed to see was the actuator arm move.
- Dave Disney
Started out by re-checking the check valves for the vacuum and pressure tanks. In addition to vacuum testing them, as I'd done before, I also applied pressure to them. One (the vacuum tank valve) could only withstand about 10 psi of pressure, so I replaced it with a new one that would take 20 psi.... but I didn't think that was the problem and turns out it wasn't.
I checked the vent lines for the wastegate and pre-control solenoids (the lower nipples on each) to make sure they weren't blocked and holding pressure. They were fine.
I also checked the vent filters (the little round filters that are attached to the solenoids) on both turbo control solenoids to make sure they weren't blocked. They checked out ok.
Then I checked the adjustment on the Pre-Control and Turbo Control actuator rods. Both were OK.
Now here is where it gets interesting.
I bought a $20 web cam from CompUSA. It is crappy quality, but it has a built in white LED light and is USB and capable of 30 frames per second. The light was a plus (in a dark engine compartment) and I didn't want to risk my expensive ChaseCam if I didn't have to.... turns out that was a good idea (read on).
I placed the camera where I could see the Charge Control actuator and went for a test drive. It behaved exactly as it should, actuating at 4500 and turning off at 3000. I did quite a few runs and it worked perfectly every time.
Next, I placed the camera where I could see the Turbo Control actuator. I did a WOT run in second gear and the TC actuated at 4500 (as it should). Then I coasted back down to about 2800... TC stayed open, 2500 rpm, still open, put the clutch in and stopped. About the time I stopped it finally shut. I did several test runs and it behaved inconsistently every time. Sometimes it would slowly open after dropping below 3000, sometimes it wouldn't open at all, sometimes it wouldn't open until I hit 3500 or 4000 on the way back up during another WOT run.
Then the camera melted
I figured there was enough airflow down there to keep it from melting (guess I should have used that aluminum foil tip, Dgeesaman)So the TC is the problem.
I hadn't checked the TC actuator while the car was hot ('cause I don't like being burned
). So I checked it right after a few WOT runs. The vacuum and pressure lines for the TC run right behind the air pump and are pretty easy to get to there. I hooked my mity-vac up there and applied vacuum or pressure to the TC actuator and it worked perfectly every time. I thought about going ahead and replacing the TC actuator with a spare, but thought I would run another test first.So, then I tee'd a vac/pressure gauge into the vacuum side of the TC actuator and went for a drive. It worked perfectly. At 4500 I would get vacuum on the gauge and at 3000, poof, the vacuum gauge dropped to zero.
Went back home and moved the gauge over to the pressure side of the TC actuator. The pressure side of the TC line is showing the same weird behavior that the video camera revealed. The pressure never left the line at 3000. Sometimes it stayed pressurized (TC open) through several runs, causing zero boost below 4500. Sometimes it releases after a few seconds, etc.
So.... something is keeping the pressure from leaving the TC actuator.
It can't be wiring because: Both turbo control solenoids are wired together to a single output on the ECU. Recall that the ECU grounds the solenoids to activate them. If one solenoid connection had a frayed wire that was grounding intermittently, it would also activate the other solenoid, which isn't happening. It can't be an ECU problem for the same reason. The ECU only has one wire to ground for both TC solenoids, so if it was keeping the solenoids activated, I would have also seen a problem in the vacuum TC solenoid.
I can't think of anything the TC actuator could do that would keep pressure in the line. When the pressure TC solenoid shuts off, it basically switches the TC actuator (pressure side) from being connected to the pressure tank to being connected to a vent to atmosphere (thus dumping the pressure from the line and shutting the TC door).
So, that leaves me with two possibilities. A) My replacement TC solenoid (pressure side) is also bad or B) I have a restriction in the line between the TC actuator and the TC solenoid.
I've tested the pressure TC solenoid several times (and replaced it once), but not when its really good and hot. It could be failing when it gets warmed up.
But I'm betting on option B. I think there is gunk (or something) in one of the steel pipes that connects the TC solenoid to the actuator. That would also explain why so many people have had this problem and replacing everything (solenoids, actuators, etc.) doesn't fix it.
I'll find out tomorrow and let you guys know. I'm going to check the steel pipes and clean them, or just bypass them completely with a long piece of hose. I will probably also replace the pressure side TC solenoid with a 3rd spare that I have.
Also, I can post those videos I made if anyone wants to see them. They are really poor quality, but all I needed to see was the actuator arm move.
- Dave Disney
10-09-04, 01:02 PM
#21
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Fixed
I fixed mine this morning. And do I feel stupid. Hopefully the rest of you have the same problem so I won't feel as bad. But I had the pressure/vacuum hoses switched for the TCA. I have no idea how I had secondary boost the first try and then it fail. But anyway now I get it all the time and boy is it nice. Feels amazing. hehe
The area between the rats nest and the metal pipes by the airpump is where they weren't connected right. I went out with one T-ed and saw pressure and it appeared to work correctly in the sense of when it applied pressure and when it released it. Then I got under the car and applied pressure to that same hose with my mityvac and the arm never moved. So I tried vacuum. Then it moved and then I knew I F'ed up.
So go double check that.
But I had the pressure/vacuum hoses switched for the TCA. I have no idea how I had secondary boost the first try and then it fail. But anyway now I get it all the time and boy is it nice. Feels amazing. heheThe area between the rats nest and the metal pipes by the airpump is where they weren't connected right. I went out with one T-ed and saw pressure and it appeared to work correctly in the sense of when it applied pressure and when it released it. Then I got under the car and applied pressure to that same hose with my mityvac and the arm never moved. So I tried vacuum. Then it moved and then I knew I F'ed up.
So go double check that.
10-09-04, 01:29 PM
#22
Junior Member
Thread Starter
I fixed mine too.
It was the pressure side Turbo Control solenoid. The one I replaced it with was also bad.
Both the original solenoid and the replacment still pass Mazda's check procedure (in the shop manual) with flying colors.
But here is what's happening. There is a spring in the solenoid that returns the valve back to its initial position when the power source is removed from the solenoid. Over time, the heat weakens that spring and the pressure in the line between the solenoid and the turbo control valve holds the solenoid open (the spring cannot overcome the pressure). So, the pressure can't escape and the turbo control actuator is held open when it should not be.
The solenoid I had in the car couldn't take more than about 9 psi without sticking. The original solenoid in the car couldn't take more than about 11 (I'm running 12.5). I tested several spares I had and finally found one that was happy even at 15 psi. I put it in the car and went for a test drive..... car now performs perfectly and life is good
I can post a detailed test procedure for the solenoid valve if anyone is interested. You basically need to put 12v and a ground to the solenoid, then put pressure (about 12 psi to start) on the nipple that would go to the actuator and then remove the 12v and see if the solenoid lets the pressure in the line vent. If it doesn't (or is very slow doing it), then you have a problem. Let me know if anyone wants a nice how-to with pics. You have to test it as it is used in the car, the blow through test the shop manual outlines will not work with this solenoid. A very bad solenoid can still pass that test.
Thanks for all the troubleshooting help guys. My advice, if you're having the problems described above would be to buy a NEW pressure side Turbo Control solenoid.
- Dave Disney
It was the pressure side Turbo Control solenoid. The one I replaced it with was also bad.
Both the original solenoid and the replacment still pass Mazda's check procedure (in the shop manual) with flying colors.
But here is what's happening. There is a spring in the solenoid that returns the valve back to its initial position when the power source is removed from the solenoid. Over time, the heat weakens that spring and the pressure in the line between the solenoid and the turbo control valve holds the solenoid open (the spring cannot overcome the pressure). So, the pressure can't escape and the turbo control actuator is held open when it should not be.
The solenoid I had in the car couldn't take more than about 9 psi without sticking. The original solenoid in the car couldn't take more than about 11 (I'm running 12.5). I tested several spares I had and finally found one that was happy even at 15 psi. I put it in the car and went for a test drive..... car now performs perfectly and life is good
I can post a detailed test procedure for the solenoid valve if anyone is interested. You basically need to put 12v and a ground to the solenoid, then put pressure (about 12 psi to start) on the nipple that would go to the actuator and then remove the 12v and see if the solenoid lets the pressure in the line vent. If it doesn't (or is very slow doing it), then you have a problem. Let me know if anyone wants a nice how-to with pics. You have to test it as it is used in the car, the blow through test the shop manual outlines will not work with this solenoid. A very bad solenoid can still pass that test.
Thanks for all the troubleshooting help guys. My advice, if you're having the problems described above would be to buy a NEW pressure side Turbo Control solenoid.
- Dave Disney
Last edited by autoxer; 10-09-04 at 01:41 PM.
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kenpo2 (06-10-20)
10-09-04, 01:35 PM
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Great troubleshooting skills! While I don't have this problem, I learned a lot just reading about how you guys trace these problems down.
I'd love to see the videos, and a how to with pics would be great!
Congrats on finding the issue!
BTW, assuming a Mazda tech could have found this issue, what do you think the charge would be?
I'd love to see the videos, and a how to with pics would be great!
Congrats on finding the issue!
BTW, assuming a Mazda tech could have found this issue, what do you think the charge would be?
10-09-04, 01:38 PM
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Glad yours is fixed. I have a feeling my hoses were correct at one point and then sometime when I was tring to fix things they got swapped. I had to replace my TCA since the pressure side wasn't working and I bet I got those hoses mixed up before that and never thought to check it again.
I still don't understand how I got secondary boost with the hoses mixed up though. Makes no sense.
Anyway, I certainly wouldn't mind a nice write up of that testing procedure since I am sure I will need to use it at some point.
I still don't understand how I got secondary boost with the hoses mixed up though. Makes no sense.
Anyway, I certainly wouldn't mind a nice write up of that testing procedure since I am sure I will need to use it at some point.
10-09-04, 01:49 PM
#25
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Thread Starter
I'll post the videos and a solenoid check how-to in the next couple of days.
I worked on the car about 14 hours over about three different days. So, multiply that by their shop rate... probably seven or eight-hundred dollars by the time you factor in all the new parts they'd have put on the car trying to figure it out. I doubt they'd have ever figured it out though. Trying to even explain the problem to a regular shop mechanic would have been a nightmare.
I worked on the car about 14 hours over about three different days. So, multiply that by their shop rate... probably seven or eight-hundred dollars by the time you factor in all the new parts they'd have put on the car trying to figure it out. I doubt they'd have ever figured it out though. Trying to even explain the problem to a regular shop mechanic would have been a nightmare.
10-09-04, 02:49 PM
#26
Originally Posted by autoxer
Let me know if anyone wants a nice how-to with pics.
Here's the problem I am having... https://www.rx7club.com/3rd-generation-specific-1993-2002-16/sequential-problems-354409/
10-09-04, 11:14 PM
#27
don't race, don't need to
Glad that all worked out. So the actuator was sticking open like I thought, just not becauet the actuator was faulty, rather the solenoid. Need to move the rack off the engine, I think. Sigh... so much to do...
Good job guys!
Good job guys!
10-10-04, 09:52 AM
#28
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I just found this post this morning or I would have chimed in earlier.
Had the same problem TWICE. First time it was switched vacuum hoses like Arutha and a few months later a bad turbo control solenoid like Dave. These cars are often possessed.
Had the same problem TWICE. First time it was switched vacuum hoses like Arutha and a few months later a bad turbo control solenoid like Dave. These cars are often possessed.
Last edited by tcb100; 10-10-04 at 09:54 AM.
10-11-04, 07:43 AM
#29
Hmm... mine was working fine for a period of about three weeks after the '99 turbo install, then stopped after a oil pan reseal.. wonder if my lines are swapped, since you have to dislodge the TCA to do the pan... easy to try.
Originally Posted by arutha
I fixed mine this morning. And do I feel stupid. Hopefully the rest of you have the same problem so I won't feel as bad. But I had the pressure/vacuum hoses switched for the TCA. I have no idea how I had secondary boost the first try and then it fail. But anyway now I get it all the time and boy is it nice. Feels amazing. hehe
The area between the rats nest and the metal pipes by the airpump is where they weren't connected right. I went out with one T-ed and saw pressure and it appeared to work correctly in the sense of when it applied pressure and when it released it. Then I got under the car and applied pressure to that same hose with my mityvac and the arm never moved. So I tried vacuum. Then it moved and then I knew I F'ed up.
So go double check that.
But I had the pressure/vacuum hoses switched for the TCA. I have no idea how I had secondary boost the first try and then it fail. But anyway now I get it all the time and boy is it nice. Feels amazing. heheThe area between the rats nest and the metal pipes by the airpump is where they weren't connected right. I went out with one T-ed and saw pressure and it appeared to work correctly in the sense of when it applied pressure and when it released it. Then I got under the car and applied pressure to that same hose with my mityvac and the arm never moved. So I tried vacuum. Then it moved and then I knew I F'ed up.
So go double check that.
10-11-04, 07:47 AM
#30
Dave,
This is VERY curious. Where the replacement solonoids you used brand new? i do notice that the condition is worse at 14 psi than it is at 10. Seems to me that the "patch" fix that PFS tried a ling time ago involved a pressure regulator that essentially limited the pressure in the line to 9-10 psi. It sorta worked... i wonder if installing something that would limit the pressure the TCS(p) sees to 9-10 psi would help out. Would it need to see 14 psi to opperate correctly if you're running 14 psi boost, or would 9-10 always be sufficient to movbe the turbo actuator?
This is VERY curious. Where the replacement solonoids you used brand new? i do notice that the condition is worse at 14 psi than it is at 10. Seems to me that the "patch" fix that PFS tried a ling time ago involved a pressure regulator that essentially limited the pressure in the line to 9-10 psi. It sorta worked... i wonder if installing something that would limit the pressure the TCS(p) sees to 9-10 psi would help out. Would it need to see 14 psi to opperate correctly if you're running 14 psi boost, or would 9-10 always be sufficient to movbe the turbo actuator?
Originally Posted by autoxer
I fixed mine too.
It was the pressure side Turbo Control solenoid. The one I replaced it with was also bad.
Both the original solenoid and the replacment still pass Mazda's check procedure (in the shop manual) with flying colors.
But here is what's happening. There is a spring in the solenoid that returns the valve back to its initial position when the power source is removed from the solenoid. Over time, the heat weakens that spring and the pressure in the line between the solenoid and the turbo control valve holds the solenoid open (the spring cannot overcome the pressure). So, the pressure can't escape and the turbo control actuator is held open when it should not be.
The solenoid I had in the car couldn't take more than about 9 psi without sticking. The original solenoid in the car couldn't take more than about 11 (I'm running 12.5). I tested several spares I had and finally found one that was happy even at 15 psi. I put it in the car and went for a test drive..... car now performs perfectly and life is good
I can post a detailed test procedure for the solenoid valve if anyone is interested. You basically need to put 12v and a ground to the solenoid, then put pressure (about 12 psi to start) on the nipple that would go to the actuator and then remove the 12v and see if the solenoid lets the pressure in the line vent. If it doesn't (or is very slow doing it), then you have a problem. Let me know if anyone wants a nice how-to with pics. You have to test it as it is used in the car, the blow through test the shop manual outlines will not work with this solenoid. A very bad solenoid can still pass that test.
Thanks for all the troubleshooting help guys. My advice, if you're having the problems described above would be to buy a NEW pressure side Turbo Control solenoid.
- Dave Disney
It was the pressure side Turbo Control solenoid. The one I replaced it with was also bad.
Both the original solenoid and the replacment still pass Mazda's check procedure (in the shop manual) with flying colors.
But here is what's happening. There is a spring in the solenoid that returns the valve back to its initial position when the power source is removed from the solenoid. Over time, the heat weakens that spring and the pressure in the line between the solenoid and the turbo control valve holds the solenoid open (the spring cannot overcome the pressure). So, the pressure can't escape and the turbo control actuator is held open when it should not be.
The solenoid I had in the car couldn't take more than about 9 psi without sticking. The original solenoid in the car couldn't take more than about 11 (I'm running 12.5). I tested several spares I had and finally found one that was happy even at 15 psi. I put it in the car and went for a test drive..... car now performs perfectly and life is good
I can post a detailed test procedure for the solenoid valve if anyone is interested. You basically need to put 12v and a ground to the solenoid, then put pressure (about 12 psi to start) on the nipple that would go to the actuator and then remove the 12v and see if the solenoid lets the pressure in the line vent. If it doesn't (or is very slow doing it), then you have a problem. Let me know if anyone wants a nice how-to with pics. You have to test it as it is used in the car, the blow through test the shop manual outlines will not work with this solenoid. A very bad solenoid can still pass that test.
Thanks for all the troubleshooting help guys. My advice, if you're having the problems described above would be to buy a NEW pressure side Turbo Control solenoid.
- Dave Disney