Overboosting and no transition: problems with stock twin control
I went through something like this 6 years ago and wasted so much time diagnosing that I ended up buying all new solenoids, something like 7 or 8 at $50 a pop and like 10 of the check valves at like $10 each. And I made sure that the vaccuum lines were exactly as on the factory diagram. Never had issue after that.
I just got a chance to mess with the car this evening.
RECAP:
- i get good primary boost
- 4 psi WOT in neutral
- MBC on wastegate ONLY
- precontrol is still controlled by stock ECU
- my boost pattern is 10-5-8, so i get a large pressure drop at transition and it will not build full boost afterwards... would this indicate that the secondary is not producing any boost and the pressure is being fed back thru the secondary when the charge control actuator opens?
- i also sometimes have a hard time generating any boost pressure at all and the car feels sluggish
I switched the lines to the turbo control actuator and it caused no transition at all. I just switched it back after verifying that the lines were hooked up right to begin with:
I checked:
- pressure and vac resevoirs (good)
- put a mity vac on the turbo control and actuated it. (good)
- put vac guage on turbo control vac supply nipple under pressure tank. key on i got vac for a second then it switched it off.
- put pressure guage on turbo control pressure supply nipple under pressure tank. key on i got pressure for a second and it switched off.
each time i did key on key off i got pressure or vacuum reading for a second, then relay clicked and back to zero.
any suggestions? I'm considering going poor man's non-sequential for the time being.
RECAP:
- i get good primary boost
- 4 psi WOT in neutral
- MBC on wastegate ONLY
- precontrol is still controlled by stock ECU
- my boost pattern is 10-5-8, so i get a large pressure drop at transition and it will not build full boost afterwards... would this indicate that the secondary is not producing any boost and the pressure is being fed back thru the secondary when the charge control actuator opens?
- i also sometimes have a hard time generating any boost pressure at all and the car feels sluggish
I switched the lines to the turbo control actuator and it caused no transition at all. I just switched it back after verifying that the lines were hooked up right to begin with:
I checked:
- pressure and vac resevoirs (good)
- put a mity vac on the turbo control and actuated it. (good)
- put vac guage on turbo control vac supply nipple under pressure tank. key on i got vac for a second then it switched it off.
- put pressure guage on turbo control pressure supply nipple under pressure tank. key on i got pressure for a second and it switched off.
each time i did key on key off i got pressure or vacuum reading for a second, then relay clicked and back to zero.
any suggestions? I'm considering going poor man's non-sequential for the time being.
I haven't checked them since I put them on, but they are new viton check valves from dale clark. not very old or many miles.
ugh... i'm trying to avoid pulling off the uim again. I know the vacuum lines are right under there and new.
I have a PFS downpipe and stock main cat. I doubt it's clogged because it pulls really hard up to transition. When I said the car feels sluggish I meant every once in a while when I don't get boost. Feels like a boost leak that's not always there.
Today I swapped the connectors for the WG and precontrol solenoids, thinking they could have their lines switched and got no change...
Now, what exactly is the turbo control actuator supposed to do when you key on key off after a drive? Is it supposed to move all the way when you KOn and stay there until you KOff... just like the charge control actuator? Just move a little bit every time you key on?
I went through something like this 6 years ago and wasted so much time diagnosing that I ended up buying all new solenoids, something like 7 or 8 at $50 a pop and like 10 of the check valves at like $10 each. And I made sure that the vaccuum lines were exactly as on the factory diagram. Never had issue after that.
Today I swapped the connectors for the WG and precontrol solenoids, thinking they could have their lines switched and got no change...
Now, what exactly is the turbo control actuator supposed to do when you key on key off after a drive? Is it supposed to move all the way when you KOn and stay there until you KOff... just like the charge control actuator? Just move a little bit every time you key on?
Is it true that the precontrol actuator largely controls boost pressure before 4500 rpm? The troubleshooting guide states this...
If so, I've been trying to adjust the system *** backwards. I figured the wastegate controlled boost pressure all the time... maybe I just need a MBC on both actuators. I think I'll try that.
If so, I've been trying to adjust the system *** backwards. I figured the wastegate controlled boost pressure all the time... maybe I just need a MBC on both actuators. I think I'll try that.
Racecar - Formula 2000
Joined: Sep 2002
Posts: 4,033
Likes: 369
From: Bath, OH
Yes, that's true. Here are some threads with some useful related info on using dual ball/spring MBC's. This is the system I use, and it works great.
https://www.rx7club.com/showpost.php...6&postcount=10
https://www.rx7club.com/showpost.php...6&postcount=10
Full Member
Joined: Mar 2007
Posts: 57
Likes: 1
From: Redmond
sounds like a problem I couldn't figure out for the life of me. All hoses were connected, bought new solenoids, made sure that they were all getting the right voltage, but for whatever reason i could never hold pressure at 10lbs in the secondary. I'd be interested to know what you came up with.
Could it possibly be the Charge Solenoid, maybe it's not letting things open up once the secondary is pre-spooled...The issue with mine right now, is I get no secondary turbo at all. I'm trying to pinpoint that solenoid
The valve and actuator should be easily checked with a mity vac and the manual. You could put a mity vac on a long line to the supply lines to the actuators and see if they get good vacuum from their solenoids at transition.
Is it true that the precontrol actuator largely controls boost pressure before 4500 rpm? The troubleshooting guide states this...
If so, I've been trying to adjust the system *** backwards. I figured the wastegate controlled boost pressure all the time... maybe I just need a MBC on both actuators. I think I'll try that.
If so, I've been trying to adjust the system *** backwards. I figured the wastegate controlled boost pressure all the time... maybe I just need a MBC on both actuators. I think I'll try that.
I've found it's as easy as precontrol adjusts below transition, and wastegate adjusts above transtion. The settings of each relative to each other controls the shape of the transition dip/spike.
Dave
Dave
Racecar - Formula 2000
Joined: Sep 2002
Posts: 4,033
Likes: 369
From: Bath, OH
Exactly. That's why I run 2 ball-spring MBC's. One controls the PC actuator, and thus, the boost before transition, and the other controls the WG actuator, and, thus, the boost after transition. The lines from the actuators to the solenoids are blocked with solid (no holes) pills. I set the PC at 11 psi, and the WG at 10 psi to optimize the performance w/o fuel cut (stock ECU). See the chart below:
^ DaveW are you still using the stock ecu or do you have a PFC with that boost control setup?
nvm, read your post again .. <- slap me
anyway, I bet the turbos last longer at stock boost lvls ... ?
nvm, read your post again .. <- slap me
anyway, I bet the turbos last longer at stock boost lvls ... ?
I'm just waiting on another MBC. Pretty confident that will solve my problem.
Glad to have started a constructive conversation... seems like this isn't common knowledge for some reason. I misunderstood the boost control system entirely until I ran into this problem.
Why 11 psi and not leave it at stock 10?
Glad to have started a constructive conversation... seems like this isn't common knowledge for some reason. I misunderstood the boost control system entirely until I ran into this problem.
Exactly. That's why I run 2 ball-spring MBC's. One controls the PC actuator, and thus, the boost before transition, and the other controls the WG actuator, and, thus, the boost after transition. The lines from the actuators to the solenoids are blocked with solid (no holes) pills. I set the PC at 11 psi, and the WG at 10 psi to optimize the performance w/o fuel cut (stock ECU). See the chart below:
Racecar - Formula 2000
Joined: Sep 2002
Posts: 4,033
Likes: 369
From: Bath, OH
1. I'm just waiting on another MBC. Pretty confident that will solve my problem.
2. Glad to have started a constructive conversation... seems like this isn't common knowledge for some reason. I misunderstood the boost control system entirely until I ran into this problem.
3. Why 11 psi and not leave it at stock 10?
2. Glad to have started a constructive conversation... seems like this isn't common knowledge for some reason. I misunderstood the boost control system entirely until I ran into this problem.
3. Why 11 psi and not leave it at stock 10?
2. It originally took me about a month of reading posts and articles on boost control for the FD before I REALLY understood how it works, so I can easily understand how confusing it is.
3. Actually, the "stock 10" can be more or less than that depending on weather conditions, intake and exhaust flow mods, etc. Remember that there is no feedback with the stock boost "control" system. The stock "boost-control" relies on a predetermined map, and is not very good at actually "controlling" the boost.
I set the PC at 11 because (1) I can do so w/o fear of fuel cut, (2) 11 psi provides more power than 10, and (3) with my setup (see my signature) the 11 psi on the PC setting minimized the boost dip/spike at transition.
Last edited by DaveW; Oct 12, 2009 at 07:45 AM. Reason: More comments added
