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So I just switched back to full stock boost control with the PFC and stock solenoids. Exact same behavior. If I set both primary and secondary to 1.1 bar and 80% duty I get 14-7-15. I messed with the settings from there and no matter what I get 7 lbs at the transition. Noise is also still there. I'll try to get some logs with the datalogit.
Okay, I got everything figured out this weekend. Thanks for the help, and thanks Mike for the datalogit!
1) The noise - I believe this was compressor surge. The charge control valve (CCV) is fed boost from the secondary turbo after the transition to force it to open. However, if that boost is significantly lower than the primary, the valve will delay opening since it is fed boost from the primary to hold it closed prior to the transition. I switched the boost source to the CCV and CRV to either the secondary or primary, depending on which is greater (see diagram). The noise went away after this and my transition was noticeably faster. This (and the sticking Solenoid 'E' fix) is a must for anyone running higher than stock boost IMO. Both are shown in the diagram below.
2) The transition 1 - I adjusted the PC and TC actuator arms to be as "light" as possible; i.e. the least amount of pre-load I was comfortable with.
3) The transition 2 - I think you need to use stock boost control for the stock twins for one simple reason; the WG is used after the transition and the PC actuator is used prior. There's no way to do this with an aftermarket controller. The stock solenoids with the PFC are working great. I tried 3 others...
4) The transition 3 - with the datalogit, I raised the transition point to 4880 rpms (boost settings in below pic). This made all the difference in the world. In print it looks high, but it doesn't feel high... the primary turbo perfectly carries the load below this point. My theory is simply that the larger BNRs need a bit more time to spool given the PC and manifold ports. Once I raised the transition point, I was able to finally see a relationship between primary boost and prespool; i.e. more primary boost, less pre-spool, etc. I was able to get a 10-10-15 pattern, but I wanted more primary, and settled on a 13-9-15 with a crazy fast transition; nothing like before. The car drives great (must have made 100 redline pulls over the weekend ), and the transition is now super smooth and fast. If I don't pay attention, I don't even feel the transition - before it was a very noticeable dead spot in the RPM range.
Vacuum line updates - I recommend both for higher boost sequential systems -
PFC Boost Settings (ignore the 3800 "low" setting, they all should be 3000) -
I personally had very good luck with Hallman Pro-RX bleed and ceramic check ball MBC on stock ECU 10psi and then also on ROM tuned ECU at 14psi.
In this case the Pre-spool MBC is set to open at a lower boost than the wastegate MBC, so it gets the 2ndary turbo spinning up early and fast. I had awesome transition with dual MBC, just a flicker down when watching the boost gauge, but I could get it set so it felt seamless and it would stay set.
I personally had very good luck with Hallman Pro-RX bleed and ceramic check ball MBC on stock ECU 10psi and then also on ROM tuned ECU at 14psi.
In this case the Pre-spool MBC is set to open at a lower boost than the wastegate MBC, so it gets the 2ndary turbo spinning up early and fast. I had awesome transition with dual MBC, just a flicker down when watching the boost gauge, but I could get it set so it felt seamless and it would stay set.
Your right, a lot of people have luck with that setup... Just didn't work well for me, although I didn't try it again since moving the transition point.
Nice work! Too bad you can't get the middle transition to something like 11 though. Are you going to keep playing with it a bit more?
I may... But the 9 lbs at the transition is more just a number, the car feels great through the transition. If I wanted a 13-11-15, I think I'll need to push the transition point a bit higher. I'm gonna drive it like this for a few outings and see how it holds in different conditions.
Great thread for those of us still running twins. I appreciate you posting up your fixes and results!
Originally Posted by BLUE TII
Thank god you were able to get it working.
I personally had very good luck with Hallman Pro-RX bleed and ceramic check ball MBC on stock ECU 10psi and then also on ROM tuned ECU at 14psi.
In this case the Pre-spool MBC is set to open at a lower boost than the wastegate MBC, so it gets the 2ndary turbo spinning up early and fast. I had awesome transition with dual MBC, just a flicker down when watching the boost gauge, but I could get it set so it felt seamless and it would stay set.
That's exactly what I was asking earlier and arrived at the same idea from your response. I was thinking about going back to PFC control of the PC and WG like moehler, but now I think I will play around with my MBC's and be sure to set the PC lower and the WG higher. I still wonder if the PFC is a better way to control sequential twins if not just for the fact that you can control boost via commander and you can have a higher or equal primary boost level.
I am just finishing a two year near total rebuild of my 94' Touring I purchased new in 1994. I stayed sequential but am using the newer SP Hitachi KAI twins that have 12% more air on the compressor side and the same stock exhaust wheel. (Not the Bathurst SP's from Australia) I also thought about upgrading to some newer type solenoids rather than the stock system since I can run these turbos just like the BNR's at much higher boost due to improved shaft size and a few other newer upgrades. The problem I kept seeing is the response of the stock actuators themselves were a major problem. They have set spring rates and the wastegate actuator is sprung too low for better control of higher boost. It begins to open with as little as 6-7 psi, lowing lower end boost in primary mode, and totally opens at 11.5-12 psi without any preload. This means the actuator can open with even full duty cycle from internal pressure in the exhaust side of the turbo manifold. This would also be true for BNR's and any of the stock twins. Also, the actuators are imprecise and use a diaphragm/spring old design. I therefore decided to buy custom Forge actuators with the newer piston design and interchangeable internal springs. I used the original brackets from the old actuator, which I sawed off, and mounted the new actuators on these brackets for a perfect mounting angle. Forge sells the arms to match the stock arm length and configuration. I started the car several weeks ago for the first time and I am finishing the last items on my last punch list. I will let everyone know the outcome after fine tuning with some road testing. I expect good things and better twin control.
Mike
I am just finishing a two year near total rebuild of my 94' Touring I purchased new in 1994. I stayed sequential but am using the newer SP Hitachi KAI twins that have 12% more air on the compressor side and the same stock exhaust wheel. (Not the Bathurst SP's from Australia) I also thought about upgrading to some newer type solenoids rather than the stock system since I can run these turbos just like the BNR's at much higher boost due to improved shaft size and a few other newer upgrades. The problem I kept seeing is the response of the stock actuators themselves were a major problem. They have set spring rates and the wastegate actuator is sprung too low for better control of higher boost. It begins to open with as little as 6-7 psi, lowing lower end boost in primary mode, and totally opens at 11.5-12 psi without any preload. This means the actuator can open with even full duty cycle from internal pressure in the exhaust side of the turbo manifold. This would also be true for BNR's and any of the stock twins. Also, the actuators are imprecise and use a diaphragm/spring old design. I therefore decided to buy custom Forge actuators with the newer piston design and interchangeable internal springs. I used the original brackets from the old actuator, which I sawed off, and mounted the new actuators on these brackets for a perfect mounting angle. Forge sells the arms to match the stock arm length and configuration. I started the car several weeks ago for the first time and I am finishing the last items on my last punch list. I will let everyone know the outcome after fine tuning with some road testing. I expect good things and better twin control.
Mike
Wow, very curious about how the aftermarket actuators work out. I've never seen anyone do that before. One thing I'd add though, you can adjust the actuator arm to preload the stock springs so they open at higher boost. If you're going to run higher boost, then I'd definitely do the vacuum line mods above...
Yes, you can add preload, but that will only add a few psi and will limit the overall range of the actuator. This adds way more flexibility since you can choose multiple different spring ranges, just like aftermarket turbo wastegates. Here is a picture of my turbos assembly on the workbench with the custom actuators and all of my ceramic coated turbos and piping. Also, I ported the exhaust manifold and the exhaust side of the turbo manifold. I opened the opening on the door side of the secondary to match the primary side opening. There is still plenty of overlap to have the door seal well, but should add significant secondary kick.
Mike
Correct. The stock turbo control valve. The other modifications on the turbo control side is not using the stock turbo solenoid, which usually fails, but reassigning to a unused emission solenoid on the rack. Also, I have the pressure regulator mod on the pressure side for all my solenoids to never see over 10.5 psi to prevent wearing them out and sticking. Also, all of the manifold metal is internally and externally ceramic coated to increase efficiency and to help prevent the typical cracking on the turbo manifold. The exhaust manifold is ported for increased flow and the turbo exhaust manifold is opened on the secondary to match the size of the primary opening. The door still closes with about a 3-4 mm lip all around and the flow should be much better to the secondary, with about a 20-25% increase in surface area from stock. Also, I used a JDM exhaust manifold with no EGR pipe in it, which can decrease flow and cause some air turbulence.
Mike
On thing on the Forge actuators. They come with only one nipple. so you can just tee both vacuum lines into one or do what I did an tap a second nipple on the top of the actuator so that both lines can attach separately just like stock. These actuator are very reasonable at around $150-160 each, especially since they are piston design, billet aluminum, custom arms to match stock, and have interchangeable springs. I have several Forge springs and several aftermarket springs to choose from during testing if I need them. The precontrol is currently 6-10 psi and the wastegate is 10-14 psi.
Mike
Correct. The stock turbo control valve. The other modifications on the turbo control side is not using the stock turbo solenoid, which usually fails, but reassigning to a unused emission solenoid on the rack. Also, I have the pressure regulator mod on the pressure side for all my solenoids to never see over 10.5 psi to prevent wearing them out and sticking. Also, all of the manifold metal is internally and externally ceramic coated to increase efficiency and to help prevent the typical cracking on the turbo manifold. The exhaust manifold is ported for increased flow and the turbo exhaust manifold is opened on the secondary to match the size of the primary opening. The door still closes with about a 3-4 mm lip all around and the flow should be much better to the secondary, with about a 20-25% increase in surface area from stock. Also, I used a JDM exhaust manifold with no EGR pipe in it, which can decrease flow and cause some air turbulence.
Mike
Nicely done. Any more info on pressure regulator mod? Seems like a worthwhile task for control system longevity.
Nicely done. Any more info on pressure regulator mod? Seems like a worthwhile task for control system longevity.
One correction. my pre control spring is 8-12 psi. Very similar to stock.
The pressure regulator mod I found here on the forum several years ago. You buy a small air pressure regulator that is adjustable around 10 psi or so. Just tap into the pressure line coming from your primary turbo outlet/y-pipe that typically goes right to your black pressure tank right in front of the UIM on top of the engine. No matter what pressure comes out of the turbos, the pressure is limited to 10-10.5 psi or what you set it the regulator for. The output line from the regulator just goes back to the pressure tank. The solenoids, all of them, never see more that this regulated pressure. This has worked for me for years. There are other options as some have discussed in this thread. My regulator I placed alongside the strut tower back from the main fuse box on a USDM LHD car. Don't put it on the exhaust side of the bay, too much heat. Most of the small regulators have heat limits.
To answer the last question, I have over 500+ hours into this near complete rebuild. Almost everything is either new, refurbished, and/or modified. Thermal management and air flow efficiency changes and mods were my goal. I upgraded everywhere I could. I started the car several times now over the last month. I had to adjust many things to get idle back to normal since my throttle body was ported and needed multiple adjustments and all my air flow components were either ported or extrude honed professionally. All my pipes intake and exhaust are ceramic coated for either for barrier or dispersant. I will begin road testing later this month. I live in Madison, AL next to Huntsville. I welcome anyone to come see it if you wish once its road worthy.
Mike
P.S. I will eventually do a build thread detailing every modification and parts used when I can.
09-07-18, 11:44 AM
), and the transition is now super smooth and fast. If I don't pay attention, I don't even feel the transition - before it was a very noticeable dead spot in the RPM range.
