Simplified sequential for aftermarket ECU's
03-22-09, 07:06 AM
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Simplified sequential for aftermarket ECU's
Alright, I'm working on setting up sequential for use with an aftermarket ECU and I've been going over the diagrams, vacuum routing, sequentials operation, and every thread I could possibly dig up on the subject. Most people seem to use 4 solenoids (or more), using generally 3 outputs. My goal with what I've got below should be controllable with 1. It differs only from the simplified sequential version for a stock ECU (using a boost controller for prespool) by consolidating the charge relief/control into a single solenoid (Which dramatically reduces the ECU requirements). In this method I don't need a separate output to vent pre-spool as it'll happen automatically. I've tested this on my '94 with good results so far but would like some feedback on the questions below.
Questions I have:
1) In my operation, the Charge Relief remains open at ALL times prior to transition, vs only during pre-spool on the stock ECU, I can't think of a reason why this wouldn't work or any negative effect as there's nothing happening here with the charge control door closed anyway, and it'll still vent pre-spool until transition. Thoughts?
2) Is there a timed delay between Charge Relief/Control and Turbo Control? Everything I've read (and seen on the stock ECU) seems to imply that this all happens at the same time. I've tested all 4 solenoids (Turbo Control's 2, Charge Relief, Charge Control) at the same RPM with good results, but I often see these 3 different things ran separately. Any reasoning behind this that I might be missing?
3) What purpose does the pressure chamber & check valve serve to the Turbo Control? Wouldn't you typically always have boost when you want the turbo control open? Is this to prevent the turbo control from possibly closing partially upon transition as pressure drops? Or is it instead to keep the Turbo Control open above X rpm so that the car behaves more like a non-sequential in the upper bands? (As opposed to acting just like sequential except for the transition wouldn't dump it'd just open as soon as pressure was regulated on the control)
Hardware and Diagrams:
1 Manual Boost Control for Turbo Precontrol (This has proved effective)
1 Electric Boost Controller for overall wastegate control
3 Solenoids (Triggered together by a single output)
Turbo Control (Vacuum)
Turbo Control (Pressure)
Charge Relief Control & Valve (I've moved both of these to a single solenoid)
Diagram of Vacuum Routing:
Questions I have:
1) In my operation, the Charge Relief remains open at ALL times prior to transition, vs only during pre-spool on the stock ECU, I can't think of a reason why this wouldn't work or any negative effect as there's nothing happening here with the charge control door closed anyway, and it'll still vent pre-spool until transition. Thoughts?
2) Is there a timed delay between Charge Relief/Control and Turbo Control? Everything I've read (and seen on the stock ECU) seems to imply that this all happens at the same time. I've tested all 4 solenoids (Turbo Control's 2, Charge Relief, Charge Control) at the same RPM with good results, but I often see these 3 different things ran separately. Any reasoning behind this that I might be missing?
3) What purpose does the pressure chamber & check valve serve to the Turbo Control? Wouldn't you typically always have boost when you want the turbo control open? Is this to prevent the turbo control from possibly closing partially upon transition as pressure drops? Or is it instead to keep the Turbo Control open above X rpm so that the car behaves more like a non-sequential in the upper bands? (As opposed to acting just like sequential except for the transition wouldn't dump it'd just open as soon as pressure was regulated on the control)
Hardware and Diagrams:
1 Manual Boost Control for Turbo Precontrol (This has proved effective)
1 Electric Boost Controller for overall wastegate control
3 Solenoids (Triggered together by a single output)
Turbo Control (Vacuum)
Turbo Control (Pressure)
Charge Relief Control & Valve (I've moved both of these to a single solenoid)
Diagram of Vacuum Routing:
03-22-09, 12:57 PM
#2
1) From the factory I bet the charge relief was kept closed during normal operation to decrease noise. One thing you could consider experimenting with (and I've thought about this a bit) is eliminating the charge relief valve and duty control the charge control valve with whatever ECU you are using. I'm pretty sure that's how the Mark IV Supra is set up ( see http://www.mkiv.com/manual/manualtt/...ption/ttd3.JPG ). In that way during prespool the charge air will not be vented at all. This would probably be tricky to get working right though.
2) If I could guess, under part throttle they may not be timed the same from the factory. Remember that factory engineers have a much more challenging job than we do: impeccable driveability for the masses as well as performance. Many two stage engine systems (VTEC, sequential turbos, possibly the VDI and 6 port systems on the Rx-8) vary transition based on load. I know the VTEC switch point on Hondas varies according to MAP. There are adjustable transition points in the Power FC for going between sequential (spooling 1 turbo) and non sequential (spooling both, turbo control open) based on TPS voltage. You may not notice a whole lot of difference from engaging them at the same time. It doesn't seem that important to me to keep the control systems separate.
3) If I were you I would be very hesitant to change any of the plumbing for the turbo control valve. Mazda clearly went through great lengths to maximize its response. The precontrol valve is opened gradually and is duty controlled, but the turbo control actuator is designed to snap open almost instantly. There is no cost or emissions incentive for them to have such complex plumbing for one actuator.
Look at the setup--it uses a dual port actuator, which works just like an aftermarket dual port wastegate actuator or an external wastegate. Pressure applied to the bottom port will open the flapper just like a standard single port internal wastegate actuator. Vacuum applied to the top port also pushes it open (and pressure to the top port would push it closed, just like an external wastegate).
Combining both functions to open the flapper will increase its response. The more pressure applied to the bottom, the faster it will respond; and that's where the pressure tank comes in. It seems like having that tank, controlled by a solenoid valve, would allow the highest and most consistent pressure to be applied to the actuator, maximizing response of the turbo control valve. I thought I remember reading somewhere in another thread that the dual port design was a somewhat last minute addition that Mazda installed to increase response.
2) If I could guess, under part throttle they may not be timed the same from the factory. Remember that factory engineers have a much more challenging job than we do: impeccable driveability for the masses as well as performance. Many two stage engine systems (VTEC, sequential turbos, possibly the VDI and 6 port systems on the Rx-8) vary transition based on load. I know the VTEC switch point on Hondas varies according to MAP. There are adjustable transition points in the Power FC for going between sequential (spooling 1 turbo) and non sequential (spooling both, turbo control open) based on TPS voltage. You may not notice a whole lot of difference from engaging them at the same time. It doesn't seem that important to me to keep the control systems separate.
3) If I were you I would be very hesitant to change any of the plumbing for the turbo control valve. Mazda clearly went through great lengths to maximize its response. The precontrol valve is opened gradually and is duty controlled, but the turbo control actuator is designed to snap open almost instantly. There is no cost or emissions incentive for them to have such complex plumbing for one actuator.
Look at the setup--it uses a dual port actuator, which works just like an aftermarket dual port wastegate actuator or an external wastegate. Pressure applied to the bottom port will open the flapper just like a standard single port internal wastegate actuator. Vacuum applied to the top port also pushes it open (and pressure to the top port would push it closed, just like an external wastegate).
Combining both functions to open the flapper will increase its response. The more pressure applied to the bottom, the faster it will respond; and that's where the pressure tank comes in. It seems like having that tank, controlled by a solenoid valve, would allow the highest and most consistent pressure to be applied to the actuator, maximizing response of the turbo control valve. I thought I remember reading somewhere in another thread that the dual port design was a somewhat last minute addition that Mazda installed to increase response.
03-22-09, 03:58 PM
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1) From the factory I bet the charge relief was kept closed during normal operation to decrease noise. One thing you could consider experimenting with (and I've thought about this a bit) is eliminating the charge relief valve and duty control the charge control valve with whatever ECU you are using. I'm pretty sure that's how the Mark IV Supra is set up ( see http://www.mkiv.com/manual/manualtt/...ption/ttd3.JPG ). In that way during prespool the charge air will not be vented at all. This would probably be tricky to get working right though.
2) If I could guess, under part throttle they may not be timed the same from the factory. Remember that factory engineers have a much more challenging job than we do: impeccable driveability for the masses as well as performance. Many two stage engine systems (VTEC, sequential turbos, possibly the VDI and 6 port systems on the Rx-8) vary transition based on load. I know the VTEC switch point on Hondas varies according to MAP. There are adjustable transition points in the Power FC for going between sequential (spooling 1 turbo) and non sequential (spooling both, turbo control open) based on TPS voltage. You may not notice a whole lot of difference from engaging them at the same time. It doesn't seem that important to me to keep the control systems separate.
3) If I were you I would be very hesitant to change any of the plumbing for the turbo control valve. Mazda clearly went through great lengths to maximize its response. The precontrol valve is opened gradually and is duty controlled, but the turbo control actuator is designed to snap open almost instantly. There is no cost or emissions incentive for them to have such complex plumbing for one actuator.
Look at the setup--it uses a dual port actuator, which works just like an aftermarket dual port wastegate actuator or an external wastegate. Pressure applied to the bottom port will open the flapper just like a standard single port internal wastegate actuator. Vacuum applied to the top port also pushes it open (and pressure to the top port would push it closed, just like an external wastegate).
Combining both functions to open the flapper will increase its response. The more pressure applied to the bottom, the faster it will respond; and that's where the pressure tank comes in. It seems like having that tank, controlled by a solenoid valve, would allow the highest and most consistent pressure to be applied to the actuator, maximizing response of the turbo control valve. I thought I remember reading somewhere in another thread that the dual port design was a somewhat last minute addition that Mazda installed to increase response.
2) If I could guess, under part throttle they may not be timed the same from the factory. Remember that factory engineers have a much more challenging job than we do: impeccable driveability for the masses as well as performance. Many two stage engine systems (VTEC, sequential turbos, possibly the VDI and 6 port systems on the Rx-8) vary transition based on load. I know the VTEC switch point on Hondas varies according to MAP. There are adjustable transition points in the Power FC for going between sequential (spooling 1 turbo) and non sequential (spooling both, turbo control open) based on TPS voltage. You may not notice a whole lot of difference from engaging them at the same time. It doesn't seem that important to me to keep the control systems separate.
3) If I were you I would be very hesitant to change any of the plumbing for the turbo control valve. Mazda clearly went through great lengths to maximize its response. The precontrol valve is opened gradually and is duty controlled, but the turbo control actuator is designed to snap open almost instantly. There is no cost or emissions incentive for them to have such complex plumbing for one actuator.
Look at the setup--it uses a dual port actuator, which works just like an aftermarket dual port wastegate actuator or an external wastegate. Pressure applied to the bottom port will open the flapper just like a standard single port internal wastegate actuator. Vacuum applied to the top port also pushes it open (and pressure to the top port would push it closed, just like an external wastegate).
Combining both functions to open the flapper will increase its response. The more pressure applied to the bottom, the faster it will respond; and that's where the pressure tank comes in. It seems like having that tank, controlled by a solenoid valve, would allow the highest and most consistent pressure to be applied to the actuator, maximizing response of the turbo control valve. I thought I remember reading somewhere in another thread that the dual port design was a somewhat last minute addition that Mazda installed to increase response.
I'm not sure what noise there would be as theres nothing moving through the charge relief anymore than there would normally, I think it just works the actuator a lot more than it'd normally see but that shouldn't be a problem. I've also considered duty cycle control of the charge control, but I think that may have an adverse effect on the pre-spool speed as it'll take a bit more to spin up with compressed air working against you as opposed to spinning up with atmospheric initially. I'm sure it's managable as the Supra's do it though.
Everything I've read and seen regarding their points in the FSM and testing on the road with a multimeter/etc always shows these to be RPM based, I can't ever find a situation where they seem to change with load. It's my thinking that the PowerFC tried to be a little bit more feedback controlled than the original was.
I'm going to leave the double solenoids in place, I'm just unsure why they're using a pressure chamber for a source that's already under pressure. As I said, my only thinking is they didn't want the transition drop pressure to cause the Turbo Control to fluctuate so they trap the constant 10psi in the pressure chamber (unless of course you spike to more or something). Also this would force the turbo control to remain open above X rpm (I've seen this solenoid stay on under light load, so unless that pressure leaks off this would be true) causing the car to spool non-sequential above transition, which is acceptable behavior in my opinion.
since you are looking into improving the twin turbo system i would like your opinion on this picture below. I though of replacing the turbo control actuator with a regular push style actuator and control all 3 actuator with manual boost controllers. Its just something i thought of and never relay got any feed back on it.
03-22-09, 05:31 PM
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Other than the minor lag at transition, you'd also end up running near sequentially again above the transition point. From my testing with the PFC the Turbo Control doesn't close again until the RPM range comes below transition, meaning that the car spools non-sequential. I think they did that to make them predictable at high speeds.
Edit: I also don't see a charge relief/control solenoid in there, did you accidently erase those or did you change the operation of the valve as well?
Edit: I also don't see a charge relief/control solenoid in there, did you accidently erase those or did you change the operation of the valve as well?
03-24-09, 02:10 AM
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So i've done some more testing, and it seems that with the pressure chamber/check valve not in place it introduces a bit more lag to transition. I've had no ill effects so far by moving charge relief/control to a single solenoid. I did discover that closing turbo control past transition and putting it load dependent really seemed to cause more troubles than it was worth, it seemed to choke off my upper band trying to spool the primary by itself and gave me really sporadic throttle response. I've since just left it open beyond transition and it's considerably smoother and more predictable. So far I'm pretty confident in this configuration, but I'm always looking for advice. Can anybody see any long term ill effects to this setup or improvements?
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