I was wondering if anybody could tell me what the ecu does, if anything to control the turbos. I know that there is vacuum line and wutnot, but was wondering if what the computer does to control the turbos. thanx in advance for any info.

 

Well, it does a lot of things...all of those solenoids which determine where the air goes...if you look at what happens at various RPMs like during prespool, once the secondary comes on line, etc...the ECU makes all that happen.

If you're simply talking boost control, it controls the precontrol and wastegate solenoids. Its not a feedback system though, its mapped. Depending on RPM, etc. the ECU sets the duty cycle fo for those solenoids, which directly determines when the precontrol and wastegate do their things.

jds

 

So if i put manual boost controlers in instead on the solenoids, i wouldnt need the computer?

 

If you put manual boost controllers in instead of the solenoids you wouldn't need the computer to control boost...but your statement is a little vague. What exactly are you trying to do?

jds

 

well, i am going to try and put a sequential twin turbo system on my 240sx. i like the way that it is done on the rx-7 so im trying to figure out how exactly the twin turbos are controlled. ive got the diagrams of the turbos and vacuum lines and such.

 

do you know what the minimum things are that you have to have for the sequential turbos to work?
ANd, how do you adjust when the secondary turbo spoils and then when it takes over?

 

Eek. You're doing this willingly?

There is a lot of stuff involved in making it work the way the 3rd gen's system works...I'm sure I don't know half of it. I think if I were designing my own I'd go with an electrical control system rather than all the vacuum lines, etc...but maybe there are underlying reasons not to do that that I haven't considered.

There is a wastegate-like device on the primary turbo that, instead of venting exhaust gasses out the tailpipe, it vents them to the secondary turbo. There is a duty solenoid, mapped in the ECU, that controls how much pressure is seen at the precontrol actuator...this determines when and how much prespool action occurs. I've bypassed that and am using a ball-and-spring type valve, but I'm not completely convinced I like this for the prespool yet.

jds

 

so i need to get some kind of valve to vent some exhaust to the secondary turbo that is controlled either by a electric signal or vacuum to get the prespoil for the secondary and then vent all exhaust to the secondary when the engine gets to around 4-4.5K rpm?

 

Sort of. After the transition, exhaust is spinning both turbines. At some point after the primary spins up, the secondary starts to prespool, but its not affecting the intake charge until the transition from primary only to twin mode. There are several valves involved.

jds

 

Not only that, you need a gatherer / headder that will match the manifold on the twins, since the wastegate and prespool controll all sit in the manifold... also a ball bearing upgrade would be adviseable, since turbo rotaries "puff" with a lot more force, than a 4 banger or 6 banger, so you need something to ease the force neccisary to spin them twins up

Also the twins are made to transition at 4.5K rpm due to that is about 1/2 way through our rpm limit, 9K and works well for us, the transition point is controllable, via pills or a controller, but I tried to make the twins transition sooner, and there is not enough exhaust flow to build pressure in both turbos at the same time.. -> hence BB is going to help, but who knows how much flow you're going to create...

Personally I'd search for a T34 or T40 Twin "Kit" for your car, since it will have all these enginnering issues taken care of to one extent or another....

Hopefully if you do decide to undertake this someone who understands the twins very well, can help you figure some of this stuff out...

-DC

 

there aren't any twin turbo kits for my car. My car has a KA24DE motor. There have been twin turbo systems for the SR20DET, which is the Jap motor for my car, but it was only for show purposes. i want to make the sequential tt for my car. it is gonna take a while to figure out the exhaust manifold design with all those valves and stuff, and how to get the vacuum stuff figured out. i wan to see an exhaust manifold off a 3rd gen. rx7 to see exactly how they ae made and wut are in them. I want to get the transistion from primary to secondary around 3.5-4k rpm's.

 

sounds like a good plan but if you noticed most people with our cars go to a single turbo down the road....i hope you have taken into consideration exactly how much power you want from the turbos,they may not giv you what your looking for and a single may be a wiser choice do to how easy it is to install and **everyone loves a warentee**