Have a stock 00 jdm rx7 type r and trying to iron out an issue with the sequential system. Only mods is a hks intake and cat back exhaust. Solenoids have been upgraded to aftermarket mac valves and have a perfect boost pattern 10 8 10.
The problem arises after i go above 4500 and change gear. If the rpm falls between 3000 and 4000 the car is lagy af. The second i let the rpm drop below 3000.. boom! Primary kicks in hard.
At first i thought it was a sticky turbo control actuator getting stuck open but then i attached a multi meter and got a suprise. The stock ecu wont stop the voltage signal to the turbo control actuator until the rpm drops below 3000. Is this normal? I had assumed that because the ecu tells the actuator to open at 4500 it would also tell it to close when the rpm drops below 4500. I know i should just go single but to be honest i really enjoy the problem solving

 

The ECU is functioning correctly.

There is a 2ndary turbo latching function to prevent you from cycling down to the primary turbo needlessly.

Check/calibrate the TPS though. I seem to recall that this is a part throttle latching and completely releasing the throttle should reset the latch and get you back into the primary turbo.

Also check that your catalytic converter isn't clogged up. The spool should be prompt at 3,000rpm even with yuor 2ndary turbo latched on (though less frenetic than primary alone at 3,000rpm).

 

Well then I have airfare ready next time I have an issue. You or Blue...or both.

 

Thanks for your help. Ill have a look at the tps and cat when i get back home next week. Could it also be possible that the turbo control actuator is slightly out of adjustment? I did replace this recently as my old one had a pressure leak. i also made sure that there was some tension against the actuator rod when i installed it. Not that i think that would matter all that much considering the turbo control operation is either fully open or closed. My turbos are also getting a bit old and starting to leak a slight bit of oil now. Im guessing that this could also contribute to the secondary not spooling as quickly when the secondary is still latched on. Anyone selling some bnr's? haha

 

So checked everything out finally. All looks good. Finally finished the full solenoid conversion this week and it seems to be a little better. Was great this morning when i took it out for a drive but once the day got warmer it started to be really slugish once the secondary turbo was "latched" again. Thinking at this point that its either my secondary turbo or the turbo control actuator. The secondary has been smoking a tiny bit when it kicks in. Its possible i may have damaged the actuator diaphragm aswell after i replaced it. The circlip was a bit rusty and came off while i was thrashing the car. Got a spare set of turbos that ill put on in the next few weeks. Only prob is is that that they are the fb turbos and not the 99spec type r ones. See how that goes. Will post more updates

 

Yep, sounds like it is possibly a worn out 2ndary turbo causing the sluggish operation when both turbos are supposed to be working together.

Could also be a boost leak between the 2ndary turbo and the "Y" pipe or a leaking Charge Relief Valve (the plastic thing that looks the same as stock BOV, but is back off the rear turbo outlet instead of forward off the Y pipe.).
This would allow normal boost on primary turbo and sluggish boost and overworked turbos when both turbos are supposed to be working together.
It would also likely wear out the 2ndary turbo prematurely.

So, if you get the new turbos in and continue to have the same problem test/replace the Charge Relief Valve as soon as possible.

Good luck!