Markus1981

I guys , i am batteling with my Series 7 and the twins . My second turbo does not come online most of the time . However if i blip the throttle a few times over 4500 rpm , the second turbo comes online and boosts 0.7 kg/cm2 . From what i read it sounds like a vacuum problem ? I know there should be a check valve to the vacuum tank but i cant find where exactly that should be . The car was directly imported from japan and the sequential system never worked properly . If anyone can give me a series 7 diagram i would apprechiate it a lot . At idle 900 rpm the car has a vacuum of -270 mmHg at 912 rpm its -309 mmHg . If i rev the car in neutral i get 0.26 kg/cm2 at 6270 rpm. If anyone has any diagram from a series 7 please help !

Markus1981

This is what it looks like . The left line from my pressure chamber goes to the y pipe like in the diagram . The right one goes to a black plastic piece . Thr line lrft of that plastic piece goes to the vacuum tank directly with no splice or check valve . So i think the routing of the vacuum lines is not right

billyboy

Can't make out anything useful from your picture!

Diagram is here -

https://www.rx7club.com/3rd-generati...diagam-792369/

there are better ones out there, coloured, etc, not on this forum though, afaik.

Usual issues you should check in order of failure are the one way valves, the odd dead or sticky solenoid - especially the ones that have high duty cycle, air leaks in the black box, vacuum and pressure chambers and lastly, the actuators.

96fd3s

Yes it sounds like a vacuum problem..
You need to remove the upper intake manifold and make sure all the hoses are connected..
You cant do much without taking it off! There is about a dozen hoses under there that you cant see because the intake manifold is in the way..(i have a S7)

Markus1981

Thanks guys for pointing me to the S7/S8 Vacuum diagram ( I haven been looking for weeks without success )
I went over it last night and saw that the hose from the Vacum Chamber and the hose from the Pressure Chamber are the wrong way arround on my car ( see attached diagram ) . I will try tonight after work and hope its just that . If not i will take of the UIM of and go line by line on the weekend ....

Markus1981

She finally boosts !!!!!!! found another pair of swapped vaccuum pipes and one old rubber pipe that didn't seem to seal very nice . Drove her just now and it's awesome when the twins work .

Markus1981

Hi guys ran into a lot more problems with my twins . I found 3 solenoids that where dead . Replaced them and now I get a solid 0.8 kg/cm2 on the first turbo , after that it makes the transition to the 2nd turbo but then only boosts 0.44 kg/cm2 ( 6.8 PSI) I then started to diagnose the second turbo and found the line to waste gate has been replaced but without the destructor pill . Went to my local Rotary tuner and got a hose with pill from one of the turbos he had lying arround . I checked if the line had the pill in , and then installed it . Still the same result 0.44 kg/cm2 only on the second turbo . I have a power fc and i also played arround with duty cycle but no change at all . Anyone got a hint what else it could be ?

Markus1981

Found my problem , my wastegate actuator diaphrame is buggered .

fd3s7007

Hey Markus glad you sorted your boost issues. I'm doing the same and i know how frustrating it can get ��

Markus1981

Thanks , still need to get a new one and fit it

Markus1981

Does anyone have a good tip how to replace the wastegate actuator with the least disassembly possible ?

Markus1981

Never mind managed to get the actuator out from the top , it's tight in there but not impossible , now just need to get a new one

Markus1981

turned out this wasn't my problem either . Had my wastegate and precontrol solenoid connectors swapped and a leaky pressure tank . Now she boosts like never before on both turbos . I love the working sequential twins

p51hellfire

iTrader: (12)

Just out of curiosity, I have recently acquired a 99 rats nest and I have a 93. I'm trying to figure out if this is something I could install in my 93.. Anyone heard of such a thing? Is it worth my time? I have the wiring harness for the 99 as well. Thanks all!

Markus1981

Yes you can install it , but I honestly don't see a benefit . My personal opinion . Benefits of the plastic box : -looks neat and less hoses to worry about -RX8 solenoids are a straight replacement Drawbacks : - looking neat but you anyways can't see it because it's hidden behind the pressure tank so pointless in my opinion -it's made out of plastic and takes more space under the UIM ( in my view less cooling flow below UIM ) -For every solenoid and 1 way check valve (2 are inside the box ) you have to take the box apart and hope it doesn't break ( I did that a few times and touch wood everything is fine ) -you have to use the Mazda check valves as the superior and by far cheaper viton check valves won't fit in the box ( too wide ) -if you break a nipple of the plastic box you are 700$ out of pocket . Summary : In terms of rigidity the old rats nest is better than the plastic box once you did a hose job and a lot less to worry about .( this is my personal opinion ) As an alternative to the harness change you can also take the box apart and fit the old series 6 solenoids . They fit straight into the box and then you have the correct connectors .