That's right, I want an inconsistent boost pattern. The car I'm driving is not a track car, only a street car. I'm in the final phase of my build and thought about what's so fun about the FD. It's the stock twins. In first gear, you feel a push, a slight pull back very briefly, then another push when the secondaries kick in. That, to me, is what makes the car fun to drive on the street. When you go wide open throttle and switch to second gear, your RPMs don't drop far enough to need the primary turbo anymore. Your RPMs stay in that sweet spot of the rev range. I don't know off the top of my head where it drops down to, but it's definitely not down to 720 RPM. Now, the goal is to exaggerate this process by having a more aggressive switch, which would result in a 10-8-14 psi pattern. I'm scratching my head on how difficult this would be to do. Here are a few examples of what I'm thinking:

1. Get a "Stage 1" upgrade from BNR on my primary turbo and a "Stage 2" on my secondary turbo. From memory, the Stage 1 upgrade is an upgraded turbine with compressor and bearings, while Stage 2 involves machining the inside of the turbo housing to fit a bigger compressor.
2. Change the pill size for the secondary turbo, which is located in the two tubes coming off the turbo or, in my case, built into the pipes on the 99 specs.

I understand the basics of how the twin turbos work and how the primary turbo wastegate is actually the "Pre-Turbo Control" and uses exhaust gas to pre-spool the secondary turbo. Then the "Turbo Control" uses vacuum and pressure to move the huge diaphragm to open the flap in the manifold, so the secondary turbo receives the same amount of exhaust as the primary at this point. The "Wastegate Control" acts as an umbrella over the whole system and works in conjunction with the "Pre-Turbo Control." On the compressor side, there's a charge relief and charge control. The charge control keeps boost from leaking to the primary side too early, while the charge relief vents off extra boost.

Now, when it comes to putting all this together to figure out how to accomplish this goal, how would you do it?

My RX-7 FD mod list:

• Power FC, data logging with the new DL-340XB (replaces the Datalogic) and tuning with FC Tweak, shoutout to Xavier
• Stock injectors and fuel pump
• Greddy V-mount, 99 Spec Turbos
• Knightsports twin downpipe, FEED twin high flow cat, FEED AS-V catback, ported waste gate
• Upgraded ignition module (FD-IGN-10XB), new OEM coils

Edit:
I just realized this might not be possible after rereading my post. The "Wastegate Control" dumps exhaust gas for the whole system, so if it's set at 14 psi for the secondary, then the primary will spool up to 14 psi as well. Maybe the "Pre-Turbo Control" actuator, or basically the primary turbo's wastegate, can help with this by dumping the exhaust after 10 psi is reached. What do you think?

 

every car with a PFC i've been in has been pretty seamless with the transition.
however i wonder what happens if you play with the duty cycle of the wastegate? maybe you can turn it down, and instead of hitting its target right away, you can get it to undershoot and then ramp up?

 

With my home-made boost controllers (OE ECU), I have a boost pattern similar in feel to what the OP wants to get. It's approximately 11-8-10, but at the transition, I can feel the secondary turbo come in with a significant torque increase. It's definitely a satisfying push in the back.

 

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My boost gauge shows more or less the pattern you're talking about with just a downpipe and catback. You see a spike to 13 psi at transition and then it slowly tapers down to 11ish until redline. Manual boost controller (and ported wastegate if needed) with stock ECU would get you there.

 

I'm not that familiar with the PFC, but you should be able to control boost via the duty cycle of the WG. You could just tell it to go to one boost level/duty cycle for the first turbo, then tell the second to go to another boost level/duty cycle to achieve this pattern.

I'm fairly certain you can tune when the transition happens on the PFC, so I would imagine you could do this as well. I know on my AEM S2 I can achieve something similar in its advance boost settings. Can you post a picture of the boost control screen on the FC-Tweak?

 

Sure you can do that with the PFC. It's probably the best ECUs when it comes to control the stock twins. It offers:

(a) full control of both pre-control & wastegate duties
(b) independent primary and dual mode boost targets
(c) RPM and TPS% at which WG control comes into action
(d) RPM and TPS% for pre-control to regain control, thus enabling you to accurately set the point at which both turbos remain locked, or when the primary mode takes back control, depending on your gear changing habits
(e) Intelligent PC & WG duty control to keep you within the target boost settings even when your initial duty settings are way off.
(f) Fuel cut protection when boost overshoots the set target by more than 3.6psi

All these settings are clearly shown on FC-Tweak's settings Page 7.

 

He has spoken.

I'll have to check it out once my car is together, been 2 years already but almost done. Thanks for the reply

 

Poor man's way = Throw a straightpipe on and let it creep on the secondary turbo. Going to go Marcus Read here " MAKE SURE YOU HAVE ENOUGH FUEL". At 14PSI, you'll want a 255LPH pump or go up to 280LPH pump.

Proper way = Get a ECU that lets you control Boost by RPM and Boost by Gear. Maybe even a AVC-R.