I'm running a Hybrid Turbo on my 13B Cosmo and in planning for upgrades, I'm considering doing a half bridge port and later upgrading the turbo to a GT35r or something in that range. I want this car to be very street drivable and I know the downside of vacuum leaks.

In trying to further understand how the rotary works and responds to modifications, I have questions:

Is Exhaust Backpressure essentially the inverse of Intake Vacuum?

Does Exhaust Backpressure preclude or nullify Intake Vacuum?

Does half bridge porting reduce or nullify Intake Vacuum?

Is Intake Vacuum required for stable cruse RPMs?

*If* cruse RPMs' driving stability is reduced because of low vacuum level, what is physically responding (or not responding) to the low vacuum level and is there a remedy to supplement that could increase the vacuum level in order to stabilize cruse RPMs driving stability?

 

Vacuum has nothing to do with the exhaust. A vacuum leak will create a high idel. becouse it is unregulated air coming into the engine. Vacuum on the engine tells its health the more vacuum the better the engine.

Hope this clears up a few things for you

 

So a vacuum guage isn't a very usefull diagnostic tool for a rotary because the intake is seperate.

 

I was attempting to apply the info from the sticky thread: Overlap & Halfies & Quicker spool http://forum.teamfc3s.org/showthread.php?t=52376 to my application. They talked about overlap and scavenging as benefiticial and seemed to say that a half bridge port could be designed to provide good low to midrange power and even idle at 850 RPM. With a small street port, I had trouble idling below 1000 RPM, but I had some vacuum leaks.

Also, before the vacuum leaks were fixed the car had some serging problems during medium or neutral throttle. I *would not* like to recreate this and I wondered if the half bridge might do just that, since I *thought* the Overlap & Halfies & Quicker spool thread mentioned that the halfie created a situation of low vacuum. I'll go back and reread yet another time.