I've been thinking about this for a while, and correct me if I'm wrong, porting intake cambers on the 13b causes low compression readings with a standard compression gauge.
To me it makes sense since the profile is changed affecting flow characteristics and depending on the port low end power is sacrificed for the sake of top end power. So when I'm sitting here cranking the motor at 250rpm to check compression the readings don't mean much since the intake ports have been altered. Does anyone have numbers to back this up with, someone who tested their compression before porting their irons and after?

 

Unless you extend your ports really far up(into the start of the compression "stoke") it shouldnt have any meaningful effect of compression. Now it will make the engine read less vac. at idle.

 

+1

 

What about when combining ports (porting out a 6 into a 4)?

 

I don't know how that is even possible...

 

you have just ruined the engine.

 

How so?

 

porting that thing like that has proven to be fruitless and will not yeild any more power than the stock port.

 

By lowering the volumetric efficiency.

 

I refer to that as an abomination port. You're free to try it if you want, but learn from others, it will KILL PORT VELOCITY inside the usable rpm range. When looking at the secondary and aux ports as a whole there is already a lot of port area there, cleaning up those ports and extending the primary ports will help. Although the real easy gain is to just get rid of the inconel exhaust diffusers, either spend the ridiculous amount of time to grind the wings off or just replace the sleeves with tii ones.

 

Im sure its crossed few minds. Converting 13b to a t. Removing the sixport housing completely would be a task, I've read not in detail how to remove the exhaust diffusers, replaceable with tII's didn't know that. Any slight advantages on running s5 n/a rotors on a s5tii engine?

 

Yes there is.
9.7:1 cpr with a turbo is a fun street car.

 

Because doing so will create a port that won't make much usable power until the 8,000 RPM range, at which point you're out of stock intake and ECU anyway.