The engine is an '87 13BT. I am porting the intake side using mazdatrix templates. I asked them about exhaust and they said there was no template and to just smooth out the port so it's even with the iron insert. Those of you who've ported your turbo's what are your recommendation. I have complete faith in mazdatrix, but I thought there would be more with the exhaust. Thanks

Steven

 

Yeah, round it out slightly so it's even with the insert.
It will also help to drop the bottom down about 2.0 - 2.5mm.

 

Kinda depends what you want the motor to do. You can advance the timing of the exhaust port by lowering its opening point which will kill your torque and lower the spool time of the turbo, but I wouldn't increase its durration beyond that (making it close later than stock) because you'll end up with too much overlap for a forced induction engine and you'll lose power over all.

There's plenty of info and pics of peoples porting online if you just look for it.

 

Be very careful when using those templates on the primary ports. The secondaries can easily go as large as the template but the primaries will not. There is not enough casting behind the ports. Unless they now sell new T-II templates, those templates were designed to work with the old pre-86 13B's since they could be ported out huge. They are still valuable for the new engines though using them as a general guideline.

The exhaust side is somehwat controversial depending on who you talk to. If you ask 10 people how to do it you'll probably get 10 different answers. The way I personally do it is to enlarge the opening to the same size as the sleeve (when I still retain the factory sleeve) regardless if it is on a turbo or n/a. The larger port area gives you less backpressure as far as the engine is concerned. Backpressure through the turbo is a different matter altogether. The downside to porting to the same size as the sleeve is that your port overlap will increase. This causes a slight loss in lowend power and makes emissions worse. The turbo will still actually spool faster regardless due to the overall increase in airflow capability. Ever seen where big turbos on bridgeported engines start to make power? It can be impressive sometimes and they have huge amounts of overlap. The common way of thinking is beginning to completely reverse in regards to port timing on turbo engines. The aussies have known this for years. Other people will tell you to only port the exhaust downward and not up. If you go this route then at least angle the top of the port upward to help blend with the expansion rate of the sleeve. This will cut down on turbulence but not add overlap to the engine. Whatever you ultimately decide will most certainly be an improvement over stock.

 

They must have new one's because mine are specifcally for '87-'95 Turbos.

Thanks for all the advice everyone. It really helps!

 

Cool! They didn't have those a few years ago when I got mine. I don't need templates anymore anyways.

 

Do you know anything about the physics and chemistry of a motor?

Weather it be forced induction or n/a overlap caused by increased intake and exhuast duration will gain HP.

how much some people lift the exhuast ports would give YOU heart failure, and they certainly aren't short of HP