Im rebuilding the engine as we speak and was wondering if my builder should do a mild port on the exhaust side. Ive got the typicall mods(MP, CB, Intake, Gforce ECU, pullies.) I need my car to be a daily driver and was wondering if a mild port will fluctuate my idle really bad or even if the Gforce can take a boosted ported motor. Any help? What is safe boost to run on a stock fuel injected, ported motor?

 

The biggest gains can be had from porting the intake not the exhaust. I have a large street port and the idle is fine. I have it set at 950 where as with the stock motor it was 800. below 3000 it doesn't feel as strong but above 5500 it pulls a lot harder than the stock motor did. As for the ECU I think you should give the company a call. As a rule of thumb street ports require less advance

 

Thanks for the info

 

IMO, porting only makes sense if you intend to run 15+ psi boost. The stock ports can handle anything up to that. You

 

A mild or average port shouldn't effect the idle or reliability.

 

I have just had my engine fully rebuilt...all is new other than rotors...I also had a street port done
I have only done c. 700 km.
At fisrt my idle was a bit fidly, but it is settling fine now c. 800 rpm...my mechanic told me when I do my first service it will be fine (c. 1000km).
I was worried for the low down loss of torque, but I have not seen this (I only rev up to 3000 rpm)...however I do not know if this is because my old engine was bad. All I have is a downpipe on performance mods! I will be guetting a PFC soon, as I am running on the stock ecu.
Hope this helps

 

anything over a street port is when your idle will be different, thus the "street" port meaning its good for thet street, unless you go crazy on the port and just call it a street port, but most of the time any street port is good for the road.

 

You did a port job before everything else?

Never heard that before.

I would think that if you did any port job on the exhaust side that you'd introduce more lag as you'd be slowing the exhaust velocity down. Perhaps if you had a divided manifold it might help some though.

 

Engine porting doesn't have anything to do with inadequacies of the stock ports (unlike wastegate porting). The stock ports can run 20+ PSI, if you like, without any problems.

Engine porting is to increase airflow through the engine to gain more power, not to fix a problem. Depending on the size of the port and other components on the car, it can yeild up to a 20% increase in overall power. As with everything, nothing is for free, so you lose some low end grunt.

 

Yeah, Dave Barninger did a large street port on a new Malloy reman for me (25% increase in both intake and exhaust ports). The sweet spot is in the midrange rpm (3000 to 6000 rpm) with power dropping off after 7000 rpm. Might try a Pineapple next time (monster port )!

 

Speaking of ports, anyone read the Mazda RX-7 Performance Handbook? In it, the author states that once you port you can kiss passing emissions good bye, but doesn't really elaborate on why that is. Anyone have any insights, refutations, corroborative evidence?

 

Thanks guys. Ill be sticking with the stock ports for now. Dont plan on going single for awhile anyway. My car was fun as hell before an Oil seal went on the rear rotor so Ill put it back to great self

 

I do not know what emission standards you have in the US, but I will not have trouble passing them in Greece. Anyhow, I will let you know how I am progressing with the ports.

 

I found better results with only exhaust porting that I did with street porting...but that's with a big single. Either way, if you've got it apart, why not port? Any gain of HP above stock would be worth it IMHO. If your worried about emissions, just tune it a little leaner in your idle blocks.