I was just wondering what the gas mileage, reliability and low end difference would be between a mild street port and an agressive street port on a s4 TII. My current engine is ported (mileage not too great but I love it) I was wondering if I went further with it next time if the gas mileage would be that much worse and if it will be that much less responsive in the low end and if it was worth it later on in the power band. Please post your gas mileage or experiecences. Thanks.

 

Anything that falls within the realm of a streetport is generally considered to have a negligible effect on mileage and reliability. That's why it's called a "street" port.

Aggressive street ports that open much earlier then stock and close much later are going to have negative effects on mileage (any port with lots of overlap really kills low RPM efficiency). If you get to the point where you start cutting into seal paths the reliability goes out the window as well.

Very high HP levels are available on normal sized street ports, so don't get sucked in by the lure of massive ports.

 

Thanks for the info. Guess I'll keep it mild.

 

You can have a pretty large streetport and still have it function just fine. I had a good sized streetport on my car, nothing crazy but it did have a touch of overlap. I still got pretty damn good milage - high teens with mixed driving (very spirited back-road driving) and mid-high 20's with solid highway driving. It had no problems with city driving at all. It still had very usable low-end. Just make sure you keep the aux ports operational.