Ok, brief history, Im a chick just getting into hondas, I LOVE CRXS!!!!! I need to know some info on the headers. I have an 88 dx 1.5L dpfi with zc sohc swap, but I have those little stock headers which look horrible. I need to know what a good size piping is for after market headers. I see on ebay all these measurements of 2" or 1.5" etc. And one for gathering piping. What is a good performance brand, and size, piping, that is CARB legal???? Is bigger piping better? PLEASE HELP ME BUILD MY REX!! (Along with any other things you may think are good tips)

 

1. You should post in the CRX section, this section is primarily for questions related to ECU tuning or tuning-related questions (more on the side of theory than parts).

2. Not sure if you're referring to an exhaust manifold when you refer to header (the parts connecting the engine to the exhaust) or the exhaust itself. The two are not the same, the header has 4 tubes from the engine to the catalytic converter, and then the converter connects to the exhaust; the exhaust carries the waste gasses out the back of the car to the muffler and then out the exhaust tips.

3. For your standard low-power 4-banger, you'd be fine with exhaust piping up to about 2". I'd guess you'd start to see an engine choking out on that exhaust size when you're in the 180hp range. 2.5" will be good until about 250hp or so. Any more power than that you're going to want 3" as the tradeoffs (weight, size) will be outweighed by the gains in power from going to larger sizes and turbos just love big exhausts (or no exhausts). I wouldn't put a 1.5" exhaust on anything that wasn't stock. You'll also notice some exhausts marketed as "mandrel bent". This is far superior. Typical muffler shops will take a straight piece of pipe and bend it in a machine to create your exhaust. This reduces the effective inside diameter of the pipe significantly where the piping wall bends inwards and seriously hurts airflow/power. I wouldn't consider anything but a mandrel bent exhaust - and all aftermarket *performance* exhausts will be mandrel.

Generally speaking an exhaust is tuned by its size to move the peak power higher or lower in the RPM range. If you want more low-end the engine will be happier with smaller piping but that will choke it out on the top end. Too large on the piping and the engine will generally be a dog in the low RPM range. There's a lot of other factors that relate to that... it's a gross oversimplification... but that's the most general idea.

As for brands, or exhaust tips, which is what I think you're referring to, I have no idea, sorry. I don't stay up with the current popular brands, people in the CRX forum might be able to help more.

 

Yeah, Im talkin bout exhaust mani. Thanks for all the info, very helpful