Engine Modification Effectiveness

Modification Effectiveness

I was wondering whether or not certain mods to the Corolla make a significant difference. I have a 1999 Corolla, so I'm mainly talking about the 1ZZ-FE engine, not any other variant.

According to http://www.corollaperformance.com/TechInfo/1ZZFE.html, the factory headers are pretty much optimized. "On the exhaust side, the exhaust manifold is a very short, four-into-one tube header. The primaries are too short for proper pulse tuning, and that's not likely to change due to the close proximity of the catalytic converter and the fact that there is a flex joint right after the collector, making building a header any better than the factory piece quite difficult." Do you think changing the header would make much of a difference?

Also, I know many people say that cat-back exhaust systems are significantly better than just an axle-back muffler. This is questionable though. Again, according to the site, "Aft of the header, there is another tuning complication. The catalytic converter is welded to the exhaust pipe, so cat-back exhausts will either be a muffler-only affair or will have to be a cut-and-weld installation. On the plus side, the exhaust pipe appears reasonably free of restriction, so a muffler-only exhaust may be good enough."

What do you guys all think? Is this site accurate, and if not, do these mods actually make a significant difference? Thanks for your input.

I'd get a CAI... P&P the head. People say a header is worthless. 2 1/4 catback... if you want more power than that.. go forced induction or get some nitrous.

Thanks for your input. I have another question. I have a TRD muffler on my Corolla. I think the exhaust tip is a bit too large, though. I would like something a bit less conspicuous. Is it possible to switch that tip to a smaller one, say like 2 inches? Thanks again.

Thanks for your input. I have another question. I have a TRD muffler on my Corolla. I think the exhaust tip is a bit too large, though. I would like something a bit less conspicuous. Is it possible to switch that tip to a smaller one, say like 2 inches? Thanks again.

Chop it off and weld one on Any muffler shop can do it .. probably like $20 + cost of the tip..