exhaust and muffler for a 1990 Geo Metro base model

[90metro]

Hey all,

I've been told that the Geo Metro's have an exhaust design flaw in which the exhaust gases don't expel properly, causing the head to overheat and all sorts of problems. They said a larger muffler would solve this problem. What have you all heard (if anything) about this, or is it myth? Thanks.

David

[Ryland]

I have never heard of anyone with a stock muffler having this problem, but I have noticed that auto part store off brand mufflers do tend to be made with larger pipe so they can make a "one size fits all" and to large of a pipe will cause the exhaust system to no longer be in tune.

[hummingbird]

Ryland, pardon my ignorance, but what is exhaust 'tuning'? Could you please elaborate? Thanks!

[dcb]

try this link

[MetroMPG]

David, are you sure you're not thinking of the EGR passage coking up, potentially causing a burnt exhaust valve in the middle cylinder? That's the only exhaust/head related problem I'm aware of for these engines.

[some_other_dave]

Originally Posted by hummingbird

Ryland, pardon my ignorance, but what is exhaust 'tuning'?

Generally, it is modifying the exhaust so that it helps the engine produce more power or more torque. There are specific ways of doing that, including pipe length and diameter, the exact geometry of junctions of the pipes, what pipes are joined to what other pipes, and so on.

In general, most "tuned" exhausts out there are completely irrelevant to our needs. They are almost all optimized for high-RPM power, and many will sacrifice low-RPM torque, and reduce the efficiency of the engine in the RPMs where we typically drive.

-soD