My Metro's new exhaust!

[dwendt1978]

About 2 weeks ago the Metro developed an exhaust leak at the drop down pipe where it's connected to the manifold. The guy before me snapped off the spring bolts and he bolted the exhaust direct. Causing enough stress over time to crack it.

So on my way to work the other day it finally gave way and hit the ground! So I ripped out my speaker wire and used that to tie the exhaust up and head home to get the gas pig (my truck).

I went to the junk yard and got a used manifold with the drop down pipe. Bought a 10' section of 1.5" tubing and a new muffler. Upon taking off my manifold, ofcourse 1 damn bolt snapped off in the head! So I called my brother-in-law and he come over right away and had it drilled and heli-coiled in about 20 minutes! Dang he's fast. Anyway here's some pics.

Here's the heli-coil installed.


I decided to weld pretty much everything. Not a bad job I thought.




In this pic you can see where the muffler would normally sit. Way to thin from rust to weld. So I used a coupler and piece of pipe, cut out the bad stuff and installed and welded the new pipe.




Here's an overview shot.



Only thing I don't like is the gassy smell from not having a cat or resonator. At 55mph the car is AMAZINGLY quite. Not a clue if I'll see in increase in mpg's but the car is MUCH more peppy than before. I installed a new O2 sensor while I had to go through all this. Oh, and did I mention the car is used strictly for off-road use!!

[Johnny Mullet]

Looks like what I am about to do to my 1998, but I will be using 2" pipe on mine. So the car is pretty quiet until you open her up?

[91Caprice9c1]

That looks fun - much cleaner and more streamlined compared to the factory stuff with the cat and resonator between the manifold and muffler. It was a wise move on your part sticking with the factory pipe diameter when removing the intermediate components - you must retain some back pressure.

I've read the factory exhaust system on these cars is very restrictive, I'm not surprised you noticed a difference, especially minus the cat.

Any special brand muffler? Where'd you pick it up from and how does it sound under hard acceleration?

-MechanicMatt

[dwendt1978]

It's a Parts Plus muffler, which I believe is Napa.

All joking aside, it sounds like a 125cc dirt bike when you get on it. Turns alot of heads which is funny. My brother-in-law when we got done said "Take it for a spin and drive by the house, I want to hear it", and when I came back he was about on the ground laughing at how it sounded.

I bet I removed a good 30lbs of junk with the resonator and cat.

[RossT]

Nice, thanks for posting the pics!

[DOCTORBILL]

"...on my way to work the other day it finally gave way and hit the ground!"

"...At 55mph the car is AMAZINGLY quite."

"Oh, and did I mention the car is used strictly for off-road use!!"

I am confused....or was the smiley face to mean you are joking...? (I am slow).

If you are serious - what the Baja 500 !? WHERE do you work?

This little bugger is so low to the ground, it would bottom out on a cigarette butt!

I like your home grown welding - wish I had learned how to do it - too old now (65).

I have a buzz box and an Oxy-Acetylene torch, but can't seem to weld anything
w/o it looking like some dull witted ape tried to do it.

Also, that "Heli-Coiling" business...I've seen it for sale - does it work as advertised?

DoctorBill

[91Caprice9c1]

There's nothing wrong with heli-coils so long as the spring stays in there. TimeSerts on the other hand are a far superior thread-repair solution. Sturdy, reliable and wont back out. Time Serts are the best. http://www.timesert.com/html/faq.html

Order them at your local parts store.

-MechanicMatt

[Crvett69]

really not sure why people think a car needs back pressure to run right. its a air pump so more you can run through while maintaining correct fuel/air ratio the more power and more efficiency it will have
try this article for a more in depth explination

http://www.dsmtuners.com/forums/freq...kpressure.html

[Johnny Mullet]

Originally Posted by Crvett69

really not sure why people think a car needs back pressure to run right. its a air pump so more you can run through while maintaining correct fuel/air ratio the more power and more efficiency it will have

I have heard that these little engines need backpressure also, but when I removed my partially clogged cat on my 1998 Metro, this little car really came to life.

[91Caprice9c1]

Great article. It cleared up a misconception I had about back-pressure and exhaust scavenging. It did show however, that by reducing backpressure, one also reduces gas velocity, thereby reducing scavenging. Showing that, similar to camshafts, there is a compromise to exhaust pipe diameter; smaller pipe does well at low engine speeds, bigger pipe does well at higher engine speeds.

There is still too much of a good thing though. Imagine a 5" pipe on a metro and lets say we get near zero backpressure at WOT. Well for the displacement deficient metro, it's not going to generate the nessecary gas velocity nessecary for good scavenging at any RPM, no matter how high you wind it up. This would result in poor low-end performance and less than optimal high RPM output as well.

-MechanicMatt

[dwendt1978]

Just an update on my car's mpg's. Last tank with cat & resonator on it netted 48.3 mpg's this first tank with new exhaust netted an AMAZING 54.68 mpg's! Both tanks were over 400 miles. I'd say thats an impressive gain.

I've noticed the car pulls hills now without losing the speed it once did. This definitely helped me out.

[leonbentz]

Excellent job on the exhaust dwendt1978! It looks like something I may do some day. I did have a new muffler and cat put in, since I've owned mine, but with DEQ and all, it looks like I may have to stay with what I have.