Ok so my miata isn't the prettiest girl on the block, she has rust in the rocker panels (thanks to improper cleaning of drain holes) and its basicly going to be a track car so interior is gonna go aswell as other things.

The issue at hand is figuring out a way to get my exhaust to exit thru my rocker panel, like GT cars

So my options are:

1. Run the pipe under the frame rail and then out the side under the rocker panel.

2. Run the pipe under the car then up thru the floor over the rail esentially then out the side of the rocker panel.

The first one won't even work ( I don't think) because I'm running a 3in downpipe and hopefully 3in exhaust, if not then 2.5inch. My car is lowered(only an inch) so I'm thinking it will bottom out if its under the rail.

So can I run it over the frame rail? I looked but I'm not exactly sure whats all in that area of the miata, open space hopefully

Can it be done?

 

this is where oval exhaust tubing comes in!
http://www.drgas.com/store/home.php?cat=8

I plan on doing this with a 2.5" system but not through the rocker, just right under it.

Either way you put it, if you run it under the frame rail you will decrease the ground clearance. If youre going to pop a hole in the side of the car that would be interesting...i havent taken a peep at the underside in that detail.

 

There were good pictures of someone who did this on miata.net a couple of years ago. I think he had to build a muffler from scratch.

You plan on making it a track only car? Where are you racing it, at the drag strip?

 

i would run it out the drivers side in front of the door, out the front left fender. get ear plugs.

 

lol kinda why I want it behind me, its going to be bad enough there though.

 

Thats what my friend had done on his daytona. He had the pipe ovaled and managed to get 3in pipe to fit, just barely though. Its not lowered and rubs on medium sized bumps.

I have to get rid of the rusted rockers anyway, so if I run the pipe thru there I can just rivet an aluminum plate there and it should look half decent.

 

I've seen the side exit under the rocker but not thru the rocker..No its not a drag car silly.:gay:

 

I'm planning on running a large exhaust on mine eventually... plan is just a single resonator (3in) and run it straight pipe style past the diff and out the middle of the rear bumper. Straight flow is my focus.

Just not sure its worth cutting out ground clearance if you bring the pipe below the chassis. Or, bringing it and the heat up into the car interior to put it out the side.

 

This was notched through the rocker. So if not a drag car, what kind of racing are you doing?

Depending on the kind of racing you are doing and where running an extemely loud car may not be allowed.

Jay

 

i don't know. i would just run it straight back, no bends.

 

It seems like alot of dead weight running a full exhaust system.

Does anyone know if there are any critical parts in the area behind the driver seat, I would imagine I'm going to run into the gas tank real quick if I go that route.

 

Ultimate weight reduction... open headers :gay:

Seriously tho.. I gotta go w/ Kung Fu on this one and say prolly the best option (for weight and ease) is before the doors.

 

But my front fenders are the only things that are in good shape...

 

is there anyway to get a muffler in there with such a short exhaust?

 

Look here to see what I did (dumps out right behind the seat):
http://www.lightweightmiata.com/exhaust/exhaust.htm

I spent a couple of days under the car trying to figure out how to make it side exit without losing all my ground clearance but there just isn't any way without cutting your rocker panels (and then you will still lose a lot). Just dump it out under the car and be done with it. I know you want it to look cool but sometimes you just can't get it to look the way you want.

 

So easy to loose weight somewhere else, I wouldn't do the side exit thing to save weight. Looks ok, but really you could take a really long **** and loose as much weight as you would by doing the side exit thing. If you really want to save weight on the exhaust go with 2.5" instead of 3". You aren't going to make enough power to justify such large exhaust piping.

There is some room behind the driver's seat, your problem will be getting the exhaust over/under the frame rail. I would seriously question routing the exhaust in the cabin of the car, a leak could be very bad. And the chance of fire would be there too. And if you are thinking about coming over the frame rail and into the cabin of the car, you'll be introducing extra bends into the exhaust.

You want quick and dirty (and LOUD) go from your downpipe to a length of pipe that takes the end of the exhaust just behind the driver and use a turn down. No bends (aside) from the turndown, would probably the most free flowing you could do.

It does look cool, but I wouldn't expect it to save weight or give any bennifit beyond looking cool.

 

Sorry turndown exhaust is not even an option, I do not like it in the least of ways.

 

That sir is blasphemy. What power level is sufficient for 3inch exhaust then?? I have stripped alot of weight already of the car, not to mention I'll be running a full aluminum exhaust(including custom muffler) so I'm not going to ignore the savings availible in the exhaust sytem.

Frame rail s no longer an issue. I have figured out how to do it, its just a matter of cutting the rocker properlly. Thanks for your suggestions everyone.

 

Well Corky Bell has said that 3" exhaust is too large unless you are planning 600hp. There was a recent thread on miata.net about it. Take his comment for what it's worth. But Corky does seem to be somewhat of an expert.

http://forum.miata.net/vb/showthread.php?t=194488

What weight savings have you already done? Unless you are going extreme the little bit saved from 2 feet of aluminum exhaust is non-existant. How much to your wheels weigh? Point is there are lots of better places to save weight than your exhaust system.

The only time I see people talking about weight savings on exhaust is stock autocross where weight reduction isn't allowed, but replacing the catback is. So people go to big extremes to save a couple of lbs. It can make a difference, when the difference between 1st and 2nd is messured in 100ths of a second.

What kind of racing are you doing with the car?

 

Well I'll take Corky comment for a grain of salt because I've seen dynos where 3inch exhausts on 200whp cars made a good difference.

Well I'm basiclly gutting the car so yes that little bit of pipe will matter. The car is going to be lapped. All my rims are 12lbs or under (I have 3 sets).

edit: Jay you do know Im not running a 1.6 with a greddy right?