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Heywier427 New Reader
2/12/24 5:36 p.m.

A post shared by Fitilla 007 (@fitilla007)

Is venting exhaust gasses under the car/not going all the way to the back creating too much dirty air under the car?

2013 Honda Fit. K24 engine.  Beginning stages of aero (available bolt on wing & front splitter).

In an attempt to save weight, exhausting under the b pillar line is what we are doing.  Small turn down to push it out towards the rocker/pass side of car.

Exhaust is aluminum pipe and muffler from downpipe back.  The exhaust routing  of a honda fit is 90 degree angle galore, as the fuel tank is centrally mounted under the car (under rear passengers feet/ front occupants butts.

Car is fully gutted/cut, and only made for club racing/no rules.

Interested in adding more aero this season.  Doing much interneting and reading. lol.

Thanks. Tom.

stafford1500 GRM+ Memberand Dork
2/12/24 6:07 p.m.

There are lots of other things that are making the air under a car aerodynamically messy. The effect of pumping high energy air under the car could help drive downforce (as in a blown diffuser, but less effective) but keep in mind that assistance all goes away when you lift off the throttle.

My suggestion is start with what you have in mind but be ready to add some extension either to the side or rearward if you have any hint of exhaust gases getting into the car. Keep you nose open, you don't want to gas yourself at speed.

Heywier427 New Reader
2/12/24 6:21 p.m.

Thanks for the heads up.  Been running like this for 2 seasons with the stock 1.5 liter engine with no signs of exhaust smell in the cabin.

Adding 120 hp this season, so grip is going to become an issue!

The underside of the fit is really flat for what you would think.  The entire center is a flat plastic pan (protecting the gas tank and gas tank filler pipe), the front is all plastic panned up.  The only area is from the rear beam back (and the exhuast route).

We have already cut out the tire well, and added a flat plastic sheet from just beyond the beam, tying to the rear bumper.  We are probably going to make a diffuser at some point.  The room is there for it.

Good to know the additional exhaust gasses may be helping!  

Do you think keeping the 45 degree turndown towards the rear of the car is more beneficial than kicking it out the side?  We have to turn it back in at some tracks for noise restrictions.  Maybe its better to just it exiting out the rear.


BillKeksz New Reader
2/25/24 10:28 p.m.

Just a reminder that CO is odorless...

APEowner GRM+ Memberand UltraDork
4/8/24 10:15 a.m.

Exhaust is also corrosive so dumping it under the car is a great way to corrode the floors.

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