Here we will discuss the Tuned Exhaust systems available for Nitro Cars and Trucks. F
irst, why a tuned exhaust? Well, the best reason I can think of is CHEAP power! According to RC
NITRO magazine, a properly tuned exhaust will increase you output up to 87%! Now that is major bang for your buck! A stock
exhaust system is basically a muffler and a way to direct gases out of the car or truck. On the other hand, a Tuned Exhaust,
(pipe and chamber), actually work to supercharge the engine. It also smoothes out exhaust traveling through the pipe. The
easier it flows, the faster the fresh incoming charge can flow. Here is an example of both a stock exhaust and a tuned system
ou will see the
stock piece is nothing more then a can with a stinger pipe on it, and a baffle to cut down the noise. In the tuned system
photo, you can see it has a free flowing header pipe, and a specially designed chamber.How It Works Y
ou will notice that the chamber is small on the engine side, (left side in photo below), and tapers
wider up to the stinger pipe. (Small tube coming out the side of the chamber) At the end of the pipe, you can see that it
tapers down very quickly. This is called the convergence cone.
When the piston is on the down stroke, both intake and exhaust ports open up, exhaust is
forced out and a fresh charge is drawn in. When this happens, the taper in the first part of the chamber lets the exhaust
pulses and gases to speed up, creating a negative pressure in the pipe, which in turn pulls the exhaust out of the cylinder
and pulls the fresh charge in. When this happens, the negative pressure will pull fresh fuel into the exhaust pipe. Now the
good part. Remember that convergence cone that was mentioned? Well here is where it works. Exhaust pulses travel at the speed
of sound, while the gases travel much slower, so the pulse hits the convergence cone first, reversing and it creates a positive
pressure in the pipe. At this point the piston is moving up in the cylinder, and the intake port closes first. The positive
pressure in the pipe pushes the extra fresh fuel that was pulled into the pipe, back into the cylinder packing it in, or Super
Charging it. This is where we gain all that extra horsepower and torque!How to tune it O
k, that's how they work. Now how do you tune it?? You can tune the pipe for low end or top end power
and speed. Read on!
- If you run on a track with short straight aways, you want the low-end speed.
- If your track is
large with long straights, go for the top end tune. Here's how.
For low end speed: M
ark off about 60 feet on the ground. Have a friend stand at the finish end with a stopwatch. Run
your car or truck and have him time it. Now, remove the chamber from the pipe and cut 1/8" off of the pipe end. Put the chamber
back on; make sure you push the chamber all the way into the silicone coupler until it touches the pipe. Now time the car
again. Any faster?? Ok if it is, take off the chamber and cut another 1/8th" off and do it again. Repeat this process until
you see no increase in speed, or it slows down. Now if it slows down what does that mean? You cut too much off! No big deal,
remember when I said make sure you push the chamber into the coupler until it touches the pipe? Here is why. If you cut too
much off, simply pull the chamber out of the coupler a little to lengthen it!! When you are all finished, secure the coupler
to the pipe and chamber with zip ties.
For top end speed: A
for top end speed, it is easier. Mark off about 120 feet and do the time trial. Then just pull the chamber out of the coupler
1/8 of an inch and time it again. If you run out of coupler before you reach the fastest time, just buy a longer piece of
For Low-end speed and torque: Shorter pipe
For High-end speed and torque: Longer