Example of Induction and Exhaust Tuning

[VRYQUIK]

Example of Induction and Exhaust Wave Tuning

The bike used in this article is a perfect example proving how that adjusting the timing of the induction and exhaust waves, can increase power. Keep in mind that this is just a crude way to tune these waves and that if done properly, there will major increases in power. The correct way to time the wave is by modifying the induction system from the beginning to end and the same is true for the exhaust. Please read the "Induction" and "Exhaust" articles on this website for a better understanding.

Keep in mind that if these waves are timed correctly, it will increase power. If the waves are not timed correctly, it will decrease power. This is the reason that some engines using a certain cam and exhaust, will make more power than an engine using the same cam with a different exhaust.

The bike being used is a 2002 Ultra Classic, 95 ci, 50 mm T/B, SE 203 cams, V&H Pro Pipe (designed for a Softail) with a modified tail section. I started by dyno tuning the bike.

Induction

Here is the graph after the dyno tune.



Next, I removed the SE air filter and performed a dyno run.
It gained about 2 TQ & 2 HP at 4000 RPM (92 TQ / 70 HP)
indicated by the lower lines of the graph.



Next, I installed a velocity stack, shorting the stack a little at a time while dynoing the bike each time the stack was shortened. Each time I shortened the stack, I noticed an increase in peak TQ until the final trim, where the TQ started to drop. The peak TQ was 100 TQ before the final trimming of the stack. The results are 97 TQ and 75 HP at 4000 RPM as shown by the upper lines on the above graph. This also proves that if you increase TQ...the HP will follow.
Also notice that the AFR leans as the power increased. This is because the volumetric efficiency has been increased causing a lean AFR.

Exhaust
Have you ever noticed a chrome exhaust that has discolored areas up and down the pipes? Most people believe that this is caused from a fuel mixture that is too lean or too rich. The correct reason for the discoloration is due to the exhaust waves traveling down the pipe and colliding with the waves traveling back up the pipe. There is a lot of heat that builds up in this collision area causing the pipe to discolor. This collision also restricts the exhaust flow and lowers the volumetric efficiency.

These pictures show the discolored area of the secondary pipe. I cut the pipe at the discolored area. In theory, this will remove the collision area and increase the volumetric efficiency of the engine in a particular RPM range.






Here is a graph of the bike after the pipe was
cut off and the mixture was corrected.





Compare the before and after graphs. Notice the increase of TQ between 2000 - 3750 RPM.

Also notice that the exhaust has no restrictive baffles. This also shoots down the theory of "adding back pressure" to increase power. If the exhaust and cam is properly tuned, you will have no need to add back pressure. Adding back pressure to an exhaust (restricting the exhaust) can have a positive effect on power sometimes, only because it is slowing the exhaust waves down to match the cam timing. When you slow the exhaust waves, you also lower the VE of the engine, It is better to tune the pipe without restrictions to keep from loosing volumetric efficiency.