Low budget comparison Dyno results
 

Before recently modifying my stock '79 SC muffler and cat, I decided to do some stopwatch testing in 2nd gear noting outside temp. The goal was to create a set of baseline numbers to compare against any mods I do in the future. Sounds cheasy but I found it to be repeatable.

I do not have my original full numbers with me but I will post results of a quick test this morning as an example.

The simpleton test is as follows:
Attain 30 mph constant speed then simultaneoulsy mash the throttle WFO and start your stopwatch. At 60 mph stop the timer and jot down the time. Mine = 4.1 secs @ 70 deg medium humidity. Repeat a couple times to ensure consistent results (mine were suprisingly consistent).

To check low end verses high end power, test again still in second gear, @ 30-50 mph and 40-60mph. (I do not have my numbers w/ me to post, but again they were consistent).

After altering my muffler and cat, suprisingly my numbers remained basically the same although the 40-60 (high end) showed a very slight (.1-.2 sec) improvement.

As simple as it is, I think this is a very useful thing to do to establish a base line for your car before making changes. (keep in mind temps and humidity need to be similar when doing these comparative tests)

Sounds like a great "low budget" test to me. You certainly can't beat the price!

Surprisingly and disappointingly...;)

I've done the same thing, but on a piece of road with the physical starting and finishing points used to start and stop the stopwatch. Also, a pasenger is handy to operate the stopwatch. You just have to have the same passenger each time, and hope that they have not gained or lost weight in the interim. In my case, the chosen distance was around 1/4 mile =/-. Just by changing my muffler I saw a 1 1/2 second difference. The advantage here is that the amount of time is great enough that the inevitable imperfection of getting the stopwatch started and stoped is less significant. The disadvantage is that there is a very slight risk that you might do something illegal. Not that it happened to me.....

I was shocked by the repeatability of my results (I assumed that after a couple tries, I would wide variations). Starting the watch dead nuts at throttle application is a no brainer and suprisingly hitting the stop button as 60 sweeps past was very accurate.

Oh well, as simple as this is, I never thought to try this in all my years of screwing with cars. I just thought it might be of value to someone else who is contemplating making some changes.

Edit: I also thought it would be interesting to see what others w/ same stock gearing were getting in the same test. (I realize tire size/pressure and temp/humidity will vary, yet it would still be fun to see some numbers!)