The thing I like best about inertial dynos is the amount of testing you can do in a short time without putting much time on an engine. Because each run takes less than a minute including warmup and the engine only spends a few seconds at peak rpm, serious failures are rare. We usually plan what we are testing, get everything ready, and make around 40 runs in an afternoon. Sometimes we change things as we go, but usually we have a plan, such as having a series of pipes to test. Though the Performance Trends software has good graphing capacity to compare runs, I like to import the data to a spreadsheet so I can average several runs and graph with various options. All the graphs in my CMB article were from Excel. The CMB test program only took about three dyno sessions where we tested basic engine mods, pipe designs, carb settings, and liner changes. We made over 100 runs and the engine was still putting out good enough power to raise the record by 20 mph.

Lohring Miller

I had a buddy over this weekend and we disagreed on something. Maybe you guys can settle this... He came over to see how I tune my pipes. I turn the pipe backwards to avoid hitting the prop. He thinks this will make a difference. I say since the exaust is coming straight out the head it should not matter which way the header is piointed.

You don't have much choice to move the pipe out of the way, whether it makes a difference or not! ;D I don't think it makes a difference if it's at about the same angle that it would normally be (on opposite side). Maybe Lohring has done some more extensive testing and can come up with a definitive answer...I can't.

I think there are a lot more significant things that affect power than which way the pipe points. For example, the rear exhaust Quickdraw we ran in our Eagle rigger with a straight exhaust, full circle crank, and electronic ignition had LESS power than the carefully selected side exhaust Quickdraw using a standard Zenoah crank and ignition that we ran 110 mph with. I have no idea why this was, but it shows that lots of little things go together to make a good engine. Acceleration runs between an average engine and a good engine often differed by 5 mph peak speed at 100 mph. Quickdraw has found that the cylinder hone pattern can make a 1/4 hp difference. Nitro racers find that the piston to sleeve fit matters more than many other factors. In heat racing these things won't matter, but it shows up in SAW racing.

Lohring Miller

I agree 100%. The reason this all started is because my buddy got a new full mod engine. He wanted to just bolt on his old pipe without testing or tuning. We tried his old 2" band pipe and got good results. Then we tried a pipe I had made that was a bit shorter and 1.5" the motor just screamed and had better power over a broad range. He refuses to believe a smaller pipe can give more power. :o;D ;D ;D

Greetings RIGGERMAN! I run a custom water brake dyno for all my pipe work. Make sure you are carefull with inertia type dynos!!

Hi Bruce

Do you have any photos of your Dyno

Regards Colin

I often thought about using one of our old formula V water brake dyno's and building a belt drive reduction /adapter to get the rpm and torque into a usable range. With a properly designed and aligned tooth belt drive there should be a fairly low % of loss. It's all relative anyhow.

I build my own dyno , performancetrend software , dyno wheel is 304 stainlessteel out of one piece including axels.

ratio from engine to wheel is 2:1 , in the program you can select a slip graph , from moment that the clutch is engaged the ratio is 2:1 to 2.02:1

short movie:

JohanD

Very nice !!! .... see one of Jeroens pipes ;D