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ECP Dyno Session - Fall 2003

I went to ECP "Freddie's" to learn the most details I could about the 440 engine. What I learned here has been most beneficial to learn how to build the best clutch kit possible for not only the 440 sled, but for any sled that we test and build a kit for.

I was told I would learn to:
    Find my sled's available power
    Find proper race fuel to run my engine
    How to operate the sled for optimum performance.

Freddie is good at extracting information from a customer. The first of the talks on the phone and emails about what you want dyno'd is somewhat of an education process for him to get valuable clues of what your engine will be like and what you know about it. I was lulled into a rhythm of questions and answers of what I wanted to do with my sled and what I was willing to do with it displaying my commitment to finding the character of the engine. I couldn’t wait to let him see my stocker.

He tells the basics of how to build horsepower to his customers and they learn his trade, so now the customer is bound to get better with this information. What has happened for me here was not only learning but has raised more questions and umpteen ideas are going thru my head of how I’m going to clutch my sled. In the future, the next problem I get, I might find to be much more difficult but interesting. It is an excellent way to grow in knowledge, make a good friend and at the same time learn a lot of new solutions. What notes you take and the information you give almost always grows bigger when it bounces back.

So we're going to simulate runs as if at the track. We'll start the engine, pull a dyno run, kill the engine then cool it off to a good temperature that I will have time allotted to do at a hectic race.

Quoting SUPERTUNER:
"You need to know what to do in a drag race environment where we make heat after heat, you cool the engine between heats and because your pipes are thermally efficient in that they have been heated once and subsequently heat easier the next time, when the pipe heats up it creates a loss in how much time it takes to accelerate (low end torque). There is almost always a trade off of low-end torque for top end RPM. When you know this, you could operate the sled properly and gain some of the best of both of these worlds back. The problem is we cannot control how long we will be held at the line when someone takes their time or bumps the clutch or whatever.

People learn to take advantage of that torque in the hole shot and then change the clutch tune-up at the top end to allow the clutch to keep the engine in the RPM range that occurs and changes as you go down the racetrack while adding heat into your pipes. This is where progressive helix's come into play. Load heavy at the beginning, and then drop a few degrees in angle as the shift plays out.

Now of course this varies from sled to sled...in an open modified with no hood or with a sled having lots of vents in front of the pipes. O.M. sleds, the pipes run cooler due to the wind hitting them and assisting with their cooling as you run down the track.

In a case where you have a full-bodied sled with a heavily shrouded and concealed pipe, you don't get the wind and the under hood temperatures become "sauna like" resulting in a scenario where you need to clutch for a low-end torque loss and a top end RPM gain. The deal here is doing exactly the same thing every time between rounds, heat the sled the same amount on the jack stand, stage for the same amount of time and get the same repeating results every time."
End quote:

The Dyno:
The dyno is an Inertia dyno. Unlike an Eddy Current or Water Brake dyno where you load the engine at peak and pull the engine down in rpms, this inertia dyno has a 1200 lb drum that has to be accelerated. The engine accelerates the drum from idle to peak rpm. This will simulate the actual environment that the engine will be run in. A direct connection from the drum to the engine is made via a clutch stub that has a special coupler, which is designed to free wheel when the engine is shut off. The dyno is so accurate and software so powerful that you can measure 10ths of a HP and prove this by "repeatability" runs.

The Dyno software displays two forms of visuals for the customer. One page is a plot form that shows the torque and hp curve lines. The right side of the page shows torque values in ft-lbs, the left side of the plot shows graphic values in Corrected Hp, the bottom of the page shows the rpm.

The optional page is a raw-data sheet. This data sheet is a table of numbers with 6 columns of i)engine rpm, ii)Measured torque, iii)measured hp, iv)corrected torque, v)corrected hp and time in seconds between each sample interval.

The sample intervals can be 1000 rpm, 100, 50 and 10 rpm if you like. You can get enough data that will make your head spin. I think for me personally that 50-rpm sample intervals are about fine enough resolution.

The Dyno Session:
I pulled in with the sled jetted for Yellowstone Mountains. The mains were 210's and the engine at that time in the mountains was gulping C-12 fuel. I just give the engine a refresh with new pistons/reeds/seals and used 92-octane/premix fuel to give it a shakedown run.

Freddie popped the primary off, connected the dyno jackshaft and said we could do a few runs with these jetting details to see its character on that fuel. I said NO WAY, we cant do that? I know of guys including myself who burned down these engines with 290's and 92 octane. He mentioned that we probably burned down at near w.o.t runs. I concurred. This should not happen in an acceleration test of less than 10 seconds. So with an anxiety knot growing in my chest, Freddie spun up the dyno and started the engine.

Running the engine near idle for a few seconds, he then pinned the gas and started the dyno to sample. I was literally gripping my chair waiting for a "SQUEEK". I must say that it was scary to listen to the engine grunt from idle to 8500 rpm. It took about 9 seconds to grind out a run. After killing the engine, I connected the cool-down cart. Freddie pulled up the dyno run and looked at the curve. Said about 84-85 hp on that run and he did not like the shape of the torque curve climbing to peak hp. The curve climbing from 4000 rpm to 8200 was in the shape of a smile. This is not what a tuner wants. That curve shape represents that the engine is not building torque quickly.

"Pull a plug, Joe" Out comes the plugs. "Too rich. I said "WHAT?...Too rich?" "Yeah, you watch, lets do another run to prove it." Next run while he's loading the engine he gets me to look at the exhaust spout and it was just slobbering. After the run, I pulled the plug and looked at the wash. He's right!..."Rich. Same hp, between 84-85 hp.

Now it was time to change over to race fuel. VP C-12 fuel went in at 40:1 premix. Another dyno run and an instant 5 hp to about 90 hp. Still had a smiley curve so we had some work to do to clean it up.

I have 3 cd boxes here. The timing is modified in two of them. Not sure on the specs, but one has a quick advance, one has a quicker advance and the 3rd is stock. Just doing cd box changes, the Quicker advance made less hp in a pull accelerating from 4000 to 8200 rpm, the Quick advance made just a little more hp in a pull accelerating from 4000 to 8200 rpm and the stock made the most hp in its pull from 4000 to 8200 rpm. What did not change much was the peak power at 8200. It was the torque rise thru the rpms that was higher, the closer I got back to stock ignition.

On some more runs we kept checking the plugs and piston wash. Just for the heck of it Freddie changed the gap, thus opening it .004" more thou from factory spec. One more dyno run and it showed 1.2 more hp accelerating the engine. Since this was an obvious change from the last we did one more run to verify. Yep, same thing. Over 1 hp gain with a change in plug gap.

Thru this whole time the temperature was around 83 to 85 degrees F. After each run I cooled the engine down. I got to learn how much ice to use on my Cool-down-cart and found how much time it took to get my engine to a "race-ready" temperature. My engine after a run takes around 1 minute to get down to 100 degrees from a full pull.

The complex of characteristics that this engine seemed to like was the timing of the stock cd box, the octane of the race fuel, good plug gap and a certain race-ready engine temperature.

Totals of these details behavior produced the least emotional torque curve with the most average hp out of all the runs.

Now what we want to do is find how we can make the curve emotional again to produce a frown. Engine frowns = Owner Smiles. When you have a frown there is more area covered under the curve, this means you produce hp quicker per rpm.

Another detail that affects the torque output is the rave valve settings. After a bunch of runs I measured that the rave was on #10 notch. I turned it out to #15 notch and pulled a run. We lost hp accelerating from 4000 to 7600 but the peak hp was nearly the same. Next setting was to turn the rave out to #20 notch. The engine lost even more hp from 4000 to 7600 rpm. Ok so we thought there was no use going to #20+ notches, so go back to #10 and maybe even close it up to #9 notch. Well "Whammo!!!!" Another 1hp thru the midrange rpms increase over #10 setting with hp staying the same at peak rpms. The rave valve made higher torque thru the midrange rpms by tightening it up.

Just to prove about a Power Valve Freddie Elaborated on a 440 Polaris engine and had the data to back it up.

Freddie Discussion: I struggled to get any improvement whatsoever from the engine for 23 dynoruns. I was failing miserably at even coming close to what Polaris said the engine should make. By dynorun .022, the best I could extract was 52.1 foot-pounds of torque and and 83.5 HP. At dynorun 24, and because it was after all a small engine I began playing with the power valve and wham!!!...An immediate 12 HP gain when I found that sweet spot for the power valve setting!

Carburetion:
What is general knowledge of most 2-stroke reed or rotary valve engines is that they make better low-end power with rich jetting thru the lower end circuits. My engine comes stock with 25 pilots and recommended 250 jets. We did runs with this configuration all along. Time to start changing details. I went down to 230 like Bomber recommends in their new "Tip Sheet" for drag racing. Pull a run, more Hp from 250 jets.

I know from field testing that going up in the pilot size seems to produce a better hole shot in sno-x and in extreme trail riding when you accelerate in low speeds, you punch on the fuel, a larger pilot seems to make a difference in pull.
We went up in the pilot size right to a 35 and Freddie noticed that the engine idled terrible. "I can even feel it in the handlebars...BLAH!" Time to sample a run. The engine plowed thru the rpms accelerating the dyno. After killing the engine Freddie looked over and he could see several feet away from the screen that there was another curve higher than the previous pull. Looks like we made an average of 1.2 hp across the whole rpm range of 4000 to 7600-7800. One more pull for repeatability and voila...Repeat HP.

One thing that was distinct was when you look at the Numerical data, there seems to be a small range of rpms where the engine stays the same hp with even a smaller pilot jet. The numbers state at 4300 rpm the hp starts to climb and maintains a higher curve right to near peak torque. We increase pilot size and the hp increase starts at the same rpm every pilot size.

My question is should I be clutching for engagement here in certain disciplines, thinking that the HP will build quicker here? ...Interesting to say the least.

Air Filter:
We did the dyno sessions without any filter or airbox. Figured we'd try to extract everything we can from changes and get a repeatable run, then install the filter. At the end of the day for the last two runs we installed the kicka$s filters and lost a total of 1.2 hp at 8200 rpm. We did two runs with the filters on for "repeatability" hp reading to make sure it was not a fluke.

Freddie has done a lot of dyno tests with the filters and loses about 1% per 100 HP. Like SUPERTUNER says, "These filters are truly kickass!". But he further says if you are going to use them on the trail, don't count on them doing a better job than the air box. Generally a filter does a better job of cleaning air when you lose HP. You can gage filter brand for filter brand by HP loss.

If for trail purposes, I recommend to use K&N "Pre-Filters" which are pink/purple colored bags that wrap over the filter and are tied with a string. This will eliminate at least the water/moisture that is in the air but possibly not finer materials.

Air boxes do a pretty good job on newer sleds. The effects seen on most sleds on the dyno will actually make more "Average" trailable hp letting the engine offer more torque thru the midrange rpms. You might lose a hp or two at peak, but will gain 2 to 4 hp in the lower rpms.

Conclusion:
Looking at the final dyno curve now the curve is quite the emotional one. Instead of a simple smile shape curve, the engine now has a series of small frowns. More area under the curve, more torque. I not only have a gun, but also now I can point it loaded with ammunition. Knowing the character of my engine and how the character changes with details a novice or pro tuner can perform, i'm not just shooting at a wall. This dyno session has given me the light to see the target on that wall....oooh, can you say "recording tach?"

What you learn here and the questions you raise, you get new thoughts and ideas, but more importantly, you get "Value Added Comments" From Freddie to clear things up. Damn, my head is just spinning with ideas on how to clutch to the average hp.

Freddie comments:
This season you may have been hearing about Chuck Hamrah's 1000 Pro Stocker. It set a record at every event it went to! Why?...because we knew exactly how to handle the massive power and believe it or not, we went quicker and faster when we took power away for the first 100 feet of the run. Your little 440 is the exact opposite because it simply doesn't have the luxury of having to "bleed off" some power.

Regardless of engine, you will learn it's personality, figure out it's average HP and know exactly what rpm to clutch to.

***To ask more questions about the Baddest dyno on the planet, Click on the ECP link.***

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