C mod class

[blueskyracer]

We are waiting for our new tach with memory to get here

[pro350hydro]

We are waiting for our new tach with memory to get here

Memory wont do much for you, as you spin the motor up pretty good getting on plane or if you hop out of the water in a turn. Need to try and mount it in a location were it is visible why going down the straight away, at least for testing. If I remember right that pipe works best at about 8,500-8,800 rpm.

How did the plugs look?

[Guest]

Recording RPM

Sam gave me a great idea on recording RPM of an engine. What we found works really well for us is to video each run while your testing. We then play it back into a laptop and use the speeker or headphone output jack to measure the frequency. Most all volt meeters have a frequency reading capability. The one I use has a digital display. Lets say the meter is displaying cycles per second so you can get RPM very easily. If you get a meter reading of 274 Hz on the unit and you have a 2 cylinder engine the RPM will be 274 x 60/2= 8,220 RPM. We now have it setup so we use it real time by using the video camera to feed directly into the laptop that we connect a VOM.

Alan

[blueskyracer]

This is what happened and I guess it was just another learning experience. In testing the boat kept surging. You could feel it want to take off and then it would slow back down. It acted like it was to lean having started with the needle setting for a stock motor. So we keep going richer but also changing props and set up but nothing was getting better.

Rather than looking at the plugs we just played with height and angles figuring it was just a matter of the right combo. Second to the last heat of the weekend I noticed that a heat on a fairly short course this year was using almost a whole tank of fuel when we use to only use about half of a tank with the stock set up. I figured that was not right at all. So we went a few clicks leaner from the stock set up and things started to improve.

At the next race we will work on getting the motor on the pipe consistantly and then go back to set up and props. We have two new props on order but will work with what I have for now.

On another note there was one bit of good news. I got my mirrors on and they helped see those E Mods coming that I had to run with and the cooling system worked perfectly. Lots of water flow. More so than the stock set up and the boat is really easy to get on plane.

Even with the problems we had fun and it was great to see the racing family again. Our CSH won so that was another positive.

[Sonny]

I start 1 1/4 turn out from closed on the needle at the bottom of the carb. I do not pull the plugs, I take the pipe off of the snout of the exhaust manifold and look inside. If it is dry give it a little fuel, if it is wet take a little fuel away. It should look like chocolate powder in the pipe when it is right. Did you try 1/4 up and 1/4 tucked? If you get that motor making chocolate powder and you are 1/4 up and 1/4 tucked and it still doesn't fly like crazy you and me will need to compare some numbers. At the back of the sponsons there is a critical dimension from the bottom of the sponson to the air trap. I would be happy to flip the c mod over and send you some pics and numbers of the bottom. It is quite a bit different than my other hydro's, it sits on the bunks of the trailer like a rocking chair and when we run it you can see clear over to the other side of the lake under it, all but the last 2 inches or so. Let me know how I can help.

[ebss011]

Cmod

Get a test wheel and pump, put it in the water, squeeze the throttle and tune the carb til it screams! good way to get it dam close. and dont forget to click it out acouple more to compensate for when your under way. Then ck
the plugs. And dont use the pipe when tuning! work for me this weekend!
TopGun 11-Z

[blueskyracer]

I start 1 1/4 turn out from closed on the needle at the bottom of the carb. I do not pull the plugs, I take the pipe off of the snout of the exhaust manifold and look inside. If it is dry give it a little fuel, if it is wet take a little fuel away. It should look like chocolate powder in the pipe when it is right. Did you try 1/4 up and 1/4 tucked? If you get that motor making chocolate powder and you are 1/4 up and 1/4 tucked and it still doesn't fly like crazy you and me will need to compare some numbers. At the back of the sponsons there is a critical dimension from the bottom of the sponson to the air trap. I would be happy to flip the c mod over and send you some pics and numbers of the bottom. It is quite a bit different than my other hydro's, it sits on the bunks of the trailer like a rocking chair and when we run it you can see clear over to the other side of the lake under it, all but the last 2 inches or so. Let me know how I can help.

Just checked the needle setting and it is one full turn out and the pipe looks like the inside of a wood stove pipe. Black and oily

[pro350hydro]

Just checked the needle setting and it is one full turn out and the pipe looks like the inside of a wood stove pipe. Black and oily

How many clicks is that?

How did you adjust it when you ran it stock? You need to do what topgun said above

[blueskyracer]

How many clicks is that?

How did you adjust it when you ran it stock? You need to do what topgun said above

About 37 clicks

[blueskyracer]

I just got the new tach so I will be installing tomorrow. Also I have lengthen the pipe 2.5 inches. I am keeping my fingers crossed for two new props. Hopefully we will be able to get on the pipe.

Next race is Memorial day weekend. Gee that is a little over a week away!

[pro350hydro]

Also I have lengthen the pipe 2.5 inches.

What part? and why?

[form-e one]

remeber the nextrace for ya is 3000 feet so will have to lean it a bit out will help ya,,, deff affects the motors that altitude..

[Sonny]

Be careful with the pipe you can do damage to the motor with it. There is some heavy physics goes into the pipe. every piece and every angle means something. If you added 2.5 inches to it I would assume you lengthened the stinger? The stinger decides how much pressure/heat the system bleeds off. To put the stinger in perspective, it's the difference between standing next to the train tracks listening for a train, and putting your ear on the tracks. You will hear the train coming from further away by placing your ear to the tracks because sound travels more efficiently through a denser material. by lengthening the stinger you are making the atmosphere or low pressure center inside the pipe denser but you are trapping the heat as well.

[blueskyracer]

If the pipe was adjustable all I did was slide the pipe back on the header just like it was an adjustable system. Now that I have a tach with leads long enough I should be able to see what is happening.

Could just be a mixture adjustment since the pipe is black inside from front to back. All changes are easy to change back.

[pro350hydro]

Could just be a mixture adjustment since the pipe is black inside from front to back. All changes are easy to change back.

What oil and what mix are you running?