Some extra power from modding your headers

[Augusto]

This post was done in 2005 !!!

In the never-ending race to get the last bit of juice from our engines any increase in performance is always a good thing. This one is a pretty simple one and for nothing but a bit of work you'll get rewarded with some additional power.

Just wanted to share a tip for increasing power modifying headers like the latest Hatori big mufflers.

I always do this but this time I decided to take some pictures to share this.

Any removal of flow restriction in a muffler system will have an effect in increasing the power available. If you remember the original cox engines and old control line engines had their throttle control via an adjustable exhaust opening. You probably get the idea of why that matters.

Not only you need to open the port but you also need to round the inner edges to smooth the flow. All smoothing helps lowering the resistance to flow and the better and less restricted the flow the more the power you can get.

Here are a few pictures of how to mod the headers to reduce the restriction:












Augusto.

[piromaniac]

Hey Thanks Augusto, I will have to give this a go.What do you use just a dremel
or a file?

[Augusto]

I use a dremel. A roughing bit first and then a finishing one for a smooth finish.

Augusto.

[H to the C]

Augusto,

Man you telling everyone our secret. This little mod works great.

hc

[Augusto]

Augusto,

Man you telling everyone our secret. This little mod works great.

hc

oops I forgot...
Come on Henry you scared they will learn to fly like you? hehehe

Augusto.

[EricLarson]

Augusto, did you guys check the results on a dyno? Just wondering as the header pipe combo you are working on looks to be mounted on an OS motor. If that is a SB17 or 18 that is not a muffler, but a tuned pipe. Both the SB17 and 18 are tuned pipes with muffler chambers similar to the MP2. The Hatori's out of the box where designed and tested on a dyno to see the results.

[tnreefguy]

Its the same concept as porting and polishing a set of heads on a motor. I never have thought of bringing that principle to a model engine. Looks good.

[EricLarson]

Keep in mind that 2 cycle and 4 cycle exhausts work different. Also mufflers and tuned pipes also work different. Augusto also mentioned that.

One of the guys I use to fly with when I lived in Thief River Falls, MN worked for Black Magic. They made lots of custom race parts for snowmobiles. Long story short, they also made race tuned exhaust systems, and some things work and others don't. The only real way to tell is on the dyno.

[tnreefguy]

True I would like to see some numbers for the ys 91 before and after the mod since I use that combo. I do like that floating head design. It sure is better than chasing a muffler bracket that will never stay tight.

[3DME]

The muffler pictures is one of the FH models. I have alot of experience with the big two strokes(250-500cc) as I race shifter karts.EXHAUST port & polish with two-stokes means two things. Porting is changing the height of the exhaust port in relation to the piston stroke, this is expressed in degrees of crank rotation. Porting will move the powerband around depending on how early or late the exhaust port is exposed(open). This works hand in hand with the shape of the expantion chamber in the pipe. Polishing is the smoothing of the port walls, first a roughing (called blending)then a polish to smooth. This helps the scavaging effect.

The interesting thing that I have found on the dyno is, porting will add a small amounts of hp to a specific rpm. It will also change when the motor "comes on the pipe" in relation to rpm. Smoothing and polishing the exhaust adds a good bit of torque over the whole rpm band of the motor. By the way I was the Florida Asphalt Series champion In the 500cc unlimited two years in a row.


I would have to say this mod falls under the blending/polishing since this mod does not change the exhaust timing. I am guessing here but I bet this mod adds torque over the whole powerband. A motor with more torque will not load as easy which is what we are looking for.

You want real power out of your 500cc 2-stroke?(CR 500 & KX500)
Cut the head way down 16.5:1. Re-shape and polish combustion chamber
Big ass jets for alcohol.
Here is the secret,
Fill the tank with cool power 30%
Uses 9 quarts of fuel in 25 green flag laps on 1/5 mile track
91 HP to the rear wheels, champ kart weight 295 lbs + driver
Just make sure you bring your balls with you, you will need them

Mike

[Rodney]

Hey Mike, sure hope you were a rep for Morgan fuels, thats an expensive way to win races.

[3DME]

Nope not rep. It was only about 6 gal per race (chump change) The big cost is tires. When I first started I was running alcohol and benol for oil(mixes with alcohol) I got the bright idea of running CP 30% for qualifing one day. Just happend to break the track record that day and never turned back afer that.

Mike

[Nick Defelici]

I think the guys at hatori know what there doing. Not to say that you dont

[Mike Fortin]

Has Augusto ever been wrong?

I started doing this about 8 months ago with my MPII's and there is a subtle yet noticable increase in power.

Thanks for sharing Augusto..as always!

[Augusto]

3DME is right on the money by identifying it correctly as a polishing mod. That's exactly what it does add torque across the whole power band.

Then again you can either do it or not it's up to you. I just shared it so next time someone asks me how come my heli has so much power I can refer them to this one as being one of the few things I do to them.

Augusto.

[3DME]

You can bet the guys at Hatori know what they are doing and they sure know more about these small engines than I do. As with most production parts there are some costs that will out weigh the benifits. HC says it works, but what does that rookie know?

Mike

[capebob]

Has Augusto ever been wrong

Well, I have a ruined cat's eye dosifier on a 40E carb, but I think that may have been my fault.

Bob

[Clintstone]

Good post guys, thanks for sharing as it gives everyone something else to think about. I think it is cool how the heli community shares instead of keeping secrets. I would like some feed back from some guys who have tried this.

[ChrisLaFollette]

Im going to mod my SB 17 when it gets here. Ive done it to my 50 sized muffler, havent bothered with my MP2 for the 90 but I am doing the SB17.

[Pete Niotis]

Smoothing and polishing the exhaust adds a good bit of torque over the whole rpm band of the motor.

This is exactly how it was explained to me a few years ago by a very experienced pilot that has been in rc over 30 years.

A bunch of heli pilots have doing this for a few years in the detroit area.

If anything...it can't hurt, just my opinion