blw

My Feedback: (3)

rideblue- use the exhaust to pressurize your tank.

Birman

What happened to Bill Robison? He used to post all the time...

gjeffers

rideblue, check the timing, it just may be off.

rideblue

thank you all for the help .. how do I check the timing on it im also testing the LS and seems to be about 3and1/4 out makes it run the best but still has the same prob.

Hobbsy

My Feedback: (102)

That is a long way out, 1/2 to 1 turn out is more like it. If it has good compression then timing is not the problem. Mine is .008 from the end of the spraybar. Two Saito feeler guages worth as seen in the mic.

hamman

My Feedback: (61)

Glow plugs can have an effect on idle and midrange, if your using the one the engine was broke in with it was probably run real rich, toss it and put in an O.S. Four stroke plug and readjust carb mixtures. Larry

RC Specialties

Dave,

Have you had a chance to try the 14x8 APC yet? I am curious as to what RPM's you get. If you don't mind give me the idle speed also. It will give an idea if my LS is about right, aside from other variables.

Jim

w8ye

My Feedback: (16)

rideblue

That could be my problem I have not gone farther in than one turn of the LS so if that being the case I will Try it in the morning and let ya know the results also I will take your word for the timing ideas I know I can tare it apart to see the dot but im always a little conserned bout taking many bolts off the motor Thanks Guys. By the way May not matter at all but IM at almost 5000 ft elev always need more this HI

Hobbsy

My Feedback: (102)

Sorry Jim, yesterday was my wifes birthday so I dedicated most of the day to her, I'll balance the APCs this AM, I'm going to run the TurboHeader on my high compression Saito .80 and the .82, I no longer have a .72, nor a .91. I don't think it will fit the .62.

w8ye

My Feedback: (16)

rideblue

Although I don't think it is your problem, You only need to pull the valve covers off the engine to check the valve timing. If you are not good at finding top dead center, you will also have to pull the back plate.

Hobbsy

My Feedback: (102)

Jim, I had a fun time getting the APC 14x8 usable the hole was drilled crooked through it, Picture #1
The hole in the back of the prop was concentric with the cutouts in the back of the prop, Picture #2
My cure was to drill the hole just enough over size that the off set of the front wouldn't matter and ream the back for a TruTurn bushing Picture #3
Stock Muffler and APC 14x8 ==9,373 Pic. #4

TurboHeader and APC 14x8 9,511 Pic too dark, not readable.
Pic. #5 TurboHeader and APC 15x6==============9,428 rpm
Pic. #6 Stock muffler and APC 15x6=============9,225 rpm.
Pic. #7 is with silicon extension, if there was any loss at all it was less than 50 rpm.
I ran the engine at full song for 3 minutes with the extension on and it did not blow off or melt. 30 degrees ambien.

krop

My Feedback: (19)

Jim,
As i mentioned in prior E-mail, the muffler arrived but I am on vacation if Florida.
I will try it on my 82A when I return North and the weather cooperates.I plan to run with both the standard muffler and yours. Then, I'll post the RPM's and my thoughts.
krop

Hobbsy

My Feedback: (102)

K, I plan on running my .82 as well with an APC 14x6

Kmot

My Feedback: (24)

So, I am very curious. What is it about a stubby 90* fitting that gives a 200 rpm increase? [sm=eek.gif]

Hobbsy

My Feedback: (102)

There is a smooth chamber in there, nothing fancy, no sharp corners. It just works as you will find out. I used a new Fox Mircle plug today and the same WildCat 15%. Jim had asked about the idle, 1,910 was perfectly smooth, flying at 2,100 would be ideal.

Ken6PPC

I must be confused. The mic in the picture reads 0.016", not 0.008" as you wrote. What am I missing?

RC Specialties

Kmot,

I would love to give the secrets, but I can't. Hobbsy is correct in his statement but it goes beyond that. There are certain ratios that have to be considered and a balance achieved. If you could straighten the TurboHeader you could look straight through it. However, it does not sound like an open pipe. This was a complement of my son that studied acoustics in college. Did you know sound waves cancel each other sometimes???? Hobbsy put it best, "it works".

Thanks for you info Dave.

Jim
RC Specialties

Hobbsy

My Feedback: (102)

Sorry Ken, I went back to August and looked at the original picture, it is .016. Jim, have you tested one in warmer weather, I ran this one at peak rpm for 3 minutes with the gray extension, no cable tie, it didn't melt or blow off.

RC Specialties

Dave,

I have been testing the final prototype well over a year. The only change is the normal readjustment of the needle for the seasonal temp variation. I used the aerotrend coupling and found it held up better than others. I do recommend the tie wrap. I have lost a few in the air. It will get soft over time near the outlet. You will love the sound in the air, Dave. I may talking too much. Rules.

Jim

eclecticant

My Feedback: (10)

Thanks WSYE I have a coupls more questions the main one is what do i doto become a member.
Ihave a150 and a 180? in a 180 box but their is a missing plate on the side wheir the 180 would go is their any way i can tell for shore

THANKS KEN

Kmot

My Feedback: (24)

Jim,

No, I do not expect you to reveal your secrets. I expect Hobbsy to reveal them!

Kidding aside, I think it is a great achievement. And yes, I do know that sound waves at 180* cancel each other. But that is usually achieved with a device producing the opposite sound wave. If a pipe were designed in such a way as to generate sound waves at 180* to each other internally I could then understand making a 'quiet' pipe but not necessarily a pipe that achieves more rpm. However, an 'open' pipe on a four stroke Saito might indeed make more rpm than a muffled pipe. An open pipe that also manages to reduce noise, could be what we are talking about here. That is brilliant. Congratulations!

stallwart

This sound cancellation is called phase cancellation. It is achieved when identical sound waves are simultaneously produced with opposite or mirror image wave forms. I've seen it done electronically, such as with microphones wired in reverse of one another (out of phase) but not mechanically. I think the so called "hush" systems work on this principle.

If it is achieved mechanically that is terrific! No extra batteries required.

XJet

The usual method for reducing engine exhaust noise is a process called integration -- which simply means reducing the pressure difference between the highest and lowest variations in the exhaust gasses.

In its simplest form, this is an expansion chamber. In a more complex (and effective) muffler, it also involves the addition of baffles to try and "break up" the pressure waves that occur when the exhaust valve opens and the hot gases rush into the muffler.

Using phase cancellation on a small model engine is all but impossible (sorry to be a skeptic), because you're dealing with wavelengths of sound that are in the order of 8-12 feet. To get true phase cancellation would require that the cancelling wave travel half that distance before being mixed with the next pressure-wave. There's just no way you're going to do that in an exhaust fitting that small.

It is possible however, to use some aspects of gas-dynamics to create the same effect as a baffle through the creation of areas within the muffler where the gasses are choked due to converging pressure-waves -- however this is generally not as effective as the use of a physical baffle.

The reality is that with most model-sized 4-stroke engines running on methanol, you don't actually need much integration of the exhaust note to significantly reduce the noise level and some engines are even acceptably quiet when run on a stright pipe.

Don't get me wrong, I'm not knocking this device -- indeed I'd like to try one (and maybe review it for RCModelReviews.com) but it's most unlikely that there's a whole lot of black-magic going on inside it. However, it looks like a well-made, compact exhaust system that will carve a very definite and useful niche in the market.

w8ye

My Feedback: (16)

Ken,

William Robison is the man who does the memberships. He'll be along eventually and catch up with you.