N.Hammer stock pipe

[911Dispatch]

Can anyone recommend shortening the stock pipe, if so, how much? I’m looking for overall better performance, I’ve heard a lot say it’s just too long. I'd rather shorten the stock pipe than buy a mac or diff. pipe right now. Does it matter if you shorten the header or the pipe? All help and expertise is appreciated, thanks!

[abx131]

I just went thru this with my Miss Bud. I was told not to cut the pipe for they are tuned specifically for your engine and cutting it screws up the engineering of it. You are supposed to trim the end of the header where it connects to the pipe. Do it in 1/8 inch increments until you achieve the results you want. Each cut sacrifices low end and increases top end. See the entry titled Bud Exhaust Mods in this forum for the technical side of it by hydrojunkie, but that was the jist of it.

[911Dispatch]

Well..I'm glad I didn't start hacking away on the pipe, lol. I was hoping someone had already did this so I know how much to take off without trial and error. I've heard you just keep taking off sections until you stop getting results, maybe you can confirm that? by sacrificing low end, I assume you mean acceleration?

[Hydro Junkie]

No such luck. Setting a pipe is different on EVERY BOAT. You can have 3 hulls come out of the same mold and they will all be different. When you start adjusting pipes and headers, you have to consider how you are going to drive the boat, as well as hull type and loaded weight. If someone tells you he has great results with a pipe 4" long and it doesn't work for you, who would you be upset with, him or yourself? The boat's different, you could have a different engine, different fuel, different hardware, different carb settings, different prop................. The list of variables can go on forever. If you have a boat club in your area, you might take the boat to one of their events and have them help you set the boat up to YOUR SPECS, NOT SOMEONE ELSES.

[911Dispatch]

Hydro Junkie, I'm clear on that now. Could you please answer the second part of my question?

(I've heard you just keep taking off sections until you stop getting results. Is that how you know you reached optimal performance? By sacrificing low end, does "low end" refer to acceleration? I would like to have higher top speed and acceleration out of the corners. I've heard people say time and time again that, "that stock pipe is too long". Is it possible to increase both of these factors by shortening the header from stock length? How do you know when you've reached the "sweet spot". thanks, sorry for so many questions.

[Hydro Junkie]

First off, DON'T APOLIGIZE, that's part of what this site is for. Low end refers to low speed TORQUE. The more torque you have, the bigger prop you can handle. As for a high top end AND power out of the corners, don't hold your breath. I only know of one way to make it work, and it is a ROYAL PAIN IN THE BUTT. The only way I know of to get both is to have a radio controlled ajustable pipe, and yes, I have seen this done. There are two ways to do this:
1) Rig a slide mechanism in the exhaust coupling and attach a pushrod between the throttle servo or throttle arm to the pipe
2) Rig up the same as option 1, except run the pushrod to it's own servo.
As I said a royal pain in the butt. The drawbacks are:
1) The system almost never seals properly, letting exhaust into the boat and loosing backpressure
2) Routing the pushrod can get tricky, at best
3) Adjusting the pipe for any kind of performance at both ends is near impossible

Having gone through the hard one, now we get to the easy one. Pipe length adjustments need to start with a baseline. Start by doing ALL the other mods you want to do to the boat(I. E. ridepads, different props/rudders, engine hop ups, etc). Once you get them completed, you need to have some way to accurately check the speed of the boat. This can be a GPS receiver, radar gun, stopwatch, etc. Make several passes around a set course, recording the speed/time of each. Next, cut about 1/8 inch off the header followed by more passes. Also, you need to be paying attension to the engine tone, especially coming out of the corners. If the engine boggs down when you punch it, you have shortened the pipe too much to get it to accelerate quickly. It takes a lot of trial and error to get it right, though you will have to BALANCE TOP SPEED AND ACCELERATION. If you want a fast accelerating boat, plan on not as much top speed. If you want blinding speed, you better have a long straightaway to get there. Hitting the SWEET SPOT is a judgement call. Your sweet spot and mine will be totally different. When you start looking for that sweet spot, be sure you have at least one(better still is 2-3) extra header. One thing not mentioned yet is HOW MUCH POWER CAN THE HULL SAFELY HANDLE? It is possible to overpower the boat. Just like a Funny Car spinning the tires at midtrack, you can do the same with a boat.

[ejp]

so if I cut my header a little and added to the end of the pipe it would help.

[911Dispatch]

Thanks. I think I'll go with the easy one.

[Ron Olson]

The length that I start out at is 7", some go a little more, up to 8". I take this measurement from the glow plug following the header and pipe to the widest part of the pipe. You can use a long piece of coupler and cut this down also until you find the length. As far as I'm concerned, most tuned pipes on these boats are more of saying that they do have a tuned pipe on them and at the length that they are set at doesn't contribute to the motors performance. Boats like the NH have to be made to get around the radio box.
I founhd it surprising that most of the 4-wheeled R/Cers just slap a pipe onto their vehicles and don't work with the length, they assume that the factory has them set where they should be.

[ejp]

So, can I cut my pipe and it will help performance?

[Ron Olson]

That's what I'm saying ejp.
911, when it's on the pipe, it'll sound like sticking your foot into a 4-barrel carb-------waaaaaaaaAAAAAAAAAAAAA!
I had the pipe on my .12 'rigger a little short, 6-3/4" and the pipe would come on once it got over half throttle. Cool sound but it took a while to get it on the pipe and acted peaky. It does take some work to do it properly so cutting the pipe and/or header is the risky part. Use the coupler for shortening but have extra so that you can lengthen it if you need to. I've been to record trials and have seen the racers make small changes, usually 1/4" at a time.

[ejp]

The length that I start out at is 7", some go a little more, up to 8". I take this measurement from the glow plug following the header and pipe to the widest part of the pipe. You can use a long piece of coupler and cut this down also until you find the length. As far as I'm concerned, most tuned pipes on these boats are more of saying that they do have a tuned pipe on them and at the length that they are set at doesn't contribute to the motors performance. Boats like the NH have to be made to get around the radio box.
I founhd it surprising that most of the 4-wheeled R/Cers just slap a pipe onto their vehicles and don't work with the length, they assume that the factory has them set where they should be.


I don't really understand what you mean hear. What is the coupler your talking about for? Is the length surposed to be less then 7" long? Please explain is simpler terms.

[Ron Olson]

I'll try. The coupler is the silicone tubing between the header and pipe. I would use 7" as the minimum total length of the way that I said to use as a measurement as I found 6-3/4" to be too short. A heavier boat will need a longer pipe length, outrigger hydros run thier pipes shorter because for one thing, there is barely anything touching the water when they're at speed as opposed to monos, Cats and tunnel boats.
Keep in mind when setting up your pipe in a boat or car to keep a 1/4" gap between the header and pipe as any contact can give you radio interference.

[ejp]

I give up!!!! So do I leave the pipe out? Do I use the tubing as the pipe itself? I am a very visual person, Sorry. If you could explain in good detail I might understand what you mean. Sorry.

[Ron Olson]

No, the coupler is just what connects the pipe and header together. I was going to throw a picture in here but most of the better ones to show you what I'm talking about have been already posted elsewhere on this site. Give me some time to look around more in my pic files or else I'll go shoot some more. Once I can get you a shot, you will see how short I'm talking about.

[Ron Olson]

OK, ejp, 911 and Waterdog, I'm back armed with pix to help show you what I'm talking about.
First pic are 2 motors, one side exhaust and the other a rear exhaust. This shot will give you an idea of how short a 7" pipe length looks like to give you an idea of how much pipe and header has to be removed. Ejp, note the yellow and red silicone couplers.

[Ron Olson]

this picture shows how to measure the pipe length. This is a tool made by Grimracer, www.grimracer.com but is made for .21 engines like the Rossi shown, Nova Rossi's and others that have the front exhaust. A flexibla measuring tape does the same thing but I showed this because I only have 2 hands. There is a hole at "0" inches that you stick your glow plug tip into. There are measurements on it that show the inches for you to refer to.

OK, any more questions, I'll be on for a while and will try to answer them the best that I can.

[ejp]

so I go from the glow plug to the widest part and cut it down to 7"

[Ron Olson]

Yes, but it's easier to start a little longer, say, 8" then slowly work it in from there. If you start at 7" or less, you can also lengthen it from there using the pipe coupler. This is why you should get a fresh piece of pipe coupler from your Hobby Shop before trying to work on the adjusting. Most of the small block engines, .11-.18 use 1/2" I.D. couplers.

[ejp]

Mine measures about 8 1/4. So now I cut it down in small incraments. To get the best results from my pipe?

[Ron Olson]

Yes. It's hard to see in the second shot, but on my Rossi, the total length on that engine is at 8" which gives you an idea that 8-1/4" on a smaller engine is too long. We have to take in account in diameters and lengths of the pipes that we are using also. This stuff gets way over my head technical as I'm not a math genius. This is why I have to work with each pipe on each boat differently, even if I am using the same engine, header and tuned pipe. It's like props, you have to go according to what the boat likes, not hard and fast numbers. This is why there are so many different tuned pipes for these engines, what power band you need the power at, high, mid or low end or a combo like low to mid or mid to high range, load on the engine, etc. . When you find the sweet spot, you'll know it!

[ejp]

o.k. Thanks thats better.

[Watercadet]

There is a little room for disgresstion on the pipe legnth. On my FF.12 rigger it won't pull the normal props with the pipe under 8". I am at sea level and run on salt water. Oh yeah, the boat is packing a 1.62 HP Sirio Turbo motor, so the boat has plenty of power. Just gotta run a longer pipe.
Adam

[911Dispatch]

Ron,

In the one post you said to run the measure from the glow plug, down the header, to the fat part of the pipe. In the pic it looked like the measure went from the end of the pipe to the fat part, can you advise?

Also, if I mod the pipe to 7 inches, or even take more than 1/2 inch off the pipe from stock, as you well know the exaust end is not going to reach the hole it sets in at the back of the boat. What's the best way to fix that?

Thanks

[Hydro Junkie]

I'll coment on the exit end part. Use a piece of pipe a little larger to fill the area between the pipe and the transom. Now we get to the fun part. In one school of thought, you must use a larger size to keep from increasing back pressure(I've seen 1/4th inch differences), while in another the thought is to use one that's as close to matching inside diameter as possible. Again, use what works best for your boat

[Watercadet]

The tool Ron is using is clear. It is porpose built for that headder and is calibrated accordingly. It looks like a "J" hang the hole on the plug and the distance and radus of the headder is figured in. Hope that is as clear as mud ;)
Adam

[water dog]

I have a mip stinger pipe and was wondering if anyone has used it in a boat ?.How long is the macs pipe for the 2.5 engine size?.

[Ron Olson]

I've tried one and still have it. I did some experimenting with it but not a lot. I used to run one a looooong time ago on my Traxxas Nitro Hawk and loved the sound of it.

[911Dispatch]

Ok, got it.

Thanks