Exhaust pipe qualities, particularly header pipe

Simon,

I had enough of exhaust rust with my time on Jap 2 smokes.

I bought a ti FP system (2nd hand) over the stainless variety.

Power, weight and quality were the reasons for my FP purchase, with importance in that order.

Stainless steel is ok in exhaust systems but mild steel or plated steel in my opinion is pony and therefore if only the power gain was there then the pipe would have to be quite cheap in comparison with a better ti or stainless system.

Are u thinking of something :wink:

Lloyd

I would only consider a system that is less noisy than stock and has a spark arrestor. You can't legally run a loud pipe if you ride on public lands in California. This does not apply to closed course racing however there are noise limits also.

California noise regulations

The only way I would consider purchasing an aftermarket pipe would be to replace a damaged factory component. The pipe would have to be as quiet or quieter than stock. It would have to incorporate a U.S. forest approved spark arrestor.The finnish would have to comparable or at least maintainable, it would have to look good if I cleaned it up. Price would be the next issue, everybody wants to save a buck. Last would be increased performance, that would be icing on the cake. When running properly I have never been at a loss for horse power or torque. Maybe 5% of the riders can use everything there Berg can give them effectively. Sound business sense say's to market to the other 95%. Let the others have the rest .
Just my thoughts on the matter, and as alway's.... I could be wrong :wink:

Ken

Closed course db issues

husabutt said:

This does not apply to closed course racing however there are noise limits also.

Click to expand...

Yes, more and more - it's not truly "racing", but the Dirt Rider 24 Hr Enduro Torture test (next weekend) requires a 96dbA pipe limit. Two west coast Supermoto series also have noise limits at certain venues. Quiet pipes are the way of the future. Both Akro and Leo Vince are producing good-performing, quiet pipes, and I expect other manufacturers to follow suit.

Regarding the original question - is it OK if pipes rust ? Not to me. There are many solutions available in the materials marketplace, the best of which (in my opinion) is thermal coating. In addition to preventing rust, the best coatings also disperse heat. And they are cheap. No rusty pipes here, thanks

Cheers,

Brett Saunders

I would like to buy a more quiet system than the stock unit, but only if the power loss was minimal. As far as rust, that's not acceptable. I would only buy a ceramic coated system such as BBR makes for the jap mini thumpers; a stepped header design. A header with ceramic coating keeps the heat in the exhaust which INCREASES performance. It is a freebie in the power game. Keeping the heat in doesn't cost anything. The ceramic coating that BBR uses looks really nice, doesn't rust, doesn't blue, and increases the power output.

Titanium systems produce less power than an identically designed steel system because the Titanium system transfers the heat from the gasses to the metal to the outside air more efficiently. Reducing the exhaust gas temp also reduces the exhaust gas velocity which reduces the power output of the engine. Racers buy Titanium systems for the weight savings and header design; not thermal efficiency.

Give me a chrome moly stepped header with ceramic coating.

Hi Simon,
From a fabricators point of view:

Regarding True Competition Equipment:
Mild steel as it is quite easy to modify and / or repair.
Next is stainless then Titaniun. Both burn to a pleasing tint providing engine tune is correct. I avoid thermal barrier coatings (intended to retain heat as opposed to dissipating it) in this area as such makes repair and / or modification difficult.

Regarding Aftermarket Competiton:
Thermal coated mild steel is cost effective and pleasing to the eye.
Stainless and Titanium are lightweight and good looking, albeit expensive.

Pleasure and / or Show:
Stainless or Chrome.


Note:
If you are interested in viewing some of my custom thermal coated systems please visit: www.XR100.com

Hope this helps.

Sincerely,
Dale

LINEAWEAVER said:

If you are interested in viewing some of my custom thermal coated systems please visit: www.XR100.com

Click to expand...

Sorry that I forgot to mention your designs in my post. I wasn't thinking about your systems because I consider them for flat track use only. Not well suited to the rocks on our single track.

XR100 has many Lineaweaver products that are race proven designs.

Hi Simon,
In the early days I relied upon Alumicoat (TM) which was an Aluminum based spray applied under pressure @ extreme temperatures.

I currently use a ceramic coating available in a multitude of colors.

Regarding mufflers and noise:
Since we often must run @ fairgrounds noise is a big issue regarding GNC dirttrack. Such is the reason for the big cannisters seen on the twins. Said cannisters are affectionately deemed boom boxes. Such a design does not hurt performance and indeed reduces the noise level. Unfortunately they are huge and such is the age old tradeoff being:

Small = poor power / quiet
Big = good power / loud

Sincerely,
Dale

While we are on the subject

I like to side with Berger 100%.

Dale,
Does a more open exaust produce less low end and more top end power?
Is there such a thing as back pressure with 4st's? Does back pressure increase low end power?
Thanks,
John

Re: While we are on the subject

jmumme said:

I like to side with Berger 100%.

Dale,
Does a more open exaust produce less low end and more top end power?
Is there such a thing as back pressure with 4st's? Does back pressure increase low end power?
Thanks,
John

Click to expand...

Such is a loaded question for which I will attempt to answer in a short and sweet reply.

Increased back pressure (ie exhaust restriction post valve) can slightly reduce over scavenging which is the result of an improper state of tune. (ie. incorrect camshaft selection, porting, etc. for the intended rpm range)

An engine properly tuned and operated in the intended rpm range will not benefit from a post valve restriction, however, an engine built for top end may indeed receive a slight boost in power below the torque curve.

More important regarding a closed exhaust (smaller outlet ID than that of the head pipe and / or muffler) is the effect it has regarding finite wave tuning. (Commonly referred to as acoustical tuning ala the two-stroke) Increased camshaft duration gives said waves a larger window for which to work both in favor and against power. Said effect is rpm dependant. When using a restricted exhaust (for noise) with a long duration camshaft (such as the LRX1) one will experience a considerable loss in low rpm power albeit quite a large boost on top. Both results are attributed to the finite wave reflections from the closed end piece.

I also believe that in addition to other reasons Husaberg and KTM to stick with their current short duration camshaft design in order to prevent low rpm power loss while keeping the exhaust somewhat quiet and small.

That is the best I can do without getting too heady and taking up a bunch more space.

Best Regards,
Dale

:lol: You don't seem heady..
I didn't realize just how loaded it was.
Thanks for taking the time to explain the basics Dale!
You're the man.. :bow: 8)

Dale,

Has anyone experimented with an internal megaphone design silencer?

i.e. An oval outside canister with the inner pipe being a megaphone design.

I wonder if a perforated megaphone could provide some sound silencing with the benefits provided by the megaphone shape.

Simon said:

Splat said:

Dale,

Has anyone experimented with an internal megaphone design silencer?

i.e. An oval outside canister with the inner pipe being a megaphone design.

I wonder if a perforated megaphone could provide some sound silencing with the benefits provided by the megaphone shape.

Click to expand...

Splat,

It is more effective to have the megaphone using a reverse meg, then installing a silencer afterwards.

Cheers,
Simon

Click to expand...

Gentlemen,
I tested both designs in the early nineties while developing the CG / Suzuki DR 350 for ISDE competition. A reverse cone of proper dimension fit to the the correct taper and length megaphone, attached to the proper length and ID head pipe, topped off with a suitable muffler (ie inlet and outlet proportional to or larger than that of the reverse cone exit) proved best overall.

Note:
Contrary to popular belief and all else remaining equal said reverse cone reduced power everywhere once camshaft duration and overlap exceeded a particular point.

The taper perforated core megaphone / reverse cone design muffler as described by Splat was quite popular in the seventies in particularly with regard to multi cylinder roadrace and dirttrack equipment.

Hope this helps.

Sincerely,
Dale

Hi Simon:

Without having to come up with entirely new technology for noise reduction one way to increase horsepower and reduce noise levels could be to utilize two muffler/silencers. This has already been done. At some point I will probably get a Looney Tuned Exhaust dual exhaust for my wifes YFZ450 quad. The magazine test results were favorable and it was quiet.