Expansion pipe on two stroke marine engine possble ?

[dart]

Hi there all,
i have a 40 hp mercury(jap spec) short shaft 3 cylinder,3 carb engine on a 3.90 mt alloy tinny.
i have done quite a few mods so far to it,jack plate,hydro foil plate,mercury ss 15 " 4 blade balanced,cupped,thinned prop,50 d2 carbs,50 hp d1 larger stinger exhaust,60 thou shaved of head,irriduam spark plugs,removed air box,disconnected rev limiter wire,lightened flywheel,carbon reeds,ram tube velocity stcks,removed 2 lighting coils,exhaust relief hole mods in leg,cut air vents in cowl,amsoil full synthetic @ 50:1 ratio,bp 98 octane fuel
future mods will be in next few months,
1 mm over size wiseco forged pistons,full race porting,balanced crank shaft.

ok,so is it possble to make/modify and fit a expansion pipe to a out board marine engine ?
i realize the expansion part of the pipe will not fit in lower leg,but i would use the smaller ,later model stinger manifold,add some pipe length to end of it,then run a cylicone adaptor pipe,cut off the old curved pipe/flange and position it so the pipe comes out of side of leg ,near where the lower 2 bushes are,then make bracket/brace to bolt the out chamber to the engine.
i have ben looking at using a jet ski 800 cc expansion pipe,the jet ski pipe shoulld work ok i beleive as the engine on jet ski are similar size,bore,stroke and rev range.
although they usually rev to 7,000 rpm.
here is what im looking at buying and modifying to suit/fit,
www.factorypipe.com
http://www.factorypipe.com/p_kawasaki.php
http://www.factorypipe.com/p_yamaha.php
http://www.factorypipe.com/p_seadoo.php

is this going to be possble some how ??
out of the pipes above,which would be the best one to choose ??
i like that kawaski 750 SX/SXi Limited
i really hope so,cause a nice decent expansion pipe would cain hard!!
i luv the sound of two stroke pipes!!
so do you reackon the perf from a expansion pipe would be be on par with say just the normal exhuast stinger or worse ?

out of the pipes from factory pipe website which one would have the most chance of working ?

you know how jet ski's have 2 or 3 cylinders,and they have only one expansion pipe for all cylinders,why is that and they work on them ?

i cant buy bigger engine ,say for example a 60 hp as they are far to heavy for my boat !!
as it is my boat is meant to have only a 25 hp size engine on it
.
but i have had my rear transom braced and modified for extra weight and power force.
i have tried doin extensive google search on this topic so far,nothing much.

do you please have any other links of info/pics of expansion pipeson small outboards ?
it is not possble to make seperate manifolds for my engine is it ?


why cant you keep bliping the throttle to keep revs up,say like shift gears??
jet ski's dont have gears either,and there power expansion pipes work dont they ??
they dont have a chamber for each exhaust port do they ??,no the ones iv seen any way!!
what is a sliding style pipe mean ?
so if the pipe does not act/perfom like it should do on a marine out board,if it was fitted,would it run worse then ?
what about the nice tinny rev sound a expansion pipe makes,will it have it ?
if i buy the centre bleed in the links above i provided,the pipe should kick in lower rev range than the end bleed pipe!!

hope to hear some replies/helpful comment or may be some links!!
cheers guys

[Mark75H]

Expansion chamber pipes have been used on racing outboards since about 1960, a couple years after they were first used on motorcycles. Using the search function on BRF should bring up a lot of answers to this.

A sliding pipe is like water injection, it makes power at more than 1 rpm, unlike a fixed length pipe.

Location of the bleed pipe is irrelevant.

[dart]

thanks for reply back
so would a jet ski pipe of similar size engine cc,bore and stroke work on a 40 hp 3 cylinder two stroke mercury outboard and perform or make it worse or just the same ?
thanks

[ultrafast30]

Outboarder on this site has done quite a bit with this. And i think Cheney has done the same. These guys may have some insight?

[dart]

Outboarder on this site has done quite a bit with this. And i think Cheney has done the same. These guys may have some insight?

hi mate,ok thanks for that info!!
i might give them a p.m then
cheers

[dart]

i just tried to p.m outboarder,his msg bank is full and cheney member cant be found!!

[Mark75H]

thanks for reply back
so would a jet ski pipe of similar size engine cc,bore and stroke work on a 40 hp 3 cylinder two stroke mercury outboard and perform or make it worse or just the same ?
thanks

Port timing and engine rpm are as or more important than matching bore & stroke. You need to google "The Two Stroke Tuner's Handbook" by Gordon Jennings and learn how exhaust tuning works

[Tim Kurcz]

thanks for reply back
so would a jet ski pipe of similar size engine cc,bore and stroke work on a 40 hp 3 cylinder two stroke mercury outboard and perform or make it worse or just the same ?
thanks

http://www.boatracingfacts.com/forums/showthread.php?7707-quot-Name-That-Outboard-quot/page28

Go here and know that the headpipe shown did not work well. It was replaced with a short stub collector and the pipe was shortened/rotated as well. In the end it worked great - after a summer's worth of trial and error. It gets a short tower this winter for racing summer 2013. Good luck with your project!

Tim

[dart]

http://www.boatracingfacts.com/forums/showthread.php?7707-quot-Name-That-Outboard-quot/page28

Go here and know that the headpipe shown did not work well. It was replaced with a short stub collector and the pipe was shortened/rotated as well. In the end it worked great - after a summer's worth of trial and error. It gets a short tower this winter for racing summer 2013. Good luck with your project!

Tim

hi tim,great thanks for the link mate!!
the pipe you are talking about above is the black one in post # 280 is it ???
i have a " westcoast" brand expansion pipe im modding at the moment to fit and try out!!
if you have any other info,facts or links r.e expansion pipes please let me know.
btw,that black pipe,what brand is it ??
whats it off ??
is it loud ??
what rev range does the pipe kick in at ?
should the end bleed stinger outlet on expansion pipes be similar diameter to the stock engine stinger that it comes with ??
would turning a end bleed pipe into a centre bleed give more low end power ?
cheers

glen

[Fastjeff57]

Question: How do those Formula One hydros run so damn fast without expansion chambers? All they have is a crude tuner built into the towerr.

Jeff

[Tim Kurcz]

Question: How do those Formula One hydros run so damn fast without expansion chambers? All they have is a crude tuner built into the towerr.

Jeff

Hey Jeff,

What appears to be a "crude" tuner is actually part of a folded expansion chamber that likely underwent thousands of hours of dyno time to develop. Remember that expansion chambers typically make power in a narrow powerband best suited to applications with VSD's or multi-speed transmissions. Outboard two-strokes require a much broader powerband that necessitates a totally different tuning approach. Never underestimate factory design features. Each and every single part was developed for a purpose. End users don't have a clue as to the time and $$$ invested to make those engines work.

Tim

[Mark75H]

3 into 1 pulse tuning ... almost as good as an expansion chamber

That's why there are so many triples and V-6's

[Tim Kurcz]

3 into 1 pulse tuning ... almost as good as an expansion chamber

That's why there are so many triples and V-6's

Agreed. Marine manufacturers use it for several reasons: Simple, light weight, wide power band, lowest cost. That's why my FE/850 engines use pulse tuning.

Tim

[hydroplay]

As a boat builder who is always looking for better handling and cornering, the FE boat we won a couple championships a couple years ago used a pulse tuning pipe which has all the attributes that Tim mentions but also makes the boat work better without heavy pipe(s) hanging off the back. This obviously has less impact on a bigger boat, but just replacing a steel bracket with an aluminum one on our CMH was detectable by the driver.

[Tim Kurcz]

As a boat builder who is always looking for better handling and cornering, the FE boat we won a couple championships a couple years ago used a pulse tuning pipe which has all the attributes that Tim mentions but also makes the boat work better without heavy pipe(s) hanging off the back. This obviously has less impact on a bigger boat, but just replacing a steel bracket with an aluminum one on our CMH was detectable by the driver.

Big time agreement with Sam - weight is a big issue for any boat. Given that your Tohatsu has pulse tuned exhaust already, you might consider running methanol and castor oil. You'll need only change carb jets, timing, and possibly a prop. Methanol has 20% more heat capacity than gasoline and something like 135 octane. This would be the simplest, lightest weight, and least cost way to increase power. You'll get more than a chamber for a whole lot less work.

Tim

[Mark75H]

3 into 1 exhaust tuning as mentioned on the other thread

[dart]

is it possble some how to convert/modify a conventional expansion pipe into a " sliding pipe " ???
thanks
glen

[Mark75H]

Its commonly done at the lead in pipe by having one section slightly larger than the other, creating a slip joint.

It has also been done by having a second cone inside the final cone.

Another way to vary the tuning is water injection. Some current production PWC use water injection in their pipes.

[Bill Van Steenwyk]

Glen:

Almost every subject you have asked about has been covered in great detail in previous posts here on Boat Racing Facts.

If you will look at the top of the page you will see a white bar with what looks like a magnifying glass just to the right of the white bar. That is the "search" function. If you type in to the white bar the subject you are looking for and then click on the magnifying glass, you will find MUCH information and will not have to ask for it. As an example "water injection in expansion pipes, or sliding expansion chambers". You will find much information plus pictures which should be very helpful.

Then after you go thru what many folks have contributed, many of them answers to the same questions you are asking presently, you can target to get more specific answers that the search function has brought to mind.

No one here on BRF is unhappy with answering your questions, but most of the answers are already there for the reading and understanding, by just using the search function and enter the keyword/words you are interested in. I think you will find you will get more information that way as most folks have already spent much time previously answering the same questions by others.

Good Luck

[dart]

i spoke to a mobile marine mechanic here in oz,and he has knows of some one that has fitted and modified a expansion pipe and he said that the ideal length from manifold to end of bleed of pipe should be approx 1,100 mm long.
well my modded fitted west coast marine pipe is about 900 mm long.
any way im taking the boat for a spin/testing on sunday,new redline race oil and redline synthetic gear box oil as well!!
cheers
glen

[Mark75H]

He is WRONG ... the length is different for each application

Read the Two Stroke Tuners Handbook and stop wasting your time and ours

[Aeroliner]

As Sam said it would be wise to read Jenning's before your start to ask questions. You can down load it here. http://www.vintagesleds.com/library/manuals/misc/Two-stroke%20Tuner's%20Handbook.pdf
Once you get the basics down then your questions will most likely be answered.

Alan

[Fastjeff57]

I designed and built over 150 expansion pipes using Jenning's formulas, and nearly all of them worked fine! It's a great info source.

Jeff

[Schiada]

Thanks Alan!
Now I have a backup copy.
My paper book is getting a little old,got it in 1974.

[Aeroliner]

I just looked on line for a copy of Jennings and got a rude shock. The $5.00 book now sells for $179.00 plus shipping. Electronic copy when printed two sided works very well.

Alan

[Fastjeff57]

It's worth that 180 bucks!

Jeff

[dart]

He is WRONG ... the length is different for each application

Read the Two Stroke Tuners Handbook and stop wasting your time and ours

yeah really!!!
ok i will stop frikn asking questions then smart @ss!!!!!!!!!!
btw if you dont like reading my chat/posts,then dont frikn read or repsond to it!!!!!
what is it a crime to keep asking questions on here is it???????????
i do searches,you wouldnt know if i have or have not!!!
if i want to ask/post questions about any boat/engine related stuff i will!!!!!
not going to be dictated on what to do just cause you dont like me!!!!
where does it say in the forum rules on here not to ask questions that may have already been talked about or answered????
if you dont like my topics,then dont read/respond to them as im not forcing you to read/reply to them am i,NO im not!!!

[Tim Kurcz]

yeah really!!!
ok i will stop frikn asking questions then smart @ss!!!!!!!!!!
btw if you dont like reading my chat/posts,then dont frikn read or repsond to it!!!!!

Hey Dart/Glen, Keep this up and you'll be banned from the site. I suggest you apologize immediately.

Tim

BTW: Sam is correct. Pipe lenth varies tremendously engine to engine.

[Schiada]

Ya, NOT COOL Dart!

[dart]

Hey Dart/Glen, Keep this up and you'll be banned from the site. I suggest you apologize immediately.

Tim

BTW: Sam is correct. Pipe lenth varies tremendously engine to engine.

no i wont apoligise as i have dont nothing wrong!!!
as they say,the truth hurts!!!!
if gives a toss if i get banned!!!
i have all the info i need now,including modding/fitting expansion pipe and i aint gonna show/tell any @ss the facts to mod,build and install it!!!
good bye

[Mark75H]

no i wont apoligise as i have dont nothing wrong!!!
as they say,the truth hurts!!!!
if gives a toss if i get banned!!!
i have all the info i need now,including modding/fitting expansion pipe and i aint gonna show/tell any @ss the facts to mod,build and install it!!!
good bye

yep, you are toast ... again. you won't sneak back in ... nor will you get on any of the other good boat forums. I'll warn them right after I get done on the admin page.