3 into 1 pipe

[diablo]

ordering a 3 into 1 frm jemco tomorrow, can't wait. what would be good jetting at sea level for that pipe on 73 carbs

[tz375]

Good. Please post plenty of pictures.

The most likely jetting is a couple of sizes up on the main jet but it's possible that it will not need any jetting changes.

Best way to set it up is on a dyno with exhaust gas analysis, but if that's not an easy option logistically, start with two sizes up on the mains and work from there.

[jabcb]

Am looking forward to seeing your pics.

Which tripple? Going to have Jemco nickel plate or power/ceramic coat the pipes?

[tz375]

On the bench today is a really nice Comer P51 kart motor. The owner brought it over yesterday and we chatted for a while. Nice guy. The objective is to see if we can design a better pipe than is commercially available (Tall order I know).

Last night, I went through his measurements and started to put them into the software and today I decided to check everything he measured just to be sure and you know how hard it is to accurately determine actually exact port opening/closing times. His data was pretty good.

So I start to look at the pipes he brought over. Typical short fat dumpy Kart pipes where a large diameter muffler sleeve makes it hard to work out what size anything really is at the stinger end.

Then I decided to do some on line research and come to find out that Karts are not only strictly controlled, but they are all tweaking jetting to change pipe temps to change the powerband. They also play with replaceable header lengths which they call the flex pipe. It's not so much about changing the basic power curve as it is about tweaking the tuned length to match the pipe temps. So on a cold day or on a track where the pipe is not as hot, the header (flex pipe) will be different to say a day with lower air density.

We change jetting based on atmospheric conditions - they change the pipe.

Next step is to try to measure the pipes and come up with a mathematical simulation of those two pipes and from there see if we can change pipe design for the better. Ports are already close to max in the spec chart, so there's not a lot can be done there. It all comes down to the pipe and that's supposedly controlled as well.

All very interesting.

[diablo]

yes very interesting, i am going to have to figure out how to get some pics on here. This k i am working on will be nice when i am done, the PO has an awsome flame paint job on it. Has only 12 K miles on it and is like working on a new bike.
I want to put K&N's on it so i may have to get bigger jetting or raise needles, cheers.

[tz375]

"posting" pictures actually means pointing to the picture on another site. People typically use Photobucket or something similar and then write this code into the post

"[img]http://www.yoursite.com/yourpicture.jpg[/img]"


The "img" tags tell the system to go an grab that image and insert it here.

We'd all like to see your bike and that new pipe.

[Oldracedad]

Richard

I started building pipes for the Vintage kart club a year and a half ago. I'm building them now in the new shop. The basic design of them hasn't changed in over 35 yrs. The pipes I'm building don't even wave out that well on the TSR software. I talked to Tom a while back as he wanted to put the software design into his program but noone would them him the concept. He thought the karting people were a very tight knit group at that time...(20 yrs ago)....When my son raced karts (KT-100 yamaha) we tried a pipe called a "Vevey"...it was a pipe out of europe. That pipe was amazing to use on a fixed kart gearing motor....powerband everywhere....They were designed to run on low pipe temps as there thinking having powerband forever depending on how much straight flex you put between the header and the 1st cone. I've seen these pipes used on Formula A motors (100cc rotary) and they would turn them motors 21K.....what a sound...The case reed motor are the new thing and they only turn them 17K...and they pull strong starting at 6K. I'm porting a KT-100 now to run on alcohol. I'm altering the exhaust width leaving the height alone as gear pulling kart motors only use 170 to 180 degrees of exh duration. I'm useing this formula that came out of Italy that calculates blowdown in referance to stroke. I guess this formula is spot on. It's also backed up with some of my old kart buddies I'm still in touch with. I'm just finishing up the 2nd cylinder and they are going to test both cylinders I've done here in about a month....He hopes

Just my thoughts
Bill

[tz375]

Hey Bill, great to hear from you.
You still out east or did you come back to the third coast?

I hear you about the rather odd looking numbers. The pipes are a regular chamber but they have a tube over the stinger and then another larger tube over that to make the gas and noise go the long way round. And then it exits through a bean hole slot that is a spec size too.

This particular kart runs in one of the direct drive spec classes where almost everything is spec'd out from port widths to carbs spacer thickness and there is not a lot of wriggle room. I did think about blue printing it but there's so little room to move, it's easy to come unstuck. Besides, these guys really just want to know what's possible.

I ran the first couple of sims and am getting closer to actual dyno results which is a good place to start. What I'm seeing is a peak torque and HP at around 10K which is where they are clutched and then they run it in the over rev portion of the powerband from peak up to around 14,000 where it drops off fast.

The idea seems to be get max torque as the clutch bites for great drive out of corners and then live in the very top where revs make up for the dropping torque curve. We would just gear it differently and use the front of the curve but with no gearbox, that isn't an option for them.

This motor came with a badly stuck piston. It appeared to be smeared on front and back faces and under that mess was a classic 4 corners cold seizure. Looks like the driver got on it while the barrel was cold and that caused the cold seize and he kept going and that raised temps to smear a whole lot of piston on the sleeve. Muriatic acid and Q tip cleaned up the aluminum on the bore in short order but there are some gouges in the bore that won't come out with acid. They could go up almost 1/2mm on the bore before they break out of spec.

I'd love to grind in some trick cheater ports that fit the gauges but provide more area but that isn't happening. As I said, my job is to work up a pipe or to have fun learning something new.

[stcyr]

tz, have you tried or considered hydroforming: http://www.3wheelerworld.com/showthread ... on-chamber" onclick="window.open(this.href);return false; ?
Looks relatively easy and the results are beautiful.

[tz375]

Thanks for the link. I actually downloaded that thread a couple of years ago. Hydroforming has some advantages form a fabrication perspective, but somehow they don't look as "real".

[Suzukidave]

I know we arnt dealing with the knife edge of performance here but i do have a wonder if the exhaust waves respond as well to the sectioned more angled chambers or the smooth shapes of the hydro formed pipes ?

[ja-moo]

I know we arnt dealing with the knife edge of performance here but i do have a wonder if the exhaust waves respond as well to the sectioned more angled chambers or the smooth shapes of the hydro formed pipes ?

That's like asking which oil is best........ many answers.....

[tz375]

There's at least one guy out there creating a curved expansion chamber - by that I mean that the changes in section (angle) are all curves with no sharp changes and he's convinced he's about to conquer the world. His competitors who still beat him, think that may not happen in this lifetime.

We do know that flow tends to separate from the walls if a change is too large, so the logical extension of that statement is that curves in place of sharp changes should improve flow. Unfortunately for that school of thought, 4 stroke guys discovered years ago that a series of angles in a valve seat actually flow better than a fully radiused seat. IIRC a 15 degree change in angle will flow very well, but much more and it will separate. Fully curved valve seats flow worse that a standard race type 3 or 5 angle seat.

For some reason, gas and pressure waves don't always do what we mere mortals think is logical, but algorithms used in simulation software typically work on a step change approach to the iteration and as such appear to not be capable to discerning such a subtle shift in design.

We could conduct flow experiments to see those effects and could potentially construct a series of different pipes using smooth and sharp changes to compare in back to back tests. With a large enough sample size, it might be possible to determine the effects of each....


Or as wisdom of sage Ja-moo suggested: Many people. Many Answers

[stcyr]

It's similar to adding a turbulator to an airfoil. http://en.wikipedia.org/wiki/Turbulator" onclick="window.open(this.href);return false;

In an expansion chamber, the combination of velocity and change in direction of the gases isn't nearly as great as in a 4 stroke's head so the boundry layer has no problem following the inner surfaces. Of course, the largest diameter sections have such a reduced velocity that it's a non-issue. The contour into the outlet pipe seems like the most critical for flow.

In theory, a chamber built with smooth (wave) transitions would equate to a slightly less abrupt transition into the power band and one built from cone segments could be more finely tuned to produce a stronger, more defined power band.

[ja-moo]

Not coming from a technical view, I sometimes just look at what the factories do on their race bikes. As they are the ones (with th $$$$) looking for every 1/10 of a hp or better spread of power. If one design showed a marked improvment, I would "think" that design would be a consistant on racing bikes. It doesn't seem to be, so I would take an "educated guess" that one design doesn't have a marked advantage over another.