ESE's works engine tuner

[F5 Dave]

Husi seems to love saying what I love??? Mostly its all news to me.

My impression is that Boost bottles are generally a bandaid for a poorly designed pipe. I built a variable volume one for my old H when I poorly designed a pipe with too much baffle angle & I couldn't be arsed fixing it. It smoothed out the dip before peak power & was fun to play with for a laugh & easier to change than the pipe which was a long twist up around swing arm type.

[husaberg]

Husi seems to love saying what I love??? Mostly its all news to me.

Relax Dave Husey enjoys quoting you, only because you are always so quotable.
This is what you actually said in full. Apologies if you do indeed have no opinion on them. My jibe was in jest. Sarcasm is indeed wasted on the goof.

http://http://www.sip-scootershop.com/EN/Products/11701000/Boost+bottle+POLINI.aspx

Pah! What a load of bollocks (no offense I mean the bolt on goodies merchants website). I love these descriptions of what is supposed to be happening & how it will cure the common cold etc.

Yamaha made these famous in the 80s on their MX bikes. But there is a reason you don't see them on modern high performance bikes. (well infact the RG150 has one, but in the form of a long rubber tube). They are really only useful as a plaster for a badly designed (or rather mismatched) pipe. TSR software will tell you how to design one for the area you are trying to affect.

I have tested "boost bottles" between the carb and the reed.
They improve throttle response very low down in the revs off the pipe.
A couple of older quads used the idea, and one will hardly run at all off the bottom end if the bottle is removed.
But compared to a ATAC on the header they are virtually useless for improving power at the bottom of the useable band.
Whereas the wave/pressure action in the pipe is so much stronger that a flapper valve controlled chamber on the BSL500 gave 28% more power at around 7000 - was closed by 8000 and had virtually no effect at that rpm and up.

Have anyone ever seen one used on a rotary valve?
I can't recall ever seeing one ever mentioned on a rotary valve? (There way be an obvious reason for this I am overlooking)(Tell you the truth I have never got my head around the reeds on the KR250 either)
I thought it might work and if it had a diaphragm the volume could be easily adjusted for trials on the dyno IE by either putting a vacuum or pressure on it to adjust volume.
I guess it might pulse a bit too with the pressure in the intake too? I dont know if that would be good or not.
Obviously the diaphragm would have to be mounted towards the middle a bit of the "Boost bottle".
It could solve the over metering and fuel drop out puddling of a plenum mounted before the carb intake?

[dmcca]

First of all... this is my first post here... been lurking for a while, particularly in this thread, and ive gotta say its one of the best 2T reads around, well done everyone involved!

I have tested "boost bottles" between the carb and the reed.
They improve throttle response very low down in the revs off the pipe.
A couple of older quads used the idea, and one will hardly run at all off the bottom end if the bottle is removed.
But compared to a ATAC on the header they are virtually useless for improving power at the bottom of the useable band.
Whereas the wave/pressure action in the pipe is so much stronger that a flapper valve controlled chamber on the BSL500 gave 28% more power at around 7000 - was closed by 8000 and had virtually no effect at that rpm and up.

I'm interested in testing some ATAC style chambers... are there any rules of thumb to follow for the volume or positioning of the chamber? Thinking of adding one to a single cylinder 250 using the powervalve actuator to open a chamber. However the only way of doing it is to have a branch pipe about 150-200mm down the header that then leads to the chamber... how critical is the distance between the exh port and chamber entry?

[Grumph]

Some years back John Robinson of Performance Bike Mag did a test on an add on atac type chamber - Malossi brand i think.
Manufacturers recommendation was fit as close to the port as possible. Robinson agreed - didn't test at different placings, Fitted it at around 100mm out from the joint at the port. Results reasonable - fattened the curve a little at the bottom if I remember right.

[wobbly]

I posted about this a while ago.The chamber needs to be about the swept vol of the cylinder.
When its big enough, going bigger does nothing.
The connecting tube should be about 1/2 the header dia, as short as possible, with the controlling throttle plate as close to the pipe as you can get it, and as close to the flange as you can get it.
The resonant effect works up to a specific rpm, then kills power real quick, so you need an rpm "switch" to control a solenoid that quickly snaps the plate open at a set point,unlike a powervalve that can be ramped.
Many current cylinders have an ATAC volume within the casting that is opened/closed at the same time as the powervalve.
This is easy but for sure not the best setup.

[dmcca]

Thanks guys, appreciate the info. Im already running an ignitech ignition so could easily set up a solenoid off that. Will keep working on a reasonable design.

I posted about this a while ago.

Sorry, must have missed that.

[F5 Dave]

. . . .
The connecting tube should be about 1/2 the header dia, . . . .

whoa, that's interesting. that's quite a big hole & larger that many designs I have seen on production stuff. Hmm, maybe time to look at my GG300's setup.

. . . nah its got enough mumbo

[TZ350]

I bet the Aprilia is a much larger diameter disk valve.
So it is open wider for greater percentage of the time/area than comparable timing would have a smaller disk.If that makes sense.

Looking at your picture Husa, the Aprillia sure is shorter, it must have the primary drive on the other side.


I am not sure what can be done to modify the cover and shorten the inlet tract down to look like the Aprillias, but I will have a look.

I understand how a taller port of the same timing and area is fully open for longer than an equivalent lower one.

But even after machining all the teeth off the starter gear on the back of the clutch hub the size of the rotary valve itself is still restricted by the inner sleeve protruding out of the clutch and that rides on the input shaft. Still I can get another useful 10mm overall and had already started making the parts required and will use them in the next engine.

[husaberg]

Looking at your picture Husa, the Aprillia sure is shorter, it must have the primary drive on the other side.

I am not sure what can be done to modify the cover and shorten the inlet tract down to look like the Aprillias, but I will have a look.

another useful 10mm overall and had already started making the parts required and will use them in the next engine.

Yeah it is a hard ask. The Rotax Aprilia is back to front compared to most Japanese engines. Its a Euro thing. I must admit to wishing my Berg was a right side kick occasionally

[dmcca]

Hmm, maybe time to look at my GG300's setup.

Funny you should mention the GG300... I was working on one the other week and thats what gave me the idea of adding a 'torque chamber' to my bike... the GG300 setup has a very small port thats linked the power valve assembly on one of the aux exhaust ports... its hard to see the exact size of the port but its very small, like 10-15mm tops. It sure has loads of bottom end though.

[Henk]

It sure has loads of bottom end though.

That would probably have more to do with the fact that it's a 300 than the extra port, my 360SX had so much bottom and mid I never bothered revving it out.

[wobbly]

The cylinders that use the powervalve action to open and close a port linking to a chamber within the casting are very limited by physical room.
We tested a couple of sizes of connecting tube and plate valve, and found that if it was smaller than 1/2 the header dia it didnt work near as well.Bigger than that and the flow disruption lost top end power.
We had a 20mm tube on a 43mm header for the 166cc cylinder size, with a 150cc chamber, and as I said this gave around 28% more power just below where the valve closed.

[husaberg]

Worth a look

http://www.emot.nl/webwinkel/index.p...atId=saleItems

http://www.emot.nl/specials.php

http://www.emot-oldparts.nl/webshop/

http://www.emot.nl/fotoalbum/

Below engine of the Day any guesses? Answers on the back of a Blank Cheque to Husaberg.
Second pic is the split single "Twingle" piston supercharged DKW (3 pistons Single cylinder) well one spark plug. I was looking for a Pic of this a while back for Snow
3rd pic Rumi 125 http://2stroker.createforumhosting.c...iel-t2652.html
4th pic Is that a pneumatic powervalve on the Casal 80? I have no Idea
5th Rumi

[wobbly]

The pic of the Casal is a Rotax copy style pneumatic powervalve - basically bloody useless as the instant you feather the throttle at any rpm the valve drops.
The pic of the Bartol I have seen before named as something else?? - but was the inspiration for me to use the FCR downdraft carb on the TSS500, same as
what is going on the F3 Superlight bikes I am building - Aprilia RS250 with 100+ Hp RZ400.

[F5 Dave]

Clear thinking when you lose any pretense of needing to be a road based engine. imagine the grief with plug fouling from the down angled cylinder on a few year old bike with a leaking tap as you tried to kick start it outside your girlfriends house with the rain just starting.