uitlaten topic

[tombo]

Denk dat je alleen niet veel merkt, aangezien je met ori cilinder rijdt.

[volvofan_volvo]

heej ik kan twee dingen doen nu :

-een homoet met een vaste bocht met verloop naar 28 mm
-zo'n uitlaat op maat laten maken met zo'n scooter demper

met homoet meschien 70 a 75 € 116.-
andere 75 a 80 € 200,-

gewoon met me orginele duitse blok
alleen wat moet ik nouw nemen??

owja ik kom aan deze gegevens via ron
van ronrolf dus wat zouden jullie doen ??

[Martijn Koert]

een opmaat laten maken bij s en s. zit je precies tussn in met de kosten koop gewoon een 4p. verlas je bocht en klaar. kost je 55 euro. een uitlaat van 200 eruo heeft helemaal geen zin op jou setup en de 80 haal je al helemaal niet

[volvofan_volvo]

maar dat is een nadeel van homoet heel veel mensen hebben ze en ze scheuren ook makelijk heb ik gehoordt

[Martijn Koert]

wat een onzin. bij de 6p wil die nog wel eens bij de bocht scheuren. maar een 4p scheurt niet hoor.

[tombo]

Waarom zou ej uberhaupt een opmaatuitlaat willen laten maken voor je originele setup :S steek dat geld dan in het bijwerken van je cilinder, dan ga je harder, én kan je je originele uitlaat gewoon houden. Naar mijn inziens is het weggegooid geld :S (niet lullig bedoelt ofzo, maar zo denk ik erover)

[Timmio]

nog een vraagje wat is een megafoon uitlaat? (staat op www.born2brom.nl)

[Ries]

dat staat er achter, die is uit 1 deel(van bocht tot en met demper), en een normale uitlaat is uit 2 delen...

[Kreidler4Life]

homoet scheuren niet zo gauw hoor/

heb pas 1x gehad dat een 6p scheurde nou die was al 3 jaar oud dan mag eht wel eens,

[Zatopek]

Ik heb iets vreemds. Mijn homoet 4p maakt minder toeren dan met een Jamarcol uitlaat....... Wel is ie ietsje sterker wat betreft trekkracht. het scheelt ruim 500 RPM is ca. 5 km op top. Verschillende sproeiers geprobeerd maar het maakt niets uit. Chris van Homoet begreep er ook niets van.......

[Martijn Koert]

dan monteer je de jamarcol

[Bolle Aad]

Ik heb iets vreemds. Mijn homoet 4p maakt minder toeren dan met een Jamarcol uitlaat....... Wel is ie ietsje sterker wat betreft trekkracht. het scheelt ruim 500 RPM is ca. 5 km op top. Verschillende sproeiers geprobeerd maar het maakt niets uit. Chris van Homoet begreep er ook niets van.......

Pijpje met gaatjes korter gemaakt misschien ??

[Zatopek]

Weet niet wat je precies met korter maken bedoelt maar de gaatjes in die blokfluit staan wel allemaal open....... heb ik ook al eens aan gedacht maar nog niets mee gedaan. Waarschijnlijk heb ik zo minder tegendruk en dus ook minder kracht. Wat denk jij? Die gaatjes wat dicht zetten? En hoeveel?

[Bolle Aad]

Frans/Dimage heeft ooit een Klaas Knol poortmap geplaatst
Welliswaar om een standaard cilinder op te voeren o.a .ook met behulp van een uitlaat van een 4,2 of 5,2 uitlaat

De bocht moest dan tussen de 20 en 28 cm lang zijn

het pijpje met gaatjes moest 40 mm afgezaagd worden

Als je zo`n pijpje reserve hebt, ken het niet zo,n kwaad om het te proberen

[Zatopek]

Nee, heb ik niet, voor de goede orde maar dat weet je natuurlijk via mijn topics en profiel, ik rij op een RS met een licht getunede Breitwand. Een Homoet 4p- geeft iets meer kracht maar dan mis ik weer 500 RPM en dus ca. 5 kilometer op top. Ik ga toch eerst eens die gaatjes in die blokfluit wat dichtzetten. Tevens ga ik misschien nog wat aan mijn cylinderkop laten doen zodat ik meer compressie heb. We shall see, hou je wel op de hoogte via dit topic.

[Luc]

Voor 'n betere werking kun je een 4P eenvoudig iets aangepassen, dit in tegenstelling tot een 6P. Hieronder de reactie van zo'n aanpassing op een 60cc Kreidler. Voor een 50cc zijn de wijzigingen minder groot.

Hello Luc
Today the Homoet 4P was modified "50%", so to speak. I have only welded in the 70mm belly and shortened the header to 220-240mm's (no exact measurement - I just wanted to try out the modification, being the over-eager young man that I am . A shorter header WILL be tested. This is fun! ;D
The difference is AMAZING! The power band is now from 7.500-10.000rpm, which is quite an improvement. Shifting from 1st to 2nd gear now no longer means a drop out of the power band!
I am still being surprised by the two-stroke engine and its sensitivity. To be honest, I just keep finding it more and more fascinating.
Thank you ever so much for your advice! If I was not looking forward to trying the other exhaust you made out for me, I certainly am now!
Sincerely, J

[Zatopek]

Luc, je hebt PB.

[kreidlerbas]

That modification is, in all its simplicity, very effective. Once paired with an expanding header and a 60-70mm belly, the Homoet 4P will be the best value-for-your-money pipe on the market, so far! But you need to put some work into it.

I also tried fitting a stinger with a diameter of only 13mm's, resulting in a bit more power and a small improvement of the power band.
Though it made my engine rev to 11.000rpm i 5th gear, I have removed the smaller stinger again, as I'm afraid the piston will over-heat.
The engine would start "knocking" after a while, but maybe it was due to a too lean mixture? I will do some more experimenting.

On another note, I made the edges of the header sharp where it connects to the 4P. Afterwards, the engine came on to power a bit smoother and the power seemed to improve a bit, as well.


Here's my experience:

The Homoet 4P is a quite good exhaust for a 6,25HP Mahle cylinder, although it should be mounted one hole further back on the bracket to show its true potential.
In its standard form it delivers too narrow a power band at higher rpm to be an amazing exhaust.

To put it in other words, the 4P is too short - it can be helped off a bit by using a longer header to match it better to the correct "tuned length". This cuts out peak power, but the engine will still rev to ~9.500rpm like it is intended for any 15.43.99 or equivalent! And the upper mid-range is improved drastiacally!

Alternatively, you can weld in the 60-70mm belly-section to match it to the better tuned lenght.
Basically, this lets you use a shorter header, which then lets the engine rev higher, thus making more power.


Conclusion:

The 4P simply needs the mid-range power a longer header delivers - either that, or the exhaust should be modified as mentioned. Anything else will most likely result in a power band which is too narrow.

Quite a bit of text, I know. But this info IS "da bomb", so to speak. And I'm not finished, yet.

One thing is for sure: The Homoet pipes make great power when utilized correctly. On the other hand, they are mass-produced pipes and you only get what you pay for.
Believe me, guys - a pipe matched truly to your engine setup will deliver even more power. Consider that before investing in a Homoet and cut it into pieces - one of Luc's designs would be SO much better.


Sincerely,

Jesper.

P.S. Oh yeah. After the modification of the 4P, I can now utilize a sprocket ratio of 13/35 as opposed to only 12/35 before. Same engine speed, better acceleration. That's worth thinking about, isn't it?

[kreidlerbas]

nog een vraagje wat is een megafoon uitlaat? (staat op www.born2brom.nl)

A megaphone exhaust is the diffusor-part, alone - "half an exhaust", so to speak.

It helps empty the cylinder with its expansion.

A standard exhaust with a correctly placed reflection wall will give more power, depending on the length and "angle" of the diffusor taper (the expanding part after the header/down pipe).

[Zatopek]

@ Kreidlerbas : Very interesting story. My Homoet 4p will be changed by Luc in August. It will be changed specially balancing the timings this particular cylinder. Hopefully it helps a lot, for the moment my 60cc Parma will not rise above the 9.500 RPM in fifth gear.

[kreidlerbas]

@ Kreidlerbas : Very interesting story. My Homoet 4p will be changed by Luc in August. It will be changed specially balancing the timings this particular cylinder. Hopefully it helps a lot, for the moment my 60cc Parma will not rise above the 9.500 RPM in fifth gear.

Mine tops out at 10.000rpm on a good day - typically it stops around 9.700rpm. The 11.000rpm is reachable when I put my nose on the gas tank, I have to admit. I should've written that earlier

I have also tried the exhaust on a 15.43.99 (40ZN8+) with a longer header - the engine went totally nuts from 6-9.000rpm. A shorter header would make that setup fly.

A lower tapered (angle) baffle and a shorter belly should increase the power band, although at the expence of peak power. The question is how much of a sacrifice that really is. I'm definetely looking forward to hearing more about that mod, if Luc will let you post it.


And here's a thought:

The Homoet 4P seems to work best with a low exhaust timing. Inserting a belly allows it to be used on a cylinder with a longer exhaust duration, as this mod delays the reflection timing of the preassure wave = it returns after the transfer ports are closed.

[Andy]

Do you have some pics of your modificated 4p.

Andy,

[kreidlerbas]

Do you have some pics of your modificated 4p.

Andy,

No, I'm afraid I don't. I'm waiting till I get some heat resistant paint and a steel brush - it doesn't look too good at the moment. Besides, my Kreidler needs a big clean-up. Too much tuning, not enough polishing.

There isn't much to see, though - it looks a bit like the 6P with the small silencer apart from the missing expansion header, of course.

I'm thinking about modifying it a bit, again. I have plans of making an interchangable belly section - that way, I will be able to determine the optimal belly length for a given header length.

If any of you guys wish to try out the mod with a rough method of calculating the tuned length, read the following guide:

1: Calculate the tuned length.
Exhaust timing * 42454 / rpm*

2: Measure out the total length of the exhaust, from the piston up to the main reflection point of the baffle.
Header + diffusor + (baffle/2)

3: Substract the exhaust's length from the tuned length.
Tuned length - header + diffusor + (baffle/2)


*The intention of this formula is to reveal at which rpm the engine delivers maximum effect - I have found that it shows maximum rpm, instead. Maximum power will be delivered ~1.500rpm earlier with the Homoet 4P after the mod.


Here is an example:

1:
Exhaust timing: 190º

Tuned length = 190º * 42454 / 11.000rpm = 733mm

2:
50mm + 220mm + 317mm + (193mm/2) = 683,5mm
(50mm: piston to header. 220mm: header to diffusor. 317mm: diffusor to baffle. 193mm/2: main reflection point/half the baffle cone)

3:
The belly length is therefore = 733mm - 683,5mm = 49,5mm.

I must add that the baffle cone has NOT been measured very exactly. It may be 190mm or it may be 200mm. It is a close estimate, and yes, I forgot to measure it correctly when I had split the exhaust in two!


The belly of my 4P is 20mm's longer, but it is also intended for a shorter expansion header at a later point. The end result should be 13.000rpm max and the power will peak around 11.000rpm. I won't punish my engine with that high RPM untill I get a new piston.

Some of you may have seen the above calculations before. I have with no care for copyrights lifted it from Graham Bell's book on two-stroke performance tuning. The numbers are guidelines and are therefore NOT 100% exact - keep that in mind if you ever read the book. (Great reading, none-the-less. But have a dictionary handy if you're less than great at English.)

[Zatopek]

Hi Kreidilerbas, very interesting story again. The way to calculate the pipe is it the same way Luc is doing so After changing the pipe wilt it make more RPM also in fifth gear or is it "only" more power earlier in powerband

[kreidlerbas]

Hi Kreidilerbas, very interesting story again. The way to calculate the pipe is it the same way Luc is doing so After changing the pipe wilt it make more RPM also in fifth gear or is it "only" more power earlier in powerband

I think Luc uses some other references, to be honest. As mentioned, these calculations are not 100% exact, but they are fine for a generel guide for most two-strokes.
Luc uses reference points from exhausts made for Kreidler racing engines, all the way back to 1964. Having these numbers gives a great advantage, and even if I calculate an exhaust from Graham Bell's guidelines, you can be certain that it will not work as good as one of Luc's designs!
Theory is great, but nothing beats practical experience!

In other words, if you were considering having Luc build you an exhaust, GO for it. It will work! And it will be worth every cent you pay for it, as well.


But, here's a bit more theory for those who like that stuff (I do):

Max. RPM is decided by the total expansion chamber design, but it is primarily a matter of the tuned length, the height of the exhaust port and the length of the header.

Graham Bell has set up the following theory which is a good guideline:

"My theory is that an engine requires a certain exhaust duration to attain a specific engine speed. Therefore, if an engine is required to make maximum HP at, say, 12.000rpm, the exhaust duration required will be the same (+/- 1º) regardless whether the engine is an 80cc cross engine or a twin cylinder 250cc road racer."
- A. Graham Bell.

I.e. for max HP at 10.000rpm, the exhaust timing should be 190º-192º;
for 11.000rpm it should be 196º-198º;
for 12.000rpm it should be 202º-204º;
and for 13.000rpm it should be 205º-207º.

An important thing to be aware of is that there should be a certain difference in port height from the transfer ports to the exhaust port!
If the difference is too high, the power band might become very narrow.
I believe that the difference in port height should be minimum 8mm's and maximum 9,5mm's, i.e. if the transfer ports are 31mm's from TDC, the exhaust port should be no higher than 21,5mm's on a Kreidler.
That is, unless you have the right exhaust! Then the duration of the exhaust port is less important, although it still makes a small difference! A lower exhaust port will always benefit low-end and mid-range power.


If anyone has access to building an exhaust with out spending money, I will gladly try to design an exhaust, for no other reason than plain, old fun. Keep in mind that I can give no guarantee of how it works - that's why I don't want money to get involved.
All I need is the exhaust height or timing + the RPM it is supposed to work at.

Please remember that all of this is theory based on another person's experiences with other machines than 50cc Kreidler engines. If I design an exhaust on the basis of Graham Bell's knowledge, it may or may not work. But it would be great fun to try out.