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Thread: ESE's works engine tuner

  1. #32536
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    19th October 2014 - 17:49
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    Ken and Frits, thanks for making that material available, I'm looking forward to viewing it.


    Does a typical modern 64-68mm 250 MX piston usually have enough material around the wrist pin to allow boring to take a 20mm pin instead of the common 18mm pin? I'd think that the strength concerns are at TDC when the pin is trying to pull down and out of the piston; BDC would have the pin forced into the body of the piston.

    I suspect they may start out with a fairly generic casting/forging, but I don't know if they get trimmed on the underside of the piston below the pin (to save weight) enough to not leave sufficient material. Would it be a good plan to offset the new bore upwards so it just cleans up the bottom of the original bore and so removes minimal metal below the pin?

    Any thoughts as to what is a good number for a safe minimum thickness below the pin for high RPM use?

    thanks,
    Michael

  2. #32537
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    12th October 2016 - 01:24
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    Question about tuning for longer engine life:

    I'm building a Lambretta engine for endurance road use and bucking the trend of trying to get as much displacement/power as possible. I need to be able to do 300 mile days for several days in a row. I know I'll have to give up power but I'm also thinking that the power itself is not the cause but the effect. I'll be sleeving an aftermarket cylinder back down to a stock 175cc but the sleeve also gives me the ability to set the port area, timings, and angles as desired.

    Questions:
    With power being a combination of BMEP and RPM, do I have to give up both?

    What has the largest impact on engine life?
    1. Engine speed
    2. torque/power
    3. temperature
    4. other

    Given it's a forced air cooled engine, are there BMEP limits I should not expect to be able to exceed in sustained operation?

    Current modeling in EngMod has me at 25hp @8000rpm and trying to decide if I should just be happy with that or try for more.

  3. #32538
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    7th October 2015 - 07:49
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    Ken and Frits, thanks for so helpful gallery. Bridgestone crank looks so nice.....
    .
    Add some tables from very old V.V. Bekman s "Road Racing Motorcycles" book and very old Fiat marine turbo-reed engine with trans higher than ex.
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  4. #32539
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    17th September 2013 - 01:07
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    Frits or anyone with interest,

    Going through your (Ken)-pictures I found the suggested pipe for the Trabant.
    One can see that you have opted for a straight header section.

    Click image for larger version. 

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    This is in line with my own thoughts trying to not over scavenging my old (50cc moped designed in the 50-60:s) engine that, minus the RV intake, got way more similarities with the Trabi than the RSA...or anything with a descent 3-5 port layout.

    As a general rule of thumb, should you suggest to start with a straight header and go from there with antic designs like this?

    A friend with the same type of engine have tried all types of pipes, the last one a modern thing from a scooter. Way to extreme I say and I think he confirmed it with “more revs...but terrible dip, with fuel reversing out the carb, just before a final rush of power”.

    He is at 190/131 duration so my take is that the “already to good pipe” even worsen the negative 2/3 of max hp-rpm dip and is even more pronounced by having optimal timings?

    Will have a go in EngMod to see if the pressure traces can tell anything and if I’m able to hack a suggestion for a new (simple and basic) pipe together...one that works better that is.
    But any input is appreciated.

  5. #32540
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    25th March 2004 - 17:22
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    Quote Originally Posted by OopsClunkThud View Post
    Question about tuning for longer engine life:

    I'm building a Lambretta engine for endurance road use and bucking the trend of trying to get as much displacement/power as possible. I need to be able to do 300 mile days for several days in a row. I know I'll have to give up power but I'm also thinking that the power itself is not the cause but the effect. I'll be sleeving an aftermarket cylinder back down to a stock 175cc but the sleeve also gives me the ability to set the port area, timings, and angles as desired.

    Questions:
    With power being a combination of BMEP and RPM, do I have to give up both?

    What has the largest impact on engine life?
    1. Engine speed
    2. torque/power
    3. temperature
    4. other

    Given it's a forced air cooled engine, are there BMEP limits I should not expect to be able to exceed in sustained operation?

    Current modeling in EngMod has me at 25hp @8000rpm and trying to decide if I should just be happy with that or try for more.
    Disclaimer: I've never seen a lambretta in real life.

    Temperature will be an issue so having a sleeve will be the worst thing you can do. Are there not aftermarket (ally, I assume they are iron stock?) Cylinders? - Edit: seems the internet is filthy with them.-

    Rebuilding the crank with mx conrod parts if possible. And piston.

    What usually fails in these things?

    I'd also find a dirtbike stator and cdi for reliable sparks.
    Don't you look at my accountant.
    He's the only one I've got.

  6. #32541
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    25th March 2004 - 17:22
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    Quote Originally Posted by ken seeber View Post
    Mid this year in the Netherlands I had the privilege to catch up with one of our 2 stroke technical legends, Frits Overmars. During this day, we visited a couple of locals, Henri Tiben and Martijn Stehouwer, both who are up there in the 50/125 cc racing scene. Getting the idea that this sounds strong, I asked the question “how often could you ever race?”, the answer being “every weekend if we wanted to”. I guess the tyranny of distance is less of an issue over there.

    Anyways, Frits very generously gave me a library of pics, all carefully catalogued into various companies. I say generously, as this collection is a product of many years of his association with, and just good old passion for, something we are all here for. The 2 stroke. Must say it was quite humbling.

    However the generosity was not to just me, but everyone here. Being a bit of a slack arse and distracted of late (again), figured it’s time to get them out there. Turns out that getting 2.2 GB of pics out there is not completely simple, certainly well beyond Kiwibiker’s posting limit.

    DropBox has a 2 Gb limit so that’s out, but Google Drive is our friend here:

    https://drive.google.com/drive/folde...of?usp=sharing

    Enjoy

    Attachment 342940
    Golly. Thanks Frits and Ken. Epic.
    Don't you look at my accountant.
    He's the only one I've got.

  7. #32542
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    12th February 2004 - 10:29
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    No expert on Lammys but they are fan force cooled which is a limiting factor for long periods running at speed. As F5 says the sleeve is a bad idea for the reason given. I've got a watercooled barrel coming for my scooter. Evidently this on it's own, leaving the head aircooled is sufficient. Or maybe not if it's 2-stroke.

  8. #32543
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    13th December 2018 - 18:06
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    Quote Originally Posted by ceci View Post
    I have made a mistake ?.
    it has to rotate compressor impeller more than the crankshaft
    Yes, considerably more.

  9. #32544
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    12th October 2016 - 01:24
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    I know a sleeve adds a barrier to cooling, but it will still be an alloy cylinder with iron sleeve, better than the full cast iron as stock. One reason for doing this is that the cylinder spigot is only 3mm thick and this is a failure point, so bringing it back to a smaller bore and 4mm thickness should help (still really thin by modern 2T standards).

    Not asking how to make a Lambretta reliable, wrong place for that, more about where to de-tune.

    For example, to hit 25hp I could get there with:
    6.0 BMEP @10,500rpm, mean piston speed of 20m/s
    vs
    7.5 BMEP @8500rpm, mean piston speed of 16m/s

    Assuming I will have to sacrifice some BMEP, but do I? or is the wear mostly from piston speed and I could have 10 BMEP at 8000rpm for 30+HP (assuming I have the porting to do that)

  10. #32545
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    1st May 2016 - 13:54
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    Quote Originally Posted by OopsClunkThud View Post
    Question about tuning for longer engine life:

    I'm building a Lambretta engine for endurance road use and bucking the trend of trying to get as much displacement/power as possible. I need to be able to do 300 mile days for several days in a row. I know I'll have to give up power but I'm also thinking that the power itself is not the cause but the effect. I'll be sleeving an aftermarket cylinder back down to a stock 175cc but the sleeve also gives me the ability to set the port area, timings, and angles as desired.

    Current modeling in EngMod has me at 25hp @8000rpm and trying to decide if I should just be happy with that or try for more.
    This is not the usual 11/10ths search for bucket HP. But ESE is a bit quiet and this is also where my head is at present.

    I'm building up a Bultaco Metralla from over 40 years of parts collecting.
    Not as a TSS race replica but just a strong, reliable, fun and useful weekend ride bike.
    The Metralla probably provides a good model for your endurance Lambretta.

    For a 100mph 250cc 1960's production bike, its state of tune was simple and mild, (just 2 little transfers) and almost identical to the Matador ISDT enduro bikes. They did not 'wear out' in a week, a month or even a year. Claimed 27bhp @ 7500 rpm.
    (Racing kit lifted this to 32 @ 8200, about the same as the Pursang MX)

    Frits & Wobbly have repeatedly advised that 'heat' is the nemesis of extracting power from air-cooled engines.
    More HP production means way more waste heat to be dealt with.
    Since HP = Torque X rpm, limiting the revs but maintaining sufficient torque to achieve the operational task is a good way to go with old air cooled engines. Any mods I do to the Metralla will be designed to keep the operating rpm at around the 7500 level.

    Tons of info out there in google land about building tuned chambers to maximise peak HP, not much about pipes for general two stroke use. Wobbly provided some excellent information about de-tuned exhausts with plate baffles and their ability to extend powerbands well below & above the nominal tuned length rpm. Also about Vevey pipes with perforated rear cones in resonating chambers doing even better. One pipe software vendor now offers a similar option. I'd like to convert a standard Metralla plate baffled pipe to a perforated cone but haven't found any info about how to determine the required rear chamber volume.

    For your project more cc and std rpm looks like a good way to go. Not sure how you change final gearing on a scooter, if needed.
    A cast iron sleeve might be a barrier to cooling but in an old air cooled cylinder it also provides some dimensional stability.

    Cheers, Daryl

  11. #32546
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    19th October 2014 - 17:49
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    Patrick, I'm pretty sure I've read somewhere that wear increases with the square of the speed change so keeping a reasonable RPM on the scooter sounds like a good idea to me.

    You might also look into some of the lubricant coatings for pistons/cylinders. They may need to be renewed periodically but your scooter probably isn't racking up lots of miles to where the cost would be exorbitant to refresh things. KalGuard, SwainTech, TechLine, etc.

    Coming from a background of big 4t singles and twins for a street ride I'd probably shoot for a nice fat midrange power that lets the gearing be raised so you can still have a decent ride but not be pushing the RPM to the limit.

    cheers,
    Michael

  12. #32547
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    12th October 2016 - 01:24
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    Quote Originally Posted by Pursang View Post
    ...Also about Vevey pipes with perforated rear cones in resonating chambers doing even better. One pipe software vendor now offers a similar option. I'd like to convert a standard Metralla plate baffled pipe to a perforated cone but haven't found any info about how to determine the required rear chamber volume...
    thanks for that!

    found this post on the topic, not sure yet how to model it in EngMod

    https://www.kiwibiker.co.nz/forums/s...post1130788402

  13. #32548
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    Quote Originally Posted by OopsClunkThud View Post
    thanks for that!

    found this post on the topic, not sure yet how to model it in EngMod

    https://www.kiwibiker.co.nz/forums/s...post1130788402
    Yes that's the area, also a really good expanded one at 7:31 the day before (04 Nov 2014).

    Not much info online, and it's all kart related. 'Vevey' pipes might have been originally created to satisfy noise restriction requirements for karts at the Vevey race circuit in the late 60's??? Earliest ones just had the perforated rear cone, then a 'silencer' box was added, then tuning of the box volume and finally pressure with stingers.
    Some pics here about 'volume tuned' exhausts & other kart stuff.

    If you work out how to EngMod it please let us know.

    Click image for larger version. 

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    Also the 2 stroke Wizard duel power pipe Click image for larger version. 

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    cheers, Daryl.

  14. #32549
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    Quote Originally Posted by SwePatrick View Post
    Successfully relocated pins:

    good job mate. I thought of trying that horizontal pin method but I have no experience with it and lm sure I would of buggered it somehow . instead I felt less nervous making a vertical hole to fit a needle bearing then closing the hole, since ive done it before on another pistons.
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  15. #32550
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    peewee, did you peen the hole shut or give it a quick burst with a TIG welder to melt it shut?

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