Scooterotica

drunkmunkey6969 wrote: Yes, we did it on an RB20 motor that a customer is running round on, and it worked for that application, as you know....having your own dyno gives you the luxury of testing whatever you want and PROVING what works and what doesn't.

so you have a dyno graph you can show us that would be great to see


On this motor, larger transfers were beneficial, we gained a small amount of power right across the rev range.

Darrell Taylor wrote: have you read my comment about transfer window size constantly changing
in my example a 20mm wide transfer at 1mm open is 20 sq mm the std duct entry is 600sqmm so the ducts entry is 30 times bigger !!
many modern race engines have larger transfer duct entrys but have you seen the ultimate 125 gp motors transfer ducts? approx 1 to 1 ratio

Fair enough (so you agree)

, but a Lambretta is not an ultimate gp motor is it, you have to compare like for like
(so why are you comparing lambretta engines to big motorcross motors and modern 125 engines).

And presumably the cylinder transfers on the ultimate gp are larger than a Lambretta cylinder, so at 1:1 the ultimate gp will make sense.....
(i cant see how that makes sense if the windows are bigger than a lambretta cylinder then your now saying the entry should be smaller????)

and if we are enlarging transfer ports on the lambretta cylinder wall, then we will want a large entry to match.(see what i mean not making sense??)

But i see what you mean, (are you sure ????)

although surely the crankcase window size/area should at least match the cylinder transfer area when they are fully cracked open and not just when they are 1mm open??

as per my post? i said at 1mm open the entry is 30 times bigger
and when they are fully cracked open the entrys are still bigger than the windows and the majority of the transfers work is done

Or can you offer further info on why this is not the case? Please explain why if so, i'm interested to learn.
upon first opening of the transfer,there is only a little transfer but a continuation of blow down spent charge is entering the transfer port contaminating the charge luckily the short circuiting of this first batch of contaminated charge is lost out of the ex port to be never seen again ,the remaining charge will exit via a small opening say 2mm at a greater velocity than when the port is fully open and if the transfer system is designed well will be put to good use
When the ex port is fully open and the transfers are fully open they are exposed to the adjacent exhaust port increasing the likelihood of lost charge this charge is the good stuff fresh/cool and has no contamination ,Now we dont want to lose that and fortunately at this point we have a lower velocity stream emerging that wont fire it straight out the exhaust

And lastly.......do you not find that when the piston is nearly at BDC that the transfer window in the crankcase is almost blocked/closed.....another reason why we modify pistons and transfers, let me know your experience in this case.

ive never bothered except for matching cutouts to the liner,i genarally do a simulation to find crank angle related flow data and match up at the angle thats most beneficial

Darrell Taylor wrote:

drunkmunkey6969 wrote: Or can you offer further info on why this is not the case? Please explain why if so, i'm interested to learn.
upon first opening of the transfer,there is only a little transfer but a continuation of blow down spent charge is entering the transfer port contaminating the charge luckily the short circuiting of this first batch of contaminated charge is lost out of the ex port to be never seen again ,the remaining charge will exit via a small opening say 2mm at a greater velocity than when the port is fully open and if the transfer system is designed well will be put to good use
When the ex port is fully open and the transfers are fully open they are exposed to the adjacent exhaust port increasing the likelihood of lost charge this charge is the good stuff fresh/cool and has no contamination ,Now we dont want to lose that and fortunately at this point we have a lower velocity stream emerging that wont fire it straight out the exhaust

And lastly.......do you not find that when the piston is nearly at BDC that the transfer window in the crankcase is almost blocked/closed.....another reason why we modify pistons and transfers, let me know your experience in this case.

ive never bothered except for matching cutouts to the liner,i genarally do a simulation to find crank angle related flow data and match up at the angle thats most beneficial

At last i caught a fish.......took enough bait though!! lol

That is quality info, much appreciated.

well im glad you,ve found it of use
when i wrote it i thought youll either read it with interest or kick off in disagreement
which its ok to disagree as we all have our own views on how things work and im not saying that my view is correct other than its working extremely well for me.

There's a school of fish in that lot.

Because of the constraints of the lambretta engine getting the transfers too big is not really an option. Big as you can get without welding is still not big enough. Obviously the port in the barrel doesn't want to be too big and this creates a venturi.

When does the 'friendly' bit start I wonder?

Well said Sticky, i couldn't agree more. I've always had the upmost respect for the scooterotica advice / opinions, however the last two days has changed the way i think. Darrell seems like a spot on guy who is willing to explain his knowledge of two stroke tuning principles for the benefit of everyone on here, even though he has been ridiculed by the certain members ot the scooterotica team at times. The same people who are now trying to lure him through antagonistic posts into revealing the secrets of his trade / livelihood, as well as asking Carl to reveal what Ryan does to get his results. Reading between the lines this makes me think that maybe they dont know / understand as much as they let on and are looking to increase their Knowledge through confrontational posts. I dont claim to understand most of what has been posted by Darrell etc, however i appreciate their efforts. I am not however reading other tuners advice in order to use it for my own commercial gain, as seems the case here. Maybe running a forum and business can result in a conflict of interests. Ps. Can someone pm me Darrells contact info, i want some "Darrell ports " for my TS1.

i couldnt agree more ferritt, darrell sounds like a decent bloke but for some reason he seems to be getting a bit of a hard time on here, Its not many people who would share a bit of there knowhow on a forum, most tuners stay well away from forums for the very same reason that seems to be happening here, theres not manny people have the courage to go on using there own name either, good on you darrell, shows your not scared to hide behind a keyboard either,,,,

cut the guy some slack,,,,, he mite one day be able to help you out

Hey, I too also agree that Darrells a nice guy and sure does know his stuff....and with hind sight i do somewhat regret the way that i have treated him so far, as it did come across as harsh and bullying i do admit. But it was never intended that way, and the thing is, which many of you on the open forum may not appreciate is that as admin/moderator...we do get such a lot of things going on behind the scenes...and are sometimes subjected to all sorts of comments/advice/warnings etc etc from all sorts of folk and in Darrells case we have in fact been inundated in that respect and as admin etc, so we simply would not be doing our job if we ignored these things...hence our initial concerns about Darrell...and so raising awkward questions etc about the fact of his ban off the FS1e forum.

I have absolutly nothing personal against darrell at all and no axe to grind, in fact (as i've always said)i admire his skill and results.
I do admit now that i was a pratt to him, and was just trying to wind him up and I only did that cos of all the previous warnings from others that i had saying that darrell was a trouble maker etc....

It all sounds so silly now, but i was at the time just trying his patience out/testing him to see if the other folk were right...and TBH, do you know what...I think that Darrell is a star...he was not only patient/polite but also helpful despite my p155 taking...so 10 out of 10 to Darrell.....