ESE's works engine tuner

[Maxdelta]

What was that original pic Max? Not an RM250 as obviously oil injection. So guessing RG250. 1/2 Reed barrel so you don't need monster inlet area and you can get heaps normally. I'd concentrate on anything else.

Like re-engineering the crank to use better rods if you want to rev it a bit more.


Dave,
Its a Suzuki snow cylinder (Arctic Cat 580).

[Maxdelta]

Thanks Wob,
This cylinder has the C ports ducts that are fed right along the outside of the intake port, so there is minimal meat there to widen the port. Also, no room left to lower or raise the port. Hence my looking into the possibility of removing the bridge. The stock bridged intake port width is ~68% of bore. Maybe there's not much left that can be done to this port? I could square off the bottom corners to gain some more area, and I can widen approx. 1mm per side.

356886356887

[wobbly]

Depends on how the intake STA sits in comparison the the Blowdown , and the amount you would gain by increasing the Intake duration ( cut the skirt ) - against loosing bottom end.
Use JanBros spread sheet and analyze the ports.

[katinas]

.
356885

An interview with Dane Rowe, a hottie from the 60's

https://rocinantemecanico.blogspot.com/2012/04/surprise-guest-my-interview-with-dane.html

Great interview.

Thanks

[Frits Overmars]

An interview with Dane Rowe, a hottie from the 60's
https://rocinantemecanico.blogspot.com/2012/04/surprise-guest-my-interview-with-dane.htmlI always admired Dane Rowe and I enjoyed the interview but if I'm not mistaken your picture does not show Dane Rowe but Dutch sidecar passenger Anneke Mak.

[Maxdelta]

Depends on how the intake STA sits in comparison the the Blowdown , and the amount you would gain by increasing the Intake duration ( cut the skirt ) - against loosing bottom end.
Use JanBros spread sheet and analyze the ports.

I'm using Engmod. Basically i can't get enough intake STA. Blowdown and transfers are at ~120hp each. Intake is ~80hp. If removing the bridge isn't an option, then it seems my options are to square off the bottom corner radii and cut the piston skirt. Which leads me to ask....what's a reasonable amount you can remove from the skirt? Would 2.5-3mm be asking for trouble? Thanks for all the assistance.

[katinas]

I'm using Engmod. Basically i can't get enough intake STA. Blowdown and transfers are at ~120hp each. Intake is ~80hp. If removing the bridge isn't an option, then it seems my options are to square off the bottom corner radii and cut the piston skirt. Which leads me to ask....what's a reasonable amount you can remove from the skirt? Would 2.5-3mm be asking for trouble? Thanks for all the assistance.

I remember there was always a dilemma with piston ported engine intake, where to go from std, cut the piston or lowered intake port bottom or just lift the roof. But in any case dont remove the bridge as Wobb advised.
My last experience with piston ported engine was in 1998 with 340 cc single cylinder engine for road race with wide bridge, served as a C channel.
Best final results was nearly std intake ports roofs and bottoms just widened, but huge piston skirt cut ( step by step 3mm then 6 mm and finally 10mm).
I cant remember accurate duration aprox 190. Main advantage over port grinding ( bottom and roof) is that the piston skirt remains hidden from the suction flow for a longer period of time (similar to disc valve long cut).
And bridged port not only save engine, but allows you to make the bottom edges sharp, which, together with piston inside intake skirt sharp edge resist for reverse flow better.

[wobbly]

If you are using EngMod then its real easy to see the effect of cutting the skirt on bottom end power as you approach equality in STA with the Blowdown.
You can also adjust the intake length to see if power can be gained by increasing the air column and thus ram into the open port.

[JanBros]

Use JanBros spread sheet and analyze the ports.

sadly, there is nothing in it for the intake to analise. reedvalve only.

[wobbly]

Sorry JanBros , didnt realize.
But further on the intake scenario , the old TZ350 responded real well to cutting the skirt around 2mm and lengthening the tract 20mm with a plastic spacer from the 250 model.
And how close to the ring is the port top at BDC - can you ditch the bottom ring and grind that much upward - depends upon the skirt length a TDC.

[Peljhan]

I am wondering. If we have an engine with matching STAs let's say 30hp for each system (intake, transfers and exhaust) and we measure 30hp on a dyno.
Than we make-increase STA on one of the systems to 40hp. What would we measure teoretically?

[wobbly]

As long as everything in your sim is capable of achieving the 30 Hp of the STA prediction, depending upon the inertia of the vehicle components and the friction component, then you
will measure something like 14% less on a rear wheel Dynojet = 25.8RWHP.
EngMod calculates crank power - so if you now upgrade every part of the engine ( not just change the ports ) then the same applies to the new prediction.
Note the Exhaust STA is pretty much irrelevant ( except when using the duct exit radio button shortcut ), its the Blowdown that is highly important.

[katinas]

Sliding pipes from eighties. I just wonder when they really started using it.

From 21:21- https://youtu.be/2RZ86QoA-qI?si=ZuxwBLNCCw_762ih

From 0:35 https://youtu.be/D1e_vKt8Va0?si=lATwZp9HRV_D4QAw

[Jonny snatchsniffer]

I know most of you on here dont like air cooled 2 strokes because of thermal limitations, but i have what i have, its a 200cc lambretta piston ported no reed, the intake is only 153.5, exhaust angle 180, a and b transfers at 120, boost port 122.5, now im using a pipe from the 80's which has a long parallel header, also a 28mm pwk, the inlet is bridged, tz350, you probly know about the ported stuff, tho saying that most of us have been there done that, but my thing is Italian shopping bikes, and wobbly, when you worked with Jim did you do any of the scooter, like the jl3, jl4 lambretta pipes? And could they be improved upon?
I dont have engine mod and just threw it together with the above timings and thrashed the fuck out of it 140M to a rally but runs out of puff at 8000rpm @76mph gps
I know its over 60 yrs old but I'd like get more out of it
My 125 1966 vespa has 27 rwhp so surely I can get more out of a 200, thi over square at 58x66
So what should I be doing in my man cave to get it singing a bit more? I'm also stud limited and single chef hat exhaust port

[wobbly]

The scooter pipe thing happened after I left JL.

[Gradella23]

The scooter pipe thing happened after I left JL.

hello Wob, any sneak peek on the newcoming Kz R3? I saw Franco joined LKE, i was quite shocked

[Wos]

I know most of you on here dont like air cooled 2 strokes because of thermal limitations, but i have what i have, its a 200cc lambretta piston ported no reed, the intake is only 153.5, exhaust angle 180, a and b transfers at 120, boost port 122.5, now im using a pipe from the 80's which has a long parallel header, also a 28mm pwk, the inlet is bridged, tz350, you probly know about the ported stuff, tho saying that most of us have been there done that, but my thing is Italian shopping bikes, and wobbly, when you worked with Jim did you do any of the scooter, like the jl3, jl4 lambretta pipes? And could they be improved upon?
I dont have engine mod and just threw it together with the above timings and thrashed the fuck out of it 140M to a rally but runs out of puff at 8000rpm @76mph gps
I know its over 60 yrs old but I'd like get more out of it
My 125 1966 vespa has 27 rwhp so surely I can get more out of a 200, thi over square at 58x66
So what should I be doing in my man cave to get it singing a bit more? I'm also stud limited and single chef hat exhaust port

In germany there is a very good old scooter specific forum called german scooter forum (gsf)

If you ask your questions there even in english i am pretty sure you find specific help:2thumbsup

But its always worth to stay here, listen what others do in the big 2 stroke world ;)

https://www.germanscooterforum.de/

Grüße Wolfgang