Port Map Analysis

[chris2470]

I've a suspicion the piston ported engine will perform much better than first thought !!

[drunkmunkey6969]

ok here goes lol

1 is the 225 reed
2 is the 225 piston ported
3 is the 200 reed

Bingo.

1st is a TS1.....not as revvy as i thought it would be
2nd is a 225 piston port Indian Barell, that has had some porting work done.
3rd is an RB20......revvy little sucker aint it!

[tony]

Loads of these hi hp ts1's and rb motors probably have to rev silly high to make that power. The bmep could be lower than a lesser hp motor. So therefore the high hp motor is less efficient than the lower revving one because it has to be spun up to make the power-to shift more gas through the ports. So tuning is really about bmep increase not hp. Thats proper tuning. Its very easy to raise an ex port and make hi hp..thats not tuning..thats pub talk tuning. Also Bmep increase becomes harder with the less area you have.. ie a 2 port barrel.

[J1MS]

Loads of these hi hp ts1's and rb motors probably have to rev silly high to make that power. The bmep could be lower than a lesser hp motor. So therefore the high hp motor is less efficient than the lower revving one because it has to be spun up to make the power-to shift more gas through the ports. So tuning is really about bmep increase not hp. Thats proper tuning. Its very easy to raise an ex port and make hi hp..thats not tuning..thats pub talk tuning. Also Bmep increase becomes harder with the less area you have.. ie a 2 port barrel.

Had this conversation with a few mates over the years... more so since dyno's became the fashion... claiming big BHP figures but not actually going much faster in real terms, as its got to be kept in the narrower power band... my first attempts at tuning barrels were revs and more revs with little or no power low down, fun to ride.... but not really good for road riding and long distance touring... just increasing exhaust port height and inlet port timings (the easy ways of increasing revs and usually peak power) But re-shaping transferes in the bore then increasing flow and effective port area is alot harder... get this to work well with the exhaust system thats employed... get the inlet port timing/area to work to suit... then sometimes a little less pot timing and a little more toque can make for an overall smoother more responsive engine alot easier to ride but a little more work to do when porting...
A scooter I sold in 83 which was a 150 spanish LI, mildly ported, clubman and 22mm carb... the lad who bought it had it for about 2 years as it was... most thought it was a 200 because it pulled so well... port timings used were not much over std...

[tony]

Yes mate. You are right. Eventually people will wake up to the dyno talk. Its really about torque delivery, how wide it can deliver that amount of torque for..not how hi the hp is. Big hp is good but without the torque the bmep's are down and therefore its probable the bike will be slower as you say, harder to ride. What is required will be a very close gearbox and a good rider. This isnt really practicle for the road and rally type riding. I personally like hi-end feisty motors but then again I dont do rallies anymore.

[RinB]

I think we have have discuss this a fair bit now and It is apparent that the tune is not just about Port timings but alot about port area and the whole scavenging system ie transfers.

I for one play alot with the transfers and boost ports which people on here may well have guessed, as I quite often try to explain the benifits of the scavange period of a 2 stroke.

What I find intresting about these pics Dan is

What is the corralation of the tranfers Time area overlaping the Exhaust period
Ie TS & RB over lap Indian barrel well down rev range !!!!!

Lets discuss

Smiffy

PS as for Dyno Talk completely agree, Thats why I wont get suckered into it
Brill for initial setting up though

[RinB]

Did a port map for 3 Lambretta cylinders, a 225 reedvalve, a 200 reedvalve and a 225 piston port. I don't want to say which is which just yet, but i found the results quite interesting when i fed it into the port-time-area software for analysis.

See what you techy gurus make of the graphs, i'd be interested to hear your thoughts on theoretical power delivery, port timings, rpm, and to see if you can guess which is which.

Red bar is exhaust angle area and blue is transfers.

Exhaust and Trans port timings and blowdown in degrees shown in top left corner.

Angle area on vertical axis, rpm on horizontal.

Dan ive been re looking at these graphs TS1 & rb did you include all transfers + the Boosts
The boosts area being taken for area from the top of piston @ BDC to the boost ports top

Smiffy

[drunkmunkey6969]

Yes.

[DMC]

took bloody ages to find this post again.

A few questions for you guys, is the software any good? have you had any good comparatives against actual dyno runs?

[RinB]

took bloody ages to find this post again.

A few questions for you guys, is the software any good? have you had any good comparatives against actual dyno runs?

PM sent