ESE's works engine tuner

[Sketchy_Racer]

no,no,no,no,no,NO.

I'm guessing that's not the way to do it then

In Engmod all the port dimensions are normal to the flow direction, or simply chordal width.
Anything ( paper or Solidworks unroll feature ) is nothing like what is needed, as this is circumferential width.
In most all cases the A port is flow direction, the B and C are chordal as is the T port.

This would still be possible to use the paper scratching in solidworks to measure for the chordial widths, No?

Dont forget to calculate the T port pocketing correctly as well.

Not sure I understand this part, care to elaborate? Thanks Wob.


-Sketchy

[Sketchy_Racer]

Basically you have two options for stroking the cylinder. (please note I am not calculating the longer conrod as it boils down to adding a spacer below)
with the longer stroke the piston will go 2.25mm more up and 2.25mm more down.

1) you leave the cylinder as it is, provided you have enough deck height for the piston ring to stay into the cylinder, and do the porting for the new stroke
this is not optimal because you will have the lower part of the transfer ports floating 2.25 mm above the piston at BDC.
You loose piston cooling and time area.
You could work the ports down but this is very difficult to do correctly, it is easy to break the inner radius of the ducts.

2)you take away 2.25mm from the bottom plane of the cylinder, AND add 4.5mm of deck height. If you have enough, great, otherwise you have to weld a slice on the deck and redo the plating.
Or does it have an iron bore?
In this case there's also a lot more porting job to do, but it would be the nicest way.

I did a couple as in case 2).
The cylinder i'm using currently is both bored from 47.6 to 52 and stroked from 39.3 to 46. totally worth it.

I'm going to have to do it as per case one. The cost involved of building up and re-plating cylinders is a great deal of work. I'm hoping that it will be possible to keep the duct radius in a good shape after porting.

I do have the luxury of having a couple of knackered cylinders that I can cut in half to get a better look at the existing geometry as well as have a practice on that first.

[TZ350]

Don't forget to calculate the T port pocketing correctly as well.

Not sure I understand this part, care to elaborate? Thanks Wob. -Sketchy

Something like this maybe. The left is a T port, the right a Triple port, anyway it will be interesting to see what Wob says.

[wobbly]

In the diagram the A width is way smaller than measuring it like B.
If you take B and roll it out flat the circumferential length will be way wider again,and has no relevance at all to what we
need in EngMod.
You can measure B easily in the SolidWorks model by picking the two vertical port edges and using the measure function.
One of the width options will be the chordal distance.
But A must be measured using bent,ball ended dividers,in the direction of the duct flow actually in the cylinder,unless you have got clever and have modeled the
transfer ducts as well.

When you select T port in the Exhaust page, at the bottom it asks for the duct side exit angle C.
This is pocket exit angle, and done right it makes a huge difference to power in a T port.

[Sketchy_Racer]

Thanks heaps guys for the info, very helpful! I see that I am going to lose quite a few hours in this program!

[chrisc]

A KTM 65SX with a 50SX-cylinder (smaller bore, same stroke) is a good tool for 50 cc racing. One drawback: it has no balance shaft, so the way you mount the engine will influence the life span of the frame, the functioning of the carburettor and the amount of numbness in the rider's hands and feet.
The latter may sound futile, until you've experienced the difference between engines without and with a balance shaft. Vibration costs concentration.

Thanks for pointing that out Frits, I hadn't noticed that it didn't have a balance shaft! Rod and I rode his TZ125/AM6 bucket in the 2 hour in November to 3rd place. After that I couldn't feel my right foot and left hand from numbness and that does have a balance shaft. Rider comfort is high on my priority list after learning the hard way how much time there is in it on both my bucket and NX4 RS125.

I've test ridden 3 air cooled 125cc buckets with no balance shafts which although they went like rockets, vibrated like hell. If I had a choice, I'd get away from that as much as I could in a freetech bike where you have so much choice. Anyone care to suggest other alternatives to the KTM SX, AM6 and Derbi?

You've commented a few times about the appropriateness of using a RS125 chassis for a freetech 50 bike Frits, I'd love to continue that conversation but maybe without clogging the ESE thread. I'll ask the question on the race chassis thread

[Frits Overmars]

A must be measured using bent, ball ended dividers, in the direction of the duct flow actually in the cylinder.

I have a simple tool: a set of feeler gauges converted to an inner compass. Grind two of the feeler tips like in the drawing and you're done. You can even still use all of the feeler gauges.
I insert my compass in a port from the inside of the cylinder bore, push the legs against the duct sides, and then pull the compass back so that the legs are pushed towards one another. That way it is easy to find the minimum cross sectional width. Finally I measure that width with a caliper.

When you select T port in the Exhaust page, at the bottom it asks for the duct side exit angle C.
This is pocket exit angle, and done right it makes a huge difference to power in a T port.

Here are some sketches to go with that remark.

[Frits Overmars]

Thanks for pointing that out Frits, I hadn't noticed that it didn't have a balance shaft! Rod and I rode his TZ125/AM6 bucket in the 2 hour in November to 3rd place. After that I couldn't feel my right foot and left hand from numbness and that does have a balance shaft. Rider comfort is high on my priority list after learning the hard way how much time there is in it on both my bucket and NX4 RS125.
I've test ridden 3 air cooled 125cc buckets with no balance shafts which although they went like rockets, vibrated like hell. If I had a choice, I'd get away from that as much as I could in a freetech bike where you have so much choice. Anyone care to suggest other alternatives to the KTM SX, AM6 and Derbi?

There must have been something wrong with the timing of that AM6's balance shaft then. The AM6 can be quite civilized, vibration-wise.
I don't know all the engines that could be considered, but Derbi seems to be the most-chosen engine, preferably pimped with a KTM 50SX cylinder or an Emot cylinder.

You've commented a few times about the appropriateness of using a RS125 chassis for a freetech 50 bike Frits, I'd love to continue that conversation but maybe without clogging the ESE thread. I'll ask the question on the race chassis thread

Did I? My intention has rather been to comment on the inappropriateness of an RS125 chassis, or any other 125 cc chassis for that matter.
They are simply too heavy for a decent 50 cc racer. Anyway, see you there: http://www.kiwibiker.co.nz/forums/sh...chassis/page43

[41juergen]

Frits, I believe some longer time ago you mentioned how to define the size of the radius of the upper ExPort.... Was that something like approx. 4% of the bore?

[adegnes]

Anyone care to suggest other alternatives to the KTM SX, AM6 and Derbi?
:

Derbi flat reed maybe? With a powerful cylinder of course.

[nasone32]

YEAH i'm back to engines! today i enlarged the conrod window a fair amount. on the manual mill.

Also a little picture of the 52mm cylinder. Still have to round that edge inside and lot of porting to do. But i'm not planning to use this cylinder anyway. it's 100cc max and this would give 101,8cc.
So i'll stick with the 50mm bore and 95cc.
Unfortunately the regulations have changed to allow for 100cc, it was 95cc the year i designed the engine. otherwise I would have gone for a 50x50 instead of 50x48.
at that time most people was using 52x44 (94cc) because it was the most common "long stroke" for the stock crankcase. so they made the rules to suit that.
That's unlucky because i'm leaving behind a 5% of power.

and also a pic of the frame.

[adegnes]

Lookin' good!

[TZ350]

I love these little sprint bikes.

[peewee]

YEAH i'm back to engines! today i enlarged the conrod window a fair amount. on the manual mill.

Also a little picture of the 52mm cylinder. Still have to round that edge inside and lot of porting to do. But i'm not planning to use this cylinder anyway. it's 100cc max and this would give 101,8cc.
So i'll stick with the 50mm bore and 95cc.
Unfortunately the regulations have changed to allow for 100cc, it was 95cc the year i designed the engine. otherwise I would have gone for a 50x50 instead of 50x48.
at that time most people was using 52x44 (94cc) because it was the most common "long stroke" for the stock crankcase. so they made the rules to suit that.
That's unlucky because i'm leaving behind a 5% of power.

and also a pic of the frame.

nice job nasone. im working on a sprinter as well

[TZ350]

Is this a snowmobile sprinter?