ESE's works engine tuner

[teriks]

Did you try the sequence described in my post?

Windows, XP pro ver 2002 service pack 3 and yes I work down the page in order when creating a new project.

I very much like the EngMod2T programe, lots of great features and after two days and a bit I can create a project, process it and display sensible graphs. Modelling the carb and inlet tract and accuratly measuring the theta angles of the transfers are a bit of a trick. I havn't been able to produce a graph that accuratly matches my existing motor yet, that might take a bit of time but I expect I will get there.

Wob, Great work on Trevors engine, its great to see someones bringing the old TZs into the modern age.

Yup, same sequence, only I stopped after

In the Header Pipe Restriction field
Entering any number without deleting the “0” first results in a Dat2T error message.

Using the same Windows version as well.

I find that I have made a habit to mark the initial number and enter the new without deleting the initial value.
Guess that's why I don't notice these things..

[Frits Overmars]

at the entrance to the transfers the rsa aprilla has very wide dividers between each one while most tuners would narrow these down, i wonder what people like frits think about this or does it not matter.

It matters, Pete, as a lot of Italian kart engine manufacturers and tuners will reluctantly confirm. They all copied the Aprilia cylinder and while they were at it, they could not resist correcting the 'errors' that Jan Thiel had left behind. And then they were surprised when the engine made less power instead of more .
It's not that simple to improve the best two-stroke cylinder in history .

[TZ350]

EngMod2T

One of the inputs required is the transfer duct angles across the bore. Working them out had me stumped for a while but in the end this is how I went about measuring them, simple as.



Take one piston, cover it with masking tape and mark out some reference lines.



Put the piston in the cylinder and using a wire bent to fit inside the transfer ports mark out the angles using the wire as a guide.



I coloured the segments to make them easier to see.



Measured the angles and off sets and entered the data.



And yes I think I got it right as the software gave me the numbers I was expecting and it has drawn a picture of the ports that look like the shapes on my piston top.

[koba]

Jeebus that's a big Exhaust port.

Is that the 75% one that went clank?

[TZ350]

Jeebus that's a big Exhaust port. Is that the 75% one that went clank?

The transfer ducts screen only deals with the transfers, the exhaust pictured on it, is only there so you know which way is up.

If you mean the cylinder, Yes ... and soon to be resurrected too.

[dmcca]

It matters, Pete, as a lot of Italian kart engine manufacturers and tuners will reluctantly confirm. They all copied the Aprilia cylinder and while they were at it, they could not resist correcting the 'errors' that Jan Thiel had left behind. And then they were surprised when the engine made less power instead of more .
It's not that simple to improve the best two-stroke cylinder in history .

Frits, first of all, thanks for your willingness to share info with us... Your ideas have inspired me

It sounds like a lot of the development of the RSA cylinder went into transfer duct geometry... are there any more secrets you can share about the key characteristics that led to such huge power...

Is there any single aspect of transfer duct geometry that offers greater gains than others??... inner duct radius, window/port ratio, radius at bore edge, widening factor just before the port exit, etc. Or is it simply a case of 'the whole being greater than the sum of the parts'.

***EDIT... just been looking more closely at the RSA cylinder transfer ducts... it looks like the inner duct radius is different between secondary and main transfer ducts... Also it seems that the window/port ratio is very different between secondary and main transfers... Im assuming that the flow in the secondary ducts accelerated faster as a result?... were both ports opened at the same time or were staggered transfer timings used?

Sorry for all the questions, just trying to understand the efficiency of the design.




Engmod2T question...

On the topic of transfer geometry, when modelling the transfer window/port ratio, I have been measuring this at the horizontal plane of the base gasket surface (ie measuring the entry to the ducts as shows in the photo Frits posted above) while the drawings in the help files seem to show that it should be modelled along the vertical plane where the cases widen either side of the crank. It has a significant affect on the length of the port depending on which one is chosen (and therefore affects duct volume and crankcase comp ratio).

Which is correct?




Ignitech/starting advance question...

Ive been playing with base advance after experiencing hard starting on my CR280 build... it was kicking back, backfiring and was very hard to start... i quadruple checked everything and determined that base advance was 8 degrees which i though should be fine, however after playing with the stator plate i have now settled on 2 degrees base advance (the minimum i can physically go to) and starting is much easier, much less kickback and very smooth idle. I tried it at 10-15 and it nearly broke my ankle.

Im still trying to account for why it is hard to start at even 8 degrees base advance...Im running a custom toroidal combustion chamber at 13:1 compression ratio... Jetting seems ok. Im wondering if the toroidal head has sped up combustion to the point that even 8 degrees advance is too much for starting, resulting in kickback... or possibly the fact that the bore centre is offset 1mm to the rear, could that resulting change in crank angle at tdc make it that much more susceptible to kickback??...

Just trying to get my head around why it needs so little advance to start?? Once running it is very strong at 25+ degrees advance and shows no sign of detonation even when experimenting with advance up to 35 degrees and super lean jetting.



Dave.

[Frits Overmars]

Frits, first of all, thanks for your willingness to share info with us... Your ideas have inspired me. It sounds like a lot of the development of the RSA cylinder went into transfer duct geometry... are there any more secrets you can share about the key characteristics that led to such huge power...
Is there any single aspect of transfer duct geometry that offers greater gains than others??... inner duct radius, window/port ratio, radius at bore edge, widening factor just before the port exit, etc. Or is it simply a case of 'the whole being greater than the sum of the parts'.
***EDIT... just been looking more closely at the RSA cylinder transfer ducts... it looks like the inner duct radius is different between secondary and main transfer ducts... Also it seems that the window/port ratio is very different between secondary and main transfers... Im assuming that the flow in the secondary ducts accelerated faster as a result?... were both ports opened at the same time or were staggered transfer timings used?

The outer transfer duct radius is utterly unimportant; there the charge has no option but to go where the duct wall leads it. But the inner duct radius is very important: it should be as large as possible to avoid flow detachment. If you manage to keep the flow clinging to the inner surface (the Coanda effect), there will be less pressure-absorbing turbulence, so the flow will meet less resistance, transport more mass and deliver it where you want it to go.
The golden rule of flow: look for sharp inner edges and remove them. It always works.

The radii at the bottom bore edges, as visible in the picture above, yielded 1 HP; that's about 2% of the total power. The egdes where the transfer port windows cut the bore, should not be radiused; you do not want to promote inflow of waste gas into the transfer ducts. Here only the top and bottom edges should be chamfered lightly to make life easier for the piston ring.
There should be no widening just before the port exit; the duct cross-section area should gradually move from entry area to exit area. And with the inner curvature of the duct fixed, this more or less lays down the shape of the outer curvature.

Assuming that the flow in a duct will accelerate faster as a result of narrowing that duct is an ineradicable misconception. If it were true, it would mean that a duct narrowing to zero would yield an infinite flow velocity......
Flow velocity depends on the pressure difference between entry and exit of a duct, and in the case of an engine, where the flow constantly accelerates and decelerates, it also depends on the column length of the mass in the duct. It does not depend on the column's cross-area; twice the area would mean twice the mass per mm column length, but it also means that the cross-area exposed to the pressure difference is twice as big.
A smaller cross-area can have the effect that because of the reduced mass flow the pressure in the crankcase does not fall as quickly, which in turn may lead to a longer-lasting acceleration of the flow and thus a slightly higher top speed. But it will also mean less mass transport during the transfer phase.

The duct entry area of the Aprilia cylinder's B-ports is slightly smaller than their port exit area. This stems from the old obligation to develop cylinders that had to fit the existing crankcases of the Aprilia RSW engine, of which there are hundreds around. the RSA engine did not have this limitation, but simply enlarging the B-duct entries disturbed the scavenging, so the ducts were left as they were (and remember: while the B-ports' exit areas are only open part of the time, the entry areas are open all the time).
The transfer timing is 130° for the A-ports (they are really close to the auxiliary exhaust ports) and 132° for the B-ports and the C-port.

[Dutch Fisher]

Thats good to hear as the crashes were driving me nuts while trying to find my way around a new application.

The sequence leading to a typical crash is.

In the Dat2T application.

Create a New Project.

On the Pipe Types screen.

In the Header Pipe Restriction field
Deleting the default “0” provokes a Visual Fortran Run Time Error.

In the Header Pipe Restriction field
Backspacing to remove the “0” provokes a Visual Fortran Run Time Error.

In the Header Pipe Restriction field
Entering any number without deleting the “0” first results in a Dat2T error message.

On the next page of the module backspacing to clear a field before entering a value invokes a Dat2T error.
.

You need to reinstall XP. Those errors are from the Windows DLL that DAT2T uses to display dialog boxes.

[pete 2]

Thanks frits,
so would their be a (correct) ratio between c/case volume and transfer duct volume for a high performance engine?
also on the rsa cylinder the liner has an opening in front of the boost port, while the honda 250 production racer has not,in the honda this is directly infront of the inlet from the reed block and appears to be an obstruction to the flow.

[NordieBoy]

You need to reinstall XP. Those errors are from the Windows DLL that DAT2T uses to display dialog boxes.

Errors in the visual fortran runtime mean you have to reinstall windows?

[Frits Overmars]

Thanks frits,
so would their be a (correct) ratio between c/case volume and transfer duct volume for a high performance engine?

Not really. The RSA's TDC crankcase volume is 675 cc (for a 125 cc engine!) but most of this volume is in the transfer ducts.

also on the rsa cylinder the liner has an opening in front of the boost port, while the honda 250 production racer has not,in the honda this is directly infront of the inlet from the reed block and appears to be an obstruction to the flow.

Over the years Honda has produced cylinders with and without the lip that your picture shows, sometimes both types in the same production year. But flow through the C-port is not the most important item of a fast cylinder.
Another point to help you make up your mind: compared to a Honda RS125 or RS250 the Aprilia RSA125 produces about 20% more power per cylinder....

[wobbly]

Re EngMod2T question on ducts and entry areas.
Depends upon the geometry of the duct in the case and that of the cylinder where the duct begins at the bore edge.
In many designs the inner wall is very short ( above the gasket plane ), and the case extension of the duct outer wall drops away very sharply - with the floor being miles away from the gasket plane.
In this case I would use the area/length at an angle from the bore edge out to just below the gasket plane.
Some engines have a longer inner wall, and also have the case floor close to the gasket surface.
In this design the duct really does "go around the corner" into the case and the ( vertical ) window forms the entry area, as shown in the help files.
Truth be known the main effect is to change the case volume, but this spec is always MUCH better to model accurately by drilling a hole in a piston at TDC, and calculating with the ducts included.
The case volume total has a bigger effect on the real power produced by the sim, rather than duct length.
Duct length, has a bigger effect on the sim run times, not power.
I tried to replicate the run time error as you found TeeZee, and yes my system does the same - I never found that issue as I have never changed the zero figure before.
None of the pipes I have done have a "step", always an oval to round transition in the flange, that is modelled as a short taper in the pipe screen.
So yes, send a report to Neels, it is a "fault".
He is working now on creating a "button" that will collect all the files used by a project, into one file, so its easy to send each other sims to check, making it much quicker for others to review projects already created.

Re Ignitech starting issues, and base advance.
Post up a screen shot of the "Bike" page and advance curve, I may be able to help with that.

[TZ350]

I measured my old RS125 pipe tonight ...


and it turns out to be the same dimensions as the bracketed ones in the picture.



The numbers on the left (Tuned Pipe Dimensions) are for the pipe itself. The numbers on the right (Tail Pipe Dimensions) are for the venturi restrictor at the end of the convergent cone and the tail pipe (stinger) length.



Then you can get a look at what the pipe will look like and check the tuned length.



The object is to simulate my existing engine and get a simulated graph that is the same as the real dyno graph, well similar as the simulator is crank hp and the dyno is rwhp. Then I can be pretty confident any changes I make in the simulation should be reflected on the dyno.

I am a bit of a newbee with the EngMod2T simulation package but getting there.

[Yow Ling]

One of the local bucket guys came round tonight with the bike he has been building. We just checked the squish and admired his work.
This is RG150 bottom end with VJ22 barrel with sleeve. Wish mine was this far done!

[TZ350]

One of the local bucket guys came round tonight with the bike he has been building. We just checked the squish and admired his work. This is RG150 bottom end with VJ22 barrel with sleeve. Wish mine was this far done!

Its what I thought after the GP, the writing is on the wall for the 4-stroke boys no matter how fast they can ride as the whole playing field seems to be moving up a notch or two.