ESE's works engine tuner

[gamma500]

Do you guys have info and photos of The Steadman special 750?

Another amazing kiwi built 2t special!

Link to article I found from the internet:

http://img5.imageshack.us/gal.php?g=7500001.jpg

Faster than the superbikes at Taupo!!

[TZ350]

EngMod2T

The model assumes the combustion process stays the same as long as the basic combustion chamber and process stays the same but has to be re calculated if the compression ratio, fuel or other details like piston dome, squish clearance or area are changed.

The "Turbulent" combustion calculation (takes a lot of time) only has to be done once, then the details are entered by hand once and the program run in "Prescribed" combustion mode (much faster) while changes to other items like pipe, ports and port timing can be explored without affecting the combustion model.

From EngMod2T's help file.

Turbulent eddies are created from the bulk flow of the fluid. Kinetic energy is taken from the bulk flow and transformed into turbulent energy (the spinning of the turbulent eddy). The size of these eddies are in part determined by the size of the container or duct and in our engines are typically between 5 and 20mm diameter depending on the cylinder and transfer port sizes. (This size is known as the integral length scale) These eddies break down into progressively smaller eddies down to eddies of about 0.5 to 1mm.

It is at this size that combustion takes place.
To decrease the delay time we need to increase the strength and duration of the spark to ignite as much of this first eddy as good possible. The size of this spark also needs to be at least the size of a turbulent eddy. Bigger does not really help because one or two eddies burning at the laminar rate has no real effect on the delay time. Increasing the spark strength and duration past the point where the eddy has been fully ignited will also have no or a very small effect. This partially explains why some engines show a performance improvement with a bigger gap - they have larger turbulent eddies.


To increase combustion rate we have to spin these eddies faster to come into contact with non burning eddies at a faster rate. This is why faster spinning eddies (higher turbulent intensity) results in a faster combustion. It also implies that combustion happens at a specific rate. Uncontrolled combustion is where these eddies ignite because of a sharp temperature and pressure rise. This is an uncontrolled event and if enough eddies ignite we have detonation which is definitely uncontrolled!


Prescribed burn rate. This model goes one step further in that the shape of the mass fraction burn rate is described by the user. Mass fraction burnt is usually a curve that is S-shaped. To descibe this the model uses typically a Sine function or a Wiebe (Vibe) function to describe the S-shape. The user supplies the constants that describe the form of this function. The user also supplies the ignition timing, the delay period length and the duration of the combustion. The chamber geometry is ignored.

Turbulent eddy entrainment. The turbulent intensity is calculated by the simulation and from this and the mixture purity and AFR, the laminar and turbulent burn rates are determined. This is then used to calculate the burn rate. The user supplies the ignition timing. The major characteristics of the chamber is included and squish action is calculated. Blending radiuses are ignored but dome shape and piston crown shape are used to calculate the flame front characteristics.

To read more, buy a copy of EngMod2T, its worth every penny.

These graphs are from my single exhaust port GP125 with a flat top pistion with 0.6mm squish and 7.6:1 corrected comp ratio. They will change if I change any of the combustion chamber details and have to be recalculated.

Ignition Delay ... VibeM ... Burn Duration in Degrees ... VibeA once calculated these numbers can be hand feed into EngMod2Ts simulation model to speed the calculating process up when simulating changes to pipes and ports.

[TZ350]

you should use the "Supplied" option in X/Y-axis limits (it's on the window for choosing perf. data) to limit the range and get even more accurate values.
A small trick I use is this: say I see the value of delay at 10500 is between 10 and 12. I limit the Y-axis between these two, and set the X-axis to start at 10500. It says the exact value right on the Y-axis scale.

I can't seem to make the "Supplied" X/Y option work.....



How accurate does one have to be? would line of best fit work here?

[wobbly]

I have some pics of Jimmys triple on an old hard drive somewhere, I will see if I can find them.
It was here for a while when I did the pipe/port/ignition specs for him.
Initially it used a special PVL setup I built.
Then a set of 3 poxy Oz built ignitions, but we just couldnt stop them from talking to each other.
Its as fast as hell, but even using the triple balance program from BSL days, it still vibrates your balls off after a few laps.
He is building a V6 now, with RS125 cylinders.

TeeZee, yes best fit curve is fine for combustion data, its the value trend that is important.
More especially when you are simply doing pipe performance tests, as the combustion characteristic will remain a constant.

I used Dynamation back when I did the specs for the MB100 and NoMates engine - EngMod 2T would now do a way better ( more detailed) job.
The data generated back then was accurate enough, but all credit to Mike and Nige for implementing the basic info into something that works.

[dinamik2t]

Now that we say about pipes.. what is your opinion on dual stage baffle cones?? What would be the limit to the angle of the steeper stage?

[F5 Dave]

Think we probably have some pics of the 750 earlier in the thread.

here's an early pic. Wood radiator didn't make the final cut.

[wobbly]

TeeZee, in your VibeM graphic, it doesnt need to start at 0 ( this is the default ).
The range in Y is 0.2 min to 1.2 max, put this in and it expands the Y axis within these limits.
Leave rpm ( X ) as is.
makes reading off the specific numbers much easier and accurate.

[husaberg]

I had a bit of a dig around on the net and came up with these I see what Wob was meaning when it came to the Chassis. A truly beautiful example of CNC.

[husaberg]

I had a bit of a dig around on the net and came up with these I see what Wob was meaning when it came to the Chassis. A truly beautiful example of CNC.

A few that wouldn't fit. Including the Britten maybe Wob would like to mention any inside detail he may know about it? The Supermono is there for no other reason than because it's pretty

Credit to most of the pic to this guy http://picasaweb.google.com/11482178...21351539510098

[speedpro]

Do you guys have info and photos of The Steadman special 750?

Another amazing kiwi built 2t special!

Link to article I found from the internet:

http://img5.imageshack.us/gal.php?g=7500001.jpg

Faster than the superbikes at Taupo!!

I have heaps of photos including of bits getting machined plus a video of when they first fired it up. It isn't bad considering it was pretty well all done in a double garage with a pretty basic lathe and mill. Nige made the pipes and as usual are a work of art.

[F5 Dave]

Well I’ve managed to engineer myself into a corner with SE bearings again. I have a 50.75 barrel I am running in the interim on my MB so I ordered a ye olde YZ100 piston to check out. Good luck finding online info on a ‘76 piston.

Arrived on my desk this morning so yet to check it at home.

Single 1mm ring that is pegged looking like far enough away from boostport not to have to move. Bit heavy as 3^rd oversize & suitable for single port only. But heck it will keep this interim cylinder working ok & is far & away better than the MB one.


Whoops, 16mm pin. 14 is std. rod is 19mm ID. Yams usually run thin SE bearings, but 16x20 is their size (same as RD250 apparently so don’t yell foul yet).

I forgot to order a pin, it was a mission enough to find rings & piston from same seller who would ship. But that should match up with something else easy enough or be shortened.

So can someone point me in the direction of a reasonable resource (can’t seem to find a decent site, maybe I should try PeteSalesbearingcatalogue.com?) for finding if a 16x19x## bearing is indeed made? 1.5mm rollers? Mammy!

[jasonu]

I had a bit of a dig around on the net and came up with these I see what Wob was meaning when it came to the Chassis. A truly beautiful example of CNC.

What is the bike in the background in the last pic?

[F5 Dave]

Last pic?, you'd have to be a forensic scientist to see that (or do you mean the reflection of the same bike?, heaps of mirrors in that show). I see both the Ally & Kevlar Roberts bikes in other pics though,.

[husaberg]

Last pic?, you'd have to be a forensic scientist to see that (or do you mean the reflection of the same bike?, heaps of mirrors in that show). I see both the Ally & Kevlar Roberts bikes in other pics though,.

My guess is jason means this one the Roberts one in the background of the first set of pics? he just confirmed this.

http://picasaweb.google.com/114821789113527181423/MotorcyclesUnleashed#5271322403647734418

[jasonu]

Last pic?, you'd have to be a forensic scientist to see that (or do you mean the reflection of the same bike?, heaps of mirrors in that show). I see both the Ally & Kevlar Roberts bikes in other pics though,.

Hus pm'd me the answer and another pic. I was looking at the Roberts bike. It looked familar but I wasn't sure. Still looks the business.