ESE's works engine tuner

[TZ350]

Simultaed Crank hp, it may be overstated by about 4-5 hp, but its the relative differences that are important as you can expect them to show up the same way in the engine.



Red line is the Plenum and it adds a boost in the 12-14K area, the Blue is a Boost Bottle and Orange is the 24mm OKO.

I have been playing around with the simulator again and have been able to simulate a boost bottle and plenum (air box) similar to the plenum we made a while back.

I am not sure if EngMod2T can do both airbox and boost bottle together, hopefully there is a way. Anyway plenty to tryout on the dyno after the last round of the Pacific Clubs Summer series at Kaitoke over Easter.

The Plenum giving a boost in the 12-14K area is just what I would expect if the 24mm carb was limiting the top end power output.

Now that we look like we are getting to the end of what a conventional 24mm carb can pass the plenum might usefully add something, anyway EngMod2T thinks so, so we are just going to have to try it out again.

[2T Institute]

What piston? Comp height? Did you get much benefit from the 110mm rod (air cooled RD 250/250 rods are a better rod BTW). Did you use a spacer plate with the 110mm rod?

[dmcca]

Tz, now that we're talking about your moto, please remind me: how much difference was there from reducing the duct entry to about 1.2xport ?

I'm interested in dyno proof of this too... Tried it on several bikes and my bum tells me it's a good thing but I can't seem to get engmod to show much if any difference.

[dinamik2t]

Yes, I was curious about that, because the sim shows some difference, but not much.
Also, I am very curious whether I am measuring the duct enty area correctly - or at the correct point. I have found area ratios close to 1.5 for tfrs and 2.5-3 for boost ports in a few cylinders Seems pretty large.
All of these cylinders have the sleeve side of the duct at the same level as the outer/flange side. I just lay a milimetric paper on it, shape the edges and count squares...
In addition to that, 125mx/gp ducts look so big! Makes me wonder.

[TZ350]

Did you use a spacer plate with the 110mm rod?

Yes used 10-12mm spacer, depending on the rod piston combo.



At first it was just an alloy plate then Thomas suggested putting the spacer to use as cooling too. The black piece in the picture is a heat insulator.



So the spacer now adds volume, stops a lot of cylinder heat getting to the crankcases and directly cools the exhaust port area through contact with the copper bars.



Multi tasking cylinder spacer.

[wobbly]

What you have to realise is that because EngMod is a 1D simulation it cannot predict changes is flow regimes due to duct geometry.
Making the entry area 1.2 instead of 1.5 will change the volume, and this is what the sim "sees" but this change will dramatically affect the flow thru the duct into the port.
Its the same with say port stagger,this dramatically affects the scavenging regime, all the sim sees is the high ports affect on blowdown and calculates this change.
What you have to do is look at what is being done in the fastest engines on the planet and translate that experience to the project at hand.
This is why the sim is overpredicting the power of the GP125, it knows nothing about the duct shortcomings, even though the numbers may be similar to a RSA.
Neels hates fudge factors, but what we need to pull the power down,is a factor that represents a " % of shit design " that we cant modify out of our projects.

[sonic_v]

What you have to realise is that because EngMod is a 1D simulation it cannot predict changes is flow regimes due to duct geometry.
Making the entry area 1.2 instead of 1.5 will change the volume, and this is what the sim "sees" but this change will dramatically affect the flow thru the duct into the port.

The transfer ducts are modelled exactly the same as the exhaust system hence in effect the ducts can behave like diffusers when the cylinder pressure is above the crankcase pressure ( This is rarely good for power as it increases backflow into transfer duct). Hence a 1.5 area ratio is a steep angled diffuser and a 1.2 area ratio is a shallow angle diffuser and thus the code is doing more that just a volume change.

However, the code knows nothing about the finer details such as inner and outer radius of duct etc.

Sometimes going down to a ratio of 1.05 or even 1.0 can be good from a simulation point of view.

[TZ350]

The interest at the moment is modelling a boost bottle and plenum.



Here is a bit of info on Boost Bottles.



Engine http://wikiscootia.wikidot.com/boost-bottle#toc1

Theory http://www.mopedarmy.com/forums/read.php?1,843707



How to calculate the Sizes required. http://49ccscoot.com/boost.html

And making your own is not that hard.

[wobbly]

Yes I agree the sim calculates the transfer duct as a tapered pipe taken from the dimensions given, from this it calculates the volume.
And yes I also agree that it cannot know if it is ( although it must assume that it is ) a constant taper.
The less the real duct conforms to this ideal, the less accurate the sim is in its calculations in relation to the real diffuser.
Neels visits here sometimes - maybe he could enlighten us if any calculations are done for reverse flow down the duct, when blowdown overcomes case pressure, and the transfer duct actually acts as a diffuser and not a contraction.

TeeZee, Neels has sent us both the latest version to install.
Resend the packed sim when you have this done - and I will report if it crashes.

A boost bottle setup helps throttle response when getting back on the gas, after coasting into a corner at low rpm.
Could be usefull on a sprint track.
The ATAC boosts the whole bottom end, off the pipe, and works much more effectively due to the greater wave intensity in the header.

[husaberg]

The interest at the moment is modelling a boost bottle and plenum.


Here is a bit of info on Boost Bottles.

And making your own is not that hard.

My thoughts based on gut instinct is the boost bottle would be quite beneficial esp with the restricted size carb.
I hazard a guess that it would be more beneficial than the original plenum certainly it should be a lot less problematic with the fueling.

What about a convoluted tube so you can alter the length/volume during testing quickly?


Or an air bladder mounted in the reservoir internally to tune the volume much like a pressure tank TZ will be well familiar with,
which could even be pulsed to alter the volume or even absorb/reflect pressure waves. just spit balling on the last bit.
If you have seen an home made water ram made with a old bike tube inserted you will have an idea what i mean.

[TZ350]

I will get that sim update sorted.

A boost bottle setup helps throttle response when getting back on the gas, after coasting into a corner at low rpm. Could be usefull on a sprint track.

This would have been usefull at Te Puke.

The ATAC boosts the whole bottom end, off the pipe, and works much more effectively due to the greater wave intensity in the header.

An ATAC valve is very much on my to do list.

[TZ350]

Interesting, whatever way you cut it, most of the votes are going to two strokes, could this be another sign of where things are going at the pointy end of Moto4 (affectionately known as Buckets).

[F5 Dave]

My thoughts based on gut instinct is the boost bottle would be quite beneficial esp with the restricted size carb.
I hazard a guess that it would be more beneficial than the original plenum certainly it should be a lot less problematic with the fueling.

What about a convoluted tube so you can alter the length/volume during testing quickly?


Or an air bladder mounted in the reservoir internally to tune the volume much like a pressure tank TZ will be well familiar with,
which could even be pulsed to alter the volume or even absorb/reflect pressure waves. just spit balling on the last bit.
If you have seen an home made water ram made with a old bike tube inserted you will have an idea what i mean.

BTW intake pressure will suck flat anything that isn't pretty rigid. Although Suzuki have got away with using just hose on the RG150, but it is rigid wrt to its dia.

[husaberg]

BTW intake pressure will suck flat anything that isn't pretty rigid. Although Suzuki have got away with using just hose on the RG150, but it is rigid wrt to its dia.

Yeah it could the only way to be sure is to suck and see. Admittedly i posted the pic wasn't great example of what i was meaning (i was in a hurry.)
I do believe it will be a bit more rigid then you think though.remember (vacuum cleaners) They have amazing strength in regards to crush from their shape and material concentration.
Hence its uses on some automotive intakes. From memory some FWD cars and even karts also have sturdy steel convoluted tubes as well on exhausts.

[TZ350]

EngMod2T



Red line boost bottle as close to the Rotary Valve as I can get it and Blue line BB mid way between RV and Carb Slide, all other conditions the same. The stuff you can easily find out in half an hour using the EngMod simulator.

That would have taken me several nights on the dyno to find out?