ESE's works engine tuner

[teriks]

Well we got all sorted to video this PJ problem and it had disapeared ... .

Not the pj-entry location then.
I was under the impression that you had modified the carb bell to shorten the inlet tract, seems I got that wrong also.

[TZ350]

Every idea was a good idea as it realy had me stumped and I needed all the help I could get, it was more by luck than good management that the glue sorted it out, but logical when you think about it.

[dinamik2t]

Glad you sorted it out TZ
Actually, PWKs have this seperate 'base' (obviously, since Oko copies them) and there is a band and an o-ring to seal the part.
Oko was just glued, eh?

By the way, your dyno result is impressive with a single ex! Congrats!

[Frits Overmars]

Actually, low pressure is what draws air -and so fuel- from a higher pressure area. Both main and powerjet draw fuel from the same bowl. And that fuel is drown by the same sub-atmospheric pressure of the crankcases.

Nope. It is drawn by the dynamic pressure at the fuel exit points in the carburetter. And that pressure depends on the mean air flow velocity along those exits.
Air flow velocity is at its highest in the center of the narrowest part of the inlet tract, so the location of the fuel exit will make a difference. And by mean air flow I mean (air flow into the engine + backflow)/2.
You see, more than enough variables; more than enough differences between the exit points of the fuel flow through the main jet and the flow through the power jet.

[2T Institute]

What's everyones thoughts on the tiny atomising bleed hole on the front side of Mikuni TZ power jet discharge tube?

[wobbly]

Re the tiny bleed hole in the TZ powerjet tube - I always thought that this was a good idea to emulsify the fuel as it exited the dropper.
But years ago i did some wet tests on the flowbench with a VCR video camera ( pretty trick shit stuff back then ).
The Mikuni was a horror scene when played back slo mo,with huge "gobbs" of fuel exiting the main and powerjet.
We then stuck on a Lectron - wow, lovely fine mist of fuel from the back of the flat needle face - and it flowed 12% more air - size for size with a venturi 2mm smaller behind the slide.

Next is the current state of TeeZees GP125, here is the latest dyno curve digitised with 16% added to simulate crank power.
Then there is the sim with an actual RS early model pipe.
Then there is the new pipe of my design.
Of most interest is that in this case the sim is giving slightly too much crank power - but the shape and peak point are all but perfect.
I would be confident now that any change in the sim, would be reflected in reality on the dyno.
In my experience the later Dynojets like a twin roller 168 with Eddy current load control to slow the acceleration rate down ,seem to read around 5 to 10% lower
so this would put the sim and the dyno reading very close, as the shape is spot on now.

[dinamik2t]

Nope. It is drawn by the dynamic pressure at the fuel exit points in the carburetter. And that pressure depends on the mean air flow velocity along those exits.
Air flow velocity is at its highest in the center of the narrowest part of the inlet tract, so the location of the fuel exit will make a difference. And by mean air flow I mean (air flow into the engine + backflow)/2.
You see, more than enough variables; more than enough differences between the exit points of the fuel flow through the main jet and the flow through the power jet.

Aha, I see. I think I got it now, Frits.
If the powerjet is positioned in the middle of the venturi or at a lower point, that will affect how much it will flow, correct?

I remember both Lectron and Mikuni aftermarket PJ kits' instructions, saying that the end tip of the pj should be around the middle of the carb.
Yet the Keihin PJ of the carbs for the mx250 models is down low! Position would also affect which fraction of the flow becomes more rich or not, or that doesn't matter??

[wobbly]

When using a simple powerjet nozzle the tip position matters in that no flow will occur until the slide is well past the exit hole, and there is sufficient airflow
to drag fuel up the feed tube above the bowl level.
With the aftermarket add ons and the ones as used by Lectron you can shorten the dump tube so that the flow will only occur at high slide openings,as well as high air flow.
These also have a built in "lag "control in that it takes time for the fuel to rise up the tube and dump out the exit into the air stream.
With a solenoid controlled setup all this is pretty much irrelevant as the flow can only occur when the solenoid is not powered up, and this
is TPS as well as rpm dependant inside the ECU program..
The carbs as used on the MX bikes has the dump tube very low in the bore as they added and subtracted fuel at low slide positions in those bikes.
For a race engine I bend the tube up to around 1/2 bore, as this is where the exit is on the Kehin SPJ carb for RS125/RS250 Honda.
And the general setting is the solenoid is powered up ie no flow below 4000 and 60% TPS and is powered up again at around 12400 to lean off the mixture and increase revon.
This causes a problem with Ignitechs that are used with only a capacitor, as at startup the solenoid is powered up, dragging all the voltage out of the ECU, so I convert the ECU output
to a 3 step truth table, and have the setting such that below 1500rpm the solenoid isnt powered.

[dinamik2t]

You mean something like this, eh?


As for the bending.. I rememder heating copper pipes in hydraulics and filling them with sand to bend them. I assume same would be applicable to brass, which is similar to copper, but would it be a good idea to fill the PJ's tube with sand??
I 'll check tomorrow and see whether the tubing can be removed from the carb body, to bend it with an actual tube bender.

Thanks for the explanations Wob!

[wobbly]

The tube is thick walled and bends easily by simply levering it up.
You can take it out, but then when its bent it wont go back in,as its designed to be pushed in from the outside.
Here is the table

[TZ350]

""Hi Tz350, I want to ask your help to test some expansion chamber design software...
So I got this software like the one mentioned on :
http://www.kiwibiker.co.nz/forums/sh...15#post1779915

I want to test the result on my engine spec but can't afford to build one this time..
So I've input your spec as in http://www.kiwibiker.co.nz/forums/sh...post1130226187 on this software, if you have any spare time, can you test it on your engmod2t?

1st one : I input with same bmep (about 37.2 @ 12500)



2nd : I input with higher bmep but lower rpm (about 37 @11500)



I guess engmod2t result could give an idea about what can we expect from this software..
thx in advance tz350.. ""

There you go ..... I hope the results encourage you to get a copy of the pipe software and your own copy of EngMod2T to continue the development of your GP125.

EngMod2T is not that expensive and as you can see, worth every penny as an evaluation tool. It can also warn you of potentialy dangerous thermal conditions if you look at some of the other graphs that it can display related to the combustion process.

[pugs]

There you go ..... I hope the results encourage you to get a copy of the pipe software and your own copy of EngMod2T to continue the development of your GP125.
EngMod2T is not that expensive and as you can see, worth every penny as an evaluation tool.

Wow, thank you so much Tz.., turn out this software worked pretty well..
Actually I already have this software, but it's just me that still confused, which one I will choose for my next pipe: this software or Frits's design.. (And now it made me confused even more.. x_x)

Another question, if you don't mind, will you share, what number (peak rpm & sound speed) that you inputed for Frits's design so it can achieve 43@13250? It's okay if you want to keep it for ese's team..
Oh.., surely Engmod2t will be the first on my wish list..

Question for Frits..
(sorry I hijack your thread tz.., but now, i just can't help myself..)
Frits, when I put bigger engine capacity (150cc) on your pipe formula, while other parameter stay still, dx number are getting much bigger.. (& since approx. power output doesn't included in dx equation, lower hp number would not change that...)

I always thought that same port area (engine breathing-capacity) will generate same achievable-power on the similar rpm.. Well, maybe less on the bigger capacity due to more reciprocating mass. Um..., is that the reason? I mean, is reciprocating-mass affecting rpm that much? (125cc @12000rpm dx = 150cc@10000rpm dx)
Or there's another explanation? Thank you for the enlightenment...

[TZ350]

Thanks, Mental; everything seems to be fine now. So here they are again:

http://www.kiwibiker.co.nz/manual/Aprilia-1.zip (6.8 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-2.zip (8.3 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-3.zip (9.2 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-4.zip (7.2 MB)
http://www.kiwibiker.co.nz/manual/Aprilia-5.zip (5.6 MB)

The pipe design I used in that simulation was the simpler one I found of Frits's on the Aprilia-3.zip file. I don't know the rpm and sound speed he used but the simulator liked it and it does look fairly easy to make.

Another question, if you don't mind, will you share, what number (peak rpm & sound speed) that you inputed for Frits's design so it can achieve 43@13250? It's okay if you want to keep it for ese's team...

There are no secrets at Team ESE, we post everything we do, its the fun of making friends, sharing ideas, riding bikes and building stuff we enjoy.

[speedpro]

There are no secrets at Team ESE, we post everything we do, its the fun of making friends and building stuff we enjoy.

I'm actually on my way there this morning to measure up a few things

[wobbly]

Just a couple of points re the pipe designs shown above.
The header length at 37% is just plain dumb and very wrong, never seen a pipe on any engine that worked with that %.It should be in the 31 to 33 range.
And running a 19mm stinger on any 125 that makes any power at all - IT WILL BLOW UP.
Also its very short sighted to take Frits pipe layout from a 125 GP rotary valve engine that makes over 50 Hp around 13000, and simply bung it onto an air cooled bucket engine
with a 24mm carb that needs a huge level of input to make 30 RWHp.
Aprilia made arm loads of test pipes to understand what worked on that engine,and for sure it wont work well on the GP125 bucket - its the design intent that is important, not the actual numbers.