ESE's works engine tuner

[dinamik2t]

I don't know either why pick-up voltage would be required.
Perhaps it has something to do with the amperage limit of the output wire?

[TZ350]

I was just watching a video of Kaitoki. Good fun.

We will be back .....

[TZ350]

Taper Bored 24mm OKO, its 24mm at the very front, 29mm at the slide and 31mm at the manifold end.



In the middle picture you can clearly see the air correction jet, its just a drilling in the carb body. It was about 0.8mm and I have opened it to 1.45 but after reading Riches post I will try bigger.



Posted because someone asked me where the Power Jet is positioned on my carb.



My plan is to use an electric air solenoid (purchased from JayCar) to bleed air into the powerjet to interrupt its function below 7,000 rpm or so.

[husaberg]

Taper Bored 24mm OKO, its 24mm at the very front, 29mm at the slide and 31mm at the manifold end.



In the middle picture you can clearly see the air correction jet, its just a drilling in the carb body. It was about 0.8mm and I have opened it to 1.45 but after reading Riches post I will try bigger.

Posted because someone asked me where the Power Jet is positioned on my carb.

My plan is to use an electric air solenoid to bleed air into the powerjet to interrupt its function below 7,000 rpm or so.

I will try to keep this post small i will trim it down a bit later and put it more in an order etc.

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.

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??

Attachment 255006

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.

Attachment 254941

Made an adjustable PJ out of a model aero engine carb needle jet for controlling the PJ. Now to get one of those solenoids the Husaburg posted to shut off the PJ for a bit of extra over rev.

Made some progress with the shorter inlet tract and expect to get the lower mid range back again with a bit of fiddling with the carburation.

Just a little bit more and the single exhaust port engine with the RS pipe will be very close to EngMod2T's predicted power output.

Attachment 254940 125cc rotary valve with a 24mm carb and air cooled.

Measured 31 rwhp (estimated 34 crank hp) on the dyno tonight, red line is last night before the inlet tract was shortened and the jetting/ignition adjusted.

I have ordered one of Wobblys special kitset "A" Kit Pipes for a Suzuki GP125 ..... so hopefully 1 or 2 more hp and a wider spread of power. Then there is the ATAC idea for better low end.

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.

You have to be very carefull with the switch point and the run time on the dyno.
The switch point is dead critical to 100rpm,so i always set it too high initially and make sure that the dyno is loading the acceleration rate to be as close to that on track as you can.
This gives the pipe time to heat up and affect the power over the top, as it would in reality.
On a RS250 dropping the switch point from 12800 ( std) to 12400 gives easily another 800 rpm of virtually no power drop past peak.
On the track,if the rider can feel the switch point ( it feels like hooking another gear)the jet is too big,when its right it should be seamless and just keep reving out.
Leaded fuel is the opposite to unleaded, in that as leaded likes to run lean - you can only use a small powerjet and thus only switch off a small amount.
A leaded engine works best with around 35 to 38 PJ, the unleaded fuel can switch a 60, in Keihin numbering, as the crap fuel makes best power at peak when quite rich..

And something that I scraped from the net.........

""The solenoid control on TZ type powerjets really just shuts off fuel flow to the powerjets right at the top of the rev range to lean the mixture off to increase the over-rev once you are past peak power.

I don't have the solenoids plugged in currently though as I find they work well enough for my current needs with the powerjets simply responding to venturi vacuum pressure in pretty much the same way as the oem 3MA powerjets work.""

Attachment 233787Attachment 233788

And here is a picture of the carbs and what I can make out, a dyno graph without, and with the power jet solenoids shutting off (red line) and extending the over rev.

So it looks like you can use an electric power jet like a standard one and when the carburation is sorted, try switching it of by activating the solenoid at or just after peak power and see what happens with the over rev.

The FPE superkart engine that won the NZ road title at Manfield a few weeks ago makes 92 RWHp on the Dynojet 168 I use.
Still not quite as good as the RS250 setup we did that won at Laguna Superkart Worlds a couple of years ago.

The powerjet carb is controlled by the Ignitech with a combination of throttle position and rpm in a "truth table".
In general the solenoid is activated with 12V ( no fuel flowing) below 4000 rpm and 75% throttle on the TPS.
Above 75% and around 12400 rpm it is activated again to lean off the fuel curve over the top of the pipe.
Looks like you will be able to reverse the fuel exit, blocking off the hole on the throttle bore side, and take off fuel from the outside bung, thru a needle jet and into the top of the venturi next to the slide.

Recently I got myself (Ebay) a 38mm carb with Throttle PS and Electric PJ from a motor crosser.

Wobbly told me that on those the PJ nozzel is to low and starts to flow to soon for a road racer and the MX ones are hard to tune.

Attachment 230481

I couldn't afford to buy a good second hand TZ or RS unit. So I figure that moving the discharge nozzel.

Attachment 230483

And adding an adjustable jet from a large model aero engine could be worth a try.

Attachment 230482

On the dyno I have seen how a leaner mixture rev's on further and how richining it up for best power the over rev drops off.

I think that as the rpm goes up the mixture strength on an ordanery carb at max rpm goes over rich.

And at the moment I think the idea is that the PV is shutoff after peak power to get back to the correct mixture and by retarding the ignition at the same time extend the over rev, but I am sure there is more to it.

I would love to know more about how this type of carb should be used and/or setup.

The modern take on powerjets is to turn them off after peak power to extend the rev range. This assumes that you are happy for your engine to rev that much further past peak power & on many buckets perhaps this is not so good unless you have uprated the crank assembly. The jet will start to flow, depending on its position. Some don't seem to work well without an airbox if they aren't very prominant, or perhaps if the suction isn't so much (putting big carb on a smaller cylinder). In some cases they are best blocked off presumably if the air jet doesn't match very well & is tending to increasing richening with airflow as it is.

With all the talk about wanting to utilize only a couple of gear changes per lap, I would have thought that the solenoid powerjet was a gift from heaven.
A late model well tuned RS125 will rev to around 12400 if the PJ is disabled,turn the PJ function back on and it will go to 13800+.
Its so simple and you retain exactly the same lower rev power,but with easily another 1000rpm to work with you have the choice of adding teeth on the back, getting better acceleration from torque multiplication, or keeping the same gears - but increasing the terminal speed.
And from the dyno curves I have seen, most of the 100 buckets with short stroke lengths, arent even beginning to stress the bottom ends - with less peak rpm than the 54.5mm stroke 125 bikes or karts that will easily run to 13000 all day.

Some more RSA125 development info from Jan Thiel

"No pressure transducers were ever used in our engine development.
And time/aerea was never calculated.
The port timings remained practically the same during 15 years!
What we did was trying different angles and radiuses, mainly on
the transfer ducts. I think we tried 40 different types of transfer ducts
that did not chanche the time/aerea. It was all about in which direction
the charge entered the cilinder and how the tranfer streams influenced upon
each other! Also about 200 different exhaust pipes were tried. After 2004
nothing much was changed but we improved with different power jet and
ignition mapping. It seemed nearly impossible to improve the transfer ducts
any more. The exhaust ducts were CNC machined, using different programs,
mainly to reduce exhaust duct volume. Also about 100 head designs were tried"

Didnt calculate time area? Im guessing that means the time area requirement hasnt changed any in the last 15+ years.
So there you go its all about the transfer ducts, now where have I heard that before?
Check out the attached photos, I guess the idea of thinning the transfer duct bridge has gone out the window, and the exhaust duct hows that for a crazy shape


Attachment 231454
Attachment 231455
Attachment 231456

Recently I got myself (Ebay) a 38mm carb with Throttle PS and Electric PJ from a motor crosser.

Wobbly told me that on those the PJ nozzel is to low and starts to flow to soon for a road racer and the MX ones are hard to tune.

Attachment 230481

I couldn't afford to buy a good second hand TZ or RS unit. So I figure that moving the discharge nozzel.

Attachment 230483

And adding an adjustable jet from a large model aero engine could be worth a try.

Attachment 230482

On the dyno I have seen how a leaner mixture rev's on further and how richining it up for best power the over rev drops off.

I think that as the rpm goes up the mixture strength on an ordanery carb at max rpm goes over rich.

And at the moment I think the idea is that the PV is shutoff after peak power to get back to the correct mixture and by retarding the ignition at the same time extend the over rev, but I am sure there is more to it.

I would love to know more about how this type of carb should be used and/or setup.

Ok now we have a stepper motor controled power jet........

The 'high compression brickwall' is no longer as hard as it used to be. With leaded fuel the compression ratio was 19,5; nowadays it is about 15. The 'brickwall' arose from the high expansion ratio (which is identical to the compression ratio). The higher this ratio, the more the burnt gases in the cylinder cool down before they enter the exhaust, thus lowering the resonance frequency of the exhaust system.
Riders complained that the engine would not rev, especially not in the lower gears, where the revs rose so quickly that the rising wall temperature of the exhaust pipes could not keep up with them. So you had cold exhaust gas and cold pipes.

The problem was to a large extent solved when the solenoid-controlled on/off-power jets were replaced with stepper motor-controlled jets that could continuously adjust mixture strenght, allowing the engine to rev more freely.

Attachment 229455

This is it. The stepper motor itself originates from a Fiat Uno where it regulates the idling rpm

Regarding the Aprilia RSW/RSA125 single, Jan Thiel told me that in seven years of testing the racing department had not been able to establish which was best: low or high inertia. I would choose low.....

Frits Overmars

[husaberg]

I am a bit stuck with the timings as I cut the secondry exhaust ports a bit big. It was my first effort and more about seeing if it could actually be done.

At 116 the front transfers come very close to the underside of the side exhaust ports so I cant move any more there and the rear transfers need to open a little later than the fronts, so its all a bit compromised really.

I originaly wanted to make a broad spread of power but have allowed myself to get distracted by the side show of building a racing Bucket engine that reliably makes over 30hp and my tripple port is aimed at that.

Attachment 262591 Attachment 262592

50hp 125 Aprilia racing engine.

Side Ex boost ports are the way to go to get the blow down STA needed to make real power and to allow a smaller width main exhaust port for piston/ring reliability.



In all fairness, there are other people in the Tuning Industry that have their own ideas about the worth of Ex boost ports for racing .....

Attachment 262570 Attachment 262571

I think they are the Bizz but don't like wasting good cylinders on experiments, so I used an old damaged cylinder to see if it was actually possible to cut these side ports, turned out OK but not to sure about racing reliability. Although the main exhaust port is not as big as the 31hp cylinder that failed at Kaitoke so that must help.

Should be interesting on the dyno ....... and if its any good then we will see if it holds together on the track.

Found these other pics of the Aprilia on the thread EX ports.

Some more RSA125 development info from Jan Thiel

"No pressure transducers were ever used in our engine development.
And time/aerea was never calculated.
The port timings remained practically the same during 15 years!
What we did was trying different angles and radiuses, mainly on
the transfer ducts. I think we tried 40 different types of transfer ducts
that did not chanche the time/aerea. It was all about in which direction
the charge entered the cilinder and how the tranfer streams influenced upon
each other! Also about 200 different exhaust pipes were tried. After 2004
nothing much was changed but we improved with different power jet and
ignition mapping. It seemed nearly impossible to improve the transfer ducts
any more. The exhaust ducts were CNC machined, using different programs,
mainly to reduce exhaust duct volume. Also about 100 head designs were tried"

Didnt calculate time area? Im guessing that means the time area requirement hasnt changed any in the last 15+ years.
So there you go its all about the transfer ducts, now where have I heard that before?
Check out the attached photos, I guess the idea of thinning the transfer duct bridge has gone out the window, and the exhaust duct hows that for a crazy shape


Attachment 231454
Attachment 231455
Attachment 231456

AND a Honda EX

No not planning anything too radical.

Attachment 228854Attachment 228855

Wobbly was just explaining to me the lengths the rotary valve boys are going too, to compete with the reed valvers and how it might be hard to get a big enough inlet port on our GP's with their smallish side rotary valves.

Attachment 228856

Yum yum stuff........ head inserts and an electric power jet carb with a throttle position sensor.
Attachment 228857

Real transfer ports ..........

[SwePatrick]

I´m having a wonder here..

Why not restrict the airflow where there´s no fuel blended in into the airmass.
Then you can choose an.. say 36mm carb and build a big plenum on the carb with an perfect lavalnozzle at 24mm?

Take a look at Formula 3 cars.
They have an HUGE plenum with a tiny restrictor, inside the plenum theres an long diverging kone to stack upp the air again.

Or are you restricted by rules that carb MUST be 24mm?

pics:




By looking at your modded Koso carb i think it might be worth a test, but it might be a problematic one to jet correct.
(A cone like this you lathed is to be at 7degrees+-1.)
Why jettingproblems?
because you got the highest airspeed at the very front of the carb, not at the point where you want it,, at the venturi where the needle is located.
You just might 'choke' the airflow at the front of carb.

Rgds
Patrick

[TZ350]

Interesting pictures and ideas, maybe the thing would be to use your idea and direct injection into the cylinder like Orbital does ...

Or are you restricted by rules that carb MUST be 24mm?

Yes my carb must be 24mm.



The other restrictions are, what we can achieve with Mr Rattly, the old lathe



and basic hand tools.

[wobbly]

I would lift the main port to 80* then lift the B & C ports to around 114.5 or so.
You have the perfect tool to see if the STAs are in the ballpark - run it thru EngMod and see what happens.
Means you have a setup that mirrors the Aprilia design philosophy.

[TZ350]

My sensor has a PN 0-261-231-001, what's yours?
According to this http://www.phormula.co.uk/KnockCalculator.aspx , deto freq for 56mm bore should be 10.2kHz.

BOSCH p/n 0 261 231 046



Other sensors can be found here too. http://www.bosch.com.au/content/language1/html/4563.htm

[husaberg]

I´m having a wonder here..

Why not restrict the airflow where there´s no fuel blended in into the airmass.
Then you can choose an.. say 36mm carb and build a big plenum on the carb with an perfect lavalnozzle at 24mm?


because you got the highest airspeed at the very front of the carb, not at the point where you want it,, at the venturi where the needle is located.
You just might 'choke' the airflow at the front of carb.

Rgds
Patrick

Frits has mentioned this at some stage. The idea being only the airflow was restricted before the additional mass of the fuel mixed in with it if i recall correctly.

Found it thread tools rock. I knew Frits would have a picture.

Attachment 256967

This is what my ventori tube looks like, flow is from left to right, two ramps, leading ramp is 34 deg included and trailing ramp is 14 deg included angle.

Could the flow be improved by making the leading edge ramp into an aero foil shape like the leading edge of an aeroplane wing as in your picture.

It would certainly shorten up the tube and get the venturi point closer in behind the slide.

Yes, make it into a bellmouth. That will get you both a shorter unit and a better inflow. You might also consider putting the restriction in the bellmouth if your rules allow it. That would mean you can have a considerably longer trailing ramp (the widening can start right after the bellmouth, i.e. under the throttle slide). It also means that only the air, not the fuel, has to pass through the restriction. That way the total mass that has to be accelerated through the restriction, will be about 8 % less.

Still a good idea though.

[bucketracer]

Taper Bored 24mm OKO, its 24mm at the very front, 29mm at the slide and 31mm at the manifold end.

TeeZees carb has the 24mm restriction ahead of the slide so only air passes through it and I think he was actually testing it before Frits suggested it. But in reality on TeeZees engine there is a fare bit of fog when its making max power so its probably a moot point. This is the carb he used on his 31rwhp setup.

The answer to the, three times past the main jet fog at max power question suggested by Frits, was that the fog may indicate the inlet stream is bouncing off the closing disk and that it may be possible to shut the inlet a little later.

[F5 Dave]

ok, a question for the panel;
Small end bearing axial (to piston) clearance; How much is too much? Obviously if the bearing can travel far enough so the rollers touch the edge of the rod they will grab on the sharp end & lock immediately causing mondo destruction. I found this out the hard way running RD50 pistons in my MB50 20 years ago, they needed thrust washers in that application.


The MB pistons (in the 50 as the 100, which is what I'm now talking about, the 100) are bevelled at the piston pin bosses. They leave a scant .4mm clearance at the top & ~4mm at the bottom, which is obviously nice for lubrication. Yamaha KT pistons are straight edged at the bosses.

The OEM stuff I have measured for small pistons seems to run 1mm clearance, so .5 per side. 250cc cylinders run up to almost 2mm it seems.

So I'm left with the suitability question over 17mm wide MB SE bearing in a Yam piston with 19.2mm between the bosses, so 2.2mm clearance. With a wider rod it should not make it out of the small end.

I'm not overly happy with the 2.5mm rollers (making for a 14x19 bearing) that only has 11 rollers, but they seem to go ok in std bikes. Most of the 18x14 brgs seem to run 12 rollers.

[wobbly]

I had a quick look at the 3Ex GP125 in Engmod.
Lifting the main Ex to 80* needs to have the B,C transfers lifted to 113.8* to get the STA near balanced again.
It will then have staggered Ex plus reverse staggered transfers,Mr Thiel would be proud.

[TZ350]

I had a quick look at the 3Ex GP125 in Engmod.
Lifting the main Ex to 80* needs to have the B,C transfers lifted to 113.8* to get the STA near balanced again.
It will then have staggered Ex plus reverse staggered transfers,Mr Thiel would be proud.

That looks good Wob, it will take me a few nights next week to get it sorted then we can give it a spin up.

[TZ350]

I was recently asked about servos for the Ignitec and if I thought a Radio Control servo could be used for the exhaust power valve.

Well I don't think so, or at least not easily or without a bit of work, and they are only 3 to 5V or so too.

My understanding is that a normal power valve servo is a motor and feedback potentiometer. And how it works is that the Ignitec is shown where the fully open and fully closed points are, ie 100% travel. Then the Ignitec can position the power valve anywhere from 0% closed to 100% open using the feed back potentiometer.

A RC servo works the same internally but is controlled by a variable input frequency transmitted from the pilots radio hand set. As the pilot wiggles a knob the frequency of that knobs channel changes a little bit and that tells a little chip inside the RC servo the changes to make.



RC Servo



An RC Servo Tester mimicks the pilots handset, you turn the knob on the tester to vary the frequency being sent to the RC servo and hence its position.



The change in frequency is interpreted by the chip inside the RC servo.

And the chip positions the servo motor using an internal feedback potentiometer just like the Ignitec does with a power valve servo.



I was able to use a RC servo to open/close the Vtec Valve by using two RC Servo testers, one set to open, the other to closed and a Relay that the Ignitec activated when it was time to open the Vtec.

It may be possible to cut into a RC servo and bypass its internal electronics and modify it to work like a normal power valve servo.

This link may show more: http://www.societyofrobots.com/actuators_servos.shtml

If anyone manages to modify a high torque RC servo to work as an ordinary power valve servo, it would be great to have the details posted here.