ESE's works engine tuner

[TZ350]

Page 1670......

Chairs, the latest ones i see are are digital now though, so they will have a curve i hope.
They are still a neat little set up, and cheap as chips.
Attachment 328749Attachment 328750
Price:$299.00 + $4.49 shipping
https://www.amazon.com/DIGITAL-IGNIT.../dp/B00CFL5QLU

http://www.ktm-parts.com/mm5/graphic...XS12050039.pdf

For an idea just how big they are for those unfamilar with the little KTM's
Attachment 328751

Was thinking about this and wondered that, instead of having the two disc valve passages being coaxial or on a plane, have them enter the under cylinder volume semi tangentially.

A very good idea, I was thinking about that too..

The problem with grinding a cylinder is that the main exhaust will then not have the plating going around the corner from the bore into the port.

As the ring bulges outward, and the top/bottom port radi with a chamfer help to guide it back into the groove,eventually the plating will be worn thru to alloy - or chipped away.

You can smooth the edge with a cotton mop to help the situation, but for sure it will last long enough to test the porting results.

The transfers don’t give any problems, as they don’ need a chamfer at all.

As you have gone 1/2 way and put in the bore/duct radius you may as well go all the way and epoxy fill the B port front wall as Jan did as a successful test on the Aprilia.

I notice Yamaha regressed in that detail. Compared to the earlier reverse cylinder
https://www.kiwibiker.co.nz/forums/a...8&d=1481884812

The problem with grinding a cylinder is that the main exhaust will then not have the plating going around the corner from the bore into the port.

As the ring bulges outward,and the top/bottom port radi with a chamfer help to guide it back into the groove,eventually the plating will be worn thru to alloy - or chipped away.

You can smooth the edge with a cotton mop to help the situation,but for sure it will last long enough to test the porting results. The transfers dont give any problems, as they dont need a chamfer at all.

The transfers dont give any problems, as they dont need a chamfer at all.

Even if it's not needed to guide the rings back into place, isn't there still some benefit to airflow? I had always thought sharp edges were the enemy of good aerodynamics.

Jean or Frits indicates that the chamfered intake ports were harmful. It helps the exhaust gases to come in when the intake ports open.

Transfer ducts with what is called "exit " flow benefit far more from the sharp edges at the bore as the gas that forms the scavenging regime maintains a much better coherent stream.

With bore chamfers the column edges break up, and eddies or tiny turbulent swirls are formed that compromise the directional control.

Jan tested this at Aprilia, and i have done a direct back to back on a KZ10B, dynoing at 47.8 Hp with no chamfers, then immediately loosing near on 1 Hp everywhere after chamfering all the transfer ports - creating a ruined cylinder in about 10 minutes .

Wob, do you have any comment / recommendation on the height of the aux ex ports?

Re the height of the Aux ports.This is a simple case of swings and oundabouts - the higher you go the better the peak power ( more STA at opening ) but this comes at the expense of power at the low end, and in the overev ie it creates a narrower band of peakyer power.

So, to get the best of both, once the width has been maximized, and that seems to be limited to around to bore center,then the height is dictated by the power needed and the width of the powerband.

This is helped of course in the bottom by a PV, but the Aprilia had around 2mm of height difference on a 54.5 stroke,and thus was biased somewhat toward band width, allowing good overev capability.

KZ2 engines have no PV and need plenty of bottom and overev,but the width is nowhere near bore center ( no piston plugs ) but have around 1.5mm stagger, so i believe there is a lot to be gained in tests with plugs and much wider/lower Aux.

FCR carbs were designed for 4T, and the biggest issue on a 2T is that the slide is set at a 1.5,whereas a normal 2T Keihin would be a 5.

This gives very rich transition response,and cant be tuned out - but on Meth this may not matter. For simple gravity feed you need at least a 4.2 float jet,and I believe that Meth needles are available, but the tube is fixed,so will have to be drilled or be part of an alky kit to get sufficient flow at 1/4 to WOT with a thin point on the needle tip.

re the 75% cylinder exit area rule of thumb,this area is just a by product of the desire to reduce the volume of the whole exit duct.

The other guide is that this area is most effective if it occurs at around 1.5x the bore diameter,thus many cylinders are way too short.

I have added extra ,smaller area ,duct length to many cylinders, by extending the bolt on spigot plate, or making a female spigot on the cylinder into a male one.

Then the header that sits after the oval to round transition, starts at 2x bore.

Hi All,
Thought I’d drop by to share the findings of my YZ250 EFI project. It has a 2009 CRF450R 50mm throttle body, 3D printed polyurethane throttle boot to a Boyesen RAD valve. Fuel system is returnless with a Walbro GSL-414 pump controlled by a Madhu PWM pump controller/pressure sensor. Fuel filter is a Sytec mini bullet. Injector is the CRF450R 12 hole injector (440cc/min @ 4 bar). It’s controlled with a Microsquirt V3 running MSextra code, triggered by a 20-1 tooth wheel welded to the ignition rotor and a crank sensor from a YFM350.

It’s tuned in Alpha-N strategy (TPS vs. RPM table), with barometric pressure sensor and intake air temp sensor for compensation. It uses a Wideband O2 and logs either EGT or Fuel pressure.
First start was about a month ago, have put 3 tanks of fuel through it so far. Most of the tuning has been automatic based on AFR targets, except idle, light throttle and overrun where it needs to be tuned manually. 50mm throttle feels just as linear as the 38mm carb. I haven’t used any accel pump fuelling yet, so I’m hoping that will sharpen the throttle up a bit more.

Throttle transition at high rpm has been the main tuning issue. When closing and reopening the throttle, the motor would flood and not refire until the revs dropped, so I figured the airflow must drop off at some throttle value. I tried tuning a ledge into the fuel map, it was better than before but still hit and miss, fast roll on was ok, slow roll on or steady part throttle would still flood.
Then I figured that the airflow wasn't just related to the throttle, but when the engine is firing, the airflow is significantly higher than when it isn’t firing, due to the exhaust vacuum after blowdown pulling charge through the engine.
Therefore the fuel required for a cycle can be predicted by whether or not the engine fired on the previous cycle, in addition to engine speed and throttle position.
So my solution is to check whether the cylinder has fired, then adjust the fuel table for the next cycle. The throttle body MAP sensor is connected to the exhaust port and samples the pressure during blowdown. I’ve set up a 2nd fuel table in the ECU with a multiplier for when the pressure is above a threshold, corresponding to the cylinder firing. When the exhaust pressure is high, the main fuel table is unchanged, when low, it is reduced by 50% (will need to be dialled in for various RPM, but seems to work so far). The main fuel table is tuned with the wideband when the motor is firing, then extrapolated into the non-firing low throttle/overrun area. On closing the throttle, once the motor stops firing, fuel flow drops to match the airflow, so the motor doesn’t flood. On opening the throttle, the mixture is correct to initiate firing, then after the first fire fuel flow goes back to the main table value.

I think with some tuning I should be able to get the transition pretty much seamless. At the moment I'm working on getting the fuel table just right around the transition area, then I'll work on the switch threshold and multiplier values. That said, it's pretty decent already, but I'm a perfectionist.

Nathan

https://www.youtube.com/watch?v=4Zsz26QmfAU

Attachment 328790
Attachment 328789
Attachment 328791
Attachment 328792
Attachment 328793

Throttle transition at high rpm has been the main tuning issue. When closing and reopening the throttle, the motor would flood and not refire until the revs dropped, so I figured the airflow must drop off at some throttle value.

Then I figured that the airflow wasn't just related to the throttle, but when the engine is firing, the airflow is significantly higher than when it isn’t firing, due to the exhaust vacuum after blowdown pulling charge through the engine.

Great stuff, TeeZee will be very interested.

My thought too. Waiting for TeeZee now.

Yes, very interested. Thanks Nathan, for the great idea of using a MAP sensor to measure the pressure changes in the exhaust system so as to see the changes in bulk air flow through the engine, I wish I had thought of that ages ago.

Overun over fueling, Cagiva had the same issue. Yours is a bloody neat set up though.

https://www.kiwibiker.co.nz/forums/a...hmentid=301602
https://www.kiwibiker.co.nz/forums/a...hmentid=301601
https://www.kiwibiker.co.nz/forums/a...hmentid=301600
https://www.kiwibiker.co.nz/forums/a...hmentid=301599
https://www.kiwibiker.co.nz/forums/a...hmentid=301598
https://www.kiwibiker.co.nz/forums/a...hmentid=301597

The Cagiva used to keep pumping in fuel on over run, then bog with its rich mixture and then chime in with a potential highside causing burst, when the unburned fuel finally cleared out of the crankcase.
Pumper carbs can do the same thing, not an issue on karts as they tend to keep on the gas.
I think What you have done is you have compensated for lower airflow and incomplete combustion on over-run, which was creating a richer mixture in the crankcase, which is what a conventional vacuum metered carb does.

I found with my system it would never clear once it bogged, just 100% dead until the revs dropped. They must have been using some method of clearing it.
I guess that's why injected snowmobiles and boats don't have the issue, as soon as the throttle is cut the revs drop.
Nice article on the Cagiva too, I hadn't seen that one.

I found with my system it would never clear once it bogged, just 100% dead until the revs dropped.

Exactly my problem too.

Same problem everyone else, from Cagiva through to Suter last year at the IOM the longer time at full throttle the worse it will be.That overlay from the ECU on the video is uber cool

Measuring the blowdown pressure pulse rather than the negative (since they should be proportional) gives you a head start on getting the fuel in. I have the pressure sample window set to 140-170° ATDC. The peak moves with RPM, because of the delay along the hose to the MAP sensor, so best to keep it as short and close to the port opening as possible. I have the injection start 10° after the sample window, so the latest pressure value is used to calculate the injector pulsewidth.

I suspect the pulses develop to full strength over a few cycles, as the return wave strengthens the combustion, so probably no need to get all the fuel in on that first cycle after measurement.

I am measuring through the powervalve vent, so my pressure values are only indicative for firing or not. With a proper exhaust port measurement you could adjust fuelling based on the pressure rather than just firing/not-firing..

Not likely; the 125 cc KTM GP-bike already had an injector in the crankcase that injected through a port below the exhaust port.
They used it instead of a powerjet and it would only have been logical to use the same setup for full EFI.
Attachment 328804 Attachment 328805 Attachment 328806

Neels describes in "Using Post2T to investigate Detonation" TUBmax should be lower 950° for AV Gas.
Is there any temperatur recommendation for unleaded 95/100 Fuel?

Avgas,or any leaded hi octane race gas runs best with hi com and lean mixtures.

Pump gas or no lead gas makes better power when running richer, with less com and generally more advance.

But in some applications ( like KZ2 ) we need to run lean with pump gas to get pipe temp,its a trade off between outright peak Hp and rev ability.

So pump gas " can " use the same TuBmax numbers as Avgas in EngMod, it depends upon the end use and mechanical setup of the engine.

At max.torque rpm the transfer event is not even on full song by BDC; the transfer flow is still accelerating.
About 20° after BDC the crankcase pressure has dropped to atmospheric level; then it is time to connect the case to the outside world.
If you open the inlet earlier, you will lose case pressure. If you open it later, the case pressure will drop more than it would need to, slowing down the transfer flow.

There is a reason that the disk opened later on many rotary road bikes: if you let the case pressure drop lower before opening the disk, there will be a stronger suction signal to the carburetter, making carb. setting more responsive. But hey, you've got EFI.

[peewee]

The big square Aux port will not work well at all.
It will promote bad short circuiting from the A port, and this will also lower the header temp - then trying to lean it down will loose more power.
You have to re arrange the main Ex upper width,or increase the Aux top width to get back the STA without ruining the scavenging regime.
Also,you cannot know for sure that the "reverse stagger " will work in this engine,as the scavenging pattern is heavily dependent upon the B port duct
geometry.
Remember Jans B port duct in the Aprilia was very small in entry area, and you cannot just ignore this when trying to replicate his results.

ya i dont like the square aux either. with the teardrops you lose alittle area in the lower rear corner but gain some area in the upper rear, where its needed most. so the pressure drop can be faster through the first few initial degrees of opening, atleast that's what I think happens

[richban]

Hi Guys.


I did a quick thread search and could not find anything discussed on smartcarb. Anyone running one? I have had a little experience with Lectron and they seam really good. Is smartcarb as good?

[wobbly]

One other small point about the square Aux, is that this exposes a huge area enabling interconnection to the A port via the small end piston hole.
With a teardrop the port exposes less than 1/2 the area where the linking can occur, and separates them height wise.

[husaberg]

Hi Guys.


I did a quick thread search and could not find anything discussed on smartcarb. Anyone running one? I have had a little experience with Lectron and they seam really good. Is smartcarb as good?

https://www.kiwibiker.co.nz/forums/s...post1130842057
https://www.kiwibiker.co.nz/forums/s...post1130255542
https://www.kiwibiker.co.nz/forums/s...post1130812466
https://www.kiwibiker.co.nz/forums/s...post1130437168
there is more but KB search is not working properly maybe due to the thread being split a few times. poll etc

[richban]

https://www.kiwibiker.co.nz/forums/s...post1130842057
https://www.kiwibiker.co.nz/forums/s...post1130255542
https://www.kiwibiker.co.nz/forums/s...post1130812466
https://www.kiwibiker.co.nz/forums/s...post1130437168
there is more but KB search is not working properly maybe due to the thread being split a few times. poll etc

Thank you kind sir. Very Keen on a smart carb for the 50.

[bjorn.clauw.1]

https://www.kiwibiker.co.nz/forums/s...post1130842057
https://www.kiwibiker.co.nz/forums/s...post1130255542
https://www.kiwibiker.co.nz/forums/s...post1130812466
https://www.kiwibiker.co.nz/forums/s...post1130437168
there is more but KB search is not working properly maybe due to the thread being split a few times. poll etc

google search just for this thread:
https://cse.google.com/cse/publicurl...90:5pd9xdluxce

only downside is that the google indexing robot passes by every 5 days, so the last 5 to 10 pages are not included.

[husaberg]

google search just for this thread:
https://cse.google.com/cse/publicurl...90:5pd9xdluxce

only downside is that the google indexing robot passes by every 5 days, so the last 5 to 10 pages are not included.

I ended up doing that, but the thread search is generally very good, as long as you use the advanced option and seach for posts, but not so much lately.

[F5 Dave]

I've only ridden one bike with a smartcarb. About 2 weeks back. Ran nice. But I know a lot of people on gg forum that were ccustom sanding the needles. Seemed supercritical, not as they set out one needle fits all. I question how they would wear.
Heavy to hold.

[41juergen]

The big square Aux port will not work well at all.
It will promote bad short circuiting from the A port, and this will also lower the header temp - then trying to lean it down will loose more power.
You have to re arrange the main Ex upper width,or increase the Aux top width to get back the STA without ruining the scavenging regime.
Also,you cannot know for sure that the "reverse stagger " will work in this engine,as the scavenging pattern is heavily dependent upon the B port duct
geometry.
Remember Jans B port duct in the Aprilia was very small in entry area, and you cannot just ignore this when trying to replicate his results.

Thank's for the feedback Wob and PeeWee. As the rear of the aux port is already at the bore centerline I need to give up a bit of the (theoretical) blow down. Re the short circuiting I will use a piston plug, but that will not really solve the problem, right? So I will follow the tear drop shape...
Re the stagger: the Yam cylinder has indeed a different transfer entry as Jan's RSA cylinders. I thought with the 3 ex port design the reverse stagger would be the way to go. Also the Yam engineers had the idea to let the A port going flat into the cylinder were the B port has a 15° upward angle. Need to think about to fill up the A port top with JBweld...

[jamathi]

Thank's for the feedback Wob and PeeWee. As the rear of the aux port is already at the bore centerline I need to give up a bit of the (theoretical) blow down. Re the short circuiting I will use a piston plug, but that will not really solve the problem, right? So I will follow the tear drop shape...
Re the stagger: the Yam cylinder has indeed a different transfer entry as Jan's RSA cylinders. I thought with the 3 ex port design the reverse stagger would be the way to go. Also the Yam engineers had the idea to let the A port going flat into the cylinder were the B port has a 15° upward angle. Need to think about to fill up the A port top with JBweld...

We used piston plug AND teardrop shape!
And with a triple port the A-port must be lower to reduce short circuiting with the aux-ports.
The Yam engineer's ideas seem VERY outdated.
Later they copied Honda 100%, and even published an SAE paper about that......were proud of it.....
They even didn't do the copying themselves, Yamaha-France's famous head mechanic Guy Coulon did it for them.

Our A-port was at least 25° inclined upwards, maybe a bit more.....
When I reduced the B-duct entry the reverse stagger was already there.

[Frits Overmars]

Alcohol fuels do not loose power when running rich, and being rich allows way higher com without deto. But this scenario also lowers the pipe temp, due to excess unburnt fuel in the header.

True, an overly rich mixture will yield a low exhaust gas temperature. But even with a correct mixture strength such an engine will loose revs because a high compression ratio doubles as a high expansion ratio, dropping the EGT even before the exhaust port opens.

The Yam engineer's ideas seem VERY outdated. Later they copied Honda 100%, and even published an SAE paper about that... were proud of it...
They even didn't do the copying themselves, Yamaha-France's famous head mechanic Guy Coulon did it for them.

And let's not forget Harald Bartol. Our beloved friend Cees van Dongen showed the way by putting a Honda RS125 cylinder on his son's Yamaha TZ125, and Bartol first copied Van Dongen's idea and subsequently developed 'special' cylinders, financed by Yamaha. I hear that Yamaha were not amused when it became clear that their money had been used to carbon-copy Honda cylinders.

[jonny quest]

41j you seem to have room to bring the aux exhaust ports closer to main exhaust, instead of just making them wider outwards.

The bridged exhausts like Honda 125's, open up to wristpin. Has Honda ever used closed wristpins? Any time I've tried widening a bridged exhaust on a dirt bike into wristpin area it ruined the power. Couldn't get it to work.

[jonny quest]

Forgot to mention I've had really good luck widening bridged exhaust port next to transfers. This goes against the RSA results... but has always worked for me on bridged ports

[190mech]

Very late reply!Husa asked in Nov 15,2011(page 360) if anyone tested the ignition curve from a KTM 50SX iggy,well I did today,,planning to use it on a one off Minarelli scooter engine,so I built a test rig.Sorry to say its a "flat liner",no curve at all!Back to the drawing board...