Ecotrons Engine Management

[TZ350]

Page 4 .....

7,250rpm

7,500rpm

8,250rpm

[TZ350]

Page 5 ...

9,250rpm

11,000rpm

11,750rpm

[TZ350]

Page 6 ...

13,000rpm

With these simulated charts and my known good number 65 from the old map cell corresponding to 100% TP at 9,250 I can generate new numbers for each cell for my new map.

9,250rpm

I know 65 from 100% TP and 9,250rpm on my old map was a good number and from the simulations I that 65 relates to a transfer ratio of 1.3 or in other words 1.3 times the cylinder volume was transferred up to the cylinder and it took 65 on the old map for the EFI to squirt enough fuel into the engine at that point for good power.

So now I have to normalise the simulated numbers so I can use them to estimate from the known good number 65 what each new value should be for every cell position on the map.

So we know for 9,250rpm and 100% TP 1.3 transfer ratio = 65

So for cell position 9,250rpm and 87% TP = 1.244/1.3 * 65 = 62.2

So for cell 9,250 rpm 87% TP the new value is 62.2

Now I only have to do this calculation for 190 more cells and I will have my new map, how hard can that be .....

[speedpro]

Simple in XL

[TZ350]

Simple in XL

Yes, and that is the next step. I will post it when I get it done.

[AndreasL]

Love it TZ! 👍

[Cheesy]

Is your injector dead time going to throw this calculation out at lower engine speeds if you are pushing the range on the injector?

[TZ350]

Is your injector dead time going to throw this calculation out at lower engine speeds if you are pushing the range on the injector?

I am not sure. There is a minimum on time of 1.8ms to get these injectors fully open. so any injection event has to be for more than 1.8ms otherwise the engine over fuels.

You might only need 0.001cc per injection.

A bigger injector can deliver 0.001cc in 0.9ms but there is a minimum on time of 1.8ms so the bigger injector delivers twice as much fuel as needed and can not be turned down any lower than 1.8ms.

A smaller injector might deliver 0.001cc in 2ms, so a smaller injector can be turned down to deliver the right amount of fuel.

The trick is to use a smaller injector so it squirts less fuel and so needs to be turned on for longer that way you get finer low speed fueling control.



I am using three injectors in a staged setup. The inner one does the low speed work. Then it changes to the outer two who do all the work from about 7K to 10K rpm at which point the first joins them again and helps out when the complete 360 deg crank rotation time starts to shrink and squeeze the possible injection on time.



I have had some successes with full throttle runs

[mr bucketracer]

I am not sure. There is a minimum on time of 1.8ms to get these injectors fully open. so any injection event has to be for more than 1.8ms otherwise the engine over fuels.

You might only need 0.001cc per injection.

A bigger injector can deliver 0.001cc in 0.9ms but there is a minimum on time of 1.8ms so the bigger injector delivers twice as much fuel as needed and can not be turned down any lower than 1.8ms.

A smaller injector might deliver 0.001cc in 2ms, so a smaller injector can be turned down to deliver the right amount of fuel.

The trick is to use a smaller injector so it squirts less fuel and so needs to be turned on for longer that way you get finer low speed fueling control.



I am using three injectors in a staged setup. The inner one does the low speed work. Then it changes to the outer two who do all the work from about 7K to 10K rpm at which point the first joins them again and helps out when the complete 360 deg crank rotation time starts to shrink and squeeze the possible injection on time.



I have had some successes with full throttle runs

she's looking good now

[TZ350]

Simple in XL

WorkFile Map 39A 16-03-16 RAM_MAP_LdTp_Tps_N.xls



Job done, now to see if it actually works.

[TZ350]

The EFI story with pictures if you follow the links back to the original posts.

Posted because someone asked where to find it all, so a recap on the basics of the Beasts Engine.

TeeZee tested his 24 against a 30 in a back to back test. The 30 didn't make anymore power than the 24.

Ok, making a bit of progress with setting up the EFI systems throttle body.

Det Sensor. Next week I hope to get all the chopping and changing of the wiring done then I can start playing with setting up the Ecotrons EFI program for a trial run...

The mid chamber bleed re visited as it might be useful for some low end boost......

One of the most useful things I have added to the fuel injection system is a switch that turns the fuel pump off.

Tim gave me a hand tonight, we started to make progress when we moved the injection end point. I think we originally had the injector squirting into closed ports.

Flettner makes the point that it is important, in fact the whole key to successfully fuel injecting a two stroke, is to have the injection period timed to end at the transfer port closing.

First cut at verifying the timing of the injection end point.
Lashed a regular trigger coil to a 12V solenoid with a bolt through it. Set the Ignitec map to zero, now it will fire immediately it sees a trigger pulse.

Spent sometime tonight trying to figure out why there was no signal at the injector. Then realized that at TPS = zero the injection map is = to zero. So bumped the first line up to 100 and bingo the injectors were firing.

The next move is to try the lash up Flettner suggested, and yes I still had sparks and by switching the leads plugged into the injector socket I could easily figure out which was the injector energizing and shut off points. And now I can setup the injector close point and with the timing light I can clearly see where the injection events are happening on the flywheel.

Ok ..... I dusted off my old valve powered signal generator and oscilloscope. And brought some science to the problem, and it looks like it is not me.

Later realised it was me, I did not have the steps in the map as even as they needed to be in real life and when the ECU tried changing between injectors with the engine under load it was tripping over a step and becoming confused.

Connected up a signal generator and oscilloscope to the Beast and had a look at how the EFI injector pulses behaved at a simulated 2,000 to 12,500+ rpm. And then with the motor running. Five things I learned about my EFI setup today.

Ok finally got the O2 and exhaust temperature sensors installed. No idea if they are in the optimum place but they will do for a start. Now that it all seems to be working I am really looking forward to getting a bit of time on the dyno to play with this thing.

I am now starting to make some headway with tuning the Beast and I am beginning to enjoy using the Ecotrons small engine EFI kit for two strokes and its 2T tuning software. Recorded some RPM and TPS data along with the Lambda O2 sensor.

Ok, making progress, that's if you can call getting it wrong progress. Ecotrons has a very clever self tuning feature where you tell the map what Lambda you want at what RPM and the ECU will read the ALM O2 sensor and adjust the mixture for you. Being able to make planned mistakes is a step better than just making ignorant mistakes and not knowing why. So .... its progress.

Posted because I was recently asked about the det sensor I used. I earthed one of the two wires. Probably does not matter which.

The detector/amplifier I got of Ebay comes with lights and I currently use an optional extra output to signal the ignition to retard when there is detonation.

Started making a new injector manifold that points the small Ecotrons injectors across the transfer port windows, previously the outside pair had just fired straight into the B transfer ports and impinged on the back of the cylinder liner.

Making some progress with the new fuel injection manifold. The injectors are angled so they squirt more horizontally across the transfer port. The small (bottom left) injector from the Ecotrons Small Engine EFI kit for two strokes has had the clips on its top cut back so the fuel barb can be swiveled in different directions.

Unlike finicky carburetors, with fuel injection there is not the over enriching problems you get when the inlet stream bounces back and forth several times in the inlet tract. Passing the carbs needle jet several times and picking up fuel on each pass. With EFI I don't have to be so conservative with the rotary valve timing and can experiment a little.

New injector manifold to direct the fuel streams across the transfer ducts. There will be three 126 g/min injectors, with the middle one firing first then the outer ones come in when the engine gets up on the pipe. The center injector is angled up so as to cool the underside of the piston crown by squirting through a slot in the piston skirt.

The plenum re visited ... The problem was, with the carb on the outside we got excessive fuel dropout in the plenum, EFI should cure that.

Started work on the fueling map, things are starting to come together, but probably making adjustments in to big a steps. More patience is required. When I shut the throttle after a 12k pull the motor sounded like a hive of angry hornets, to lean on over run.

The big learn of the night was the truth of the quote below.

"" One thing you have to always remember with alpha-N is that you don't actually know where the effective WOT is any more (i.e., when you have enough throttle that opening it further doesn't affect the amount of air being ingested). At low RPM WOT could be only 20% throttle. ""

Ok this is where my thinking is at tonight, possibly wrong but there you are. So I am none to sure about how useful the BSFC would be as it looks more rpm and engine efficiency than load dependent.

But what interests me is the Delivery Ratio as I think this is the total volume of air that is passing through the motor and as we all know fuel and air needs to be mixed at a set ratio, even if some of it gets wasted out the exhaust.

I knew the VE table was all about cylinder filling and I thought the cell values on an Alpha-N table were all about the volume of fuel to squirt but I have had to re-think that. From the Ecotrons manual. LOAD based Alpha-N system. For two-stroke engines, the default fuel mapping is Alpha-N method.

For my bike, at 12k ish the delivery ratio is about 120% of the cylinder volume and the amount of air (charging ratio) in the cylinder at BDC is only about 80% of the delivered air and less than that actually gets trapped (trapping efficiency) at exhaust port closing, so you can see that a fair swag of air is lost out the exhaust port. And my guess is that the bulk of the air that is lost is the first air entering the cylinder as the transfers start to open and if there was extra fuel already in the transfers that would be lost with it.

Now the opening time can start before the transfer opens and the close time after so that leaves me a clear 1.5 to 1.7ms of full on injection time. The start point can be early but it looks as if the timing of the injection end point is going to become critical if we are going to get the bulk of the injection happening towards the end of the transfer event.

That is pretty much what I have been trying to achieve with the upwards directed injection stream from the central injector.

If a carburettor has one advantage over fuel injection, this is it. When the quantity of fuel is controlled via the open/shut time of an injector, it is practically impossible to create a homogeneous mixture at the injector. And I'm not even talking about vaporized fuel here; I'm just talking about every part of air getting the same number of fuel droplets. Fortunately for us much of the necessary homogenisation takes place in a two-stroke's crankcase, with the con rod stirring things up and transferring its heat to the yet-unvaporized fuel droplets. But with direct fuel injection you lose this advantage, and the con rod bearing looses most of its cooling.

Hi Speedpro, I agree with everything you say but "weak mixture - no", well not in this case because this engine runs well with a carb but not with transfer port injection EFI so the problem must be with the EFI or at least with the way I am trying to use it.

Remember with a carb all inducted air has fuel mixed with it but with EFI this is not necessarily true. The problem with EFI and transfer port injection is that as the rpm gets up, a lot of air can get through the port but there is not necessarily enough time to inject sufficient fuel into the air stream.

Making progress, touching 12,000 rpm and nearly 25hp 3 to go.

26 hp and repeatable, but so fiddly to get and still detos like mad, however much fuel I throw at it. All the extra fuel does is make more exhaust smoke.
I think there really is just not enough time, 1.8ms for the injection cycle through the transfers at 12krpm. Ok time to change over to injecting down the inlet tract.

Ok, rearranged the injectors, injector one is still in the rear of the cylinder and injector two is firing down the carb. With the injection cycle timed to end at inlet closing. Red line is both injectors in the rear of the cylinder. Blue line is with the second injector in the inlet tract. The lines diverge at the point the inlet injector takes over. Its interesting because it goes to show that carbs can be pretty good.

The Blue line is my best with transfer port injection the Green line is where I have got to today with the twin injectors aimed down the inlet throat. It was the same map as the transfer port injection, and better than yesterday's single injector effort.

Well tonight's effort was a total bust, the two injectors send out such a cloud that it wets out on the bellmouth and dribbles down into the plenum which totally negates the reason for having injectors in the first place. Ie to stop fuel pooling in the plenum.

I can see the advantage of having the injectors behind the throttle slide like they have on the BRC engine. Gave up for the night after the EFI filled the crankcase with raw fuel.

Alpha-N maps need to be smooth without any peaks or severe troughs between cell steps. Ecotrons has a function where you can export a map to an Excel spread sheet and use the charting function to help smooth the map data. Raw data and the chart showing how rough the data is and the engine ran just as roughly. Smoothed data and chart.

Making progress towards the magic 28, at least now I know this EFI thing is going to work. Just a lot of careful step by step adjustment of the maps is required. I expect time and patience will see it running very nicely. I also thought it had a terminal deto problem. Deto turned out to be the piston hitting the head.

27.6hp - getting close with EFI to the best ever achieved with a carb on this cylinder. Blue line is where we started, Red line is where we are now. The big issue is getting back on the gas and running to rich below 8,000 rpm. Anyway it is coming right bit by bit.

The EFI is touching 28, but its still very reluctant to come back on the throttle after rolling off.

It will be a pig to ride so I guess I will take my laptop to Tammers and the weekend for me will be all about starting off the back of the grid and adjusting the EFI map to try and get the Beast track ride-able.

I am looking forward to it as I might have more luck getting it right by riding it than trying to tune its low to mid range on the dyno. Anyway the weekend away camping with every one else will be fun and the local RSA does a real great Saturday night dinner ..... Yum ...

Tammers was a bust, Bike was a real pig to ride.

Ok after months in the wilderness I finally figured it out. I was right about needing smaller injectors. So it looks like, to maximize tune-ability you need to minimize the injector size......... in hindsight its so obvious really .... Not perfect yet but very very promising.

With a smaller primary injector things start to come right.

Injectors turned up from Ecotrons today, four days from date of order and two of them were weekend days, pretty good service in my books. I fitted a smaller injector and did a bunch of runs at different throttle settings. Interesting that the 60, 50 and 40% runs carry on out to close to 13,000 rpm. Blue line is the TPS. 100-90-80-70-60-50-40% throttle settings. It is certainly throttling and coming back onto the power much better. I will have to analyse the data to see if I can use an even smaller injector.

The EFI lesson I learnt last month was, that to get the greatest range of tune ability I needed to use the smallest injectors possible that will still do the job. I know, pretty obvious, but there you go.

I read the Ecotrons EFI manual and saw that the map must have as many even steps as possible and I thought that meant dividing the rpm range up as evenly as possible, seemed logical, but wrong again.

The bike bucked around swapping between the staged injectors as the EFI struggled to jump from one cell to another on the steeper parts of the fueling curve.

I guess what they really meant was that the changes between cells need to be as even as possible.

So I don't need even spacing between the rpm break points and can have big or small gaps between them so long as there are no big steps between the values of adjacent cells.

I can now throttle on/off pretty well and do a series of part throttle runs, the last one is at 30% TPS, it looks a bit lean.

Its not perfect but is running a lot better, so for what its worth here is the current Alpha-N map.

Carburetors are great because of their analog ability to change the fuel delivery with changes in air flow at the same throttle setting. EFI, well EFI is not forgiving at all.

The Ecotrons Alpha-N map has 16 rows to work with and I had concentrated them in the area where the power is, as you do. Well that turns out to be a mistake because there is not much difference in fuel demand per cycle between 100% throttle and 90 or 80 or even 70 at max power and virtual no difference at all above 40% in the 3 to 6000 rpm range.

The big jumps were between the lower throttle settings where there was not much excitement happening, well the mistake is that the CPU has a hard time bridging the big gaps below 40% especially when it is also trying to swap between low and high injectors at the same time.

As it turns out, it was a mistake to concentrate my map in the power area, but I guess I will forgive myself.....

29hp

Different problem, but I feel your pain Dave. Been working my arse off on this EFI thing. 90% throttle consistently makes more power than a 100%, 80's pretty close to and 70 is not far behind.

Attachment 309768

I keep making more power but can't get it to come back onto the throttle properly.

I just want it to throttle properly so I can ride it , Bah humbug, and stamp my feet.

Finally getting some place with the EFI after strapping a small laptop onto the tank and riding the bike around looking for the bad spots in the map. I can now wind it out, throttle off and have it come back onto the throttle again. Its now ride-able enough to make it worth taking to a practice day for further refinement. Dyno runs recorded at 100-90-80-70-60-50-40 and 30% throttle.

I have made more power in the past but the point of these dyno runs is that it is running reasonably well at different throttle openings and it is also something of a guide for refining the Alpha-N map some more.

Its a two stage injector system with three injectors, the middle 60 g/min unit is for starting, slow running and over run after shutting off. A pair of 80 g/min units provide fuel as the engine comes on the pipe then the middle injector chimes in again so all three are firing as the rev's get around 10,000 rpm.

I checked the data logger and the middle injector is chiming back in at 9,500 rpm on WOT so I have achieved one of may aims, squirting raw fuel at the underside of the piston crown to cool it when the engine is making real power, I am very happy with that.

The biggest issue was selecting the right sized injectors, I had chosen ones that were to big, to big and there is not enough range of tuning adjustment and it took a while to work my way down to quite small injectors.

The quest for even steps on the Alpha-N map.

Now that my new bike is nearly ready I need to develop a new Alpha-N fuel injection map. The axis's of an Alpha-N map is throttle position TPS and RPM. The steps between cells need to be in even steps. That is not even RPM or TPS steps but even changes in engine load.

"Torque" is largely related to the motors Trapping Efficiency of the air passing through it.

"Delivery Ratio" is everything when it comes to quantifying airflow through a two stroke motor and it is the air flow that needs fuel added to it in the correct proportions. Trapping Efficiency is the measure of how much of this air/fuel is trapped to be com-busted.

Initially I thought changes in Torque could be used to represent changes in engine load and could be used for developing a fuel injection map. Well that might be Ok for a four stroke but now that I have tried that approach I now think that Delivery Ratio is the more suitable measure for developing a two stroke map.

Air flow (Delivery Ratio) through a throttle is not linear. The greatest changes happen between 20 - 40% throttle opening.

Attachment 320573

The first requirement is to find the throttle openings that corresponds to even Delivery Ratio (air flow) steps.

Attachment 320572

Then I modeled these throttle openings in EngMod2T and got a reasonable correlation and reasonably even layer of Transfer Efficiency steps in the power region of the simulation.

This information at each TPS position and RPM point should make a handy start for developing the new map.

The rest of the simulation data (all 12 of them) are posted on the Ecotrons thread. Because the Transfer Efficiency graphs are probably similar to any performance 2T with a few adjustments to the rpm points the numbers may make a useful start to any 2T Alpha-N map project.



Now to map it all out.



WorkFile Map 39A 16-03-16 RAM_MAP_LdTp_Tps_N.xls



Job done, now to see if it actually works.

Attachment 320844

Well.

The good news is that after months of work I have finally given Mr.Bigglesworth a thrashing on the dyno.

The bad news is that there is still a reluctance to come back on the throttle.

Attachment 320845

Fortunately the Ecotrons EFI software has a data capture function. Max power was at 12250 rpm and max over rev rpm was 12888.

Attachment 320846

Looking at the left hand courser the yellow line is Inj0 (the small injector) and the blue line Inj1 (the big injector) and the brown line is maximum injection time available. It can be seen that both injectors are topped out at 10,325 rpm. This suggests that Inj1 (the big injector) is to small.

Attachment 320847

With high rpm and the TPS at 0% Inj0's pulse width is 1.140ms (right hand courser) which is less than the allowable minimum opening time of 1.8ms so on over run Inj0 is still to big.

So the big injector is a touch to small and the small injector is still to big for good tun-ability when throttling off and opening the throttle again like you would negotiating a corner at speed.

Ok, so off to Ecotrons to buy some more injectors.

Attachment 320857

A fuel injector has a tuning range just like this jet kit has. And just like when you get down to the smallest jet in the kit and still need to go leaner you need a smaller jet kit or injector to move to the next lower tuning range.

That is my problem with the small injector, it is just not small enough to give me the tuning range required to handle the minimum fueling requirements on high rpm over run on a closed throttle. I need the next smaller injector.

Well it is not the end of the story but at least it is progress.

[TZ350]

Some helpful input from Dmcca and Wob on how to use a wideband O2 Lambda sensor to tune a 2T.

The Ecotrons EFI has barometric and air temperature sensors for automatic fueling compensation so hopefully once I am on the money with the dyno the ECU's auto compensation will give pretty much the same results as changing the jets 3 times a day.

I feel very comfortable with tuning the EFI system for maximum power, above 50% throttle position that is relatively easy.

The problem I am struggling with is at the low end, if this was a carb then the EFI bit that is challenging me now is the area covered by a carb's pilot jet and transition to the slide cutaway.

May I ask why you're not using a wideband O2 to tune this area? It would be relatively straightforward with a wideband and a brake dyno.

I started out trying to get a 12.5:1 A/F everywhere on the map, as you do if you don't know any better. Things weren't going well and I gave it away when it was pointed out to me that it was the short circuiting fooling the O2 sensor into thinking the system was running lean when it was not.

It really confused things and it looked like the O2 sensor was not going to be very useful so I discarded it. But your experience encourages me and it looks like that with a bit more experience myself I might be able to get somewhere with it now I have a better idea of what is going on.

Why a brake dyno? Then you would be developing an engine for a set of circumstances that it will never see on a race track. Going through the revs on an inertia dyno and registering revs, torque and lambda simultaneously is an excellent way of establishing an injection map. Besides, running constant revs on a brake dyno with too little fuel or too much ignition advance may kill your engine, whereas it might survive on an inertia dyno.

When i say brake dyno i mean an eddy current or similar that allows both constant rpm tests and normal 'runs'... Im sure that doing only constant rpm tests is not ideal.

Personally I do a combination of both to tune an engine and so far it has worked well for me, especially when tuning the low throttle area that TZ was talking about... in saying that ive only ever had an eddy current dyno, never an inertia-only dyno. And have developed my own methods of tuning without ever seeing first-hand anyone else's process for tuning a two stroke... maybe its a case of ignorance is bliss, however I find my process to be very quick and very reliable for a wide range of engines.

I find that the lambda sensor is a little slow to react at low revs and part throttle. Its fine at higher revs and higher throttle. By holding the engine at a certain rpm point for 3-5sec at each throttle position it gives the readings time to stabilise and gives much better, more repeatable data.

I start by doing a range of fixed rpm tests at different throttle openings, with the revs building higher each test... eg 4000, 6000, 8000, etc at 1/8, 1/4, 1/2, 3/4, full throttle. By doing this you can easily see the areas that need changing (pilot, slide, needle diameter, clip position, needle taper, main jet, etc).

If there is a serious problem with the tune you will always catch it before doing damage as you’ll see AFR's begin to lean out or detonation begin to show before you get too high in rpm. Once I’ve done basic tuning like this then i do full runs and constant load testing and fine tune if necessary, but these are normally only very minor changes.

Whether the AFR reading is showing true AFR or not doesn’t really matter, the numbers can still be used to tune an engine... around full throttle and peak torque it is fairly reliable to use ~12.5:1 and leaner readings below that, down to around 13.5-14:1 at part throttle/low rpm.

Of course you still need to use experience and 'feel' to do the fine tuning but the AFR numbers will get you close. Even if the engine is not actually seeing 14:1 at part throttle/low revs, its still a repeatable data point that can be used to tune an engine. Its certainly a lot better than guessing, especially when tuning the part throttle areas.

+1 the above.Adding that putting the Lambda in the stinger, seems to be way more stable and repeatable when logging the A/F data.

Using data this way is something that you really don’t appreciate how good it is until actually doing it.
Hence TeeZees surprise when I related that every time you change a small item in the engines tune - the dyno result for sure is not telling you really what you want to know, unless you reject every time to hit a predetermined baseline.

As Jan Thiel said, most all of the pipe testing at Aprilia was a complete waste of time, when he finally realised allot of the power differences were down to how the egt reacted to that pipe.

Not that the pipe was "better " for some aspect of scavenging, or trapping efficiency in making more or less power.

[TZ350]

Thanks Husaburg for the Cagiva story, its the same problem I am having.



Shaving down the rich areas on the map. I use Excels formula and graphing functions.



By having a mirror map below that is made up of formula that shaves 0.005 of the top map I can repeatedly transfer values from the bottom map to the top one and by that way shave the Fuel map down in the areas I think are too rich.



I use Excels graphing function to smooth out the lines of the map and to also get nice even steps between the lines.



Great surface visualization feature too.

[TZ350]

Rob, is it time to do a total fundamental reality check? Could it mean taking off all the injectors and chuck on a carb? Means getting rid of the neat throttle valve, but maybe you need to understand if it's some form of injector peculiarity or some unique characteristic of the engine as it has been built.

Have been hoping to avoid reality, this engine has run very well in the past with a carb. But its looking like you are right, it is shaping up to be something about the injectors. Maybe they need to be angled differently.

If the main problem with the carb setup was the fuel and oil that eventually may not reach the engine, maybe, is possible to build the chamber only upside of the inlet pipe, so the gravity kept fuel and oil always on the inlet. May be quite a bit of work and possibly more work/benefit than with the EFI setup, though...

Yes, good idea, we had thought of it but like you say, hard to do on the rotary valve engine but could be very possible to arrange the plenum in such a way it drains into the inlet on a reed or piston porter.

Rob - I'd try the low speed injector on the downstream side of the throttle valve - and aimed at a port wall. From what i've read on 4T injection in low airspeed conditions, you get better results if the injector stream can be made to splatter - for want of a better word...

Good idea, thanks, I might need to look at how I could do that.

Initially it looked like it was anything less than 20% throttle (left cursor) was the problem. But after a bit of time studying the recorded data it is beginning to look more complex.



As the rpm picks up (top line) you can see the rough running smooths out (right cursor) as the difference between injector on time (green line) and the total injector on time available (red line) reduces to 30%. 30% is about the amount of time the transfers are open.

To my surprise the engine runs rat shit when the injector on time is much less than the transfer open time and it gets better when the injector is on for longer than the transfers are open and best when the injector is on the whole time. Actually I suppose that should not be such a surprise because a carb is on for the whole time too, and they run Ok.

After looking at quite a lot of data it looks like the engine runs rough when the injector on time is less than the total transfer open time. The engine runs better the longer the injector is turned on. And of course anything less than 20% throttle there is not much injector on time and the thing runs like a pig.

It must have to do with fuel homogenization. A carb adds fuel to all of the air that passes through it but with an injector, under 30% on time I must be getting big patches of air with no fuel in it. And when the injector has to be on for much longer the air is getting a more consistent mix that is more like that delivered by a carb.

On over rev with the throttle shut there is very little injector on time. So because I can't fire the injector for the full transfer open time. I guess the trick is to find a way to thoroughly homogenize the air fuel mix or at least time the injection point to coincide with the air that will eventually be trapped in the cylinder.



Up till now I have had the big injectors on either side with the slow speed injector in the middle. Maybe worth my while reversing that and trying two small slow speed injectors either side with a really big power injector in the middle. If that results in better mixing and works well then as an extra up side I would be also getting lots of underside piston cooling from the power injector.


The big question is, is how to get a homogeneous mixture of the correct air fuel ratio in the cylinder when the injector is only on for a much shorter time than the transfer window is open.

[TZ350]

Thanks Husaburg for the Cagiva story, its the same problem I am having.

Mr Bigglesworth's Dyno runs.



.... rich areas ....

Initially I thought these were rich areas and to get it running nicely all I had to do was carefully adjust the map in these areas. But I now think the problem is with the injection on time being much less than the transfer port window open time.