ESE's works engine tuner

[Frits Overmars]

I have a copy of the old British Standards somewhere and now you mention it, I recall early mechanical fuel injection manifolds had a thin slide throttle plate.

Attachment 298121Attachment 298122

The drawing on the right contains a written warning: it was designed by the Prince of Darkness .

[Frits Overmars]

It looks to me that the 24mm restrictor on the RV inlet will mean sweet FA because you have other injectors that feed into the transfer ducts that are not restricted in any way.

Well, as long as these injectors don't inject air... I haven't got the bucket rulebook at hand but I imagine it stipulates (because that is how my rulebook describes it) that all oxygen used for combustion must come from ambient air and all this air must pass through restriction(s) with a total area equivalent to a 24 mm orifice.
Now if you would use the Orbital injection system, whereby fuel is pushed into the combustion chamber by means of pressurized air, that would be a different kettle of fish. My rulebook specifically allows the Orbital system because I want to promote fuel injection. Some smartass may start using a huge blower 'for this purpose' but we'll deal with that when it happens.

[Frits Overmars]

But I want a short 38mm intake.

You can have both. You don't need to put the restrictor in the disk valve cover; you can use the plenum entrance for that, as Husabergs sketch shows.

I would machine a 24mm restrictor, totally smooth with no throttle piston at all, best air flow and absolutly legal! You might want to add some more volume up where the old aircleaner fitted, more volume is better.

Way to go!

[TZ350]

OK had a play with the EFI on the dyno tonight. Sort of went OK, got the lower end to 8,000 rpm working OK but the old problems at the cross over point are back. At least now I know not to worry and with a bit of patience I will get it sorted.

The real problem is, is that I have no idea what the numbers mean or what a Alpha-N map for a 2T should look like and what worked before does not work now that I have a more symmetrical triple injector setup that points in the right directions.

performance curves from an old Bridgestone motorcycle

I have been modeling my Alpha-N or TPS/RPM based map on the torque curve so it got richer as the torque and rpm increased. But the break specific fuel consumption drops off, so I am a bit confused.

http://www3.telus.net/CarTunes/home/fuel injection operation.htm

""It is clear to see where peak torque is on the engine from the injection map, the large bump on the fuel map is at 6500RPM this is where cylinder filling is best and therefore is the point of maximum fuelling and maximum torque.""

More info on setting up an actual MegaSquirt system here:- http://www.extraefi.co.uk/MAP_Alpha_N.htm

"" One thing you have to always remember with alpha-N is that you don't actually know where the effective WOT is anymore (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. ""

Hopefully get another crack at it tomorrow night.

[ken seeber]

Frrits, good to see you encouraging DI for 2 strokes

At Orbital, we initially started with a 3 cyl 1.2 litre engine and this first used a 30 cc compressor, but later went to a 36 cc, more for reasons of emissions rather than power chasing, these being of 2.5 & 3% of engine displacement. In this case, the compressor drew its air via the engine intake system.

When we did the 50 cc scooters, we used an eccentric on a crank wheel, essentially the full diameter of the wheel. This drove a small direct acting compressor piston (using a small roller against the eccentric) with a spring return. The piston was dia 25 mm * 5 mm stroke (well, pretty close to this...memory loss occurring here) equating to say 2.5 cc, around 5 %. In this case, the air for the compressor was ingested from the inside the crankcase, which was handy as, being oiled air, it both lubricated the compressor (and its bearing), plus the detergents in the oil assisted in keeping the injector clean.

Frits, you mention your rulebook. Is this the Freetech 50 regulations? I have looked and have been waiting for these to come out in English, but when translating, it doesn't seem to include the Unlimited class rules.

Thanks

Ken

[husaberg]

Well, as long as these injectors don't inject air... I haven't got the bucket rulebook at hand but I imagine it stipulates (because that is how my rulebook describes it) that all oxygen used for combustion must come from ambient air and all this air must pass through restriction(s) with a total area equivalent to a 24 mm orifice.
Now if you would use the Orbital injection system, whereby fuel is pushed into the combustion chamber by means of pressurized air, that would be a different kettle of fish. My rulebook specifically allows the Orbital system because I want to promote fuel injection. Some smartass may start using a huge blower 'for this purpose' but we'll deal with that when it happens.

The MNZ rules are pretty ambiguous

F4 2 stroke engines over 104cc are restricted to carburation equivalent to a single 24mm carburettor,

You can have both. You don't need to put the restrictor in the disk valve cover; you can use the plenum entrance for that, as Husabergs sketch shows.Way to go!

It was robs sketch from nearly 900 pages ago,
I am a bit confused so is the restrictor better at the air entry to the engine or at the plenum/air box entry. Frits?
I seem to remember Leon Moss selling spacers for some filters as part of the Ledar kits as the intakes were to short and the solid backed foam filters being allegedly esp problematic...
So I wonder if Robs Plenum based on a std GP outer case will suffer from having the solid wall to close to the intake, could this have contributed to the fuel drop out he suffered previously..........
What ever Rob does I think maybe some of that Russian rocket paint (ok house paint LOL) might be a good idea for the inside to stop the heat transfer from the cases to the intake............

The insulating capacity of this stuff is simply amazing !
The factory claims 1mm of paint equals 50mm of glasswool.
I did tests with a aluminium plate half covered with the coating on the coocking plate.
While the uncoated side is hot enough to bake an egg ,you can touch the coated side by hand !

And yes I am expecting commission from Martijn

[Frits Overmars]

Frits, you mention your rulebook. Is this the Freetech 50 regulations? I have looked and have been waiting for these to come out in English, but when translating, it doesn't seem to include the Unlimited class rules.

Ken, I was referring to the rulebook for dutch mopedracing (www.sobw.nl). Freetech50 is just what it says; neither the limited nor the unlimited Freetech50 classes have any limit on carburation.
The Freetech rulebook contains a part dedicated to the limited class and a common part. There are no specific rules for the unlimited class; if you wish to build a 50 cc engine with four cylinders and fourteen speeds, be our guest!
The English version: I am still hoping someone with a decent grasp of English will step in and translate it. I simply can't find the time (spend too much of it on two-stroke forums ).

[Frits Overmars]

... is the restrictor better at the air entry to the engine or at the plenum/air box entry, Frits?

The best you can do with a restrictor is to maintain a constant flow velocity all of the time. That means: a large plenum between it and the pulsating engine suction.

I think maybe some of that Russian rocket paint (ok house paint LOL) might be a good idea for the inside to stop the heat transfer from the cases to the intake.

Certainly. And while you're at it, try to coat the insides of the crankcase and the transfer ducts.
Too bad this Russian stuff isn't fuel-resistant; you will have to coat the coating, which makes it a bit less easily applicable.

[TZ350]

First move was to mark the flywheel at 15 deg BTDC.



Then using a timing light, adjust the Ignetec's base advance so the 15 deg advance line, lines up with the mark on the flywheel.



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. ""



I am still not sure if the torque curve is the ideal thing to follow because its just the air that's trapped, what about the air that is lost out the exhaust it must carry some fuel with it to so the fueling curve would need to be bigger than the torque curve in the areas the torque curve is lower???? Ie the fueling curve would need to be a higher flatter line than the torque curve is at lower rpm????



Its interesting that at lower rpm and above 35% the torque curves nearly match each other,this must be where the effective WOT thing is happening well before the throttle is actually wide open.

[teriks]

OK had a play with the EFI....

I have been modeling my Alpha-N or TPS/RPM based map on the torque curve so it got richer as the torque and rpm increased. But the break specific fuel consumption drops off, so I am a bit confused.

Yup, fuel efficiency rises when everything is starting to work together..
Anyway, in case you have missed it, you can plot fuel flow in EngMod. Could give some decent clues of where to start.

[Haufen]

Certainly. And while you're at it, try to coat the insides of the crankcase and the transfer ducts.
Too bad this Russian stuff isn't fuel-resistant; you will have to coat the coating, which makes it a bit less easily applicable.

too bad, what about hot gearbox oil? Can it cope with that?

"" 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. ""



I am still not sure if the torque curve is the ideal thing to follow because its just the air that's trapped, what about the air that is lost out the exhaust it must carry some fuel with it to so the fueling curve would need to be bigger than the torque curve in the areas the torque curve is lower???? Ie the fueling curve would need to be a higher flatter line than the torque curve is at lower rpm????

Have a look at trapping efficiency to get an idea about the relative ratio between torque and fuel flow.

Did you not kind of auto-calibrate the FI using a lambda probe some time in the past? Sounds like a good idea to get a baseline calibration for the fuel map to me.

Yup, fuel efficiency rises when everything is starting to work together..
Anyway, in case you have missed it, you can plot fuel flow in EngMod. Could give some decent clues of where to start.

Do you know if that value includes the amount of fuel leaving the cylinder unburned?

[2T Institute]

The plenum re visited ...



Attachment 298098

Pretty much what we tried. The problem was, with the carb on the outside we got excessive fuel dropout in the plenum, EFI should cure that.



Attachment 298100 Attachment 298099

With a real short inlet tract there were problems with resonance in the plenum at low RPM that I called the Blarrrs and that the motor could barely pull through and it needed a longer inlet tract to cure that.

Attachment 298101 Attachment 298102 Attachment 298103

Then I tried an automated way of halving the area of the inlet tract at low RPM. This worked a treat and it was surprising how high the power curve would go before falling over (Blue line).

Have a look at a late model Ford Falcon engine they have a large variable length inlet that works by vaccum. A simple butterfly valve closes the long runner at 3800.

[TZ350]

Some definitions.

DELIVERY RATIO.
Mass of fresh charge supplied to the cylinder during scavenging divided by the mass of atmospheric air which would be contained in the swept volume ( not the trapped swept volume ) of the engine.


TRAPPING EFFICIENCY.
The ratio of mass of delivered charge which has been trapped to the total mass of delivered charge. Remember that some of the latter exits the exhaust port before combustion starts, ie during scavenging. This turns out to be approximately equal to the scavenging efficiency divided by the mass based scavenging ratio.

CHARGING EFFICIENCY.
The mass of fresh charge trapped in the cylinder during scavenging divided by the mass of atmospheric air which fill the entire cylinder volume when the piston is at Bottom Dead Centre. It is equal to the Trapping Efficiency times the mass based Scavenge Ratio ( nearly equal to the Scavenging Efficiency ).


BSFC. ( Brake Specific Fuel Consumption )
This is the fuel consumption in kg/kw-hours. If the engine has a power output of 5kw, a BSFC of 0.5kg/kw-hour, and runs for 10 hours, it will consume 5 x 0.5 x 10 = 25kg of fuel.




Dratio Black line: DELIVERY RATIO
Ceff Green Line : CHARGING EFFICIENCY
Teff Red Line : TRAPPING EFFICIENCY
BSFC Blue Line : BSFC (Fuel Consumption)



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.



Now as you can see, not all the mixture that gets delivered actually stays in the cylinder long enough to be trapped there when the exhaust port closes. But with a carb all the "Delivered" air has had fuel mixed with it.

So that is my starting point, and the beauty of EFI is I can time the injection end point and reduce some of this wasted fuel, even better would be direct injection into the cylinder after the exhaust port is closed but that is another step for later.



A series of throttle position Delivery curves simulated using EngMod2T.

Now all this air would normally have fuel mixed into it at a set ratio, so I am going to use these curves to develop my next Alpha-N fueling map. You can see the WOT point is about 45-50% of the real throttle opening up to about 8,000 rpm, so the map will have some flat areas on it.

[TZ350]

Ok, the map making went better but no matter how big the numbers I put in the map I could not get the thing rich enough to stop detonating at 10K plus rpm so I guess the secondary injectors are not big enough. Have another look tomorrow night....

[speedpro]

Did the injector pulse widths top out at the rpm you were testing?