EngMod2T Q&A

[dmcca]

So ive got some questions about Engmod2T... hopefully there are other users on KB that can help, and maybe we can create a bit of a database of info to share. The program seems very powerful but i sometimes wonder if im feeding in accurate data or if im getting things a little wrong... without a dyno at hand its very hard to be certain.


When modelling a reed cage that has an internal divider or stuffer before the reed petals, do you subtract the area of the divider from the area of entrance to the reed cage when calculating the 'diameter of the rubber block' (entered in the Inlet Port window)?

The photo below shows what im talking about...
http://i553.photobucket.com/albums/jj373/dmcca/DSC08431.jpg
The rubber intake boot is on the right, the reed cage is on the left.
The rectangular area at the exit of the rubber boot is calculated and entered as the last diameter of the intake pipe (basically modelled as the cylinder side of the carb). In this case the area is 1190mm^2 which equates to an equivalent diameter of 38.9mm. This is entered in the Inlet Type window.

When you then go to the Inlet Port window to model the reed cage itself it asks for the 'diameter of rubber block'... this is essentially the area at the entrance to the reed cage but do i just enter the same value of 38.9mm diameter or remove the equivalent area (in direction of flow) of the divider from this figure??... in this case the divider is 8.5mm x 39.7mm = 337.45mm^2, so the total area of the reed entrance becomes 1190-337.45 = 852.55mm^2 or equivalent diameter of 32.5mm

The graph below shows a KTM200 modelled with the above reed cage, black line is a "diameter of rubber block" value of 32.5mm (divider removed from total area), red line is a "diameter of rubber block" value of 38.9mm (divider ignored). Obviously taking the divider into account looks better, but which one is actually correct???

http://i553.photobucket.com/albums/jj373/dmcca/ktm200graph.jpg

To complicate things further, in this case the divider protrudes from the reed cage by about 10mm, so when its bolted to the rubber intake it technically changes the final area of the intake pipe just before it ends... should i actually be removing the area of the divider from the last stage of the cylinder side carb pipe instead of from the entrance to the reed cage???

[wobbly]

The inlet port and reed is very tricky to model correctly.
Look at the RZ400 inlet for my F3 bike.
The 39 dia is the actual area at the reed block face ( less the divider ), the 41.5 dia is the effective reed block flow area.
The 35mm is 2/3 of the reed block length, this models accurately the stuffer.
At the other end is the carb trumpet with a 6mm end correction length, this 6mm at 69mm dia is the flow area curtain at the carb entrance.
Using this setup you get the correct effective length of the inlet and the waves bouncing up and down the tuned lenfth are timed correctly.
In reality my "rubber boot" is bigger in diameter at the reed face, but using the effective diameter less the divider sets the actual area as seen by the flow.

This info was gained off an instrumented engine used for a PhD project at AK Uni, and initially I left the reed length off altogether, and added 1/2 the carbs trumpet dia at the other end.
This gives approx the same length overall.
But the method above is more accurate for all engine and reed sizes.

[teriks]

Good info, to bad I'm not dealing with reeds (yet anyway). On the other hand, modelling the atmospheric side is hard enough to deal with.
Do I understand you correctly if I say that D=69 is what Neels calls "Starting diameter" in the help files?

Now to something that's been bothering me for a while, how to model Prof. Blair's "Best Bell" (http://www.profblairandassociates.com/pdfs/Bellmouth.zip)?
(More Blair candy at http://www.profblairandassociates.com/RET_Articles.html, mostly four-stroke thou.)
Judging by the article, I would believe that the correction length should be kept well below the 0.5 times the starting diameter suggested in the help files.
-It looks like you have come to the same conclusion on your RZ400 model, although I don't know the geometry of your carb.

Apart from a bunch of simulations I have built and ran such an intake, but without a dyno it's all but impossible to evaluate the small improvements suggested by simulation.

Need some sleep, but Ill try to produce something describing my modelling tomorrow.

[wobbly]

Yep, the 69 is the "starting dia" of the bellmouth.
The trick is to use the correction length that gives you the effective curtain area equal to that start dia area.
The reed end is alot more complex, as they are open/closed/partially open all the time, so present a variable length during one cycle.
But using the lengths described gives an accurate representation on screen,that correlates with the instrumented engine testing.

[teriks]

So, as promised, this is how I approached the "best bell".
Black lines=actual geometry.
Red lines=simulation model.
249992
Seems I have put way too much detail in the model, both compared to wobbly's example and to the examples in the help files.

Now, how's "effective curtain area" defined?
If you said just curtain area, I would have guessed 22*PI*4 in my example above, but now I'm lost.

Can I use the fact that I was blond as a kid as an excuse for asking stupid questions? ;)

[wobbly]

I dream about blonds so no you cant, it would ruin everything.
In your model the sim would work well with a taper from 12 out to the 22 dia bell entrance face dia.
The end correction is defined as the carb dia squared divided by 4 times the bell entrance dia.

[teriks]

I think I'd rather don't mess with those dreams :)

Now that's a definition of correction length that makes some sense even to me, thanks wobbly, this is gold!
Made some sort of illustration as a reference for my self, might as well share it.
250091

[teriks]

Double post...

[dmcca]

The 39 dia is the actual area at the reed block face ( less the divider ), the 41.5 dia is the effective reed block flow area.

This info was gained off an instrumented engine used for a PhD project at AK Uni, and initially I left the reed length off altogether, and added 1/2 the carbs trumpet dia at the other end.
This gives approx the same length overall.
But the method above is more accurate for all engine and reed sizes.



The end correction is defined as the carb dia squared divided by 4 times the bell entrance dia.

Thanks for the great info wobbly!!!

Is the effective reed block flow area you used just the area calculated by the program in the Inlet Port window? Or are you calculating a different figure for this?

[wobbly]

Yes, the reed program calculates the effective round port diameter, and I use this as the area at the end ( beginning) of the inlet length.

[wobbly]

Here is the single most important trick to be learnt about intake tuning.
This is RZ400 for F3.
The intake tuned length is optimised for 10,000 rpm, this is shown by the red line, case pressure, dropping below atmospheric, at the same
time as the intake pressure ratio yellow line,goes positive at the reed face.
This puts negative on the outside of the reed and positive on the inlet side, opening the reeds very quickly and early.
Shorten the intake and the yellow crossing point moves to the right,giving the coincident crossing point at higher rpm.
This gives the lie to the fact that using intake rubber and carb lengths off a 125 are correct for a 200 to 250cc cylinder as is done by most manufactures and is accepted by tuners as OK.

[dinamik2t]

Hi, I'm new here! (had a subscription for while, but never posted)

I 've been using EngMod2t for about a year now. I have previous experience from mota.. that's day vs night!:sleep: I haven't had the chance to dyno test any results yet though.

I would like to share EngMod files, even though I don't have a lot of them. Mostly a couple of pipes, some carbs and a few moped tuned engine files. All 125cc class.

I also have a question. What value do you use for 'combustion efficiency'?? In the manual, mr Neels says that 0.87 should be right for modern engines and up to 0.92 for GP engines.
With 0.87 I get very good results, but I am not sure whether that value is a little optimistic.

Also, the engines we tune around here are mostly air-cooled. I see you modify air-cooled engines too. What values of cylinder temperature do you consider "safe" ?? I try not to exceed 2700 in sim results, but I 'm not sure about the real-life correspondance of these values.:no:

[teriks]

Ok, so I have tested three different bell models.

RED: According to my first picture posted in this thread, end correction 4mm.
BLACK: #1, but with end correction 1.6mm.
GREEN: Wobbly version, my second picture posted in this thread.


Results:
250865
The seemingly small change in end correction of 2.4mm gives a larger change in the result than changing the detailed model into a simple cone.
-If the 1.6correction is correct, I have work to do...

Perhaps I should bring this over to the ese-thread, lots of engmod-discussion there now. :confused:

[ief]

Such a good idea this thread and so little follow up...

I find it pretty hard as well but it's realy a great (and fun) tool, to bad about the only one I know of that knows what he is doing with it is Wob and well, Neels himself :)

I am playing with tuning the inlet myself now and found the opposite of what Wob was saying, thus, making it longer moves the wave to the right :scratch: And then there is that making the inlet longer makes the wave less strong...

Thing I thought about was, there is only one sort of slide carb but was led to believe a flatslide performs differently from a round slide, that's not an issue?

Long story short, it will take quit some time for me to grasp this al a bit but that's part of the goal and fun.

On to modeling a carb correctly...

cheers!

[ief]

Or an airbox...

leeds to a question I came across earlier.

When looking at these two graphs I can't find the logic.

Ab6 = without airbox, makes less power (say 1 hp)
Ab7 = with airbox

Ab6 shows more reed disp. be it later, it closes later too so in my mind it should flow more, thus making more power. All makes sence, it's better timed and allthough the puls action is slightly less the proper timing compensates witch shows in the reed disp. So far so good but...

Ab7 makes more power? :scratch:

So ithought I'd see what the flow at the inlet does and this baffles me even more, Ab7 seems to flow far less then Ab6 but still makes more power and reed disp and crank P ain't that different?

I must be missing something...

attached P traces M traces and combined.

[teriks]

Such a good idea this thread and so little follow up...

I find it pretty hard as well but it's realy a great (and fun) tool, to bad about the only one I know of that knows what he is doing with it is Wob and well, Neels himself :)

I am playing with tuning the inlet myself now and found the opposite of what Wob was saying, thus, making it longer moves the wave to the right :scratch: And then there is that making the inlet longer makes the wave less strong...

Thing I thought about was, there is only one sort of slide carb but was led to believe a flatslide performs differently from a round slide, that's not an issue?

Long story short, it will take quit some time for me to grasp this al a bit but that's part of the goal and fun.

On to modeling a carb correctly...

cheers!
Probably because a seemingly simple question could take a lot of effort to answer..
Personally, I'm reluctant to answer something I'm not very sure of, but after a few more Czech beers you might get some really "interesting" answers ;)
(Back to the beers and garage to prepare for competition on Saturday)

[marsheng]

Neels. I've just found this thread but I see it is not too active. Any chance you can send a request to join this thread to all your purchasers ? Do you know of any other engmod forums? Its a great tool but real live experiance is required to get the best out of it.

Cheers Wallace

[Vannik]

Wallace,

I only found it about a year ago and are thinking along the same lines as you,to send a link to all the licensed users of EngMod2T.

Cheers
Neels

[ief]

Now we're getting somewhere :)

Today It seems I holed a piston in engmod, didn't want to write results. Haven't been able to figure out what's going on.

Worked fine before on the same file. Tried reinstalling engmod, save the project under a new name. Went over the project over and over to see if something wierd was going on, see nothing.

Latest it seemed to be doing it only on turbulent mode but not sure.

Just shows a blank screen at the end of the run and gives a 'not responding' message.

And my previous question still stands about the dip after running with newly written cbd file after turb run. Is that a fault or what is it?

[Vannik]

Ief,

The moment EngMod2T hangs (holed a piston?) please pack the project and send me the pack file with a brief description to explain what happens.

The turbulent model is not an analytical model but a statistical model combined with some physics so it will not work for all engines in all cases (as it says in the help files) but as more engines are modeled with it and more results become available it improves. Problem is improving it breaks it for some cases. Sometimes hand editing of the file created by Post2T is required.

Vannik

[dutchpower]

Neels


After the upgrade having big detonation !!!!

[Vannik]

I have no idea what you are simulating or what you used before. Were you getting the same max unburnt air temperatures without detonation or has the max unburnt air temperatures increased?

[peewee]

neels is there any plans to add nitromethane as another fuel ? :laugh:

[Vannik]

neels is there any plans to add nitromethane as another fuel ? :laugh:

It is there - choose methanol as base fuel with the right nitro ratio - have used up to 94% on 4T simulations. Make sure you are much richer than stochiometric.

[koba]

Wallace,

I only found it about a year ago and are thinking along the same lines as you,to send a link to all the licensed users of EngMod2T.

Cheers
Neels

I'd be keen!

[Vannik]

This bike had its engine designed by Wobbly using EngMod2T.

335486

[Vannik]

I posted small error fixes today, contact me please if you are a license holder and did not get the notification.

[41juergen]

Hi Neels,
I have tested the new version with my 3XV project and it ran well. Only noticeable change was a slightly lower TUbMax and going along with that a little less max power and little better over rev. Is it because I didn't changed the pipe temp to the pipe temps at different length positions?
wbr
Juergen

[Vannik]

Juergen,

Was that with prescribed or turbulent combustion? With both there were small error fixes in correcting mass preservation issues.

Neels

[41juergen]

Juergen,

Was that with prescribed or turbulent combustion? With both there were small error fixes in correcting mass preservation issues.

Neels

Neels, that was with the turbulent combustion... I must admit that I didn't changed the pipe temp setup from the former vector (pipe temp depending "only" from rpm) to the newer matrix setup (pipe temp. depending from position and rpm)...

[Vannik]

Not changing the pipe temperature method will give the same answer as before.

The biggest change was in the turbulent combustion model mass preservation coding. Before it could burn more mass than was there - obviously not right.

[41juergen]

Ok, got it, thanks a lot.

Just another "wish": it would be good to have a second y axis in the dat evaluation graphs, e.g. to show the power curve on the left (with a scale e.g. 20-50 kW, depending on values) and on the right side the deto's or efficiency factos (with a scaling e.g. 0-2).
I assume that would request some seriuos changes in the code, right?:innocent:

[Vannik]

Yes, but already halfway there, the PV graph has it by default.

[Vannik]

I am working on a utility to show a schematic of the transfer port passages as many still get it wrong. Below a picture of where I got to over the weekend. It must still be corrected to use the same horizontal and vertical scales. Anything I should add? Any other ideas?

335784

[sispeed]

Looks good. Can't wait to see my model with this new view
Regards Siggi

[41juergen]

Just another suggestion: have you ever thought about creating emission data as an output (e.g. mass flow in g/sec)? I know that most of the users don't need that, but for working on road going bikes it would be a perfect input for a catalyst design software... :msn-wink:

[Vannik]

Yes, I have and plan to also add basic catalytic converters sometime in the future.

Currently I am working on a duct element that can simulate the increase in flow volume and the dropm in temperature as the result of NOX injection.

[Vannik]

I posted more small error fixes today, if you did not get the notification please email me.

It also adds a contra rotating crank engine layout option.

[peewee]

would it be feasible without much trouble to add a print function ? seems like this would be helpful especially when setting up a new engine for the first time. you could print off the pages and take them in the garage and fill in the data boxes then return to the computer and type in all the info.

[Vannik]

would it be feasible without much trouble to add a print function ? seems like this would be helpful especially when setting up a new engine for the first time. you could print off the pages and take them in the garage and fill in the data boxes then return to the computer and type in all the info.

Are you asking for something similar to the 4T version?

339193

[peewee]

yes that looks like it would be great. then the pages could be printed blank and the data boxes filled in with pencil in the garage then transferred to computer later. I don't know how much trouble it would be for you however

[Vannik]

I have just released an update. Make sure you received the update links.

Next I will see about creating a blank document for manual completion when measuring.

[Vannik]

yes that looks like it would be great. then the pages could be printed blank and the data boxes filled in with pencil in the garage then transferred to computer later. I don't know how much trouble it would be for you however

Found an old one. Is this ok or do you need it updated?

339286

[peewee]

Found an old one. Is this ok or do you need it updated?

339286

old one will be fine :drinknsin

[Vannik]

Released an update. If you did not receive notification let me know please. Spam filters are overactive sometimes.

Summary of Major Updates to 2T Suite
9 August 2019

There has been some major updates to the software since the last official release. Twice in the last 6 months a new release was just about ready before being interrupted by either refinements or additional functionality.

• Short Summary of Major Updates:
• Updated pipe junction model
• Updated turbocharger and supercharger model
• Adding an opposed piston two crankshaft option
• Adding a tandem twin engine
• New Uniflow scavenging model and dialog box
• First version of poppet exhaust valve to model a Uniflow engine
• Extra output in the power output file, this will automatically create a new power file
• More options in the compression ignition model
• An ignition curve generator was added, use with caution! It is only meant to get started
• General small bug fixes and improved robustness

Read the detailed description of the new pipe junction model in Dat2T Help first before using it. It is quite different. The old one will still work though. This is applicable for 3-pipe junctions as used in ATAC, boost bottles, wastegates, T-pipes and internal stingers.

The first time a full run is done on an existing model with the older version power output file the older version will be renamed and will still be available for opening in Post2T while a new one with the extra headers will be created.

The poppet valve addition is not yet complete so only the generated lift profile is active, VVT, imported lift profile and flow bench created Cd maps are not yet working. They will be added over the next few months.

It is no longer possible to test all available combinations or permutations so please report any issues!

[Vannik]

Released some small bug fixes today.

[flyincat]

Has anybody played with Ethanol fuel in EngMod2T? I was doing some messing around and simulating E85 (85% ethanol/15% gasoline) with some interesting results. The sim was first run on Regular and Premium with squish and timing optimized to start seeing deto warnings. This is where things get interesting. I changed the fuel over to E85 and changed the AFR to maintain the same lambda as I was running on gasoline. Timing, squish, etc., besides compression ratio, were all left the same as the initial run on E85 (12.5:1 CR). There was a HUGE increase in power, especially below peak. Also interesting is how far TUbMax went down compared to the gasoline runs. Next I kept increasing compression ratio CR all the way to 15.5:1 and power kept going UP and UP below peak. This seems a bit like fantasy land to make such big leaps. What am I missing?

343202343203343204

The other interesting thing is the power on E85 went right past the STA.

343205

[Vannik]

I have no experience with either clean ethanol or with it blended with gasoline. My experience is limited to methanol. But some pointers:

The biggest increase in power comes from the much bigger latent heat of evaporation (Gasoline~305kJ/kg, E85~836kJ/kg) and that causes two good things:


The incoming charge density is increased by cooling it down during evaporation
The temperature of the mixture in the cylinder at the start of compression is much less, leading to a lower maximum unburnt temperature during combustion and an effective anti-detonation result.



E85 is used extensively by the drifter crowd as a detonation combatant when running high boost pressures.
In a 2T engine we can increase the compression ratio quite a lot - clean ethanol has an effective octane number of 109.

Currently there is no detonation checking for Ethanol or E0 to E100 built into EngMod2T, it is being rectified. We should verify this before analyzing the results.

[Frits Overmars]

Where does the E85 power come from? From internal cooling, yes. But also because with the amount of air that the engine inhales, you can burn much more E85 than regular petrol.
I worked it out some time ago for my German mates and I have been planning to produce an English translation, but other things keep getting in the way, so here it is in its original form. Let's see how Google Translator will mutilate it.
343257

[flyincat]

Thank you, Neels and Frits!

I do have some experience with E85 in forced induction 4T, so most of this makes sense. In full disclosure, I ran the sim comparison with all of the same temperature inputs. With all of the cooling from E85, this may be majorly wrong!

Neels, any tips on where I can look in the sim outputs to figure out where things might be over optimistic? On E85 and much more compression, this pump gas engine went right past 200psi BMEP. Something can't be right.

Frits, I think google translate did an OK job, at least the numbers make sense to me. I couldn't figure out the part about the wet candle towards the end. haha Great job breaking the numbers down for comparison! I really like the derivation down to 3.46x evaporative cooling. I knew it was a lot, but never realized it was that much!

There is one statement in the EGT section that I noticed. "...because E85 probably burns a bit slower..." Everything I've known about E85 is that it actually burns FASTER (at comparable lambda). I think the faster/slower and more/less ignition advance story gets confused when we start talking about knock limited engines. Usually in the 4T world, the E85 discussion involves some forced induction. With forced induction, people are always talking about ADDING ignition advance. Well that is because pump gas ignition timing was way retarded and not anywhere close to MBT. So all things considered, a MBT tuned engine on pump gas would normally require LESS ignition advance on E85. No?

343303

Here is one last thought on E85 in a 2T vs 4T. A 2T has much more surface area (crankcase, transfer ports, etc) to act on an probably more duration than a 4T (port injected EFI). Is it possible that a much more dense charge in the crankcase greatly benefits a transfer STA limited engine? In comparison, the 4T only has cooling at the very end of the intake tract and very short intake tract duration if the injection is spraying through an open valve.



Google translated, below:

Gasoline & E85 © Frits Overmars

Many motor sport regulations dictate that only fuels available at public gas stations
may be used. Diesel is excluded because a larger diesel oil leak
Racetrack could be unusable for a longer period. Thus remain gasoline and E85.
Below, we compare the important properties of these two fuels.
An air / fuel ratio, with each fuel molecule being just enough for its combustion
The amount of oxygen molecules available is called a stoichiometric air / fuel ratio.
It is indicated with lambda = 1.
Lambda> 1 means an excess of air. e.g. Lambda = 2 means that twice as much air is present
as theoretically necessary for complete combustion.
Lambda <1, however, means a lack of air, or, in other words, a fuel surplus.
In reality, racing engines never run with lambda = 1, but always fatter, because the mixture never exactly
is homogeneous, and because unused oxygen from a performance point of view would be a waste.
Optimal is lambda = 0.86. This optimum value applies to every fuel. However, the lambda actual value plays
in the following comparisons between gasoline and E85 irrelevant and thus can be left out.
One can calculate the fuel consumption for each type of fuel, if one considers the stoichiometric air / fuel
Ratio of the respective fuel knows.
Gasoline: 14.7; that means: to completely burn 1 kg of gasoline you need 14.7 kg of air.
Ethanol: 8.4; that is, to completely burn one kilogram of ethanol requires 8.4 kg of air.
Methanol: 6.5; that is, to completely burn 1 kg of methanol requires 6.5 kg of air.
The amount of air that can suck a motor is not dependent on the fuel, but is determined by
Displacement, speed, slot surfaces, timing and pressure differences.
For our calculations, we assume that the engine draws in 1 kg of air per revolution.
(In reality, that would be nice because air weighs 1.233 grams per liter, so 1 kg is 818 liters).
For this supposed 1 kg of air the engine needs:
1 / 14.7 = 0.068 kg of gasoline
or
1 / 8.4 = 0.119 kg of ethanol
or
1 / 6.5 = 0.154 kg of methanol
If a fuel contains 85% ethanol and 15% gas, you need 1 kg of air for:
(0.85 x 0.199) + (0.15 x 0.068) = 0.111 kg of fuel.
This is 1.6 times the mass of the 0.068 kg of gas originally needed.
When using E85 instead of gasoline you can burn 1.6 times as much fuel per kg of intake air.
What does that do for performance? That depends on the combustion value expressed in MegaJoules per kg:
Gasoline: 43.0 MJ / kg
Ethanol: 26.8 MJ / kg
Methanol: 20.1 MJ / kg
1 kg of E85 contains 0.85 kg of ethanol and 0.15 kg of gasoline, and thus has a combustion value of
(0.85 x 26.8) + (0.15 x 43) = 29.3 MJ / kg.
E85 thus has a lower combustion value than gasoline. But because we use 1.6 kg instead of 1 kg of gasoline each time
E85 can burn, the total released energy per kg of air but higher.
Compared to 43 MJ / kg for 1 kg of gasoline stands 1.6 x 29.3 = 46.9 MJ for 1.6 kg E85.
That means 9% more energy and thus 9% more power.
Now there is the problem that the fuel quantity is generally not in kilos, but in liters
is measured.
1 kg of gasoline = 1.389 liters
1 kg of ethanol = 1.267 liters
1 kg of methanol = 1.266 liters
1 kg E85 = (0.85 x 1.267) + (0.15 x 1.389) = 1.285 liters
Instead of 1 kg of gasoline or 1.389 liters of gasoline, we need:
1.6 kg E85 = 1.6 x 1.285 liter E85 = 2.056 liter E85. That's 1.48 times the volume.
The consumption is 1.48 times higher: instead of 1 liter of gasoline now 1.48 liters E85.
The capacity of the tank, and all flow areas in the entire spray system must
therefore be 1.48 times larger. That means: All diameters must be 1.22 times bigger.
The float chamber valve seat is often forgotten.

Control:

A Rennzweitakter needs about 7 cc of gasoline per hp per minute.
The same engine With E85 would consume 1.48 times this amount of fuel, but it would also be 1.09 times
deliver the original performance.
Its consumption would be (1.48 x 7) cc per 1.09 hp per minute, or 9.5 cc / hp / min.
With a measuring cup and a stopwatch, it is easy to determine whether the spray system is sufficient.

Engine temperature:

The specific evaporation value shows how much kiloJoule of heat needs to be added to fuel 1 kg
evaporate.
Gasoline: 380 kJ / kg
Ethanol: 900 kJ / kg
Methanol: 1100 kJ / kg
1 kg of E85 contains 0.85 kg of ethanol and 0.15 kg of gasoline, and thus has a specific evaporation value
of (0.85 x 900) + (0.15 x 380) = 822 kJ / kg.
The specific evaporation value of E85 is thus 2.16 times higher than the specific evaporation value
of gasoline.
In addition, the engine now consumes 1.6 kg E85 instead of 1 kg of gasoline. The total evaporation required
Heat for the aspirated air / fuel mixture is thus 1.6 x 2.16 = 3.46 times higher.
This heat is removed from the sucked air. The mixture enters the engine much cooler.
Thus, the internal cooling of the motor in E85 operation is considerably better, and the thermal load
of the engine is lower, despite 9% more power than gasoline.
Two-stroke engines react strongly to temperature differences. The cooler running E85 engine can do that
even more than the 9% extra power calculated above, and also suffers less
an increasing engine temperature during the race, especially in air-cooled engines too
Performance loss would result.

EGT:

The exhaust gas temperature may be somewhat lower despite higher power than with gasoline operation.
The engine will probably not turn quite as high as before.
An attempt to correct that with lean spraying can easily backfire.
Wrap the exhaust is better, but the first piece of the manifold, where purged fresh gas
before it is pushed back through the exhaust shaft in the cylinder, must remain as cool as possible.
How long this cool piece should be depends on the outlet channel diameter or the manifold
Diameter off. Expect that the cool part of the exhaust system must be so long that it is a
Volume equal to the displacement volume may contain; then it is definitely long enough.
A second method of increasing the exhaust gas temperature is to fire the ignition later
adjust. But you can not go too far with that, because E85 probably burns a bit slower,
and therefore not less, but would require more pre-ignition.
It would therefore be better if the maximum speed and the maximum speed had suffered too much,
make an exhaust with smaller lengths and unaltered diameters. Only the tailpipe
Bottleneck must be adapted to the additional power.
Compression ratio:
The compression ratio could be higher because E85 has a higher octane rating than gasoline,
but that only makes sense in four-stroke engines. Especially turbo four-stroke will be quite lively with E85.
In Rennzweitaktern but you should compact low. That promotes performance, bandwidth,
The reliability, and if you do not have a strong spark, it also helps the ignition.

Oil:

Not every two-stroke oil mixes well with E85. Castor oil is already suitable.
e.g. Maxima Castor927. Eleven 909 should also be usable.
The oil / fuel ratio may be leaner compared to gasoline when using E85.
For example, we take a mixture of 1 liter of oil to 20 liters of gasoline.
When using E85, the engine consumes 1.48 x 20 = 29.6 liters of E85 instead of this 20 liters of gasoline.
If we mix 1 liter of oil with this 29.6 liter E85, the engine gets the same amount of oil as before.

Focus:

Methanol, ethanol and E85 can attack various materials: copper, aluminum, magnesium,
Plastic hoses, gaskets, o-rings, etc. And when plastic bearing cages are attacked,
This can lead to major engine damage.
It is therefore advisable to run the engine with petrol for a few minutes after using E85
to let.
Determining the spray on the basis of the candle image can be dangerous with alcohol-containing fuels.
In methanol, I have found that the candle always stays wet. An attempt to thwart them
getting dry can cost flasks.
Sometimes you can also use a candle with a slightly lower degree of heat.
All alcohols are hygroscopic: they attract water vapor from the atmosphere and dilute
itself more and more.
Always keep the fuel tank closed, and avoid draining the vehicle's fuel tank.
Weighing is a better and safer way to determine fuel consumption.

[Vannik]

Here is one last thought on E85 in a 2T vs 4T. A 2T has much more surface area (crankcase, transfer ports, etc) to act on an probably more duration than a 4T (port injected EFI). Is it possible that a much more dense charge in the crankcase greatly benefits a transfer STA limited engine? In comparison, the 4T only has cooling at the very end of the intake tract and very short intake tract duration if the injection is spraying through an open valve.

Derek,

Absolutely - transfer port and crankcase cooling gives measurable gains.

I am adding the detonation feature for E0~E100 in EngMod2T, I will then have a better idea.

[flyincat]

Here's one from the Aprilia RSA 125 sim... The blue line is the baseline from the sim found on this site (100 unleaded, 14.8CR). The fuel was then changed to 85% ethanol (lambda stayed the same), black line. Further runs showed increasing compression ratio, all else constant. Anyway, it looks like ~8.7% gain at 13,000rpm for 17.8CR. Make believe OR plausible?

343305

[Vannik]

The trends are correct, with E85 creating more cooling which allows more compression. More cooling plus more compression will increase the power and move the whole curve to the left as is happening. While the trends are correct the magnitude is a bit suspect. I am suspecting the evaporation model and will investigate that further, it is not very sophisticated and might over predict the cooling.

Is there anyone with actual measured performance and temperature data for a high performance 2T that is willing to share?

[flyincat]

I did actually poke around at the Temperature traces (crankcase, transfers, etc.) and I didn't see a glaring obvious change from gas to ethanol. But, I should be clear that I didn't change any wall temperatures on the input side either. In fact, some of the ethanol runs had slightly higher temps, through the bottom end, than gasoline. It must be the cooling effects are all accounted for in the combustion chamber because that's where I saw a big difference in temps.

I also looked at Mass Flow (air) all the way back to the intake and didn't see a clear trend vs power increase.

One other thing that could be way incorrect is the Combustion Efficiency. I left this the same for gasoline vs ethanol. Maybe this needs to change as ethanol is added?

[Condyn]

Hi, new to kiwibiker, but not two strokes. A couple prior purchase questions about EngMod2t.

I understand the software is going to be somewhat complex, however I am still concerned about some small things that my knowledge doesnt contain. I have looked thru the Dat2T input form pdf to see what is needed, and am curious if the " help " button reveals instructions or tips to take measurements needed so they are not done incorrectly??

I also know that there will clearly be a learning curve with using this software, and logging in the hours will be most valuable. I must still ask if there is anything I should be aware of so I do not get taken down false trails whilst using??

Thanks

[Vannik]

Hi Condyn,

I try to make the Help files as descriptive as possible with guidance without being prescriptive. Plus there are extra documents available for specific topics, if you get stuck just ask.

The software is 1-dimensional so some aspects like in-cylinder flow is modeled using a quasi-dimensional approach and not full 3D. Full 3D will increase the price at least 10 times and the run duration a 100 times. So there are some limitations.

Neels

[jfn2]

Hello Vannik
I'm working on a EngMod file for a Kawasaki KX65 engine and wondered if you or anyone else had a working model already written up or any information I could use as I do not have my engine apart to be able to measure it. I figured I'd check here first. Thank you very much.
Jeff

[Vannik]

I do not have a model of the KX65, closest I have is KX85.

[jfn2]

HEllo Vannik
Thank you very much for the reply. I don't think the 85cc engine and the 65cc engine are close enough but I will kept you in mind if and when I get into the 85cc class. I'll ask in some of the other forums if anyone has figured one up or I'll have to wait until I tear mine down. I'm sure I'll be asking you more questions.
Jeff

[Condyn]

Does this STA methodology work properly for a multi-cylinder engine? The top of the page states an individual cylinder volume, but combines the HP of the cylinders on a multi-cylinder engine. The achievable power listed on the particular engine Ive modeled Is roughly 30hp higher than what I know these ports to be capable of. I understand Its taking into account only the port windows and assuming everything else is perfect. I must admit Im not using anywhere near the best scavenging model. I also understand this is a semi-empirical method as mentioned in the files. The target values listed are all greater than the achievable power which is already way too high. I think maybe if it gave a BMEP achievable output instead of Power, that would make more sense for a multi cylinder perhaps? *
Edit* I suppose I could quickly turn my engine into a single cylinder and give that a try.

[Vannik]

The "proposed" power possible or the "suggested" STA values are based on BMEP values. So even though power is shown the calculation is based on the BMEP value.

It assumes very good scavenging and very good delivery ratios and very good trapping efficiency. It is what is possible if everything works as expected.

[Condyn]

As always, thank you for the great support

[OopsClunkThud]

I'm trying to model a single exhaust port where the side walls are not parallel (as pictured). my approach was to use a bridged exhaust with a bridge width of zero as this allows for a "side wall angle". The side wall angle is 22.6°, but after saving and reopening this always gets lowered to 19.798°. Also, the area in the STA screen shows NAN, so clearly it's not liking the numbers.

Is this the best approach or is there a better way to go?

348460348461

[Vannik]

There is a built-in limit to side wall angle. It is very conservative, I will update it to a less conservative value in the next day or two.

[OopsClunkThud]

There is a built-in limit to side wall angle. It is very conservative, I will update it to a less conservative value in the next day or two.

Thank you!

spent some time today mapping out the cord width across the port, and it seems like that would drive the natural limit. the angle I had (22.6°) was in excess of that limit (21.3°) but that value is still larger than engmod lets you set.

I could use the profiled type if need be, that would likely get around the issue, but not as clean.

[jfn2]

Hello Neels
I've had your program for a couple of months but just now have time to play with it. I'm trying to model an old school engine ( single exhaust port, straight transfers, piston port) and I ran into a problem with the exhaust system. I started with the TZ 250g model and just changed the engine, some of the transfer info) I kept the TZ250g info when I didn't know the answer to some inputs because the engine I'm trying to model is very much like the TZ. In fact it is very much like the Yamaha 350 engine except for the reed intake. It's a Polaris 340 snowmobile race engine. Bore= 62mm, Stroke= 55.6mm, Rod center dist= 112mm but it has no boost port. When I put in the dimensions for the exhaust pipe then I try to run the sim it gives me a error code that says that this pipe will not work. I have checked my numbers a couple of time and cannot find the problem. I know the pipe works because I've used it racing. I do not have the file completed yet so I can not pack it, I don't think. Is there anything I can do?
Thank you, Jeff Neilan

[Vannik]

Hello Jeff,

Two possibilities assuming you get the message from Dat2T and not EngMod2T:

1. Try to pack it and if it does pack, email me the pack file.
2. If it does not pack, open it with Dat2T, open the exhaust and save it, then save the project. Then, before opening Dat2T again, send me the following file: "C:\2Stroke\Dat2TErrorLog.dat"

I will then see if I can find the issue.
Kind regards
Neels

[jfn2]

Thank you Neels I will try and see what happens. I let you know.

[jfn2]

Hello Neels
Thank you for the paper you sent me about the Husky chainsaw. Do you have a file for your EngMod program that follows this paper? I would like to try to incorporate this t-model ex pipe into the handle as is suggested in their studies but I do not have a saw like this and I can find no one that has tried this. Thank you very much for your support and time. Jeff

[Vannik]

Hi Jeff,
There is not enough info to accurately model it but I have a rough approximation of it. Do you want the pack file?
Neels

[jfn2]

Hello Neels
Yes I would like to see your file, thank you. Looking around I do not see and can not find many people that know about this style of tuning. Again, thank you!
Jeff

[Vannik]

Okay, sent.

[Vannik]

The T-pipe discussed here is from SAE2001-01-1853 and looks like this:

348921

To model it the following manifold is selected:

348922

Then the following silencer is selected to add the box outlet with restricted outlet:

348923

And then to get the box dimensions right:

348924

Next the pipe dimensions and the collector junction has to be added.

[jfn2]

Hello Neels
Thank you very much for the pics explaining the T-pipe junction. Your pack file would not open but I managed to open the data file and I tried to model my own file but I was stuck about the T-pipe dimensions. Your pics really helped. I'll leave you know how it works. Thank you! Jeff

[Condyn]

When was the latest engmod2t suite update released? Not sure if I am up to date.

[Vannik]

Last official release was in August. I have had about 6 new releases prepared but then had urgent requests, mostly from the opposed piston crowd. I am hoping to do a new official release in the next week. Just chasing an error in a specific version of scavenging plenum on an OP2S engine model.

[Javi]

Hello everyone, I'm Javier, from Jerez, Spain.
Hello Mr. Vannik.
I am a new user of EngMod 2T, I am learning to use it, I await your help with any doubts that arise.
I am doing a translation of the manuals into Spanish.
I've been reading the 2T forum for almost a year, your are unique.
We currently compete in a 125cc championship with a 1986 Yamaha RD 125 YPVS, against the Aprilias RS and Cagiva Mito, and we are not far from them, due to suspension problems.
We are not professionals, we are a group of old friends, and our goal is to have a good time at the Jerez circuit, without making a fool of ourselves. It may seem that we have a "motorcycle pot", but it only seems so. We are also fixing a Kawa AR 125, with the same objective. I do not write in ESE's because I am not at the same level, but I am not stupid either.
Greetings to everyone.

[Vannik]

Hello Javier,
Welcome here!
I have also users of EngMod2T in Columbia and Ecuador and other Spanish speaking places. I think I must ask them if they want to also discuss with you, maybe we can make a good Spanish Help manual?
Kind regards
Neels

[Javi]

Always ready to help. We will try to do a good translation, and happy to share with my Spanish-speaking brothers.
In mid-November we have the last race of this year, and I will focus on EngMod.
I leave you a photo of my "girls". I can't find a pilot for the 350, there are no "balls" to drive it.

[Javi]

Hi everyone,time flies damn.Mr Vannik already has enough translation,for those who are interested.You can order them from me too.Free.I tink I habe donne a god traslaction.Too hot here to do motorcycles.Muerte al Pollo.

[Vannik]

I sent out the official notifications and download links today for the latest versions. If you are a valid license holder and did not receive the email please contact me so I can rectify the email list and send you the links.

[Vannik]

1. Batch2T: Added a multiple batch run utility, it is very new. Please try it and report any issues.

2. Dat2T:
2.1 Updated the pipe calculator
2.2 Updated the exhaust port, it now gives you four options for the auxiliary port power valve
2.3 Updated the temperature and pressure input, the inlet and outlet ambient conditions can now differ
2.4 Updated the combustion dialog to add fuels
2.5 Many refinements and bug fixes

3. EngMod2T:
3.1 Can now run multiple batch files in series
3.2 Many refinements and bug fixes

4. Post2T:
4.1 Added a logP-logV scale option to the PV diagram, this is till being developed but will mostly work
4.2 Many refinements and bug fixes

In the Help files of Dat2T and EngMod2T a topic "Error Reporting" has been added to explain how to report errors.

If you did not receive the update please contact me.