ESE's works engine tuner

[TZ350]

Page 1390

Fritz sent these through a couple of weeks ago but it's taken some time to get them up.


http://kiwibiker.co.nz/images/DKW-Ja...-carbs-CRP.zip
http://kiwibiker.co.nz/images/Honda-Suzuki-Yamahai.zip
http://kiwibiker.co.nz/images/Jamath...i-Kreidler.zip

EngMod2T and simulating pipe designs.

TeeZee,the older version used a completely different pipe modelling code. In this setup we found that 50* gave the best correlation to dyno tested powerbands, and was a source of real frustration for Neels who hates " fudging " numbers with a passion.


He came across a new thesis that modelled an RSW and this included a new pipe simulation technique, and this has been written into the new code. Now the pipe wall temp makes a huge difference ,and much more accurately represents the real world wall temp average over the pipes length.


When you have temp varying with rpm, this overrides the temp at max power entry, and I found in Beta testing that 325 and 425 worked very accurately. In a situation like the Aprilia model where a powerjet is switched off past peak, 450 is needed at peak rpm to get correlation
but is too hot for our "normal" sims.

As some of you know I have been developing my 300cc NSR. Its going really well except the pipes are cracking and braking all the time. They are SS no surprise. They really do cool very quickly and obviously heat fast as well. I was wondering if lagging the pipes for the first 300mm is a good idea to keep a bit of heat in there and not let them cool so fast. Will this help with the cracking yah reckon.

Years ago on pre 95 rs hondas guys used to put beads of high temp red silacon around the chambers to take the zing out of them to stop cracking , the promblem was the rubber mounts but it did work not to bad but looked crap

I'm not sure how the SS works as I've never had a SS pipe. As with nearly everything I've owned, if the pipe was cracking the cure was to mount it so it was free to move around while still supported. You probably already on to that idea.

...anybody who has tried this, tell me about expansion chambers made of aluminum, examples of which I saw on the French site. Since, I assume, they'd have to be made thicker than steel, does the weight savings balance the drawbacks? I assume the big drawback is heat-loss, but maybe that could be largely addressed with a ceramic coating. What alloy and thickness has worked (if any has worked)?

Don't do it. There is no weight saving, aluminium (aluminum to you) pipes won't work without an internal ceramic coating, and they will crack despite the increased thickness. Aluminium does that.


Titanium works great for pipes if you use the right grade . But stainless steel is almost as good, cheaper and easier to weld.

hey wobbly let me ask something. in EngMod 2T, where it asks for the flow width of the window. if the duct exit and window are the same size and there is no kicker or radius turn at the duct exit, its rather easy to figure the flow width.


But like most cylinders, there is either a kicker or a radius turn just as it enters the cylinder. is there a easy way to get a close approximation of the flow width in this situation ?


Green arrow would be the flow width if both duct walls went parallel into the cylinder. but what if there was a radius or kicker. Would it still be as simple as the blue arrow suggests or is it more complicated than that ?

Where you have an angled exit on one wall like that I use a combination of the flow and chordal width. In reality the port flow area will be very close to the chordal width, as when the flow exits the duct its effective area will be less than a straight flow port, but more than the flow area measured vertically as you have drawn it. In between approximation is the chordal width as I have shown.

Imagine that you have a collection of coins. The diameter of the largest coin that you can shove through the window from within the cylinder bore, is the dimension you are looking for.

Well its sort of like I said, with parallel walls the coin will push into the duct and give you the exact "flow width".


With one wall angled a smaller coin will push into the port, but this gives a smaller flow width, and in this case its the chordal port width. Neels (EngMod2T) code asks for the actual "flow width" and even he says you need some judgement to approximate this where weird angles are involved.


You will know when TubMax is too high ( around 980*C ) as the program will scream DETONATION at you.


On a DynoJet you will need around 12.5% multiplier ( down ) to go from indicated crank Hp in EngMod to RWHp when testing your average racebike.


ONLY a 1 mm change, that is enough to completely ruin any engine - 0.1mm should be an ONLY to everyone - in a KT100 0.05mm in any port size can ruin an engines power.

You will make more power if you have a transition from the 23.7 duct outlet ( this will of course be oval ) up to the 26 pipe diameter ( round ) ie no steps at the joint face.
This is usually around 25 to 30 long and will be the slip joint spigot - this can be inserted into the pipe in front of the header as part of the header length %.

Hi Wob, this is getting into deeper water than I am used to. I worked hard playing with the ignition to get a flat TubMax (squish end gas temperature), but was I doing the right thing, is Ief's red line on this graph more appropriate? I just don't know what a good TubMax graph should look like.

EngMods TubMax is a reflection of the % of fuel energy retained in the unburned end gases trapped in the squishband. The shape of this curve is affected by a myriad of elements but the biggest factor is the real ignition timing.


In a race engine the results are supremely useful for juggling the ignition timing to fix any major anomalies that can produce low bmep at one point or several in the usable powerband. Where you are running what i would call "normal" numbers for timing - say 28* at the bottom of the range and 15* at peak then some further retard to get heat in the pipe for overev capability ,the curve shape will be close to that of the torque produced, a flattened bell.


ie low 900 rising to high 900*C at peak torque then dropping away again as more of the combustion heat energy is dumped into the pipe. You have to be careful of part throttle deto at the beginning of the powerband, and then of course if the temp starts hovering at 1000* in the high power range you will get DETO lighting up on the screen.


To drop the temp it is easy enough to simply retard the timing - but more power may often be had by adjusting the stinger, or reducing the com/squish velocity. Then re-running the Turbulent model to account for the differing flame propagation speed through the chamber due to squish turbulence changing the combustion delay numbers etc.


These factors are just as important, sometimes more - than the "raw" ignition timing number at any rpm point. Each end of the bell curve can be tipped, by use of a powervalve for example,or a solenoid powerjet that is simulated by a change in A/F ratio past peak power.

A huge part of Neels efforts to recreate reality in EngMod2T’s sim results is all around the code needed to model the wave action within the pipe.


A 2T lives and dies on the correct timing and amplitude of the particle flow down the pipe, much as a 4T lives and dies on the intake tracts influence. The latest code change that now has an accurate model of the actual wall temps effects has got the results even closer, without the demon fudge
factors Neels hates with a passion.


The only caveat i would add is that there is still some leeway for idiocy to creep in, and still get a result that seems fine ie 25* diffuser angles. Go back to the old texts and you will find that very early on in the development of expansion chambers it was found that the angle that gave the best energy recovery ( amplitude Vs period ) of the depression communicated to the Ex port during the scavenging phase was 16* included.


This is now modified somewhat in that we can and do have up to 6 different cones. All interacting and changing the shape of the negative pressure ratio plot as seen at the port face when the piston is around BDC, but as is human nature we always think more must be better - even with single malts.


Just keep in mind that any energy used in the diffuser, must then reduce the energy available to be used in the reflection phase - there is only a finite ( and ever decreasing ) energy level available that starts when the piston cracks open the port.

[SwePatrick]

Formula 1 injectors..
Those that they used when their engines revved above 20k

4 of those might work, but they´re to big.
If you use one injector every fourth revolution.

How am i thinking?

4 stroke seqvential injection, one squirt per cycle(720 degrees)
2 stroke, one squirt per cycle.

That would mean one injectors can deliver fuel to an twostroke for 10000rpm.
Just multiply them the get one to squirt every fourth cycle(the second one the cycle after that, the third one on next and the last one on the last, then start over) to get 'closed time' enough to be able to give an exact 'open time'.

[Frits Overmars]

An Ecotrons EFI system for really small engines:- http://www.ecotrons.com/products/uav-engine-efi/

This 'real small EFI system' would double the size and the weight of the engine if the injector could cope with the revs, which it can't.

Formula 1 injectors.. Those that they used when their engines revved above 20k. 4 of those might work, but they´re to big. If you use one injector every fourth revolution.

It might work on a test bench. But the aim is to get the plane off the ground which would become rather difficult with the battery that those four injectors would require. And the whole idea becomes academic when you realize that the total weight of the plane would exceed the permissible maximum.
(There is a damn good reason for a maximum weight; I've witnessed the destructive energy of an F3D model plane hitting something at 360 kmh).

[senso]

why not just pwm an injector ?

Injectors are inductive, and slow to respond, its "easy" to pulse 10A or 20A at 50Khz for example, but the injector wont even move with such frequencies.

[Yow Ling]

Injectors are inductive, and slow to respond, its "easy" to pulse 10A or 20A at 50Khz for example, but the injector wont even move with such frequencies.

Would a piezo diesel injector work?

[FastFred]

.

30,000 rpm = 500 Hz

[Flettner]

A small constant spray system would be useful, for confined spaces within the engine.
You know the Hilborn system? Gear pump connected to the engine, simple, the faster the engine spins the more fuel supplied. There is a return system to the fuel tank with a jet in it, the bigger the jet the less fuel the rest of the system sees. There is some crude fuel control system for idle and low speed running also. I'd imagined that if you inserted an electronic control on this return "jet" you could control fuel flow throughout the rev range. Just like a normal EFI engine the ECU would need lots of inputs like TPS, temp, RPM, etc.

[ief]

I f... one takes a (not so good) carb, placed on a bike with X size (main) jet. Now we flow the carb and we find the jet size goes down...

Does this automaticaly mean better emulsion or is that not to say?

[Frits Overmars]

You know the Hilborn system? Gear pump connected to the engine, simple, the faster the engine spins the more fuel supplied. There is a return system to the fuel tank with a jet in it, the bigger the jet the less fuel the rest of the system sees... I'd imagined that if you inserted an electronic control on this return "jet" you could control fuel flow throughout the rev range.

A bypass-jet will make the system sensitive to the viscosity of the fuel. The obligatory fuel for the model engine I was working at contains 20% castor oil, making its viscosity quite temperature-dependent, playing havoc with needle settings. I wanted to eliminate this dependence so I decided against a bypass.
Connecting the gear pump to the engine would give a fuel flow that rises linearly with engine rpm but that is not what's needed, so I chose to decouple the fuel pump rpm from the engine rpm and regulate the pump rpm via the afore-mentioned lookup table.

[senso]

.

30,000 rpm = 500 Hz

I know, but in a 4 stroke at even 10000 rpm the injector is only working at 83.3Hz, a much lower frequency, and at 10k rpm you are already into "exotic" parts and not stock parts from a car or motorcycle.

[Flettner]

Poor little engine, HCCI test unit. It's going to get a hiding. AG 100 Yamaha, just arrived on my floor.

[Peiter]

Excuse me for the interruption guys but I am amazed by those rpms..

http://youtu.be/yqz2YU7QzEc

[wobbly]

But at 18,000 a 50cc with 39mm stroke has only 23M/Sec mean piston speed, less than an RSA at 13,000.
Its only just getting going.

[FastFred]

.30,000 rpm = 500 Hz

I know, but in a 4 stroke at even 10000 rpm the injector is only working at 83.3Hz, a much lower frequency, and at 10k rpm you are already into "exotic" parts and not stock parts from a car or motorcycle.

TeeZee posted some injector math for his 2T

Performance Fuel Systems has great technical articles about fuel injectors http://performancefuelsystems.com/tech.htm


An injector does not instantaneously snap open, it take a finite amount of time to reach full flow. 2ms (2 thousandths of a second) is the rule of thumb, below that, the flow is mostly non-linear and erratic.

Thankfully its better on the closing side as the fuel injection pressure helps with closing the injector’s needle valve so closing is much more rapid than opening.

A little math ..... 8,000 rpm / 60 = 133 rps x 360 deg = 48,000 deg sec / 1000 = 48 deg/ms

So at 8k rpm the crank turns 48 degrees in one mille second or 96 degrees in the time it takes to open the injector properly (ie 2ms).

2ms @ 8k rpm = 96 deg of crank rotation
2ms @ 10k rpm = 120 deg of crank rotation
2ms @ 12k rpm = 144 deg of crank rotation
2ms @ 14k rpm = 168 deg of crank rotation

So if at 12k rpm it takes 144 degrees (2ms) to get the injector fully open and another 72 degrees (1ms) to deliver sufficient fuel then the injectors pulse width is 3ms and it is energized for 216 degrees which is way more time, than the transfer port is actually open.

30,000 rpm = 500 Hz = 2ms for 360 deg of crank rotation. Just not enough time for conventional Pieco (small) injectors.

[husaberg]

TeeZee posted some injector math for his 2T



30,000 rpm = 500 Hz = 2ms for 360 deg of crank rotation. Just not enough time for conventional Pieco (small) injectors.

Which is why some used GP tems that experimented with Fuel injection in the nineties huge pressure (45 bar from memory)and a duel system that feed on intermintent engine revolutions.