ESE's works engine tuner

[TZ350]

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

High crankcase pressure at idle and lower at WOT. Takes a bit of getting your head around but it is all laid out with pictures in the original post.

I ran some simulated crankcase pressure traces with the minimum in the middle because I wanted to see if there was anything useful there that I could use for my EFI efforts. I was expecting the crankcase pressure to be low at Idle. But to my surprise the crankcase pressure remains relatively high. So how does the motor slow down to an idle with all that air/fuel to burn. my guess is, it can't be air/fuel but pollution.

[TZ350]

So, when a 2stroke comes "on pipe" is it the crankcase having a clean mixture versus a polluted mixture in crankcase?

"On the Pipe" the air is cleaner and the pressure in the crankcase is lower because the pipe is sucking the crankcase down faster than the inlet can re fill it at WOT.

At idle the crankcase pressure is higher, everything has a higher average pressure, inlet, crankcase and pipe. They are all near ambient air pressure.

The engine idles on closed throttle because there is only a small mass of air/fuel passing through the crankcase.

I suspect the crankcase may be highly polluted by back flowing poorly purged combustion products but not entirely sure about that point.

[Vannik]

I suspect the crankcase may be highly polluted by back flowing poorly purged combustion products but not entirely sure about that point.

The software gives you the purity at the entrance and exit of each transfer passage as well as the purity in the crankcase and inlet port.

[Flettner]

run this pressure trace without a pipe, what do you see?
Or perhaps a short stub.

[TZ350]

The software gives you the purity at the entrance and exit of each transfer passage as well as the purity in the crankcase and inlet port.

Good point. I will have a look.

[tdc211]

Just use splash zone in tranfers/Ebay.
Its marine green epoxy. Same shit prostock eng use
In USA for ever. Its not coming out of tranfers. If you preheat a touch and post heat more
.

Now I have mucked up a lot of tranfers.
That being said. On one particular cylinder I was close to ktm new 105 cylinder. In the mid . But I didn't know why. It definitely was the volume/outside and inner radius . And pipe I had on. Everything! Even with not great corner radius in export. Not just one roof angle or something.
It is a whole! You make them 1/2 moon shape and the roof/floor angles just part of that shape. I am convinced this ups the combustion efficiency. I use a feeler gauge . Snip end some. Bend 1/3 to desired root angle . Like a Mason trowel and put the roof angles in as splash zone kinda thick. Then I take a popsicle stick hit on the disk sander at one end (thin) and do the inner/out. and the popstick kinda bends with the radius I am trying to make.
That's after grinding out shit inner 1st.
Then no choice but mold it. To see what you have.
I built the best 105 I ever have. (Which I charged way less $ than my epoxy cylinder 105, cause it was a lot easier) And guy thinks I charged him
To much. I hate mx.

On a side note 10 or 20 degree roof means nothing unless tranfers work. Been there tried that. And transfer blip on blue page in sim is way higher now after the change in combustion efficiency. Trapping is good to.

Here's another thing. I ground out stock floor on one cylinder.
It had a good inner and 25 epoxy roof or so. As soon as that 1/2 moon was ground in the floor. Under the sink the streams where absolutely junk with aggressive floor angle. You make floor straight,streams back to a normal.
So the roof and outer wall is vital here to straighten the streams out with aggressive floor angle. Or the volume.
Idk length a big part to am sure. But I rather be to small than to big.

New cylinder in pic

[TZ350]

.
The straight lines represent the Crankcase purity.

6,000 rpm. crankcase and cylinder similar to each other at 77-97% for the different throttle openings.

9,000 rpm. peak torque and greatest variation in cyl purity 20-98% but CC much closer at 85-98%

12,000 rpm. peak power and crankcase 88-99% Cly 46-99%

So at idle and low speed the crankcase is at its most polluted but not as much as I expected.

At idle only a small trickle of fresh charge is entering the crankcase and although the average pressure in the crankcase is high only a matching trickle of fresh mixture can be moving out the other side to the cylinder because the average pressure is equally high throughout the whole system.

[breezy]

The software gives you the purity at the entrance and exit of each transfer passage as well as the purity in the crankcase and inlet port.

how is the software able to calculate this? what sort of info is required?

[dutchpower]

Just use splash zone in tranfers/Ebay.
Its marine green epoxy. Same shit prostock eng use
In USA for ever. Its not coming out of tranfers. If you preheat a touch and post heat more
.

Now I have mucked up a lot of tranfers.
That being said. On one particular cylinder I was close to ktm new 105 cylinder. In the mid . But I didn't know why. It definitely was the volume/outside and inner radius . And pipe I had on. Everything! Even with not great corner radius in export. Not just one roof angle or something.
It is a whole! You make them 1/2 moon shape and the roof/floor angles just part of that shape. I am convinced this ups the combustion efficiency. I use a feeler gauge . Snip end some. Bend 1/3 to desired root angle . Like a Mason trowel and put the roof angles in as splash zone kinda thick. Then I take a popsicle stick hit on the disk sander at one end (thin) and do the inner/out. and the popstick kinda bends with the radius I am trying to make.
That's after grinding out shit inner 1st.
Then no choice but mold it. To see what you have.
I built the best 105 I ever have. (Which I charged way less $ than my epoxy cylinder 105, cause it was a lot easier) And guy thinks I charged him
To much. I hate mx.

On a side note 10 or 20 degree roof means nothing unless tranfers work. Been there tried that. And transfer blip on blue page in sim is way higher now after the change in combustion efficiency. Trapping is good to.

Here's another thing. I ground out stock floor on one cylinder.
It had a good inner and 25 epoxy roof or so. As soon as that 1/2 moon was ground in the floor. Under the sink the streams where absolutely junk with aggressive floor angle. You make floor straight,streams back to a normal.
So the roof and outer wall is vital here to straighten the streams out with aggressive floor angle. Or the volume.
Idk length a big part to am sure. But I rather be to small than to big.

New cylinder in pic

The volume

[teriks]

"On the Pipe" the air is cleaner and the pressure in the crankcase is lower because the pipe is sucking the crankcase down faster than the inlet can re fill it at WOT.

At idle the crankcase pressure is higher, everything has a higher average pressure, inlet, crankcase and pipe. They are all near ambient air pressure.

The engine idles on closed throttle because there is only a small mass of air/fuel passing through the crankcase.

I suspect the crankcase may be highly polluted by back flowing poorly purged combustion products but not entirely sure about that point.

Are you sure that the average pipe pressure with the throttle closed and at "on the pipe rpm's" are lower than at idle rpms?
I would have guessed about the same, close to ambient. All the rest I tend to agree with.

For sure at WOT, the average pipe pressure increase with power.
Not too surprising given the restriction at the stinger, and also the reason we can use pipe pressure to assist in fuel metering in F3D (or just about any RC related two-strokes).
I don't have a throttle on any of my models, but a quick run @ WOT and a few different RPMs with the pressure transducer in the center of the belly section below:

I doubt that such a signal would be very useful for your injection experiments though.
Perhaps the variation is way too small to be meaningful at smaller throttle openings,
and there should also be a bit delay building the pressure so would be bloody difficult regulating cycle to cycle I guess.

[tdc211]

The volume

Double post.

[tdc211]

The volume

Yes I agree.. Less volume at the floor with a aggressive floor angle. Your sort of taking volume from the floor and putting it on outer radius so it can swoop in. And keep streams strong.
The new 105 has the most aggressive floor angle and least amount of volume I have seen

[Nath88]

I assume 33000rpm is close to resonance teriks? What happens past peak?
I still think the pressure rise after EPO is a great indicator of the following suction pulse (pipe boost effect in general) and therefore next cycle fueling. It worked really well when I tested it, but my ECU couldn't adjust for the delay by RPM vs. crank angle. So it only worked around the RPM range I had it adjusted for. Also the piezo disc I used was too big, so the signal output was huge and it quickly destroyed itself.

Just need to find a few hundred bucks to get the YZ cylinder plated before I can get it running again and continue testing.

[TZ350]

"On the Pipe" the air is cleaner and the pressure in the crankcase is lower because the pipe is sucking the crankcase down faster than the inlet can re fill it at WOT.
At idle the crankcase pressure is higher, everything has a higher average pressure, inlet, crankcase and pipe. They are all near ambient air pressure.
The engine idles on closed throttle because there is only a small mass of air/fuel passing through the crankcase.
I suspect the crankcase may be highly polluted by back flowing poorly purged combustion products but not entirely sure about that point.

Are you sure that the average pipe pressure with the throttle closed and at "on the pipe rpm's" are lower than at idle rpms?
I would have guessed about the same, close to ambient. All the rest I tend to agree with. For sure at WOT, the average pipe pressure increase with power.

No, I was looking at the crankcase pressures, although I did look at the pipe some time ago and what you say about it makes sense.

I would love to know more about your pressure transducer. It sounds like something I could use if its affordable.

[TZ350]

So, when a 2stroke comes "on pipe" is it the crankcase having a clean mixture versus a polluted mixture in crankcase?

Yes, 98% clean mixture at WOT and 9,000 rpm, 15% polluted with only 85% purity at minimum throttle and 9,000 rpm according to this simulation of my engine.