ESE's works engine tuner

[wobbly]

I am REALLY interested in the flow method of checking actual port power capability.
And cant wait for you to show some results from this.
But as I have said before, lifting a cylinder only increases the Exhaust and Transfer STA but as in the example shown the Blowdown is actually reduced.
So how can we trust this result from the software unless its dyno proven.
Also what is the venturi connected to in the pic that gives the flow info i assume ?

[Flettner]

maybe" true" hcci is still a dream away, but maybe new ideas of better si combustion will come from the hcci challenge..... still interested why your hcci test engine suddenly screamed to high rpm before it died...

I guess it went like this, compression is ignition, so if it stops running at higher rev's it must be running out of compression, or at least enough to initiate combustion. So as the revs climb the ability of the crank case pump drops off to a point where there is just not enough compression rise to set of combustion, so the rev's drop until the cycle can start again? Maybe? As for the high speed takeoff in the end I think by that time the little piston is hot enough to 'pick up the ignition' where the compression only left off. It would seem we might need to control the small piston temp? and / or keep the volumeric efficiency up at high speed. I'm sure a tuned pipe will help with this requirement.
I assuming the compression rise on my crude test engine is just enough to initiate combustion. I have a new version that will have much better control over the ignition compression rise.

[Ocean1]

I guess it went like this, compression is ignition, so if it stops running at higher rev's it must be running out of compression, or at least enough to initiate combustion. So as the revs climb the ability of the crank case pump drops off to a point where there is just not enough compression rise to set of combustion, so the rev's drop until the cycle can start again? Maybe? As for the high speed takeoff in the end I think by that time the little piston is hot enough to 'pick up the ignition' where the compression only left off. It would seem we might need to control the small piston temp? and / or keep the volumeric efficiency up at high speed. I'm sure a tuned pipe will help with this requirement.
I assuming the compression rise on my crude test engine is just enough to initiate combustion. I have a new version that will have much better control over the ignition compression rise.

I has a silly question. Is it possible that a spark plug initiated combustion event at some stage through the combustion process could increases pressure to the point where compression ignition immediately completes the job?

If so isn't it likely that there are existing engines that fall into that category?

And is that an effective way to manage the timing of the event so that it remains safely on the after tdc side, while offering most of the advantages of HCCI?

[marsheng]

Just in case this has not been posted before

Direct injection 2 Stroke

http://www.snowmobile.com/products/f...600s-1775.html

Some interesting piston shapes.

[Flettner]

I has a silly question. Is it possible that a spark plug initiated combustion event at some stage through the combustion process could increases pressure to the point where compression ignition immediately completes the job?

If so isn't it likely that there are existing engines that fall into that category?

And is that an effective way to manage the timing of the event so that it remains safely on the after tdc side, while offering most of the advantages of HCCI?

Absolutely, I think many engines fall into this category by accident. If Ryger had anything to believe, listen to the video of the cart running up and down the short road test. Even though the sound has been buggered up, it's quite obvious the the engine is struggling down low in the revs (worse than a standard engine I think), very retarded ignition timing. Assuming the high pressure crankcase pump has something to do with 'conditioning / homogenizing ' the fuel air ready for a quick burn event, compression is low and squish is minimal, then once the plug ignites the fuel air the pressure rise is such that it goes to self ignite condition shortly after, with a bit of luck just after TDC or there abouts. You are right I think.

Still tricky to control with a throttled engine.

[Ocean1]

Absolutely, I think many engines fall into this category by accident. If Ryger had anything to believe, listen to the video of the cart running up and down the short road test. Even though the sound has been buggered up, it's quite obvious the the engine is struggling down low in the revs (worse than a standard engine I think), very retarded ignition timing. Assuming the high pressure crankcase pump has something to do with 'conditioning / homogenizing ' the fuel air ready for a quick burn event, compression is low and squish is minimal, then once the plug ignites the fuel air the pressure rise is such that it goes to self ignite condition shortly after, with a bit of luck just after TDC or there abouts. You are right I think.

Still tricky to control with a throttled engine.

Be nice to have some actual numbers from some of the engines that've been built that made more power than expected. And yes, I can imagine the sound would be a giveaway.

What actual pressure are we talking, here, for ordinary petrol?

What would the above process mean for spark timing? Would need to stay at or about tdc right through the rev range wouldn't it?

And tricky in what way? Is your experience with run-aways from residual fuel in the crankcase/ports? If that's not easily resolved you'd be right back to direct injection wouldn't you?

[Frits Overmars]

I am REALLY interested in the flow method of checking actual port power capability.... But as I have said before, lifting a cylinder only increases the Exhaust and Transfer STA but as in the example shown the Blowdown is actually reduced. So how can we trust this result from the software unless its dyno proven.

I too am really interested in this approach. You may recall that I proposed substituting the calculated flow areas by measured flow capacity numbers in EngMod.
Lifting a cylinder does reduce the blowdown angle area because it will increase the number of transfer timing degrees more than the number of exhaust timing degrees. The Torqsoft website quotes 0,00132 and 0,00130 respectively, a 1,5 % reduction, and that ties in with what I found, using their dimensions. But while their quoted exhaust timing values may be correct, their quoted transfer timing values are way off, so I too wonder how we can trust their software, though for a different reason.

[ief]

Other end of the spectrum but still, have to ask, any reason this portshape is as it is?

even the 'higher performance' cylinders have those and I wonder what benefit they could have?

(old school, 2 transfer ports barrel)

[wobbly]

Assuming you are describing Aux Port shape ( or Hook Port as the Mericans call them ) the triangular shape used in a hi performance
cylinder is like that for a couple of reasons.
The top edge chordal width is greater than the duct width, but as this upper edge opens first the pressure differential is greatest and we get the maximum flow
ability in the upper 1/2 of the port opening, where the port area matches the duct area for maximum exit velocity.
As the piston moves down past the 1/2 height point, the Blowdown pressure is alot less, thus the flow rate reduces, so we dont need anywhere near as much area to keep up the flow needed.
Then there is the issue of vertical short circuiting from the A port window.
Only having the front corner down near the A port, reduces the tendency for the A ports flow column to do a U turn above the timing edge and exit thru the Aux port.
The same applies to the port linking area presented to the passing small end pin cavity.
The rear corner of the Aux port that is closest to the pin hole, has a much reduced area, and is well separated in distance from the A port, so there will be much less linking time area
thru the pin hole cavity.

Re the real port flow capability.
If we look at the raw numbers of the Aprilia in EngMod is would seem that the Transfer STA is excessive in relation to the Blowdown numbers.
But this is taking no account of the big radius on the timing edge of both the Ex and Aux ports.
Thus the effective Cd numbers for the Blowdown is much improved, and this is accounted for in the scavenging model that was presented in an SAE paper from I think the Uni of Valencia.

[ief]

No, it's the transfer, sorry

it's less pronounced then I drew it but still. And this is the opposite of ' tuned for max performance'

Tnx anyway for the aux port shape exlpanation, the more info the better

You probably answered it allready with:

'As the piston moves down past the 1/2 height point, the Blowdown pressure is alot less, thus the flow rate reduces, so we dont need anywhere near as much area to keep up the flow needed.'

Would that mean that in this case flow in the transfers is kept higher to help in the lower revs giving up some sta for higher revs?

[Flettner]

Be nice to have some actual numbers from some of the engines that've been built that made more power than expected. And yes, I can imagine the sound would be a giveaway.

What actual pressure are we talking, here, for ordinary petrol?

What would the above process mean for spark timing? Would need to stay at or about tdc right through the rev range wouldn't it?

And tricky in what way? Is your experience with run-aways from residual fuel in the crankcase/ports? If that's not easily resolved you'd be right back to direct injection wouldn't you?

I think I was wrong, the HCCI engine did not run away due to residual fuel, I'm sure it's compression/heat (small piston heating up) related somehow.
HCCI opperation is a function of heat and pressure, which changes dramatically throughout the a normal engines running conditions/throttle settings. This would require a constant compression change to avoid detonation but still allow for HCCI combustion. Every crack of the throttle would change these conditions and need compression/timing adjustment. I guess doable.
I think with my test engine as it is, if I fitted a sparkplug as well (as Frits said) this would help with the conditions where the compression just falls off ie at high rpm where the crank case runs out of puff.
My engine was designed to raise the compression ratio to approx 21 to one if it were a full cylinder volume but with the exhaust port spilling out half before compression begins, I'm probably a few ratios short on compression in the real world, if you know what I mean
My latest engine has a bigger combustion piston and a little longer stroke so quicker rise time. This engine at least has some control via the spray gun fueling system, I can modulate it's revs with the trigger although still hairy. I have a clutch fitted and it's ready to be hooked up to the out doors dyno when time permits.

[philou]

it's the transfer,

?

usual, the delta transfert ports in the other direction

[wobbly]

The normal triangular max performance A port geometry is there to allow more room for the Aux, and to increase the wall area next to the main Exhaust to
prevent short circuiting.

[ken seeber]

Been thinking about HCCI a bit more. Seem that it is a part load thing only. One thought, say if you wanted 20 hp (under HCCI control because of the low emission and fuel consumption benefits) and your engine was 20 hp, then no go. Then give the engine to the WWW (Wobbly’s Wonderful World) and it comes back with 40 hp. So, could you then run the engine at its 20 hp part load point and then expect HCCI to kick in? Not likely.
After talking further to some ex Orbital cronies, it is clear that HCCI just needs temperature. In a 2 stroke, this can be accomplished with high levels of retained exh gas. In a 4 stroke, similarly using high levels of EGR. But, to get more power, amongst other things, the WWW crew strive to trap more fresh mixture in the cylinder at the time of exh port closure. The problem is that this is cool, not conducive for HCCI.
Dunno where this is going, but maybe HCCI could be promoted at higher load by being able to increase the gas temp after EPC. The big risk here is deto. Could be that Fletto’s auxiliary piston, that is phased early in the compression stroke, might be the go initiate HCCI prior to the conventional spark timing.

[peewee]

with triangle aux you can also drop the forward portion below the A transfer top but don't go so far as to break through the roof. a lot of cylinders especially older ones use a flat A roof so it will be easy to break through if you don't pay attention