This is the way we can get more area under the curve.

Notice that the end that changes most is the leading peak pressure end.

If you could view each firing of the rotor it would look similar to some of the five curves shown with not much movement of the trailing tail.

Barry

 

Good news and bad news.

As the mean effective pressure has increased through changes in timing a new problem has arisen. Preignition!

The in-chamber testing can show us the beginning of combustion pressure from the small ignited kernel of flame front, but it is so small at first that the pressure change usually only shows an increase after about 5º of eccentric movement (15º BTDC advance starts showing pressure at 10º BTDC). Imagine our surprise when we started seeing a pressure rise starting at 28º BTDC!

The crazy thing is that it made more power and no real detonation!

Barry

 

So, the higher bhp can likely be attributed to the earlier and higher CP right... (851 @ 40ATDC vs. 663 @ 54ATDC)

So, can we assume that if you were to run higher octane fuel, and run more ignition advance (closer to the 28* BTDC of pre-ignition that you experienced) that you might be able to replicate the results using controlled combustion?

Secondly, is pre-ignition as "capable" a starting force on a combustion event as spark ignition is? In other words, could running less advanced then 28BTDC (but more advanced than 15*) while eliminating the pre-ignition replicate the results?

These are rhetoric questions btw, god I love this thread.

 

^^ In this graph, what was the actual ignition timing? 15 degrees BTDC? but there are signs of preignition at 28 degrees BTDC? when are the trailing plugs firing?

Are you saying that the more advanced timing overall is not causing detonation (unwanted combustion after plug fires) but is rather leading to preignition on subsequent combustion cycles?

 

Trots and Arghx, great questions.

The real question may be… do we try to eliminate the reversion causing auto ignition or try to control it with some type of valve?
I think Honda has the answer with their two stroke experiments into Active Radical Combustion.

“When the spark plug fires and ignites the fuel mixture, some of the fuel is isolated from the resulting flame by the exhaust still in the cylinder, and does not burn. What Honda has done is to develop a way to ignite all the fuel in the cylinder by using the properties of auto-ignition, and has termed this process Activated Radical Combustion. This title is derived from the way fuel actually ignites. When the fuel is brought to the right pressure and temperature, the molecules break down into what are known as active radical molecules. These are highly unstable chemical compounds which are an intermediate step in the actual combustion reaction. When hot exhaust gas remains in the cylinder, it contains a small percentage of active radical molecules; when these are combined with the incoming fuel charge, the resulting mixture begins to auto-ignite at lower temperature that a pure gasoline/air mixture. What we currently associate with auto-ignition is engine knock, a phenomenon that occurs when the fuel ignites before the spark plug fires, while the piston is still on the up-stroke”

I am working with a Gorilla (Jonathan) and a Trout2 (Jack) on this project.

Thanks for your input, we learn together,
Barry

 

What your describing is called EGR (Exhaust Gas Recirculation)

This is not new technology in the diesel industry and has been an effective technology to improved diesel emissions for the last 10 years.

Main issue with EGR is cooling the exhaust gases enough be safely re-enter into the intake charge and not cause excessive auto-ignition.

 

http://en.wikipedia.org/wiki/Exhaust_gas_recirculation

http://www.autoshop101.com/forms/h61.pdf

http://www.asashop.org/autoinc/nov97/gas.htm

http://www.aa1car.com/library/egr.htm

 

EGR is an emissions component designed to reduce NOx emissions during cruise on gasoline and diesel vehicles, Barry is referring to in-voluntarily left behind exhaust gas due to port overlap in rotary/2-stroke engines, and its effect on the subsequent combustion cycles.

 

Mazda described that as simply "unstable combustion" due to the overlap. They solved it by eliminating overlap altogether.

Reminds me of some of the direct injection fueling strategies.

 

EGR ultimately does reduce NOx via creating a controlled Auto-ignition. Your right this is done in a cruise/steady state condition, but if done right and with a proper fast reacting valve EGR could effectively do what Barry describes in a controlled manner.

I wouldn't want to relying on uncontrollable in-voluntary exhaust gases left behind via port overlap.

 

Exactly

Adam, that is exactly how I feel.
But I didn't know that we had this going on before this new instrumentation. I was just fat dumb and ugly rolling along (well maybe not fat!).

I thought everything was great with my setup. Nice conservative 12psi boost, a little less than 400 hp.

Then I added dual EGTs and found I was running nearly 1050ºC on my front rotor.

Now I add pressure sensors and I find that we are experiencing auto ignition in some rpm ranges.

I have to ponder the problem a little more.
Thanks for your contributions.
Barry

P.S. Adam did you see the water fittings on Big Al's three rotor build. Looks similar to yours but I think he just threaded the fittings into the housing.

 

1050C is about 1900F... that is pretty high. 1700-1800F I can see, but getting over 1900 is really getting up there. Of course it does depend on how close to the exhaust port you are measuring it. What hotside do you have?

 

I ran all last year with 1850*F on my rear rotor and would run 30 minutes sessions of continuous WOT at the track with multiple sessions and multiple track days. Car took it like a champ minus the grinding away of the turbine housing with my turbo blanket on. This year its not as high, probably due to the larger A/R ratio (500R-SP (0.84 A/R I think) vs billet PT6765 /w 1.0 divided)

thewird

 

As I understand, you are using divided cast manifold. Each runner has different length and mainly, different mass. So assuming same conditions on both rotors, you are not going to get same EGTs.

It would be very interesting if you hook up exhaust back-pressure sensor.

 

Good to know

 

HKS cast divided to 1.00 housing with the probes 2" from the exhaust port flange.

Liborek, if you notice the EOP at the bottom of the cycle results it shows 132psi on one and 143 psi on another when the exhaust port opens, but averages would be interesting too. It would show how well it flows through the turbo and beyond.

Barry

 

Adam, if you look at the data provided by Honda the first two charts they are exact duplicates of runs made on my rotary using in-chamber sensors.

Honda produced 27% better fuel economy using no external ignition source. The 400cc two-stroke developed the same torque as their 870cc four-stroke but got better mileage and was 110 lbs lighter. (Note that it only worked well to 60% power than regular ignition was put back in charge.)

If Mazda would incorporate this instead of side ports and use it in conjunction with direct injection the rotary could keep its performance edge with better mileage and lower emissions. I think this would be a better way to go with the 16X.

But sadly this is not the road that we should follow. I think we will have to try to eliminate the auto ignition. Who can we talk to at Mazda?

Barry

 

Mr. Downing may have a contact within the rotary engine R&D department.

And it seems AI is the key to eliminating auto-ignition. For both rotary and auto-cycle engines.

From what Honda say's on this article a 2 stroke motor with this auto-ignition feature would lend itself nicely in a generator environment wouldn't it.

 

Barry

 

You know, I never really thought about it in depth how EGR reduced NOx, which is emissions caused by high combustion temperatures I believe right? I was under the impression manufacturers used the spent exhaust gas just to take up combustion space, leading to better fuel economy without running lean (causing more NOx due to heat). Interesting...

Agreed, but with porting there seems to be no way to avoid it, unless we were all to run Renesis-style side exhaust ports with no to minimal overlap. I know that's not happening any time soon, so the question may not be how to control it, but how to work around it safely, and what affects it.

 

AI -50/50 HOH Meth

 

Bumping this up, any updates for us Barry?

 

Trots, I have gotten lots of good info on ignition timing. Both when and how much split. IMEP (Indicated Mean Effective Pressure) has gone up about 20%. We just need to confirm the results with more testing.

Little things have been slowing progress...
-To help standardize the tests I added new sparkplugs, this lead to a reopening a water leak at one of my housing cooling mods.
- My 3 bar MAP sensor seemed to be intermittently giving erroneous readings... replaced the GM version with the plug in Denso unit.
-I ran out of meth and my supplier now only sell drums. Jonathan (GorillaRE) found another source.
-I had to change my standard Chevron 93 oct. fuel because they added 10% ethanol in the middle of the tests. Switched to Exxon 93 oct.
-now my optical pick-up threw it's target and I am in the process of making a new one.

Barry

 

Not so; EGR functions by diluting the air/fuel charge with inert gases.

It has the same basic function as water injection, to the point that some manufacturers (Volvo, possible others) are using EGR to allow stoich operation under boost.

Why not water injection? You never run out of exhaust gases with the engine running.

 

Spot on Peejay.

They cool the exhaust gas for that purpose so it doesn't cause autoignition (will become a mute point to a degree with almost all diesels common rail injected & SI engines going DI too), by providing for a greater mass of pumping fluid you reduce combustion temp(which reduces NOx production) & running temps & improve efficiency at cruise.