+1

 

This is my favorite thread on the whole forum. keep up the good work.

 

Peejay and Slides,
That is the common knowledge. Sometimes there more is going on in this complicated combustion process and it is not an either/or proposition.

Most ERG systems promote better MPG. Could the active radicals introduced by the EGR valve be causing this through better combustion? I doubt that the inert gas portion can help much except to reduce pumping losses.

Barry

 

i believe the economy lift is due in part to having the non combustible recycled gas replace the extra fuel normally added for boundary effect cooling and intended to remain unburned
-which as you know was the traditional strategy in controlling combustion temperatures at load in petrol engines

its a two birds,, one stone method ( or rather three birds )
,, with the EGR method,, they control combustion end gas temperature ( and n20 emissions )
and reduce unburned hydro carbons
all whilst increasing economy over the older traditional method


on a side note-
all this talk about dieseling and auto ignition reminds me of a motor i had a while back in the rx2
i used to run two different combos of 6 port turbo engine in it
one more radical than the other ,, as it went in for race days at the drag strip

this one i hurt lots ,, it had a habit for eating rear stat gears and crunching rear corner seals
the culprit in the end proved a slight wobble in the crank,, but i digress...

when its day had come and it had finally chipped an apex seal
i limped it home,, with both rotors still running at idle, albeit a very low and loopy one


when i got home,, i left it to idle as interest as to how long it would go before stalling out

it wouldn't,, instead getting to an almost imperceptible loping 200 rpm on the tacho

intrigued,, i pulled off the ECU connections to the coils

AND IT STILL RAN


not only did it run,, it stayed running ,, i had to stall it against the clutch !


you can imagine i was rather amazed at such a feat,, and i am kinda pissed back then no-one had a digital camera to record it


so,, what magic happened here?
well the ECU was a micro,, it was still seeing a CAS,, and still sticking in the fuel timing it saw in the idle fueling table
the plugs where normal,, no glowing self made glow plug
the rear housing proved to have chipped a seal
and the subsequent groove left in the housing was in the compression / combustion zones
-- substantial inadvertent and very hot EGR was causing some sort of "standing wave " combustion on that rotor

 

Why is reducing pumping losses not sufficient to explain the increase in economy?

Is that not, after all, where most of the Diesel engine's efficiency comes from?

 

I agree that it will help but consider the flow into a diesel engine operating unthrottled vs. the flow through a EGR valve. I think we would need a lot more flow to reduce pumping losses significantly.


Today my question for all you great thinkers is "What can be causing the our auto-ignition at 25-30º BTDC when the timing is set a 15º BTDC ?"
Barry

 

increase in charge temp due to compression (you have effectively reached full dynamic compression, the rotor itself is only 10* from TDC) + glowing carbon deposits on rotor = spark free ignition.

 

This is an excellent thread!

I'm curious, is there any reason the 2 photos at the beginning of the thread show the rotor at BTDC positions, rather than ATDC? Or was it a simple illustration of angle?

 

Have you tried colder sparkplugs? Surely chamber temps are higher due to the increase in ignition timing, maybe just high enough to cause the plug tips to glow a fraction more, or carbon deposits on the rotor as mentioned above.

On a side note, I know of a 13BT that made about 50hp more on the dyno than it should have (480hp), due to RFI from bad plug wires. Once the wires were changed power dropped to a normal level. So I'm wondering if pre-ignition was present and gave the abnormal power increase??

 

the one thing you don't have a direct measure on


-- the proportions of the recycled end gas V the new fuel mixture
( and potentially the end gas composition as honda hint with the free radical talk )

lots of supposedly inert ( but methinks perhaps potentially catalytic )
very hot torch like gas,, meets highly stratified and unstable fuel pockets

but when they do so,, the flame kernel is much faster and burns to the outer edges quicker, instead of along the chamber longitudinally as normally expected
hence the rise in TQ as there is a more completed burn before the maximum crank position

evidence i think that honda would indeed have actually answered mazda's hardest task,, complete and fast burn in a historically difficult chamber shape
- provided the engine is built to take the stresses

time to lower the exhaust backpressure i think, not to sure you should continue to push that one
- dont think this current engine design will take the thermal stresses too long

 

Today my question for all you great thinkers is "What can be causing the our auto-ignition at 25-30º BTDC when the timing is set a 15º BTDC ?"

Unburned gases from the previous combustion cycle mixing with the fresh air/fuel mixture. As they are compressed, they combust, in a not so controled fashion.

 

Good catch JZG. I am very dyslexic at times. Use it for angle comparison only.

This would have been a good engine to put the test equipment on.

You hate to remove 50 HP with new wires.

Barry

 

My problem right now is that my laptop is to slow for the TFX system.
I need a old fast (2GHz) laptop that has PCcard port and using Windows XP.
Barry

 

Restarting testing with a revised thermally shielded sensor from TFX.

As an update to the "latest experiment failure" thread.... thought I should update this one too. The engine is still running well after 3 years of testing. I do have to re-Loctite the plug (on the leaky housing) at each spark-plug replacement.

During the latest run we broke 1000 psi chamber pressure for the first time (10 lb wastegate spring goes to 12psi).

Barry

 

one possible explanation, we saw this when my friend dynoed. he had his map sensor teed into one runner, and this was fine up to 6500+ rpms, when the pressure signal got very unstable. when the pressure signal got unstable, the engine output got unstable, and it threw the dyno off.

we were seeing a very wavy 195hp! we swapped nipples, and the number on the dyno chart dropped to the 140s....

the dyno measures accelerations so the up and down output threw it off.