Hi all,

Interested to here some opinions on the following EOI graphs. Safe or Dangerous ? Better or Worse ?
[NB This is a Honda 2.2 Diesel engine with offset crank]

The OEM graph is the end of injection in crank degrees using existing rail pressure and duration for the calculations.
The graphs is based on Crank degrees, IQ in mg/stroke and RPM. The EOI is pretty much all over the place although a rough pattern can be seen.

The MOD graph is the end of injection by a test formula that automatically optimises the SOI using existing rail pressure and duration vs rpm.

Where you see the EOI fall rapidly toward the end of the graph, is where the SOI has hit the SOI limiter. In the case of OEM it has been artificially set at 35.79 BTDC. For the case of the MOD graph, I wanted to get 70mg of fuel at 4000rpm without hitting the SOI limiter. So the SOI limiter was raised to 38.15 degrees BTDC. This explains the falling tails at high rpm that dont quite line up between OEM and MOD as the EOI isn't impacted so much by the SOI limiter.

Anway, like I said....opinions appreciated.

Do you take into account the ignition delay?

biela wrote:Do you take into account the ignition delay?

Nope. Got any calcs for that ? Ones that are accurate and not simulations.
Way I see it, theres currently about 100 variables you have to throw in the mix to chuck out a fudge factor :/
I was hoping someone with dyno experience would explain how much + or - crank angle leeway you have from oem.

Some people have no qualms about 2 degree shifts. Some people have kittens if you mention more than 0.2 degrees.

It troubles me that EOI for 35mg/stroke should hit almost 15 degrees BTDC at high rpm

I have no dyno experience, sorry.

I am planing to do calcs with the following document:
"Experimental investigations of ignition delay period ...."


With the Arrhenius equation.

Many thanks for the document. You are a saint. I will delve into that now :D

Relic wrote:It troubles me that EOI for 35mg/stroke should hit almost 15 degrees BTDC at high rpm

Looks like ignition is delayed by a fair amount at this particular area.

In order to avoid high EGT, I'd try to set EOI no later than 10 degrees ATDC.

Like you said, ignition delay depends on many different factors, so the easiest and most accurate way is a dyno. Unfortunately it takes time and costs money. Flashing my Mondeo takes 13 minutes each and every time, and dyno hours are not cheap. :|

Thanks for the advice Zok.
There is an added complication on mine which I have started delving into.
The crank is offset 6.5mm
:?

If 0 degrees crank is considered to be when the crank arm is parallel with the cylinder bore.
TDC occurs at -2 degrees.
The conrod is centred down the bore at -6 degrees to eliminate side load on the piston.
BDC occurs at -184 degrees
So induction/combustion strokes are 182 degrees, compression/exhaust strokes are 178 degrees of crank rotation.
:eh:

Now I don't think there is anyway crank sensors can vary there time.
Cant really have a long degree and a short degree.
So SOI must be relative to crank degrees and not stroke completion.
So the problem is ....is 0 degrees TDC or is the 0 degrees when crank arm and cylinder bore are parallel or is 180 degrees BTDC
:wtf:

..regarding dyno time sucks...
Anyway, I am trying to build a "universal" cylinder simulator of offset crank at the moment.
The hard part was getting the geometry right.
Have to do the compression, pressure, temp and delay still.

Manufacturers often use delayed injection at cruising RPM for decrease NOx and use hole in Rail Pressure map at this RPM for slow combustion. After cruising RPM rail pressure rice as pike for give car good ricing and SOI/EOI optimized for performance more that for ecology in this area. This give strange shape of SOI/EOI if see this maps separately from RP map.
And we must keep in mind pilot-injection that strong modified ignition and combustion and made calculations complicate. Pilot-injection can switch off at same RPM and give SOI/EOI jumping.
For understanding and calculations we must see RP, SOI/EOI, pilot-injection and duration maps in complex, not separately.

Program Diesel-RK allow modeling ignition and combustion processes.

Thanks Alex.
On the diesel rk software.
I don't use any apps that work on client server basis.
I don't open doors through my firewall for complete strangers.
If it was as a standalone app.....I would probably give it a try.

So......in the meantime I will carry on trying to build simulation myself.

Rail pressure and boost are quite low also to keep pumping loses as low as possible - i mean for lower exhaust backpressure and lower injection pump's mechanical power consumption...

I didn't notice that you're talking about crankshaft offset - i thought you were talking about camshaft angular offset.. :? umm, I guess piston is at the TDC when crank arm and connecting rod are parallel - when main bearing, big-end bearing and small-end bearing are aligned into one straight line... :eh: ...and I guess ECU's firmware is made so that 0 degrees in program should be TDC, otherwise making a firmware would be an engineer's nightmare... :?

You can turn it the other way around: a crankshaft has no offset, it's the cylinder bore that is rotated for some degrees by transverse axis.. :mrgreen: