Let's discuss larger nozzles and idle quality

Chvyrkr · May 2, 2012

Different PCM's or CPS's maybe?

Charles · May 2, 2012

Compression...

I bet it's the 17.5:1 vs the 14 or 15 or so for my truck. Well hell, actually, my 550 is 17.5:1 too, and it sounds good. Course it only has 100% nozzles.

TARM · May 2, 2012

Doesn't lower CR also help with reduced emissions or at least lower NOX. You have lower heat there for lower NOX and the lower CR supposedly allows for a more even fuel to air mixture.

IIRC the new Mazda diesel is dropping all the way down to 14:1!!! It will meet all Europe and US with no after treatments only a DPF. The CR is interesting given that is what they raised their gas engines too so both are running the same 14:1 CR!! With HCCI on the gasoline side of things right around the corner it looks like spark plugs are on their way out.

The new 2.0L D engine has a 5600 rpm limit and is suppose to pull down 40 mpg in the full size car M6 It will even be offered with a manual trans.

Charles · May 2, 2012

TARM said:
Doesn't lower CR also help with reduced emissions or at least lower NOX. You have lower heat there for lower NOX and the lower CR supposedly allows for a more even fuel to air mixture.

IIRC the new Mazda diesel is dropping all the way down to 14:1!!! It will meet all Europe and US with no after treatments only a DPF. The CR is interesting given that is what they raised their gas engines too so both are running the same 14:1 CR!! With HCCI on the gasoline side of things right around the corner it looks like spark plugs are on their way out.

The new 2.0L D engine has a 5600 rpm limit and is suppose to pull down 40 mpg in the full size car M6 It will even be offered with a manual trans.

Most of the OTR tractor engines have been 14.0:1 forever. Our bone stock 3406 in our tractor is 14.0:1.

This is one reason I didn't even hesitate to drop my little 7.3 down to that level. It's somewhere around 14 to 15 now.

Gearhead · May 2, 2012

Pocket said:
I haven't datalogged my truck yet with the new changes, so I'm not entirely sure where the idle PW is actually ending up at. But as always I can set values how I want, and the truck does its own damn thing when it feels like it. That's the one thing I've noticed about the PW table. I can almost set whatever values I want, it doesn't care. I get more changes out of that table if I adjust the curve or slope of the fueling, how quickly it rises and falls... or doesn't.

For example, my last two major tuning adjustments before starting this thread had two entirely different PW tables, but much of everything else was identical. In both cases, the PW at idle rested at around 1.45ms, even though the tables had completely different values. But the idle characteristics were both different, how they came off idle as well as how they came back to resting idle after driving. Also warm starts were affected, as a flatter PW table had a harder time settling into an idle after cranking.

Currently the idle ICP is down below 450psi, down from my other files of close to 530psi. Base idle speed is up to 750 RPM's.

Mine is also set to 1's across the board too

And I was having a bit of issue with ICP climbing rapidly as RPM's came off idle, but not coming on with the fueling. The result was a choppy feel at light throttle. So some of that has been pulled back a bit. Now I can watch my ICP gauge in the cab climb more with fueling rather than with RPM's.

It is a fuel throttled engine...... If 1.45 ms of pw is what it wants to maintain idle that thats what it is going to run. What will be affected by the pw table is the mfd at idle and where in the timing table you are at idle...

TARM · May 2, 2012

Charles said:
Most of the OTR tractor engines have been 14.0:1 forever. Our bone stock 3406 in our tractor is 14.0:1.

This is one reason I didn't even hesitate to drop my little 7.3 down to that level. It's somewhere around 14 to 15 now.

I knew the tractors were low as the ones on our farm have always been. Did not know that about the OTRs but it makes sense. Its the smaller engines and the ones in our trucks that have always seemed to be higher. I do find it interesting that as there is more control of the combustion event gas engines are going higher and diesel in this sector are coming down.

The lower CR would also increase MPG as there is less opposing force?

Charles · May 3, 2012

TARM said:
I knew the tractors were low as the ones on our farm have always been. Did not know that about the OTRs but it makes sense. Its the smaller engines and the ones in our trucks that have always seemed to be higher. I do find it interesting that as there is more control of the combustion event gas engines are going higher and diesel in this sector are coming down.

The lower CR would also increase MPG as there is less opposing force?

Picking a compression ratio is a lot like picking a nozzle or a camshaft profile. An engine designed to run at part load the vast majority of it's life needs the static compression ratio to be relatively high, so that efficiency is good under those low power, low boost conditions. The efficiency at full power is a bit lower because of the pumping losses of the extra compression when there was plenty of boost for the needed cylinder pressure at higher power levels.

An OTR engine is desgined to run at near, or actually at full load nearly the entire time. So it doesn't need to focus on low power efficiency. So they drop the compression ratio, and the boost brings things back in check under power. They are not efficient at part load though, where they rattle and blue smoke due to lack of cylinder pressure when off boost.

A high CR engine is focused on low power, off boost efficiency. A low CR engine is focused on high power, on boost efficiency.

powerstrokenstang · May 3, 2012

Mine seems pretty efficient at high cr full load:shrug:

TARM · May 3, 2012

You have a good size turbo and large nozzles both I think help with that especially at cruising speeds. Little if any drive pressure and the fuel deliver is stupid fast with that minimal volume. Maybe even better efficiency if the CR was dropped a couple points but I hear ya. Its one of the things I love about these diesels.

Even with my engine not running quite right I still picked up a bit of mpgs from stock with gtx42r 200% hybrids I love diesels the more power you add the better mpg they get if you are not into the go pedal. LOL

I got to say that 5600 RPM of that Mazda 2,0L D engine was impressive and the tq curve I saw on a site was very smooth after jumping up quickly. Getting into general use gasser territory with those rpms