performance module

BlackLibertyCRD · **Posted:** Fri Feb 08, 2008 9:51 am

The chip I have don't increase fuel pressure but fools the ECM to increase pulse of injectors and increase timing. There is more to the pressure sensor and the aftermarket chips that meets the eye.

gmctd · **Posted:** Fri Feb 08, 2008 12:16 pm

Sir, I categorically deny any and all inferences to any insight, nor do I have any recollection of any improprieties with that injection pump and fuel rail, no matter how briefly they may, or may not have, occured..........

FYI - high Rail Pressure has several purposes: the window of opportunity for the injection event is wide at low rpm, becoming increasingly narrower as rpm increases - very narrow at high rpm, the full volume of fuel must get thru the injector and into the cylinder quickly to allow the comparatively slow Diesel combustion process to play out - increased pressure satisfies that requirement, quickly forcing the required volume thru the injector - increased pressures result in improved spray pattern and finer mist, enhancing the combustion event - increased pressures ensure sufficient volume to meet any\all increased demand, within the prescribed limits of the system.

Max pump pressure is not determined by the ECM - max Rail Pressure is determined by ECM in the Jeep CRD* - max mechanical pump pressure is determined by Bosch, on the production line - max Rail Pressure is determined by Bosch, in the ECM - our 2.8L CP3, and the Cummins 5.9L, and the DMax 6.6L, are all upper-limited to 23200psi by an intricate system of contrivances and gadgets inside the CP3 - (FYI the '07.5 Cummins 6.7L gets a new CP3 pump, set for ~26000psi max - some unit-injector systems are already at 28-30kpsi) - Bosch has new CP3 pumps ready for 28-30kpsi, requiring ceramic injectors - if you installed one in the Jeep CRD, it would put out max 23200psi to the rail, because ECM monitors and controls that with the Rail Pressure Sensor in the rail and the Fuel Quantity Solenoid in the CP3, and, in the Jeep systems, will vent off any excess thru the Fuel Pressure Solenoid valve at the rear of the Rail - *Cummins and DMax chose a mechanical pop-off valve for that chore, much like the one on your home water heater - actual Rail pressure is controlled by the Fuel Quantity Solenoid in the Jeep CP3, and the Fuel Control (Solenoid) Valve in the Cummins and DMax CP3's.

The hot-boxes cannot alter the Rail pressure nor the upper pressure limit as programmed in the ECM - they only offset the sensor output levels, which ECM measures to determine operational requirements.

Also noting here - the scanners display only what the ECM is measuring, whether the sensors are offset or not (the Edge module has a switch to select between stock output and hi-output) - however, max Rail Pressure cannot exceed CP3 calibrated mechanical output limit, whether the sensors are offset or not

Now, reading between the lines (you did read all assigned material, right?), you may have noticed a brief annotation in this instructor's sig, allegating to possession and use of an Edge Trail device, closely accompanied by an SGII device - therefore, assuming those alleged devices to be correctly installed and utilized, any claims to max rail pressures could probably be substantiated with results obtained by constant employment of those devices, within the charters of their designated tasks - allegedly.

Therefore, if aforesaid allegation is acceptable to the court, and to wit: max observed rail pressure with the SGII and the Edge Trail hot-box, verified with the AE DCJ-Enhanced scantool has never exceeded 23200psi, factoring in the +/- specs of the rail pressure sensor.

In the Cummins and DMax world, when the big boys are playing at 500hp and upwards, rail pressures and resultant rail volume has been seen to quickly drop, such that they literally run out of fuel due to insufficient fuel volume in the rail - various modifications have been developed to increase, not rail pressure, but pump volume, such that each stroke delivers greater quantity of fuel, thereby maintaining rail volume and pressure under increased demand.

How? Pump displacement - bore and stroke - of the CP3 is written in stone, fixed and invariable - so, they increased the pumped volume per stroke by altering the inlet areas in the fuel metering plunger in the fuel control valve - now, when ECM is calling for 63mm3 of fuel, CP3 is delivering 83mm3, and upward per demand\event, resulting in increased rail volume to supply increased demand - but still mechanically regulated to 23200psi max.

Even that modification has upper limits, so they have been running twin-CP3 pumps feeding the fuel rail, easily keeping up with fuel demand at 750-1200hp and 1600-1800ftlbs torque - them ain't yer grampaw's Diesels, no more, eh.

So - inserting a hot-box between the ECM and the Rail Pressure Sensor and MAP (Boost) Sensor does not increase CP3 upper limit pressure - it does, however, cause ECM to increase Fuel Quantity Solenoid\Fuel Control Valve pulse duration as required to bring fuel pressure up to the specified levels called for at any operational level - operational levels that ECM thinks are low due to the offset output from the Rail Pressure Sensor and MAP\Boost sensor - Map sensor offset will result in increased injection pulsewidth as ECM equates lower-offset Boost as requiring more fuel (MAP sensor-only offset will increase injection pulse-width duration only, without additional benefit of offset rail pressure).

What is the result? Increased rail pressure at any demand level, whereby pressure can peak at lower rpm, which increases injection volume at all levels of injection duration, and increased injection pulse-width, both combining to result in increased Boost and increased power at lower rpm.

Try it - you'll like it...........................

crd liberty · **Posted:** Fri Feb 08, 2008 1:57 pm

gmctd
Tired here after reading that. May need a nap.
Wish I knew just 1 percent of what you know about engines

Steve

gmctd · **Posted:** Fri Feb 08, 2008 2:11 pm

Unfortunately, some have accused me of being insightful, and that's very hurtful - I'm just a grizzled redneck old-timer that still enjoys gettin' dirty and wrenchin' on these ole motors................

USNA · **Posted:** Fri Feb 08, 2008 2:28 pm

Thanks for this thread all who have contributed.

CATCRD · **Posted:** Sat Feb 09, 2008 11:05 pm

gmctd wrote:

The hot-boxes cannot alter the Rail pressure nor the upper pressure limit as programmed in the ECM - they only offset the sensor output levels, which ECM measures to determine operational requirements.
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What is the result? Increased rail pressure at any demand level, whereby pressure can peak at lower rpm, which increases injection volume at all levels of injection duration, and increased injection pulse-width, both combining to result in increased Boost and increased power at lower rpm.

Not trying to nit pick here, but don't those statements contradict each other? The box receives a pressure value from the rail, it reduces it by some amount and passes that lower value on to the ECM. The ECM, thinking the rail pressure is lower than commanded, increases it. This makes true rail pressure greater than what the ECM thinks it is.

Now if the pump pressure is mechanically limited to 23.2kpsi - which it sounds like you're saying it is - when the false pressure reading from the box reaches this ceiling, the ECM will stop trying to increase it: no point in trying. What we suppose is that - confronted with this ceiling - the ECM responds in some other way, perhaps increasing duration. I don't know.

So what it sounds like you're saying is that the max pump pressure is capped by what I call a PRV set at 23.2 kpsi. That's what I wanted to know, and it's certainly good news for people using these tuners. On the pump we're currently designing at work the PRV is set at assembly to a value substantially higher than rated pressure, and when it vents to tank during test, it's incredibly loud. Software pressure control is the normal mode of operation, not mechanically venting. I guess what we disagree on is what I said before; that running your pump at a higher average pressure than the next guy will shorten its life by comparison. True for any pump. Just like I'm aware that constantly towing heavy loads with the Inmotion tune or street racing flat out will shorten the life of my engine/transmission/driveline. I'm OK with that, because I don't do it much.

Now about stacking...anybody done it on the CRD yet? :twisted:

gmctd · **Posted:** Sun Feb 10, 2008 12:29 am

Good questions - what occurs is based on

a.) ECM programming, which is invariable without a reflash, as in the Inmotion use of the Euro tune whereby ECM response to the sensors is altered - offsetting the sensors cannot alter ECM programming - and

b.) ECM normal response to those same sensors, which have been modified for offset output

Since the Rail Pressure Sensor and MAP\Boost sensor have been offset to achieve some performance gain, and since ECM accepts those offset values as being correct, ECM then increases Fuel Quantity Solenoid duration to raise offset Rail Pressure up to expected value - as the offset value will always be less than the real value, PCM would continue to demand increase even if live Rail Pressure had reached the 23.2kpsi CP3 limit - that would probably result in CEL and DTC, and has done so in the past when those conditions have been met.

Now, since ECM is reading offset values from the sensors, a scantool connected to the DLC would also read those offset values, not the actual live values - as Rail Pressure does not appear to be offset at the high end according to the scantool, the hot-boxes must be factoring out the offset value as max pressure is approached - either that, or the scantool is reading ECM rail pressure demand, rather than live rail pressure - lack of CEL would seem to indicate that it is the live value.

'Nuther words, ECM can only respond as it was originally programmed, whether you've tricked it or not - altering the software by reflash can result in greater power - should result in even greater power when the hot-box is stacked on - just make sure you don't have a plastic torque convertor when you do that - the plastic stator is the part that turns a fluid coupling into a torque convertor........and also turns it into nothing more than a Halloween noismaker: rattle rattle whizzzzz.................

DarbyWalters · **Posted:** Sun Feb 10, 2008 12:46 am

As tested, when the module affects rail pressure beyond limits it does put you into a limp mode...Diesel Power Mag test last year.

gmctd · **Posted:** Sun Feb 10, 2008 12:49 am

Correct - if monitored rail pressure is not within spec'ed range for any operational condition, ECM will CEL and DTC - a faulty sensor can cause that

And since someone asked: the only CRD's that do not have plastic torque convertors are those with SUNCOAST in the owner's sig.

Be afraid - be very afraid................

BlackLibertyCRD · **Posted:** Sun Feb 10, 2008 10:24 am

gmctd wrote:

Correct - if monitored rail pressure is not within spec'ed range for any operational condition, ECM will CEL and DTC - a faulty sensor can cause that

And since someone asked: the only CRD's that do not have plastic torque convertors are those with SUNCOAST in the owner's sig.

Be afraid - be very afraid................

I'm with you on that point. The next mod on my list is the replacement torque convertor. One thing I can't understand is why do I need a shift kit if I think it's shifting ok now. Wouldn't the TCM adjust the shift back to the way it was?

gmctd · **Posted:** Sun Feb 10, 2008 12:20 pm

Good question - as built, the 545RFE has a stamped steel end-plate over the five gear-range accumulator bores - transmission rebuilders for the Hemi boys have found some transmission failure to be caused when the stamped steel warps\deforms, eventually pulling the short screws out of the aluminum valve body.

By upset-forming a stamped steel piece, a thin plate can be made to assume the strength of a much thicker plate - however, even the pumped-up weakling thin plate survives only marginally in the severely-restricted Torque Management Request limited, EMCC infested, F31\F37 solutioned DCJ world of heavy-duty transmission engineering - the shift kit supplies the as-required unstressable replacement.

Then, for those elderly 545's of some accumulated mileage, also provided is replacement accumulator-piston rings and seals, along with some improved valving to replace those that have been proven to stick on occasion resulting in shudder and erratic response, plus stiffer accumulator apply-springs, as well as springs required to replace the worn pieces in the pressure regulator in the pump, and some stiffer springs to improve torque convertor response, plus a resistor to offset the line pressure sensor, allowing greater pressures for improved shifting.

FYI - a spring in a vertical bore seldom wears against the walls of the bore - a spring in a horizontal bore, as in the pump, will quickly wear on the lower outside surfaces of the coils due to gravity, such that spring tension is quickly reduced as coil diameter is reduced - rated spring pressure is determined by wire diameter and number of coils

All in all, well worth the 65buck asking price - have not yet had the pan off the 68RFE, but will be interesting to see if DJC bean-counters allowed the engineering department to resolve those issues for this HDMS transmission

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