SPdiesel module

aandlwoods · **Joined:** Mon Jun 09, 2008 4:53 pm **Posts:** 96

I have an SPdiesel Sie module. I just discovered that i can change the fuel pressure separately from the power levels. When i change it i can feel and hear the engine idle different and if i go too high, it will idle very rough. Heres the question: Do i run the risk of messing something up (fuel pump) by increasing the fuel pressure by .5 psi at idle?

gmctd · **Posted:** Fri Aug 22, 2008 9:14 am

Fuel economy, severely.......................

aandlwoods · **Joined:** Mon Jun 09, 2008 4:53 pm **Posts:** 96

so adding a lift pump with a 5-9 psi range will hurt economy as well?

gmctd · **Posted:** Fri Aug 22, 2008 11:36 am

You seem very confused: the pressure you're adjusting with the SP is Rail Pressure outta the CP3 injection pump at ~5000psig idle to ~23000psig FWOT - adding a lift pump increases supply pressure to the CP3 from 0psig (BARO) to 9psig, eliminating several vacuum leaks between the fuel tank and the fuel manager head output - and I hardly think the SP module can increase Rail Pressure to such small increments - the problem with those Rail Pressure only modules is they increase Rail Pressure across the board, from idle to FWOT - much more efficiency is available when MAP (Boost) is factored into the mix, as with the EDGE\equiv modules - and all of the power-box modules ECONOMY mode is what's normally known on radios and tv's and lights and such as OFF - they merely dump fuel on demand by informing ECM that Rail Pressure is lower than expected for any given demand

aandlwoods · **Joined:** Mon Jun 09, 2008 4:53 pm **Posts:** 96

Ok, the module has preset power levels, Economy,0,1,2...10. Then it has a boost and fuel pressure guage. I turn on the jeep and i am showing about 4.5 psi (fuel) when its cold. Then i push the up arrow and the engine audibly changes, and then it shows 4.8 or so and it constantly changes but hovers around that area.

I was thinking that when i was running in Economy mode which is most of the time that the engine could be running slightly lean and was scared that i was risking internal engine damage from being too lean. With that, i was wondering if just bumping up the fuel pressure a little bit would prevent that. What do you think? Am i being overly cautious?

gmctd · **Posted:** Fri Aug 22, 2008 4:41 pm

Ok, maybe I seem confused: what fuel pressure does it display, and where is Boost tied in on the engine?

warp2diesel · **Posted:** Fri Aug 22, 2008 4:59 pm

I like the resistor idea better, but is the signal analog off the rail pressure sensor and boost sensor, or is it a BUS signal?

aandlwoods · **Joined:** Mon Jun 09, 2008 4:53 pm **Posts:** 96

Not familiar with the resistor idea. How can i find out if it is analog or BUS?

warp2diesel · **Posted:** Fri Aug 22, 2008 5:37 pm

aandlwoods wrote:

Not familiar with the resistor idea. How can i find out if it is analog or BUS?

GMCTD and TURBOTIM would know. If I had to find out on my own, I would probe with a VOM and if I had a steady DC signal, analog, crazy other signal BUS.

gmctd · **Posted:** Fri Aug 22, 2008 6:30 pm

The Rail Pressure signal is a 1v to 5v signal representing 0psig to 23000psig, strictly analog - you may be interpreting that display wrong - that's prolly 4.5 x 1000psig you're seeing, not 4.5psig, so you're adjusting it from 4500psig to 4800psig - still, where is it picking up Boost pressure - is there a wired connector to the MAP sensor?

And BTW - you cannot run a Diesel engine lean, as in the gasser (patooie!) sense - if you 'lean' out a Diesel, it just runs slower - if you run it 'rich', it just puts out gobs of power - they ain't the same, and never the twain shall meet....................

warp2diesel · **Posted:** Fri Aug 22, 2008 6:44 pm

Sense the boost pressure, lie to the ECM and proportionally tell a variable resistance lie from the rail pressure sensor to the ECM.

aandlwoods · **Joined:** Mon Jun 09, 2008 4:53 pm **Posts:** 96

gmctd wrote:

The Rail Pressure signal is a 1v to 5v signal representing 0psig to 23000psig, strictly analog - you may be interpreting that display wrong - that's prolly 4.5 x 1000psig you're seeing, not 4.5psig, so you're adjusting it from 4500psig to 4800psig - still, where is it picking up Boost pressure - is there a wired connector to the MAP sensor?

And BTW - you cannot run a Diesel engine lean, as in the gasser (patooie!) sense - if you 'lean' out a Diesel, it just runs slower - if you run it 'rich', it just puts out gobs of power - they ain't the same, and never the twain shall meet....................

Yes there is a connection to the MAP sensor.

Turbo Tim · **Posted:** Fri Aug 22, 2008 8:16 pm

Ahhh Ha! I thought so. This is exactly what I suspected. I have never seen how one of these boxes hook up, but it makes sense that they would intercept the MAP and Fuel Rail Pressure sensors. This is where they add (or subtract) what is reported to the computer.
Yes both sensors are analog, and one could use some resistors to do the same thing, BUT you would also have to know which way you need to move the signal (+ or -).
Since there is no evidence of a tach signal going into one of these boxes, it seems like a simple straight-line voltage divider or adder with a selectable switch.

If someone wanted to “donate” one of there trick boxes for a week or so, and didn’t care if someone was to “Peek” inside, who knows what we could discover!

We all could end up with yet another “Mod” for our CRD’s.

warp2diesel · **Posted:** Fri Aug 22, 2008 8:59 pm

We could probe by sliding a wire into the plug or probing the wire with a thin pin and hook up a 2 volt meters, one to the rail pressure sensor and the other to the MAP out put. One person could drive and the other record the readings or set up a video camera and drive hard up a hill or mountain.
Then we would have a data table to work with.
Sir Ohm and Nicole Tesla would both be proud.

gmctd · **Posted:** Fri Aug 22, 2008 9:34 pm

Ok, that's better than I expected - I had heard the SP was a Rail Pressure only box - the RP-only boxes just dump additional fuel from idle to FWOT - they can be offset to start from a threshold of rising RP which indicates demand for power, a threshold below which oem standard fuel rates are maintained - Boost, however, can be used to factor RP at lower rpms where additional fuel is not needed unless engine is loaded, where Boost would be up, the greater the Boost, the greater the fuel even at lower rpm - much better system when both inputs are factored, and those with a microprocessor will factor calculated tables for even more precise control

FYI - Rail Pressure is indicated in psig, where Baro Pressure = 0 on the guage - therefore, the oem Jeep CP3 draw-type system would indicate, say, 4500psig at idle, having no lift pump - installing a 9psig lift pump would indeed increase Rail Pressure, which would read 4509psig - hardly enuff to affect idle, or damage anything, eh...............

warp2diesel · **Posted:** Fri Aug 22, 2008 10:34 pm

1) MAP voltage goes up to L.O.S.T. box. Voltage is monitored between resistor and MAP.
2) Resistor in line lowers voltage to ECM
Note: This can be determined by placing POT wire between MAP and ECM and adjusting for max boost before ECM limits it.
3) L.O.S.T. box increases resistance to rail as MAP voltage increases
Note: This can be determined by driving up a steep grade with a POT hooked up between the rail pressure sensor and ECM, watch boost and EGT, when EGT reaches 1200F to 1300F, turn the pot down until EGT starts to drop.
An electro-mechanical version could be made by hooking up a 20PSI pressure gauge connected to the intake manifold and mechanically connecting the gauge to a POT that increases resistance to the rail pressure sensor as boost pressure increases, the MAP sensor output would be trimmed with a POT. Additional POTs could be used to trim the POT hooked up to the pressure gauge.

TurboTim could come up with an electronic version that would be less apt to wear out.

Turbo Tim · **Posted:** Sat Aug 23, 2008 12:52 am

I would suggest that before y'all go out with some duct-tape and movie cameras looking like something from a Mad-Max movie, that this could be done in a much safer mannor, like on a test bench.
All you need are a couple of variable power supplies, a couple of volt meters, and lots of writing paper.
You would see how each effects the other.
I'm waiting on a donar box to play with and I'll post the results.

aandlwoods · **Joined:** Mon Jun 09, 2008 4:53 pm **Posts:** 96

GMCTD, i found out that you were right. The fuel pressure measured is the high end.

gmctd · **Posted:** Mon Aug 25, 2008 1:23 pm

Yep - having only two digit displays for 5-digit numbers is severely limiting - I 'spect what you've got is an enhanced version of the EDGE TRAIL, with more bling - the 3-pos switch has always been out in the engine bay, wrapped around the module, so we never messed with it, leaving it in center position which was enuff to overcome F37 detune pretty handily
http://www.edgeproducts.com/product_ima ... al-117.pdf

SPdiesel module

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