Fuel Rate (PCM parameter )???????

[rjwest]

Using a Laptop to read PCM Data and codes.

There is a Sense read out of " FR "
defined as Fuel Rate in mm3 ( millimeters cubed ).

Trying to convert to Gallons,
Question: How do I convert , tryed internet search,
can't seem to get a number that makes sense.

Also " FR " does not specify a time period,
IE sceonds, minutes, etc....


Anyone , have any Help ( Maybe GMCTD )?


OK: Why should I bother , I am Trying to calculate
Instant MPG from laptop,

I have noticed that the FR is less if I
downshift to 3rd on a hill (Loaded )

It appears Higher RPM with a Loaded truck gets better milage than lugging in OD at less than 2000rpm ). Trying to see if any significance differance.

[gmctd]

Fuel Rate is defined as volume of fuel pumped per 1000 pump plunger strokes.
Each cylinder injection cycle requires one stroke.
Four cylinders fire per crankshaft revolution.
250 crank rotations require 1000 pump strokes.

Engine turns X rpm per mile - 60mph is one mile per minute
3600rpm is 60 rotations per second

Now, if one train was heading east in russia, and the other train was heading west in canada, on which side would they bury the survivors?

Sorry - in Mathematical Circles I'm known as Mr. Zero, and so resort to attempts at humor to evade the issues. ;)

Truck gets 16mpg - how many cubic millimeters is that?

Less Fuel Rate per same rate of travel (mph) is better fuel mileage, is the extent of my knowledge on that subject.

On second thought......higher Fuel Rate at lower rpm indicates PCM is calling for power the engine cannot make.
Dump more fuel into it, and fuel is being consumed without getting any more work due to design limitations.

This is where 18:1 cr and 25-50psi Boost would help - those 360cuin Cummins sixes don't employ no magic at 900hp.

Drop into a lower gear\higher rpm range, and the engine requires less fuel to tote the load.

Be handy if a PCM-driven Fuel Rate gage were part of factory instrumentation.

See - simple, with numbers, but no math.....

[ 10-10-2004, 10:54 AM: Message edited by: gmctd ]

[Jim P]

The conversion for mm3 to gallons is 1 gal.=3785411.8 mm3.

On the old mechanical pumps, the fuel rate was defined as the amount of fuel pumped in 1000 strokes but on the electronic pumps it is defined as the amount of fuel pumped in one stroke of the pump. The older pumps fuel rate was expressed in cc (cubic centimeter). The electronic pumps use mm3. There are 1000 mm3 in one cc.

[jdmetcalf57]

I understand fuel rate to be cubic millimeters per injection per cylinder. When I had my truck on the scanner it run 14cubic mm at idle. If I remember correctly at 195HP the pump injects 63 cubic mm per cylinder firing.

Total fuel in cubic mm per minute = RPM x4 x Fuel Rate
there are 4 cylinders that fire per revolution.
Divide this by 3785411 cubic mm per gal to give gal per minute
Divide speed in mph by 60 to give miles per minute
Divide miles per minute by gallons per minute to give mpg

simplified this is

mpg = (mph x 15773)/(RPM x FR)
Fuel Rate FR is in cubic mm per injection.

A check on reality of this is a fuel rate of 45 with 2300 rpm and 50mph gives 7.6mpg

[jdmetcalf57]

From the equation I previously posted you can see that for a given speed it is the minimum combination of RPM x FR that gives best instantaneous mpg. GM could have given us the instant mpg very easily but they didn't. Maybe your experimenting could tell us how best to shift to get the best mpg while pulling hills.

I suspect that there is a sweet spot of rpm that gives best fuel economy. To high an rpm waste a lot of power just turning the motor over and I think? a motor lugged to hard has some different inefficiencys.

[gmctd]

Pretty sure the mech pump was rated as Fuel Rate @ rated hp = XXmm3/stroke @ 3600rpm, or similar....

[rjwest]

OK: GREAT : Now I have my homework to do,

I see 12-14 as a fuel rate at idle and

20-30 around town at 40-50.

will try to program computer this week.

[rjwest]

THANKS TO ALL RESPONDERS!!!!!!!!!!!!!!!

Got it programed into the Laptop.

Can now read Instant MPG, Now I have to figure out how to do a plot of the data, Reading on the fly is a little difficult....

i am using the PCM Fuel rate data.
It states it is PCM commanded fuel rate. So I figure there will be some differance from actual.
But should be a good comparison for MPG at different gears/Speeds.

Some initial data.: Flat Fla Road. NO HILLS
No accel/decel

.45 Gals per Hr at idle


35MPH 22-23 mpg
45 MPH 19-20
49 MPH 19-20 MPG TCC unlocked
50MPH TCC locked 20-23
55 MPH 20-22


About 3 MPG increase when TCC locks up.....

Also I noticed an increase in MPG when the temps
reached 180 ( thermostst).

Thanks JDMET again for the Formulas

[FARMERBOB]

I have a question related to this topic, if 63 MM/3 is 195 hp how much fuel do you get with the heath or jk chip?

[tom.mcinerney]

RJ--
What software(s) and hardware are you using to connect the truck to the laptop??

[rjwest]

I am using a Conector/cable/adapter from http://www.obd-2.com/ http://www.obd-2.com/
Above, called " carcode"

they sell the adapter for 125$us , you download the program and Diesel specific data.
They have just recently releases the L65 l56 nad L 66 Specfic data parameters...

Problem is with documentation, there is none,
Needed help from Diesel Page ( previos posts )
just to get Instant MPG.

Problem now is: can't plot User written equations,
Sent a note, they said they would look at it..

Was hoping to get a graph of MPG at different speeds, Just taking numbers not as accurate .

There are other programs, ( google search ).
also there was a Member who had a different program
( I think it was " Dimsdale " hav't seen him post lately though...

Will keep you informed.

Note: Before I put on the boost fooler, I was getting " Defuel mode set in PCM from to much boost. The standard cheap OBD2 reader would not reset this condition, the laptop Reset would.
If you have a laptop and are going to buy a reader, the program may be a good option,...

[autocrosser]

To answer how much fuel is delivered with the Heath PCM on a 96 I measured 80 at full throttle with my tech 1. I have see some reprogramed ones from other sources that delivered 77. I get very little smoke with 12lbs of boost. I can't see it in the day time but can see a little at night in the headlights behind me. It also made a world of difference in hauling a 8k trailer also.

I pulled about a 3500lb load last weekend and it never downshifted on hills on the interstate. I'm sure large mountain hills would cause a downshift. Big improvement!!!

[tom.mcinerney]

Thanks , RJ.
When I did my googling , no respondents had addressed any diesel outputs....

[Turbine Doc]

Farmer Bob,

On my scanner I show peaks up to 81mm, using a Heath re-flash, 70mm was about max on a stock L65 PCM, and 63mm on my stock L56 PCM. According to my local Stanadyne shop a DS4 can actually deliver up to 89mm at absolute max program conditions, delivery is controlled by PCM/chip programming vs engine speed turning the IP constantly varying, as far as I know nobody has a PCM or chip set for that high; a rate 80 is what most advertise.

I rarely if ever see rate that high, my rates during normal driving are similar to what is posted above, when heavy tow or "gittin it" is when I see higher rates. PCM will bump the 80mm at 1st load demand and fuel back to what is needed to sustain demand. Advantage with the flash or chip is more at 1st, plus it holds fuel and boost at a higher levels for longer.

GMs stock curves set for optimum time engine life, retard rates to "save" engine for long haul, PCM will "protect" engine to an extent. Performance is lacking then, you can add fuel/boost with foolers and re-flashes for more performance, but this can shorten engine life if you drive it too hard. Which is why I and several others MAKE NO SIGNIFICANT CHANGES TO FUEL/BOOST WITHOUT GAGES .

Cooling mods., bigger pipes, & other flow enhancements will allow safer operation, but you still need gages to have real time visual when you ought to be backing off.

[ 10-15-2004, 10:18 AM: Message edited by: tbogemirep ]