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Old 08-02-2008, 07:16 AM   #1
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Question Scangauge came in! Questions about DFCO, neutral and throttle control

I just got my Scangauge! I'm also driving a different car now, and I tried the Scangauge on it last night.

I've heard that when you're coasting and the MPG reads 9999, that means you're in DFCO (deceleration fuel cut-off). I found that this actually occured when the car was coasting in gear and also when coasting in neutral. Is this normal? I should probably do a bit more experimentation.

I also did a quick read-through of the user's manual and it looks like you can actually adjust the throttle position in which the fuel cutoff occurs. Is this true? If so, that's insane! It was at "24" and I raised it to "28", but is this really what it does?

Thanks!
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Old 08-02-2008, 07:20 AM   #2
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Quote:
Originally Posted by FLAteam View Post
I just got my Scangauge! I'm also driving a different car now, and I tried the Scangauge on it last night.

I've heard that when you're coasting and the MPG reads 9999, that means you're in DFCO (deceleration fuel cut-off). I found that this actually occured when the car was coasting in gear and also when coasting in neutral. Is this normal? I should probably do a bit more experimentation.

I also did a quick read-through of the user's manual and it looks like you can actually adjust the throttle position in which the fuel cutoff occurs. Is this true? If so, that's insane! It was at "24" and I raised it to "28", but is this really what it does?

Thanks!
I guess it depends on the vehicle. The SG in my truck does not report 9999 when in DFCO. I have to look at O2 sensor data on the SG to confirm DFCO.

-Jay
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Old 08-02-2008, 10:32 AM   #3
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Yes, according to others, 9999 means DFCO.

You can't possibly be in fuel cut (not DFCO since there's no Deceleration involved) while in neutral, or the engine would stall.

I suspect that the adjustment is merely for the SG's detection of DFCO, which apparently uses throttle position as one of its criteria. I doubt that the SG can adjust a vehicle. If it can make adjustments like that then they would market that, since it's half the price of even the cheapest product that can.
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Old 08-02-2008, 06:07 PM   #4
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oklahotrod

Hello All
Teat vehicle is a 2004 Dodge Ram 1500 Quad Cab HEMI....
After doing more research I learned how to wire up my 2 cells on the 04 hemi Dodge in series. This really helped the overheating problem and cut the amp draw in half. I had begun hooking up a dual control map modifier friday PM and finished it this AM (Sat). Took it for a test and found I now had good control over the MAP and set the city dial back from stall to good driveability and set the HWY dial just short of stalling the motor. Now we had control over the O2 sensors with efies and the MAP and are seeing 35mpg on the Scan Gauge! We have been using a SCAN GAUGE to monitor engine functions and mileage in addition to the factory overhead console giving us mileage. The SCAN GAUGE seems to work great giving many function reading and the ability to clear /reset trouble codes. The only thing goofy about the Scan Gauge is that it consistantly shows better mileage than the onboard readout in a car/truck----we have tried it in several other vehicles!!!! That is not a bad problem if only it would be consistant always in any error-----------instead it seems to be more and more off the more electronic enhancements and HHO we add.
We closed the car lot today at noon and my wife and I took the truck on a test run to Norman Ok about 35 miles away. We ate lunch there and made several shopping stops. On the way over I had the map mod set on HWY and we were showing about 18mpg on the factory console and 35mpg on the Scan Gauge. Nearing Norman we were going up a hill and the truck started to stall and buck when I gave it gas and a warning buzzer and light came on and the throttle by wire went to idle!!!! Checking the Scan Gauge I found the motor had gone into open loop and the truck would not respond to the throttle------------it had obviously gone into limp mode. I cleared any codes and turned it off and re started and all seemed OK. I then left the map mod in City and it had better driveability than before and the mileage read about the same. After doing our thing in Norman we started back and now the Scan Gauge is reading an average of 50mpg and the factory console shows 14-15mpg ??????? It seems to me both these gauges should be using the same info from the ECU and should match??????????? Upon getting back to Chickasha and having gone 72.1 miles I fill it back up and am EXTREMLY DISSAPPOINTED & DEPRESSED to see 14.4 MPG !!!!!!!!!!!!!!!!!! That is about what the truck got before any mods and driving it harder!!!!!!!!!!!!!!!!
Any thought/help you can offer will be appreciated and also any sources that I might go to for answers. I have already kissed a lot of frogs and corrected others as well as my mistakes and this morning thought I finally had a marketable system. I am suspicious about the greatly increased Scan Gauge mileage coming back after the throttle malfunction. Sunday I amgoing to go mess with it some more, make sure codes are clear and take it for another drive.. Is it possible that after the throttle malfunction the ECU started dumping more fuel into the motor--if so why did it show much greater rather than lower mileage on the gauge?
Bill
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Old 08-02-2008, 06:23 PM   #5
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You can fix the SG readings. When you fillup the tank are you inputing the fillups in the SG? You can For example, last time I filled my tank the SG had overestimated my fuel usage by 1 gallon. I entered the proper fuel usage and SG will use that offset for future calculations so they are more accurate.

-Jay
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Old 08-03-2008, 10:54 AM   #6
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Well, after a little more experimentation, I've found that I need to stay in gear in order to sustain the 9999 mpg reading...but then after it gets below a certain speed (or rpm), it seems to drop back down to like 50mpg again, as if i were coasting in neutral. Is this the fuel-cut off getting switched off? I put it back into neutral after it drops from 9999...but should i downshift instead? Would the A/C being on or off affect the rpms, thus affecting the time at which the cut-off is switched off?

Also, it seems that SG has a sort of delay in displaying fuel economy in realtime...I think it might be a full 1 second delay. Does this happen to everyone?

Thanks.
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Old 08-03-2008, 02:31 PM   #7
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You can change the update rate for the SG in one of the options from SLOW, NORMAL and FAST.

The SG guesses at the DFCO based on throttle position and open/closed loop status (OPEN LOOP + idle TPS = DFCO ... usually)

You should set the CUTOFF value around 4 above whatever your idle TPS value is. At least that's what the manual suggests. For example, in my car the idle TPS is 10, so I have the cutoff set to 14.

You should adjust the tank after each fillup and try to fill after you have used at least 3/4 of a tank as this will reduce the significance of tank variability since its not always possible to fill the tank exactly the same amount every time. (Again, this is from the manual -- refill the calibration tank when at least 1/4 left)

DFCO is based on the rpms. For my car that would be around 1400 rpms, and coming down from 4th gear is usually 32 mph. YMMV

A/C usage or effect can be seen through the GPH. Engine condition, tire state, road condition, weight and aerodynamics will affect how rapidly your RPMs will drop off and some cars have more aggressive engine braking than others. You will need to experiment and see what technique works best for you -- neutral coast or in-gear coast or DFCO coast then into neutral coast. I personally do mostly in-gear coasting to stops but will do minor pulse-coasts in gear to keep my engine at the optimum rpms.
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Old 08-03-2008, 03:27 PM   #8
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Quote:
Originally Posted by azraelswrd View Post
You can change the update rate for the SG in one of the options from SLOW, NORMAL and FAST.

The SG guesses at the DFCO based on throttle position and open/closed loop status (OPEN LOOP + idle TPS = DFCO ... usually)

You should set the CUTOFF value around 4 above whatever your idle TPS value is. At least that's what the manual suggests. For example, in my car the idle TPS is 10, so I have the cutoff set to 14.

You should adjust the tank after each fillup and try to fill after you have used at least 3/4 of a tank as this will reduce the significance of tank variability since its not always possible to fill the tank exactly the same amount every time. (Again, this is from the manual -- refill the calibration tank when at least 1/4 left)

DFCO is based on the rpms. For my car that would be around 1400 rpms, and coming down from 4th gear is usually 32 mph. YMMV

A/C usage or effect can be seen through the GPH. Engine condition, tire state, road condition, weight and aerodynamics will affect how rapidly your RPMs will drop off and some cars have more aggressive engine braking than others. You will need to experiment and see what technique works best for you -- neutral coast or in-gear coast or DFCO coast then into neutral coast. I personally do mostly in-gear coasting to stops but will do minor pulse-coasts in gear to keep my engine at the optimum rpms.
Thanks! I must have missed that in the manual. I did not see that. When I checked what my cutoff is set to it was at 24. My TPS reading at idle is 0, so I set it to 4. Maybe now it will read DFCO correctly.

On a side note, as well as a 0 reading from the O2 sensor in DFCO, I have noticed that the IGN reading (ignition timing advance) will fall to -10 in DFCO. The timing also displays much faster than waiting for the O2 sensor to figure out what's going on. I'm hoping that SG will properly read DFCO and reflect it in the instantaneous mileage now. I have 2 pictures of readings I've gotten in DFCO today... Sorry for the poor quality, I took these with my cell phone.

-Jay



(above) This is me DFCO'ing down a mountain in third gear.



(above) This is me DFCO'ing down a large hill. Notice the -10 IGNition timing advance...
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Old 08-03-2008, 08:12 PM   #9
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Thanks azraelswrd, that cleared up a lot! My idle TPS is 0, so I guess I should put it to 4 as well. I really gotta read the manual more thoroughly, because I don't know where to get that AVG guage and I don't know how to interpret the IGN values.

I'll try to start calibrating my fillups...today's 110-mile run was nice, I'll continue to experiment.
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Old 08-04-2008, 05:53 AM   #10
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the AVG gauge is an X-gauge function where he uses a trip as a gauge. go to the website and read up on the X-gauge function and the add-a-gauge function. they are neat. that is also where he got the o2 sensor readings.

X-gauge codes are long and take a lot of time to put in but they are worth it. not being a computer guy, it may take me longer than some but I still got it done.
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