ScanGauge II - MPG Questions
 

I've frequented this forum off and on for quite some time, and I finally made the time to register moments ago. I have several questions that I hope is ok to ask in this one thread / discussion. If not, I can make separate threads, but they are related...

My vehicle, in case it matters, and if it doesn't show-up in my sig:

2003 MINI Cooper S

1. If one were to change the fuel injectors to larger ones, would that impact how the SG2 computes MPG, and if so how (up or down)? Not knowing how this figure is computed, I have no idea...

2. During set-up the user is prompted to input the displacement of the engine. Does it matter if the engine has forced induction (turbo or supercharged)? Since the instructions don't note such, I guess not, but I ask because many often speak of the effective displacement of boosted engines (at a specific PSI)...

3. Prior to purchasing the SG2 I was led to believe that during set-up it asks for the vehicle's weight. I was not prompted for that information so I guess I was misinformed, or I confused this with another device. So, vehicle weight is not a needed input for the SG2, correct?

4. Setting of the fuel cutoff. Many threads here and on the web... When off the throttle, coasting, in gear, I get the expected "9999", with the default of 24. I had read that the cutoff is best with a setting at 1-4 above TPS, in neutral. The instructions say 4, but others had said 1... With the engine idling, car parked, I see a TPS of 7. A poster had said to get this TPS number with the engine not running, but with the ignition in the 2nd position. My SG2 does not turn-on in this position though. When I turn the engine off though, the SG2 remains on for a bit, and TPS at that point is 2 or 3. Should the SG2 be activated, or have a visible display with the ignition in the number two position (engine off), and is this the ideal or best way to get the TPS number?

5. I am not using the Trip features, but I am using the Gauges, notably MPG and AVG. Since I'm not making use of the Trip functionality, keeping track of the price paid per gallon, is performing the dual fill-up procedure beneficial for more accurate real-time MPG and AVG figures on the gauges?

Thanks much for your assistance.

Welcome to Ecomodder, TonyB!

I'll attempt to answer your questions to the best of my abilities. Others will chime in and correct me if I am wrong :D

1. This will not affect the readouts. The SG uses complex algorithms to determine your fuel economy, along with reading from the MAF, MAP, O2 sensor, TPS and others.

2. I see what you are getting at. But, the SG calls for the exact engine size, so if you have a 2.0, then input a 2.0. It can read Boost Pressure and different MAP/MAF readings, so it will be on top of things :thumbup:

3. The best I can remember, vehicle weight is not needed for the SG.

4. The SG calls for 3-4 over your idle tps. You would want to register this reading as 10 or 11. When you are coasting in Neutral, your engine is idling, right? So that is the measurement you want to go from. Unless you are Engine Off Coasting (EOC), then that value has no meaning :D

5. Yes. This procedure is to get the SG accuracy dialed in. It will be ballpark at best without calibration. It is still useful, but if you are like me, you want real time data. Doing the calibration will provide that!

Don't hesitate to ask anymore question, Tony. We love helping out around here :)

it will all even out and correct its self after a few fill ups.

also set it to hybrid if you are coasting engine off or you are turning the car off at redlights.

Thank you both! Very helpful group here indeed.

1 and 2 - Great to know, and figured that this was being accounted for by the SG2.

3 - I must have been thinking of a different device. I've shed a fair amount of weight on the car...

4 - I appreciate the confirmation on +3 / 4 over idle TPS. But, this brings up an interesting discussion on coasting in neutral, or in gear. After a fair amount of reading, I was left to believe that coasting in gear is not only safer, but actually more fuel efficient, compared to coasting out of gear. Heck, I seem to recall that this (coasting out of gear) is illegal, at least in some states. Curious to hear any thoughts, but the important thing here is this... If one is generally coasting in gear, shouldn't TPS be noted during such, as opposed to just idling while parked? If one coasts out of gear, it would seem to make more sense to get the TPS figure accordingly, like parked in neutral...

5 - Alrighty, I'll start the fill-up procedure. But, dirtydave, are you saying that this procedure is not needed as things sort of correct by itself after a few fill-ups? No coasting with engine off, but that would seem to make sense. If I do decide to do the fill-up procedure, two times, that's it, and won't be necessary with every fill-up?

Happy Friday folks, and thanks again for your generosity!

"Coasting" in gear is not coasting. That is called engine braking.

Thanks UFO. I should have said such, and actually did so in my email to Linear Logic. Interestingly, the rep called that coasting...

One of few links I saved:

Looks like I cannot provide links at this point (need 5+ posts). Here is the content:

"No. Wrong.
All modern electronic fuel injection systems that I am aware of (and that includes a very large percentage of the market here in the US) shut off fuel on deceleration. The reason for this is NOT fuel savings, it is for emissions. Cars nowadays have to meet some very serious emission requirements. Leaving fuel injectors on during deceleration gives no advantage.* They also have a very serious disadvantage in that if you leave the injectors on you then have to deal with unburnt hydrocarbons, and CO.

This is why Bosch K-Jetronic fuel injection went the way of the dodo bird. The K stood for Konstant, this system just pissed fuel into the engine if there was air coming in. Because it sprayed fuel all the time air was flowing into the engine, it was too dirty to meet newer emission requirements.

As far as the details go, typically the system will look at throttle position (duh!) engine temp, and possibly air temp. If the throttle is closed above say 2,000 RPM the ECU stops activating the injectors until a preset RPM is reached, and then they are turned back on. This cut in RPM might be about 1300 RPM warm, and somewhat higher cold, say 1800 RPM. If the driver steps on the gas, the injectors resume right away, regardless of engine speed. This off and on function of the fuel injectors is imperceptible to the driver, but can be demonstrated in a shop using shop tools. I have shown this to my students hundreds of times.

I am not sure of the first system that used fuel cut, but I know Volvo has used it since mid 1982.

Getting back to the OP, assuming your ECU used a fuel cut strategy the difference in fuel usage would be so small I doubt you could measure it. But leaving the car in gear and allowing it to coast would use less fuel on a modern engine. I am not familiar with your model car and engine, so I do not know if uses fuel cut. I suspect it does, but I am not sure.

*The only advantage of leaving the injectors on, is it will keep the engine temp up. If you descend a very long grade, it is possible to have the engine coolant cool off to the point that the heater stops blowing hot air. This complaint shows up during the winter at some car dealers in Denver after cars descend the Eisenhower grade."
++++++

So, if I decide to do my downhill coasting in gear, ie engine braking, is getting TPS out of gear, idling, desired, then adding 3 or 4? As opposed getting a TPS figure while engine braking...

Thanks much.

the scangauge will be close enough after 3-4 fills you can update the price of fuel with everyfill for the tfc and cpm gauges


tps is the way to watch your right foot good for the DWL technique and steady state cruising

shift to neutral unless you are on the throttle. or if you feel unsafe or something

I've been using engine-off coasting in my Toyota 4x4 pickup for a while now, as it has no power anything. However, after 2 braking events, the booster runs out and the braking effort gets very heavy. This can be dangerous on long coasts, especially on long downhills. So with the engine off, I just stick it in gear (4th, 1:1) and release the clutch - voila! brake boosting is back. This works great when I have momentum to spare.

And by the way, the Scangauge will not automatically calibrate. Adjust the fuel amount input on each fillup and it should get closer and closer to actual fuel used.

Thank you very much for the follow-up.

I'll do the fill-up procedure when I need gas next, probably late next week. I'm curious how much more accurate it will be... I've noted my averages mutiple times between two homes (getting our old home ready for the mkt), so I'll see what the difference is when more accurate.

I must admit that I'm pleasanty surprised so far, assuming the readings are somewhat accurate. Local driving I'm seeing about 36 to 37 mpg. When I've had some highway mixed in, about 40. Actually today, when I got off the freeway, while at a light idling, I saw the average go from nearly 41 to almost 40 (2 minute wait). Damn. I had no idea idling was that detrimental...

Again, really curious to see if these numbers are true, as compared post fill-up procedure. I have the car's weight down to about 2,290 pounds (1/4 tank of gas). That excludes me, but I'm only about 140 pounds...

Thanks again.

I speak for everyone here when I say that we avoid idling at all cost. You get 0 mpg when sitting at a stoplight, stop sign, traffic, parking lot, etc. This is where changing routes and timing lights pays big dividends.

The stock weight for your MINI is 2678 lbs. I'm curious to know how you have dropped nearly 400 pounds out of that car.

Thanks BD. After doing more reading here, you are indeed correct. Idle or die, lol. I can see how some even wish to even cut their engines off at times; seemingly not ideal in all situations, and with certain cars, but I understand the motivation now...

As one might be able to surmise from my initial post, I've modified my MINI (larger injectors), with track performance in mind. Fun little cars, even on the canyon roads where we live. Hoping to hit Laguna Seca at some point, probably after I get the new home remodeled...

That said, the car has been a build of sorts. While I've increased the engine's output, the staple has been a steady diet of weight loss. The figure I have for a starting point is 2,513 pounds (Google that number and MINI Cooper). I confirmed that at a truck scale soon after purchase. Thereafter, I've had a couple corner balances. I'm currently at 2,292 pounds. A target of 2,250 seems doable...

I won't list everything, but wheels and tires alone, a little over 50 pounds. The stock runflats are heavy, and wheels are boat anchors. Within a few weeks after purchase, realizing that none of my friends or family would feel comfortable in the back seat, that was removed and sold. Corresponding hardware, belts, etc removed. Stock battery at 34 pounds replaced with a 12 pounder. Removed the battery box too that the exhaust had to snake around, which paved the way for a straight exhaust. My notes show a 35 pound savings there. Oh, A/C gone too (23 pounds). There are more such changes, but to give an idea as to the extremes, I took-out the interior carpet, and with a heat gun, removed a few pounds of sound deadening material. Same inside the doors too. I of course put everything back so it looks nice of course, not gutted. I temporarily removed the headliner and did some surgery to find and remove heavy brackets in place for a roof rack...

The car currently has a weight to hp (bhp) ratio of about 8.8. It will be around 7 to 7.5 when done, which is pretty good company:

The 2014 Audi TTS is at 12.3, the 2014 Subaru WRX STi is at 11.1, the 2014 Nissan 370Z is at 9.3, 2014 Ford Mustang is at 8.6, 2014 Corvette is 7.6, Chevy Camaro Z28 is at 7.6, the 2014 Porsche GT3 at 6.6, and the 2014 BMW M3 is a little over 8.

Light is good, in many respects. Braking is vastly improved too, as well as the suspension (responds quicker with less mass). There is less wear and tear in general...

To see the car getting about 40+ mpg is not a surprise I suppose, but still great to see, as that is what I had hoped. I originally got the SC2 to monitor water temps (installed an EWP) and intake air temp (a new IC I had designed) and had not made time to look at fuel efficiency until recently...

Very interesting TonyB! You should start a build thread and a fuel log for your MINI. It sounds like you have done awesome work, you explain yourself very well and are knowledgeable. Perfect for Ecomodder!

Thanks BD! I'll strongly consider such.

Looking forward to the next fill-up so I can get the SG2 dialed-in... A good week to you, everyone.

So I got an email today from the forum, stating that I haven't been active in a while here...

So, I'm back. I actually had a question anyways...

What exactly is the time duration being considered on the Average MPG? I assume/d it was from engine on to engine off, but lately, on shorter breaks between trips, like where I ran into a store for a couple minutes only, then fired-up the engine again, it resumed where I left off - the Average reading was around 40 MPG, which was where it was when I turned the engine off a few minutes earlier...

Curious if this is normal and by design. Thanks much. I should be at 1/4 tank later this week. Looking forward to see how much I need to adjust, and in which direction...

Your issue is a non-issue :) the SG clears this data, called recent trip data, after the car has been off for a minimum of 3 minutes.

As far as I know, the SG starts processing data as soon as your ECU receives voltage, i.e. when the key is on. Only after cranking and the sensor readings come into the ECU does the SG display these treasures :thumbup: you probably already knew that though. I need to get to bed!!

If you have any more questions, feel free to ask sir!

Thanks so much BD! I did not get an email alert of your response, so sorry for the delay...