2011 Cruze- 1 month review

[GMBoy]

Originally Posted By: LS2JSTS

In my Holden/GTO the fuel used is measured/calculated somehow at the injector itself, iirc. Something to do with the ECM and the pulse width thats being sent to the injectors. The readout is very accurate and even switches from average mpg readout to gallons per hour when the engine is idling. None of my other GM's have had that ability...curious does your Corvette read GPH at idle Patman?

You are are correct - the ECM/PCM uses fuel injector pulse width to measure fuel usage...not sure how that other guy got MAF.. The Corvette or any other GM car (other than your GTO) shows gallons per hour.

 

[OVERKILL]

Originally Posted By: LS2JSTS

In my Holden/GTO the fuel used is measured/calculated somehow at the injector itself, iirc. Something to do with the ECM and the pulse width thats being sent to the injectors. The readout is very accurate and even switches from average mpg readout to gallons per hour when the engine is idling. None of my other GM's have had that ability...curious does your Corvette read GPH at idle Patman?

That's the traditional method of measuring fuel consumption. And how my '89 Town Car did it.

 

[Patman]

Originally Posted By: LS2JSTS

The readout is very accurate and even switches from average mpg readout to gallons per hour when the engine is idling. None of my other GM's have had that ability...curious does your Corvette read GPH at idle Patman?

Not via the trip computer, but that info is available when plugging into the OBD2 port via a scan tool (like my Scangauge)

 

[cchase]

Originally Posted By: GMBoy

Originally Posted By: LS2JSTS

In my Holden/GTO the fuel used is measured/calculated somehow at the injector itself, iirc. Something to do with the ECM and the pulse width thats being sent to the injectors. The readout is very accurate and even switches from average mpg readout to gallons per hour when the engine is idling. None of my other GM's have had that ability...curious does your Corvette read GPH at idle Patman?

You are are correct - the ECM/PCM uses fuel injector pulse width to measure fuel usage...not sure how that other guy got MAF.. The Corvette or any other GM car (other than your GTO) shows gallons per hour.

I got my information from reading about how Scanguage and Ultragauge units calculate mpg and since my own experience shows that those units, uncalibrated, return identical values to what the car is reported led me to believe that the car was using the MAF data in conjunction with injector data to calculate fuel flow. I stand corrected.

 

[sciphi]

IIRC the SGII uses MAF data, GPH data, speed, and RPM run through a custom algorithm to figure out fuel economy. The SGII and dash instant MPG displays can be very far off from moment to moment. Somehow they arrive at a consistent % off from each other every tank. Go figure. I haven't been disappointed by the fuel economy on this car. For a $20k car, it gets amazing fuel economy! Well, part of that is a driver who's driving for fuel economy, doing lots of highway driving, in a car set up for returning great highway fuel economy. Nick, sorry for the threadjack!

 

[LS2JSTS]

Originally Posted By: Patman

Originally Posted By: LS2JSTS

The readout is very accurate and even switches from average mpg readout to gallons per hour when the engine is idling. None of my other GM's have had that ability...curious does your Corvette read GPH at idle Patman?

Not via the trip computer, but that info is available when plugging into the OBD2 port via a scan tool (like my Scangauge)

I didn't even notice it for quite a while. As you approach a light or the engine rpm drops below about 1,200, it automatically switches to tenths and reads GPH right on the trip computer, then back to mpg when you accelerate. First time I noticed it I thought all trip comps should do this!

 

[Vikas]

OBD-II does NOT report actual fuel used. The scangauge type devices infer the fuel used by integrating MAF (or MAP) readings over the time. The assumption is made that on average the engine runs at the 14.7 stoichometric (?) ratio. The injector pulse width is NOT exported out to OBD-II

 

[GMBoy]

Originally Posted By: Vikas

The injector pulse width is NOT exported out to OBD-II

Wrong. The injector pulse width is monitored and reported - but maybe not in all cars. Also all scan tools don't show it. My GM Tech 2 shows it right along with the long and short term fuel trims.

 

[Win]

Originally Posted By: LS2JSTS

Originally Posted By: Patman

Originally Posted By: LS2JSTS

The readout is very accurate and even switches from average mpg readout to gallons per hour when the engine is idling. None of my other GM's have had that ability...curious does your Corvette read GPH at idle Patman?

Not via the trip computer, but that info is available when plugging into the OBD2 port via a scan tool (like my Scangauge)

I didn't even notice it for quite a while. As you approach a light or the engine rpm drops below about 1,200, it automatically switches to tenths and reads GPH right on the trip computer, then back to mpg when you accelerate. First time I noticed it I thought all trip comps should do this!

The Holden's seem to be full of neat little features. On the G8, instantaneous fuel consumption is in the engineering menu, and it never switches from GPH so you have to do the arithmetic when in motion. It shows some other neat data like throttle opening, tranny temp, coolant temp etc.

 

[Hokiefyd]

Originally Posted By: GMBoy

Wrong. The injector pulse width is monitored and reported - but maybe not in all cars. Also all scan tools don't show it. My GM Tech 2 shows it right along with the long and short term fuel trims.

I think Vikas' point was that the OBD-II protocol doesn't recognize or "have a place" for injector pulse width. I have no doubt that a manufacturer-specific tool could see it, but it may not be a part of the standard OBD-II protocol. If it were, then wouldn't all cars have it?

 

[GMBoy]

Originally Posted By: Hokiefyd

Originally Posted By: GMBoy

Wrong. The injector pulse width is monitored and reported - but maybe not in all cars. Also all scan tools don't show it. My GM Tech 2 shows it right along with the long and short term fuel trims.

I think Vikas' point was that the OBD-II protocol doesn't recognize or "have a place" for injector pulse width. I have no doubt that a manufacturer-specific tool could see it, but it may not be a part of the standard OBD-II protocol. If it were, then wouldn't all cars have it?

You are probably correct. The base OBD2 protocol probably doesn't mandate it but the OEMS offer enhanced OBD2 for their own use. Good point.

 

[Hokiefyd]

Originally Posted By: GMBoy

You are probably correct. The base OBD2 protocol probably doesn't mandate it but the OEMS offer enhanced OBD2 for their own use. Good point.

One of my favorite features of the two Cadillacs I used to own was the Driver Information Center. You could get all sorts of information out of the computer if you knew what buttons to press (and it was pretty well-documented online). I must say, I think GM is THE best for making vehicle data accessible to the driver while driving. Some Chryslers are now getting there also, I think some have digital oil pressure and/or temperature gauges that you can select on the instrument cluster.

 

[GMBoy]

Originally Posted By: Hokiefyd

Originally Posted By: GMBoy

You are probably correct. The base OBD2 protocol probably doesn't mandate it but the OEMS offer enhanced OBD2 for their own use. Good point.

One of my favorite features of the two Cadillacs I used to own was the Driver Information Center. You could get all sorts of information out of the computer if you knew what buttons to press (and it was pretty well-documented online). I must say, I think GM is THE best for making vehicle data accessible to the driver while driving. Some Chryslers are now getting there also, I think some have digital oil pressure and/or temperature gauges that you can select on the instrument cluster.

Yep! My dad had a 1983 Eldorado, then a 1984 Seville and a 1994 Deville that all had the data available right on the AC control head or DIC. Nice touches that are gone now.

 

[sciphi]

My Cruze will show instant MPG, distance to empty, and speed on one screen, average MPG/miles traveled and speed on the trip computer screens, and a separate "vehicle information" menu with direct tire pressures (within 1-2 PSI of my digital gauges), battery voltage, and coolant temperature (215-219*F is a normal temperature for this car). Not like the old GM's, but still handy. Likely there are a few hacks that nobody's discovered yet. I also have my ScanGauge II set up in the car, mainly for the boost gauge function. I also have GPH, ignition timing, and average fuel economy displayed. The other gauges get cycled through periodically to make sure everything's okay. It actually reports fuel pressure! The fuel pressure varies from 43 PSI to 50 PSI depending on load. The gallons/hour is handy for figuring out how to make the deceleration fuel cut kick in when going downhill in gear. It's a fun little game to play, and keeps me from speeding down hills since it only triggers during ~1300 to 1800 RPM. I'm thoroughly enjoying this car, even though the interior has some teething issues.

 

[Hokiefyd]

Originally Posted By: sciphi

I'm thoroughly enjoying this car, even though the interior has some teething issues.

Teething issues? As in things are wearing quickly, or some things were overlooked in a first-generation design?

 

[OVERKILL]

Originally Posted By: Hokiefyd

Originally Posted By: sciphi

I'm thoroughly enjoying this car, even though the interior has some teething issues.

Teething issues? As in things are wearing quickly, or some things were overlooked in a first-generation design?

If you look back through the thread, he has some annoying rattles that he's hoping the dealer can fix.

 

[sciphi]

Originally Posted By: OVERK1LL

Originally Posted By: Hokiefyd

Originally Posted By: sciphi

I'm thoroughly enjoying this car, even though the interior has some teething issues.

Teething issues? As in things are wearing quickly, or some things were overlooked in a first-generation design?

If you look back through the thread, he has some annoying rattles that he's hoping the dealer can fix.

Basically. Feature-wise, I'm not complaining. It has the features I want, and they work as advertised.

 

[Vikas]

Originally Posted By: GMBoy

Originally Posted By: Vikas

The injector pulse width is NOT exported out to OBD-II

Wrong. The injector pulse width is monitored and reported - but maybe not in all cars. Also all scan tools don't show it. My GM Tech 2 shows it right along with the long and short term fuel trims.

Fair enough; I should have qualified my statement by saying it is not one of the standard OBD-II parameters and thus scangauge type of devices do not use it. I am still not sure if on average the engine always runs at stoichemtric. Is that really true? The UltraGauge I have is not user friendly for tracking mileage. Besides, I could not get it to match the real world fuel economy in few iterations.

 

[rslifkin]

^ Generally, once the O2 sensors are heated up, most modern engines will run at, or very close to, stoich unless you apply enough throttle to hit fuel enrichment.

 

[Hokiefyd]

The A/F ratio really depends on the engine; a number of modern engines have lean-burn modes which are leaner than stochiometric. I don't know about the 1.4L in the Cruze, or how the turbocharger would affect the desired A/F ratio.