E90 difference in gauges?

I recently took a look at the 328i and 335i E90 sedans. On the 335, it looked like the MPG gauge was not there. On the 328i, there was no temperature gauge.

Why the difference between the two?

Anoop

Reply to
anoop
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Isn't the mpg gauges nothing more than an estimate based on engine vacuum? If so, there is no vacuum in a turbocharged engine to measure; hence the mpg gauge is useless. In contrast, it is nearly useless for the normally aspirated engines.

As for the temperature gauge, it is also useless because all it really shows is that the engine is either cold or not.

Jim

Reply to
Jim

The MPG guage LOOKS like it is vacuum operated, but in reality is is a display of the injector timing compared against the vehicle speed. If you roll down the road at 40 and take your foot off the gas, the injector timing becomes very short, so the amount of fuel needed to continue on this kind of operational profile would be very small, and the MPG would become very high -- on my car (an E36), this is full scale for Best MPG. As you continue rolling along and approach a stop, the guage begins to drop because at the given speed and injector timing, the vehicle cannot continue at the Best MPG, and at full stop it gets the Worst MPG. On my daughter's E46, the guage works the same, except that when the car gets to a full stop, the guage goes to full scale Best MPG. I can't explain why it would do this, but my inclination is that there is a software bug.

In any case, I understand that the MPG guage looks like a vacuum guage, but it really is not or the needle would remain stationary as the vehicle rolled to a stop. Since the needle moves, then the indication has to be a measurement of fuel consumption vs. speed.

The temp guage is perhaps the most useful guage of the bunch. The condition of the engine is a function of the heat of the engine.

As for the original question, I can't tell you if what you saw is accurate or not. I see no reason for the difference in guages of the 328 and 335, except that the 335 would need a guage or two to tell one about the activity of the Twin Turbos.

Reply to
Jeff Strickland

Now you made me second guess myself. :-)

They have a picture of the 335i gauges here:

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the 328i gauges are here:
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I still wonder why they had to do that. There's got to be a reason!

Anoop

Reply to
anoop

I usually use the temperature gauge to tell me when I can start shifting at a higher RPM. I usually try to keep it below 4K until the engine reaches its normal operating temperature.

Anoop

Reply to
anoop

That's interesting, they took the fuel consumption gauge out of the 335 and put a water temp gauge in its place. I can only guess that water temp is more volatile in the twin turbo, so they want it to be more prominant.

Reply to
Jeff Strickland

If it were, it would read high at idle.

Reply to
Dave Plowman (News)

Its not a water temp gauge but a oil temp gauge like the E92 coupé. Oil temp is more important then a mpg gauge. Who can buy a 335i, he is not interested in fuel consumption.

"Jeff Strickland" schreef in bericht news:sCWii.2997$Np2.2783@trnddc07...

Reply to
Rob Barendregt

It is based on the amount of fuel being passed from the tank to the inj minus the amount returned. However, the newer systems are based on the exhaust and the time the injectors are open thus the inj time = fuel used (not burnt) / vehicle speed or distance.

If you reset the computer average consumption at 60mph with the throttle closed the reading will be about 90mpg but quickly drops to 60, 40, 35 etc as the throttle (hence fuel injected) is opened/speed & distance.

So if you want to lie about MPG when selling reset the computer at 60 with the throttle closed and stop when it reads 45mpg then show the intending buyer how frugal you V12 monster really is - Look sir I get 38mpg out of this - give me the money.....

Steve

Reply to
steve-caner

wrote

As if someone buying a V12 was concerned about mpg in the first place...

Pete

Reply to
Pete

Good call, oil temp is more cirtical than water temp. I knew that ...

Reply to
Jeff Strickland

Pete - get a little humor in your life - it was meant as a joke!

Reply to
Oscar

Yeah, I guess I forgot to put the smiley face at the end of my response. :)

Cheers, Pete

Reply to
Pete

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