Does anyone know what the optimum RPM would be to get the best MPG? I would assume that it would be about 3200 RPM, just before the VTEC kicks in.

Does anyone with more knowledge about the VTEC have any insite?

Thanks in advance

 

I asked the question on another thread: At what speed does the FIT achieve maximum MPG? I'm no expert, but wouldn't each RPM use the same amount of gas? Then the more RPMs, the more gas you use. There has to be a speed where the distance traveled for each RPM is maximized. Above that speed you use more gas per mile traveled. Below that speed you're not traveling far enough for the gas being used.

 

This may not answer your question, but it is good info about the engine's specs: http://asia.vtec.net/Series/FitJazz/lseries/index.html

 

I thought about doing some tests to determine this, but it depends on a lot of factors....Gas brand selection, throttle input, wind conditions and road conditions, etc. GENERALLY, you can assume the lower the rpm, the less gas you use, but I know of some cars that achieve the optimum balance of power and mileage at like 3k rpm or 3.5. Anyone else know more?

In my own experience, freeway traveling, the best I've gotten on Cali gas was 34 MPG, and i think i set the cruise control to 80 exactly, on my Sport Auto. It would take a lot more input from other people to determine a precise answer, and it will be difficult for this to not turn into yet another "WHAT IS YOUR MILEAGE!@?!@" thread, but lets see if anyone knows the answer to the original question

Tre

 

An indicator light connected to the Vtec??? OK??

This is pissing me off, I’ve herd everything from 2700 to 3800. I would definitely like to know. Keeping below the Vtec engagement would be a good compromise between speed and MPG.

 

any link on how to connect the LED?

 

And once again Claymore - until someone proves different here stateside HONDA USA says 3400 rpm for the NA model.

http://www.hondanews.com/CatID2153?m...55013&mime=asc
"VTEC
Part of the balance between efficiency and power is made possible by Honda's VTEC variable valve timing system. In the Fit's 16-valve SOHC engine, the VTEC system employs a two rocker arm design (per cylinder on the intake valves) with friction-reducing roller followers for each pair of intake valves, along with intake cam lobes configured to optimize both low- and high-speed operation. Depending on engine load and rpm, an electronic controller determines which cam profile will be used and exactly how the intake valves will operate (usually around 3,400 rpm)."

 

Maybe the VTEC kicks in sooner under WOT. I think the MPG tests are performed at 55 mph for the freeway mileage, so whatever rpm at 55 is the the best one.

 

Optimum RPM to get the Best MPG? ----> 0 RPM and your fuel will last forever!

just kiddin...

 

It's probably similar to the S2000 VTEC - it kicks in earlier at WOT, later at slow acceleration. The computer decides when it's appropriate (within a fairly narrow range, though).

JonasM

 

the word to see here is "usually"

on my 6th gen accord, it also says usually at 3400rpm, but we have shown that it comes on earlier if you give it gas (WOT) .. i had a vafc and it has the vtec indictor light..

-joe

 

I drove my car at 4000rpm for a few tanks
I drove my car at 3000rpm for a few tanks
and i drove the crap out of it (redline shifting) for a few tanks

at the end, it really makes very little difference..

range:

7.68 L/100km = 30.626899 miles per gallon <-- 3000rpm shifts, driving tame
to
8.5 L/100km = 27.672304 miles per gallon <--- 4750rpm shifts, driving insane

on mix mode city driving

so i doubt that there is really a good range for "mad mpg"

-joe

 

not true. on an even leveled floor yes, but when talking about hills, the story changes.

the best wy to explain is riding a bike. the faster u pedal the more tired u get, so that's why you upshift. also, the higher ur shift, the more efficient each pedal cycle is (the wheel makes more turns per pedal at higher gears than lower gears.

but the story changes when you go uphill. lets say you go uphill on the last gear. u'll have hard time struggling up, so you pedal hard. ur rpm of ur pedal is still low,b ut u're getting tired fast. my point is if u're at too high of a gear, and need to floor the pedal to accelerate at the pace u want, get low rpm, but u might end up wasting more gas than if at a lower gear, light footed the pedal, and see higher rpm as a result.

 

I've now got 42XX miles on my Fit Sport AT. I'm averaging about 30 mpg to date.

There are a lot of factors involved in achieving maximum fuel efficiency. Yes, one of them is determining what rpm provides the best engine efficiency.

I'll just randomly use a number of 3000 rpm. If this is where the engine is the most efficient, then running at this rpm would provide the best gas mileage IF ALL OTHER FACTORS WERE OPTIMIZED!

Other factors include:
- wind resistance. The faster you go, the more air you have to displace to push the vehicle through the air. The slower you go, the less wind resistance you have.
- tire pressure. More air usually provides for less rolling resistance, and better efficiency.
- tire size. Although most of us have "new" Fits, when we start replacing the tires, this can be critical. A smaller, lighter, wheel tire combination results in less rotational mass which takes less power to turn. There are many other factors in tire size with can effect things - be careful here as you can change your speedometer!!!
- vehicle maintenance and care. A clean, freshly waxed car is going to slide through the air easier. Watch your favorite race, IRL, F1, Nascar, they are always rubbing and cleaning on the cars just prior to the race, looking for the cleanest car possible.
- weight. Clean the junk out of your car. Everything that you put in there adds weight. More weight means more load on the engine. Go on a diet (LOL!!!) or leave that significant other at home (j/k!!)
- gearing. The transmission determines how hard the engine has to work, based on the computer models. If the gearing is too low, the engine has to labor to try to keep the car at a given speed, which uses more fuel.


Now, having said all of that... If the engine is most efficient at 3000 rpm, and you have a MT Fit, that mean that in 5th gear, you are going about 62 mph. This may be the optimal speed. OR - it could be that using 4th gear, at 3000 rpm could be as you would be doing a slower speed and having less wind resistance.

I have an AT Fit. 3000 rpm in 5th is about 82 mph. There is no way that this is the optimal speed as the wind resistance is much higher. 3000 rpm in 4th would result in a much lower speed with less wind resistance, resulting in better fuel efficiency.

I titled this Misccellaneous Ramblings on purpose, as this is what this is.

Years ago, I saw a study which showed that most cars get their best fuel efficiency around 45 mph.

 

I saw that same study in P.M. some years ago!
Also if you check out the insight central boards those guys get over 60mpg's by going UNDER 50mph and coasting

 

You really have to look at it as a compromise between MPG and speed. how slow are you willing to go.

 

You will get the best efficiency at the slowest speed you can go in top gear without lugging the engine. Probably 35 to 40 on level ground for the Fit.

 

Based on my experience, I don't think the tests are based on 55mph for freeway. I only say this because I am able to get 40mpg doing at least 70mph (if not really averaging 75mph)- and this was with AC on the whole time.

I also got nearly 30mpg on my Element on a long freeway trip, which was done by driving a consistent 65mph on the freeway. The EPA estimate for an Element is only 26 freeway I believe. I'm sure if I drove 55mph, then the mileage would have shot up to at least 32-33mpg.

What I do agree with however is the fact that the lower the RPMs the better the gas mileage.

 

http://www.fueleconomy.gov/feg/how_tested.shtml

Dig around this site - the top highway speed is 60 MPH with an average of only 48mph !

 

ummm....say what? VTEC will either engage or not engage. It does not crossover sooner or later. It needs a certain RPM (set in the ECU), it needs a certain % of throttle and the engine must be warmed up.

To me, ^^ that does not relate the Fit's MPG.

Take some things into consideration when attempting to get maximum MPG. Are there lots of hills where you drive?
What are the average posted speed limits?
A lot of stop n go traffic?

Those are just a few. My daily commute to work is approx. 24 miles 1-way. It is mostly flat, with about 2 steep hills that are roughly 1/3 mile long. And, the average posted speed limit is 45 MPH. What does this mean for my fuel mileage? Let me tell you.

Since I got my Fit I have not had less than 35.6 MPG. When I'm driving to work I shift through the gears at 3200 rpm until I hit 5th gear. Without lots of a/c use and strong crosswinds or headwinds, I have attained 39.2 mpg. When I am feeling sporty and begin to shift at 4500 and higher, depending on how much of that is full-throttle, I'm still getting killer mileage around 36-37 mpg.

It's really not THAT scientific. If you want to squeeze the most out of your tank then you'll learn to use minimal throttle and minimum rpms. Regardless of what you choose and depending on what your surroundings are like, you'll see great mileage.