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Evap Solenoid and MPG
Topic Started: Dec 21 2014, 10:47 AM (1,135 Views)
jazzmandolin
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After replacing my ticking evap solenoid with a lower mileage used solenoid I seem to be getting approximately 3 less mpg. Wondering if and or why the solenoid would affect mpg? The replacement solenoid is quiet, quiet with no ticking whatsoever. I have never seen less that 44 mpg out of this car and the 44 was loaded with tools and 65-70mph. 55 to 60 mph unloaded I usually see above 50. My last tank driving mostly highway between 55 and 70 I saw just over 40 mpg worst I have ever gotten out of the car! Its been unusually foggy/humid and lots of rain over this last tank and wonder if this might have something to do with the low mpg? I am going to do a tank full of very conservative driving and see what my mpg shows.
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myredvert
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myredvert

Where are you located, and how long have you been driving you metro?
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jazzmandolin
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Northern California just up the road from Chico in Paradise. Been driving the car a couple years. Got about 35,000 on the complete rebuild of motor and head. Runs great uses no oil between 5000 full synthetic oil changes. Had motor/head done by a amazing metro specialist out in North Carolina couple months before we drove it out here to the left coast a year ago. Hope I can figure out what is going on here as I really want to be seeing better than 40/41 mpg. Will be interesting to see what my tank full of conservative driving will give me in mpg.
Edited by jazzmandolin, Dec 21 2014, 11:49 AM.
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jazzmandolin
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Just saying I REALLY want a scangauge or ultraguage to keep track of data. Funds are just too below low to pop for one at the moment.
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Old Man


jazzmandolin
Dec 21 2014, 10:47 AM
After replacing my ticking evap solenoid with a lower mileage used solenoid I seem to be getting approximately 3 less mpg. Wondering if and or why the solenoid would affect mpg?
Have you considered that we have just changed over from "summer blend" to 'winter blend' gas? I always get a 3 to 5 mile drop in gas mileage when using the winter blend............
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jazzmandolin
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Actually I did think of this and am wondering if this might be whats up?
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jazzmandolin
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Old Man now that you mention that you always get the lower mpg out of the winter blend gas I have to highly suspect this is the reason for my lower mpg. Had any luck with fuel additives to compensate for the winter blend gas? I always run chevron gas as the car seems to run better a little smoother and get a little better mileage out of the Techron gas. Would using higher octane during winter blend season help any? I normally us 87 octane as I have not noticed any difference in performance when using a higher octane gas. I think our cars are designed to run on the 87 octane were they not?
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Old Man


I don't concentrate on gas mileage or looks---just "foot in the carb" performance and being a fun car to drive..........
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vr4


jazzmandolin
Dec 21 2014, 12:29 PM
Old Man now that you mention that you always get the lower mpg out of the winter blend gas I have to highly suspect this is the reason for my lower mpg. Had any luck with fuel additives to compensate for the winter blend gas? I always run chevron gas as the car seems to run better a little smoother and get a little better mileage out of the Techron gas. Would using higher octane during winter blend season help any? I normally us 87 octane as I have not noticed any difference in performance when using a higher octane gas. I think our cars are designed to run on the 87 octane were they not?
Nope and nope.


You'll spend more on additives than you're losing anyways.
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myredvert
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myredvert

As Geogonfa would say... "Just my .02 worth..."

In my opinion, tracking your mileage over time is a good thing to do. Observing trends over time can help us identify a pattern that may be worth investigating further, but its also important to keep the actual meaning and validity of our measurements in proper perspective. See what your fuel economy is doing over several tanks of very consistent driving patterns and routes. Personally, I'm a huge fan of the "Woodie Rule" which advocates measuring fuel economy over three or more fillups of close to a full tank accomplished over very consistent driving conditions to see what your fuel economy is really doing. That way some of the "errors" we are not even aware of at the time have a chance of evening themselves out a bit.

Theories based on assumptions based on lack of detailed facts aren't typically very correct. :whistle Offhand I can easily think of 15 + variables or conditions that will affect performance and performance calculations that normally exist outside of a professionally controlled testing environment, many of which you failed to detail or account for in your 'analysis.' And for good reason - even if we are aware of all of them, we still can't account for, control, measure, or normalize their effect in sufficient detail (or honestly in much meaningful detail at all) to the extent that we can theorize "why my mpg changed a little bit for the last tank..."

And respectfully, if your fuel economy is varying from over 50 to around 40, there are either large variations in your driving conditions or your driving technique (or both) over time that tend to make this kind of exercise pretty futile. I never attempt to jump to conclusions that "since my economy changed by this much, it must be a perfectly reliable calculation, therefore, the change mustbe due to...." In fact, when a change is observed, my first and main question is always "what did I do differently or what conditions may have changed to affect my fuel economy measurements that I am not aware of, making them unsuitable to start theorizing..." That's just me, but I also happen to have decades of professional performance testing and measurement experience (in vehicles other than automobiles though, so maybe that invalidates my experience for measuring fuel economy in cars?" :dunno

We simply do not perform our measurements in a professional, scientifically controlled environment using the same precise planned and executed testing methodology a professional would use, and it is unrealistic to expect results that warrant some "professional" level analysis of possible (but not proven) small changes. Now, if you believe you have identified, controlled, and/or mathematically corrected for each and every one of those variables while driving around in the real world, then maybe it is time to 'worry" about a 3 mpg difference in your measurements. And also time for me to get to know you better so you can help me improve my testing and performance measurement knowledge and skills, because I'm not able to do that exceptional level of controlled testing. Coastdown testing to evaluate coefficient of drag (Cd) changes for major aero mods I feel I can do fairly well and get reasonably decent DIYer results, but fuel economy once my car leaves the garage and gets out into the real world, I'm honestly at a loss as to how I can possibly get "professional level, precise and reliable to the 1/10" type of results once my car leaves our driveway. :D

You don't have to have the same "performance goals" as Old Man to appreciate his philosophy - if your personal goals are oriented towards economy than performance and fun, simply do the things that you need to do to achieve it, be a little patient, learn more about and be more logical and fair about what all can affect fuel economy, learn how to standardize your driving technique and eliminate variables that will allow you to get slightly more meaningful calculations, and ease up on the "analysis" pedal a bit before you go absolutely bat :shit crazy jumping into the deep end of the "what happened/what's wrong" pool so fast. Worrying without adequate foundation can suck all the fun right out of your Metro and your life! Again, just my .02 worth...
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jazzmandolin
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I am not going to drive myself crazy over a few mpg difference but being the first time I have calculated less than 44 mpg I definitely took notice and decided to post here about it. To me a drop from 44 to 40 is pretty substantial considering my very consistent calculations over the last year. I have done tank full to tank calculations filling up until auto stop at the same gas pump and calculate almost every tank. I have gotten the 44 mpg when I drive my work route with my tools and 60 to 70 mph cruising. This has been very consistent over the last year. Drove a couple tanks with just myself and no tools stayed at mostly 40 to 45 mph in the mountains with some 55 mph and calculated 53 mpg on one tank and just under 55 mpg on the other. I do understand these calcs are not exact but should be fairly close.

Asked about the solenoid because that is the only thing that has been changed sense my regular 44 calcs and then the 40 calc. Although when I posted about the solenoid and mpg at that moment I was not thinking about the winter blend gas. I do believe Old man has it correct and more than likely the drop is due to winter blend. Cant wait to see what I get out of my next couple tanks. I do drive a Metro for the MPGs and overall simple design. Will never be a hyper miler though. If I were looking for a fun toy to drive I would probably go for a Triumph Spitfire or Old Porsche 9/14 two of the favorite cars I have owned and driven. Anyway love the engagement we get here on the forum! I enjoy it.
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myredvert
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myredvert

Quote:
 
I do understand these calcs are not exact but should be fairly close... Asked about the solenoid because that is the only thing that has been changed sense my regular 44 calcs and then the 40 calc.
Respectfully, did it ever occur to you that considering you hadn't even considered the winter blend possibility, that there are (and have been all along) additional and even more significant variables that you didn't consider that would have significantly altered the performance you "measured" for each tank? Just sayin' :dunno

I have to be honest, I don't have near the level of confidence you seem to have in my own ability to account for all those many variables I am aware of that affect DIY fuel economy measurements, and want to be so quick to jump to an assumption/guess from it, and I have spent decades performing extremely precise operating profiles under very controlled conditions in order to measure and evaluate (among other things) fuel consumption. More difficult to execute in many respects, but surprisingly with far less variables to account and correct for than driving a car "out in the real world..." :hmm

I would think it is fair to say my driving profiles, techniques, and measuring methodology are fairly decent for a DIYer, and probably more disciplined than most, but I have a different perspective than most on just how meaningful my "measurements" actually are, when all things are considered.

I'm with Old Man for one - do the right things to obtain my personal goals, enjoy the ride, and not get too worked up over things that I don't have the ability to evaluate and measure accurately enough to think too much about.
:cheers
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jazzmandolin
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I am not getting all worked up over this. LoL I did think about the possibility of the winter blend gas just was not thinking about it at the exact time I posted about the evap. HA What I do know is for a year I consistently calculated 44 mpg on my regular commute driving the same route under pretty much the same conditions tank after tank. Then I get the 40 mpg calc driving the same route, pumping the same pump, calculating the same way. Only differences being the different evap solenoid, wet weather which I am so glad to have and the possible different blend of gas. Was surprised at the drop after a year of consistently same calculations and this is what prompted me to post. Thanks to the input here I am pretty sure my drop is from the blended gas. I suspect its takes a little more to push through rainy wet driving conditions too. Anyway Happy Holidays and I will post what my next tank mpg calc is.
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jazzmandolin
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I must say I am a little disappointed but not all worked up just disappointed. LoL. Anyway drove 250 miles on 6.5 gallons 38 mpg and I never drove over 60. I really never expected to see less than 40 mpg out of the little car but now I have. Never saw this low mpg using last years winter mix gas? Like I have said over many many tank fulls driving the same work route which includes 70 mph driving between Red Bluff and Redding Ca on hwy5 I always got right around 44 mpg give or take a little. To the fella that says there are too many unconsidered variables to my calculations all I can say is what I have said. Over may tank fulls driving the same route, pumping at the same pump I continually calculated right around the 44 mpg so I feel my calculations are pretty solid. Sense I never saw this much of a drop in my mpg before changing the evap solenoid I am considering dropping the old ticking solenoid back in to see if this makes a difference? I do know there has been a change somewhere recently. Whether it be low quality winter mix gas or something else a change has happened somewhere? I used to get consistant 38 mpg out of my 91 corolla wagon with room to spare and a little power in the hills. Really not happy with less than 40mpg!
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Old Man


Try running a couple tanks of high octane fuel and adding MMO to the fuel to help clean the injector.
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