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Old 05-11-2008, 09:49 PM   #11
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I've never achieved higher than 44-45 in all city with my VX, but I have a decent amount of hills. Without those, which is probably how the old EPA was tested, I would expect at least to be able to get 47 with my high-mile VX.

I've also been in the 50s for highway trips as well, and this is without matching front-to-back tires, no grill block (such as the factory one), and no rear diffuser.

The old EPA is possible if the car is in perfect shape. But for how little the VX costs I still can't see many if any hybrid coming close to beating it in the long-run for cost to own.
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Old 05-11-2008, 09:53 PM   #12
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"old EPA, not new EPA"

Fair enough. I didn't realize that's what you meant.

"I want to know how difficult it is to achieve 47 city and 56 highway"

I think the gaslogs here show that 45 mpg overall is a very typical result. I think they also show that certain people, with mostly unmodified cars, are able to get 50-60 (and sometimes better), on a fairly regular basis.

But only you know your own driving environment and driving style, so you'll have to interpret these numbers in that context.

Anyway, I think the bottom line is that you're likely to beat a VX only by buying one of the following: something with fewer than 4 wheels; something with fewer than 4 cylinders (e.g., certain Metros); a hybrid; or a diesel. And when an item on that list beats a VX, it usually does not do so by a wide margin.
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Old 05-11-2008, 10:07 PM   #13
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Quote:
Originally Posted by monroe74 View Post
"old EPA, not new EPA"

Fair enough. I didn't realize that's what you meant.

"I want to know how difficult it is to achieve 47 city and 56 highway"

I think the gaslogs here show that 45 mpg overall is a very typical result. I think they also show that certain people, with mostly unmodified cars, are able to get 50-60 (and sometimes better), on a fairly regular basis.

But only you know your own driving environment and driving style, so you'll have to interpret these numbers in that context.

Anyway, I think the bottom line is that you're likely to beat a VX only by buying one of the following: something with fewer than 4 wheels; something with fewer than 4 cylinders (e.g., certain Metros); a hybrid; or a diesel. And when an item on that list beats a VX, it usually does not do so by a wide margin.
45 in the city is fine, but from the mileage figures I see, 45 on the highway is not acceptable. Do people here not drive on the highway very much? I live in the bay area where I would be doing quite a bit of highway driving. Also I read that the VX has a Drag coefficient of .32 but why does the HX have .38??
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Old 05-11-2008, 10:39 PM   #14
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"Do people here not drive on the highway very much?"

I don't know why you're saying that, because the gaslogs explicitly reference a fair amount of highway driving.

"45 on the highway is not acceptable"

I don't know why you're saying that, because the gaslogs explicitly indicate that lots of folks beat that on the highway, or even off the highway.

"I live in the bay area where I would be doing quite a bit of highway driving"

I think you'll see a big difference between cruising at 55 as compared with cruising at 80. And I imagine both of those speeds are used on the roads you're talking about, so this is where your own details have to be considered.

Also, you'll see a big difference between driving smart (using the kind of techniques discussed on this forum), or not. So this is another reason why your own details need to be considered.

And again, if you're worried that a VX won't be good enough (however you define that), I think you have to say, compared with what. Because it's hard to beat.

"why does the HX have .38"

I don't know. Maybe the coupe design is fundamentally less slick than the hatch. That's a guess.
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Old 05-11-2008, 11:51 PM   #15
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I was looking on wikipedia on ignition timing, and found this picture. Now I've got another question, why are there so few instances in this timing map where it's closed loop? I was under the impression that it only goes into open loop when the engine is at high load, high RPM, choosing the timing based off of predefined tables, usually resorting to 12:1 fuel ratio in order to protect the engine or something.
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Old 05-12-2008, 04:36 AM   #16
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"You can buy HX 14" wheels"

You're getting great results, so that seems to be working well.

But I assume you're getting a fairly substantial speedo error. Are you correcting for that in your gaslog? If not, then the mpg you're reporting is probably understated.

Also, do you find that first gear feels tall? I assume the bigger tire would create an effect like that.
I checked & the speedo should be off by 1.56%, so I adjust that amount. 1st seems about the same.
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Old 05-12-2008, 05:07 AM   #17
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I dont worry about the speedo much, you can check that in this area when the police set up a radar display whose purpose is to slow people down.

I found that my previous two Toyotas were 3% over the true mileage, nice way to shorten the warrantee by 1000 miles in a 36k warrantee period.

I confirm my odometer accuracy by using the mile markers on the interstate highway. In 50 miles my odometer read 49.5 so I just adjust the odometer reading by .05%, 1 mile in 200.

I understand GPS works nice but I would think it would not include increased distance due to elevation changes.

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Old 05-12-2008, 08:31 AM   #18
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monroe, it used to be that fueleconomy.gov had two EPA ratings for the two different VX models--one was SIL (shift indicator light) and the other was not. The one that wasn't had substantially worse EPA score. I don't recall if I read on the website that the test driver has to shift earlier when driving the model with the SIL, but if I didn't, then I assumed that the VX without the SIL in its description had a lower EPA score because it was being shifted at a "normal" or higher RPM when test driven, than the VX with SIL in its description.

I don't think the <2% taller gear ratios from larger non LRR tires are off setting the fuel economy loss of not riding on the normal sized LRR tires. The higher ground clearance is enough to offset any gains from <2% taller gear ratios. So, therefore, riding on the original LRR tires gives a better EPA score. This isn't my idea--someone else had made a post about why the VX has such great EPA numbers, using these reasons (or at least the original LRR tires that came on the car as the main reason)

I also plan to get proper sized LRR tires for my car if mine ever need replacing (they're quite new at the moment)

I'm actually not sure about this, but it makes sense given the slippery shape of the coupe. I also read somewhere on these forums (I think it was TomO) that the VX hatch design causes turbulence which causes drag--which the coupe model's design doesn't have. Driving the coupe, without touching the tires, it rolls better than mine did at 45psi. At 60psi, my VX only now rolls about the same as the coupe does, although this could be due to my ball bearings that aren't rolling smoothly, but everyone I asked about that tried to assure me it wouldn't have a noticeable effect (although someone made a post about relubing their ball bearings and the car rolling better afterward, so I dunno)

You're right, I forgot about those things, and they make a small difference. Before I knew the term hypermiler, the website gassavers, or anything about tire pressure and aerodynamics, I did a 500 mile tank over about a week or so period in the 1994 Civic 2 door coupe -half or more of those miles were on the highway- driving around 60-65 (top speed of about 70) and lots of short trips and cold starts, but it was summer time-- and I averaged 52.5mpg. Now granted I filled up at a different pump in a different state, but it was an 800 foot elevation increase from where I first put fuel in and I had gone up and down many hills. Don't get me wrong, though, I was driving to save gas! And I think at the end of the tank I was doing some P&G although I didn't know it as that at the time. Anyway, 52.5mpg is about what I'd get in my VX if I left the tires alone and drove to save gas. I'd almost prefer the DX gearbox for reasons I've already stated--because at 60mph, an extra two or three hundred RPMs on the tach isn't going to offset the substantial gains I get with close 1st, 2nd, 3rd, 4th, and 5th gears.

Let me enter into a tangent on the issue of gear ratios. Unless you are going to be doing literally 60% or more of your miles on the highway, or above 55-60mph, you are going to be getting worse mpg with the tall gear ratio. In my VX I have to give it extra clutch and gas every time I start it --wasting fuel-- then I have to climb to 2000rpm in first and 2nd gears, and I often have to drop into 1st gear where in any other car I'd be able to remain in second. I could go the same speed in 2nd gear in the DX as I could in 1st in the VX. If I had the close gearbox of the DX, given my driving habits of about 40% at 60mph and the rest less than 60mph, the one or two mpg lost on the highway because of the few extra hundred RPM is not going to outweigh the losses in feul economy dinking around town--and everyone has to dink around town. I'd be able to keep my RPMs below 1500 with the DX transmission no matter what gear, except for 5th--but then I'll just have more incentive to P&G. I think a happy medium would have been if they had made 1st gear short, 2nd and 3rd gear close, and 4th and 5th gear farther apart, so I'm not shifting at 2000rpm to go into 2nd and 3rd gear, and then only 1400rpm to go into 4th and 5th gear. It should be geared with 1600rpm shift points across the board and still have the same tall 5th gear ratio.

You cannot be very gentle with the throttle going up a hill though. If you do, then you bog down at 1000rpm. So this is how I've been approaching hills--highest possible gear while flooring it or near flooring it, rather than one gear down so I'm going up the hill at 1700rpm instead of 1400rpm. Lean burn at 1700rpm or full enrichment at 1400rpm? Seems lean burn might be better. 300 more RPM is only about 16% faster--so not sure if lean burn is more or less than 16% more efficient than full enrichment (I assume it's more than 16% more efficient) Again, need to know the horsepower output while maintaining lean burn as compared to the hp output when flooring it.

but lugging or straining the transmission is worse for the car than riding it a few hundred rpm higher.


Quote:
Originally Posted by monroe74 View Post
1993: "when the EPA does the test for that car, the shift light makes the drvier shift earlier than he is shifting when testing the mpg of any other car"

Really? Are you sure that EPA runs the test that way?

"those LRR tires that the VX originally came with and still exist, probably, on only one VX"

It's true that most VX owners seem be running 175/70. But the effect is probably mixed. The tire makes gearing taller, which means a speedo error of more than 2%, which means that many VX mpg claims are probably understated, by that amount. The taller gearing might also make real mpg higher than what you would get with a smaller tire (aside from making observed mpg lower than real mpg).

Anyway, it looks like tirerack has Sumi 165/70 available, so it seems possible to get back to stock, if someone wants to do that. I intend to do that when my 175/70 Sumis wear out.

"They (the EG coupe) have significantly better aerodynamics [compared with the EG hatch]"

Really? Are you sure? The VX has a coefficient of drag is 0.32. That's pretty low.

Also, I think you're incorrect to suggest that all the VX has is lean burn and LRR. You're leaving out VTEC-E (which is something separate from lean burn). There's other stuff too, like gearing, and various weight reductions. A good technical listing of various VX FE ingredients is in this pdf.

"then it makes sense it would be better to run at a higher RPM (thus a lower gear) to maintain lean burn than being at the lowest possible RPM and being in full enrichment mode"

I think high gear is always going to be better. I'm using a DMM as a lean-burn monitor, and it's certainly possible to maintain lean burn in a high gear, provided you are very gentle with the throttle.

But I still have a question very similar to yours. Being gentle with the throttle is at odds with my normal P&G technique, which is designed to minimize pumping losses. I raised this question here:

http://www.gassavers.org/showpost.ph...&postcount=147

"I probably should get in the habit of maintinaing lean bur at higher RPM as this is much better on the motor and transmission than always pushing the car at the lowest RPM."

I don't think so. Wear is roughly proportional to number of revs. Your expected engine lifetime can be expressed as a rev count. Lower revs per minute means lower revs per year, which means more years before your engine runs out of revs.
It's a small travesty that no VX owneres on here have a SuperMid. If they did, they'd answer some of these lean burn questions!!! Imagine if every VX owner on this site had a SuperMid. We'd all be VX masters of hypermiling. Now I really want to know what my mpg is when in lean burn and when in full enrichment mode. poop. I guess I could get a SuperMid, but then I'd have to pay someone to install it cause I'm about as mechanically inclined as a chimpanzee.
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Old 05-12-2008, 09:19 AM   #19
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In the winter I tend to get around 42-44mpg, last summer I averaged 47mpg, my vx has 250,000 miles on it although it has 195psi compression I'm sure there are parts of the engine that have enough wear that they hurt my mileage, my vx also has all the dealer options like the passenger side view mirror, mud flaps, side molding, after market sun roof, and parts of the a/c system are still in the car although the compressor is removed.
I also live in an area that has number of stop signs and stop lights at the bottom of good hills, this became very clear while driving my comuti-car I have to ride the brakes going down all the hills and come to a complete stop at the bottom, then start going up the next hill and my battery doesn't last any wear near as long as if I stick to a straight stretch.
So I would like to get better mileage and I try but so far my best idea is to use my vx less.
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Old 05-12-2008, 10:38 AM   #20
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imz: "why are there so few instances in this timing map where it's closed loop?"

Good question, it does seem odd.

Maybe because it's a timing map, not a fuel map. Maybe the latter would look very different, in this regard. Just a guess.
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