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legitstreetcars 11-11-2019 06:50 PM

My 40 MPG Corvette is going well but I need help
 
Hey everyone, my name is Alex and recently I made a video on my YouTube channel on building a 40 MPG C5 Corvette that sacrifices nothing. Before my YouTube career, I was a long-time member here under Sprayed01. I daily drove a Chevy volt for 4 years, and before that I was ecomodding a Saturn SC2. I also just rebuilt a Tesla so I'm into a little bit of everything.

Anyway, if you watched that video I have another coming out this Saturday on how we tuned the car for lean burn. Check out the video but basically I have it running at about a 16.5 afr when just cruising on the highway at 60mph. We tested it on the dyno at a few different afrs and this was the best as far as it feeling totally normal. Too lean and you could tell it was down on power. We also raised the timing.

Here's my question. I want to give mileage results in most of the videos I make on the car since I'm going to be making changes and then testing. I need to figure out the easiest method of calculating mpg after each mod. Now I fully understand the way to go is filling up, driving until it's almost empty and then filling up at the same pump and calculating with the amount of fuel used. The problem is this car will get over 700 miles to a tank so I can't just take a mini road trip after each mod to see if we've made a difference.

Do you have any tips here and how accurate is the mpg display in the cluster? I know it's probably not perfect but what would be a minimum distance I could drive and be able to give a decently accurate result?

Ultimately I will highway cruise it for hundreds of miles on the highway after a few more mods to give everyone a final result but I need something in between.

Thanks, everyone!
Alex

legitstreetcars 11-11-2019 06:51 PM

https://www.youtube.com/watch?v=aRbKIrjIg9k&t=176s

Fat Charlie 11-11-2019 08:15 PM

OE cluster MPG displays are about as accurate as a presidential hurricane forecast.

https://encrypted-tbn0.gstatic.com/i...eifbJWEPoPDese

Get a ScanGauge or UltraGauge, spend some time getting it calibrated, and then use the short trip measurement to ABA test your mods.

MeteorGray 11-12-2019 08:25 AM

Is that a map of the 57 states?

teoman 11-12-2019 09:45 AM

With torque pro you can log to a mobile phone and mail yoursel frselts

2016 Versa 11-12-2019 10:12 AM

As it's already been stated most MPG displays are very optimistic. The one in my Nissan Versa is consistently off by 5-10%. Probably your best bet is to get a Scan Gauge or Ultra Gauge calibrate it as close as possible over a few tanks then start your mods and testing. Even with the calibrations there may be some error but will probably be minimal.

Daschicken 11-12-2019 11:16 AM

Scanguage accuracy is limited, given that it assumes a constant AFR. The gauges and access to engine data is nice, but having something that taps into the actual fuel injector pulses like an Ultragauge would be great.

The testing really depends on what kind of mods you are doing. If it is engine related, then you really need an ultragauge or similar for optimal accuracy. If it's aero and tires related, then a coastdown test could give you the data you are looking for.

EDIT: MPGuino, not ultraguage!

My rental sentra had an MPG gauge that varied from 6.8-12% optimistic from the two fillups I did with it. :eek:

ennored 11-12-2019 12:17 PM

Quote:

Originally Posted by Daschicken (Post 611503)
Scanguage accuracy is limited, given that it assumes a constant AFR. The gauges and access to engine data is nice, but having something that taps into the actual fuel injector pulses like an Ultragauge would be great.

UltraGauge calculates fuel economy the same way the ScanGauge does.

(No idea why they do it this way. Fuel flow data is in the OBD datastream, use it!)

darcane 11-12-2019 02:24 PM

Welcome Legit,
As you may have noticed, we already found your video and talked about it.

One thing you were wrong on in the video is that Honda has sold numerous cars that legally operate in Lean-Burn mode. I currently have one, a 2001 Civic HX. On this car, the Ultragauge does not properly compute the fuel economy when it is in lean burn mode. I suspect it would be off on your Corvette as well.

I think focusing on some of the hypermiling techniques might get you to your goal. This does nothing to modify your car away from being a performance car, and can basically be turned "on" whenever you want. I used to have a '94 Corvette that I regularly got 29mpg hwy with before I knew anything about hypermiling. With those techniques, I'm sure I could have gotten in the mid/high 30's.

Good luck with your project!

Daschicken 11-12-2019 03:48 PM

Quote:

Originally Posted by ennored (Post 611505)
UltraGauge calculates fuel economy the same way the ScanGauge does.

(No idea why they do it this way. Fuel flow data is in the OBD datastream, use it!)

I guess I was thinking of the MPGuino, not the ultragauge... :confused:

Ecky 11-12-2019 04:39 PM

Quote:

Originally Posted by Fat Charlie (Post 611476)
OE cluster MPG displays are about as accurate as a presidential hurricane forecast.

https://encrypted-tbn0.gstatic.com/i...eifbJWEPoPDese

Get a ScanGauge or UltraGauge, spend some time getting it calibrated, and then use the short trip measurement to ABA test your mods.

If OP is running anything but stoichiometric, a Scangauge or Ultraguage will be really inaccurate too, as they don't use air-fuel ratio in their calculation. The way to get accurate numbers in a lean burn vehicle is with an MPGuino.

slowmover 11-12-2019 09:38 PM

The display number is relative. As a value. Mines off 11% at 60-mph. A glance tells me how I’m doing after correction. The main value is in checking against current road conditions. As a tank for me is in excess of 700-miles, the display rarely is left alone.

As to mpg:

A fuel stop 50-60 miles out from home. Warmup (including tires) is done. Fill to first auto shutoff. Then, a drive of 100 or more miles. Make the midway turnaround at a deserted crossover to avoid stopping.

Run about 62-64/mph. Keeps you under commercial traffic, but not so they jam up behind you. 100% cruise control use. No lane changes. Cancel cruise to get groups around you (drift down to 55; use terrain to re-engage cruise: let the computer handle the drivetrain). No accel or decel. Note exceptions.

Back to same pump and refill same way.

A baseline which anyone can copy. This is the most important consideration.

.

mikeyjd 11-17-2019 11:48 AM

Corvette For Prius Fuel Economy & Z06 Power With LEAN BURN MODE! Project 40 MPG EcoVette!

https://www.youtube.com/watch?v=keGz...UpVH02it16%3A6

Hersbird 12-12-2019 05:32 PM

https://m.youtube.com/watch?v=vNIZ25eBMco

hayden55 12-13-2019 08:09 PM

I find it hilarious that this guy was a lurker on the forum already and we had no idea. He even had a thread going back in March about it. lol
At least he's going in the right direction now. Turning an LS motor into an Atkinson cycle mimicking motor was pretty lame.
He's not wrong though. I've always dreamed about the 40mpg C5 starting from when I joined this forum around 13-14.
Those cars were doing 300hp and 30mpg way before the v6 muscle cars!

ksa8907 12-13-2019 10:24 PM

To be as accurate as possible you will need to measure the fuel flow (hopefully returnless?) Or maybe have a separate fuel source/tank that is easier and more accurate to track usage?

Tahoe_Hybrid 12-14-2019 02:32 AM

Quote:

Originally Posted by 2016 Versa (Post 611499)
As it's already been stated most MPG displays are very optimistic. The one in my Nissan Versa is consistently off by 5-10%. Probably your best bet is to get a Scan Gauge or Ultra Gauge calibrate it as close as possible over a few tanks then start your mods and testing. Even with the calibrations there may be some error but will probably be minimal.

my average is off mine says 23.2mpg but pump calculation say 25.5 to 26.9mpg...Highway


my best for the 6.0L v8 was 31MPG in the city at a steady 43mph hit almost every single green light (CVT mode runs at 1,050RPM at 42MPH)

it's really hard but you can get it running in lean mode it's very hard to keep it in lean mode slightest hill or bump in the road kicks it out




Best combined was 28.7MPG


I think a new HV ⚡ �� battery will get me to 40MPG+ on this V8...




11 years old yep toast...

I fill up at the same pump everytime from now on i think i was getting scammed at a mobil station they were cheating me upwards of a gallon of gas.. for the first 2-4$ it's "Slow"



If I turn off Hybrid mode it only gets 12.8MPG City :eek:



You should swap out for a taller gear ratio like 2.93 or taller tires.....be sure to get the speedo programmed.... this will lower the RPM of the engine.... there for save gas at highway speeds

Mustang Dave 12-19-2019 10:11 PM

Without actually logging miles and gallons at fill-ups, his numbers are meaningless. I filled my Mustang on my way home one evening, and my MPG average display showed 45.x MPG when I got home. (The trip was all downhill) I log EVERY fill-up. My numbers are legitimate.

talonts 12-20-2019 12:51 AM

Honestly, without a separate tank, your (and others') "solution" of filling to the first click, even at the same pump, is generally useless.

I can watch the pulsing of the fuel in the hoses to the fillers on cars and see that the more cars there are filling at once, the more sensitive the shutoff valves are. They can also be temperature sensitive. You'd have to hit a pump when the station is deserted, run your tests, hit it again when deserted, and have the outside temps the same. Even then, there is ZERO guarantee that "first click" will lead to the same fuel level both times.

You either fill the tank ALL the way up, possibly destroying your vapor recovery system (depending on design), or you get a separate calibrated tank/pump to run your tests from.

Edit: Todd Day and I played around with fuel maps on our 90 Talons in the late 90s/early aughts, and while lean burn obviously helps a lot, the fastest gains were from extending the closed loop tables as far as possible, as that helped in all upper rpm situations. Which was very difficult on the stock ECU, as making room for those extended tables required removing other code, that chip was PACKED full for the 90-94s.

I do love your setup though, best of both worlds. I'd love to do the same with an LS/LT motor in the future in a transplant.

You want to basically add any power mod you can that involves volumetric efficiency, as that will boost power AND mpg. Long tube headers probably aren't going to help much at 1-2K, though...

Fat Charlie 12-20-2019 06:01 AM

Quote:

Originally Posted by talonts (Post 613614)
Honestly, without a separate tank, your (and others') "solution" of filling to the first click, even at the same pump, is generally useless.

What it guarantees is that you're limiting your variables down to one piece of equipment and spreading its flaws over the widest number of miles possible.

OE displays are feel-good instruments. SGs and UGs need to be calibrated. The best independent measurement we have is a gas pump. It's regulated, inspected and certified for accuracy and you can maximize consistency by using the same one under as similar conditions as you can.

Nothing's perfect, but pointing that out and then claiming that onboard measurements covering a gallon or two are somehow more valid is acting like our politicians.

Big Dave 12-20-2019 10:47 AM

I never trusted one-tank fill-ups for accuracy. I used four fill-ups. In my case that was about 1,600 miles.

But then, I had a long commute.

Mustang Dave 12-20-2019 08:23 PM

Quote:

Originally Posted by Big Dave (Post 613625)
I never trusted one-tank fill-ups for accuracy. I used four fill-ups. ...

I agree. A single fill-up over 33 MPG may be due to exceptional circumstances; or it may be due to a short fill. It doesn't establish a trend.
6 consecutive fill-ups over 33 MPG could possibly indicate a trend.
(Then cold weather and Winter fuel arrived.):p

talonts 12-21-2019 12:59 AM

Quote:

Originally Posted by Fat Charlie (Post 613617)
Nothing's perfect, but pointing that out and then claiming that onboard measurements covering a gallon or two are somehow more valid is acting like our politicians.

Yeah, well, lying about what I said is definitely "acting like our politicians", so...

Fat Charlie 12-21-2019 06:26 AM

I'm sorry I associated you with our politicians. I zigged when I should have zagged, and you weren't calling onboard measurements more accurate (except for a physically full measurement, which you weren't recommending).

That's the fun thing about multiple threads spanning time, things can get confused. I screwed up and acted like our politicians. Sorry.

MeteorGray 12-21-2019 09:55 AM

I don't judge a car until I've got a number of fill-ups under the cap. The more evidence added to the pool, the more confidence in the conclusions.

For instance, now that I've got 100 refills on my 2015 Mazda3 2.0L automatic, I can confidently say I've got a car that is delivering over 44 mpgs achieved mostly on the highway for a lifetime-so-far fuel cost-per-mile of 4.6 cents.

I consider each refill as the latest iteration of a track record that becomes more valid every time I fill the car. Any significant deviation from that track record at a refill means that I start looking for reasons: A strong headwind? A brake dragging? A malfunctioning engine computer?

I do use a ScanGauge, but only as an interesting indication of fuel mileage under varying conditions. My gauge is usually within about 2% of actual accuracy, which is good but not as good as counting gallons at the station.

Hersbird 12-21-2019 12:32 PM

I think his test was long enough to reasonably claim he got 40 mpg out of his Corvette. If you watch the video you see he could have done much better. I'd say he should repeat in the summer on a more deserted road, run lower speed with more tire pressure and go for 50 mpg.

diesel_john 12-23-2019 10:02 PM

I go to lean-burn by reducing the voltage to injector power. I put a 0-100 ohm 100 watt rheostat in series. ( Grainger). Use 0 ohms to start.(choke). lol. When warmed up dial up the ohms till the power drops off, then dial down the ohms if I need more power. Add kill a switch to engine brake or coast.
Of course, this makes any data based on pulse width useless.
This works well on throttle body injection. Dont mind error codes as long as the processor dont mess with the ignition timing on the newer systems. {knock}
I have tried fuel flow meters to a small reservoir by the engine but fuel temperature changes have to be controlled or compensated for. Many gas stations dont compensate for temperature.
Fuel consistency is a problem now days I dont even know what Blend I am buying today. It changes every day with the price of crude.
So the fuel mileage is useless on the E85 systems. A gallon of what per mile?
Strain gages on a drive shaft would be good for ABA tests. Read torque directly.

Lingenfelter did some mods to reduce drag. splitters, skirts, dams, etc.

Keep in mind the exhaust system is air cooled.

hayden55 12-24-2019 01:46 PM

Plus he did the test while it was 20F outside. That's a big difference in highway mileage with the Prius. I bet if you convert the math to 70F and 70mph he's almost at 37 ish mpg driving like a normal person.

Hersbird 12-24-2019 04:52 PM

Quote:

Originally Posted by hayden55 (Post 613840)
Plus he did the test while it was 20F outside. That's a big difference in highway mileage with the Prius. I bet if you convert the math to 70F and 70mph he's almost at 37 ish mpg driving like a normal person.

The cold makes it worse and he was going 70 mph for a bunch of the loop when he wasn't stuck in stop and go traffic, and got 40. That's why I say lean without even more, slow it down, and do it again in the middle of summer on an open back road and go for 50 mpg

hayden55 12-25-2019 01:20 AM

Quote:

Originally Posted by Hersbird (Post 613854)
The cold makes it worse and he was going 70 mph for a bunch of the loop when he wasn't stuck in stop and go traffic, and got 40. That's why I say lean without even more, slow it down, and do it again in the middle of summer on an open back road and go for 50 mpg

Ah okay. I skim a lot of tech videos. I saw him going 60 at the beginning and also in the last video so I assumed he did it the whole video. Oops lol

slowmover 12-25-2019 03:46 PM

As noted above, consistency matters, not perfection.

MPG isn't really a goal. It’s in knowing the fuel cost expressed as cents per mile.

Cars are about practicality. More than one per household is where it gets out of hand. There’s not even a reasonable attempt to try this, yet it was the norm right into the 1960s.

There are minimums to meet in re safety (design + size) which happily correspond with what’s needed for a household.

Specification, matters most. Past that is the detail of circumstance: climate, terrain and driver motivation. These are fixed, for the most part.

Fuel burn is just a trend. How it’s monitored doesn’t mean much. It’s less than half the cost of a vehicle, on average (any type). The trend is about VEHICLE USE as to what matters.

That’s the other part ignored. There are a dead-minimum number of places to stop for which one requires a car. That’s the MPG loop that counts as the car will be in constant service to & from those locations. Highway trips are a laughable “worry”.

It’s not just avoiding cold starts. It’s avoiding the use of an empty vehicle altogether.

How accurate a fuel pump is or isn’t , as FC notes above, relevant to the trend itself. Especially on a car that couldn’t be any more impractical.

1). Where’s the annual miles reduction from Square One? (the decision to emphasize economy)?

2). Where’s the upgrade to vehicle weather-proof storage?

3). Where’s the savings account to cover ALL TRANSPORTATION EXPENSES as a car is only one category. The weekly family expense over a years time?

4). What’s the expected increase in vehicle component life? Tires, brakes, steering, etc? What’s the projected life extension at a lower vehicle expense (but temporarily increased by expense of a garage) to lower THE LIFETIME EXPENSE?

5). What’s the projected increase to Net Income as a percentage once analysis & remedy are implemented?

Buying gas is just use Fuelly. Be consistent as with all else. But it’s the “all else” as above that matters. On a car that’s ridiculous, the whole exercise is pointless.

“Claims” are trends. Consistent use. So long as the owner isn’t disciplined enough to take the driver out of the equation (anyone can replicate it in his car), any claims he makes can’t be backed.

As MG notes, it’s A LOT of fill-ups to make an accurate trend. It’s at least a year to cancel weather effects. Afterwards, anyone should be able to match it with minimal rules to follow.

Has the Corvette owner — after 50-miles of warmup — scaled the car with full fuel (dialed in tires based that data) and then made a 2-300/mile Interstate
roundtrip at 58-mph on cruise control? No acceleration, braking or lane-changes except as the law requires. Zeroed-out driver inputs.

He hasn’t? Then there’s not even a baseline against which to work. Much less make claims which aren’t suspect. (Good intentions ain’t the thing).

.

Hersbird 12-25-2019 09:00 PM

Well he sold the car now for $8800 so there will be no more tests. Pretty good deal for a clean C5. Maybe the next owner will end up here.

talonts 12-29-2019 01:43 PM

Quote:

Originally Posted by Fat Charlie (Post 613683)
I'm sorry I associated you with our politicians. I zigged when I should have zagged, and you weren't calling onboard measurements more accurate (except for a physically full measurement, which you weren't recommending).

That's the fun thing about multiple threads spanning time, things can get confused. I screwed up and acted like our politicians. Sorry.

No worries, and thanks for the reply.

Tahoe_Hybrid 01-02-2020 04:33 PM

Quote:

Originally Posted by talonts (Post 613614)
Honestly, without a separate tank, your (and others') "solution" of filling to the first click, even at the same pump, is generally useless.

I can watch the pulsing of the fuel in the hoses to the fillers on cars and see that the more cars there are filling at once, the more sensitive the shutoff valves are. They can also be temperature sensitive. You'd have to hit a pump when the station is deserted, run your tests, hit it again when deserted, and have the outside temps the same. Even then, there is ZERO guarantee that "first click" will lead to the same fuel level both times.

You either fill the tank ALL the way up, possibly destroying your vapor recovery system (depending on design), or you get a separate calibrated tank/pump to run your tests from.

Edit: Todd Day and I played around with fuel maps on our 90 Talons in the late 90s/early aughts, and while lean burn obviously helps a lot, the fastest gains were from extending the closed loop tables as far as possible, as that helped in all upper rpm situations. Which was very difficult on the stock ECU, as making room for those extended tables required removing other code, that chip was PACKED full for the 90-94s.

I do love your setup though, best of both worlds. I'd love to do the same with an LS/LT motor in the future in a transplant.

You want to basically add any power mod you can that involves volumetric efficiency, as that will boost power AND mpg. Long tube headers probably aren't going to help much at 1-2K, though...

i use the same pump it's pretty accurate since in California it has a return vapor line so all the vapor gets sucked out of the tank

Tahoe_Hybrid 01-02-2020 04:38 PM

Quote:

Originally Posted by talonts (Post 613614)
Honestly, without a separate tank, your (and others') "solution" of filling to the first click, even at the same pump, is generally useless.

I can watch the pulsing of the fuel in the hoses to the fillers on cars and see that the more cars there are filling at once, the more sensitive the shutoff valves are. They can also be temperature sensitive. You'd have to hit a pump when the station is deserted, run your tests, hit it again when deserted, and have the outside temps the same. Even then, there is ZERO guarantee that "first click" will lead to the same fuel level both times.

You either fill the tank ALL the way up, possibly destroying your vapor recovery system (depending on design), or you get a separate calibrated tank/pump to run your tests from.

Edit: Todd Day and I played around with fuel maps on our 90 Talons in the late 90s/early aughts, and while lean burn obviously helps a lot, the fastest gains were from extending the closed loop tables as far as possible, as that helped in all upper rpm situations. Which was very difficult on the stock ECU, as making room for those extended tables required removing other code, that chip was PACKED full for the 90-94s.

I do love your setup though, best of both worlds. I'd love to do the same with an LS/LT motor in the future in a transplant.

You want to basically add any power mod you can that involves volumetric efficiency, as that will boost power AND mpg. Long tube headers probably aren't going to help much at 1-2K, though...

i use the same pump it's pretty accurate since in California it has a return vapor line so all the vapor gets sucked out of the tank... I also make sure it's seated correctly other wise it will shut off prematurely.. and put way over the amount, to make sure it does not enter slow mode...

Big Dave 01-22-2020 11:08 AM

Hey, Legit. Can you re-tune a Ford 4.6 in a similar manner to what you did in the 40 MPG Vette? Or are you a strictly Chevy man?

I live in Indianapolis so a trip to Chicago would be easily possible.

Hersbird 01-22-2020 01:33 PM

Quote:

Originally Posted by Big Dave (Post 615759)
Hey, Legit. Can you re-tune a Ford 4.6 in a similar manner to what you did in the 40 MPG Vette? Or are you a strictly Chevy man?

I live in Indianapolis so a trip to Chicago would be easily possible.

He's a YouTube guy more than a make money as a mechanic guy. So what you need is a project that will generate views. Like cutting the roof off a Tesla. A 40 MPG Corvette raises some eyebrows but 10 sec 1/4 mile vettes are a dime a dozen on YouTube. A 40 mpg taxicab probably doesn't get views, but a 10 sec 1/4 mile Taxi might.


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