My 40 MPG Corvette is going well but I need help

[legitstreetcars]

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]

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

[Fat Charlie]

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



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

[MeteorGray]

Is that a map of the 57 states?

[teoman]

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

[2016 Versa]

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]

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.

[ennored]

Originally Posted by Daschicken

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]

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]

Originally Posted by ennored

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...