Rocket-tabs

[Ecky]

Originally Posted by hayden55

Update?

Here's my data so far, formatted as best I could.





-I didn't move the Rocket Tabs over from my summer tires, so after I switched to winters I was running without.

-My 12v battery failed when the temperature dipped low enough that I needed snow tires. Also that dataset (yellow) was so small you can almost throw it out.

-Winter and summer tires are the same size. Summer are Potenza RE92, winter are Nokian Nordman 5.

Some thoughts:

There's definitely a relationship between temperature and fuel economy. The relationship for the whole dataset is f(x) = 0.09x + 51.9. Or, in other words, a change in 1 degree F results in a drop in average economy of 0.1mpg in my car.

The Rocket Tabs are an outlier in terms of slope. It could have been weather related; by the time I got them on, the weather was deteriorating and we were getting a lot of ugly, rainy days. If cooler days were drier AND rain affected MPG more than temperature, it could produce that negative slope. Still, weird. You could also choose to interpret it that the Rocket Tabs hurt economy when it's warm and help when it's cold, but I doubt that's the case. Or maybe it was just bad luck. Lots of traffic in my commute at the end of the season? I dunno.

Overall, winter tires + supercapacitors delivered better fuel economy (adjusted for temperature) than legendary RE92 summer tires and a normal 12v battery, OR Rocket Tabs. So at least in terms of what my limited data support, Supercapacitors are the real winner here. Want to safe fuel? Ditch the 12v battery.

[mpg_numbers_guy]

Originally Posted by Ecky

Overall, winter tires + supercapacitors delivered better fuel economy (adjusted for temperature) than legendary RE92 summer tires and a normal 12v battery, OR Rocket Tabs. So at least in terms of what my limited data support, Supercapacitors are the real winner here. Want to safe fuel? Ditch the 12v battery.

Are you saying your new (lithum?) battery improved your fuel economy over a standard 12V battery? By how much?

[Ecky]

Originally Posted by mpg_numbers_guy

Are you saying your new (lithum?) battery improved your fuel economy over a standard 12V battery? By how much?

Hard to say exactly since there are so many variables.

-The 12v was probably getting weak weeks or months before and thus causing my charger to draw more power from the engine.

-Charging a lithium battery is more efficient than a lead acid, and charging capacitors is a lot more efficient than that, even.

However I'd say that's largely irrelevant because the lithium battery is behind a resistor so it's not playing much of a role here, it's mostly just keeping the caps topped off when the car is off. You're mostly seeing supercapacitors vs a lead acid battery (which in this dataset declined very rapidly as temperature dropped).

From what I understand a 12v battery will have a resting voltage of around 12.6v. While your car is running, your alternator (or DC-DC converter) is producing a higher voltage than that. This causes current to trickle into the battery, which is turned into heat and lost while the battery is full. By contrast, a lithium battery OR supercapacitors will actually sit at that ~14v the charging system provides. Maybe someone with a better electrical background can provide more or better information.

[Ecky]

I forgot to give you a number!

The delta between winter and summer tires was around -2mpg, but the winter tires had a failing battery AND the dataset was very small, so I wouldn't take much stock in that number. They might actually not be a fuel economy loss over RE92s at all. Nokians are pretty kick-ass tires.

The delta between winter tires with a failing lead acid and winter tires with supercapacitors was ~+8mpg. Again, small dataset and the failing battery makes the numbers of questionable usefulness.

Probably the number you can trust most is that switching from summer tires with a lead acid to winter tires with supercapacitors was worth an improvement of approximately 5mpg, or 10%.

EDIT: Let me throw out that one outlier, which was basically the day my battery failed, and see how the chart looks.

EDIT2: Taking out that lone datapoint, winter and summer tires are very close to each other, and supercapacitors provided a ~5mpg improvement. But, this is based on a VERY small data set.

[Xist]

I cannot imagine gluing something to my tire and seeing greater benefits than smooth hubcaps. Boat tails are supposed to improve fuel economy 10% and so is an alternator delete. Belly pans and other significant modifications are supposed to be 5% or less, so I cannot imagine small pieces of foam yielding results equal to or greater than a boat tail and an alternator delete.

[samwichse]

Originally Posted by Ecky

Here's my data so far, formatted as best I could.





-I didn't move the Rocket Tabs over from my summer tires, so after I switched to winters I was running without.

I bet if you ignore the rocket tabs and do a fit of temp vs summer tires with the rocket tab/non rocket tab data together, you'll get a niceer R^2.

IE: No significant effect from the tabs.

[Ecky]

Originally Posted by samwichse

I bet if you ignore the rocket tabs and do a fit of temp vs summer tires with the rocket tab/non rocket tab data together, you'll get a niceer R^2.

IE: No significant effect from the tabs.

I expect you're right. Definitely a limitation of real-world data though is that variables aren't controlled for.

But, one thing I definitely did not see was an instant 20% boost in economy.

[Natalya]

Any build instructions on the supercaps//lithium 12v combo? Or, rather, what caps and battery to order?

[Ecky]

Originally Posted by Natalya

Any build instructions on the supercaps//lithium 12v combo? Or, rather, what caps and battery to order?

Let's move it over to this thread:

https://ecomodder.com/forum/showthre...ent-36566.html

Some info there already, read through it and feel free to ask further questions. I think if I could do it again I'd probably try ~1200-1800F caps rather than the 3000's and 400's I tried. The 400's were just too small (they'd start the car once, reluctantly), and 3000's are absolute overkill if going to be paired with a small battery, but probably the right size if you wanted to run battery-less.

[euromodder]

Originally Posted by Ecky

-I didn't move the Rocket Tabs over from my summer tires, so after I switched to winters I was running without.

-My 12v battery failed when the temperature dipped low enough that I needed snow tires. Supercapacitors are the real winner here.

Your best MPG on winter tyres (with SC) is still impressive compared to the other combinations
Best is above best summer tyre mpg, and lowest is higher than with summer tyres as well.


Let's see what the Tabs will do in spring, with SCs, but the only graph going downhill is the one with Rocket Tabs - not good ...