this post was submitted on 26 Oct 2023
549 points (98.2% liked)
Technology
59598 readers
3147 users here now
This is a most excellent place for technology news and articles.
Our Rules
- Follow the lemmy.world rules.
- Only tech related content.
- Be excellent to each another!
- Mod approved content bots can post up to 10 articles per day.
- Threads asking for personal tech support may be deleted.
- Politics threads may be removed.
- No memes allowed as posts, OK to post as comments.
- Only approved bots from the list below, to ask if your bot can be added please contact us.
- Check for duplicates before posting, duplicates may be removed
Approved Bots
founded 1 year ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
As far as I know Mazda are the highest with their gas engines that have diesel compression ratio.
Wow, 56%, impressive, although they seem to be roughly in-line with the competition for MPG anyway.
I know, that's what I find weird about it, in the end fuel economy isn't that much better... I haven't checked peak power vs competition though, but I think they have more torque than most? 🤔
It's because fuel economy is heavily driven by vehicle weight, since start from a stop kills efficiency. Cruise effeciency is more about aerodynamics than weight (ask anyone who's ever towed anything - you can really feel the drag above 45mph).
And oddly enough, today's cars aren't really significantly lighter than 30 or 40 years ago. We've just moved the weight from the frame/body setup to unitized body/frame (lighter but safer... And cheaper to manufacture), more safety systems (airbags/computers) and things like heated seats, etc.
Today's 4+ seat SUV often weighs as much as a 1970's 4+ seat station wagon...but with less space inside.
Yes it's about aerodynamics and rolling resistance and weight and you need X torque to overcome all of that at Y speed, but if you are able to generate that amount of torque from less fuel because your engine manages to extract more energy from the same amount of fuel, you would expect the car to have better fuel economy than its competitor with an engine that has worse thermal efficiency... So unless Mazda is doing something really wrong or the return diminishes greatly past a certain point, I don't understand why they don't have much better fuel economy numbers with an engine that has 56% efficiency (compared to as low as 20% for gas engines just 20 years ago!)
How do they pull that off?
16:1 with the latest generation of engines, direct injection does miracles!