I Got 8 On The Floor and 4 Under The Hood!! Let’s Ride!!

Posted: August 19, 2011 in Powertrain
Tags: , , ,

Eight on the floor and four under the hood, baby! Wait!…..What?! Shouldn’t that be the other way around? Shouldn’t that be 4-on-the-floor? And 8 cylinders under the hood?

Not in today’s world of maximum fuel economy and even more maximum performance. The trend in engines today is that less is more. Fewer cylinders, providing more horsepower, better fuel economy and performance. Trucks that used to have V8 engines now have 6 cylinder and even 4 cylinder engines available. Ford’s top selling F-150 full sized pickup now has more trucks driving off the lot with 6 cylinder engines than with 8 cylinders. And the Ford Explorer that used to sport a 4.0 liter V8 has been replaced by a Ford Explorer offering a 2.0 liter turbo 4 cylinder. Technology that is available today is allowing automakers to produce 4 cylinder engines that can more than hold their own with the 6 and 8 cylinder engines of the 70’s through 90’s. Advancements in fuel injection, turbocharging, valve timing and camshaft phasing allows the small engines to perform like the big engines they compete with when necessary, but sip fuel just like or even better than the weaker 4 cylinders of yesteryear. The best of both times. So next time you hear someone say “Wow! I coulda had a V8!”, you’ll probably find that they are glad they didn’t.

But what about the transmission? Didn’t it used to be “4-on-the-floor”? Yes, but those times have changed, too. The 4 speed automatic has been replaced by the 5 speed automatic, which is being replaced by the 6 speed automatic. But sooner than you can start counting to 6 on the other hand, here come 8 speeds. BMW sedans and SUVs are available with 8 speeds today. Chrysler’s Ram Trucks will have 8 speeds next year, as will Chrysler and some Dodge cars. What’s the point? And where will it end?

Part of what makes the little 4 cylinder engines so good is that they are able to achieve peak torque (rotational force) at very low revolutions. Eight speed transmissions help make that happen. Having transmissions with more gears allows the engine to stay in a range where the torque is high and the car just feels better. Then, when the transmission is in its higher gear ranges and the engine is turning slower, but with high torque, the vehicle can achieve better fuel economy (lower engine speed) while maintaining a better driving feel (higher torque).

That’s enough on this subject, at least until next time, when we’ll discuss 3 cylinder engines and 9 speed transmissions…….Really?………Really!

  1. phbrown says:

    WOW! Great post, I didn’t even know about the dodge trucks. And it is crazy seeing all the ingenuity people are coming up with to achieve higher CAFE standards.

    Just the other day I touched my Dad’s F-150’s grill and realized it was plastic and not metal.

    I do have one question tough. In your post you mentioned how the today 4-cylinders are able to stay more in their sweet spot (higher torque/lower RPMs) due to additional gears in the transmission. But don’t diesel engines also get higher torque at lower RPMs? I know in the USA people don’t like disel but what about other places… Is that the trend? Using a 3 cylinder diesel combined with 8 speed transmissions?

    One last series of related questions (sorry) What is the limit to adding gears to the transmission?
    Does it evenutally reach a point where the additional gears weight doesn’t justify the increase in MPG? Or will companies just switch over to the CVT then?

    • phbrown says:

      Question: with the steer by wire coming out in vehicles do you think it will be feasible for an owner to actually adjust the parameters to their liking?

      follow up: do you think it will be possible for a hacker to adjust the parameters while someone is driving on the highway? Similar to how some hackers hacked into the TPMS system of a car…

      • martinjlm says:

        The answer to your second question is part of the reason for the answer to your first question. In order to safeguard against potential hacking into vehicle control systems in a manner that could induce safety hazards, automakers do not / will not allow for consumer adjustability of the code itself. Some do / will allow customers to select from pre-programmed settings. Sport Mode / Touring Mode / Performance Mode selectors for electric steering and electronically tuned suspensions are already on the market.

        Automakers are held responsible for the vehicle’s ability to meet stringent safety requirements. Allowing customers to randomly change settings could easily result in someone inadvertently making the vehicle unsafe. The automakers liability in this type of situation could become a significant legal issue. Locking out customization nips it in the bud.

    • martinjlm says:

      Very good question! Diesel engines do produce high torque at low rpms and have a broad rpm range where they are at or near peak torque. These aspects of diesel engine operation are what make them so attractive for truck use. They are also the characteristics that automakers try to emulate in the development of more efficient gasoline engines. All modern diesels are turbocharged. This helps produce low end torque. More and more small gasoline engines are turbocharged. To produce low end torque. All modern diesels have fuel injected directly into the cylinder. More and more gas engines are moving to direct injection.

      The industry is moving towards making gasoline engines as efficient as diesels and towards making diesels as clean as gasoline engines.

      As for your other question…..what is the limit for transmission gears. We thought it was 4……no, wait 5! I mean 6. Okay, so Mercedes Benz is working on a 9 speed…..and Hyundai is working on 10. Let’s not forget CVTs……Continuously Variable Transmissions. You could argue that they only have one gear or you could argue that they have an infinite number of gears, since the ratio is, as described, continuously changing. As automobiles change and become more electrified we could see a complete shift (no pun intended) in how the transmission works within the vehicle. This could change how we count gears. For example, I have a 21 speed bike. Arguably, it has 7 gears, each available across 3 tiers. Each tier has a multiplying factor when combined with any of the seven selectable gears. Electric-based vehicles could adopt a similar protocol where the electric motor has x-number of speed positions with a multiplier attached for different terrain conditions.

      That’s a long winded way of saying……we really don’t know.

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