A decade ago, why did carmakers...

[RedRooster]

build their transmissions/final drives so that the engines would rev so high while cruising?
I'm currently driving a late 80s Acura Legend, and while this was supposedly a luxury car, why would they insist on making the V6 rev so high on the highway? Cruising at the speed limit, it's turning 2500rpms, and compared to almost all cars within the last 5 years or so, that's awfully high. My friend has a piece of junk Escort, and it runs at 2100 on the highway.
Is the ever lowering cruising rpms due to gas mileage restrictions or something that have been put in place? I'm just curious, perhaps some of the mechanics around here could explain that to me.

 

[dude]

The contract/conspiracy between automakers and oil drillers is finally over! Yipppppeeeeeeeeeeeeeeeee!!!!!!1

 

[mdennison]

My 89 prelude did 4000rpms at 80mph. It is because if it was at 2000rpm, like a mustang, it would bog down...not enough low end juice!

 

[BruNgoLD]

my guess would probably be just better technology and research giving way to more efficient engines...

would make sense, doesnt it?
im sure engines running at 2500 rpms at the speed limit was a low cruising rpm back then?
probably helps to change the oil regularly, etc too

anyone else?

 

[Zenmervolt]

Has nothing to do with the time period and everything to do with the engines. Take a look at the torque and horsepower curves for the engine in your Legend and I'm pretty sure that you'll find out that the engine makes most of its power near the top of the rev band. Sure they could have geared the car differently to lower RPM at cruising speed but then acceleration would have been unacceptably sluggish. My 1988 Accord turns 3,000 RPM at 75 mph, and this makes sense because there is almost no torque produced until 2,500 RPM. There is quite literally a surge once the engine passes 3,000 RPM. The gearing is decided as a compromise between acceleration and cruising, Honda geared the Legend lower because the engine needed to be revving in order to produce torque. It's far from uncommon. In some cases it's a lot more extreme. My 1976 Porsche 914 has a ~4.8 : 1.00 final drive ratio (3.25 : 1.00 is normal, 4.11 : 1.00 is considered very low gearing) and it turns 3,000 RPM at about 65 mph, it all depends upon the engine.

ZV

 

[beat mania]

Speed limit change, dude. I'm sure 50 years from now when you're senile and you forgot about this post you'll be complaining again how you have to rev your 10 year old car to 5000rpm to drive at the 200mph speed limit when cars build 50 years from now only need to rev at 10rpm 🙂

 

[Zenmervolt]

<<Speed limit change, dude.>>

Bzzzzt! Try again.

ZV

 

[RedRooster]

Good point Zemner, now explain this question... 🙂
We have a '75 Monte Carlo, 400ci small block, and it only has a 3 speed transmission(no overdrive at all). No tach, but it sounds like it runs over 2000 on the highway, probably a fair bit more. Why in the world would they make a car with an engine that big(I could pull a new Ram diesel in a tug of war), rev so high? Was that just poor engineering?

 

[fastz28]

How does 2000rpm at 80mph sound?

Good!!

Would you like 28 mpg and 350+ HP to go with that?

Yeah baby!!

Low end torque is what's missing. Where do you get that? Try displacement!!

😀

 

[GMachine]

<< How does 2000rpm at 80mph sound?

Good!!

Would you like 28 mpg and 350+ HP to go with that?

Yeah baby!!

Low end torque is what's missing. Where do you get that? Try displacement!!

😀 >>



Nice! In my 2000 SS, when i'm not speeding, 65 is about 1800 rpm. Try that with f*kcing v-tec.

 

[Thegonagle]

Sigh. Like so many before you, you display ignorance about what VTEC is and what it does.

It is actually able widen the torque band by effectively, instantly ?swapping the cam? while underway.

Try 8000 RPM with the truck engine in your SS.

You?ve got 350 HP at what, 4000 RPM? Can you imagine how much more potential a 5.7 liter engine would have were it able to breathe effectively at 8000 or 9000 RPM? VTEC helps achieve just that.