whats the slowest RPM you can hold/top gear?

[PaleMelanesian]

25 mph, 5th gear, 1000 rpm. It's good enough to gain speed on moderate climbs. I prefer 1200 rpm for pulsing, but sometimes the conditions call for lower rpm and slower acceleration.

[Miller88]

On the flat, I can hold 5th gear at 1000RPM (around 28MPH). According to Ford, this engine isn't supposed to have a load on it under 1250.

[freebeard]

I think that it is affected (not determined) by the number of cylinders, the mass of the flywheel and the stroke.
• A 12 cylinder engine will be firing more than a 2 cylinder at a given rpm
• Ever hear a single cylinder John Deere tractor idle? Fires about twice a second
• Strokers have better low end torque

That said, air-cooled VWs like revs, because the volume of cooling air is related to rpm.

[cfg83]

arcosine -

Originally Posted by arcosine

1200 RPM is 38 mph in my Saturn sc1. I can drive at a constant speed at 20 mph in fifth gear. It bucks a lot at 15. Check that your rubber motor mounts are not cracked.

I have the same 5th gear ratio so it's the same for me. On the flat I can accelerate up from 20 MPH but it is a matter of "micro" accleration.

CarloSW2

[Diesel_Dave]

Getting back to the original question, the slowest rpm at which you can be in top gear is determined by the amount of low-end torque that your engine has and the amount of power required to push the vehicle down the road. For unloaded turbodiesel trucks like mine and Big Dave's it's nearly impossible to lug the engine. With 300+ lb-ft of clutch engagement torque I can run 6th gear at idle speed (800 rpm). That's close to 50 hp, so that's plenty for unloaded cruising on level ground.

[gone-ot]

...on flat land, with A/C on, the wife's Cruze will hold 40 mph at 1400 rpm in 6th gear fine (6 = 0.74:1, final drive = 3.87:1), and that's below the turbochargers' full "in" point of 1850 rpm.

[Quezacotl]

1200rpm at top gear(5) going 40km/h.
Just in the edge that it won't shake. But usually i'll switch to lower gear

[redpoint5]

I grab 6th gear in my TSX at 30mph when cruising. She would go about as low as 25mph in 6th at around 1100 RPM.

You would think with 6 gears, they could have left the last gear tall, but no such luck.

[PaleMelanesian]

Originally Posted by redpoint5

I grab 6th gear in my TSX at 30mph when cruising. She would go about as low as 25mph in 6th at around 1100 RPM.

You would think with 6 gears, they could have left the last gear tall, but no such luck.

Honda is especially bad about that. They put your 6th gear the same as my 5th, and made all the ratios closer in the middle.

[serialk11r]

Today logged a short trip home (engine warmed up already though) and I just finished looking through the log. Idling in 5th gear at 600rpm (normal idle is 680rpm) going about 11mph = only 45mpg. Idling in 4th gear looked to be about 50mpg instead of 45mpg. However 900rpm in 5th gear or about 16-17mph was 55mpg, 1400rpm ~26mph appeared to be about 60mpg but I didn't have straight road with no traffic to hold speed at.

Will try going at low speed in 4th to see if the numbers look better when the engine is over 1000rpm, and try to log some consistent 30-35mph travel to see if the FE numbers look better. I hope this little car can do better than 55mpg...

Looking at gph values is pretty intriguing, 0.23gph idle seems like a tiny amount of gas until you realize that it takes less than twice of that to be actually traveling at 25mph. My 1.8L engine is too big!