Ok, so here's my question. My 99 SH (obviously manual) seems like it runs at very high rpm's in 5th gear, compared to most modern cars. In 5th gear, if I'm goin 40mph, my engine's running at 2k. If I'm going 60mph, my engine's running at 3k, and so on.... My dad says that sounds like the way the older cars were before overdrive became standard on cars. Since my car is a manual, and 5th gear should be overdrive, is there something wrong with my gearing, OR do Prelude's just not have overdrive (seems like the more logical explanation). I know this may be a bit of a dumb question, but help me out here.

 

preludes just have shorter gears

 

You must have just bought your Prelude..... and if so, welcome to the family (wise choice)!

Our cars are geared high, because the engines aren't very torquey, they need higher gearing to keep the RPMs up for the high power band. If you set your cruise at 70mph on the freeway, you will be doing 3500 rpm. Sounds like alot, right? But when you consider the peak hp on our engines is 200@7000 rpm, and the red line is 7500 with the top engine speed of 9000 rpm, it's all relative. Crusing at 3500 rpm in our car is like cruising at 1200 rpm in a Buick.

You will still get overdrive-like fuel economy. It's a different design than alot of cars. If it was geared in 5th to do 1500 or even 2000 rpm at 70 mph, you would have no torque or power, and thus the car might actually stall out!

In fact, keep your car in 5th and slow it down to 1500 rpm.... see what happens!

 

Ahem correct explanation, but we have shorter gears

 

im a 4th gen driver(93si) , and for fuel economy i constantly use fifth gear at speeds like 34-40 mph and up and the rpms are at 1500-2000 and i dont get any problem(i dont have a lot of power in that rpm for acceleration --but i could just drop down to 4th, but im not lugging or stalling?)

is there a problem using fifth gear like that? I thought using the higher gear always yielded the best gas mileage.

thanks any help would be appreciated

 

No problem with using the gears like that..... it is in fact good for economy.

The 5th gens (and 4th gen VTEC models) use shorter gear ratios than 4th gen S or Si (in other words we have different transmissions). At 1500 in 5th gear, I start to lug a little. At a thousand it's almost ready to stall. But on the same token, at 1500 in 5th, our cars are only doing 30 mph.

I usually don't slip into 5th untill I'm at 40 mph.

 

thanks for that i wasnt sure which models had the shorter gearing good that you cleared it up

 

Actually your RPMs have nothing to do with fuel economy, fuel economy has to do with throttle position, If you're using 5th at a low rpm to get yourself up to speed (w/o downshifting) u'll require the engine to work hard thus consuming more fuel (i.e. starting the car from a stop, compared to downshifting to slow down)

 

so should i or shouldnt I use the highest gear possible?
those replies seem to conflict

 

Okay, here it is in a nutshell:

The lower the gear, the better performace

The higher the gear, the better the fuel economy

1st - 3rd gears = good for acceleration and passing, but bad to stay in all the time if you're looking for the best fuel economy.

That's why GM's 6 speed manuals have that 1st - 4th slip if you shift at under 2000 rpm (a pin slides out and locks 2nd and 3rd out).