Tanong lang regarding speed with respect sa rpm

**slip-slick** · April 15th, 2003 12:58 PM

i checked this out last night. for my 97 EK, with racing filter, headers, muffler, 100kph is at 5th gear, 2800-2900rpm, 2 passengers only.

**mbt** · April 15th, 2003 02:30 PM

tama si max... gearing is what affects rpm * speed rather than engine displacement... shorter gearing (num. higher) would give faster acceleration but a lower top speed and a higher rpm at a certain speed (more noise and higher fuel consumption).

**Karding** · April 16th, 2003 05:24 AM

Originally Posted by mbt

tama si max... gearing is what affects rpm * speed rather than engine displacement... shorter gearing (num. higher) would give faster acceleration but a lower top speed and a higher rpm at a certain speed (more noise and higher fuel consumption).

bago lang po ako dito, pero may tanong lang. Shorter gear ratio is fast shifting but not neccesarily a faster acceleration. Akala ko faster acceleration needs more Torque and and Top speed or high end power needs higher HP?! Kung shorter ang gear ratio at mabilis kang mag shift pero wala namang torque, wala ding power sa acceleration. To achieve a higher top speed, kelangan malakas ang HP mo.

**icon** · April 17th, 2003 04:51 AM

does it matter how hard u push the car? And I don't mean literally pushing. :mrgreen:

**RS Sprint** · April 17th, 2003 12:06 PM

A shorter gear ratio (numerically higher) will allow the engine to spin sooner to redline and move the car at a faster rate of acceleration sicne the load to be overcome is lessened and the torque given by the engine is multiplied greater (in effect) due to the short gearing.

Pero it ultimately depends on how well matched the gear ratios are in respect the to the engine's output as well as the road you are driving on. I've driven a 280 wheel HP (about 350-360 HP * the crank) Evo but with similar gearing to mine (4.9 final drive) and it didn't feel that much faster since kulang na yung load sa makina. This was on a level road. A few months after he switched to a different tranny with a 4.6 final drive and taller 4th and 5th gear ratios and the improvement was remarkable, parang all new car siya since the engine output was properly matched to the gearing and hence the load.

So hindi lang torque o HP iyan pero how matched these all are.

**Karding** · April 18th, 2003 12:59 AM

Having said all these, it's not a CAUSATION...its a CORRELATION :wink:

**mbt** · April 18th, 2003 01:07 AM

all things (including the same engine output) remaining equal, a car with shorter overall gearing will accelerate faster but have a lower top speed than the same car with taller gearing...

like, the fact that 1st gear is shorter than 2nd gear in your vehicle is the reason why it accelerates faster in 1st than in 2nd. at the same time, it could be going 60 kph at 6000 rpm in 1st gear while going 60 kph in 2nd gear at just say, 3500 rpm.

**Gian** · April 25th, 2003 03:25 PM

Whoa! very informative!

Have question though, if one plans to change gear ratios from short to tall (or vise versa), what do he need to actually change? And, are the parts that are changed readily available or are they custom made?

I assume that the parts that need to be replaced are specific to the trannies in which they will be placed.

Hope to hear from you guys! Thanks

Gian

:D

**mbt** · April 25th, 2003 07:18 PM

Gian,

i think the easiest way to do that is to swap out your differential gear for one with a numerically lower or higher overall ratio... mahirap yata mag change ng gears in the tranny...

**RS Sprint** · April 25th, 2003 11:43 PM

Really depends on the tranny. Some can have a simple differential change wherein the final drive is tied into it. Others need to replace a set of gears to change the final drive.

Changing specific gear ratios is also possible but is not necessarily applicable for all trannies. As an example, with the Lancer Evo's (4-6.5) tranny, there are 2 different sets of gear ratios from 1st-5th gear available from the factory and 2 final drive ratios also available from the factory, depending on what you will specify if you buy it from a Ralli-Art / MMC dealer, and another 2 aftermarket final drive ratios made by CUSCO and HKS.