How does a gear change make your car faster without adding any horsepower?

 

the gears get your car into the optimum rpm range quicker. Even though they do not add horsepower, they allow more horsepower to be applied to the ground.

Steve

 

exactly...think of it this way. a race is not all hp, its hp with time factored in. if you have a car that makes 1000 hp at 7000 rpm, but only 100 hp up to 6999 rpms, think of how long it would take to get to the 'sweet spot'. if it had gears, it will get there much sooner and vamos you are gone! (this is also why torque convertors are awesome).

 

Ok I understand that. The gears will not increase your flywheel horspower. but since it will transfer more power to the wheel shouldnt you get an increase in RWHP/RWTQ.

Lets say we have the same car on the same dyno. one run with 3.42 and one run with 4.10. the dyno will register higher RWHP/RWTQ numbers on the 4.10 run vs. the 3.42. right??????

 

i think what will happen if you have shorter (numerically larger) gears like 3.73s or 4.10s is that it will just reach the speeds a lot faster. I dont believe dynos measure the time it takes to reach a certain speed but how much force is applied to the drums.

i think thats how they work. correct me if i am wrong.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by BLMONGOOSE:
<strong> Ok I understand that. The gears will not increase your flywheel horspower. but since it will transfer more power to the wheel shouldnt you get an increase in RWHP/RWTQ.

Lets say we have the same car on the same dyno. one run with 3.42 and one run with 4.10. the dyno will register higher RWHP/RWTQ numbers on the 4.10 run vs. the 3.42. right?????? </strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">No, 4.10's will lose hp on a dyno vs. 3.42's. It takes more horsepower to turn them, therefore you lose power.

At the track, 4.10's will allow you to turn more rpms. Thats where the mph gain comes from.

I'll give you an example. This for an A4 w/ 4% converter slip, 26" tires, 4900rpm shift extension w/ 3.42's, 5200rpm shift extension w/ 4.10's.

here is your hypothetical rpm range:
4900rpms- 200hp
5000- 225
5100- 250
5200- 275
5300- 300
5400- 325
5500- 350
5600- 375
5700- 400
5800- 425
5900- 450
6000- 475
6100- 500
6200- 525
6300- 550
6400- 575
6500- 600
6600- 625
6700- 650

Situation: from shift into 3rd through the traps w/ 3.42's on a run where you trap 119mph.

you go from 4900rpms-5500rpms when you cross the traps at 119mph. you have applied an average of 275hp to the ground through out that rpm range

switch to 4.10's: you go from 5200rpms-6700rpms when you cross the traps at 121.6mph. You have applied an average of 462.5hp to the ground through out that rpm range.

the point being is that the higher the average amount of hp you put to the ground the higher your mph will be. This is what a gear swap does. Just make sure you gear accordingly to your powerband.

hope this helps out

later,
Steve

 

Thats interesting--So when I go to get my car dynoed this Friday it will read less rwhp than if I had the original 2.73's in it since I had 3.73's installed. I'm really having trouble grasping this concept.

Since you are getting into your optimum powerband sooner wouldn't you put more power to the ground on a dyno as well.

thanks,
Brandon <img border="0" alt="[driving]" title="" src="graemlins/gr_driving3.gif" />