hp gains from gear upgrade/zexel diff.

[FuryCharger]

I have a 3.23 gear as of now, if i were to upgrade to a 3.42 or a 3.73 what kinda gains could i expect? also would it be a good idea to get a zexel torsen differential with that??

[hawgs]

you dont gain any horsepower by changing your gears or adding a LSD

[HAZ-Matt]

No you don't. In fact with lower gears, you're horsepower numbers will go down by a few ponies. You will however accelerate quicker [img]smile.gif[/img]

[hawgs]

Thanks Matt [img]graemlins/thumbsup.gif[/img]

[FuryCharger]

so does that mean ur torque increases?? since u are accelerating faster

[Dominic]

NOTHING increases, its just that you're changing your rpm range for a given speed.

[ June 11, 2003: Message edited by: Dominic ]</p>

[AlienInv8r]

Same horsepower. Think of it like riding a bike. You can start your bike in like 10th gear and it'd take you a bit to get going, but you can hold that gear out a bit longer till you need to shift; that'd be like 3.23's.
Now think of starting in like say 3rd gear. You can get up and go much quicker with the same amount of power as before, but you'll hafta shift sooner to keep pulling; That'd be like 3.73's.
That's how I've been relating gear ratios in my head, they produce the same amount of power, just the higher gears help you to accelerate a bit faster. At least I hope I'm relating this right, someone please correct me if I'm wrong.

[ June 11, 2003: Message edited by: AlienInv8r ]</p>

[HAZ-Matt]

<blockquote>quote:</font><hr>Originally posted by Dominic:
NOTHING increases, its just that you're changing your rpm range for a given speed.
<hr></blockquote>

Oh, are you quite confident that nothing increases? [img]smile.gif[/img]

Torque multiplication is increased. The wheels therefore experience increased torque throughout each gear at every rpm. The increased torque increases acceleration. The increased acceleration means that the engine is reving faster. The increased acceleration within the engine requires more power, so the usable out put of the motor is actually partially reduced. Hence, if you take a car and dyno it, then swap the rear gears for lower ones and dyno it again, you will end up with slightly lower numbers the second time.

Oddly enough, I know that you know all of what I just posted.

[Bliggida]

Thank you HAZ-MATT!

Geez folks. Lower gears multiply the power you have going to the wheels. Gear changes (if you don't account for them) will show up on a dyno! (don't agree with you there Haz-Matt)

A swap from 3.23 to 3.42 is about the same feeling as if you added 12 horsepower.

A jump to 3.73's will feel like a gain of 25 horsepower.

Break it down to simple numbers.
You have a 200 horse engine and a 1:1 rear gear. That means 200HPx1= 200HP going to the rear gear (not counting your driveline loss right now)
But you step up to a 2:1 gear then all the sudden you've doubled your power. 200HPx2=400.

So it would take you 400 horsepower with a 1:1 gear to equal the same amount of power that it would with 200 horsepower at a 2:1 gear.

[HAZ-Matt]

<blockquote>quote:</font><hr>Originally posted by Bliggida:
Thank you HAZ-MATT!

Geez folks. Lower gears multiply the power you have going to the wheels. Gear changes (if you don't account for them) will show up on a dyno! (don't agree with you there Haz-Matt) <hr></blockquote>

No that is the point. When corrected for gears, you will see lower horsepower numbers. Lower gears show reduced dyno numbers of maybe 1-2HP because the engines do infact put out less usable power. The energy needed to rev faster has to come from somewhere.

[Harry94]

All I have to say is get the 3.73 gears and LSD. There's no sense in multiplying the torque at the wheels if you can't get traction. 3.42's aren't worth it if you already have 3.23's.

[Bliggida]

Haz, you realize that between dyno runs it it quite common to see a difference of 5 hp considered to be normal??? That is with the same equipment running the same tune - two different numbers.

1-2 horsepower. That translates to about .5 percent of the whole - HALF of 1 percent. (on our engines, much much less in vehicles that make big power) That could be the difference of you deciding to jump up in the seat at 3,000 RPM as opposed to jumping up in the seat at 4,000 RPM on the dyno. Its so insignificant that it wouldn't make any difference in any race.