I know this topic was discussed about a month ago. I have decided to stay NA, and want to stick with my 15 inch TE37's. I know the gear was made for a 16 inch wheel, but would running a 15 have any more benefit?

 

better than the 4.4.... i plan on running an ats final wid some 13 tires!!!


edit: changed from rimz to tires cause rim size has no effect on over all rotating size.


[Modified by ITR764, 9:45 AM 9/16/2002]

 

Thanks for the reply...

 

JDM 4.785 with 15" would be a perfect combo. At least in autoX, 4.785 would be ideal... ATS requires too much shifting at an autoX course from what I've seen.

 

Nice, but what the rim diameter has to do with the final drive you choose?
Final drive is one thing and rim diameter is another thing. As long as you keep your overall diameter within the stock spects (read: tire profile), you're good.
By having a FD and chooseing different rim dia, i.e: 15", 16", 17", and installing the right tire dimensions, should keep you in the same ratio. The only thing that change is weight. When you change the the FD to a higher one, you have more torque and acceleration. So, no matter what rim dia are you using, the change is the same.

In the case of 9K racer, when he changes his FD to a JDM or to a ATS using 15" wheels, he'll have a very responsive car and he will have to learn to control the power at an auto-x event.

 

i ment tire size... i just wasn't tring to get too technical.

 

you dont get more torque from a FD.

you just use the available power more efficiently for acceleration.

 

Yes you get more torque to the wheels. The draw back is a reduction in RPM at the wheel. The power stays constant.

 

you just use the available power more efficiently for acceleration

 

If you change the FD from the stock ratio of 4.4 :1 to a ratio of 4.785:1 or 4.929:1 you will get more torque to the wheel. Which will give you better acceleration.

Gear reduction 101:
If we foget about the loss of HP through the mechanical components:

1- The HP stay constant from the input shaft to the output shaft
2- In order for the HP to stay constant during the rpm reduction caused by gear ratio, the torque must increase.

The real torque at the wheel for each gear ratio can be obtain using the following:

First gear torque: Engine torque x first gear ratio x final drive ratio x mechanical efficiency of the gear box

Second gear torque: Engine torque x second gear ratio X final drive ratio x machanical efficiency of the gear box

ETC...

If you increase the final drive ratio, you will increase the torque output for each gear.

 

You're a tool.

 

..Yet another Honda-tech debate gone bad

 

Soupnazy: Why am I a tool (I don't get what you mean)?

9KRacer: Why do you say that this debate as gone bad ? Nobody (not me at least) is aggressive. Just bringing a point of view.

 

"you will get more torque to the wheel"

Changing your FD will not change the amount of torque your are producing.

As soup **** said you will use the advialalbe power more efficantly, but chaing your fd is not going to majically cause your engine to pur more torque to the wheel.

 

JPP: thanks for a good explanation.

9kRacer - I should've said for USDM ITR wheels, you'd benefit from 4.785FD... due it's weight and not due to it's wheel diameter.

 

There is nothing magic about it. It is basic physics.
The engine does not produce more torque. But the torque produced by the engine is increase through the different gear ratio (in the case where a small gear drive a bigger gear). If you modify one of those ratio, you will modify the output torque.


[Modified by JPP, 1:15 PM 9/16/2002]

 

Thanks guys..Thats all I wanted..

 

All anyone is saying is that the actually output of the engine at the crank is unchanged.

All you are doing is making better use of the available output.

 

[QUOTE]All anyone is saying is that the actually output of the engine at the crank is unchanged.[QUOTE]


That is correct


[QUOTE]All you are doing is making better use of the available output.[QUOTE]


Well, the torque at the wheel will be higher (measurable) for all five gears ratio
If that is what you are looking for then yes it is a better use of the available output. However you are sacrifying top speed for each gear.

If you are racing on a very twisty road where you never see top speed in fifth then you would be better to use an ATS 4.929 FD and take advantage of the extra torque at the wheel to get out of the corners.

However, if you are racing on a super speeway oval, where all you see is top speed in the top gear then you would be better off with a 4.4 stock FD.

The "better use" of the engine output is relative to what you need.


[Modified by JPP, 3:18 PM 9/16/2002]

 

What you're saying is correct, but I'm not sure who you're preaching to.

I was just trying to clear up this pointless debate people were having over different interpretations of the same concept.

 

I am not preaching to anyone. Just clarifying my point in regards to what you said.
SoupNazi and Solracer seemed to be arguying that there was no torque increase at the wheel following the use of a higher ratio FD and I was explaining that yes there was. BTW I don't see this as a pointless debate.

 

I believe JPP is on to something. Accelerational G-forces are much higher in 1st gear than they are in 2nd. And they are higher in 2nd than they are in 3rd, etc. Accelerational G's are directly affected by torque.

 

This concept is not new and is nothing that has just been discovered by JPP.

Does a shorter (numerically higher) FD give you more torque?

Yes and no.

It does not affect engine output at all, but it does make more efficient use of the current output.

This results in quicker acceleration and a decreased top speed. In the same way a taller FD results in slower acceleration and an increased top speed.

Traction limited vehicles may actually prove to be quicker with a taller FD, due to less torque being effectively put to use. In most cases a shorter FD will result in quicker acceleration, as long as it does not increase traction problems.

 

I could argue with the way you are phrasing this, but I do not wish to jeopardize the newer friendlier version of you.
Let just say that a shorter FD gives better acceleration and leave it at that.

And no I did not invent any of this. Physics is physics.

 

If I drank, I'd drink to that.