Now this looks interesting.

I am eager to see the results of this.

 

i might be interested in a semi drag setup!!

 

Extremely interested. Anyway of doing a LSD with these gears? But one thing, how do you plan on correcting the speedo being off from this modification?

 

I can hunt around and post up results from B-series (ITRs, etc) and probably a few H22's, as they have had final drives out for a while.

Hondaman's LSDs are a straight replacement of the stock differential, if I recall correctly. Therefore you CAN indeed use the LSD and the FD kit at the same time. Here's a pic, the LSD replaces the red part, the FD set replaces the green:

http://www.kotetu.net/Legend/lsd-fd.jpg

You can't correct the speedometer, as far as I know. The speed is most likely calculated from RPM and wheel diameter using a formula built into the ECU. Even changing your wheels is going to throw off the speedometer. With a final drive that is higher than your stock, you will not be going as fast as your speedometer thinks you are going.

 

maybe the guys that are working on the ecu can set something in the ecu to adjust the speedo, not sure

 

I can hunt around and post up results from B-series (ITRs, etc) and probably a few H22's, as they have had final drives out for a while.

Hondaman's LSDs are a straight replacement of the stock differential, if I recall correctly. Therefore you CAN indeed use the LSD and the FD kit at the same time. Here's a pic, the LSD replaces the red part, the FD set replaces the green:

http://www.kotetu.net/Legend/lsd-fd.jpg

You can't correct the speedometer, as far as I know. The speed is most likely calculated from RPM and wheel diameter using a formula built into the ECU. Even changing your wheels is going to throw off the speedometer. With a final drive that is higher than your stock, you will not be going as fast as your speedometer thinks you are going.

Actually our speedos are driven by the speed sensor on the differential.

 

here's a very informative thread I found on Honda-tech regarding gearing and final drives:

http://honda-tech.com/zerothread?id=1593351

it's got quite a bit of detail and explains why shorter gearing is good.

Actually our speedos are driven by the speed sensor on the differential.

Speed sensor sends the rpm data to the ECU or another computing device that knows the wheel diameter. Using the wheel diameter, rpm, and the constants pi + gear ratios, the ecu or other computing device reports the speed.

If the data is in the ECU, and is accessable, we could potentially change it. I don't really think it's important to do so, though. Just drive the speed of traffic and you'll be fine.

 

1) Shouldn't this be in the performance section?

2) In addition to throwing off the speedometer, I am curious to find out if you folks think this will throw off the ABS computer as well. I don't think so but confirmation couldn't hurt. After all, the ABS computers should be measuring actual differences in wheel speed from the wheel sensors vs. calculating speed from the engine RPM, right? I could see how the ABS computer could freak out though if the front tires start rotating at a different speed than it expects and measures from the rear tires.

3) Unless I'm misunderstanding this thread, the aftermarket final drive (AFD)'s effect on your speedometer speed is linear, right? If so, wouldn't something like this help? It essentially adjusts the scales the VSS's signal to where it needs to be to keep the speedometer correct.
http://www.blackrobotics.com/yb_home.htm

4) Would there be any advantages in gas efficiency by installing a lower (taller?) final drive ratio? While your acceleration would suffer (don't care) and final top speed would increase (also a don't care), your engine would be at a lower RPM for a given speed, right? I'm sure it doesn't make economic sense but I'm curious.

Regards,
-g

 

I moved the thread...

and also, wouldent making the car accell faster in the start really hurt the top speed? I dont want my car to only go 100mph or whatever. in the end you are gonna have to make the finial gear ratio the same

 

S4gunn
1) yep, thanks cole
2) I'm not certain how the ABS computers work! good idea! Let's look into it independently and see what we come up with.
3) FANTASTIC! that is definitely going to help. If you put this inline, you can very well adjust the speedo to make it right. Then I suppose you just need a cop friend who will help you with his radar gun..
4) Yes, you would lower your cruising RPM further by adding a smaller final drive (which would be a lower numeric value, such as a 4.0). I suppose doing that makes just about as much sense as putting in a larger one. It's just what you are looking for in the car. Of course, you'd also have to get that custom made, since there's probably very little chance of a significantly sized group being interested in it. I'm betting more people will want the increase in acceleration.

Cole
Raising the ratio of the final drive WILL lower the topspeed. Let me give you an example below.

 

Changing the final drive won't affect our speedometers or ABS fortunately. On RWD cars, the speed sensor is generally mounted in the transmission, so it cannot recognize/measure any changes made after the transmission (rear end gearing changes). Our speed sensor is driven off a gear pressed onto the diff itself, so any changes in gearing that change the rpm of the diff will be measured by the speed sensor. Same situation as the Integra guys, they don't have to make any corrections to the speedo when swapping out FD's.

For those of us with 6 spds, theoretical top speed will still be higher than the car is capable of reaching due to aerodynamic drag, no worries there. Cruising rpm on the highway will be a bit higher, fuel mileage will drop a bit at higher speeds, shouldn't be too bad though. Traction off the line will suffer some due to the increased torque multiplication, other than that it would be beneficial. I might be interested in a GB on this, depending on how it all plays out.

 

I am interested in this. I was thinking about this at one point but didn't know who would do it and for how much.

Anyways, you're definately serious about this correct Kotetu? If so then I will be interested. I will probably try and cop a Hondaman LSD to put it in. And then it's on to a small shot of nitrous and some tuning on my SAFC.

 

Kenso, so would an LSD help out the traction problem that it we face with the better gearing?

 

Kenso, so would an LSD help out the traction problem that it we face with the better gearing?

I believe you already know the answer to that yourself sir! Think posi in a Nova (similar to an LSD) and is #1 mod for Novas to reduce wheel spin.

Edit: I would think more than anything it would help with torque steer but I'm not sure.

 

yeah actually i did know the answer to that question. its actually something i am looking into getting sometime in the future along with this...

 

yeah actually i did know the answer to that question. its actually something i am looking into getting sometime in the future along with this...

Yeah Ben just let me know about this. I am interested as well. I think this would be the easiest way to have a little more fun from light to light.

 

Yeah Ben just let me know about this. I am interested as well. I think this would be the easiest way to have a little more fun from light to light.

yup, and since we can still hit 150+ to wont hurt the actual top speed...

 

Put me down, enough discussion, let's get it poppin'.

 

Mikey, I'm totally serious. I'll talk to the shop again and see what they say regarding a group buy. Also, we would need to come up with the target ratio for production.

We can afford to take our time with discussing the best configuration, the pros, the cons, etc, and to generate interest. We want to do it right!

I have been looking for posts regarding the current fd ratios, and so far I have come up with a 5 different numbers for the different models/trim levels. I can't help but think that is mixed up. If anyone has solid data regarding any of the transmission gear ratios should post it here. I'd also be very happy to hear if anyone has actually taken out their differential and counted the teeth on the gears. That would give us an accurate measurement.

Finally, Dv8 posted long ago that the Auto Type 2 differential is made of aluminum, as opposed to every other differential case which are made of cast iron. Accurate or not? I'd like to get the weights of the different units as well, since I know that the bolts all line up well enough for them to be interchangeable.

 

All automatics use the aluminum diff. housing, the manuals use the cast iron one. I think Dv8 weighed both and posted the results somewhere around here.

 

I'd also be very happy to hear if anyone has actually taken out their differential and counted the teeth on the gears.

I have both an auto and a manual diff. So I'll try and count those teeth this week coming. I have to open the manual to install an LSD anyway.

 

what are these gonna be made of, just wondering?

 

If it works with automatics, I'm in 100%.

k.

 

If it works with automatics, I'm in 100%.

k.

It will work with our automatics!

 

Here's a quote from the manufacturer of the final drives: "Precision machined to exacting tolerances from high-tensile forged steel, heat treated and shot peened, you will not find a stronger, more reliable product on the market."

It will work with manual or automatic, no problem. I'm even considering getting the automatic differential or at least the differential case to save a bit of weight.

hotlava - while you are at it, weigh them both! Do you know which Type they are? (type 1, type 2) You need to count the teeth on each of the GREEN parts I highlighted in this picture:

http://www.kotetu.net/Legend/lsd-fd.jpg

Then divide the ring gear tooth count by the pinion gear tooth count. Thanks!