finishing up my z6 turbo build
should be right around 400 whp, want some longer gearing to make better traction
want to swap out final drives on my s40, wondering if a final drive outta an L3 is possible? is it a straight swap?

 

if you want better traction dont hold the gas pedal to the floor

 

longer gearing = better driveability for daily and better gas mileage

 

I got better gas mileage after swapping my ls tranny to a gsr tranny by about 3 mpg consistently.

 

fixed

 

sorry failed to mention i drive almost 400 miles a week on the highway commuting
the long gears may help abit more for my application

 

i think it had been proven befor that there is no gas suffering with a change of a final drive to shorten your gears ... like a shorter gear would have less load on the motor requiring less gas to move that car .. like a ls tranny is burning the same amount of gas as a gsr tranny when the ls is at 4200 rpms and the gsr is around 4800-4900 rpms at the same mph because the gsr trans needs less force becasue of the better TQ multipication

 

The L3 FD set will not fit in your S40 because the L3 has a shorter countershaft and different gear spacing. You can use any of the sets from the S20 or S40. The S40 came with a 3.72 ratio in the DX hatch back and HX, 4.06 in the DX/LX, and 4.25 in the EX. The 92-95 S20 also used the 4.06 and 4.25. The 3.25 FD was used in the hi fuel efficient S20 VX but it was so slow it couldn't get out of it's own way.

 

Why do people have this horrible misconception that they'll get better gas mileage with 'taller' gearing?!

It's a 1.6 liter 4cylinder. It's not a chevy 350. You're not going to get better gas mileage with a 4.05 or 3.722 final.


And if you do it's going to be negligible. Negligible in the sense that nothing that you measure gas mileage with will be accurate enough to notice the difference. That's why they have significant digits.

 

Combined with the stock tire size, the OE gearing usually offers optimal mpg but with a tire size increase or different Final drive ratio, you alter the overall gearing. There are lots of variables in how gearing changes effect mpg, including the engine's torque curve, aerodynamics and weight.

A taller FD ratio lowers engine rpm at all speeds. With no other changes, and not taken to extremes, that may help mpg on flat ground freeway cruising. It will very likely hurt in-town mileage to some degree because the engine has to work harder to accelerate because you are continually slowing down and speeding up. Around town, shorter gearing actually helps by allowing you to accelerate using less throttle.

Each engine has a "sweet spot" cruising rpm range where mileage will be best. Generally speaking, that comes in the lower third of the engine's torque plateau but the engine has to have enough torque at that speed to handle the load. Trying to maintain speed while lugging the engine with a wide open throttle costs as much or more fuel than letting the engine rev.

The CRX HF and Civic VX were designed to acheive very high MPG. The have a very light weight balanced with a 3.25 Final drive ratio. I think the MPG difference between the 3.72, 4.06 and 4.25 will be very slight so use what performs the best for your set up.

 

now going with a taller gear, would that not help an engine last a little longer? milkage on an engine is all the same, would u want to buy a gsr with 120k miles most of which were at full throttle and 8500rpms? or do you want that same gsr with the ls trans that was used for commuting and most of its life it only sat around 3700rpms? I like tight 1-4 then a nice drop in 5th just so i can cruise it on the freeway. I have yet to shift into 5th on the strip.

just my two cents

 

you comparison makes no sense .... now if you asked me if i would buy a gsr that has been babied for 120k with a gsr trans or a gsr thats been babied for 120k with a ls trans i would say the one with the gsr trans .... becuase thee is no differnce and the gsr trans has better accel

 

im sorry u dont understand.... lemme spell it out S L O W L Y fer ya, higher rpms i.e. gsr trans- more rpms... more rpms = less life of an engine. cranks only have x amount of turns in them, rods only have so many cycles in their life expantancy. so with the same mileage, but one has more rpms its whole life... it in theroy... has a much shorter life expectancy.

get it????

 

o dont worry imm picking up what your throwing down ... but the ls trans also puts more load on the motor so each one of those rotations require more force/stress.. so the little bit of wear and tear = out to the same.. not to mention what we are talking about here is such a small differnce that if i handed you two cranks, bearings, rods from two differnt motors and told you one had a ls trans and one had a gsr trans you wouldnt be able to tell me witch had witch in it...

do you get it ????????

i have a ? for you ... put your car in 5th gear drive up a hill at 25 miles a hour .. then put your car in 2nd gear and drive up a hill at 25 miles a hour ... what one is doin more work and harm to the motor ?????

 

I'm afraid that it's you that doesn't get it.

Not only does your poorly written reply that's overabundant with grammatical errors make it painful to read. Or the fact that you use two extreme cases as an argument for our debate on long term effects that are so negligible that it would be difficult to even measure with common measurement tools.

If I go out and use a gallon milk jug to measure a gallon of water. I don't say that I have 1.0000 gallons of water. Because that implies that I am certain to the ten thousandth decimal place that it is exactly 1.0000 gallons. I say that it is 1 gallon because my measuring device isn't very accurate.

If someone were to go in with a syringe and withdraw 0.000001 gallons from the gallon of water that i measured using an old milk jug it would be called a negligible effect. Meaning that it's so minuscule that I cannot even detect the effects with my measuring device.

The long term effects of cruising at ~75mph with an LS final drive of 4.266 vs a GSR/B16 final drive of 4.400 is so negligible that you wouldn't even be able to prove that there is an effect. So much that you would spend more on an extensive lab test than you would save from using the lower final drive.

There's a certain finite amount of power required to maintain a car at a certain velocity. Which is a function of the vehicles mass, rolling resistance (mechanical frictions and wind resistance). I'm neglecting potential energy here and assuming that it's on a constant flat road with zero change in elevation. Even if you were to model all of this with an irreversible otto cycle and (http://en.wikipedia.org/wiki/Otto_cycle) You'd factor in the amount of...

Oh fuck it. It doesn't even matter. You're not going to notice a difference. When the engineers at honda are designing the fuel/ignition maps for the ECU they take all of this into consideration. For the VX/HX models they specifically design those engines for maximum efficicency. They match the engines mechanical characteristics with the transmission gearing and the ECU maps. On those particular models you will see a difference if you switch out the stock gearing for a shorter final drive. That is because the gearing now pulls you out of that lean-burn RPM window when you're cruising. So you can't accurately use the civic VX and HX with their corresponding 3.25 and 3.722 final drives as a rosetta stone in your argument. As we're not talking about either of those VTEC-E engines.

What you can do however is look at one of the 8th generation hybrids. Which has a form of VTEC-E, a lean-burn enabled ECU, and a CVT. Put the thing in cruise control and observe as the ECU gathers input from all those sensors to dynamically calculate the absolute most effective gear ratio. Guess what, it doesn't set the CVT at the 'tallest' possible gearing.

 

There's a certain finite amount of power required to maintain a car at a certain velocity. Which is a function of the vehicles mass, rolling resistance (mechanical frictions and wind resistance). I'm neglecting potential energy here and assuming that it's on a constant flat road with zero change in elevation. Even if you were to model all of this with an irreversible otto cycle and (http://en.wikipedia.org/wiki/Otto_cycle) You'd factor in the amount of...


LMAO Nicolaus Otto "Suck, Squeeze, Bang, Blow"

 

bense thank you for putting that all in a logical way that i couldnt put it even if i had a book infront of me

 

I know this is an old thread but you are incorrect kind sir! A taller final drive WILL result in better fuel economy assuming the driver doesn't compensate for this taller final drive by revving higher between each gear shift! At the very least, cruising on the freeway with a taller final drive will most certainly improve fuel economy assuming steady state driving at the same speeds as prior to the swap. If you consider going from 32mpg to 38-43mpg a "small improvement" (Vanilla 92-95 Civic D15B7 vs 92-95 Civic VX or 92-95 Civic CX) then yes, the transmission will result in a "small" improvement in fuel economy.

 

change your name to douchebag and call it a day

 

great write up bense my favorite part was this "Oh **** it. It doesn't even matter. You're not going to notice a difference" made my day!

 

Its kind of a trade off really, I ran a D15B vtec with a Dx trans is '94 sedan for a while. Used to average around 48 - 51 IMP MPG (should be around 40 MPG using US gallons) now that i'm running an Si transmission i've definately lost overall, i haven't actually figured out just what i'm getting for mileage now, but its about 75 kms less per tank. My in town mileage is probably a lot better though since I can drive around town in 5th (overdrive) most of the time. The only thing is I do mostly highway driving. Bense does make some very good points though.

 

Go do a lab experiment and prove the validity of your hypothesis. Then come back with the results, kind sir.

 

Why should I do a lab experiment when the EPA has already done it for me?

 

links? ....

 

Links to what? Go to fueleconomy.gov and pull the numbers yourself..