Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - '89-91' Federal HF Transmission swap into a Federal '94 Honda Civic VX

steffen707 · 04-20-2012, 05:39 PM

Glad I found this thread. There are no kits out there to put the cable transmission into your hydro transmission chassis; however, you can swap the final drive and probably some of the other gears if you want. If you visit an online honda gearing calculator like Honda Transmission Calculator by ZealAutowerks you will see that there isn't much of a difference in the 1-5 gear ratios. The magic of the HF is the final drive as somebody pointed out. Note that Honda Transmission Calculator by ZealAutowerks doesn't have the right final drive. Its actually 2.98 for the federal HF final drive.

Don't be fooled into thinking that lean burn will automatically happen at 80mph because you will be at 2500. The ecu takes into account your throttle position as well. You might find that you get better gas mileage in the city and lose mpg on the highway.......BUT THAT DOESN'T MAKE SENSE YOU SAY.

If you have a higher final drive, your rpm at highway speed will be less, the car will make less power. If the power the car is making in lean burn isn't enough to overcome the aerodynamic and rolling resistances you are seeing in the car, it will drop out of lean burn.

Much like putting a vx engine into a heavier less aerodynamic car, if the engine can't make enough power in lean burn your mph will decrease, you step on the gas pedal harder, and then BOOM, the car drops out of lean burn and you're only getting 35mpg at 65mph.

The only way to tell if this will benefit or not is to do a real world test, or to hear what somebody else has experienced.

I was wondering the same thing. But I was thinking this, with 165/65/14 re92 insight tires, and given the HF 4th gear .823 and 5th gear .694 and final 2.98, at 2387rpm in 4th gear you would be at 65mph.

Now in the VX gearing of .702 5th gear and final of 3.25 at 2220rpm you would be at 65mph.

So I was thinking of swapping in thed 4th, 5th and final of HF into a VX trans and then for 167 more rpm, you would be at the same speed in 4th as you would be in the vx in 5th.

So in case the HF final drive is just too much for the car, you can still get almost the same gas mileage as before with 167 more rpm and the new HF 4th gear and HF final drive, but in city and like everything below 50mph, would be much better off with the longer HF final drive and new HF 5th gear. I just don't know how much that 167rpm is going to hurt the fuel economy if you do have to be in 4th on the highway.

Thoughts?

04-20-2012, 05:39 PM	#5 (permalink)
steffen707 Master EcoModder Join Date: Oct 2009 Location: Midwest Posts: 337 Thanks: 4 Thanked 37 Times in 21 Posts	Glad I found this thread. There are no kits out there to put the cable transmission into your hydro transmission chassis; however, you can swap the final drive and probably some of the other gears if you want. If you visit an online honda gearing calculator like Honda Transmission Calculator by ZealAutowerks you will see that there isn't much of a difference in the 1-5 gear ratios. The magic of the HF is the final drive as somebody pointed out. Note that Honda Transmission Calculator by ZealAutowerks doesn't have the right final drive. Its actually 2.98 for the federal HF final drive. Don't be fooled into thinking that lean burn will automatically happen at 80mph because you will be at 2500. The ecu takes into account your throttle position as well. You might find that you get better gas mileage in the city and lose mpg on the highway.......BUT THAT DOESN'T MAKE SENSE YOU SAY. If you have a higher final drive, your rpm at highway speed will be less, the car will make less power. If the power the car is making in lean burn isn't enough to overcome the aerodynamic and rolling resistances you are seeing in the car, it will drop out of lean burn. Much like putting a vx engine into a heavier less aerodynamic car, if the engine can't make enough power in lean burn your mph will decrease, you step on the gas pedal harder, and then BOOM, the car drops out of lean burn and you're only getting 35mpg at 65mph. The only way to tell if this will benefit or not is to do a real world test, or to hear what somebody else has experienced. I was wondering the same thing. But I was thinking this, with 165/65/14 re92 insight tires, and given the HF 4th gear .823 and 5th gear .694 and final 2.98, at 2387rpm in 4th gear you would be at 65mph. Now in the VX gearing of .702 5th gear and final of 3.25 at 2220rpm you would be at 65mph. So I was thinking of swapping in thed 4th, 5th and final of HF into a VX trans and then for 167 more rpm, you would be at the same speed in 4th as you would be in the vx in 5th. So in case the HF final drive is just too much for the car, you can still get almost the same gas mileage as before with 167 more rpm and the new HF 4th gear and HF final drive, but in city and like everything below 50mph, would be much better off with the longer HF final drive and new HF 5th gear. I just don't know how much that 167rpm is going to hurt the fuel economy if you do have to be in 4th on the highway. Thoughts? Last edited by steffen707; 04-20-2012 at 05:48 PM..