Regearing my Honda (1994 Del Sol VTEC)

[Shortie771]

Ok i did some research and found that the Del Sol Si has a hydro tranny and then stumbled apon the Honda Civic CX whixh is also hydro and they both even have the same tranny code (S20) but the gear ratio is much better for the CX... Do you think this is a good option for a tranny swap? Will it work?

Del Sol Si
1st 3.250
2nd 1.900
3rd 1.250
4th 0.909
5th 0.750
Final Drive 4.250

Civic CX
1st 3.250
2nd 1.761
3rd 1.066
4th 0.853
5th 0.702
Final Drive 3.250

[some_other_dave]

Sure, it should work fine. Any hydro D-series trans should work just fine.

BTW, have you actually looked at your engine to verify what you have? There should be an ID number on a flat boss on the front side right by the clutch housing. You may have to clean some grime off, but it should say "D16Z6" or "B16A" or whatever. It sounds like there's some doubt, and that will remove it.

-soD

[theunchosen]

Yeah he checked it earlier(somewhere in this maze of a thread) and its the 94 Si model not the vtec(so its the d16z, to clarify that we are both talking about the same thing(that I am not a total idiot ^_^)).

CX? Never seen one but the gears are the same size as the VX so I'd say they are the same.

[evolutionmovement]

Wow, that would be an enormous drop in rpm! Might be too much in top for that engine. Then again, there's always 4th.

[theunchosen]

No way, the other gears are staggered. Besides. . . at current you usually shift into 5th already doing 2300+ if you are accelerating hard. . .

The engine's got plenty of go so long as you aren't trying to pull a hill at the bottom of the 5th you should be fine. . .

[Shortie771]

actually im usually around 3000+ rpm going to 5th, its pretty bad

[theunchosen]

In that case. . .you need to start shifting alot sooner all teh time. If you are trying for FE, you need to shift as soon as you can be in the next gear and not lug/lerch the engine.

On your car(you have slightly more power and only 100 more lbs) you should be able to shift upwards on flat terrain at no later than 2200 RPM all the time. If you are hilling you can do 2600RPM and safely get into any gear. Trust me I have the Sam's gap pass on I-26 and it goes from 45-65 and I do it in 5th at ~2K rpm

[evolutionmovement]

The bottom gears should be fine, but 5th would feel drastically different. Should be nice for fuel efficiency, but you won't have much punch in 5th doing 2200 rpm at 65, for example (if I had a dyno chart, I could tell you what the differences in acceleration in g's would be). Shouldn't be dangerously slow, but the difference will be very noticeable. I'm only mentioning it so he has that in mind to decide. Personally, I'd do it as I hate unnecessarily short gearing and would always prefer top gear be a tall overdrive instead of matched to the lower gears. Should be much quieter, too, letting you hear all the creaks from the chassis even better.

[Shortie771]

Sounds good and next time i go out ill try shifting at lower rpms, i ussually shift between 3-3.5k rpm. so i guess thats bad? yeah quieter seems nice (i wis i could reduce road nose as well) and i hate having to shift so soon the taller gears of a CX/VX would definitly be better. I cant wait till i fix the few little bugs in my car, thats my first priority then when i have the money ill definitly be doing a transmition swap...

[theunchosen]

Yeah lower rpms means the engine is running each of the steps less often. At a set throttle opening the engine injects x fuel. If its rotating faster its injecting a tiny fraction less fuel per cycle(its getting slight less air per intake, but rotating much faster) but the number of cycles far outweighs the decrease in airflow.

In short if you can stay at low rpm its always better unless you are running it WOT to maintain that. So as long as you can barely depress the gas and still maintain low rpm thats the goal.

A vacuum gauge helps you measure because more vacuum you can get the less fuel you use.