manual trans question for my build info

[Drakon543]

so i posted this question on another forum a couple days ago and figured id post it here too. as my project thread eventually im doing a manual swap but atm its not high on my list. my route to work has me sitting at 3k rpm for quite a leg of my trip so besides my mods and no tune to allow the ecu to properly adjust im only doing about 30mpg. btw I'm only assuming 3k plus mods and no tune is probably my cause of lower mpg. so 5spd civic 70-80 mph can a couple people post me thier general rpm ranges. im aware 30mpg really isnt that bad and its far from seriously bothering me but if a 5spd swap can drop my rpms enough ontop of being able to choose gears gets me alot better mpg. im also aware you dont modify vehicles and still be concerned with mpg lol. it will however give me a 1 up when i find a donar car for the swap and ask the boss if i can buy it

 

[Drakon543]

currently dime a dozen where im at in the poconos. peeked yesterday and ive got 4 available under 900 bucks in various condition. but ya a manual swap is eventually happening regardless of any benefits. also teaching someone else to drive stick on my vehicle isnt happening period. ive got 3 vehicles so having the civic down for an extended time frame isnt even a concern. but currently i still have a laundry list of other mods, general upgrades, and basic stuff i want fixed. im at that what to do next phase and i would like the manual swap to be at the top but i cant justify it if the automatic is working perfectly. ontop of that if looking and sounding cooler with a manual is the only benefit i still cant justify it. so im currently at the " if i could get better mpg and i wouldn't have to keep the rpms so high" thing. the d16 is a solid motor if kept up on like it should be but hovering around 3000 rpms for 30-40 min with occasional 4-5k spikes for hills and passing probably isnt helping the motor.

 

[SeanShine]

@Drakon543 if I understand you correctly, you are asking what is the normal engine rpm for a manual transmission civic in 5th gear at 70mph?

This actually depends dramatically on the transmission you're using. I believe (though I may be wrong) that the EX has a different gearing than an LX or DX. I would give you my normal rpms, but mine is an automatic. That being said, I did a google search and it seems that most of the time a civic will run between 3000 and 4000 at 70 mph. Cars like the 1995 Civic SI have shorter gears, and sit between 3500-4000. Then cars like a 1996 Civic LX has longer gears and it sits between 3000-3500.

Will a manual transmission get better fuel economy than an automatic? Yes. It will probably get a few more mpg than an automatic. But the reality is that a person's driving habits has the most effect when it comes to fuel economy.

 

[Drakon543]

i honestly tried that search a few times and didnt come up with any specific information. the only thing that kept coming up was what gear to dyno in....
well thats the general information i was looking for and it definitely doesn't push me to get my manual swap done before anything else on my list. essentially if i switch to manual i will actually have to run the car even harder to keep up with interstate traffic. 4th in the automatic at 70 is 3k manual in 5th ill either be at the same spot or even higher. normally i would definitely say you would easily get better mpg out of a manual. especially maybe back in 2000 when these same roads i am on 65 was already over the speed limit. i do 98 miles every day i live right off east to west interstate which takes me directly to north to south interstate. 49 miles each way and probably about 45 miles is 4th gear 70 cruise control. ill just wait for the swap until im actually doing real power gains. thanks for the information.

 

[Drakon543]

so i got a link for a breakdown of the manual transmissions. lowest final drive for 6th is 3.75 the cx 5th gen had a 3.25 option. might be a little doggish in 5th but i think an s20 from a cx might be what i want when i get around to this. this is a dd fun project tinkering type of deal so anything i do cant make the car worse on the highway. so any opinions on that transmission option are welcome.

 

[Drakon543]

gas mileage isn't really the biggest concern but its does have a hand in hand with how high id have to run my rpms. i mentioned it earlier on only due to lack of correlating information i now have. so my big hang up now is the s20 and s40 would have me at 4000 rpms on the highway. besides the 3.25 that came in the 92-95 cx i haven't located a source for the diff gear. anyway an na high compression build or a turbo build running at 4k for 40 min straight twice a day doesn't sound healthy for the engine. so im trying to get some more information to decide where im going to go from here on. if i cant get the stuff i need easily to make the car more friendly on the highway then a full engine swap may be more in the plan. but im only looking for 160-250 hp which can easily be done with the d16y8 so id like to just go with that.

 

[SeanShine]

@Drakon543 When it comes to transmission options for mpg, I think any of the 5 speeds will work fine (except for ones from the civic SI). Like 96-el-x said, remove any unnecessary weight, and then drive the car like a grandma.

One of my previous Civics was a 97 EX 5spd. I was able to get 36-38 mpg, but I was only able to do that when I was doing everything I could for better fuel economy. I removed the spare wheel, filled the tires up to 38 psi, and I would consistently throw the car into neutral and coast down hills and down off ramps.

Eventually I found that the extra 5mpg wasn't really worth the hassle for me. It was easier just to drive normally and pay the extra couple bucks when it came time to fill up.

 

[Drakon543]

ya im only getting 28 right now which is still better than my 97 tahoe but its about the same as my 13 v6 accord. my big thought here is if going to be stuck doing 3-4k i might definitely want to stick to a real na build. 4k trying to do highway speeds might start to build too much heat on the turbo. i want to do a build that suits my idea and everything compliments each other. i dont want to do part of the build and have to change a different part of the build or change the way i drive the car just because of build choices. id rather change my plans as a whole than try to fit the rest of the car with one part. if i need to scrap my original plans and do an engine swap for more suitable transmission choices then ill do that. probably going to the honda Toyota event at nj island dragway sunday ill get some direct input from some of those guys too and ill make further choices after this upcoming weekend. im not so stubborn that ill back myself into a corner on a build if everyone is telling me its stupid. but i do like to be different somewhat so i will take forever to make a choice on something.