I have a 90 hatch with a DOHC ZC on PM7 with a SL3 tranny. Only mods are a intake and lightweight flywheel. I get decent gas mileage but I wanted to put a number on it. So last week I filled my tank and drove 120 miles, 100 were on the interstate and I was at half a tank. Well with the four speed tranny at 75 MPH I'm sitting at 4k RPMs. So this week I filled my tank and just stayed on back roads or regular roads and got 200 at half a tank and 310 by the time I got to the red "E" line. Filled the car up this evening and still had basically a gallon and a half left so I could've gotten around 340 - 350ish. My question is, is 30 -31 MPG's decent for a DOHC ZC?

I understand there's more to it for MPG's but I'm asking as in general. My other thing is, I'd like to have a better cruising gear on the interstate. As much as I'd like to get a ZC tranny or SI they're hard to find around here and people want a lot for the ones I have found. But I do have a EG S20 or SJ20 five speed tranny and wanted to ask if it was possible to just take that fifth gear out and put it in my four speed? Or is there more to it than that....

 

I meant to put in there, I kind of expected almost 40 mpg......and if I were to take the car to the last drop I would get about 34 -35 but I don't like to take my chances with being stranded so I aways try to fill up by the time I reach the red "E" line. I guess I was just trying to reach out to those with dual cam ZC's and see what they were averaging.

 

I get 28-30 on a sohc zc
A lightweight flywheel is suppose to be bad for gas mileage I think

 

That's interesting man.....I would expect for you to get a tiny bit more than I would just because you're a single cam...I know there's a slight difference in our heads but not much. Given I am a 4 speed and if I'm not mistaken you have a five speed in yours?

 

yep 5 speed si tranny
3000 rpm at 65 mph
just found out my o2 sensor might have been bad so I' will update soon
I have a 9.8 lb flywheel
to increase mpg
lose weight
exhaust
ground cables
aerodynamics
drive like grandma
tire pressures
synthetic oil

 

See that's what I did this past week, I drove like "grandma" as you said. I wanted to see how much I could squeeze out. See in fourth gear for me at 65 MPH I'm sitting at about 3400 - 3500 RPMs. In fourth going 55 is right at 3k....between 2900 and 3k.

 

I wish I had one more gear or something
but these cars were made when the speed limit was 55

 

If I really want to get stingy I shift 1-3 3-5

 

Hahahaha! that kindda sounds like what I can do with my little four speed. I shift into fourth at about 40 -45. I could take first to almost redline and shift into fourth and forget the other two.

 

Hey "acmoc" read this http://www.8thcivic.com/forums/clutc...-less-mpg.html It kindda gets into two people battling each other to see which one is smarter or something. But they really put it all out there as far as lightweight flywheels. I know you had problems recently and was skeptical about them. Just thought you'd like to read this, maybe not...

 

if I were you id source a dx trans (cable) I have one in my car with a y7 its perfect for mpgs I'm getting about35- 40 average city/highway and I drive pretty bad to pass people

 

Any 5 speed tranny would be better sittin at 4k rpm is awful for mpg's. My b16 tranny in fifth going 70 is around 4k rpm so I know your pain lol. When I had my crx si I would get about 40 mpg's if I drove good and usually around 30 if I didn't lol.

 

"KingVem", I assume you're saying the DX tranny is 5 speed. Since you have one I wanna ask you if it's a good tranny for "getting down" or whatever you wanna call it. My 4 speed is awsome gunning it in first but after that it'll bog down in second because the gears are so big. Like i said in my first post I'd like to get a ZC or SI tranny but they're hard to find for a decent price and not being messed up.

 

when I had my Z6 with SI trans and a chipped ECU in mine, i got 41mpg all interstate at 80mph. Car only weighed 2200lbs with me and a tool box in it though. weight is key. that 4 speed is killing it too though. get a 5sp DX trans and that will help a lot.

 

Yeah I get on the civic all the time from what I understand dx/si have the same 1-4 and different 5th I can take the y7 up to 110 easy and I used to have the four speed in my civic....you will love it once u upgrade

 

Really? Interesting......I didn't know that about the DX and SI being basically the same except for fifth. That's awesome man, thanks for the info.....Can you tell me what code is stamped on your DX tranny? So I know what to look for in a junkyard if I get on from there? I know you can't go soley on the code on it but it'll help me to narrow it down.

 

too be I don't honest remember if you go to the junkyard id just make sure its a five speed its win win either way dx/si and make sure its a cable tranny and you'll be set

 

1st-5th in the SI and DX are the exact same, the final drive in the SI is higher which in turn makes all the gears shorter.

 

Cool, sounds good...thanks for the information.