Your engine speed at 60 MPH?
 

Hi all, I am new to this forum and very interested in improving my MPG. I have an old 87 Civic DX with the "FE" carburated D15 SOHC engine (I am disapointed that I'll never be able to use a scanguage:( ). I am averaging around 38 mpg now (50/50 city highway) without any mods and am looking into doing a 5th gear swap or putting in an FE transmission (actually I am not even sure whether or not it has an FE trans in it now).

At 60 mph, in 5th gear, my motor is turning at 2600 rpms. Could some of you share your gearing info/mpg with me (engine rpm at 60 MPH and approximate mileage at that speed) so I could get an idea if changing out my trans would be worthwhile?

Thanks in advance for any replies. :)

Welcome to the forum, and I'll go for a drive in a little while to see what my RPM is at that speed.

Maybe 30-32mpg/2200rpm@60mph.

Approx 1800 RPM, but I am using a CRX HF transmission in my Civic.

HF gearing is:

1 3.250
2 1.650
3 1.033
4 0.823
5 0.694
R 3.153
FD 2.95 (non-California model)

HERE is a helpful site for calculating speeds per gear.

I have no idea what my FE is at that speed/gear. I plan on getting a MID someday so that I can see, but I'll need to convert to MPFI first.

Here is a similar post/question from RPR, complete w/ my $.02:


https://www.redpepperracing.com/forum...opic=28958&hl=


Mak

Hello -

On my 1.9 liter DOHC, on my ScanGauge, I am seeing ~38 MPG @ ~2600 RPM @ 60 MPH.

CarloSW2

my civic vx runs at about 1,700 rpm going 60mph with the stock vx tranny, even going 85mph, the engine is still only turning at about 2,400 rpm, it freaks me out every time I drive other cars and have the engine rev so high, the only time I see 3,000 rpm is when I'm trying not to get hit by a semi on the highway on ramp.
not sure what kind of mileage I'm getting at 60mph, because I don't have any real time feedback device, and do a weird mix of driving right now.
aside from the FE carb, I would recomend a better cam, if you are going to replace the tranny, otherwise your engine isn't going to be tuned to run at those slower speeds.

02 civic EX manual trany *Future* scangauge :D shows ~3200 at 60mph and depending on load (i live in a hilly area) gets 37-48 mpg

My diesel spins at about 1800 rpm at 60 mph.

'85 CRX Si: '85 Si tranny w/ HF 5th gear = ~2750RPM @ 60mph

It flutuates depending on the weather though...give or take 100RPM

I can't remember what the stock Si 5th gear did for it, I could calculate but I can't remember the tire size. Mak

01 Jeep Wrangler 4.0L ~1900 @60 mph

apples to oranges compared to most of your engines though.....

I will look when i go to school. Al I know is 1,600rpm=30mph in the saturn.

Thanks to all for the replies!

Based on the numbers from DaX it looks like I definitely don't have the FE trans.

It looks like some of you have much better gearing than I do, but I'm not sure if spending $300 or so for an HF tranny will be worth it in the long run...

[QUOTE=MakDiesel]'85 CRX Si: '85 Si tranny w/ HF 5th gear = ~2750RPM @ 60mph

Makdiesel, could you tell me- where did you get your HF 5th gear? Junkyard? That might be a better start for me, but I am curious as to why your engine (12valve d15 just like mine) turns faster than mine at 60mph when you even have the HF 5th gear .:confused: Did the HF 5th gear swap give you much mpg improvement?


DaX- did you see a big improvement when you switched your civic (much newer than mine) from auto trans to the FE trans?

Thats wrong 1,500rpm =35mph. 2,500rpm=60mph (I don't see that kind of speed to often :) )

Sure did. Check out my Gas Log HERE. The rise in FE about halfway through the graph is when I installed the HF transmission. It does, however, take FE conscious driving. If I try (and I have tried to test it), I can get worse gas mileage than before by driving the car hard.

Change transmissions? Gear ratios? What a pain! Bring money! Time! Patience!
I'm with "clencher" on this one...find some taller tires / wheels / both? Bolt-on beats R&R (remove & replace) any day!:thumbup:

I took a look while driving my car today. It's at 2335rpm at an indicated 60mph. I have a taller 5th gear in my tranny. The stock 5th gear spun the motor about 500 rpm higher.

Thanks again
 

Thanks again to all for the info. I might keep my eye out for a cheap FE trans or an FE 5th gear set for my trans. I don't mind the labor of swapping the transmissions out. I've done at least 4 Honda D series clutch jobs.

Someone mentioned that upping the tire size would be an easier mod to change the gearing slightly.

On my previous car (87 Acura Integra D16 MPFI), I tried increasing the tire sizes in an attempt to change the ratio slightly to get better FE. In that car, at 60 mph (5th gear), the engine was turning at 3000 rpm :eek: . I went from the stock 195/60 14 up to a taller 175/75 14 (the 175/75 14's would rub the fenderwells when I turned sharply). I did all the speedometer correction calculations and ran them for several years, and then went back to the stock size when those tires wore out. It ended up that I got slightly worse mileage with the taller tires than with the shorter tires :confused: (more ground clearance/air under the car?). Again, I did all of the corrections for odometer inaccuracies. I was really surprised that the shorter tires were better for my FE. It would get 32-34 mpg on the highway (60 mph). I always wondered how much better it could have done with better gearing (2 months ago someone hit me and totalled it) :( . It was still running strong at 254,000 miles (it had 148,000 when I bought it).

Erik: On my 89 civic wagon, which is fundamentaly a DX, box, I am turning about 3000 at 60mph.
On the transmission, I have a HF transmission I was able to pick up for free. However, it has a piece of the case missing, so I am going to need to pull my transmission and rebuild it, using the HF gearing. Their are several points worthy of note.
First, as has been noted, the people who have made a change to a taller transmission have all had pretty significant positive results. Consequently, if you can get a transmission for a low enough price, it would probably be a worthwhile change to make.

Second, if you look at the gearing on an HF transmission, most of the drop in engine rpm actually comes from the taller gearing of the differential gears, not the 5th gear. The 5th gear contributes, but it's probably a 30/70 percent ratio, or so in my evaluations.

Third, if your getting 38mpg, with the engine, carb and transmission you have, you are doing pretty well. I also have a 87 DX, and I typically get 35-37mpg from it. Personally I'd like to get rid of it, but I have to get another car running for my daughter to drive, before I can do so. My primary reason is that the carburator set up is very complicated, a real pain to work on and the cost for a replacement carburator, rebuilt, is worth more than the car is worth, if I sold it. However, it has been a phenomenal car. It had 155,000 on it when I purchased it and it is at around 230,000, now.

Last: I believe that on the 87 you can actually replace/exchange the 5th gear with the car in the transmission. Their is a CRX web site called Redpepper which has loads of information for the 87's and it is almost all relevant to the DX, as well. I wouldn't advertise that your driving a DX, though, since it's largely dedicated to making CRX's go fast.

If you decide to make the change, be sure to post your conclusions, after you get some idea of how well it worked out.

2100 at 60mph
2480 at 70mph

1.) I got the HF gear from a fellow RPR member for I believe $30 (good condition).
2.) My engine turns faster because I have the stock Si transmission from gears 1-4, then add the HF 5th, while I believe you have a stock DX tranny. The only true difference between the Si and DX transmissions for a 1st gen CRX is the final drive ratio, determined by the differential. DX's have a taller FD ratio, knocking each gear down several hundred RPM's, despite the fact tha actual individual gear ratios are the same as the Si. The HF tranny has both a taller FD ratio AND individual gears to give it the long legs it has.
3.) The swap actually wasn't as drastic as I had hoped (I didn't do the math beforehand) and so I later picked up a complete HF tranny to one day swap in to cure this high RPM song bird since I drive 80% highway anyway. BTW, if you go w/ the HF 5th gear, only the fifth gear housing has to come off, not the entire tranny. Just jack up the right side and loosen the 5-6 ten-mm cover bolts to access the 5th gear. Also, keep your assembly in the right order! A HELMS manual also helps, which is also provided on RedPepperRacing.com -- Visit there, ask questions, look around, you'll find plenty of answers. Mak

Additional rolling resistance and/or unsprung weight could have something to do with it...how do you recalibrate a Honda/Acura speedo BTW? Mak

I have an '89 CRX HF (yes, the late body) with the shorter geared HF tranny (yes, there were two types for the HF). In 5th gear mine turns @ 2450RPM. If you get your hands on the taller geared HF that number in 5th gear is more like 2150RPM or so. Yeah, nice!

I didn't change anything mechanically, I just used the mile mile markers on the interstate and compared them to my trip odometer to see how far it was off. I typically see how many mile markers I have to pass before my trip will be 1 mile off. So if it takes exactly 25 mile markers for my trip odometer to be 1 mile behind, I know that my speedometer/odometer is reading 4% too slow and thus my mileage is really 4% greater than was measured with the trip (because I covered 4% more miles than is shown).

Thanks for the info on the 5th gear swap. My current trans already has a little bit of a whine in 1st gear and third gears so I am leaning towards swapping in an HF tranny if I can find one cheap enough.

Wow, everyone seems to have much lower rpms than my car. The 1.0L in my Geo turns at precisely 3000 rpm at 60mph (and naturally 1500 rpm at 30mph).

Metrompg, what's your rpm at 60mph since getting the higher final drive in your blackfly?

That POS Suzuki Sidekick I use also turns at 3,000 rpm at 60 mph. While the EPA rates it at 26 mpg highway, it really gets like 16-18 mpg at that speed.

EPA numbers / methodology?
 

Hmmm... The EPA doesn't live on this planet! I saw on TV (yes, there is still some good info on this box!) last night ... the air quality in the San Jacquine
(sp?) Valley ... in California ... was just awful! Yet, the EPA has been telling us (for years!) our air quality has been improving! Geo. Orwell called this "newspeak"....

The Prius turns 1500ish at 60MPH. Since it is a CVT, that number varies with load.