I have an 89 crx si with a d16a6. Since i have to commute much farther than before (100 miles per day) 26 mpg just isn't good enough. Im wondering what my options are, what i had in mind was an hx tranny and head, but im having trouble finding either of them.
Would the head make a huge difference? Will it even work on my Si bottom end? The only other option is buying a 96 hyandai accent (40 mpg and beyond) but i hate how they handle(like your going to roll over) and its even more uncomfortable than my Honda. The body of the Honda is pretty much rust free and i already have so many parts for the car.

 

I'm also very capable of removing the engine and swapping in another, so if it would be a better option I'm open for that, everybody sells the fast engines for this car, but nobody I've found seems to sell the economy ones online.

 

An HF 5th gear set would change your RPMs to that of a DX (real close according to the transmission calculator), without affecting your performance in the 1-4 gear range. Also 26 MPG seems kind of low, list any modifications you have done. There are also several threads in the archives of people who are doing MPG projects, so you can search for those to get different ideas.

 

Mods: -AEM CAI
-Glasspack
-pacesetter catback exhaust
i also put a rebuilt head on it and changed the piston rings

 

how hard is it to change a gear in a transmission tho? I don't know anybody who has broken open a transmission, im willing to do it if there isnt risk of screwing up my trans.

 

how are you getting such shitty gas milleage? I have an 89 si commute 104 miles each day (highway) i get anywhere from 37.5 to 45mpg + no problem crusing at 80 to and 75 from.

 

i have no idea i can get 28 if i never go past half throttle and go 55 everywhere... the car runs really well too it pulls harder than any other 4 cylinder car Ive ever driven. I thought maybe the cat was the cause but it must be more than that if you get 10 mpg more than i do with the same car.

 

since its the old style ECU i cant just plug it in to see if anythings wrong unless its throwing a check engine light right?
i found an hx motor on ebay but they want 900 jsut for the motor and its a 1.7 liter(didnt know they existed).....

 

What would be good things to inspect to see why its so terrible on gas besides tune up items?

 

thats really strange. When is the last time you tuned it up ie new rotor/cap, plugs, wires? But either way half throttle should get you up into the 80's in 5th or at least 75.

 

ok well i meant i have to be a grandma accelerating in 5th i basically tip toe on the gas to hold 55, i tuned it up very recently and its actually doing its best on gas because it used to get 24 with bad injectors and seals. One noticeable thing is once its warmed up its has some hesitation somewhere between 2500 and 4000, wen its cold it revs significantly cleaner.

 

I have an 88 crx si. 323k on the clock.

modifications:

cold air intake, pacesetter exhaust and a set of E3 plugs.

I get just under 40mpg on the way to work.

I'm not running ac. broke years ago.

I only have one window down, have the sunroof bumped open but not fully open. I shift at 2500 to 3000 and do not go above that. I'm routinely getting 38+ a week.

Like stated might want to do a tune up.

possibly laying out of the gas pedal.

 

I have a SI transmission on my work bench that I changed the gear set in, but I have not finished changing the seals and bearings yet. This is the first transmission I have ever cracked open, not to hard as long as you follow the Helms manual. But I really won't know if I did it right until I install it with a motor I am also working on.

 

yea i got a sohc zc in my 90 si and im getting 32 minimum (when i go all city)

hows ur o2 and ur cat? maybe change them first?

btw someone has a hf ecu by me for sale pm me if you need it.

 

Well i dont think i need a hf ecu at the moment unless its cheap enough to buy and have on hand.
I guess ill try the O2 sensor since im pretty sure it has the original one on it from factory... The catalytic converter would be nice but id only buy it if i knew it would make a huge gas mileage difference because the car isn't loud enough to get me tickets.
would a O2 sensor cause the hesitation though? The car has had it since i bought it and since then it has had the head replaced so its not the head, and ive changed the injectors so its not them either. I wish i could afford to just change every damn thing.

 

With the head came a new distributor also so its not that either.

 

Another thing, i think it has an electrial short somewhere because it always seems to drain batteries when its left sitting for a few days, could this be causing poor gas mileage and hesitation possibly?

 

if you have a bad battery or a short, that will hurt your mileage as the alternator is working harder. you may also have a binding brake or alignment issue. my 89 easily got 40mpg, 47 at best.

 

wow
that is horrible mpg

you need a tune up. not a swap

my buddy has a stock 91si and tops 40mpg hwy
he gets hi 30's w/ ac on

my almost stock 91dx gets hi40's and occasionally tops 50mpg hwy
I am always over 40mpg even with city/hwy mix

 

well it even did the same gas mileage with a great alignment, but now the steering rack is definitely bad, im going to try taking out and cleaning a few things like the egr and the tps, and even that stupid carbon canister. Hopefully the haynes manual will tell me hwo to test them as well.
I don't think its plugs because its been through a few sets and never has done any better or worse on gas, but ill try a set anyways. No ideas why it would hesitate around 3000 rpms once its warmed up? When the engine is still cold it runs the best.

 

i have a 91 si completely stock besides muffler and filter. and i get over 40 mpg all day. i was on absolute E before, the car wouldn't even start, i put $5 of gas and got 98 miles out of her before i put gas in again. just so you know how unefficiant your car is running lol.

 

What wheels and what size tires are you running? Are they fairly new tires?

Definitely look at the egr valve and O2 sensor. Use fuel injector cleaner and consider seafoam to get all the carbon deposits out of the motor. Check your timing and test the alternator. Take out all unnecessary crap you may have in the interior and the trunk.

I can't think of anything else right now, but 26 mpg is definitely an indicator that there is something mechanically wrong with your rex. 26 mpg should be unpossible to achieve in our lil 1.6L 2000 lb cars!!

Let us know how it goes OP

 

Ditto on the wheel/tire question. Wheel size, or more specifically wheel/tire weight can make a huge difference.

Another question/thought - how many miles are on the chassis? You may have a bad bearing (or even a brake) that is dragging.

I also noticed that my car does better when I'm about 1/2 quart low on oil. Better enough to notice but not low enough to cause any damage.

 

As mentioned before, i'd check the bearings and make sure the suspension is in check. 26 mpg is really low for a d16a6, even with an Si transmission. I twist 4,000rpm on my trips to school with the a/c on, and pull about 35 mpg+ Make sure you tire pressure is good and all, and if your running some heavy rims i'd suggest going back to stock or a pair of light weight rims. Why'd the head need replacing? Make sure all the gaskets are good, intake manifold and exhaust, etc, if one of those are leaking you'll get crappy performance and low mpg.

 

i changed the head because the car was burning oil at idle and i had over heated it badly twice, and the lifters tapped. The rebuilt head was on ebay for 150$ with a bunch of other goodies so i figured it couldn't hurt.
i should check the back brakes probably, and maybe the front because i noticed one wheel locks before the other if i hit the brakes hard enough. what i really need is a parts dx or hf so i could steal the tranny for gas mileage and lots of other parts that the car could definitely use.
Im running the original alloys on it (185-60-14) but when i put my gsr rims on it (195-50-15) it only loses about 1 mpg, but in some cases actually does just as well or better.
I have to hold off on working on it for a week or 2 because i just got into a motorcycle accident and i have a broken foot and road rash on both knees. (damn kid turned left in front of my bike and i went flying)
I hope its not the EGR because its 200$ at autozone but i will definitely remove, inspect and clean it. I will change the O2 sensor because its the original and ive read on cars with similar hesitation to mine that just needed O2 sensors.