I got everything for an mpfi swap for my new daily driver 91 sedan with the D15b2. now Ive read a lot of articles that seem to contradict each other concerning what the swap does to mileage. this is my dd so I want it to get the best mileage possible. some say the mpfi gets better gas mileage some say swapping makes it get worse mileage due to the ecu being tuned for a bigger displacement engine and different cam etc. all comments and opinions on this matter would be appreciated

 

well if you have a mpfi swap what all parts do you currently have? this is a issue where you gotta decide power over fuel economy. the mpfi with a si transmission will probably be the least economical but it dont bother me. i get it up to speed then kick it out of gear. so it all depends on the way you drive. but if you want the gas economical route id imagine going with CRX HF parts (tranny, ecu, manifolds) but itll be slow as ****. but once again this is where you come in as to decide whats best. and the whole swapping makes it worse because of ecu being tuned for a bigger engine.. well thats only off .1 liter lol. the d15b2 is a 1.5L motor and the mpfi parts ASSUMING you got them from a 88-91 si, that motor is a D16A6 1.6l so it might even make you go faster. i also forgot to ask you too what kind of transmission is it. automatic or manual?

 

I run a d16a6 with dx trans and still dpfi. With I/H/E it's not so bad, better than a HF, and gets good fuel mileage..so it depends.

 

what mileage do you get? and my car is an automatic LX I would be using a ps9 ecu d16a6 intake manifold from an EX and temporarily an obd0 LS dizzy

 

1) don't double post
2) when you complain like a child that "nobody knows anything," maybe you should just do whatever it is that you are doing, and take your own data. More info is found in the field than sitting behind a computer...
3) IF there is a decrease in MPG, it is minimal. really depends on driving style, climate, aftermarket parts, transmission set-up... if you shift after 3k rpm, you're gonna get bad mileage with it.

My personal experience with it? DPFI always gets better mileage, that's what it is designed for. I could get 40+ mpg if I drove my DPFI DX like a granny.
Now I get more like 500km to a tank instead of 600km.
The D15b2 was a lot more "zippy" for getting around town after the MPFI swap. Ran healthier it seems.

The cam lift difference is minimal. So little difference, most people don't swap it. You don't gain much from it, you don't lose anything from running the D15 cam.

You're reading too much into this. MPFI swap = GOOD. Just do it!
Also considering you're doing it to a Sedan, it would probably be more economical to have a higher output motor since the sedan is a little heavier. Makes sense?

 

its a double post cause the mods moved the thread

I rarely let the car go above 3k since its an automatic, even if that means going slow as hell

the issue is I really dont care much about power I just want gas mileage out of this daily driver if I want power thats why I have my b series sedan

also curious if its possible that putting a d16z6 with stock intake and headers with the obd1 02 censor could get BETTER gas mileage than my d15b2

also I dont understand how dpfi can be getting worse mpgs if youre driving exactly the same because if it was worse they wouldnt have made the hf mpfi

 

I didn't say DPFI can get worse MPG, I said it always gets better. 2 injectors vs 4 injectors... On a rare occasion, I got 700km from one tank. That was shifting at like 2k rpm and holding up traffic so I could accelerate. It was bad.
Where I'm from, we didn't get the HF so I have zero experience with it, but it does get better mileage according to the web. Restrictive intake and exhaust, long geared transmission, 5k redline, extremely de-tuned.
I guess yeah, if you want really good mileage, get the HF stuff.
If you want even better, maybe look into the HX or whatever it is with 3 stage vtec.
The MPFI intake from a D16a6 and ecu won't improve your mileage.

Is that what you want to hear?

 

what i meant is "I dont understand how mpfi can be getting worse mpgs if youre driving the same considering every fuel economy engine honda makes has been mpfi" my dad had an 86 hf and got 68mpg on the way to Louisiana several times

also I just found out the local wrecking yard 4 minutes from my house has a d16z6 for $125 and wondered if swapping that engine and riding at low rpms (but higher speeds because of vtec and hp increase) would actually net you higher mpgs. that and the fact obd1 shuts off your injectors when going down hills because of the 4 wire o2 sensor

 

To answer your question, I am also running the automatic. If kept at 100 - 105 kph (about 62 - 65 mph) I will get 36-38 mpg. That is using the pm5 ecu. If you go this route then intake/header/exhaust will help with power. I also modded the dpfi intake box by removing the barrier, and smoothing out the inside of the box. I also removed the 1st throttle body butterfly plate as it is another restriction.

 

More info on this I'm only getting 28 mpg mostly city that's horrible fir 4 gen civic or an LX civuc period

 

How do you not understand what he is talking about? Have you even popped the hood of your car? This is starting the get pathetic - it is clear you have no hands on experience with vehicles. The only information you know is from crap you read in magazines, the Internet, and what your Mom tells you.

Around 30mpg for an automatic DPFI sedan is typical. They have crap gearing and the Auto's soak up power that they don't have to begin with. You want fuel economy get some tuning software/hardware run that thing as lean as possible all over the map... You are better off finding a HF CRX and following the shift lights to get over 50mpg straight from the factory. Better yet buy a Honda Goldwing or something... wait I forgot you are only 15 scratch that...

 

not sure if it was posted or not, but you also have to take into account the intake ports on an HF are significantly smaller in diameter than a dX and SI. also an HF was an 8 valve motor as opposed to a DX and SI which are 16. these specs also play highly on the HF's high fuel economy

 

what did you personally do to get such good mileage? is it the mpfi swap, the way you drive, or did you mod your engine/intake system decently as you suggested? also what about city driving

 

seriously, youre a joke. my other sedan before i swapped it was spitting so much oil out you could have collected it off the bumper and used it again and it was getting 32 city mpg, exact same dpfi automatic sedan.
and I have no hands on car experience, really? I guess everything documented in my build thread for the past year including my b swap, wire tuck, and getting this new sedan was dreamed up and I magically made pictures of the progress. really? and no **** an HF would be better Im 18 years old if you would like the money to buy an hf, smartass, then feel free

 

There are some things you should do:

1) get some VX or HX rims - or any lightweight rim and run 175(or185)70/13 OR 185(195)60/14. Nothing wider.

2) ensure your engine is in a good state of tune. That means timed to spec, fuel filters replaced, injectors cleaned. You will be amazed how much mpg you gain when you have clean injectors. Make sure you clean out the TB with cleaner.

3) Don't drive like an *** and keep your speed under 65mph whenever possible

4) Run good quality ATF,

As for power:

Run the SI cam.

Port the DPFI intake box - remove the metal restrictor plate, and using a dremel or die grinder, remove the plastic mount for it. Make the interior smooth. I attached a pic of the box, so you know what you have to remove. Then run a K&N filter in the stock airbox. You can use an Ebay CAI if you like, just make sure you wrap it and don't use a short ram one. Exhaust - any header like off a Y8 or aftermarket will be better than the stock one that it came with for flow. I would recommend upsizing the diameter of the piping to 2" but no more (you will start to loose low end torque), and use low restriction cat and a glasspack for your resonator. That is all you can expect and hope for with DPFI..

I drive on this same setup as a daily, 120kms/75miles a day. 5 days a week. Get a constant 38mpg combined. And that is with the auto trans.

 

so you basically have a stock mpfi setup and youre getting that mileage? is that in the city? my ac doesnt work so the windows are always down but do have power steering

 

so that would be even more efficient than the mpfi manifold? thanks for the info I can try upgrading on the car what I can afford

also does anyone know if a d16z6 would actually get better mileage than the b2?

 

I did mine on a strict budget. You should be able to do same. The MPFI manifold has larger runners and makes more power, since you would be running 4 injectors instead of 2. ECU will definitely have an impact as some have more aggressive fuel mapping than others. If you want fuel economy then stay dpfi. If you want more power, go mpfi.

 

you get 40 in town?

 

what mpg do you get city driving? also what are the most important mods you would suggest under a very strict budget

 

I drive realllllly slow cars pass me all the time cause I wont let the car go above 3k thats why Im not concerned about speed just mpgs I have the maroon sedan for a "speed machine"

 

hahaha yea the automatic stinks and yea I am always careful with the pedal never have it above 40 mph too unless im on the highway

 

I get about 32 city. You should be able to get similar.

If you stay dpfi:

Mod the intake box - cost $0
K&N filter - Cost $25
Header - Pay no more than $50
Exhaust - $100
SI cam - $25

Total $200 <--that's a small budget - if you go a wrecker you could save more..

 

theres a z6 for 125 at the local wrecker for the whole engine but Im unemployed atm so I dont have the cash. also theres a complete a6 still in the ex at the junkyard. what I dont understand is how my other sedan before the swap was getting 32 and it needed rings

 

Because you were burning oil instead of just fuel..Been there done that..So what is the issue with the d15? Honestly, if you want low cost, run it as is, and call it a day. Or.. pull the exhaust off the EX if it is in good shape and take the header off the z6 and bolt it on to get a small HP increase.