everyone talks about making the dx multiport instead of doing other mods...... is it that big of a difference? will it make it similiar or stronger than an Si engine?

 

It's a huge difference over stock, and it alows the car to respond to other mods better as well. The DPFI TB acts like a bottle neck, it really doesn't make any difference if you put a better flowing exhaust or CAI on a dpfi car when all of that air still has to make it's way through that tiny throtle body. I doubt if a 1.5 with mpfi swap has the same power as the 1.6, but it brings it a lot closer. I guess I'll find out how much closer when I put my 1.6 in.

Another thing to consider is the tranny gearing, you're not really comparing apples to apples if you leave the DX tranny in and try to race an Si. the lower FD in the Si is going to make it quicker off the line.

 

honestly- not to start a flame - that's not true at all

 

second that
i got right now a DX tranny for now.... until i rebuild my Si...
its still pulls strong... not as fast as the Si tranny.. but i can still spank Si's


[Modified by JDM EF9, 8:35 PM 12/19/2002]

 

i love the dx tranny, not that far off from a si, and it almost has the same gearing as a 92-92 si/ex

and the 1.5 with the mpfi swap will make nearly the same power a si does, because the compression is higher on the 1.5, so it makes up for the displacement. think about it the si makes 105hp (108 in the 91) and the dx makes 92hp you give it atleast 10hp for the mpfi swap, and you are right there

 

if im not mistaken the a6 head has a more aggressive cam so that would be missing as well. but I could be wrong.

 

the heads are the same but the cams are different from Si's to Dx's

 

there would be a little lack of power, but unless you want the stronger bottem end, there in no need to do a whole motor

 

Im gonna put a y8 head on my dx block, and hopefully that will respond good, i got an 88 si tranny in the garage that i gottta swap casings off the dx i took out(casing wont come off for ****, lol), and i am gonna pick up an act clutch for the y8 and put it on there, and its my daily, hoping it wil be pretty quick.

 

Do 88 trannys have diff axles than 89-91? I thought I heard there was a difference between 88s and others

 

yeah i just got my 89 civic hatch dx, its has dpfi and i was wondering what i would need to do to change it over to mpfi? any help would be appreciated.

thanks
eric

 

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as for being the D15B2 w/ MPFI being better than an D16A6, it's too close to compare. Yes, the Si has 100cc more of displacement and a slightly (very slightly) more aggressive cam, and that's it, aside from the tranny (which doesn't reflect power, but the Si trans is the best D-series cable tranny). Power output is within 5hp between the two (D15B2 /w MPFI and D16A6), so they're about equal. The Si is a better choice for a vehicle in whole, but if you have a DX and want the performance of an Si, do the MPFI and get an Si trans. Don't waste the time for an Si cam, it's not even worth the labor for the power gain (done it, not worth it). If you're going to change your cam, atleast buy one from Crane/Gude/etc.

 

I wrote this up for someone and saved it so I could just cut and paste:

The MPFI swap is the best mod you can do to your car short of an entire engine swap. and if you do want to do an engine swap, you have to do an MPFI swap anyway. our cars come from the factory with 70 crank HP, the MPFI swap pushes us up to somewhere around (this is a guess) 110. Plus, with the larger throtle body, your car will be more responsive to other mods like I/H/E and cam. the DFPI TB is so restrictive, it bottlenecks the air flow so much that any other mod you do doesn't really do any good.

parts needed:
I recomend getting all of these parts from an 88-91 civic EX or Si, or CRX Si (I've been told that the CRX Intake manifold doesn't flow as well, never saw proof though) There are some other options, but for simplicity, it's best to get it all from one of these. also, If you have a manual trans, get the parts from a manual trans donor car (and auto for auto) I got my parts off of Ebay, a couple of broken sensors and bad parts cost me in the long run.

1. Intake manifold with Injectors, Throtle body, and all sensors intact
2. Injector resistor box
3. ECU
4. Distributor (the EX/Si dizzy has an extra sensor in it that you will need)
5. engine wire harness (you'll need to steal some plugs off of this)
6. New intake manifold gasket (if the TB or any sensor gets removed, it will need a new gasket as well)
7. New Injector seals (If the new intake mani has been sitting for a period of time, the old seals will probably be dried out and leak)
8. New Cap and rotor (if you recently replaced yours, the cap, rotor, coil, and Ignitor from your old distributor will all fit the new one)

The swap is easy to do, an experianced mechanic could knock it out in less than a day. Be prepared to have your car down for a week just in case there's some bugs to work out though. You never know when you're using used parts, don't get stranded!!

The mechanical stuff is pretty basic, especially if you have a Helms manual. (I did it with a Haynes manual because I'm too cheap to buy a Helms) The only thing I can say is make sure everything is clean and seals properly. When I did the swap on my car, The bracket that holds the back of the manifold up was bent, it was pushing up on the back of the mani and it wasn't allowing the gasket to seal properly. I also had problems with my injector seals leaking and the distributor had a bad ignitor.

The part where most people struggle is the wiring, your current setup only has wires for 2 injectors, you'll need to run wires for 2 more. Also, you need to run wires for that new sensor in the distributor I mentioned above. the best write up I've seen on this is:
http://hybrid2.honda-perf.org/tech/4gdxtozc.html
When I did my swap, I did all of the wiring with NO splices under the hood. Everything looks completely factory. I Just wish I took pictures of the process.

The only downside about the swap is, because you are using a 1.6l ECU on a 1.5l engine, the car will run rich. this can be fixed using an adjustable Fuel pressure regulator. by turning down the fuel pressure, you can lean the system.

Hope this helps,
Louie
thumpu77@hotmail.com

 

It's the input shaft that's different, 88 has 21 splines, 89-91 has 20. also, 89 has a smaller diameter clutch than 90-91

The only place where you run into axle differences is on the hub side on the Civic Std. (and possibly DX, I'm not sure) but all us models are the same on the tranny side, so just get axles to match your car, not the transmission you're swapping in.
Of coarse this logic goes out the window if you start messing with ZC trannies.

 

DX and SI axles are the same....the HF has the smaller axles...
ZCs will use the intermediate shafts however if you're looking for replacements look at a 90 integra.


Listed as a "downside" of running a pm6 with a d15 block with another head on it is that it will run rich....this is not the case however if you have a CAI. It actually will compensate very nicely for the extra air coming in.

~Alex

 

i just tried this, the inside of the tranny casings are completely different. i blew my dx tranny and my friend donated a si tranny but the bell housing had a chunck taken out of it. we thought it was jist as simple as swapping the bellhousings, but we were wrong.

 

so a SI tranny will bolt on no prob onto a d15b2?

 

Yep it will bolt right on.

 

Thanks alot man this helps

thanks
eric

 

yes, as long as you use a20 spline clutch, presure plate, & flywheel with a 20 spline tranny, and a 21 spline clutch, p. plate, & flywheel with the 21 spline tranny.

 

I believe Sport Compact Car had an article about the DPFI to MPFI wiring a couple of months back that seemed pretty good. Just another place to look.

 

i jus picked up a 89 si motor the other day and gotta drop it in my crx dx...but it didnt come with a Distributor, i know ne crx si one will work, but what about other cars? what years, models, and makes will work with the d16a1

 

so if i get a si tranny my dx clutch and flywheel wont fit in it?

 

the only diff between the si trans and dx i heard is the final drive.

 

Are you kidding me??? The DX tranny is a POS! I have an 88 DX, and that thing has the tallest gears ever! My 89 Si tranny was soooo much better!!!