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Question on change to MPFI.

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Question on change to MPFI.

Postby sstupid » Fri Oct 14, 2011 10:03 pm

I read the whole article on how to change the existing DPFI harnes to MPFI, but I was wondering if I could just take the whole harness out of a wrecked Si and put it in my car. I have found a local Si and it has the PCM and harness. Can I just do that, instead, or is it more difficult in the end?
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Re: Question on change to MPFI.

Postby el_jelly » Sat Oct 15, 2011 9:50 pm

Some of the plugs won't fit in the end, however if you can have the full si harness you can use some parts of it for the dpfi conversion plus if in the future you want to do a wiring tuck you can use the remaining of the harness to extend the stock one and use the same wire-colors.
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Re: Question on change to MPFI.

Postby lrowland1988 » Mon Oct 17, 2011 8:45 pm

el_jelly wrote:Some of the plugs won't fit in the end, however if you can have the full si harness you can use some parts of it for the dpfi conversion plus if in the future you want to do a wiring tuck you can use the remaining of the harness to extend the stock one and use the same wire-colors.


What plugs wont fit? because i have the full harness dizzy and alternator from a SI and everything else on my engine is the same as the Si the only things that need changing are the dizzy and ecu. in theory the intake and si harness should be plug and play. i have inspected every plug on my harness they are the same. the si was a 90 and my dx is a 91
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Re: Question on change to MPFI.

Postby el_jelly » Tue Oct 18, 2011 5:54 am

my good friend google says:

Image
"...the DX chassis harness that the engine harness plugs into has a round 14-pin connector and the Si has a different size round 8-pin connector - the DX chassis harness has only 2 fuel injector wires in it and you need 4 - the DX chassis harness has no wires for the Cylinder Position Sensor in the distributor and you need 2 - you add the wires for both of these during the DPFI to MPFI swap - you need to use your DX engine harness and do the DPFI to MPFI wiring changes - engine harnesses are not interchangeable between car models and some are not even interchangeable between different years of the same model"
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Re: Question on change to MPFI.

Postby LONO100 » Tue Oct 18, 2011 9:18 am

i dont mean to thread jack but i didnt want to start a new post for this quick question. i have been reading about converting from dpfi to mpfi, and i wanted to know how this would effect my fuel efficiency. i was interested in this switch not so much for a power increase but for fuel efficiency. in theory it sounds like it would be more efficient in terms of fuel distribution to go mpfi, but are there any noticeable gains in MPG for anyone who has switched from dpfi to mpfi? thanks.
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Re: Question on change to MPFI.

Postby 91B16AHB » Tue Oct 18, 2011 2:19 pm

No... DPFI is designed for maximum fuel efficiency. The ONLY reason to switch to MPFI is to make more power.
And will an acura crx seat on the 90's era fit my 90 dx?
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Re: Question on change to MPFI.

Postby LONO100 » Tue Oct 18, 2011 6:01 pm

awesome, thanks for the answer. now im glad i wont be tempted to make the conversion. im trying to max out my mpg with my civic and the way the mpfi, it just seemes like it distributed fuel more precisely and efficiently than the dpfi. thanks again, now i can tackle this rattling exhaust problem.
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Re: Question on change to MPFI.

Postby sstupid » Wed Oct 19, 2011 6:51 pm

Thanks, jelly. I won't waste my money on the harness, then. ;)
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Re: Question on change to MPFI.

Postby el_jelly » Thu Oct 20, 2011 12:45 am

In theory you can swap the harness, however the work needed to mate it to the rest of the harness and the additional wiring required makes it a less favorable solution than to convert the stock harness to mpfi. In some cases it may be feasible, for example if you buy the shell of a dx/std/lx/hf and it doesn't have any wiring on it, and you have all the wiring (inside and out) of the si, then is just a matter of putting everything in.
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Re: Question on change to MPFI.

Postby Scott91EF » Tue Dec 27, 2011 8:35 am

LONO100 wrote:awesome, thanks for the answer. now im glad i wont be tempted to make the conversion. im trying to max out my mpg with my civic and the way the mpfi, it just seemes like it distributed fuel more precisely and efficiently than the dpfi. thanks again, now i can tackle this rattling exhaust problem.



I converted from DPFI to MPFI and I haven't seen a drop in my fuel economy. I did the conversion and switched to a 5-speed SI transmission (I had the 4-speed that came in the STD) and I average close to 40 mpg (never below 37 and as high as 42). The combination of the 2 mods did give me more power but as long as I drive sensibly there is no loss of fuel economy. I still have the D15b1 motor but if I want to swap on down the road at least the MPFI conversion is done.
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