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Discussion Starter · #1 · (Edited)
I'm working on swapping a 97 SPI into my 91 LX and had some questions about the intake. I've read that it's recommended for the injectors to match the MAF. Right now I still have the 91 MAF with the 97 injectors, just because I didn't want to rewire it yet. I figure I'll still change it. I just haven't planned out exactly how yet.

a) For others who have done this swap, what have they done for the intake? Most of the pictures I've seen in the forums have custom intakes. I'd use the 97 intake, but it doesn't look like the filter box will bolt up easily. I can keep the 91 intake with the MAF from the 97, but I wasn't sure if it's enough to just swap the MAF, or if I need the MAF housing as well, which won't fit the air tube from the 91. And that leads to the next question...

b) I've seen people with knowledge of how the ECU works explain that the MAF needs to match the injectors, but then people's actual experiences seem to vary. Some run with them mismatched and have no problems. Some find that they need to switch back to the 1.9 injectors. There doesn't seem to be any explanation for why one solution doesn't work for everyone. Could the MAF housing have something to do with it? The diameter is different, so it seems like a 97 MAF in the 91 housing will give a different output compared to a 97 MAF in the 97 housing.

Right now, the car starts up and idles and revs fine with the 91 MAF, but that's as far as I've gotten. I'm also swapping to manual transmission and I don't have the clutch pedal in yet, so I haven't been able to take it for a drive.

Edit: I just compared my 91 airbox to a 94 and saw that the MAF housing in the 94 is larger and looks the same as the 97. So maybe that's the solution? I can use the 97 MAF and housing with the tube from the 94.
 

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1.9 injectors are 16# single hole
spi injectors are 19# 4 hole.
if you run the injectors with mismatched maf, it will either run rich or it will run lean depending on the combination. the pcm has no idea what injectors or maf is in it, all it sees is the 0-5v signal from the maf and then controls the injection duty cycle. the maf is wired differently on the spi than it is on the 1,9 and uses a different connector so it is not as simple as swapping the parts. you will need the whole sensor and housing and connector. also the injectors are different length. 1.9 injectors are shorter and stubby. you can simply connect the spi maf connector to the car, the wires are labled ABCD, you just need to match them. its been many years so i cant picture the exact setup from memory.
as far as the intake tubing, i just used the factory 1.9 rubber hose connected to the spi maf, then attached some cheap ebay cone filter to it.
 

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Discussion Starter · #5 ·
I was initially referring to the entire thing, hose, MAF housing, and airbox, before I realized the tube and MAF housing changed sizes somewhere mid-2nd generation. With my 91, I didn't see an obvious way to make the 97 MAF housing fit. But I see now I can use the hose from a 94.

But the second half of the question was more general musing about making the MAF and injectors compatible. I don't dispute that the MAF and the injectors need to match, but looking through the forum history, I see postings from people who did use matching MAF and injectors and still had problems. I was speculating that one possible cause would be if someone took a 2.0 MAF and put it in their (early) 1.9 MAF housing, like I almost did.

Anyway, thanks, I think I got what I need.
 
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