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rx-7 VAF swap

2468 Views 11 Replies 4 Participants Last post by  siragan
does anybody know exactly what the 1st, 2nd, and 3rd gens RX-7´s use for an airflow sensor on the intake tube?

I´m upgradig my air metering system, but I don´t want to spend a billion dollars on a new ECU and MAF, so I´m planning on plugging in an RX-7 air meter in place of the stock GT VAF.

I´ve been told that the 1st gen airflow sensors will "plug and play" into my system, no ECU changes or anything necessary (only tuning, which I can do), but I´m not sure if the 2nd gen airflow sensors will also "plug and play" into my system.

Will it work? do 3rd gen RX7 intake sensors plug and play in?

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[ This message was edited by: siragan on 04-02-2003 10:20 ]
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I installed a VAF from an 88 RX7 in my 91 Escort GT during my GTX swap, and don´t seem to have too many problems other than breaking up under load before 4,000 Rpm´s. I am working the bugs out now, I´ll let you know how it works :cool:

use that link to help ya out in finding the right VAF and the directions for tuning it. i think it is off the 87-88 rx7 NON turbo. it will have a B on it.

heh, i thought it was turbo, but guess not. was a while since i put mine on.


1993 Escort GT


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[ This message was edited by: Slapyo on 04-02-2003 14:14 ]
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04-02-2003 at 11:53, forcefedgt wrote:
and don´t seem to have too many problems other than breaking up under load before 4,000 Rpm´s.

What do you mean by "breaking up"? What other problems have you had thus far? Where did you pick yours up?

Slapyo- thanks for the link, that´s really really helpful. So it sounds like I CANT use a 2nd or 3rd gen intake VAF... dang.

And slap- you said it had to be turbo, but the one the guys used on the page was from a "87 non-turbo 13B".

I can´t wait to get my new intake system all gathered up and installed. That along with a new 2.25" exhaust and I´ll have a pretty cooking NA ride :)
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1990 Protege LX - VAF Swap

RX7 VAF Swap

1987 RX7 non-turbo VAF swapped
into a 1990 Protege LX

  • 90-94
    Protege LX (DOHC)

  • 90-94 323 LX Hatchback w/1.8L

  • 91-96 Escort

  • 91-96 Mercury
    Tracer LTS

  • Will also work
    with the BPT GTX/GTR engines

The Pro VAF is on the left and the RX7 on the right

Here´s the Cold Air Intake w/Pro VAF on the Left, w/RX7 VAF on
the right

Click on these thumbnails to see
full size

Here´s a few shots of the homebrew bracket I concocted about 9
years ago when an HKS Power Flow Filter resided before the RMM K&N filter.

Tuning: 101

Click on these thumbnails to see
full size

The thumbnails above
link to descriptive photo´s pointing out the locations of the items described in
the step-by-step below.

In most cases, the RX7 VAF will need to be tuned to
the ECU of the Protege/EGT. In order to tune it you will need the following:
Multimeter, sharpie or similar permanent marker, tape, small pick tools or small
screwdrivers, utility knife, silicone sealant, battery connector removal tools,
general mechanics tools and some patience.

The RX7 VAF needed is an 86-88
non-turbo "B" code VAF

Look for this sticker on the VAF, the
numbers will be identical.

The RX7 VAF referred to on this
page is from a 87 non-turbo 13B


1. Depending on your present set-up, removal of the VAF
is quite simple. Disconnect all intake clamps and hoses, including the filter or
filter box, the VAF unplugs from the harness, (see photo) NOT BY UNSCREWING IT!!!! but buy
carefully prying back the spring clips on either side and sliding it off. The
OEM plug still in the car, will plug in directly to the RX7 VAF.

2. You´ll notice with a side by side comparison that the
RX7 VAF is larger and the outlet diameter to the H-Box is larger. 3" hose
adapters do fine, as a 2.5" did it on the OEM VAF. I suggest using a nice
2.5" to 3" hose adapter for connection to the H-Box, makes a much
better seal than a 3" to 3". The same air filter adapter from HKS fit
fine on the RX7 VAF inlet. But you´ll also notice that the OEM VAF used studs
and nuts, the RX7 VAF uses threaded holes and bolts. So when you go and get your
found an 87 RX7 engine still fully intact, just the interior was gutted, I grabbed as many OEM bolts as
I could, makes for easier mounting of
brackets or whatnot to be able to use a factory threaded locations...

3. Make sure to save all OEM parts that go with the OEM
VAF, including the VAF itself, as you may need to re-install it all if the RX7
VAF is defective or some other component is defective and the car won´t run
correctly with the RX7 VAF.

the RX7 VAF

1. Make sure your intake system is completely intact
before you go ahead with this tuning process.

1a. Remove negative battery cable from battery. This
resets, the factory ECU to reboot with the new air flow specs. Let car sit with
cable removed for about 5 mins. This can be done while you cut the cover off the
VAF so save time. Or even cut the top off before installing and disconnect
battery while removing the old VAF would save even more time.

1b. Remove the black plastic cover from the VAF by
cutting the silicone with the utility knife, be careful not to cut too deep as
the black cover has an edge on it that needs to be there.

1c. Reconnect and start engine, the engine may stumble at
first, but it will smooth out somewhat to allow for adjustment. So have your meter
and tools set up to act rather briskly.

2. With engine running, take your Multimeter Red probe,
and probe the O2 sensor wire coming from the single wire O2 sensor on the
exhaust manifold, (see photo) The wire runs up along the block to under the
distributor, you can probe the wire anywhere along it´s path. Put the Black probe to chassis ground. As
I understood, you
are looking for 0.45volts at idle. I found mine best suited dancing around 0.53v
and 0.78v, so I left it as is. Which in turn was 5 clicks.

3. The clicks mentioned above are in relation to the now
opened VAF. (see photo) You will see a large wheel spring with teeth on it. You will also
see a small black spring that grabs at the teeth to hold it in place. With your
marker, mark the wheel where the springs sits on the wheel BEFORE YOU TOUCH IT.
With your pick tools or small screwdrivers, carefully pry the spring back and
move the wheel towards the fender, (CCW counter clockwise) It may take more or
less "clicks" for your particular application, but generally it´s
around 5 or 6. It may even need to be turned CW clockwise, it all depends on the
application, year and model the VAF came from, condition of the VAF and the
ECU/vehicle its being mated with. Once
you have it tuned to a nice smooth idle, your meter should read within 0.45v and
0.78v for the Protege/EGT BP 1.8L DOHC. Again, readings may vary. Consult your
repair manual for factory specs.

3a. You will notice the engine smooth out as you turn
the wheel on the VAF. Once you have a nice smooth idle and your meter is within
the specs, your all set. Cover the VAF with the Black cover with some tape
temporarily and go road test it. Make sure the car warms up. You will notice a
nice boost of 5hp around 6000rpm. This swap is really only to improve on the top
end at 6000rpm
and above, otherwise the RX7 VAF works just like the OEM VAF, there´s no
difference until 6000+rpm.

Please be aware that this is just a very basic tuning
process and that I do not guarantee it´s results, the info provided here
is of my own experience and it MAY NOT work for you. Don´t blame me, THIS INFO
IS TO BE USED AT YOUR OWN RISK. If you have any questions, comments, or
additional info I may have overlooked, please feel free to email
me, or use the Feedback Form.

For additional info on this subject, visit:
2.5L V6 MX3 GS
This site has some EXTREMELY valuable info regarding Mazda´s
and their crossover parts and all kinds of other great info.

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[ This message was edited by: siragan on 04-02-2003 13:29 ]
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It sputtered like the timing was off or something. I am working on it now. I´ll keep you posted!
I kinda stole their page on the swap... I left all the copyright stuff at the bottom to give them credit, and it´s for the benefit of humanity, so my cause is justified :-]

forcefed- are you using a cone filter or the stock air box?

Is the outlet to the intake hose still the stock 3"? (stock intake hose ID on the 1.8L is 3" right?)

Thanks for the help guys I really appreciate it.


[ This message was edited by: siragan on 04-02-2003 19:00 ]
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anybody know if the RX-7 I take this off of has to be non-turbo?
NON Turbo. It will have a ´B´ code designated on the part.
And what do the second and third gen RX-7s use for intake air sensors? I don´t want to limit myself to just the RX-7 VAF, I´d like to hear my options...

...so I can weigh them, whaddayasay.... :-]
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