With a "big" VAF, you'll need a EEC that is calibrated to read it, otherwise your VAF will be reading a different amount of air than your EEC is calibrated for. This will result in a LEAN condition at WOT. Do not run with the wrong VAF for the calibration of the EEC. There are two options: get a EEC that is calibrated (85.5 - 86 SVO or 87-88 Turbo Coupe) OR get a "chip" that is calibrated and plugs into the stock EEC.
If you can find an '86 SVO ECU use it/get it. They are tough to find though.Pass on the other SVO boxes.
The spark and fuel tables in a PE SuperChip are not as in the SVO ECU. The timing is more aggressive and the fuel table is too much. This may be a problem with a not too efficient IC in the summer. You may need to pull back your initial timing. A lot depends on where and how you drive. SuperChips are $265 and a custom program that works well is an extra $75.So the chip is an "tuned" '86 SVO ECU.
When installing the "SVO" VAF the stock XR hose is re-used (will fit...both ID/OD and length) from the air cleaner box outlet to the VAM inlet, (tight is good...big deal...= stay put), and the stock TC hose is used (along with Greg Paul's very nice adaptor), from the VAM to the re-indexed turbo inlet (also fits very well, in length, etc.). These have been in place now for approx. 10k miles with no problems. Of course, YMMV. Don't fight it. If you must make major mods, look to adding a 2nd snout into the fender or adapting a cone type performance K & N, perhaps. Don't ignore the need for cool air supply, however.
If you are having difficulty here, make sure everything is clean/dry, and try again, making sure patience is in use. Don't forget the thin stability wire inside this hose (VAM to Turbo). Silicone glue(s) will only act as a lubricant, and prompt the hose(s) to pop right back off when installed. There is no need for glue(s)...there is a need to have clean and dry surfaces, as well as new or serviceable clamps of the correct length. The (stock) items did not go together easy when new...they do R & R very easily when aged, however.
What won't work is attempting to reuse the mounting bolts and original locations. Due to the increased height of the TC VAM, these will no longer be usable. However, this increased height means that the TC VAM is retained (clamped) within the stock XR bracket (lower air cleaner & bracket) without requiring any locating bolts, except the two from the air box to the top of the VAM. This can all be done without major grief, fabrication, or modification, and the result is a reliable installation. Don't forget to increase the size of the opening for the wiring harness/connector. See the Merkur Resource pages for details/photos.
Installing a "big" VAF
Text and photos by Ken Tidwell
The Turbo Coupe / SVO meter flows approx. 360 CFM, and the XR meter flows approx. 280 CFM.
Part numbers for various VAM's as follows:
* 1984 SVO E4ZZ-12B529-A
* 1986 SVO E4ZX-12B529-AA
* 1986 Merkur E5ZF-12B529-AA
* 1988 ThunderBird E7FS-12B529 AA
All connections are the same...however, when installing the larger meter in the 'frame' that holds the air cleaner and meter, the opening for the connector must be enlarged upwards, as the location for the connector is higher when installed. There are no holes to mount the larger meter...I just squeezed it in, and when the air box is bolted back down, it clamps the meter in place. Use the stock XR rubber connector from the air cleaner to the meter, and the Thunderbird rubber connector from the meter to the turbo inlet. (For a higher flow installation see the Air Box article)
The meter is found underneath the air cleaner...passenger side, front of the engine compartment. Remove the air cleaner...the wiring harness (located on the left side of the meter)...there are 3 fasteners holding the frame in place. One is a large Phillips screw on the fender, and two nuts low down on the inside of the fender, holding the coolant spill tank in place...remove these two nuts and move the spill tank out of the way...lift the frame upwards...there are two rubber grommets that slide down into place when reinstalling...disconnect and/or remove the rubber coupler from the turbo inlet and lift the frame (containing the VAM) out of the engine compartment.
Remove the VAM from the frame by removing the three bolts found holding the body of the VAM to the frame.The larger TC VAM is a puzzle fit into the frame...be sure to remove the lower portion of the air cleaner box first and bend that little tab!
These are photos of the vane air meters from a (1988) Thunderbird Turbo Coupe, and from a (1986) Merkur XR4Ti.