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Got Boost?

The S/C install is pretty much a bolt on operation. It takes about 4 to 6 hours. My S/C was installed by my friend, Eric Amador, and I assisted. We took our time and it was installed in less than 5 hours. This was Eric's 7th Sebring install!

Once everything is installed, you need to align the blower itself so that the belt is properly aligned. If you do not do this step properly you can create a lot of belt squealing noise and belt wear. You'll end up going through a belt a week!

With the new engine load the blower creates, the idle needs to be adjusted carefully. Also, for Miata's equipped with automatic transmission, Moss ships a shift delay valve that delays the gear up shift slightly to take advantage of the extra torque now available. This delay valve is spliced into the A/T vacuum line which is connected to the nipple facing the firewall on the four runner of the intake plenum. The problem is that the existing vacuum line's inner diameter is way to big for the valve. Also, there isn't a lot of slack or space there to splice the valve in. What I did was to purchase some 5/64" vacuum line. I cut off about 3/4" and slipped it in the valve side that goes towards the transmission. Then I slipped the valve in the existing vacuum line. On the other side, I took about a 2 1/2" of 5/32" vacuum line to connected between the valve and the nipple on the intake plenum.

One of the problems you'll most likely run into a few days after the install is that the intake crossover tube will blow off under boost. Almost everyone I know (including myself) has had this happen to them. Carry a medium flat blade screw driver or an 8 mm socket wrench with you so that you can reinstall and tighten the hose clamps when it blows off. Also, for the first couple of days, check and tighten the hose clamps as needed. Do not over tighten! The kit comes with cheap clamps that will either break or cut into the tubing if over tightened. It might be a good idea to invest in high quality hose clamps with rolled edges. Another solution is to replace the hoses with high temp silicone hoses.

It's also a good idea to carry a spare S/C belt and some wire to be able to bypass the S/C entirely if you ever have any problems.

J & S Knock Sensor

A knock sensor (for automatic boost retard) is not really required for a normal Sebring S/C installs. However, if you don't have some sort of boost retard, you need to set the ignition timing to 8 degree BTDC if you run 93 octane fuel. If you live in California, like me, and can only get 92 octane gasoline, you have to retard it even more to 6 degree BTDC. The combination of that much retard and the load induced by the S/C itself causes a loss of low-end torque. So when you step on the throttle from a dead stop (tip-in), the car hesitates and feels like it going to stall for about 1/2 second. It looses that "eagerness" that the Miata is known for.

If you use a MSD boost retard, you can set the timing to 10 degrees BTDC. The MSD unit has a boost sensor and it will retard the timing based on manifold pressure -- even if the engine is not knocking.

With the J&S, you can set the timing to whatever you want, and it will retard when it senses engine knock through a microphone that gets bolted on to the engine block. I set the timing to 14 degrees BTDC. Now I have gobs of low end torque, the overall power seems to have increased across the entire RPM range, and the tip-in hesitation is 90% gone.

The J&S instructions suggest you install the unit in the passenger foot well, then run all of the wires over the drivers side, route it through the firewall, and then connect them under the hood. This seemed a bit silly so I installed the J&S next to the ECU behind the passenger seat and wired it right at the ECU. The only wire that needed to go through the firewall was the microphone wire. Again, the J&S instructions suggested taking it through the driver side firewall, then routing it through the front of the fire wall to the passenger side on the engine compartment (where the microphone is bolted to the engine block). We ran it right through the passenger side firewall using the A/C condensation line grommet as the feed through point. One other note, the instruction tell you to bolt the microphone to the starter motor bracket bolt. My Miata (a '97 model) does NOT have the bracket which they speak of. However, the stud is still there on the engine block, so we bolted the mike to the proper location, sans the bracket.

Here is the wiring we used. Note that this is for a '97 Miata and they seem to be slightly different that older Miatas. It seems they may have changed the color of the wires slightly. If you own a Mazda Miata Workshop Manual, refer to section Z in the back of the manual for the schematics, pin numbers, and color codes.

I also purchased the J&S dual display. This displays shows both the retard level (very useful for adjusting the knock sensors sensitivity) and the Air to Fuel (A/F) ratio. The monitor has two separate plugs: one for the retard display, and one for the A/F display. The retard display connector plugs right into the J&S main unit. The A/F meter connector plugs into another two wire female connector which needs to be spliced into the ECU again. This is where it seems to be different from year to year on the Miatas. The '97 Miata has an OBD II system with a oxygen sensor output and a sensor ground.  It is important that you hook up the A/F meter to the sensor output and sensor ground (instead of chassis ground) or you can create a ground loop and get false readings.

Adjusting the knock sensor sensitivity can be pretty tricky. On 1.8L engines, the middle position is a good place to start. I recommend you keep the J&S wires long enough so that you can pull the unit out from the back of the seat and place it on the passenger side. This will make the alignment very easier. To align the J&S, it's better you take a friend with you. Drive the Miata on the freeway and reach a 80 to 90 MPH speed. Maintain a constant speed so that the engine is not under boost. Then have the other person watch the retard display and slowly increase the sensitivity until it starts retarding. Then, slightly back off on the sensitivity.

Performance Review

The power increase is just what the doctor ordered! Accellaration from stop (0 to 40) is awesome for normal daily street driving. On the freeway is does great, however, is stops pulling after about 80 MPH. I want more power, though. :-)

Future Plans

I'm looking forward to the Moss 8.5 PSI boost kit. On the dyno, Moss is seeing about 165 HP at the wheel. I'm concerned about running that much boost without an intercooler. Moss is also working on an intercooler, but it looks likes it will be 4 to 6 months out before anything will be available.

If you would like more information about Sebring Superchargers, please visit the Sebring Supercharger Owner's Registry (SSCOR).

Water Injection

Some members of the SSCOR are experimenting with water injection as a method of reduce in the charge intake temperature. Reducing the intake temps will decrease pre-detonation (pinging). By eliminating pre-detonation, you can advance the ignition timing to get better over-all power. Rene Mapua has been kind enough to do a write up on his Aquamist water injection system and has included some pictures. Click here to see Rene's write up.

 

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Last Modified: June 11, 1998
Copyright (C) 1998, Kory Hamzeh. All Rights Reserved.