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1992 Ford Mustang Notchback - Automatic Overtaking Done Quickly - Tech
Improve Your Aod Transmission For Quicker Elapsed Times With Help From TCI Automotive.
Over The last several issues, you may recall numerous articles featuring the buildup of a '92 black Mustang notchback unofficially called the Little Juice Coupe. This month, we'll give you a brief recap of the modifications and progress the car has made during its 1,320-foot test sessions. We'll also show you the first part of the Mustang's high-performance transmission install.
The AOD has always been a hindrance in early Fox cars, and this one is no exception. Our Mustang's AOD transmission has seen better days, and its slow shifts indicate it's having a hard time coping with the added horsepower and torque from our engine mods.
The funny thing about this project is that it started out as a last minute fi ll-in. Originally, we had planned to install the Nitrous Express nitrous-oxide system on our '93 Cobra project, Stolen Goods, but we came across this LX and decided a low-buck 5.0 buildup would better suit those readers without fat pockets. It worked out for the best, as this lethargic AOD-equipped coupe needed some motivation.
Our subject vehicle had received some mods prior to us getting our mitts on it, and in addition to the 70,000 miles on the odometer, the coupe had accumulated a 3.55 rear axle ratio, Ford Racing Performance Parts underdrive pulleys, Flowmaster two-chamber mufflers, a K&N panel filter, and MM&FF's 10-minute tune-up. Even with a decent amount of mods, the coupe eased through the quartermile at a leisurely 15.05 seconds and tripped the mph clocks at 92-not bad, but barely enough to keep ahead of your average Honda Accord these days.
We took our time installing the Nitrous Express Stage One EFI system, and the cleanlooking installation shows it. We hid the NX window switch and TPS full throttle unit in the glove compartment, and the nitrous solenoids inside the fender. We also upgraded the fuel system with a fuel pump from Brothers Performance. The BBK 255-lph (PN BBK1607) in-tank pump assured us that the engine and fuel solenoid were getting the proper amount of fuel. Using a set of 245/50/16 Nitto drag radials and NX jetting for 100 hp, the black coupe sped to a 13.62 at 104 mph in the quarter-mile. We backed that up with a 13.75 at 104 mph--an awesome result with a 1.5-second improvement in elapsed time, as well as a 12-mph increase in trap speed.
Our next round of mods began with an offroad x pipe system and 15.8-inch equal-length shorty-style headers from DynoMax. We complemented the improved exhaust flow with an FRPP Cobra intake manifold. By the time we completed these mods, ambient temperature at the track dropped some 30 degrees, so there was a little better air in which to run. On motor alone, we improved our elapsed time from 15.05 to 14.55, and our speed went from 92 to 97 mph. Adding our 100-shot of nitrous allowed us to drop our elapsed time further, going from a 13.62 to a 13.06. Our mph went up from 104 to 110. We were really cooking now.
Since we were so close to the 12s, we stepped up to the 150hp jets. Before doing so, however, we thought it was pertinent to address the stock ignition system. Calling upon the folks at MSD Ignition, we ordered a Digital 6 ignition box, MSD plug wires, and an MSD Blaster Coil. The Digital 6 provided us with a timing retard feature where we could run our advanced timing during normal operation, and then once it received our 12-volt signal from the nitrous arming switch, it would pull 4 degrees of timing.
Back at the track, we managed a 14.67 at 96.59 mph on motor, and with the 100hp jets, the coupe picked up to a 13.21 at 108.99 mph. Weather conditions had a big part in the slower elapsed times, as the ambient temperature was now some 25 degrees warmer than our previous nighttime track excursion. On our next attempt, we heated the tires a bit more. Installing the 150hp jets took all of a few minutes, and our fi rst effort with the big hit was a 13.06 at 112.48 mph. We encountered massive wheelspin at the nitrous hit, though, and subsequently had to pedal the car to get it to hook up again.
On our second attempt, we put more heat into the tires during the burnout. The tires spun, but not as much, and e.t. fell to a 13.04 at 111.84 mph. Unfortunately, we couldn't improve beyond that, as our next three passes came in at 13.14, 13.10, and 13.12. All three runs lit up the tires at the nitrous hit.
Obviously, we needed to remedy the traction issue, but we also wanted to give the engine itself a bit more gusto. To do that, we installed a set of FRPP 1.7:1-ratio roller-rocker arms, a 65mm throttle body, and a mass air meter upgrade from C&L Performance. Since the dragstrip was closed for a couple of weeks, we trekked to HP Performance in Orange Park, Florida, to perform before-and-after dyno tests of the components.
Our baseline came in at 228 hp and 276 lb-ft of torque, which isn't bad given the mild modifications in place and the fact that we're cranking the horsepower through an AOD transmission. With these new parts, we picked up 15 hp and 8 lb-ft of torque at peak, with even greater gains seen across the powerband. A custom SCT chip for the A9P processor improved horsepower and torque by 9 and 14, respectively, for a total of 243 hp and 284 lb-ft of torque. Cracking open the nitrous bottle for the 150 shot produced 378 hp and 486 lb-ft of torque at the wheels.
To address the traction situation at the track, we called Nitto Tire and ordered a set of larger drag radials. Our car's owner, Brian Bohnsack, had just upgraded the coupe with Wheel Replica's new Saleen 17X9-inch replica wheels, which led us to the 275/40/17 size. We complemented the drag radials out back with a pair of Nitto 555s up front. Bohnsack also scored a deal on some suspension parts, including Strange adjustable front struts, Lakewood 50/50 rear shocks, and some UPR lower rear control arms.
As the tracks hadn't yet opened for the new season, we still had time to do more work to the engine. We called FRPP and picked out a set of its GT-40X extra performance Turbo Swirl cylinder heads. The heads were a no-fuss installation, allowing us to retain our 1.7:1 bolt-down roller-rocker arms. With 1.90 intake and 1.60 exhaust valves, the heads picked up 24 more horsepower and 22 lb-ft of torque at the wheels.
Finally, the track opened, and we hit the local test and tune evening event-nitrous bottle loaded and ready. Traction was never an issue on motor, and the car ran a 13.78 at 101 mph. We didn't waste much time before the 150 jets were slid in the NX Shark nozzle, and our fi rst pass scored a 12.70 at 114 mph. The transmission took so long to shift that it ended up tagging the rev limiter on the 1-2 exchange. Our next pass, sans rev limiter, picked up to a 12.62 at 115 mph.
We called it a night after that, as the Mustang began making a noise from the transmission area. It turned out to be the starter, but we knew the transmission couldn't be in that great of shape either, since we'd shift at 4,000 rpm and it wouldn't complete the gear change until 6,000 rpm.
With the nitrous-oxide delivery on a 3,000-rpm window switch, we knew we wanted a higher-stall converter to get us into that range sooner. We also knew we had to tighten up the shifting. Both of these should drop elapsed times greatly, so we contacted TCI Automotive to see what they had.
AODs Are Fun, Too
The good thing about having an AOD these days is that a bunch of companies have modified it inside and out, and complete high-performance transmissions, as well as parts, are readily available. Knowing that our slushbox was on borrowed time, we called TCI Automotive in Ashland, Missouri, and discussed our options with TCI's Stanley Poff.
Since this is a street-driven Stang 90 percent of the time, we stayed conservative with our torque-converter stall speed. TCI offers its StreetFighter, which has a stall speed that is 1,500 rpm more than stock. But we opted for the Saturday Night Special stall converter (PN 432600), which is a lock-up-type converter that offers a modest 400- to 500-rpm increase in stall speed over stock.
TCI's StreetFighter AOD transmissions are fully remanufactured units that use only updated '88-'93 cores. All of the bushings, seal rings, and gaskets are replaced with quality OEM parts from Federal-Mogul and Clevite, while the steel and friction elements are replaced with new Kevlar-lined pieces. All of the bands and clutches are replaced with higher-performance versions, and the failure-prone, direct-drive input shaft isreplaced with TCI's heat-treated Vasco 300 high-performance version.
TCI also installs its own special pressure regulator spring to increase torque capacity. A Trans-Scat kit is installed for firmer shifts, and it also eliminates Third gear pressure cutback, which raises torque capacity in Third and Fourth gears. TCI offers both lock-up and non lock-up transmissions, and we chose the lock-up version for better economy.
Each transmission assembly is statically tested for individual hydraulic circuit integrity before valvebody installation, then dyno tested to verify proper functions, pressures, and cooler flow.
Our AOD (PN 431000) was also equipped with TCI's new constant-pressure valvebody, which prevents end users from burning up the transmissions due to improper throttle-valve cable adjustment. The T.V. cable still needs connection for proper transmission shifting, but the constant-pressure valvebody provides more freedom when setting part throttle shift points. Line pressure is fixed with no chance of encountering a low line-pressure condition, and the shift characteristics are greatly improved. TCI sells these separately if you want to install one in your own transmission.
While we had the transmission out, it was a good time to replace the mount with a polyurethane piece from Energy Suspension. Part number 4.1124 netted the Energy Suspension motor and transmission-mount set, which fits '84-'95 5.0L Mustangs. Fox-body engine mounts are notorious for cracking and separating once the mileage starts adding up, so we replaced those as well. The Hyperflex performance polyurethane that Energy Suspension uses lasts far longer than rubber, handles more horsepower, and is more resistant to road salt, oil, and other contaminants that can wither factory rubber bushings.
While we weren't able to get to the track to see what kind of improvement the new TCI transmission and converter produced, we have driven it a bit on the street, and we can tell you the results are encouraging. Shifts are crisp, and the converter now flashes the engine rpm to about 2,500, which gets us into the nitrous oxide much quicker than before.
We can't wait to burn some rubber.