Story and photos by TOM HAND. Copyright © 1989 Mopar Action. Used by permission. First printed in Mopar Action
Most Mopar fans are convinced that performance stopped in 1971 with the death of the Hemi. I'm not one of those, but I admit the new breed of cars from Chrysler has to be attacked from a slightly different but somewhat similar angle. I've grown up with a couple of 340 4-speed cars, and I've found there are a lot of little tricks that add up to a big performance increase, even on the new front-wheel-drive cars.
Chrysler has stayed with the FWD platform since the first K-cars in 1981, and it didn't appear that they were going back to the rear-wheel-drive high performance cars of the '60s. I've always enjoyed the sleeper cars, such as 340 Darts and Dusters, so I chose as my '80s sleeper a 1984 Dodge 600 with a turbocharged 2.2-liter (135 cubic inch) engine and an automatic transmission.
A quick look at the Dodge reveals air conditioning, tilt wheel, six-speaker AM/FM cassette and a rear window defroster. The Dodge 600 weighs about 2680 pounds, the turbocharged 2.2 is rated at 142 hp, and the automatic transmission has a gear ratio of 3.02-to-1. I chose as a realistic goal a 14-second elapsed time and 90 mph in the quarter mile.
Before any major power improvements were undertaken, I thought it wise to inspect the lower end of the engine and at the same time install a higher volume oil pump. After the oil pump and pan were in, the cylinder head was pulled, cleaned up and reinstalled with new head bolts.
To check out the car and establish a baseline, I ran it at the strip until consistent results were achieved. These first runs were exactly as expected and comparable to the original Chrysler advertised figures. The slowest run was a 17.14 at 79.6 mph and the quickest was a 16.85 at 80.8 mph. Not particularly exciting but certainly promising, as the horsepower-to-weight calculations showed the engine to be producing at least 127 hp. (Some errors can be expected in the calculated values, compared with the Chrysler rating of 142 hp, because the standard tables I used aren't as accurate when working with front-wheel-drive cars.)
If anyone’s modification plan, the first step should be the easiest and most cost effective. In the case of “computer controlled” engines, changing the chip (or in Chrysler’s case, the Logic Module) will produce a substantial gain in horsepower. Mopar Performance sells a Logic Module for the 1984 turbos that installs in minutes, provides a more aggressive spark timing curve, a richer fuel mixture and higher rpm engine cutoff; and allows a boost pressure increase from 7.2 psi to about 10.0.
Owners who install this computer chip will find that 92 octane fuel is not high enough to prevent detonation. I solved this problem by mixing 100 octane low lead aviation fuel with unleaded premium. Beware of the likelihood of poisoning the oxygen sensor and the catalytic converter with large volumes of this fuel.
Drag strip elapsed times showed a great deal of improvement, with the slowest time of the day being a 16.14 at 83.5 mph and the best a 15.90 at 84.8 mph. Calculations showed the Logic Module to be worth about 18 hp. Not only was the 600 coupe's performance respectable, it could now run with automatic transmission equipped Z28s, Trans Ams and Mustangs.
After studying some basic turbocharger theory, I decided a reduction of exhaust backpressure and a “stream lining" of the air intake system would give some more performance gains.
I bought some 2 1/2-inch diameter 409 series stainless steel tubing, and a custom exhaust shop bent a new system for me that used a stainless steel Sonic Turbo muffler and had no provisions for a catalytic converter. Without the converter, a system like this has to be considered "strictly off-road," so applicable laws should be checked before using it on the street.
I removed the turbocharger compressor inlet elbow, the air cleaner hose-to-throttle body adapter and the air cleaner cover, eliminated all the casting flash and polished them internally. Installation was completed with a K&N air filter element.
The intake modifications I performed were similar to what a person would do to an intake manifold on a V8 engine. However, I had an easier time since most of my components were plastic.
A road test revealed a remarkable difference in drivability, and it was obvious the drag strip times would correlate. The strip times confirmed this: a slowest time of 15.75 at 87.71 mph and a fastest of 15.65 at 88.75 mph. Horsepower calculations showed the better-breathing 2.2 was providing at least 165 hp; that's another 20 on top of the 18 added by the Logic Module and higher octane fuel.
Since my 2.2 turbocharged engine was approximately 30 percent more powerful now than it was in its stock configuration, I began to get concerned about driveline breakage. A little research educated me a bit. The older FWD transaxles had a differential mounting configuration that was not capable of sustaining wide open throttle, drag strip-style starts. I also learned that Chrysler had corrected this problem in the 1987 and newer automatic transaxles.
The third step in my quest for a 14 second FWD automatic was the hardest to complete and the most expensive. I was aware of the transaxle redesign in the 1987 and newer Chrysler turbo cars, so I limited my search to one of those. After its acquisition, I had the ring and pinion changed from the stock 3.02-to-1 ratio to a lower 3.22-to-1. The torque converter used was built to specs provided by a Chrysler torque converter expert, and I acquired a flywheel to attach this new 4-bolt converter to my existing 6-bolt crankshaft flange. (Note: '84s used a 6-bolt crank flange and 3-bolt converter; newer vehicles have an 8-bolt crank flange and 4-bolt converter.) The transaxles for 1987 and later turbocharged Chrysler cars drive through stronger axle shafts, so these too were replaced.
Installation of the new transaxle was a six-hour job that went relatively smoothly. After completion, a few trips around the block confirmed what I had hoped for. My Dodge 600 was now capable of wheelspin from a slow roll-something that was not possible before the transaxle change.
Before my next drag strip test, I installed a 3-inch air duct from below the front valance to the air box in order to provide an ample supply of cold air. I again mixed the fuel to obtain sufficient octane.
My first run surprised even me with a 15.31 at 88.9 mph. The transaxle had obviously made a great improvement in bottom end performance, because now I was fighting wheelspin. Later in the evening I had back-to-back runs of 15.17 at 90 mph, and it was obvious 14-second elapsed times were only a quicker start away. Horsepower was calculated to be about 170, an overall improvement of 43 so far.
After about 4000 miles and 50 passes at the strip, I began to notice a buzzing noise from the converter area. I pulled the transaxle and had the converter cut apart, and it's there that the damage was found. I had wiped out the thrust washer assembly that takes all the load during high stall conditions.
I settled on a new torque converter sold by Turbo-Action (as well as Mopar Performance) that has needle bearings instead of the bronze and babbitt thrust washers. It is slightly tighter than the factory unit I had installed with the heavier duty transaxle.
The new converter required a few modifications before I could install it. The early transaxle that it was designed for used an oil pump that has a drive gear with two tabs in its inside diameter, which the converter hub engages. My later-transaxle oil pump has two flats on its i.d., so I had to have a machine shop mill corresponding flats on the hub of my new converter. This converter has three mounting bolts, so the original 3-bolt flywheel was reinstalled. The Top Dead Center mark was also made more obvious (2.2s are timed through a hole in the bellhousing by a mark machined on the converter).
Back at the strip, it appeared that the tighter converter was exactly what I needed to kill some of the 2.2's low end torque. Best time of the day was a 15.05 at a slightly slower 89.0 mph. I still, however, could not get into the 14s. My only hope was to find more horsepower. My Logic Module already was running the engine with maximum boost, fuel and timing. Luckily, I stumbled across a rather devious but very intelligent auto-oriented computer head who fabricated a new chip for my existing module. This one would allow as high as 14 psi of boost; however, my stock injectors are only safe up to about 12 psi.
I set the boost at 11.5 via various tuned bleed-off orifices and went back to the strip. First run success finally arrived with a timeslip that read 14.96 at 90.0 mph. After a couple more runs, I stopped with a best time of 14.77 at 90.7 mph.
The last race for me in 1988 was our Second Annual Mopar Day at Kansas City International Raceway on October 16. The weather was good, with the temperature at 80 degrees, relative humidity at 35 percent and the barometer at 29.98. Since the new Logic Module chip would allow temporary overboost, I opened the exhaust system. (The other modules had only minimal tolerance for overboost, and opening the exhaust would consistently let the turbo spin up quicker than the wastegate could control. This generally caused the overboost condition.) This was going to be a good day to compare the performance of my 1980s FWD musclecar with the 1960s and 1970s Mopar RWD musclecars.
The initial run was an exciting 14.48 at 93.9 mph. Horsepower calculated to about 192; the new devious box combined with the open exhaust increased the power another 22 hp, but lowering the boost put it back to a safer 182. Subsequent runs were all between 14.47 and 14.51. As the day progressed, it appeared that my injectors were not supplying the fuel, so I lowered the boost slightly and dialed the car in on a 14.60, and the mph stabilized at 92.0. I let a very good (and consistent) friend drive the 600 in the bracket race, and he piloted it to a runner up finish in the 13.00 to 14.99 class. Who would have thought that an '84 Dodge 600 four-cylinder would be at the strip, much less competing in the same class with just about every other factory Mopar musclecar ever made?
After the 14.40s, I finally was as far as I figured I could get with my existing non-intercooled 2.2 setup. However, I couldn't stop at 93 or 94 mph. A few more calculations showed 98 mph was in reach, with only 200 hp needed to get there.
My injectors would not support the 200 hp attempt, and without nitrous oxide I knew I was at the end of my road. But luck would again go my way, as I was able to purchase a complete intercooler manifold, intercooler and all the associated hardware needed to adapt it to my vehicle.
The first step was to disassemble my old hardware. While the head was off. I checked and cleaned the valves and installed new valve seats. I also drilled and tapped the block for the new 11 mm head bolts that give the much-needed clamping power.
The new intake I installed was a two-piece tuned unit that changed the torque peak to a lower rpm level just exactly what my automatic equipped 600 needed. While it was off the car, I also matched the two halves of the intake to the gasket, therefore matching the runners, much like one would match the intake to the heads on aV8.
Surprisingly, everything bolted on my 1984 600 K-body, even though it was intended for an'87 G-body (Daytona). I did, however, have a number of items that needed to be modified and/or removed.
Initially, the new throttle body was a big problem. However, my advisor in this new project engineered an aluminum sleeve that let my old 1984 motor-driven "valve" idle motor fit onto the new throttle body, which originally used a motor that pushed a plunger in and out of the orifice in the body.
Right after I thought things were solved with the throttle body-idle motor problem, I realized the hood would not shut, as the water drain trough sits on top of the new tuned intake. I left the room as my dad used his metal cutters to trim off the offending sheetmetal. I guess this is how people feel when they cut holes in their hoods to clear blowers and carburetors.
My old radiator had two additional parts that the new intercooler radiator assembly didn't. One was a hose nipple that was the return for the heater hose, and the second was a female pipe fitting that accepted the radiator fan thermostat switch-sensor. I bought a 4 inch long piece of 11/2 inch diameter pipe and welded on the correct size nipple for the heater hose and the female pipe fitting to accept the thermostat switch-sensor. I had to buy an '87 Turbo TI Daytona lower radiator hose and use the smaller diameter section of it on one side of my new 11/a inch adapter. Then I cut my ~old hose and attached it to the other side of the adapter.
Software problems always surface with computerized items, and this project was no exception. However, my devious but auto oriented computer head friend corrected my Logic Module to feed the new high-flowing injectors and allow for the 100 degrees of (average) temp drop air that the intercooler would provide.
After some minor tuning on the throttle body to bleed more air through the idle motor assembly, I was able to achieve a respectable idle.
It's amazing how much torque this combination yields. I couldn't believe how responsive the four cylinder really felt. It sort of reminded me of a 340 automatic Dart I once had.
After a two-month proving, I was ready for the strip.
I left my exhaust hooked up and the boost set at 10 psi. I ran only 92 octane unleaded Amoco fuel. The very first run was a 14.76 at about 94 mph but with a lot of wheelspin. Before the intercooler, it took 11.5 to 12 psi and good fuel to even touch the 94 mph range.
I cranked the boost up to 12 to 12.5 psi and the times dropped to 14.40 at 96 mph. The finals runs were made with the exhaust opened, and even a Grand National was surprised with my best time of 14.14 at 98 mph. Later runs would raise the speed to 99 mph, but ET stayed around 14.20. When I calculated the horsepower. it worked out to some 200 to 205.
What's more, the times and mph reflected another resounding change-all of this from a car that started out turning 17.14 at 79 mph.
I'm always a bit skeptical when I read an article such as this on performance modifications. There are always bad things that go hand in hand with the good, and this project was no different I'll give a brief synopsis of the disadvantages I noted
The Logic Module improve power a great deal, but very high octane fuel is required. The second special module I ran the 14s with is not yet commercially available, but there are many fuel enrichment devices that could possibly achieve the same results. The Chrysler electronic system adapts to any type of fuel by using a detonation sensor to control pre-ignition, but the subsequent retardation of total advance is very noticeable in a seat-of' the-pants feel.
The new exhaust system is not any louder than the original one, but the absence of the catalytic converter makes it illegal for street use. Enough said. I still strongly feel that 13.90s at 9h mph are possible, but I'm not sure my Michelin 195/70R-14 whitewalls will supply the needed traction. Even in 95 degree weather, the intercooler allows me to run only 92 octane fuel without detonation at 12 psi boost, and this provides more than enough torque to roast the front tires. At the strip, I've been posting about a 65 percent success rate against 5.0 liter mildly modified Mustangs, and even the semi-stock Grand Nationals can't consistently beat me.
I'd have to say I'm satisfied with the 3 second decrease (l 7.14 to 14.14) and 20 mph increase in quarter mile performance. Even the fuel economy decrease from the stock 27 mpg highway/20 mpg city to the 21 highway/ 16.5 city that the car attains now isn't all that major.
I'd like to thank Stu Davis for the electronics wizardry, John Donato for the transmission information, and Bob Craighead for the adaptation guidelines. Without the help of these three, I couldn't have met and exceeded my original 14 second, 90 mph goals.
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