initial inclination was to open up the parts catalog and order an off the
shelf torque converter. But after hearing some horror stories about such
converters not performing well and even falling apart, we decided to get
some recommendations. We noticed a few cars at our local track with Emerald
Torque Converters decals, and considering they were local (Walnut Creek,
CA) we decided to give them a call.
Emerald asked us details about our car, gearing, and engine, and based on
our responses they suggested a 2800 stall non-lockup converter. The cool
thing about Emerald is that their converters are built to the customers
specific requirements, they don't try to fit you with a generic converter.
We spent a morning at Emerald's shop installing the
converter, and the following weekend we took the car out to the strip.
Our initial impressions could be summed up with a huge grin on our face.
A stock 5.0 engine is torquey as it is...throw in a converter and you may
as well buy stock in Goodyear. The stock 225-60-15 tires are simply ill
suited for the immediate torque shock. With the stock converter the torque
builds gradually and max torque doesn't hit the tires until the car is in
motion. With the new converter, stabbing the throttle just halfway results
in tire spin. It took a few stoplights to teach ourselves to leave softly.
Other than the feeling we've added 50 more lb.ft. of torque to the motor,
the converter has no major side effects in terms of driveability. Because
this converter does not lockup there is about 200-300 rpm worth of slippage
in drive and overdrive. With the stock converter the engine at 65 mph would
turn at approximately 2200 rpm, we're now noticing it turns closer to 2500
rpm. While you'd expect some loss in fuel economy due to the increased rpm,
our mileage in fact has remained exactly the same. We figure this is because
we're not having to downshift from OD to D as often in order to accelerate
and pass. The non-lockup converter reacts so fast in overdrive that there
is very little need to downshift at freeway speeds.
One of the
side effects of a higher stall converter is dampening of the shifts. With
the stock converter and a TransGo shift kit we could bark the tires during
1-2 and 2-3 upshifts. With the new converter the transmission still shifts
fast, but the shifts are softer than grandmas Cadillac.
contacted TransGo to see if there was a valve body modification which
would bring back some of the hard shifting we were used to. They recommended
we upgrade the 1-2 valve with the "blue" spring (included in
their shift kit). So we dropped the pan and valve body and swapped the
green spring for the blue one. This resulted in bringing back the 1-2
bark at wide open throttle. We also installed a transmission fluid cooler,
since the higher stall and slippage generate more heat in the transmission,
which can also lead to soft shifts. If we really wanted hard shifts in
all gears, the only other solution would be to rebuild the transmission
with specific modifications to the fluid passages. We'll live with it
the 1-2 valve with the "blue" spring in the TransGo shift
kit to firm up the 1-2 shift.
stall converters generate heat, which is the enemy of automatic transmissions.
Install a fluid cooler!
the car out to Sacramento Raceway to get some objective results from the
converter upgrade. Unfortunately the weather conditions were worse that
when we had baselined the car with the stock converter. Temps were in
the high 90's, humidity was high, and barometric pressure was low (mid
29's) - about the worst conditions for racing.
Nevertheless the car gained a tenth over its best ET ([email protected]
versus [email protected]) with the stock converter. We were down 2mph, but
so were most of the other cars. We figure in better conditions there is
at least another tenth in the converter. Keep in mind, this is launching
easy on street tires, with 60 ft. times in the 2.0 range. With slicks
and a full throttle launch a couple more tenths off the ET can be expected.
(see timeslip log for
took the '88 LX to Sacramento Raceway to test out the new converter.
The car ran 13.84, a tenth faster than with the stock converter, in
very hot weather and on stock radials. There is at least another tenth
or two with cooler air and slicks.
Mladinich is the brains behind Emerald Converters. We spent a couple
hours with Gary discussing what makes Emerald Converters far superior
to any of the off the shelf brands. Gary spends a considerable amount
of time upfront ensuring the converter matches the customers stall
speed requirements. The size, number, and pitch of the vanes in the
turbine, impeller, and stator are major factors in determining the
characteristics of a stall converter. Two converters which are rated
at the same stall speed may feel and react completely different based
on how they are constructed.
Gary pointed out also how the internals of many aftermarket converters
are no stronger than stock. While they may achieve the stall speed,
the internals are not meant to handle the power and the converter
is prone to fail.
a powerful converter means having the right components and cores on
hand. Gary explained that the typical 9" and 9.5" (245mm)
converters are based on cores from GM front wheel drive 4T60 transmissions.
They are preferred because they come in eight different impeller vane
angles, and are also a good physical size for obtaining higher stall
vanes of stock and many off the shelf converters are simply
slip-fit into place. Fluid under high centrifugal force causes
the vanes to flex or bend, resulting in a loss torque transfer,
and eventual breakage or bending.
brazing (top right) is a popular feature on many converters,
but the vanes can still be flexed easily.
converters feature tig welded vanes on both the impeller and
turbine for the ultimate in strength and resistance to flex.
For high power applications Emerald offer a double bladed turbine
machining clearances within the converter can make the difference
between a poorly reacting converter and one that snaps you back
in your seat at the slightest tip of the throttle.
strengthening features include a hardened steel impeller hub,
billet front cover, anti ballooning flange (shown), and hardened
stator sprague and race.
sprague eliminator is also available for all-out race cars requiring
constant torque multiplication.
converter halves are precision welded using a robotic welder.
finished converter is checked for leaks and balanced, then shot
with the trademark Emerald green paint.
Emerald Torque Converters
2040 North Main St. # 16
Walnut Creek, CA 94596