Project Eclipse GSX Part Four
PHOTOGRAPHY: LES BIDRAWN, KEITH BUGLEVVICZ
We Continue or Quest for Elusive Extra Boost
Our Project Eclipse has come a long way since we first got the car back
in May of last year. Our first upgrade was to the suspension and throttle
response. The suspension improvements-four Eibach springs and four Koni
adjustable struts-worked like a charm, calming the sometimes-wallowy ride
of the Eclipse. To fill in the vast, vacant wheel wells, we added 18-inch
Kosei Seneca wheels and Dunlop SP9000 tires. The engine upgrades consisted
of a cat back exhaust, an intake and a better intercooler pipe, and worked
surprisingly well to give the Eclipse a measured gain of 32 hp. Next, we
added an Apex electronic boost controller and AFC fuel computer in a quest
for more boost. They helped, but we were limited by, the inefficiencies
in the stock turbo. We took care of that with a new turbo that had been
thoroughly massaged by Turbonetics. The improvement was drastic.
The cliché says a chain is only a strong as its weakest link, and that was the case in our Eclipse's exhaust system. The stock turbo outlet had been ported by Road/Race Engineering when the new turbo was installed (see "Project Eclipse", March 1998). We wanted to find out how much of a difference installing a full three-inch exhaust system would make on the car, however. There were few problems on the intake side, with a free-flowing air filter, blockage-free intake pipe and a round (instead of kinked and flattened) intercooler-to-throttle body pipe. However, the engine couldn't quite get the exhaust out properly because of the puny catalyst inlet and outlet, and the small pre-cat half of the exhaust system.
HRC offers an excellent selection of Eclipse performance parts, and their new 3-inch downpipe caught our eye; a beautifully crafted stainless steel piece with nice straight welds, a built-in flex joint and all fittings and fasteners needed to get the job done. The catalytic converter was from Random Technology and features a 3-inch inlet and outlet. This contrasted with the stock cat, which actually necked down a little from the stock 2.25-inch pipe, causing a major flow restriction. The idea behind the HRC system was it should be used to modify an existing 3-inch cat-back system. In other words, you have to cut off part of the existing performance exhaust system on your Eclipse and weld on a new flange to use the HRC system; something of an advanced procedure. Most cat-back exhaust systems for the Eclipse start out at 2.5-inches so this is the only way a 3inch downpipe and cat can be added. To do it properly, a good lift, saw and welding tools are needed. In other words, take it to a professional.
Once again, we utilized the talents of the technicians at Road/Race Engineering in Huntington Beach, Calif., for the installation. Installation of the new pipe appeared to be straightforward ... at first. The three-inch downpipe was a tight fit, and only after some serious grunting, groaning and a series of words unprintable here did we finally get the pipe in place. The fault didn't lie with the downpipe itself; there just isn't a lot of room to work in the Eclipse's engine compartment. Installation necessitated removing all the heat shielding from around the turbo, and removing the radiator fan as well for extra clearance. The stock downpipe was extracted as one piece from the car, and was relatively simple to remove. The HRC piece, on the other hand, proved difficult. The stock cast iron collector South of the turbine is physically much smaller than the HRC piece, and does not incorporate the long external waste gate runner the HRC pipe does. As a result, getting the HRC pipe to fit required a little extra effort. HRC is aware of the tightness of the compartment, but aside from supplying a special tapered bolt to clear one of the tightest spots and some hints on getting their pipe in, there is little they can do.
The second part of the system proved to be more challenging than the
first. We had to cut off a considerable length of pipe to get to the three-inch
portion. This caused a cascade of problems. Note the dogleg bend in front
of the resonator; this had to be custom fabricated later.
Attaching the new catalyst to the existing exhaust system was supposed to be straightforward. The flange from the old system would be cut off, the new flange welded on, and the whole shebang would just bolt right together. it didn't quite happen that way. Everything seemed to be going smoothly until we realized the combined length of the HP( pipe and catalyst was too short. Once again this had little to do with the HRC 'tern and more with the exhaust system we already had on the car The cat-back exhaust we used on the car didn't flare out to its full 3-inch diameter until about 2 feet past the catalyst, which was where we made our cut. This extra length was too far for the HRC piece to span, eve with the long pipes on the ends of the Random Technology cat. So, we had to improvise. like any good tuner shop, Road/Race had lots of extra parts on hand. Among them was a sizable length of 3-inch steel tubing that was easily cannibalized for exhaust system duty. We also decided to add a 3-inch resonator to take the place of the one we had cut off the cat-back system (since the car is often driven long distances, a droning exhaust was the last thing we wanted). Mike Welch carefully measured the length needed and cut off the piece needed to make the system fit. Once again, we seemed to be on track until another problem reared its head.
Although the extra length of pipe and the new resonator were fine length-wise, they just weren't lining up with the catalyst. The piece we had cut off incorporated a small dogleg bend. The bend compensated for difference of about a half inch in our modified system.
Since no amount of straining would bring the two together, Mike again came to the rescue by cleverly cutting the short length of pipe in front of the resonator. He was then able to line up the two pieces at last. Mike also cut a new hole for the stock post-cat oxygen sensor, keeping the OBDII system happy. Once the pieces were finally cut to fit, they were spot welded in place, and finally seam welded.
Despite the difficulties, the Frankenstein exhaust system looked terrific under the car. The extra welds and bends did nothing dynamically to restrict flow, and we now truly had a 3-inch "turbo-to-tip" exhaust system. The car now sports a deeper, richer exhaust note at idle that turns into a loud, angry blat at full throttle. We should point out that the exhaust does occasionally scrape, but only over high-centered clearances that would challenge almost any lowered vehicle.
The seat-of-the pants results were pretty good. Although the car didn't need FAA certification, it certainly had better throttle response, along with better turbo spool up, which was mainly what we were looking for The differences in top-end power felt incremental at best, though, with no immediately noticeable difference at the high end of the tach. What was immediately apparent was that the system was flowing a lot more air.
How could we tell? A blast to redline on a cold day would cause the
fuel cut to step in after the computer noticed the injectors hitting nearly
100 percent duty cycle. After a few of these incidents, the check engine
light came on as well. Since this increased fuel and air flow didn't seem
to be accompanied by a substantial boost in high-end power, we theorized
that the computer was over-fueling the car. To keep the engine safe from
detonation, the computer was going dead rich, too rich to make any more
power. The other hint that this could be the case was the blue faces of
that followed the Eclipse in traffic raw gas smell was a little strong.
Carefully fiddling with the Apex AFC, we dialed the air flow meter input back four percent across the entire range (by simply turning each knob back four ticks). This dramatically improved power, throttle response, odor, and caused the check engine light to go back off. We were hesitant to tune any further, though, since we had no Exhaust Gas Temperature (EGT) gauge to see how our tuning was going (exhaust gas temperature is a good indicator of fuel mixture.)
Cold mornings still brought the injectors close to 100 percent, and we were eager to try more boost, so we made a call to RC Engineering in Torrance, California, for a set of new 550-cc injectors. RC Engineering is one of the best-known names in fuel injection technology. Its injectors are all flow matched so each injector in a set flows as close to the same as is possible. in an unusual twist, Russ Collins (the "RC" in "RC" Engineering) does not concentrate as much on fuel atomization as one would think. We all know what we think an injector spray should look like-a fine mist that sprays evenly from the tip of the injector. However, Russ showed us an injector equivalent to those provided for our Eclipse on his custom strobe-light-equipped spray observation station.
What we saw was surprising ... no light mist, but a steady stream of
fuel (well, test liquid, but you get the idea) that would shoot directly
into the combustion chamber. Russ says that the atomization takes place
in the turbulent environment of the combustion chamber, and that it isn't
necessary for the injector to do the job. The narrow stream is less likely
to condense on the walls of the intake port, making the fuel mixture more
Installation of the fuel injectors was another reasonably straightforward procedure. Because it involved working with raw gasoline, it was a good idea to disconnect the battery to prevent any sparks. The entire fuel rail was removed, the new injectors were put in place, and the rail was popped on. Well, almost. Because the RC injectors have a slightly different connector location, the stock Mitsubishi rail had to be trimmed slightly. Simply a matter of grinding off some excess metal on the rail around the plug for each injector proved to be minor surgery.
With bigger injectors, the stock fuel pump would not be up to the job of providing adequate fuel pressure, so Road/Race also installed a larger Denso fuel pump.
The fuel pump was an in-tank unit, which meant removing the rear seat
to get at the access hole on top of the tank. Once the pressure was relieved
from the system and all hoses and connectors were removed, the large plastic
ring holding the fuel pump in place was removed. The pump was removed as
an assembly with the float for the fuel gauge. The pump itself was a metal
cylinder about 4 in. long. The Denso replacement unit was substantially
larger, and required a bit of modification to get onto the stock bracket.
As simple as this technique seems, Mike was quick to caution the inexperienced not to try it at home. it takes a great deal of finesse and practice to get the procedure down right one wrong move and a big piece of metal could fall into the turbo, with disastrous results. The safe way to do it is to remove the manifold altogether.
Once the hole for the sensor probe was drilled, it was relatively simple to route the lines to the gauge, which we mounted on the driver's side A-pillar next to the boost gauge. mike tells us that the exhaust temperature should be 900 degrees Celsius at full throttle when everything is operating smoothly. Getting the temperature to that level involved tuning our gas flow with the Apex AFC fuel computer This procedure takes a while, and can be disastrous if done wrong. If in doubt leave it to professional tuners like those at Road/Race.
Initially we rough-tuned the car to run smoothly, and keep the exhaust conservatively cool. Tuned this way, the car made the same power it did before we did all this work. At the time we went to press, Road/Race was in the process of tuning it more precisely in the hopes of getting better power results. As we have observed before, the stock computer is getting very conservative about fuel and timing. Though you can tune this out somewhat with the AFC , you are only adjusting the air flow meter input to the computer, not adjusting the output. To really get things right, the ECU has to be re-programmed to remove the conservative fuel and timing maps. We plan to have this done, but in the mean time, we want to see exactly how well the engine can be tuned with the AFC. With the AFC tuned conservatively, the HRC downpipe and cat and the bigger injectors have only gained us responsiveness and status in the parts hanger's club. The tuning step will be critical to making these mods worthwhile. The results of the tuning, however, will have to wait until the next installment.