Sport Compact Car Mag. wrote:
Project SOHC Dodge Neon: Part 2
Basic engine mods
By Mike Kojima
In our first installment of Project Neon, we tweaked the suspension of our underrated underdog. Now we're turning our efforts to the underachieving SOHC engine. As we said before, we didn't start with the DOHC Neon, because the SOHC Neon is more common. Besides, we already had one.
The wimpy SOHC 16-valve engine is full of promise. In stock form however, the engine just plain sucks, bleating out an uninspired 110 hp at 5600 rpm with a limp-wristed 109 lb-ft of torque at 4400 rpm. Yawn City compared with the high revs and intense specific outputs of Japanese wonder engines.Instruments
Our base model Neon has no gauges to speak of, not even a tachometer. Autometer came to our aid with its excellent aluminum-bodied Ultralite line of gauges. The big 5-inch Monster Tach we mounted on the left corner of our dash screams rice boy, but its size and placement are both very functional. The tach features a shift light and a peak rpm memory feature, which means the shift light can be set at two different points depending on the gear selected. This allows you to target your optimum shift point in different gears.
The temperature and oil pressure gauges fit into an Autometer A-pillar pod designed for the Neon. The gauges are electro-mechanical. They use special sending units on the engine with wires sending the signal through the firewall to the gauge. This gives the accuracy of a good mechanical gauge without the risk of running fragile water temp or oil lines into the cabin.Exhaust
Research on http://www.neons.org
proves informative. We found CNNP Racing and ordered a CNNP exhaust system, which is a low-restriction, stainless-steel chambered muffler with dual polished stainless tips. The Neon is blessed with mandrel-bent 2.25-inch tubing from the factory--plenty big enough for major power mods. The stock muffler is lame, however. Which is why the CNNP exhaust is simply a replacement Dynomax muffler from a V8 Camaro with the stock 2.25-inch tubing for the rest of the system.
Installing the muffler was easy, but it did require a trip to our local muffler shop to weld the muffler in place.
The results are worth the effort. The muffler pushed our peak power up to 112 hp, creating a max gain of 5.4 hp at 6400 rpm. Torque is boosted to 113 lb-ft at 4400 rpm. Plus the new muffler produced a power gain from 2500 rpm on up--impressive for a muffler on a completely stock engine. The exhaust also has a pleasant, deep-pitched note and the dual tips have a subtle sleeper look.Oil Pan
The stock Neon oil pan is a joke. No baffles to prevent the oil pump from sucking air during hard corners, no windage tray to help with oil return and reduce windage losses. We've read that a few Neons with stiff suspensions, sticky tires and stock oil pans have succumbed to oil pressure loss and bearing failure under extended hard cornering. The stock pan is also made of brittle cast aluminum. Like we said, lame. To remedy this, we contacted Moroso for one of its racing oil pans.
The Moroso oil pan has an elaborate baffle system with swinging trap doors for maximum oil control. It also has a full windage tray to better strip oil off of the crank.
A 6-quart capacity--2 quarts more than stock--ensure a continuous supply of fresh oil, and solid billet rails ensure the pan's sealing rails won't warp. The pan is fabricated from thick 6061-aluminum plate, which will bend, not shatter, under hard impacts. The pan also features bungs for turbo oil return and oil temp gauges, which may come in handy.Cold Air Intake
Next up is a cold air intake from AEM. In reality, it's a semi-cold air intake because it still picks up air from the engine compartment, although from a lower and thereby cooler part of the compartment.
The Neon didn't respond as well to the intake as most of our other project cars have, indicating other restrictions within the engine. The AEM intake did get us 2 more hp, pumping out 114 hp at 5800 rpm. Torque is up to 115 lb-ft at 5300 rpm. No power is lost anywhere in the powerband, making this a worthwhile, low-budget mod. The AEM cold air intake improves the engine's sound somewhat, but the engine's note is still flat and blatty.Underdrive Pulleys
Our next bolt-on mod is Unorthodox Racing's underdrive crank pulley. Underdrive pulleys work by reducing the drive ratio and thus the parasitic loss caused by the alternator, water pump, power steering pump and air conditioning pump. The Unorthodox unit is a work of art--CNC-machined from solid billet aluminum and cored out to remove every last bit of weight. The pulley section can be easily removed from the hub and a new, smaller pulley, just for the alternator and water pump, can be bolted in place. This is perfect for drag racing and other short duration events. For now, all our testing is done with the street configuration with all accessories functional. We plan to test the race set-up later.
The pulleys give us another 2 hp, moving us up to 116 hp at 5800 rpm, with a maximum gain of 4.7 hp at 6600 rpm. Torque is up to 117 lb-ft at 4500 rpm. The pulleys also supply a nice gain across the entire powerband.Tuned ECU
Our next mod was a Mopar Performance ECU. CNNP's Nemo Foss suggest we use the ECU from the more potent DOHC engine because it had more spark advance and gave a richer mixture on the top end than the Mopar Performance SOHC ECU. Foss says the richer mixture might hurt high-rpm power at our present level, but it might help us later as we get more into the engine. This is because the speed density Neon ECU does not compensate enough for the airflow changes our mods will create.
The Mopar Performance ECU performs quite well. In fact, it's giving us greater gains than any single mod to this point, a whopping 6.1 hp at 4300 rpm and a big gain in peak torque, upping the total to 122 lb-ft at 4300 rpm. Just as Foss predicted, we did lose some power past the power peak, the most being 6.4 hp at 6600 rpm. The power loss isn't significant because the car won't be revved this high in its current state of tune.
Other benefits? Throttle response is snappier and the car is more eager to rev. Although we didn't gain a single peak hp, we gained considerable power under the curve.Header and Catalyst
The Neon's stock exhaust manifold is laughable. Its small diameter, stubby runners dump into a close-coupled cat through a restrictive collector. It's a good set-up for reducing both cold-start emissions and horsepower.
We acquired a header from Kirk Racing, which features mild steel construction and long, 1.5-inch diameter runners with a straight flow path. The design should provide good flow for more top-end power with the long runners keeping the bottom-end power reasonable.
Since we believe in keeping our project cars as clean as possible, we bolted a Random Technology high-flow cat to the Kirk header. The cat features a short honeycomb with a higher concentration of platinum and palladium, the catalyst materials responsible for scrubbing pollutants. The richer catalyst content allows the use of a lower backpressure, short honeycomb.
The combination proved potent, boosting our engine to a respectable 122.5 hp at 5600 rpm with a maximum gain of 8 hp at 6500 rpm. The power gain is all in the fat part of the power band from 4400 rpm on up. Torque increased to 123 lb-ft at 4700 rpm.
The Kirk header has bungs for both our front and rear O2 sensors. However, if the rear O2 sensor is hooked up into the header, it'll activate the OBD-II system, which triggers the check engine light. This doesn't affect the engine's performance, but may cause problems with an emissions test. We recommend relocating the rear O2 sensor just behind the cat to keep the OBD-II system happy.Big Bore Throttle Body
Even with the header, the exhaust note was still blatty. This indicates there's still a major restriction somewhere in the intake or exhaust tract. We figured it to be the Neon's miniscule 51.7mm throttle plate, which has an odd venturi in the throttle body itself, constricting the flow area to 48mm. There's power to be gained.
We sent our throttle body to RC Engineering with instructions to open it up as far as possible. RC filled the evaporative canister purge port with aluminum-filled epoxy so the throttle bore could be lathed and honed to 57.4mm. The venturi was then machined out so the throttle body tapered from 57.4mm to 60 mm at the hose bib. This made a huge difference in the throttle body's throat area. RC then redrilled the evaporative purge passage, relocating it slightly outboard.
When installing the throttle body, we had to port match our plastic intake manifold with a Dremel tool and sanding drum; we stuffed the manifold plenum with rags to prevent chips from falling into the inside of the manifold. We also ported the manifold to the furthest edge of the gasket-sealing surface, which is why we don't recommend going any larger in the throttle body bore than we did.
The RC throttle body produces a large gain in power bringing us to 125 hp at 5700 rpm. Maximum power gain is 5 hp at 6300 rpm. Torque is up to 127 lb-ft at 4700 rpm. The power gains span a broad range, starting as low as 2500 rpm. The engine also makes good use of the extra fuel provided by the DOHC ECU.
The RC throttle body also changed our engine's sound. The blatty domestic rental car sound is gone, replaced by a deep, powerful roar, much like a Nissan SR20DE.Adjustable Cam Timing Gear
Many SOHC Neon owners say retarding the camshaft with an adjustable cam timing gear as much as 4 degrees makes a large difference. Eager to try this, we installed an AEM adjustable timing gear, which has a large engagement area for less likelihood of slipping and a venier scale for easy accurate adjustment.
On the dyno, our engine didn't match the Internet predictions. In fact, we lost power across the board. After a few dyno pulls, we determine 2 degrees of cam advance is best for all around area under the useable power curve. Our peak power is now slightly up to 126 hp at 5700 rpm with peak torque up to 128 lb-ft at 4300 rpm.
So far, we're pleased with the engine mods. We've gained a total of 17 wheel hp above stock and picked up 20 lb-ft of torque, all without losing a bit of bottom-end power. Those are wide, fat and useable power gains. Now, near-stock Civics are no longer feared and stock Civic Sis and Sentra SE-Rs can be given a run for their money.
But we've just scratched the surface of this engine's potential. We plan to go quite a bit further in Part 3 in the the quest to make the SOHC Neon a respectable world-class performance sport compact.Last-Minute
Chassis Tweakshortly after finishing the Project Neon installment on suspension tuning, one last package lands on our doorstep. It's the TTI Racing lower control arm brace we hoped to include in the December story. Better late than never. The Neon's front lower control arms bolt to a large crossmember. Unfortunately, like many front-wheel-drive cars, the mounting points are cantilevered off into space, so the crossmember flexes under hard cornering loads. This flex can cause changes in the toe setting of the front wheels resulting in irregular handling.
The TTI brace is made of light, stiff, 6061 T6 aircraft aluminum and is elaborately CNC-waterjet cut. The brace is manufactured in two pieces, bolted together with spacers for increased stiffness. It also ties the mounting points of the lower control arm together for much better lateral support, reducing flex of this area.
After installing the brace, turn-in improved because the brace prevents flex-induced toe-in under side load. If you're serious about autocrossing or road racing, the such a brace is essential.