*photography by: the author

Relieving restriction and adding boost nets 53whp and drops our Regal GS into the 13s

Welcome to the second installment of our affordable W-body build appropriately named, Project: Sleeper Status. Rather than building an F-body, ’Vette, G8 or other modern GMs that is widely regarded as fast, we thought it better to build an unassuming grandma grocery getter that would embarrass plenty of fast cars if they didn’t bring their A-game.

As I’m sure you remember from Part 1, we’ve paired with the W-body gurus at ZZPerformance in the hopes of creating an 11-second sleeper out of our 152,000-mile 2000 Buick Regal GS without breaking the bank.

As with any project, there are multiple ways to get to the same result and while we initially considered a turbo kit for its greater potential, we ultimately shied away from the exhaust-driven snail because we wanted to keep the budget in check. This isn’t to say that the end result of our Regal is going to be dirt cheap, but the first few installments will be beyond affordable and can be replicated in stages so that the pocketbook doesn’t go up in flames.

After many conversations with W-body gurus, we decided to start our project by uncorking the choked-up L67 and adding just a bit of boost. Here’s how it transpired.

Relieving Restriction

ZZP 3800 Cold-Air Intake

First on our list was ditching the restrictive factory airbox with a free-flowing cold-air intake from ZZP. This high-quality unit features 4-inch piping with a massive 9-inch reusable K&N airfilter for the utmost in flow. The airbox seals against the back of the headlight and also features a sealed lid along with internal heat shielding to keep intake temps down and horsepower up. Like the factory airbox, the ZZP unit also has an integrated PCM tray for an OEM-like install.

Speaking of the installation; it was bonehead-easy even though it’s a universal ’98+ W-Body design that also fits the 2000 and newer Bonneville H-bodies. Beyond a tidy install, the intake gave our Regal GS a newfound voice, as even at stock boost levels, the Eaton blower could be heard quietly whining under WOT.

ZZP PCM 1.0

While we were under the hood installing the cold-air intake, we also added a ZZP PCM 1.0 ECU reflash with a preloaded 91-octane custom tune from ZZP so our Regal could make the most of our meager California pump gas.

Turn around time on the ECU is 24-hours, so from the moment we dropped the ECU in the mail until the day we got it back was no more than four days. The brief waiting period gave us some time to add the rest of our Part 1 mods.

Some of the preloaded features include a raised rev limit that gave us an additional 1000 rpm for more boost and a longer drive in each gear, along with higher and firmer shift points thanks to additional line pressure, optimized torque converter lockup tables and even 3-1 and 4-2 skip shifts. Other noteworthy additions include more ignition timing, part-and full-throttle knock-retard issue fixes, optimized air/fuel ratios, and a lower 185-degree fan activation temperature. ZZP went so far as to design a cool-down mode that activates the fan for 90-seconds after the key is turned off if the coolant temperature is above 180-degrees. The speed limiter is of course deleted, as are other nannies that throw check-engine lights (CEL) due to the catless downpipe, lower-temperature thermostat and other power-friendly features.

ZZP explained that the included tune was suitable for our current setup and would even be fine for our final modifications…nope, we’re not telling…yet. And if you doubt the quality of the tune, the AFRs might have been a little rich with the bolt-ons and stock pulley, but the addition of the smaller pulley brought the AFRs right into the sweet spot of the upper 11s.

Stainless Steel Long-Tube Headers, 3-inch Catless Downpipe, and Cat-back Exhaust

With the inlet side of our L67 uncorked, next up was the outlet side and rather than starting with the furthest point and moving back toward the motor, we swung for the fences and went for a full system. Yep, we went for the big dog stainless steel long-tube headers from ZZP and followed that up with a 3-inch catless downpipe and a matching 3-cat-back system because we’ve got big plans for this supercharged six.

Lets start with the long-tubes first; they’re widely regarded as the headers to have for an L67 thanks to precise construction and their ability to support big power. They’re constructed of 16-gauge, TIG-welded (yeah, they’re handmade) stainless steel and feature 1.75-inch primaries that are claimed to be over 2-inches longer than comparable units on the market for the ultimate exhaust scavenging. The laser and water cut flanges measure 3/8-inches for a supreme seal and the band clamps that secure the front and rear headers together and can be quickly separated for service. Other fitment highlights include a 3-inch V-band connection after the laser sharp merge; again, for easy removal and installation, along with easy access O2 sensor placement and special considerations during the design so that the dipstick and transmission bolts can be easily removed.

After spent gases leave the long-tube headers in a hurry they reach the 3-inch stainless steel downpipe that preserves velocity and is just asking for more boost. While ZZP offers both 2.5-inch and 3-inch versions with 200 cell or 400 cell catalytic converters or in our case, without any cat at all.

The stock downpipe is quite possibly one of the most restrictive portioned of the OEM exhaust system, save for the stock from manifold. The stock downpipe at it’s peak only has an inside diameter of roughly 2-inches, but that worsens to just 1.75-inches around the rear O2 sensor where the piping takes a sharp U-bend that robs serious power.

ZZP solves this problem with a wide-open unit that’s either 2.5-inches or in our case, 3-inches from front to back for maximum flow. It’s made from 16-gauge high-quality stainless steel tubing and like the headers, it too features laser cut flanges for a leak-free fit.

Note that since we are running an off-road downpipe, ZZP turned off the 137-141 and 420 CEL codes, otherwise an O2 simulator would need to be purchases in order to keep your CEL off.

The last piece of our high-flowing exhaust system included the ZZP single 3-inch cat-back exhaust system made specifically for the Regal GS. Like the rest of the system, it’s made from high-quality stainless steel and is a thing of beauty. It’s available with or without a resonator before the polished stainless steel Magnaflow muffler and once installed, it looks and sounds wicked.

Fitment of the entire exhaust system is factory-fresh, from the headers down to the polished exhaust tip. But we must forewarn you that the installation is time consuming and is easier if three or four people are there to help. However, once installed, the headers fit like they came from the factory and the sound of the full system is deep, raspy and unlike any L67 exhaust we’ve ever heard­–it sounds mean.

Let’s Talk Boost

Modular Pulley System and 3.4-inch Pulley

Thankfully GM blessed the L67 with a factory supercharger so that adding ample power is only some bolt-on parts away; but only after the factory press-on supercharger pulley is ditched in favor of a ZZP modular pulley system. This clever setup includes a hub, a pulley, and five Allen retaining screws that make swapping pulleys a 15-minute affair. After using the supplied puller to remove the stock pulley, it then doubles as a press to install the mounting hub. Once the hub is in place, simply remove the five Allen-screws to swap pulleys. Per ZZP’s advice, we opted for a 3.4-inch pulley to increase boost to moderate levels.

A keen eye will notice that the ZZP pulley features an 8-rib design but that only 6 of the ribs are utilized on the stock belt. This is done so that if someone decides to step up to the high-boost 8-rib setup, they don’t have to buy all new pulleys.

Supporting Mods

Since we’ve got big plans in story, we wanted to build a solid foundation for high boost and 300+ whp so we continued with a few more ZZP supporting mods. This included a lower-temperature 180-degree thermostat, colder Autolite 104 sparkplugs, ZZP 10.3mm sparkplug wires and a ZZP Alternator Voltage Booster. Some might argue that a few of these are unnecessary, but as far as we’re concerned, all of these supporting piece are cheap insurance.

Dyno Time

To see what Round 1 of our modifications was worth in the way of power, we again paid a visit to the West Coast horsepower experts at BRG Racing & Dyno Services in Pacheco, California for some dyno time on their in-house Mustang Dyno. Thankfully our Regal GS was under the watchful eye of Casey Cager and his crew of automotive experts.

Rather than test all of the mods at once, we decided to leave the stock pulley in place and dyno just the bolt-ons first. Then, we swapped for the smaller pulley to see what the additional boost was worth in the way of power.

Before diving into the numbers, let us add that it was difficult to get apples-to-apples runs between the modified Regal and the stock baseline because the ECU tuning made the car far more apt to downshift rather than holding a gear low enough in the powerband to mimic the baseline pulls. In other words, on the dyno, the ECU would not let the car low enough to hit its peak torque without downshifting. As such, the peak torque figures with the tuned car are artificially low, but we hope to remedy this situation with help from ZZP for the future installments. Nonetheless, a closer look at the dyno graphs makes it easy to predict where the torque peak would lie with the tuned Regal had we been able to lock it in gear.

But enough with the details; how’d it do? With the long-tubes, downpipe, cat-back, cold-air intake and ZZP tune in place, we hit the rollers to the tune of 243hp and 315 lb-ft at the wheels compared to our baseline figures of 215hp and 360 lb-ft at the wheels. Total power gains for just the bolt-ons registered at 28hp at with an artificial loss of 45 lb-ft. We gained nearly 30whp from just relieving restriction and optimizing the tune, which if you ask us, isn’t bad–but it was only setting the scene for what was to come.

More Boost

After gaining almost 30hp by uncorking the L67 we decided a little more boost was the next best thing. According to the inaccurate stock boost gauge, the stock car would hit roughly 9psi. The addition of the full exhaust, intake and tune relieved restriction so much that it dropped boost to just 7.5psi. Remember, boost is restriction and relieving the bottleneck always drops boost, but again, we lowered boost and still picked up 30whp.

Next came the ZZP modular pulley system with a 3.4-inch pulley that raised boost by 3psi to almost 10.5 psi. The result? Another 25hp and 3lb-ft at the wheels over the bolt-on dyno graphs for new peak numbers of 268hp and 318 lb-ft at the wheels. Compared to the original baseline, we’ve already added 53hp at the wheels with simple bolt-ons and a little more boost!

But dynos don’t mean much without track results, so we headed for the promised land.

Track Testing

On a cool Fall day we paid a visit to the ever-fast Sacramento Raceway for some track thrashing. Some of you might remember our best stock pass of 14.68 @ 92.55 mph with a best short time of 2.24 using the traction control with street tires.

This time we had an additional 53hp at the wheels, an additional 1000rpm to play with, and sticky Mickey Thompson Drag Radials–we were ready to get after it.

Despite our best attempts at traction, the ol’ Regal would still turn the Mickeys into smoke unless we were careful. Our best short time of the day was a marginally better 2.20. Next outing we’re going to play with launch technique and see if leaving it in First gear and pedaling it helps.

But who needs great short times when you can make it back on the big end? And make it back we did, as the Regal ran a succession of 14.20s and even dropped into the 14.15s before we ditched the driver’s side headlight, aired down the Mickey Thompsons even more and proceeded to run a 13.97 @ 99.5 mph! For those counting, that’s .71-seconds and 7 mph faster than our baseline!

Once the Regal was hooked up and moving, acceleration was far stronger than stock, especially in Third gear where the stock car would start to nose over, now the Regal is running fender to fender with Mustangs and other unsuspecting victims.

We would have gone for a better pass, but noticed a puddle of oil underneath the ol’ Regal. After countless high-rpm dyno pulls and track passes, the 152,000-mile front seal gave up the ghost. Don’t worry though, we’re going to crawl under there and get her all patched up before we add the next round of mods in search of that ever-elusive 11-second ET. But for now, we’ve never been so proud of a 13-second ET and the looks on the many drivers we motored by on the back-half was priceless. Stay tuned, we’re just getting started!

Once again, we paid a visit to BRG Racing & Dyno Services for their help with Project: Sleeper Status.

The ZZ Performance (ZZP) long-tuber headers feature full stainless steel construction with thick, water-and laser-cut flanges for a leak-free fit, and 1.75-inch primaries and a 3-inch collector for serious power production.

Have a look at one of the restrictive stock manifolds compared to the ZZP long-tube header. It’s clear which one was made for big power.

A ZZP stainless steel 3-inch catless downpipe was the chose midpipe for big power production and an OEM-like fit.

The area near the rear O2 sensor on the stock downpipe necks down to just 1.75-inches–talk about a restriction. Now look at the ZZP unit, it’s 3-inches in diameter from start to end.

A ZZP reflashed ECU was commissioned to handle the tuning duties and it not only dials in the correct timing and air/fuel ratios, but in improves transmission action, raises the rev limit, lowers knock-retard and much more.

A smaller ZZP 3.4-inch pulley joined the party for more boost and more power. Note how much smaller it is than the stock unit.

The ZZP modular pulley system comes with a puller/press tool to remove the press-on stock pulley and install the ZZP hub that makes swapping pulleys a five-bolt affair.

Note the aforementioned five Allen screws that make swapping pulleys a cinch. Note that we’re still utilizing the stock six-rib setup, but should we upgrade to the eight-rib system, we won’t need pulleys.

You’ll have to read the full story for an explanation of the artificially low torque figures of the tuned Regal, but we began the dyno thrashing with the stock baseline against the bolt-ons and stock pulley. The intake, ECU and full exhaust relieved restriction and dropped boost from a figure of just over 9 psi to only 7.5 psi. Despite the drop in boost, power increased by 28hp at the wheels.

Next came the ZZP modular pulley system with a 3.4-inch pulley that raised boost by 3psi to almost 10.5 psi. This added another 25hp and 3lb-ft at the wheels over the bolt-on dyno graphs for new peak numbers of 268hp and 318 lb-ft at the wheels.

Compared to the original baseline, the bolt-ons and smaller pulley have added 53hp at the wheels!

Enough dyno talk; lets go racing! Our best stock pass was 14.68 @ 92.55 mph with a 2.24 60-ft. The additional power made traction difficult despite the Mickey Thompson Drag Radials so despite a similar 2.20 60-ft, the modified Regal pulled like a big dog on the top end for a best pass of 13.97 @ 99.5 mph! That’s .71-seconds and 7 mph faster than our baseline!

Rick Seitz

Rick Seitz is the owner and founder of AutoCentric Media, and has a true love and passion for all vehicles; GM, Ford, Dodge, imports, trucks — you name it! When he isn’t clacking away on his keyboard, he’s building, tuning, driving or testing his current crop of personal projects!