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1987 Buick Grand National Fuel System & Exhaust Upgrades - Turbo Buick Basics

Part 2: Upgrading The '87 Grand National's Fuel System And Exhaust

Dan Foley Sep 1, 2009
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Once the boost (stock 13 psi) is cranked up on a Turbo Buick, bigger injectors are needed to prevent a lean condition. We stepped up to Racetronix 42-pound, flow-matched injectors (PN 01D030X). The stock 28-pound injectors were tired and couldn't handle the additional juice flowing from the new Walbro 340 fuel pump and "Hotwire" harness (also from Racetronix) we installed in Part 1. Since we're messing with a 20-something-year-old motor, we upgraded to the Racetronix Injector Harness (PN RX-G77-INJ-A) to replace the baked old wires and connectors.

In the last installment our willing friend, Tim Cairone, let us take his bone stock '87 Buick Grand National in a time warp back to the 80's.

By using today's technology and help from seasoned Turbo Buick experts, we'll be able to show owners of stock TRs (Turbo Regals) how to safely increase the power and driveability. For the recap, after establishing a bone-stock baseline (dyno and track testing), we tried a custom chip from Cotton's Performance for 17 psi boost and 93-octane on Tune Time Performance's dyno. The chip did its job and increased the boost from the stock 13 psi to 17 psi. Power rose from 256 to 320 lb-ft of torque and 208 to 210 rwhp (gains of 64 lb-ft and 2 hp). While dyno testing we learned of an inherent lean condition common to the Turbo Buick when cranking up the boost. We didn't want to waste the head gaskets, like many of the TBs back in the day, so we attempted to cure our lean condition with a new Walbro 340 (PN RX-G77-FPA) fuel pump and fuel pump "Hotwire" kit (PN G7-FPWHG) from Racetronix.

After speaking with nearby TB experts Jose Torres and Dan Smith (Jose Motor Sports), we replaced the stock valvesprings with mid-90's LT1 springs, at their suggestion. This taught us the first must-do's for a TB-beef up the fuel system and get rid of those wimpy valvesprings before turning up the boost. After installation we were back at Tune Time testing the new fuel system and valvesprings. This test showed us gains of 28 rwhp and 38 lb-ft of torque. We were stoked about the power gained, but disappointed to find out we still had a lean A/F (air/fuel) ratio. Tune Time's Matt Hauffe suggested the original 106,000-mile, 28-pound injectors we not up to the task. So we ordered a set of flow-matched 42-pound injectors from Racetronix. This is where we left off in Part 1, with our total power gains of 102 lb-ft of torque and 31 hp (from bone stock).

We intended to strip test from the stock baseline of 14.25 at 94.53 mph to see the ET improvement from changing the chip, fuel pump, "Hotwire" fuel pump harness, and valvesprings. However, Mother Nature wasn't having it. So we moved up to the 42-pound injectors. Right after installing the larger injectors the 3.8 Turbo was running pig rich with black smoke belching out of the tailpipes. We tried leaning out the programmable fuel parameters (a feature of the latest chip technology), but it still ran too rich. After speaking with Jack Cotton of Cotton's Performance we learned you must replace the chip with one designed for the appropriate sized injectors and injector pulse width. So our friends at Cotton's Performance burned us a new chip for the new 42-pound injectors.

The TR seemed to be running smoother and more responsive with the new chip and larger injectors. We noticed the V-6 was now seeing 19 psi of max boost (we'll need to install an adjustable boost controller soon). To play it safe we added 5 gallons of 110-octane race fuel before filling it with 93-octane pump gas. With that we made another dyno date at Tune Time just to be sure the A/F was safe enough to finally strip test. On the ride up to Toms River (30 minutes from home) Tim remarked how much stronger his car felt with the new chip and injectors. What he felt turned out to be a big torque gain. The dyno showed us an increase of 2 hp along with 47 lb-ft of torque! The A/F was slightly lean at 12.1 to 12.2. We left the A/F alone since we had the protection of the race fuel.

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From a stock baseline run of 14.25 at 94.53 mph we needed to know how much quicker the GN would go. With boost now at 19 psi (stock 13 psi), along with the host of "safe" fuel system components we expected low ETs from the additional 149 lb-ft torque and 32 rwhp. Our best ET was a respectable 13.63 at 100.55. With better brakes and a high stall converter we feel the TR could have managed low 13's. We couldn't launch with even 1 psi of boost (TRs launch better at 3-5psi). We'll be looking into upgrading the converter later on for a better launch and lower ETs.

We were counting on a huge difference at the track after gaining 32 hp and 149 lb-ft of torque from the baseline of low 14's. We mounted 26x8.5 slicks on old 1970's Vette 15x8 heavy steel wheels to ensure we would not encounter any traction issues. What we did encounter was the stock brakes failure to hold boost at the line. TBs launch best with about 4-5 psi of boost, but we were forced to struggle on with no-boost launches and ran a string of 13.6 and 13.7s, all at 100 mph. All in all, we picked up over 6-tenths and 6 mph, but we were hoping for low 13's considering the massive torque gains. Our best ET turned out to be a 13.63 at 100.55. In the foreseeable future we need to install a higher stall torque converter that will make it easier for us to launch at 4 psi and get the V-6 into full boost much quicker to get the ETs to drop.

In the meantime, (for this installment) our plan was to test a high-flow exhaust system. We've been hearing good reviews about Pypes Performance Exhaust products. For our projected power level we felt a high-flow 2.5-inch GNX-type exhaust would be most beneficial over the stock 2.25-inch exhaust. Besides, the original rusty exhaust, with its restrictive transverse muffler, was in dire need of replacement. We ordered a stock-style 2.5-inch exhaust, since a 3-inch may have taken away from the stock turbo's ability to spool and it is much quieter. After all, who needs that dreaded interior noise drone?

The Pypes 2.5-inch exhaust kit (PN SGG50R) is made from 16-gauge, 409 stainless and was shipped promptly. We opted to upgrade from the standard Street Pro to the quieter and higher-flowing Race Pro mufflers. I brought the exhaust kit over to Tim Cairone's place (Shore Wheels in Tuckerton, NJ) for an easy install using his lift (I've done enough track-side exhaust swaps). Pypes manufactures its exhaust products making home installation an easy slip-fit situation. Installation went along quite smooth and now the GN sounds great-not too loud or too quiet, just right. The stock exhaust, even though it had an old Flowmaster replacement transverse muffler installed back in the '90s, couldn't hold a candle to our GN's new tune.

Next, a call was made for another dyno-test appointment at Tune Time. With the new Pypes high-flow exhaust, the TR felt stronger than ever. We mixed in 5 gallons of race gas for added engine protection. Before the GN was back on the dyno we made sure the boost was at 19 psi. This way we could see exactly how much power the Pypes exhaust is worth. On Tune Time's Mustang dyno the turbo V-6 cranked out an unbelievable 440 lb-ft of torque and 278 hp, showing us gains of 35 lb-ft and 38 hp respectively. So far this was the first mod where we picked up more horsepower than torque! These power gains are what a TR can expect if ditching the stock exhaust (with the restrictive transverse muffler) for the same Pypes cat-back GNX-type exhaust system.

Due to our current issues with the stock turbo, an oil leak, and smoking at idle, we've been planning either a turbo rebuild or an upgrade to a stock-appearing turbo. Once we replace this tired, oil-leaking unit we'll be able to get some new track times. In the meantime you will have to settle for these impressive dyno results; stay tuned for the next installment.


Tune Time Performance
Lakewood, NJ 08701
Jose Motor Sports
Camden, NJ 08104
Pypes Performance Exhaust
Hatfield, PA 19440
Cotton's Performance
Agawam, MA 01001



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