Tuning Tips And Tricks - Turbo Buick Basics, Part 8

In the last episode (September, 2011) we promised we'd take our buddy Tim Cairone's '87 Buick GN back to Atco Dragway to strip-test its latest combination. Well, we made it back to Atco, but we went ill prepared and were nonetheless disappointed. (Note: never take a Turbo Buick to the track without knowing your car can't even do a 5-psi powerbrake burnout.) Quickly, we learned the importance of proper tuning and preparation before running a Turbo Buick at the strip. Unbeknown to us, the timing (ignition and injector pulse) was way off, causing terrible turbo lag. At the starting line while power-braking for our holeshot, we couldn't even build more than 3-psi of boost. Full boost (20-21psi) didn't develop until we were over 100-feet downtrack causing the GN to run disappointingly low to mid 12's (we were expecting to go mid 11's). We later found out the timing issue was because we didn't install the cam positioning sensor properly (it was 180-degrees out) when we swapped to the forged short-block in Part 7. Then, during a test ride, after setting the Cam Positioning Sensor (CPS) timing, another EGR leak (there was also an EGR leak in Part 7) came back to haunt us. This time the EGR block-off plate we installed blew-out its gasket causing a vacuum leak and turbo lag.

First for this installment we'll show the importance of having the right tool to properly set the timing of the CPS. Second, we'll attend to the EGR issue. Third, we ordered a new chip from Turbo Tweak for our latest combination (ported heads, roller cam, larger turbo, and intercooler neck). Fourth, we'll port/polish and blend the wastegate hole in the new 62mm Precision Turbo for quicker spool-up. Then it's back to Tune Time Performance to dial in all the upgrades we featured in part 6 and 7.

Our first tuning concern was to set the timing of the Cam Positioning Sensor (CPS) with the special tool we ordered from Caspers Electronics. The CPS actually controls the injector pulse timing. Once the timing of the CPS was set properly, a test drive confirmed better throttle response and turbo spool up. After our enthusiastic test drive, we noticed the EGR gasket was leaking. For the fix we pulled the EGR plate off and installed a new EGR valve and gasket. Once again the Buick was running better, but we were not done yet!

Next we installed the new custom chip from Turbo Tweak. We ordered it for a 50/50 race gas/pump gas mix. TT burned us a chip for our latest combo (62 mm turbo, ported heads, roller cam, larger intercooler neck) with additional timing and fuel mixture for using 100 to 105 octane fuel. This new chip will increase the ignition timing from the old chip's 19/17-degrees to 23/20-degrees at full boost. Also the old chip was set-up for 15-17psi while the new one is 20-22psi boost. Since it's programmable, we'll be able to add or reduce timing and change the fuel mixture (richer/leaner) for a safe air/fuel mixture. In the meantime, we'll keep a close eye on the A/F gauge. After swapping chips, a test-drive revealed a smoother, more responsive running engine, quicker spool-up along with a now perfect A/F (14.7 to 15.1) at idle. With the old chip the A/F at WOT (according to the GN's A/F gauge) was a risky 12.1 to 12.4 at 20-21 psi boost. Now we observed a safe A/F in the mid-10's at full boost and WOT. On the dyno we'll tune the full boost A/F to be in the safe zone of 11.5 to 11.9:1. Big kudos to Turbo Tweak after considering we still have only 42 lb injectors, up to this point the GN has never ran stronger!

The final mod, for icing on the cake, was to port the wastegate hole of the turbo. Both our friends at Precision Turbo and Jose Motorsports recommended we perform this modification. This mod is said to help quicken turbo spool up and help hold consistent/steady boost output. The port work needs to be done very carefully while not exceeding a 1/8-inch from the impression circle made from the wastegate puck (see captions 7 and 8). A test ride revealed that we ported the wastegate hole a hair too much bringing us once again back to terrible turbo lag. Thank goodness RJC Racing came to our rescue. They offer a larger diameter wastegate puck (1.65-inch diameter, stock is 1.1-inch) to solve our turbo-lag dilemmaùthis must have happened to other over-enthusiastic folks when they enlarged the wastegate hole!

Once the larger RJC Racing wastegate puck was installed, the Buick was back to running great! According to Tim it ran so strong, he adjusted the RJC Racing boost control valve, so there was only 18-psi boost (20-21psi previously). Note: both Precision Turbo and Turbo Tweak mentioned we could safely run up to 22-psi with a 50/50 race/pump gas mix. With 24-26 psi, 110-plus octane race gas is necessary. With a more miles on the fresh motor, and a few more tweaks we'll be ready to turn it up. For now we were happy to be running strong and ready to go back to the dyno for a safe and conservative tune.

An appointment was made at our favorite local dyno tuning shop, Tune Time Performance in Toms River, New Jersey. Matt Hauffe has been handling driving and tuning duties to the Turbo Regal right from the beginning of Turbo Buick Basics. On our first pass we were pleased to learn the A/F was at a near perfect 11.5 (according to the wideband O2 sensor on their Mustang dynamometer). The A/F gauge readings on the GN were off a point (10.5 A/F) due to a buildup of tetraethyl lead from the leaded race fuel we mix with 93-octane unleaded pump gas (future use of unleaded race gas or meth injection is needed). Spinning the dyno wheels we observed the turbo V-6 was making 30 lb-ft more torque with close to the same horsepower. That's impressive considering there is 2-3 psi less boost (18 psi now, 20-21 psi before)! That only showed us the importance of the right size turbo along with proper tuning. Also, Turbo Tweak knows its business when it comes to burning a PROM chip for anyone with a Turbo Regal.